Refrigeration Purger Monitor

Abstract

An industrial refrigeration system has a purger for removing non-condensable content extracted from a volume of refrigerant. The purger separates a quantity of refrigerant from a mixture of refrigerant and air and purges the air and a portion of the refrigerant. The purger includes a control unit and an algorithm that estimates the purged quantity of refrigerant from measured and stored refrigeration and purger operating parameters.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/800,709, filed Mar. 15, 2013, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION

This invention relates in general to refrigeration systems including purger devices and to monitoring refrigerant loss, storing calculated loss as data and reporting the loss as part of EPA compliance reporting.

BACKGROUND OF THE INVENTION

This invention relates to automatic air purgers for industrial refrigeration systems. An automatic air purger separates and vents air by condensing refrigerant gas into a liquid state and venting the non-condensable gases that accumulate in the purger body.

During the condensing process there is a small amount of refrigerant gas that does not condense or is entrapped in the bulk of vented gas. This trapped refrigerant gas is vented to atmosphere along with any non-condensable gas. This separation process is dependant on system pressure and temperature at the time of discharge.

There is a need in the refrigeration industry to be able to estimate how much refrigerant gas is lost during the purger discharge cycle. This information is of value to the end user when justifying and reporting refrigerant losses to monitoring entities, such as the Environmental Protection Agency (EPA) or the Occupational Safety And Health Administration (OSHA).

SUMMARY OF THE INVENTION

This invention relates to industrial refrigeration systems, generally. In particular, this invention relates to refrigeration purger systems for industrial refrigeration systems. In one aspect of the invention, a refrigeration purger system includes a purger unit having an upper chamber and a lower chamber in fluid communication with the upper chamber, and a head connected to the upper chamber. The refrigeration system also includes at least one of a pressure sensor and a temperature sensor mounted on the head and configured to measure an associated state within the upper chamber. A control unit is connected to the at least one pressure and temperature sensor. The control unit has an algorithm that controls a purging cycle that purges air collected in the purger unit. The algorithm determines an estimate of refrigerant loss during the purging cycle.

In another aspect, a control unit for a refrigeration purger system has an algorithm configured to control a purging cycle that purges air collected in the purger unit. The algorithm is also configured to determine an estimate of refrigerant loss during the purging cycle. The algorithm includes a refrigerant lookup table having data associated with at least one of a refrigeration system operating pressure, a refrigerant density as a function of temperature, an air density as a function of temperature, a volumetric ratio of refrigerant to air as a function of temperature, and a weight ratio of refrigerant to air as a function of temperature. The algorithm further uses a purge duration parameter, a purger temperature parameter, and a purger refrigerant fluid level to estimate refrigerant loss.

In yet another aspect, a refrigeration system includes a compressor, a condenser in fluid communication with the compressor, an evaporator in fluid communication with the compressor; and a refrigeration purger system. The refrigeration purger system includes a purger unit having an upper chamber and a lower chamber in fluid communication with the upper chamber, and a head connected to the upper chamber. There is at least one of a pressure sensor and a temperature sensor mounted on the head and configured to measure an associated state within the upper chamber. A control unit is connected to the at least one pressure and temperature sensor. The control unit has an algorithm configured to control a purging cycle that purges air collected in the purger unit and determining an estimate of refrigerant loss during the purging cycle. The algorithm includes at least one refrigerant lookup table having data associated with a refrigerant property as a function of temperature and pressure. The algorithm also includes data related to refrigeration system operating parameters. A coil is disposed within the upper chamber and is in fluid communication with the compressor. The control unit maintains a condensing temperature within the upper chamber. The upper chamber includes a fluid level sensor configured to send a signal to the control unit that is proportional to a refrigerant level in the purger. The algorithm determines a purge time based on one of a refrigeration level, the condensing temperature, and the pressure within the purger.

Various aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a refrigeration system having a purger monitoring device in accordance with the invention.

FIG. 2 is a schematic illustration, in partial cross-section of a refrigeration purger and the purge monitoring device of FIG. 1.

FIG. 3 is an enlarged, cross-sectional view of an alternative embodiment of a purger for use with a purger monitoring device in accordance with the invention.

