Advanced Direct Exchange Geothermal Heating/Cooling System Design
A direct expansion/direct exchange (“DX”) geothermal heating/cooling system having a plurality of pin restrictors positioned in housing units at ground accessible locations. The pin restrictors are preferably located near the compressor unit and on the field side of the distributor. Refrigerant is substantially equally distributed by a distributor to substantially equally sized line sets in the DX system with multiple wells. The distributors are place in either horizontal or vertical inclinations with the pin restrictors situated on the field side of the distributor in each individual liquid refrigerant transport line. A cut-off ball valve is located within the liquid refrigerant transport line on each side of the respective pin restrictor housing units. A filter/dryer is place within the same liquid refrigerant transport line segment as the pin restrictor(s) with a refrigerant flow shut-off valve being situated on each side of the liquid line segment containing the filter/dryer and the distributor.
This is a non-provisional application claiming priority based upon co-pending U.S. Patent Application Ser. No. 60/806,739 filed Jul. 7, 2006 entitled “Advanced Direct Exchange Geothermal Heating/Cooling System Design.”
I, B. Ryland Wiggs, of Franklin, Tenn., have invented a new and useful “Advanced Direct Exchange Geothermal Heating/Cooling System Design”.
A portion of the disclosure of this patent document contains material that is subject to copyright. The copyright owner has no objection to the authorized facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
All patents and publications discussed herein are hereby incorporated by reference in their entirety.
BACKGROUND OF THE INVENTIONThe present invention relates to a geothermal direct exchange (“DX”) heating/cooling system, which is also commonly referred to as a “direct expansion” heating/cooling system, comprising various design improvements.
Geothermal ground source/water source heat exchange systems typically utilize fluid-filled closed loops of tubing buried in the ground, or submerged in a body of water, so as to either absorb heat from, or to reject heat into, the naturally occurring geothermal mass and/or water surrounding the buried or submerged fluid transport tubing. The tubing loop is extended to the surface and is then used to circulate one of the naturally warmed and naturally cooled fluid to an interior air heat exchange means.
Common and older design geothermal water-source heating/cooling systems typically circulate, via a water pump, a fluid comprised of water, or water with anti-freeze, in plastic (typically polyethylene) underground geothermal tubing so as to transfer geothermal heat to or from the ground in a first heat exchange step. Via a second heat exchange step, a refrigerant heat pump system is utilized to transfer heat to or from the water. Finally, via a third heat exchange step, an interior air handler (comprised of finned tubing and a fan) is utilized to transfer heat to or from the refrigerant to heat or cool interior air space.
Newer design geothermal DX heat exchange systems, where the refrigerant fluid transport lines are placed directly in the sub-surface ground and/or water, typically circulate a refrigerant fluid, such as R-22 or the like, in sub-surface refrigerant lines, typically comprised of copper tubing, to transfer geothermal heat to or from the sub-surface elements via a first heat exchange step. DX systems only require a second heat exchange step to transfer heat to or from the interior air space, typically by means of an interior air handler. Consequently, DX systems are generally more efficient than water-source systems because less heat exchange steps are required and because no water pump energy expenditure is necessary. Further, since copper is a better heat conductor than most plastics, and since the refrigerant fluid circulating within the copper tubing of a DX system generally has a greater temperature differential with the surrounding ground than the water circulating within the plastic tubing of a water-source system, generally, less excavation and drilling is required, and installation costs are lower, with a DX system than with a water-source system.
While most in-ground/in-water DX heat exchange designs are feasible, various improvements have been developed intended to enhance overall system operational efficiencies. Several such design improvements, particularly in direct expansion/direct exchange geothermal heat pump systems, are taught in U.S. Pat. No. 5,623,986 to Wiggs; in U.S. Pat. No. 5,816,314 to Wiggs, et al.; in U.S. Pat. No. 5,946,928 to Wiggs; and in U.S. Pat. No. 6,615,601 B1 to Wiggs, the disclosures of which are incorporated herein by reference. Such disclosures encompass both horizontally and vertically oriented sub-surface heat geothermal heat exchange means, utilizing historically conventional refrigerants, such as R-22, as well as utilizing a newer design of refrigerant identified as R-410A. R-410A is an HFC azeotropic mixture of HFC-32 and HFC-125.
DX heating/cooling systems have several primary objectives. The first is to provide the greatest possible operational efficiencies. This directly translates into providing the lowest possible heating/cooling operational costs, as well as other advantages, such as, for example, materially assisting in reducing peaking concerns for utility companies. The second is to operate in an environmentally safe manner via the utilization of environmentally safe components and fluids.
Historically, DX heating/cooling systems, even though more efficient than other conventional heating/cooling systems, have experienced practical limitations created by the relatively large surface land areas necessary to accommodate the sub-surface heat exchange tubing. For example, with R-22 systems, a typical land area of 500 square feet per ton of system design capacity was required in first generation designs to accommodate a shallow (within 10 feet of the surface) matrix of multiple, distributed, copper heat exchange tubes, or about one to two 50 foot to 100 foot (maximum) depth wells/boreholes per ton of system design capacity, spaced at least about 20 feet apart, were required. Such requisite surface areas effectively precluded system applications in many commercial and/or high density residential applications. An improvement over such predecessor designs was taught by Wiggs via the utilization of an R-410A refrigerant that operated at about a 40% higher pressure than R-22 systems, and that were able to efficiently operate at DWDX system depths, of about 300 to 350 feet per well/borehole.
While a number of former DX system designs work, as a primary objective is to increase the efficiency and reliability of DX system designs, particularly in light of rapidly accelerating energy costs, extensive testing has demonstrated a number of design improvements that will enhance the efficiency and reliability of older DX system designs.
It is an object of the subject inventions to improve upon earlier and former DX system technologies, so as to provide ultra-efficient, environmentally safe, DX system designs. The present inventions provide a solution to these preferable objectives, as hereinafter more fully described.
SUMMARY OF THE INVENTIONThe subject inventions primarily relate to DX system advantages when installed with DWDX system vertically oriented sub-surface geothermal heat exchange means, although various advantages are also present in near-surface (100 feet deep or less) DX system applications, particularly such as involving a trench system design, a pit system design, or any combination of the above. Thus, it is an object of the present inventions to further enhance and improve the efficiency and practical applicability of predecessor direct expansion/direct exchange (“DX”) geothermal heating/cooling systems. This is accomplished by means of providing the following:
1. Providing pin restrictors, in housing units, at an accessible location, typically above-ground, for a DX system operating in the heating mode, where the pin restrictors are preferably located near the compressor unit, but on the field side of any distributor. Typical predecessor DX system designs utilized self-adjusting expansion valves in the heating mode, or utilized manually adjusted heating valves. The problem with self-adjusting heating valves in a DX system in the heating mode is that the refrigerant has to travel so far in the sub-surface environment, the automatic valve is constantly “hunting” for an optimum setting, resulting in rather continuous and inefficient swings in set points. The problem with a manually adjusted valve is that a precise optimum setting is a matter of luck, rather than design. Earlier pin restrictor designs by Wiggs taught the placement of the heating mode pin restrictors at or near the bottom of a deep well DX system design, or at the distal end of a mostly horizontal sub-surface refrigerant transport tubing design. While this design was a major improvement over predecessor technology, providing uniform refrigerant flow through systems with multiple combined wells/line sets, the ability to service or change the pin restrictor was cumbersome. Therefore, the placement of the pins in an above-ground location, in a manner so as to still insure uniform refrigerant flow through systems with multiple combined wells/line sets would be preferable. This is accomplished by means of equally distributing refrigerant flow through a distributor to equally sized line sets in a system with multiple wells, all while placing the distributors in at least one of an exactly horizontal and a vertical inclination, with the pin restrictors situated on the field side of the distributor in each individual liquid refrigerant transport line going to the subsurface geothermal heat transfer field below ground/water level. An individual liquid refrigerant transport line must be distributed to each pin restrictor. Further, it is advantageous to insure the pin restrictors are easily serviced by means of a cut-off ball valve located within the liquid refrigerant transport line on each side of respective pin restrictor housing units. Placing pin restrictors on each individual distributed liquid refrigerant transport line helps to insure an equal refrigerant flow rate and pressure into each respective geothermal heat exchange loop, and also provides a means to check for any restrictions in individual distributed heat exchange loops.
Further, the use of a filter/dryer for refrigerant is a useful and common piece of equipment used in DX systems, as is well understood by those skilled in the art. However, historically in the DX field, filter/dryers have been placed within the compressor box itself. Thus, when the filter/dryer needs to be changed, the historical and common practice in the DX HVAC field has been to open the compressor box, re-claim all refrigerant the within the box, change the filter/dryer, and then replace the refrigerant that had been reclaimed. Typically, many compressor boxes in the DX field even have no isolation valves so as to limit refrigerant reclaiming to the refrigerant within the box. Thus, a design improvement, so as to materially facilitate servicing and reduce servicing time/expense, would be to place the filter/dryer within the same liquid refrigerant transport line segment as the pin restrictor(s), with a refrigerant flow shut-off valve being situated on each side of the liquid line segment containing the filter/dryer and the distributor (if there are more than one sub-surface liquid refrigerant transport lines).
Since such a liquid line segment will be relatively heavy. Thus, so as not to incur a bent or crimped liquid refrigerant transport line via gravity over a period of time, it would be preferable for the field side cut-off valves to be situated on at least one of the ground and a solid support so as to carry the weight of the subject liquid line segment.
Restrictions in at least one of a distributed geothermal heat exchange loop will be evidenced by a decreased refrigerant flow rate, by a higher temperature in the cooling mode and/or by a lower temperature in the heating mode. The cut-off valves on the other geothermal heat exchange loop(s) can be slightly engaged, a little at a time, until the loop temperatures of an operational system all evenly match. When the temperatures all match, the amount of restriction to the good geothermal heat exchange loop, via the degree of cut-off valve engagement, can be measured to determine the amount of restriction in the bad, restricted, heat exchange loop. If all multiple loops combined, with equal restrictions in each, provide the minimum necessary refrigerant flow rate for the particular DX system, the faulty restricted loop will not have to be replaced.
2. The sizing of the heating mode pin restrictors for a DX system operating in the heating mode, with R-410A refrigerant, must be within the following size parameters, plus no more than 5%, and less no more than 17% of the area of each below identified pin diameter size in inches. If the pin size is increased by more than 5%, the sensible interior heat produced is lowered and the operational efficiency levels decrease. If the pin size is decreased by more than 17%, when one switches from the cooling mode to the heating mode at the end of a cooling season, the head pressure of the refrigerant may be excessively high, so as to shut the system off via its internal high pressure cut-off switch.
((or formula) (Calculation is 15% to 30% less than conventional R-22 chart sizes, with 15% being preferable to permit cooling to heating switch-over without too high of a head pressure.) (Plus, one must add additional refrigerant to offset the increased superheat caused by the smaller pin size, or premature compressor failure will result . . . this is taken into account in charging formula.))
In the alternative, the following formula may be used to determine the correct heating mode pin size:
For a 13,400 BTU through a 44,000 BTU compressor size (not air handler size and not system design size, but the actual size of the compressor in the compressor unit/box), multiply the compressor size in thousandths by 0.000065. Match the resulting number, which will be the area of the orifice, to the closest pin size diameter. For example, if the system has a 21,000 BTU compressor, multiple 21 by 0.000065, which equals a 0.001365 area, which is nearest to a 0.042 pin restrictor size diameter.