FIG. 4 is a flow chart of a method of determining purger refrigerant loss.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, there is illustrated in FIG. 1 a refrigeration system, shown generally at 10. The refrigeration system 10 includes a refrigerant 12 that is compressible between a first pressure and a second pressure, where the second pressure is higher than the first pressure. The system 10 includes both refrigerant 12 and a mix of refrigerant and air 12′. A compressor 14 pressurizes and pumps the refrigerant 12 through the system. The compressor 14 increases the refrigerant pressure from the first pressure to the second pressure. Refrigeration systems 10 and compressors 14 are designed to operate with a condensable and compressible fluid, such as refrigerant 12, which may be ammonia, an R-series refrigerant (including hydrocarbon-based; Freon-type—i.e., R-12, R-134a, and the like; carbon dioxide; and various blended or azoetropes thereof), and the like. Removal of non-condensable materials within the system 10 provides improved efficiency and reduces the frequency of mechanical failures. Materials other than refrigerant enter the system 10 through leak or entry points such as, for example, compressor seals, valve packings, system repair points, refrigeration charging points, impurities in the refrigerant, and breakdown of the refrigerant itself Materials that are non-condensable, such as air, need to be purged from the system 10. As used herein, the term “air” may include any non-condensable materials trapped in the condensable materials, such as refrigerant.

The compressed refrigerant 12 moves from the compressor 14 to a condenser 16 where heat energy is removed by a cooling medium 18, such as water or air. The cooled and compressed refrigerant, including entrapped air, passes to a receiver 20 where separation of liquid and gaseous phases takes place. The liquid refrigerant moves to an evaporator 22 where the pressure is decreased from the second pressure to the first pressure. This pressure decrease results in the refrigerant 12 absorbing heat energy and a corresponding temperature reduction of the evaporator 22 producing a cooling or refrigeration effect. Heat is removed from the material to be cooled by the evaporator 22 and transferred to the refrigerant 12. The heated refrigerant is returned to the compressor 14 where the cycle begins again. An oil separator 24 may be provided to remove liquid contaminants and oils, such as compressor lubricants and the like, from the compressed refrigerant.

A refrigeration purging system 26 is provided to permit the buildup of non-condensable gases to be evacuated, usually to the atmosphere. Alternatively, these vented gases may be collected and recycled. The refrigeration purging system 26 includes a purger 28 that separates condensable materials from non-condensable materials and purges the non-condensable materials from the system 10. The purging system 26 includes a piping network 30 that draws refrigerant and refrigerant/air, also known as “foul gas,” from various points in the system 10. The piping network 30 further includes solenoid valves, such as purger operational valves 32a-32c and purge point valves 32d-32e. The purger operational valves 32a-32c control the flow of refrigerant that is used to separate the condensable and non-condensable materials within the purger 28. The purge point valves 32d, 32e permit control of refrigerant and foul gas flow from the system 10 to the purger 28. The purge point valves 32d-32e permit sections of the system 10 where foul gas may build to be fluidly connected to the purger 28, typically at a point of reduced gas velocity. A portion of the piping network 30 includes a coil supply line 34 that provides a source of cooled, generally clean liquid refrigerant to the purger 28. The purger operational valves 32a-32c control the source of refrigerant within the system and refrigerant flow through coil supply line 34 to achieve the desired condensing temperature within the purger 28.

As shown in FIG. 1, foul gas may be collected at purger point valve 32d as foul gas exits the condenser 16. Foul gas is also collected at purger point valve 32e from an upper portion of the receiver 20. These two input feeds combine and are supplied to the purger 28. Purger operational valve 32a controls refrigerant/air flow from the receiver 20 to the purger 28 for establishing and maintaining the proper condensing temperature based on the refrigerant used in the system 10. Purger operational valves 32b and 32c control flow from the purger 28 to a fluid sealed filter or bubbler 30a, though such is not required.

Referring now to FIG. 2, the purger 28 includes an inlet 36 that permits a flow of refrigerant and foul gas to enter a lower chamber 38. A check valve 40 may be provided to regulate the fluid pressure delivered to the lower chamber 38. The lower chamber 38 is in fluid communication with an upper chamber 42 by way of a condensing channel 44. The condensing channel 44 permits liquid refrigerant 12 to flow, by way of gravity, and collect in the lower chamber 38. The condensing channel 44 further permits the gaseous, non-condensable material, such as foul gas, to percolate or bubble up to the upper chamber 42. The upper chamber 42 includes a lid or head 42a that seals the upper chamber and provides mounting locations for measurement pickups, as will be described below. A lower chamber outlet port 46 permits condensed refrigerant to be returned to the system 10, by way of the coil supply line 34. A supply of cooled refrigerant from the receiver 20, along with some of the condensed refrigerant from the lower chamber 38, is fed into the coil supply line 34, as shown in FIG. 1.

The cooled refrigerant from the coil supply line 34 is connected to a coil 48 at a coil inlet port 48a and permitted to exit through a coil outlet port 48b. The coil 48 is positioned within the upper chamber 42 of the purger 28. The coil 48 removes heat from the incoming foul gas to condense out refrigerant 12 and permit air to percolate to a top portion 50 of the upper chamber 42. The cooled and condensed refrigerant within the upper chamber 48 flows back into the lower chamber 38 and exits by way of the lower chamber outlet port 46. In the illustrated embodiment of FIG. 1, the lower chamber outlet port 46 also connects to the coil supply line 34, though such is not required.

The purger 28 includes a float 52 having a fluid level sensor 52a that measures the level of condensed refrigerant and outputs a signal related to the refrigerant level. The fluid level sensor 52a communicates data related to the fluid level to a control unit 54. The control unit 54 may be a programmable control unit that communicates information to a computer 56 or other device, either wirelessly, over the internet, or through an Ethernet or similar connection. The control unit 54 may include an input/display panel 54a that permits programming, data entry, and display of refrigerant loss estimates, if desired. Alternatively, such programming and data display or reporting may be transmitted to the computer 56 and provided in an output format as desired. The purger 28 further includes a pressure/temperature sensor 58 that measures fluid pressure within the purger 28. The pressure/temperature sensor 58 is configured to measure the pressure and temperature conditions inside the purger 28. The pressure/temperature sensor 58 may be a singular sensor or two separate sensors accessed through a single port, such as tap port 60. The pressure/temperature sensor 58 may include an aperture 62. The aperture 62 may provide a vent for the foul gas. Alternatively, the aperture 62 may provide a mounting point for a temperature probe that extends into the upper chamber 42, as part of the pressure/temperature sensor 58. In such an arrangement, the foul gas may be vented through a support tube 52b of the float 52.

The control unit 54 is configured to determine an estimated content of gaseous refrigerant within the foul gas, and thus an estimated refrigerant loss value when the foul gas content is vented from the purger 28. The control unit 54 includes an algorithm, represented by the flow chart 200 of FIG. 4. The algorithm includes at least one refrigerant look up table having pressure and temperature relationships of the specific refrigerant determined over a temperature range. The temperature range of the lookup table is associated with the operating characteristics of the specific refrigerant. For example, data for an R-11 or R-717 (ammonia) refrigerant may be in about −20° F. to about 80° F. while an R-50 (methane) refrigerant may be in a range of about −280° F. to about −160° F. The lookup tables for one refrigerant may be applicable to another refrigerant that has properties and characteristics that are similar. Thus, lookup tables may be provided for a chemical grouping of similar refrigerants or for range of refrigerants based on temperature and system operating pressures. The lookup tables further include information related to the specific refrigerant material properties and system operating properties such as, for example, system operating pressure, refrigerant and air density as a function of temperature, and volumetric and weight ratios of refrigerant to gas as a function of temperature. In addition, the algorithm is programmed with the purger 28 size, upper and lower chamber size and volume capacity, venting and input orifice sizes, outside pressure and temperature, and purge time.

Referring now to FIG. 3, there is illustrated another embodiment of a purger, shown generally at 100, for use with a purger monitoring device having a control unit similar to control unit 54. The purger 100 includes an upper chamber 102 and a lower chamber 104. The lower chamber 104 is configured as a trap having a check valve or regulating valve 106 in a condensing channel 108 between the upper and lower chambers 102 and 104. The trap 104 may be any type of suitable trap, such as an inverted bucket trap to improve fluid separation and the rate of foul gas flow to the upper chamber 102. The lower chamber 104 includes an inlet 110 and a lower chamber outlet port 112. A sight glass 114 is fluidly connected between the upper and lower chambers to provide a visual indication of the relative levels of liquid refrigerant and foul gas within the purger 100.

The upper chamber 102 is sealed by a head 116 having a plurality of ports that provide access to the interior of the upper chamber 102. A coil 118 is disposed within the upper chamber 102 and connected to a source of refrigerant at a coil inlet port 120 and a coil outlet port 122. The operating and refrigerant conditions within the coil 118 may be monitored by one or more sensors 124 that may provide feedback signals to the control unit 54 and may further operate or control a coil flow valve 126. A float 128 having a float sensor 130 is disposed within the upper chamber 102. A vent tube 132 may support the float 128 for movement within the upper chamber 102 and also provide a venting structure to purge foul gas contained within the purger 100. The vent tube 132 includes a purge regulating valve 134 that may be operated by the control unit 54. A pressure sensor 136 and a temperature sensor 138 are mounted on the head 116 and may extend into the upper chamber 102 to measure the temperature and pressure conditions within the purger 100. This arrangement provides a direct measurement of the refrigerant and foul gas parameters rather than reliance on other, more remote sensors used in the refrigeration system. Thus, incoming data accuracy is improved and more accurate refrigerant loss calculations can be made.