For a 45,000 BTU through a 60,000 BTU compressor size (not air handler size and not system design size, but the actual size of the compressor in the compressor unit/box), multiply the compressor size in thousandths by 0.000058. Match the resulting number, which will be the area of the orifice, to the closest pin size diameter. For example, if the system has a 54,000 BTU compressor, multiple 54 by 0.000058, which equals a 0.003132 area, which is nearest to a 0.063 pin restrictor size diameter.
Regarding the above formula, when one wishes to use two, three, or more pin restrictors for one system, in a situation where the heat exchange tubing is distributed into two or more geothermal heat exchange sub-surface fields, the final calculated area needs to be divided by 2, 3, etc., and then matched to the nearest pin size used.
3. Although in a typically cooling to heating season period, the ground, which has been absorbing rejected heat all summer, will typically cool enough to permit instant DX system heating mode operation with only a properly sized heating mode pin restrictor, if the seasonal change is extremely abrupt and fast, a pressure regulated heating mode refrigerant by-pass vale within a heating mode by-pass line around the heating mode pin restrictor may be necessary so as to permit instant system heating mode operation without the system tripping off via its safety high pressure cut off switch. To accomplish this optional heating mode protective means, one should preferably add a heating mode by-pass pressure regulated valve, also referred to as an automatic expansion valve (“AXV”), so as to assist transition from the cooling mode to the heating mode so that the valve opens to an interior diameter of at least the size of the actual BTU size, in thousandths, of the compressor in the compressor unit/box multiplied by 0.00008, with no less than multiplied by 0.00006, and with preferably no more than multiplied by 0.00016, to be opened when the refrigerant head pressure is 375 psi (plus or minus 5 psi) or greater, and to be closed when the refrigerant head pressure is below 375 psi (plus or minus 5 psi). Match the resulting number, which will be the area of the orifice, to the closest pin size diameter if to be measured in pin restrictor sizing. The higher the refrigerant pressure, the greater the opening in the valve. The valve should begin to open at an 0.00008, and should be no larger than 0.00016. When the DX system refrigerant head pressure in the heating mode is less than 375 psi, the valve will be fully closed, thereby forcing the refrigerant flow through the properly designed pin restrictor orifice opening only.
4. The cooling mode TXV by-pass pin restrictor size must be within the following size parameters:
In the alternative, the following formula may be used to determine the correct TXV by-pass pin size:
For a 21,000 BTU through a 32,000 BTU compressor size (not air handler size and not system design size, but the actual size of the compressor in the compressor unit/box), multiply the compressor size in thousandths by 0.000095. Match the resulting number, which will be the area of the orifice, to the closest pin size diameter. For example, if the system has a 21,000 BTU compressor, multiple 21 by 0.000095, which equals a 0.001995 area, which is nearest to a 0.050 pin restrictor size diameter.
For a 33,000 BTU compressor size (not air handler size and not system design size, but the actual size of the compressor in the compressor unit/box), multiply the compressor size in thousandths by 0.000091. Match the resulting number, which will be the area of the orifice, to the closest pin size diameter. For example, if the system has a 33,000 BTU compressor, multiple 33 by 0.000091, which equals a 0.0030 area, which is nearest to a 0.062 pin restrictor size diameter.
For a 34,000 BTU through a 55,000 BTU compressor size (not air handler size and not system design size, but the actual size of the compressor in the compressor unit/box), multiply the compressor size in thousandths by 0.000088. Match the resulting number, which will be the area of the orifice, to the closest pin size diameter. For example, if the system has a 48,000 BTU compressor, multiple 48 by 0.000088, which equals a 0.004224 area, which is nearest to a 0.073 pin restrictor size diameter.
For a 56,000 BTU through a 83,000 BTU compressor size (not air handler size and not system design size, but the actual size of the compressor in the compressor unit/box), multiply the compressor size in thousandths by 0.00009. Match the resulting number, which will be the area of the orifice, to the closest pin size diameter. For example, if the system has a 60,000 BTU compressor, multiple 60 by 0.00009, which equals a 0.0054 area, which is nearest to a 0.083 pin restrictor size diameter.
Regarding the above formulas, when one wishes to use two, three, or more pin restrictors for one system, in a situation where the heat exchange tubing is distributed into two or more air handlers, for example, the final calculated area needs to be divided by 2, 3, etc., and then matched to the nearest pin size used.
5. Add a cooling mode TXV by-pass pressure regulated valve, also referred to as an automatic expansion valve (“AXV”), so as to assist transition from the heating mode to the cooling mode in a DX system.
Add a cooling mode by-pass pressure regulated valve, also referred to as an automatic expansion valve (“AXV”), so as to assist transition from the heating mode to the cooling mode so that the valve opens to an interior diameter of at least the size of the actual BTU size, in thousandths, of the compressor in the compressor unit/box multiplied by 0.00009, with no less than multiplied by 0.00009, and with preferably no more than multiplied by 0.00018, to be opened when the refrigerant suction pressure is 85 psi (plus or minus 5 psi) or less, and to be closed when the refrigerant suction pressure is above 85 psi (plus or minus 5 psi). Match the resulting number, which will be the area of the orifice, to the closest pin size diameter if to be measured in pin restrictor sizing. The lower the refrigerant pressure, the greater the opening in the valve.
Alternately, although not as precise as individually tailored by-pass valves for each respective compressor size, a one size fits all valve opening to the actual BTU size, in thousandths, of a five ton compressor in the compressor unit/box multiplied by 0.00009, with no less than multiplied by 0.00009, and with preferably no more than multiplied by 0.00018, to be opened when the refrigerant suction pressure is 85 psi (plus or minus 5 psi) or less, and to be closed when the refrigerant suction pressure is above 85 psi (plus or minus 5 psi), may be used for systems with 1 through 5 ton compressor units.
The AXV should be an external equalized valve, with a capillary tube extended from the valve to the low pressure vapor line exiting the air handler. The valve should preferably be an adjustable type valve that can be set to shut off at any pressure between 40 psi and 100 psi., with an 85 psi shut off point being preferable for a DX system application.
6. For maximum cooling capacity and humidity removal, the receiver size must be sized at 1 pound for every 40 feet of ⅜ inch O.D. liquid line depth within a DWDX system design, or the equivalent thereof when other line set sizes are utilized, exclusive of the trenched line(s) to/from the well(s) and the compressor unit.
For maximum cooling operational efficiencies and minimum vertical well refrigerant pressure drop, the receiver size must be sized at 1 pound for every 50 feet of ⅜ inch O.D. liquid line depth within a DWDX system design, or the equivalent thereof when other line set sizes are utilized, exclusive of the trenched line(s) to/from the well(s) and the compressor unit, and exclusive of any other DX system refrigerant containment components.
7. Differing air handler manufacturers utilize differing finned tubing lengths per ton of size design capacity. However, most air handler manufacturers utilize finned tubing with 12 to 14 fins per inch length. Since differing manufacturers utilize differing lengths of tubing per ton of design capacity, it is inefficient to prescribe a certain tonnage air handler to be used with a particular DX system BTU compressor size. Further, to optimize DX system efficiencies, testing has shown it is impractical to match a 3 ton compressor with a 3 ton air handler, as most all predecessor conventional system designs call for. Testing has shown that in order to optimize the efficiency of a DX system design, the air handler must be sized to 120% of the maximum system design load and must have 60 feet per ton, plus or minus 5 feet, of finned 3/8 inch O.D. interior heat exchange tubing. 55 to 60 feet is preferable in heating mode. 60 to 65 feet is preferable in cooling mode.
8. The DX system charging formula, using R-410A refrigerant (all known predecessor DX systems sold operate on an R-22, or similar, refrigerant with significantly lower operating pressures than R-410A) for a DWDX system, with a preferred sub-surface ⅜ inch O.D. liquid refrigerant grade transport line in the well/borehole, with a 0.032 inch wall thickness, and a sub-surface ¾ inch O.D., or larger, vapor refrigerant grade geothermal heat exchange transport line in the well/borehole, is calculated by adding the sum of the following:
A. Total depth of the ⅜ inch O.D. liquid line in well times 0.0375 pounds
B. 50% of total length of finned ⅜ inch O.D. tubing in air handler multiplied by 0.0375 pounds.
C. Compressor unit/box content of liquid refrigerant. For an ETA system, for a 1.5 to a 4 ton system, add 1.5 pounds. For a 4.1 to a 5 ton system, add 2 pounds.
D. Add the amount of liquid refrigerant contained in the system's filter/dryer (for example, a Parker Bi-Directional R-410A Heat Pump Filter/Dryer Model BF164-XF holds about 0.761875 pounds), exclusive of the filter/dryer in the compressor box, which has already been taken into account in the compressor unit/box content.
E. Add the amount of liquid refrigerant in all liquid line ball cut-off valves (typically about 0.05 pounds), exclusive of the ball cut-off valves in the compressor box, which have already been taken into account in the compressor unit/box content.
F. Measure the total liquid transport line length between the top of the well/borehole and the compressor unit/box and multiply by the full liquid weight content of the line in pounds. For example, multiply by 0.0375 pounds if it is a ⅜ inch O.D. line, but multiply by 0.06875 if it is a ½ inch O.D line.
G. Measure the total liquid transport line length between the air handler and the compressor unit/box and multiply by the full liquid weight content of the line in pounds. For example, multiply by 0.0375 pounds if it is a ⅜ inch O.D. line, but multiply by 0.06875 if it is a ½ inch O.D line.
H. For a cooling mode charge, add an additional 1 pound of refrigerant for every 40 feet of ⅜ inch O.D. refrigerant grade liquid line in the well for maximum system operational capacity and humidity removal. If humidity removal is not a concern, add an additional 1 pound of refrigerant for every 50 feet of ⅜ inch O.D. refrigerant grade liquid line in the well for maximum efficiency.
I. If the system is designed to operate in a reverse-cycle mode (heating and cooling), the system must have a liquid line receiver that holds the preferred charge differential between the heating mode and the cooling mode. Additionally, the receiver will have some constant amount of liquid content in its bottom, regardless of the system operational mode, which constant amount of refrigerant, in pounds, must be added. For example, a typically well designed receiver usually always holds 0.75 pounds, regardless of whether operating in the heating or the cooling mode.
Prior DX system designs with receivers either failed to specify a receiver with only one refrigerant entrance and exit and/or failed to specify the amount of refrigerant the receiver was to hold and/or referenced a receiver percentage content equal to some uniform percentage (such as 40% for example) of the total system charge, typically all without defining how to determine the exact system charge. Consequently, prior DX receiver designs have been generally useless. Testing has shown that the receiver content must be as hereinabove described, with only one refrigerant entrance and exit, for a reverse-cycle DX system to operate at one of its optimum capacity and efficiency. No known person has heretofore discovered or taught the receiver capacity in a DX system is dependent upon well/borehole depth with specified and certain liquid refrigerant transport line sizes.
J. If the system is designed to operate in the heating mode with a heating mode pin expansion device installed, the weight, in pounds, of the liquid content of the pin restrictor housing design must be added to the total.
The total of the appropriate above sums will equal the correct system charge.
To determine the optimum charge in DX systems utilizing other than ⅜ inch O.D. liquid refrigerant transport lines and ¾ inch O.D. vapor refrigerant transport lines, the charge should preferably be determined by the above formula, except the equivalent refrigerant content of the actual interior volume of the liquid refrigerant transport line used must be matched to the interior volume of a ⅜ O.D. liquid refrigerant transport line as per the above formula. For example, if multiple liquid refrigerant transport lines of a smaller interior diameter were utilized than that of a ⅜ inch O.D. refrigerant grade copper tube, then the content of all multiple smaller lines must match that of the content of a system designed with at least one of one and multiple ⅜ inch O.D. refrigerant grade copper tube(s). As another example, if a larger liquid refrigerant transport line was used than that of a ⅜ inch O.D. refrigerant grade copper tube, then the interior content of the larger tube must match that of the content of a system designed with at least one of one and multiple ⅜ inch O.D. refrigerant grade copper tube(s).
9. Place a rubber mat over the top of all DX system geothermal heat exchange wells in lightening prone areas. Additionally, in areas prone to lightening strikes, all copper tubing within trenches between wells and compressor units should preferably be insulated with plastic or rubber material that is not electrically conductive, such as expanded foam polyethylene and/or neoprene. This will assist in mitigating lightening strikes in lightening prone areas, such as Florida.
Copper tubing well installation spools, with pre-assembled line sets for DX system field loop installations, should preferably have at least a 24 inch wide holding tube diameter, with both insulated and un-insulated refrigerant transport lines on the same holding spool, with spiraled fiber tape to keep the lines together. The holding spool should preferably have sides extending past the outer layer of the refrigerant transport lines, but with a four foot, or less, diameter so as to facilitate shipping on a four foot wide pallet. Prior to assembly, the line set, with a cementitious grout-filled (preferably Grout 111) “Torpedo” unit surrounding the liquid refrigerant transport line U bend and the liquid refrigerant transport line coupling to the vapor refrigerant transport line at the bottom, should be evacuated of air with a vacuum pump (typically an electrically operated pump) to at least a 250 micron vacuum, and then charged with a dry nitrogen holding charge of 50 pounds, or the like, for shipment and installation. Pulling the vacuum and charging with dry nitrogen is accomplished via sealing one of the liquid and vapor refrigerant transport lines shut and installing a schraeder valve on the other for gauge set attachment and hook up to the vacuum pump and then to the pressurized bottle of dry nitrogen, as is well understood by those skilled in the art.
The 250 micron vacuum will insure there are no leaks, and the 50 pound holding charge will insure no leaks have occurred during either shipment or installation. Both pulling the vacuum and inserting the holding charge of dry nitrogen are effected by means of capping one of the ends of the liquid refrigerant transport line and vapor refrigerant transport lines, and placing a schraeder valve (a schraeder valve is well understood by those skilled in the art) in the other for refrigeration gauge set attachment (refrigeration gauges are well understood by those skilled in the art). This procedure comprises a significant time saving and efficiency improvement over the historical and traditional method of installing sub-surface heat exchange tubing in a DX system, where the tubing is installed, sealed, and pressure tested prior to pulling a vacuum and charging, which is more time consuming and is not as trustworthy as initially pulling a vacuum. Pulling a vacuum cannot be done to 250 microns in a DX system if there is a leak, whereas a pressure test could take hours or days to reveal a very slight leak. A Torpedo unit is comprised of a tube with a rounded nose, which tube contains refrigerant transport tubing, the lower liquid line U bend, and a cementitious grout fill material, preferably comprised of Grout 111, which Grout 111 is shrink and crack resistant, with a very high 1.4 BTUs/Ft.Hr. Degrees F heat transfer rate. The rounded nose on the Torpedo unit prevents hang-ups on rugged well/borehole sides and/or ledges as the copper refrigerant transport tubing line set is lowered into the well/borehole.
The pre-assembled line set, comprised of an insulated smaller diameter liquid refrigerant transport line and an un-insulated larger diameter vapor refrigerant transport line, should preferably be surrounded by a spiraled fiber tape, or the like, so as to keep the refrigerant transport lines together as they are lowered into the well/borehole. The tape 70 must be spiraled at least once every eight to twelve inches to be effective.
11. A near-surface, but sub-surface, DX trench geothermal heat exchange system should preferably be comprised of equal lengths of a smaller diameter un-insulated refrigerant transport tubing and of a larger diameter un-insulated refrigerant transport tubing, and should preferably be installed with at least 100 feet of refrigerant transport tubing per ton of the maximum heating/cooling BTU load design, as per ACCA Manuel J or the like, where 12,000 BTUs equal one ton of heating/cooling capacity. However, 120 feet per ton is a preferred length to assist in insuring optimum system operational efficiencies.
In such a DX trench system, one liquid refrigerant transport line would be coupled to one vapor refrigerant transport line at the distal end of the sub-surface heat exchange loop, with the liquid line making at least a 6 inch vertically and downwardly oriented U bend prior to coupling to the vapor line at the at least 6 inch higher elevation. The U bend should be at the lowest point of the entire heat exchange loop, and the vapor line must be one of at least horizontally oriented and downwardly sloped (downwardly sloped being preferred) to the U bend. Preferably, such heat exchange loops would not exceed 360 feet in length per loop.
In such a DX trench system, the liquid refrigerant transport line would preferably be comprised of one 120 foot long ⅜ inch O.D. refrigerant grade copper tube, or the like, per ton of system design capacity, with a maximum 360 foot distance per liquid line segment in each respective loop.
In such a DX trench system, the vapor refrigerant transport line would preferably be comprised of one 120 foot long ¾ inch O.D. refrigerant grade copper tube, or the like, per ton of system design capacity, with a maximum 360 foot distance per vapor line segment in each respective loop.
In such a DX trench system, neither the vapor refrigerant transport line used for subsurface heat exchange, nor the liquid refrigerant transport line used for subsurface heat exchange, would be insulated, and the respective vapor line and liquid line, except for being coupled together at the distal end of the loop, would be separated by at least 20 feet, with a 30 foot separation being preferable where land area permits. When the vapor line and liquid line near one another for connection to the DX system compressor unit, each line should preferably be fully insulated, with a closed cell insulation (such as expanded polyethylene and/or neoprene, or the like) when they are at least within 20 feet of one another.
In such a near-surface trench system application, when the design capacity calls for more than one 360 foot long loop, multiple sub-surface geothermal heat exchange loops, comprised of larger diameter vapor lines coupled at their respective distal ends to respective smaller diameter liquid lines would preferably be joined together by means of a vapor line distributor and a liquid line distributor for refrigerant transportation to the compressor unit. Here, as in a single loop application, insulation would preferably surround all sub-surface tubing within twenty feet of one another.
12. A DX system may be utilized where the sub-surface heat exchange tubing is installed under water. When in moving water, such as at least one of a stream, a creek, a river, and a tidal area, and the like, a DX system with refrigerant transport heat exchange tubing in the moving water needs only forty feet per ton to operate at design system tonnage capacity (as per ACCA Manuel J or the like) with sixty feet per ton being preferred with a design safety margin. The heat exchange tubing, should be exposed to the water via at least one of an extended line, a looped, coiled, and largely spread apart line, a looped, coiled, and modestly spread apart line, a series of U bends, and the like, always with the heat exchange line at a downwardly sloped elevation to a connecting liquid line, by means of a coupling, at the bottom/distal end. The refrigerant transport lines/tubing would typically be insulated, after exiting the water, on the way to the compressor unit.
The heat exchange tubing should preferably be comprised of ¾ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with up to a 30,000 BTU compressor. The heat exchange tubing should preferably be comprised of ⅞ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with a 31,000 BTU compressor up to an 83,000 BTU compressor. When smaller heat exchange tubing is used, the interior diameter of the smaller lines should preferably approximately equal the interior diameter of the respective ¾ inch O.D. and ⅞ inch O.D. lines as described in this paragraph with the varying compressor sizes.
The connecting liquid line, which will travel from the distal and lowest end of the larger heat exchange tubing back to the system's compressor unit, should be comprised of ⅜ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with up to a 30,000 BTU compressor. The connecting liquid line, which will travel from the distal and lowest end of the larger heat exchange tubing back to the system's compressor unit, should be comprised of ½ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with a 31,000 BTU compressor up to an 83,000 BTU compressor. When smaller liquid line refrigerant transport tubing is used, the interior diameter of the smaller lines should preferably approximately equal the interior diameter of the respective ⅜ inch O.D. and ½ inch O.D. lines as described in this paragraph with the varying compressor sizes.
When in salt water and/or in water that is at least one of corrosive and abrasive to copper or other refrigerant transport tubing, the refrigerant transport tubing must be situated within a protective encasement, such as at least one of Grout 111, titanium, polyethylene, and a non-corrosive fluid filled pipe, and the like.
Alternately, the heat exchange tubing could be installed with finned tubing within a containment box made of a resistant material, such as at least one of titanium, Grout 111, polyethylene, and the like, to prevent micro-organism damage. Micro-organisms in seawater eat stainless steel. Preferably, such a containment box would be filled with a non-corrosive fluid, such as pure water or the like, and would have an expanded top and bottom to facilitate the collection and transfer of heat to the surrounding water (the warmest water would naturally rise to the top of the containment box and the coolest water would naturally fall to the bottom of the containment box in both the cooling mode and in the heating mode, all while the heat transporting refrigerant would be traveling from the top to the bottom in the cooling mode, and from the bottom to the top in the heating mode, thereby providing maximum heat transfer ability and efficiency.
While submerged heat exchange tubing may be placed within a protective polyethylene covering, preferably one of a protective titanium or Grout 111 covering would be utilized, as polyethylene has a relatively poor heat transfer rate of only 0.225 BTUs/Ft. Hr. degrees F.
13. A DX system may be utilized where the sub-surface heat exchange tubing is installed under water. When in moving water, such as at least one of a stream, a creek, a river, and a tidal area, or the like, a DX system with refrigerant transport heat exchange tubing in moving water needs only 40 feet per ton to operate at design system tonnage capacity, with 60 feet per ton being preferred with a design safety margin. The heat exchange tubing should be exposed to the water via at least one of an extended line, a looped line, a coiled line, and a spiraled, spread apart, and a looped line, always with the heat exchange line at a downwardly sloped elevation to a connecting liquid line at the bottom/distal end.
The heat exchange tubing should preferably be comprised of ¾ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with up to a 30,000 BTU compressor. The heat exchange tubing should preferably be comprised of ⅞ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with a 31,000 BTU compressor up to an 83,000 BTU compressor.
The connecting liquid line, which will travel from the distal and lowest end of the larger heat exchange tubing back to the system's compressor unit, should be comprised of ⅜ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with up to a 30,000 BTU compressor. The connecting liquid line, which will travel from the distal and lowest end of the larger heat exchange tubing back to the system's compressor unit, should be comprised of ½ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with a 31,000 BTU compressor up to an 83,000 BTU compressor.
Alternately, the heat exchange tubing could be installed with finned tubing within a containment box made of a corrosive-resistant material, such as at least one of titanium, Grout 111, polyethylene, and the like, to prevent damage from corrosive elements in the surrounding water and to prevent damage form micro-organisms living in the surrounding water. For example, some micro-organisms in seawater eat stainless steel. Therefore, the containment box would not be comprised of stainless steel in seawater. Preferably, such a containment box would be filled with a non-corrosive fluid, such as pure water or the like, and would have an expanded top portion and an expanded bottom potion to facilitate the collection and transfer of heat to the surrounding water (the warmest water would naturally rise to the top of the containment box and the coolest water would naturally fall to the bottom of the containment box in both the cooling mode and in the heating mode, all while the heat transporting refrigerant (within the finned refrigerant heat transport tubing within the containment box) would be traveling from the top portion of the finned tubing to the bottom portion of the finned tubing within the containment box in the cooling mode, and from the bottom portion of the finned tubing to the top portion of the finned tubing in the heating mode, thereby providing maximum heat transfer ability.
While submerged heat exchange tubing may be placed within a protective polyethylene containment box covering, preferably a containment box comprised of at least one of titanium and Grout 111 would be utilized, as polyethylene has a relatively poor heat transfer rate of only 0.225 BTUs/Ft. Hr. degrees F. However, protective piping, within which both the un-fined vapor refrigerant transport line and the liquid refrigerant transport line (traveling to and from the heat exchange tubing, with fins, within the containment box) may be placed, may be comprised of a polyethylene pipe, or the like, as heat transfer in the protective pipe around the refrigerant transport lines to/from the containment box is not of critical importance. Insulation would preferably be placed around all refrigerant transport tubing situated above the water.
When in salt water and/or in water that is at least one of corrosive and abrasive to copper or other refrigerant transport tubing, the refrigerant transport tubing must be situated within a protective encasement, such as at least one of Grout 111, titanium, polyethylene, and a non-corrosive fluid filled pipe, and the like. The protective encasement may be comprised of a shell. In the alternative, the protective encasement may be comprised of a solid material, such as Grout 111. Grout 111 is highly heat conductive (1.4 BTUs/Ft.Hr. Degree F.), weighs about 18.5 pounds per gallon, is virtually water impervious, and cures as a solid cementitious grout. A Grout 111 protective encasement will, therefore, act as both a good heat transfer agent and as an anchor for the larger diameter, downwardly sloping, heat exchange refrigerant vapor transport tubing, coupled at the lower distal end to the smaller diameter liquid refrigerant transport tubing. The portions of the refrigerant transport tubing above the water would be insulated.
14. How to offset water buoyancy in a DWDX system installation. When water is encountered, the buoyancy of the insulated liquid line in a DX system will require the addition of additional adding weight to offset the buoyancy. The weight needed to offset the buoyancy of a ⅜ inch O.D. liquid refrigerant transport line comprised of copper, surrounded by a closed cell type insulation with a ¾ inch thick wall, together with a ¾ inch O.D. un-insulated vapor refrigerant transport line, being dropped into a water-filled well/borehole, is about 1.5 pounds per foot of depth. Preferably steel, or the like, rods are used to add weight in a DX system. Weight may be added via taping/tying maximum five foot segments of maximum 2 inch diameter steel tubing (2 inch diameter weighs 10.68 pounds per foot . . . 1.75 inch diameter weighs 8.18 pounds per foot . . . 1.5 inch diameter weighs 6.01 pounds per foot) or smaller re-bar, or the like, to the line set as needed. Prior to attachment, the steel, or the like, tubing should preferably be wrapped in a protective wrapping, such as shrink wrap, tape, or the like, so as to protect the copper refrigerant transport tubing. The taping/tying of the maximum five foot long segment to the copper tubing should be done at the top and at the bottom of the segment only, so as to only place a minimum of heat transfer inhibiting tape, or the like, around the vapor refrigerant transport line used for geothermal heat transfer, and so as to permit some flexibility between the segments during installation into a well/borehole that may not be perfectly straight, so as to avoid jamming.
DX systems utilizing a ⅜ inch O.D., or less, liquid refrigerant line, and utilizing a ¾ inch O.D., or less vapor refrigerant line, typically require 4.5 inch to 6 inch diameter wells/boreholes, so as to provide enough room to easily insert the refrigerant transport lines, as well as the insulation surrounding the liquid line. A trimme tube is typically used to fill the annular space remaining within the well with a grout. The trimme tube is typically close to the same weight as water, and has an open lower distal end. Thus, the trimme tube fills with water as the rest of the closed loop refrigerant tubing and insulation are all inserted into the water filled well/borehole.
Add as many segments of steel tubing as necessary to offset the buoyancy. However, there must not be a vertical gap between the segments being added. If a vertical gap exists, which is historically permissible when plastic polyethylene pipe is used to transport water as a geothermal heat exchange fluid, the soft copper refrigerant transport tubing in a DX system application could be crimped/damaged during installation. Thus, in a DX system application, it is critical that the segments must be placed directly above one another, or slightly overlapped. A maximum of 5 foot long segments, although 4 foot long segments are preferred, should be used in a DX system application so as to avoid damaging the copper refrigerant transport tubing, and so as to avoid jamming during the insertion, when the well/borehole is not perfectly straight, as it seldom is. While longer segments may be used when water-filled polyethylene pipe is used as a heat transfer agent, since plastic pipe is typically more flexible than copper tubing, in a DX system application, segments should preferably be limited to a maximum of 5 foot lengths, with a maximum of 4 foot lengths being preferable.
For example, one will need to add 1.5 pounds of additional weight per foot of water-filled borehole to offset the buoyancy factor created by a ¾ inch wall closed cell insulation surrounding a ⅜ inch O.D. refrigerant transport liquid line. Thus, if 2 inch diameter steel tubing is used for a weight segment, one may need up to 8.5 segments that are 4 feet long each to offset the buoyancy in a 300 foot deep well. If 1.75 inch diameter steel tubing is used, one may need up to 11 segments that are 4 feet long each. If 1.5 inch diameter steel tubing is used, one may need up to 15 segments that are 4 feet long each. When water is encountered, one should drop the copper tubing as far as possible via its own weight, and then securely tape or shrink wrap on segments of steel tubing only as periodically necessary to continue the installation to its full well/borehole design depth, which depth is typically at least one hundred feet per ton of system design capacity.
An alternative method of offsetting buoyancy would be to drop the copper tubing as far as possible via its own weight, using a 1.25 inch (not a 1 inch) trimme tube and then slowly fill the grout line with Grout 111. As the Grout 111 fills the trimme tube, the weight of the grout in a 1.25 inch diameter trimme tube will push the copper tubing down, displacing the water as it goes. However, a plug must be placed in the bottom of the trimme tube that will be pulled out as the trimme tube is pulled up off the liquid and vapor refrigerant transport lines coupled together within the Torpedo at the lower distal end. The plug would be tied to the eyebolt extended from the cementitious grout filling the Torpedo unit, so that the plug secured to the eyebolt, which eyebolt is secured to the Torpedo, prevents the plug from traveling up as the trimme tube is pulled up and away from the bottom of the well during actual grouting. However, as filling a trimme tube with Grout 111 is very cumbersome, the typically preferred method of off-setting buoyancy would be to as previously described hereinabove. Consequently this described alternate method will not be shown herein in the drawings.
15. Plastic Coating for Copper Tubing.
Apply a relatively thin plastic, or the like, coating to the exterior surface of sub-surface copper, or the like, tubing used for DX heating/cooling systems to assist in preventing damage from corrosive soils/water/materials. Conventional plastic coatings for underground/underwater copper tubing is comprised of a thick, strong, coating, typically comprised of a 0.70 mm, or greater, thick coating, which is also designed to be strong enough to optionally decrease the wall thickness of the copper so as to lower copper costs. However, such a thick plastic coating inhibits heat transfer in a DX system design. Consequently, a thinner walled plastic coating would be preferable for a DX system underground/underwater/within materials (such as concrete or the like) application, with the coating being only 0.60 mm thick, or less. The plastic coating could be comprised of at least one of polyethylene, teflon, or the like. A 0.60 mm thick, or less plastic coating of polyethylene, for example, will typically not inhibit heat transfer by any more than an approximate 2% degradation, which is acceptable in a typical DX system design, as safety margins in excess of 2% are typically always incorporated into sub-surface heat exchange line length exposure distances.
For a more uniform heat absorption/rejection rate, along the entire length of a DX system sub-surface refrigerant transport heat exchange tube, with a plastic, or the like, coated exterior surface, it would be preferable to periodically decrease/increase the thickness of the coating. The thicker the coating, the slower the heat absorption/rejection rate, and the thinner the coating, the faster the heat absorption/rejection rate.
16. Double Direct Exchange System.
In the heating mode, any direct exchange geothermal heat acquisition tubing array may be used, preferably those taught by Wiggs. However, instead of transferring the heat acquired from the geothermal source to an air handler with an electric fan, or to a hydronic system with a water circulating pump, the heat would preferably be transferred directly to the air or water desired to be heated via convective heat transfer through a secondary heat exchange loop without the necessity of a secondary power draw, such as that occasioned by an electric fan or a water pump. The use of a sub-surface DX geothermal convective heat exchange system in conjunction with a secondary DX convective heat exchange system is hereby terms a “double direct exchange system”.
For a double direct exchange system used to heat concrete swimming pools, or the like, insulation should preferably be placed around the base and sides of the pool, and the secondary heat exchange loop should preferably be placed between the insulation and the water containment means, such as within the pool's concrete shell for example.
Preferably, so as to avoid any undue wear on the heat exchange tubing within the concrete shell of the pool, the heat exchange tubing would be coated with a plastic coating, thick enough to protect the tubing, but thin enough so as not to unduly inhibit heat transfer. In this regard, in order to enhance even heat exchange, decreasing thicknesses of the plastic coating would be utilized.
Preferably, whether coated with plastic or not, all U bends in the heat exchange tubing within the concrete would be insulated with a closed cell foam insulation, so as to provide room for expansion/contraction at the ends of the tubing where the tubing was not confined by concrete.
Alternatively, the heat exchange tubing would be placed on top of the insulation around the base and sides of the pool, and then covered with a thin plastic sheet. The concrete would then be poured on top of the plastic sheet, with the heat exchange tubing below, and with the insulation between the tubing and the ground. This would enable the
In such a secondary heat exchange loop, the heat exchange tubing (typically copper, or the like) may be comprised, for example, of an array of ¼ inch 100 foot long tubes that are one of horizontally inclined or sloped, with the slope extending in the direction of the refrigerant flow in the heating mode, so that the condensing refrigerant vapor, as it rejects its heat into the concrete/pool water, will drain to a lower elevation via gravity flow.
Such a system may be operated in a reverse cycle to chill, or cool, the water in a swimming pool. However, a reverse cycle operation of a double direct exchange system operating within the atmosphere of a structure would require a condensate drainage system to collect and remove the interior moisture condensing any exposed interior air heat exchange tubing.
In any double direct exchange system, if an array of ¼ inch O.D. refrigerant grade refrigerant transport tubing is utilized as the secondary heat exchange loop, one should preferably utilize an array of 6 such ¼ inch O.D. tubes per ton of maximum heating/cooling system design capacity, where 1 ton equals 12,000 BTUs.
Additionally, in a double direct exchange system, the secondary heat exchange loop could optionally be comprised of at least one, optionally finned, vapor refrigerant transport tube/line. The at least one, optionally finned, vapor refrigerant transport tube/line would be coupled to at least one liquid refrigerant transport line at the distal end of the secondary heat exchange loop, with the liquid line making at least a 1 inch, and preferably at least a 6 inch, vertically and downwardly oriented U bend prior to coupling to the vapor line at the higher elevation. The U bend should preferably be at the lowest point of the entire secondary heat exchange loop, and the vapor line must be one of at least horizontally oriented and downwardly sloped to the U bend.
Preferably, such heat exchange loops would be comprised of a ¾ inch O.D. copper refrigerant grade vapor refrigerant transport line, or the like, that is at least 100 feet long per ton of system design capacity, with at least 120 feet long per ton being preferred, when the vapor line is embedded in a heat conductive material such as cement, concrete, or the like.
Preferably, such heat exchange loops would be comprised of at least 5⅜ inch O.D. copper refrigerant grade vapor refrigerant transport lines, or the like, that are at least 100 feet long per ton of system design capacity, with at least 120 feet long per ton being preferred, when the vapor line consists of finned tubing solely exposed to the interior air. The vapor refrigerant transport line may optionally be distributed into multiple smaller lines that have a total of the same equivalent interior volume of refrigerant.
In a double direct exchange system, the secondary heat exchange loop tubing should be comprised of one ¾ inch O.D. refrigerant grade copper tubing, or the like, or of multiple smaller tubes with a total equivalent interior diameter, for use in conjunction with up to a 30,000 BTU compressor. The heat exchange tubing should be comprised of one ⅞ inch O.D. refrigerant grade copper tubing, or the like, or of multiple smaller tubes with a total equivalent interior diameter, for use in conjunction with a 31,000 BTU compressor up to an 83,000 BTU compressor.
In a double direct exchange system secondary heat exchange loop, the connecting liquid line portion of the secondary loop, which will travel from the distal end of the larger heat exchange tubing back through the system's compressor unit to the sub-surface geothermal evaporator, should be comprised of ⅜ inch O.D. refrigerant grade copper tubing, or the equivalent, for use in conjunction with up to a 30,000 BTU compressor. In a double direct exchange system secondary heat exchange loop, the connecting liquid line portion of the secondary loop, which will travel from the distal end of the larger heat exchange tubing back through the system's compressor unit to the sub-surface geothermal evaporator, should be comprised of ½ inch O.D. refrigerant grade copper tubing, or the equivalent, for use in conjunction with a 31,000 BTU compressor up to an 83,000 BTU compressor.
Lastly, in a double direct exchange system, in various applications, it would be preferable to at least one of distribute the heat in the heating mode and absorb/remove the heat in the cooling mode in a relatively uniform manner throughout the secondary portion of the double direct exchange system. This is accomplished by insulating the secondary portion of the heat transfer tubing with insulation of a decreasing insulation value. Thus, the first portion of the secondary heat exchange tubing would be insulated the heaviest, with the insulation thickness decreasing until the last portion of the tubing is reached, which would be un-insulated. For example, one may coat the first portion of the secondary heat exchange tubing with a 1.5 mm thick plastic polyethylene coating, with the thickness of the coating at least one of uniformly decreasing and periodically decreasing throughout the length of the secondary heat exchange tubing, with the final portion of the secondary tubing having no coating at all. Otherwise, a significant majority of the heat, via such secondary heat exchange tubing, will be transferred through the first portion of the secondary tubing, potentially overheating the first portion of the area to be heated and leaving the final portion of the area to be heated without adequate heat.
16. Swimming Pool Application
A double direct exchange system, as described above, would be an ideal application for heating a swimming pool, or the like.
In such an application, so as to avoid any undue wear on the heat exchange tubing within the concrete shell of the pool, the heat exchange tubing would be coated with a plastic coating, thick enough to protect the tubing, but thin enough so as not to unduly inhibit heat transfer. In this regard, in order to enhance even heat exchange, decreasing thicknesses of the plastic coating would be utilized.
Additionally, and/or alternately, in such an application, the sub-surface heat exchange tubing within the concrete shell of the pool would typically have U bends, which U bends should preferably be surrounded with a closed cell insulation. The insulation would prevent the concrete from restricting the copper tubing from expanding/contracting at the U bends, where the most stress would typically occur, as the tubing within the insulation would be free to expand/contract as necessary due to fluctuating temperatures, thereby preventing undue wear and tear on the tubing.
Alternately and/or additionally, in such an application, a thin plastic sheet may be placed under the floor and behind the concrete, or the like, walls of the pool. At least one of under and behind the thin plastic sheet would be the sub-surface heat exchange tubing, such as used in a DX heating/cooling system. At least one of under and behind the tubing would be a layer of insulation. The insulation helps insure the bulk of the heating/cooling effect of the DX system is transmitted to the water in the pool through the tubing, and is not lost into the surrounding ground. The plastic sheet, between the tubing and the concrete, prevents any restriction imposed upon the potential expansion/contraction of the tubing under varying temperature conditions, as well as prevents any exposure of the tubing to any potentially corrosive elements by means of the concrete, or the like, shell of the pool.
17. Ground Loop Test Procedures.
Once installed, a sub-surface ground loop in a DX system is typically good. However, if an unknown kink in a line has occurred during system, or if a pebble or some other debris has accidentally fallen into the line set during installation, such restriction could impair system operation. The only solution would be to replace the well once the system had been fully installed and operation had been found to be improper. In order to avoid such an expense in ascertaining a blocked line in a sub-surface line set, at least one of two tests may be conducted prior to grouting/covering the sub-surface line, so that if a restriction is found, the sub-surface line set may be easily removed and repaired prior to grouting and/or backfilling.
One test would be to charge the line with dry nitrogen and to time the release. For example, a restricted 300 foot deep well, with a ⅜ inch O.D. liquid line and a ¾ inch O.D. vapor line, with a 160 dry nitrogen charge, would experience an approximate 4 psi higher charge level at the end of a 30 second pressure release than would a clear and unrestricted line set in the same well.
Another similar pressure release test would be to charge the sub-surface line set with 50 pounds, for example, of dry nitrogen and then release the charge through the liquid line for one minute only. If the lines are not restricted, in a one minute pressure release period, there will typically be: a 30 psi to 35 psi pressure drop in an approximate 195 foot long line set; an approximate 20 psi to 32 psi pressure drop in an approximate 255 foot long line set; and an approximate 18 psi to 25 psi pressure drop in an approximate 255 foot long line set.
A second test option would be to drop a small lightweight plastic ball, or the like, into one of the lines at the above-surface end of the line set. Such a ball would preferably be small enough to roll through the U bend at the bottom and/or distal end of the sub-surface refrigerant loop, but would be large enough to be blocked by any significant restriction and/or kink in the line set. The ball would be blown out of the line set by means of a relatively small amount of dry nitrogen, or the like, such as only 50 psi. If the ball could not be blown out, a restriction would be evidenced. In such event, the dry nitrogen pressure would be blown into the opposite line to retrieve the ball and the test could be repeated. If the results were the same via two tests, the line set should be retrieved, repaired, and re-inserted prior to grouting and/or backfilling. A preferable plastic ball for testing in a ⅜ inch O.D. liquid refrigerant transport line would be a 6 millimeter, 0.24 caliber, plastic ball, such as that used in pellet guns, distributed by AirStrike, of P.O. Box 220, Rogers, Ariz., USA, 72757. such a plastic ball is lightweight enough to be easily blown out of a good and unrestricted line set, is tough enough not to crumble or break into pieces during testing, is large enough to become stopped by a significant restriction, and is small enough to pass through ⅜ inch O.D. tubing that has been cut with tubing cutters, but not reamed out.
A preferable testing procedure would consist of dropping such a 6 mm plastic ball, into the top open end of the vapor refrigerant transport line extending from the top of the well, and waiting for about one full minute per 300 feet of depth, so as to insure the ball falls to the bottom. Next, a pressure hose would be attached and taped/sealed to the top end of the vapor refrigerant transport line, and a net, a sock, or the like, would be secured to the top open end of the smaller diameter liquid refrigerant transport line exiting the top of the well/borehole. 50 psi of pressure, preferably consisting of dry nitrogen, would then be sent into the vapor refrigerant transport line via the pressure hose. The other end of the pressure hose would be attached to a refrigerant gauge set also attached to a pressurized container of dry nitrogen, which container supplies the pressurized nitrogen for the test. If the sub-surface refrigerant transport tubing is not restricted, the plastic ball will be pushed up and out of the liquid refrigerant transport line, into the net or sock, at a rate of about 25 feet per second, plus or minus 4 feet per second.
A 6 mm plastic ball would be preferable for use with a ⅜ inch O.D. liquid refrigerant transport line, which is coupled to a larger O.D. vapor refrigerant transport line, such as a ¾ inch O.D. vapor transport line, at the lower distal end of the sub-surface refrigerant transport loop. Such a 6 mm sized plastic ball is large enough to be stopped by any significant restriction, but is small enough to pass through any minor kink in the refrigerant lines, and is small enough to pass through any refrigerant segment that has been cut with refrigerant tubing cutters and accidentally not reamed out.
If the liquid refrigerant transport line is larger than a refrigeration grade ⅜ inch O.D. line, with a 0.032 inch wall thickness, then a proportionately larger sized plastic ball needs to be used. If the liquid refrigerant transport line is smaller than a refrigeration grade ⅜ inch O.D. line, with a 0.032 inch wall thickness, then a proportionately smaller sized plastic ball needs to be used.
Preferably, the test will be conducted before the well is grouted, so that if there is a problem, the tubing can be withdrawn from the well and repaired prior to grouting. This simple test can save thousands of dollars and time, otherwise lost if a refrigerant transport line is only found to be restricted by means of the traditional DX system operational test, after full job completion. A defective/restricted line set, after full job completion, can only be corrected by means of installing a complete new replacement line set, within a newly drilled and grouted well.
BRIEF DESCRIPTION OF THE DRAWINGS
The following detailed description is of the best presently contemplated mode of carrying out the invention. The description is not intended in a limiting sense, and is made solely for the purpose of illustrating the general principles of the invention. The various features and advantages of the present invention may be more readily understood with reference to the following detailed description taken in conjunction with the accompanying drawings.
Referring now to the drawings in detail, where like numerals refer to like parts or elements, there is shown in
A refrigerant fluid (not shown) is transported, by means of a compressor's 1 force and suction, inside a larger diameter un-insulated sub-surface refrigerant vapor transport/heat exchange line tube 11, which is located below the ground surface 4 within a heat conductive, watertight pipe 5. A smaller diameter sub-surface liquid refrigerant transport line tube 2, which is surrounded by insulation 3, also extends within the heat conductive, watertight pipe 5 all the way to the pipe's sealed lower end/bottom 6, which pipe 5 has been inserted into a deep well borehole 7 all the way to the bottom 8 of the deep well borehole 7. As the sub-surface liquid refrigerant transport tube 2 reaches the sealed pipe bottom 6, the sub-surface liquid tube 2 forms a U bend 9, which constructively acts as a liquid refrigerant trap, and the sub-surface liquid tube 2 is thereafter coupled, with a refrigerant tube coupling 10, to the larger diameter un-insulated sub-surface refrigerant vapor transport/heat exchange tube 11. As the refrigerant fluid flows down within the larger diameter un-insulated sub-surface refrigerant transport/heat exchange line tube 11, on its way to the smaller diameter sub-surface liquid refrigerant transport line tube 2, the refrigerant transfers heat into the cooler natural earth 23 geothermal surroundings below the ground surface 4 and is condensed into a cool liquid refrigerant form, as heat always travels to cold.
The cooled refrigerant fluid, which has rejected excessive heat into the earth 23 below the ground surface 4, condenses into a mostly liquid refrigerant form and travels up from the U bend 9 near/at the sealed pipe's lower end/bottom 6 into an exterior refrigerant transport liquid line tube 25, which is surrounded by insulation 3, through an exterior structure wall 24, and into interior liquid refrigerant transport line tubing 27. The liquid refrigerant then travels around and through the first pin restrictor 29 (in the heating mode, which is not shown as the reverse cycle mode of operation is well understood by those skilled in the art, the refrigerant flows in a reverse direction only through the hole in the center of the pin restrictor, and not additionally around the pin, so that the flow of the refrigerant is restricted and metered, as is well understood by those skilled in the art) within the first single piston metering device 20, through the receiver 18, which automatically adjusts the optimum amount of refrigerant charge flowing through the system in each of a heating mode and a cooling mode. In the cooling mode, most all of the refrigerant flows out of the bottom 35 of the receiver 18, while in the heating mode (not shown), when the refrigerant is flowing in the opposite direction through the receiver 18 (as is well understood by those skilled in the art), the receiver 18 fills with liquid to a predetermined containment point 36, which point 36 is calculated for maximum capacity so as to contain one pound of refrigerant for every forty feet in depth of the liquid line 2 within the deep well/borehole 7. However, for optimal efficiency, the receiver 18 fills with liquid to a predetermined containment point 36, which point 36 is calculated for maximum capacity so as to contain one pound of refrigerant for every fifty feet in depth of the liquid line 2 within the deep well/borehole 7. The said respective one pound per 40 feet, or per 50 feet, containment point 36 design within the receiver 18 is preferably calculated based upon the depth of a ⅜ inch O.D. liquid refrigerant grade transport line 2, situated within a well/borehole 7, within a DWDX system design, or the equivalent thereof when other line set sizes are utilized, exclusive of the trenched line(s) to/from the well(s) (not shown herein but well understood by those skilled in the art) and exclusive of any other DX system refrigerant containment components.
In the heating mode, when the refrigerant flow travels through the first single piston metering device 20, as is well understood by those skilled in the art even though not shown herein, the optimum sizing of the first pin restrictor 29 within the first single piston metering device 20, is as explained and set forth under Summary Of Invention, Number 2, hereinabove, which is incorporated herein by reference. Although in a typically cooling to heating season period, the ground, which has been absorbing rejected heat all summer, will typically cool enough to permit instant DX system heating mode operation with only a properly sized heating mode first pin restrictor 29, if the seasonal change is extremely abrupt and fast, a pressure regulated heating mode refrigerant by-pass vale 41 within a heating mode by-pass line 42 around the heating mode pin restrictor 29 may be necessary so as to permit instant system heating mode operation without the system tripping off via its safety high pressure cut off switch 43 (the operation of a pressure regulated valve and of a high pressure cut-off switch are well understood by those skilled in the art and are therefore not shown in detail herein). To accomplish this optional heating mode protective means, one should preferably add a heating mode by-pass pressure regulated valve 41, also referred to as an automatic expansion valve (“AXV”), so as to assist transition from the cooling mode to the heating mode so that the valve opens to a specifically designed interior diameter, as is more fully set forth hereinabove under Summary Of Invention, Number 3, hereinabove, which is incorporated herein by reference.
The refrigerant then flows through the self-adjusting thermal expansion valve 16, as well as through a thermal expansion valve by-pass line 17, which line 17 contains a second single piston metering device 37, also known as a thermal expansion pin restrictor device. The thermal expansion valve by-pass line 17 and second pin restrictor 38 within the second single piston metering device 37 permits enough refrigerant flow to by-pass the self-adjusting thermal expansion valve 16 so as to enable system operation in the cooling mode at the beginning of the cooling season when the ground is very cold, but does not permit enough refrigerant to by-pass the self-adjusting thermal expansion valve 16 so as to materially impair system operation when the ground warms up by means of heat rejection during the warm summer months. The optimum sizing of the second pin restrictor 38 within the second single piston metering device 37, all within the by-pass line 17, is as explained and set forth under Summary Of Invention, Number 4, hereinabove, which is incorporated herein by reference.
The refrigerant fluid next flows through interior located finned heat exchange tubing 14, also commonly called an air handler, with an adjacent fan 15 designed to blow hot interior air over the cooler refrigerant fluid within the finned heat exchange tubing 14 so as enable the cooler refrigerant to absorb and remove excess heat from the interior air.
The warmed refrigerant fluid, having absorbed excessive heat from the interior air, is transformed into a mostly vapor state, and then flows through an interior located reversing valve 12, into an accumulator 13, which catches and stores any liquid refrigerant which has not fully evaporated, and then travels into the compressor 1. The compressor 1 compresses the cooler refrigerant vapor into a hot refrigerant gas/vapor. The hot refrigerant vapor then travels, by means of the force of the compressor 1, through the oil separator 30. The oil separator 30 has a small oil return line 31 that returns oil, which has escaped from the compressor 1, to the suction line portion 32 of the interior vapor refrigerant transport line tubing 28, which suction line portion 32 is located prior and proximate to the accumulator 13, by means of oil return line alternate route A 33. In an alternative, the oil could be returned, by means of the oil return line 31, directly into the accumulator 13, as is shown herein by means of oil return line alternate route B 34. The refrigerant fluid then travels through the interior located reversing valve 12, back through the exterior structure wall 24, through the exterior refrigerant transport vapor line tube 26, which is surrounded by insulation 3, and back into the larger diameter un-insulated sub-surface refrigerant vapor transport/heat exchange line tube 11, which is located below the ground surface 4, where the geothermal heat exchange process is repeated.
All above ground surface 4 interior liquid refrigerant transport line tubing 27, and all above ground surface 4 interior vapor refrigerant transport line tubing 28, are fully insulated with rubatex, or the like, as is common in the trade, which is well understood by those skilled in the art and, therefore, is not shown herein.
So as to avoid non-heat conductive air gaps, the remaining interior portion of the heat conductive watertight pipe 5, located below the ground surface 4, is filled with a heat conductive fluid mixture of water and anti-freeze 21. For a similar purpose, the space below the ground surface 4, between the exterior wall of the pipe 5 and the interior wall of the deep well borehole 7, is filled with a heat conductive grout 22, which is in direct thermal contact with the adjacent and surrounding earth 23.
An optional low pressure cut-off switch 19 is also shown for a secondary means of compressor 1 shut-off in the event of a refrigerant leak or other low pressure operational event. If used, the low pressure cut-off switch 19 should be set/designed not to shut off the compressor 1 unless there has been a continuous minimum of 10 minutes of system operation under pressure conditions below the requisite minimum. However, even though shown herein, it is preferably unnecessary to employ the use of a secondary low pressure cut off switch 19, since the compressor's own internal safety cut-off mechanism will shut the compressor off should it become overheated due to an inordinate period of operation under too low of a refrigerant pressure condition. Thus, in a preferable design, the low pressure cut of switch 19 shown here would simply be eliminated.
In lightening prone areas, such as the State of Florida, a design improvement to help prevent attracting lightening to underground copper tubing would consist of placing a non-electrical conductive covering 39, such as a rubber mat or the like, over the top of the well/borehole
The operation of a low pressure cut-off switch 19, a compressor 1, an electric powered fan 15, a self-adjusting thermal expansion valve 16, and their requisite and appropriate electrical wiring, as well as the operation of all other system components, are well understood by those skilled in the art and are, therefore, neither shown nor described herein in detail.
Preferably, the valve 52 is designed to open to an interior diameter of at least the size of the actual BTU size, in thousandths, of the compressor (the system's compressor is not shown herein, but is number 1 in
Alternately, although not as precise as individually tailored by-pass valves for each respective compressor size, a one size fits all valve opening to the actual BTU size, in thousandths, should preferably be as explained and set forth under Summary Of Invention, Number 5, hereinabove, which is incorporated herein by reference.
The AXV valve 52 should be an external equalized valve, with a capillary tube 53 extended from the AXV valve 52 to the low pressure vapor line exiting the air handler 51. The AXV valve 52 should preferably be an adjustable type valve that can be set to shut off at any pressure between 40 psi and 100 psi., with an 85 psi shut off point being preferable for a DX system application. A standard automatic self-adjusting thermal expansion valve 16 is also shown herein, which standard valve 16 is well understood by those skilled in the art.
Additionally, differing air handler 51 manufacturers utilize differing finned tubing 14 lengths per ton of size design capacity. However, most air handler 51 manufacturers utilize finned tubing 14 with twelve to fourteen fins per inch length. Since differing manufacturers utilize differing lengths of tubing per ton of design capacity, it is inefficient to prescribe a certain tonnage air handler 51 to be used with a particular DX system BTU compressor (compressor not shown herein, but is number 1 in
A. Total depth of the ⅜ inch O.D. liquid line 55 in the well 7 times 0.0375 pounds. The total depth is the distance between the top 56 of the well 7 and the liquid line U bend 9 near the bottom 8 of the well 7 in the earth 23.
B. 50% of total length of finned ⅜ inch O.D. tubing 14 in the in the air handler 51 multiplied by 0.0375 pounds.
C. Compressor unit/box 49 content of liquid refrigerant.
D. Add the amount of liquid refrigerant contained in the system's filter/dryer 46 (for example, a Parker Bi-Directional R-410A Heat Pump Filter/Dryer Model BF164-XF holds about 0.761875 pounds), exclusive of any filter/dryer in the compressor box 49, which has already been taken into account in the compressor unit/box 49 content.
E. Add the amount of liquid refrigerant in all liquid line ball cut-off valves, 45 and 48 (typically about 0.05 pounds each), exclusive of the ball cut-off valves, if any, in the compressor box 49, which have already been taken into account in the compressor unit/box 49 content.
F. Measure the total liquid transport line 55 length between the top 56 of the well/borehole 7, shown here at the ground surface 4, and the compressor unit/box 49 and multiply by the full liquid refrigerant weight content of the liquid refrigerant transport line 55 in pounds. For example, multiply by 0.0375 pounds if it is a preferred ⅜ inch O.D. refrigerant grade copper line 55, but multiply by 0.06875 if it is a ½ inch O.D refrigerant grade copper line. Although the liquid transport line 55 is shown here as being located between the top 56 of the well/borehole 7 and the compressor unit/box 49 at an above ground surface 4 location, this segment of the liquid transport line 55 is typically buried below the ground surface 4 (not shown herein but well understood by those skilled in the art).
G. Measure the total liquid transport line 55 length between the air handler 51 and the compressor unit/box 49 and multiply by the full liquid weight content of the line in pounds. For example, multiply by 0.0375 pounds if it is a ⅜ inch O.D. line 55, but multiply by 0.06875 if it is a ½ inch O.D line.
H. For a cooling mode charge, add an additional one pound of refrigerant for every forty feet of ⅜ inch O.D. refrigerant grade liquid line 55 in the well for maximum system operational capacity and humidity removal. If humidity removal is not a concern, add an additional one pound of refrigerant for every fifty feet of ⅜ inch O.D. refrigerant grade liquid line 55 in the well for maximum efficiency.
I. If the system is designed to operate in a reverse-cycle mode (heating and cooling), the system must have a liquid line receiver 18 that holds the preferred charge differential between the heating mode and the cooling mode. Additionally, the receiver 18, which should preferably have only one refrigerant entrance 58 and only one refrigerant exit 59, will typically have some constant amount of liquid content in its bottom, regardless of the system operational mode, which constant amount of refrigerant, in pounds, must be added.
J. If the system is designed to operate in the heating mode with a heating mode pin expansion device/single piston metering device 20, shown here as installed between the filter/dryer 46 and the secondary cut-off valve 48, the weight, in pounds, of the liquid refrigerant content of the single piston metering device 20 must be added to the total.
The total of the appropriate above sums will equal the correct system charge.
To determine the optimum charge in DX systems utilizing other than ⅜ inch O.D. liquid refrigerant transport lines 55 and ¾ inch O.D., or larger, vapor refrigerant transport lines 57, the charge should preferably be determined by the above formula, except the equivalent refrigerant content of the actual interior volume of the liquid refrigerant transport line used must be matched to the interior volume of a ⅜ O.D. liquid refrigerant grade transport line/tube 55 as per the above formula. For example, if multiple liquid refrigerant transport lines of a smaller interior diameter were utilized than that of a ⅜ inch O.D. refrigerant grade copper tube 55, then the content of all multiple smaller lines must match that of the content of a system designed with at least one of one and multiple ⅜ inch O.D. refrigerant grade copper tube(s) 55. As another example, if a larger liquid refrigerant transport line was used than that of a ⅜ inch O.D. refrigerant grade copper tube, then the interior content of the larger tube must match that of the content of a system designed with at least one of one and multiple ⅜ inch O.D. refrigerant grade copper tube(s) 55.
The holding spool should preferably have sides 65 extending past the outer layer 63 of the pre-assembled refrigerant transport line set 61, but with a four foot, or less, total side diameter 64 so as to facilitate shipping on a standard four foot wide pallet.
Prior to assembly, the pre-assembled line set 61, with a cementitious grout-filled (preferably Grout 111) “Torpedo” unit 66 should be evacuated of air with a vacuum pump 67. The vacuum pump 67 has an external electrical power supply line 68 (vacuum pumps are well understood by those skilled in the art), and should preferably be used to pull at least a 250 micron vacuum. The line set 61 and Torpedo unit 66 should then preferably be charged with a dry nitrogen holding charge of 50 pounds, or the like, for shipment and installation. Charging with a 50 pound holding charge of dry nitrogen is well understood by those skilled in the art and is therefore not shown herein.
The 250 micron vacuum will insure there are no leaks, and the 50 pound holding charge will insure no leaks have occurred during either shipment or installation. Both pulling the vacuum and inserting the holding charge of dry nitrogen are effected by means of capping 68 one of the ends of at least one of the liquid refrigerant transport line 2 and the vapor refrigerant transport line 11, and then placing a schraeder valve 69 (a schraeder valve is well understood by those skilled in the art) at the end of the other for refrigeration gauge set attachment (refrigeration gauges are well understood by those skilled in the art and are therefore not shown herein). This procedure comprises a significant time saving and efficiency improvement over the historical and traditional method of installing sub-surface heat exchange tubing in a DX system, where the tubing is installed, sealed, and pressure tested prior to pulling a vacuum and charging, which is more time consuming and is not as trustworthy as initially pulling a vacuum. Pulling a vacuum cannot be done to 250 microns in a DX system if there is a leak, whereas a pressure test could take hours or days to reveal a very slight leak.
In such a DX trench system, one smaller diameter liquid refrigerant transport line 2 would be coupled to one larger diameter vapor refrigerant transport line 11 at the distal end 72 of the sub-surface heat exchange loop.
In such a DX trench system, the liquid refrigerant transport line 2 would preferably be comprised of one 120 foot long ⅜ inch O.D. refrigerant grade copper tube, or the like, per ton of system design capacity, with a maximum 360 foot distance per liquid line 2 segment in each respective loop.
In such a DX trench system, the vapor refrigerant transport line 11 would preferably be comprised of one 120 foot long ¾ inch O.D. refrigerant grade copper tube, or the like, per ton of system design capacity, with a maximum 360 foot distance per vapor line segment in each respective loop. Further, the vapor line 11 must be at least one of horizontally and downwardly sloped 73 toward the distal end 72, with a downward slope being preferred.
In such a DX trench system, neither the vapor refrigerant transport line 11 used for subsurface heat exchange, nor the liquid refrigerant transport line 2 used for subsurface heat exchange, would be insulated, and the respective vapor line 11 and liquid line 2, except for being coupled together at the distal end 72 of the loop, would be separated by at least twenty feet, with a thirty foot separation being preferable where land area permits. When the vapor line 11 and liquid line 2 near one another for connection to the DX system compressor unit, each line, 11 and 2, should preferably be fully insulated 3, with a closed cell insulation 3 (such as expanded polyethylene and/or neoprene, or the like) when they are at least within twenty feet of one another.
The larger diameter, sub-surface, vapor refrigerant transport tubing 11 should preferably be comprised of ¾ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with up to a 30,000 BTU compressor. The larger diameter vapor refrigerant transport tubing 11 should preferably be comprised of ⅞ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with a 31,000 BTU compressor up to an 83,000 BTU compressor. When smaller vapor refrigerant transport tubing/lines is used (not shown herein), the interior diameter of the smaller tubing/lines should preferably approximately equal the interior diameter of the respective ¾ inch O.D. and ⅞ inch O.D. lines as described in this paragraph matching the varying respective compressor sizes.
The connecting smaller diameter liquid refrigerant transport line 2, which will travel from the distal and lowest end 76 of the larger vapor refrigerant transport tubing 11 back to the system's compressor unit, should preferably be comprised of ⅜ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with up to a 30,000 BTU compressor. The connecting liquid refrigerant transport line 2, which will travel from the distal and lowest end 76 of the larger vapor refrigerant transport tubing 11 back to the system's compressor unit, should be comprised of ½ inch O.D. refrigerant grade copper tubing, or the like, for use in conjunction with a 31,000 BTU compressor up to an 83,000 BTU compressor. When smaller liquid refrigerant transport tubing is used (not shown herein), the interior diameter of the smaller tubing/lines should preferably approximately equal the interior diameter of the respective ⅜ inch O.D. and ½ inch O.D. lines as described in this paragraph with the varying respective compressor sizes.
While submerged heat exchange tubing may be placed within a protective polyethylene containment box 78 covering, preferably a containment box 78 comprised of at least one of titanium and Grout 111 would be utilized, as polyethylene has a relatively poor heat transfer rate of only 0.225 BTUs/Ft. Hr. degrees F. However, protective piping 83, within which both the un-fined vapor refrigerant transport line 11 and the liquid refrigerant transport line 2 (traveling to and from the heat exchange tubing 11, with fins 77, within the containment box 78) may be placed, may be comprised of a polyethylene pipe 84, or the like. Insulation 3 would preferably be placed around all refrigerant transport tubing, 2 and 11, situated above the water 75.
Weight to offset the buoyancy created by the insulation 3 may preferably be added to a DX system by means of taping/tying 90 maximum five foot segments 86 of maximum two inch diameter steel, or the like, tubing/bars (two inch diameter weighs 10.68 pounds per foot . . . 1.75 inch diameter weighs 8.18 pounds per foot . . . 1.5 inch diameter weighs 6.01 pounds per foot) or smaller re-bar, or the like, to the refrigerant transport line set, comprised of the liquid refrigerant line 2, the vapor refrigerant line 11, and insulation 3 around the liquid line 2, as needed. Prior to attachment by means of taping/tying 90, the steel, or the like, tubing/bar maximum five foot long segment 86 to the copper tubing, 2 and 11, the segment 86 should preferably be wrapped in a protective wrapping 87, such as shrink wrap, tape, or the like, so as to protect the copper refrigerant transport tubing, 2 and 11. Add as many segments 86 of maximum five foot long steel tubing segments 86 as necessary to offset the buoyancy, which is dependent upon the depth of the water 75 within the well/borehole 7.
However, there must not be a vertical gap (not shown) between the segments 86 being added. If a vertical gap exists, which is historically permissible when plastic polyethylene pipe (not shown) is used to transport water 75 as a geothermal heat exchange fluid, the soft copper refrigerant transport tubing, 2 and 11, in a DX system application could be crimped/damaged during installation. Thus, in a DX system application, it is critical that the segments 86 must be placed directly above one another 88 or slightly overlapped 89. A maximum of five foot long segments 86 should be used in a DX system application so as to avoid damaging the copper refrigerant transport tubing, 2 and 11, and so as to avoid jamming the insertion, when the well/borehole 7 is not perfectly straight, as it seldom is. While longer than five foot segments 86 may be used when water-filled polyethylene pipe (not shown herein) is used as a heat transfer agent in a water-source heat pump system application (a water-source heat pump system is well understood by those skilled in the art and is not shown herein), since plastic pipe is typically more flexible than copper tubing, 2 and 11, in a DX system application, segments 86 should preferably be limited to a maximum of five foot lengths, with a maximum of four foot lengths being preferable.
The taping/tying 90 of the maximum five foot long segments 86 to the copper refrigerant transport tubing, 2 and 11, should be done at the top 91 and at the bottom 92 of the segments 86 only, so as to only place a minimum of heat transfer inhibiting tape 90, or the like, around the vapor refrigerant transport line 11 used for geothermal heat transfer, and so as to permit some flexibility between the segments 86 during installation into a well/borehole 7 that may not be perfectly straight, so as to avoid jamming.
When water 75 is encountered in a well 7 during a DX system copper tubing, 2 and 11, installation, where the liquid refrigerant transport line 2 is insulated 3, one should drop the copper tubing, 2 and 11, as far as possible via its own weight, and then securely apply a protective wrapping 87 of tape, shrink wrap, or the like, on maximum five foot long segments 86 of steel tubing, or the like, only as periodically necessary to continue the installation to its full well/borehole 7 design depth, which design depth is typically at least one hundred feet per ton of system design capacity.
Preferably, so as to avoid any undue wear on the heat exchange tubing within the concrete shell of a swimming pool, or the like, the heat exchange tubing 95 would be coated with a plastic coating 93, thick enough to protect the tubing, but thin enough so as not to unduly inhibit heat transfer.
In a swimming pool (not shown) heating application, for example, in order to enhance even heat exchange throughout the pool, decreasing thicknesses of the plastic coating 93 would be utilized.
A refrigerant fluid (not shown) is transported, by means of a compressor's 1 force and suction, inside a larger diameter un-insulated sub-surface refrigerant vapor transport/heat exchange line tube 11, which is located below the ground surface 4 within a heat conductive, watertight pipe 5. A smaller diameter sub-surface liquid refrigerant transport line tube 2, which is surrounded by insulation 3, also extends within the heat conductive, watertight pipe 5 all the way to the pipe's sealed lower end/bottom 6, which pipe 5 has been inserted into a deep well borehole 7 all the way to the bottom 8 of the deep well borehole 7. As the sub-surface liquid refrigerant transport tube 2 reaches the sealed pipe bottom 6, the sub-surface liquid tube 2 forms a U bend 9, which constructively acts as a liquid refrigerant trap, and the sub-surface liquid tube 2 is thereafter coupled, with a refrigerant tube coupling 10, to the larger diameter un-insulated sub-surface refrigerant vapor transport/heat exchange tube 11. As the refrigerant fluid flows down within the larger diameter un-insulated sub-surface refrigerant transport/heat exchange line tube 11, on its way to the smaller diameter sub-surface liquid refrigerant transport line tube 2, the refrigerant transfers heat into the cooler natural earth 23 geothermal surroundings below the ground surface 4 and is condensed into a cool liquid refrigerant form, as heat always travels to cold.
The cooled refrigerant fluid, which has rejected excessive heat into the earth 23 below the ground surface 4, condenses into a mostly liquid refrigerant form and travels up from the U bend 9 near/at the sealed pipe's lower end/bottom 6 into an exterior refrigerant transport liquid line tube 25, which is surrounded by insulation 3, through an exterior structure wall 24, and into interior liquid refrigerant transport line tubing 27. The liquid refrigerant then travels around and through the first pin restrictor 29 (in the heating mode, which is not shown as the reverse cycle mode of operation is well understood by those skilled in the art, the refrigerant flows in a reverse direction only through the hole in the center of the pin restrictor, and not additionally around the pin, so that the flow of the refrigerant is restricted and metered, as is well understood by those skilled in the art) within the first single piston metering device 20, through the receiver 18, which automatically adjusts the optimum amount of refrigerant charge flowing through the system in each of a heating mode and a cooling mode. In the cooling mode, most all of the refrigerant flows out of the bottom 35 of the receiver 18, while in the heating mode (not shown), when the refrigerant is flowing in the opposite direction through the receiver 18 (as is well understood by those skilled in the art), the receiver 18 fills with liquid to a predetermined containment point 36, which point 36 is calculated for maximum capacity so as to contain one pound of refrigerant for every forty feet in depth of the liquid line 2 within the deep well/borehole 7. However, for optimal efficiency, the receiver 18 fills with liquid to a predetermined containment point 36, which point 36 is calculated for maximum capacity so as to contain one pound of refrigerant for every fifty feet in depth of the liquid line 2 within the deep well/borehole 7. The said respective one pound per 40 feet, or per 50 feet, containment point 36 design within the receiver 18 is preferably calculated based upon the depth of a ⅜ inch O.D. liquid refrigerant grade transport line 2, situated within a well/borehole 7, within a double direct exchange heating/cooling system using a DWDX system design, or the equivalent thereof when other line set sizes are utilized, as one of its primary heat sources/heat sinks, exclusive of the trenched line(s) to/from the well(s) (not shown herein but well understood by those skilled in the art) and exclusive of any other DX system refrigerant containment components.
In the heating mode, when the refrigerant flow travels through the first single piston metering device 20, as is well understood by those skilled in the art even though not shown herein, the optimum sizing of the first pin restrictor 29 within the first single piston metering device 20, is as explained and set forth under Summary Of Invention, Number 2, hereinabove, which is incorporated herein by reference. Although in a typically cooling to heating season period, the ground, which has been absorbing rejected heat all summer, will typically cool enough to permit instant DX system heating mode operation with only a properly sized heating mode first pin restrictor 29, if the seasonal change is extremely abrupt and fast, a pressure regulated heating mode refrigerant by-pass vale 41 within a heating mode by-pass line 42 around the heating mode pin restrictor 29 may be necessary so as to permit instant system heating mode operation without the system tripping off via its safety high pressure cut off switch 43 (the operation of a pressure regulated valve and of a high pressure cut-off switch are well understood by those skilled in the art and are therefore not shown in detail herein). To accomplish this optional heating mode protective means, one should preferably add a heating mode by-pass pressure regulated valve 41, also referred to as an automatic expansion valve (“AXV”), so as to assist transition from the cooling mode to the heating mode so that the valve opens to a specifically designed interior diameter, as is more fully set forth hereinabove under Summary Of Invention, Number 3, hereinabove, which is incorporated herein by reference.
The refrigerant then flows through the self-adjusting thermal expansion valve 16, as well as through a thermal expansion valve by-pass line 17, which line 17 contains a second single piston metering device 37, also known as a thermal expansion pin restrictor device. The thermal expansion valve by-pass line 17 and second pin restrictor 38 within the second single piston metering device 37 permits enough refrigerant flow to by-pass the self-adjusting thermal expansion valve 16 so as to enable system operation in the cooling mode at the beginning of the cooling season when the ground surrounding the deep well 7 is very cold, but does not permit enough refrigerant to by-pass the self-adjusting thermal expansion valve 16 so as to materially impair system operation when the ground surrounding the deep well 7 warms up by means of heat rejection during the warm summer months. The optimum sizing of the second pin restrictor 38 within the second single piston metering device 37, all within the by-pass line 17, is as explained and set forth under Summary Of Invention, Number 4, hereinabove, which is incorporated herein by reference.
The refrigerant fluid next flows through the secondary (the double) direct exchange convective heat transfer/refrigerant transport heat exchange tubing segment 99. Here, the secondary convective heat transfer segment 99 is shown as a distributed array of small refrigerant transport tubes, as such a segment 99 would appear within a concrete, or the like, wall (the concrete wall is not shown, as a concrete wall is well understood by those skilled in the art). As would be well understood by those skilled in the art, any form of DX heat exchange refrigerant transport tubing convective heat transfer means may be used as the secondary direct exchange convective heat transfer/refrigerant transport heat exchange tubing segment 99, which segment is not limited to the design as shown herein. As heat naturally flows to cold, the heat in the wall would be absorbed by the cooler refrigerant (refrigerant is not shown as refrigerant is well understood by those skilled in the art) flowing through the secondary convective heat exchange tubing 99 within the wall. Thus, the cooler refrigerant would absorb and remove excess heat from the wall, which wall could be at least one of the wall of a structure, a swimming pool, and the like. The wall would, of course, be absorbing heat from the interior air of a structure (not shown herein), from the water within a swimming pool (not shown herein), and/or from any other heat source (not shown herein).
The warmed refrigerant fluid, having absorbed excessive heat from the secondary convective heat exchange tubing 99, is transformed into a mostly vapor state, and then flows through an interior located reversing valve 12, into an accumulator 13, which catches and stores any liquid refrigerant which has not fully evaporated, and then travels into the compressor 1. The compressor 1 compresses the cooler refrigerant vapor into a hot refrigerant gas/vapor. The hot refrigerant vapor then travels, by means of the force of the compressor 1, through the oil separator 30. The oil separator 30 has a small oil return line 31 that returns oil, which has escaped from the compressor 1, to the suction line portion 32 of the interior vapor refrigerant transport line tubing 28, which suction line portion 32 is located prior and proximate to the accumulator 13, by means of oil return line alternate route A 33. In an alternative, the oil could be returned, by means of the oil return line 31, directly into the accumulator 13, as is shown herein by means of oil return line alternate route B 34. The refrigerant fluid then travels through the interior located reversing valve 12, back through the exterior structure wall 24, through the exterior refrigerant transport vapor line tube 26, which is surrounded by insulation 3, and back into the larger diameter un-insulated sub-surface refrigerant vapor transport/heat exchange line tube 11, which is located below the ground surface 4, where the geothermal heat exchange process is repeated.
All above ground surface 4 interior liquid refrigerant transport line tubing 27, and all above ground surface 4 interior vapor refrigerant transport line tubing 28, are fully insulated with rubatex, or the like, as is common in the trade, which is well understood by those skilled in the art and, therefore, is not shown herein.
So as to avoid non-heat conductive air gaps, the remaining interior portion of the heat conductive watertight pipe 5, located below the ground surface 4, is filled with a heat conductive fluid mixture of water and anti-freeze 21. For a similar purpose, the space below the ground surface 4, between the exterior wall of the pipe 5 and the interior wall of the deep well borehole 7, is filled with a heat conductive grout 22, which is in direct thermal contact with the adjacent and surrounding earth 23.
An optional low pressure cut-off switch 19 is also shown for a secondary means of compressor 1 shut-off in the event of a refrigerant leak or other low pressure operational event. If used, the low pressure cut-off switch 19 should be set/designed not to shut off the compressor 1 unless there has been a continuous minimum of 10 minutes of system operation under pressure conditions below the requisite minimum. However, even though shown herein, it is preferably unnecessary to employ the use of a secondary low pressure cut off switch 19, since the compressor's own internal safety cut-off mechanism will shut the compressor off should it become overheated due to an inordinate period of operation under too low of a refrigerant pressure condition. Thus, in a preferable design, the low pressure cut of switch 19 shown here would simply be eliminated.
In lightening prone areas, such as the State of Florida, a design improvement to help prevent attracting lightening to underground copper tubing would consist of placing a non-electrical conductive covering 39, such as a rubber mat or the like, over the top of the well/borehole
The operation of a low pressure cut-off switch 19, a compressor 1, an electric powered fan 15, a self-adjusting thermal expansion valve 16, and their requisite and appropriate electrical wiring, as well as the operation of all other system components, are well understood by those skilled in the art and are, therefore, neither shown nor described herein in detail.
Here, a small ball 103, such as a small plastic ball 103, is dropped into the top portion 81 of the vapor line 11, and is allowed to fall, by means of gravity, to the bottom of the tubing, 2 and 11 near the bottom 8 of the well 7. Next, a container of a pressurized gas 104, such as dry nitrogen or the like, is connected by means of a pressure hose 105 to the top portion 81 of the vapor line 11 and about fifty pounds of pressure, or the like, is supplied into the top portion 81 of the vapor line 11. The pressure of the gas will force the small ball 103 up through the smaller liquid line/tube 2, and eventually into the net 106 at the liquid line outlet 107. Typically, the ball 103 will exit a three hundred foot deep well within about twelve seconds if there are no restrictions in the tubing, 2 and 11. If any of the tubing, 2 and 11, is unduly restricted, the ball 103 will not be able to exit during the integrity test. Preferably, the test will be conducted before the well is grouted (not shown herein as grouting is well understood by those skilled in the art), so that if there is a problem, the tubing, 2 and 11, can be withdrawn from the well 7 and repaired prior to grouting. This simple test can save thousands of dollars and time, otherwise lost if a refrigerant transport line, 2 and 11, is only found to be restricted by means of the traditional DX system operational test, after full job completion. A defective/restricted line set, 2 and 11, after full job completion, can only be corrected by means of installing a complete new replacement line set, 2 and 11, within a newly drilled and grouted well.
Claims
1. A direct expansion/direct exchange geothermal heating/cooling system comprising:
- a plurality of well units, each well unit including a plurality of refrigerant transportation lines;
- a compressor unit for processing refrigerant and operatively connected to the well units;
- a distributor operatively connected to the compressor;
- an energy distribution field operative connected to the compressor;
- a plurality of housing units, each housing unit positioned at a ground accessible location near the compressor unit and on the distribution field side of the distributor, each housing unit including a pin restrictor positioned in one of the refrigerant transportation lines;
- a plurality of cut-off ball valves, each cut-off ball valve located within one of the liquid refrigerant transport lines and positioned beside one of the housing units;
- a plurality of filters/dryers, each filter/dryer positioned in one of the refrigerant transportation lines proximate to one of the pin restrictors; and
- a plurality of refrigerant flow shut-off valves, each shut-off valves being positioned in one of the refrigerant transportation lines containing the filter/dryer and the distributor.
2. The system of claim 1 wherein the distributor is place in either a horizontal or vertical inclinations.
Type: Application
Filed: Jul 3, 2007
Publication Date: Jan 24, 2008
Inventor: B. Wiggs (Franklin, TN)
Application Number: 11/773,202
International Classification: F24J 3/08 (20060101);