Referring now to FIG. 4, a method 200 of determining refrigerant purge loss will be described in conjunction with the operation of an algorithm 202 in a control unit, such as control unit 54. The purger 204, similar to purger 28 or purger 100, connects to an industrial refrigeration system, such as system 10, using the system pressures and fluid. The purger body is filled with high pressure/temperature fluid 206 from the refrigeration system. This high pressure/temperature fluid is then sub cooled through use of the internal cooling coil that is connected to a low pressure/temperature side of the refrigeration system. Warm refrigerant gas bubbles 208 are allowed to enter the sub cooled fluid in the purger body. This causes a portion of the warm gas bubbles 208 to condense leaving a portion of the bubble (the non-condensable gas) to accumulate at the inside the top of the purger.

The algorithm 202 signals the control unit to collect and store the information from the various sensors described above, such as real-time pressure, temperature, fluid level, and discharge duration. This data, along with either measured or known system operating parameters, such as piping impedance, purge orifice sizes, valve flow rates (based on type of valve and flow setting), and data from the specific refrigerant look-up table, is used by the algorithm to determine refrigeration loss during discharge to atmosphere. The calculated information is totaled and stored in the control unit 54, such as in a PLC memory. The sensors measuring fluid level 210 and temperature 212 inside the purger send a signal to the control unit, such as a PLC controller within the control unit. In addition, a pressure level 214, such as pressure P1, may be measured at a point external to the purger 204. Alternatively, the pressure 214 may be measured within the purger 204. In response to commands from the control unit and based on the sensor inputs, refrigerant look-up table data and system flow data 216, the algorithm and control unit command a solenoid valve, such as purge regulating valve 134, to open and discharge the accumulated gas, for example to atmosphere. The method includes the step of the control algorithm 202 determining whether a discharge event 222 has taken place. If no discharge has taken place, the sensor data and revised refrigerant and foul gas estimates, based in part on the look-up table data, are calculated and stored. If a discharge event 222 is taking place, the discharge time 218 is measured and used as an input to the algorithm to estimate a refrigerant loss output 220.

The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.

Claims

1. A refrigeration purger system comprising:

a purger unit having an upper chamber and a lower chamber in fluid communication with the upper chamber, and a head connected to the upper chamber;

at least one of a pressure sensor and a temperature sensor mounted on the head and configured to measure an associated state within the upper chamber; and

a control unit connected to the at least one pressure and temperature sensor, the control unit having an algorithm configured to control a purging cycle that purges air collected in the purger unit and determining an estimate of refrigerant loss during the purging cycle.

2. The refrigeration purger system of claim 1 wherein a float having a fluid level sensor is disposed within the upper chamber, the fluid level sensor measuring a refrigerant level and sending a fluid level measurement value to the control unit, the algorithm determining a volume of air in the purger and initiating the purging cycle based on the fluid level measurement and the measured state within the upper chamber.

3. The refrigeration purger system of claim 2 wherein the pressure and temperature sensors and the fluid level sensor are mounted to the upper chamber head, the algorithm estimating the volume of refrigerant using the temperature, pressure, and fluid level measurements within the purger and determining a volume of mixed air and refrigerant vented during the purging cycle.

4. The refrigeration purger system of claim 3 wherein the algorithm uses a purge length of time measurement to estimate the refrigerant loss during purging.

5. The refrigeration purger system of claim 1 wherein the algorithm includes at least one refrigerant lookup table having data associated with a refrigerant property as a function of temperature.

6. The refrigeration purger system of claim 5 wherein the lookup table includes data associated with at least one of a system operating pressure, a refrigerant density as a function of temperature, an air density as a function of temperature, a volumetric ratio of refrigerant to air as a function of temperature, and a weight ratio of refrigerant to air as a function of temperature.

7. The refrigeration purger system of claim 5 wherein the control unit transfers the refrigeration loss estimate to a computer.

8. The refrigeration purger system of claim 1 wherein a condensing channel fluidly connects the upper chamber to the lower chamber.

9. The refrigeration purger system of claim 8 wherein the lower chamber is configured as one of an inverted bucket trap and a ball float trap.

10. The refrigeration purger system of claim 1 wherein a coil is disposed within the upper chamber, the coil being in fluid communication with a refrigerant source such that the control unit maintains a condensing temperature within the upper chamber.

11. The refrigeration purger system of claim 10 wherein the control unit operates at least one purger operational valve to control the condensing temperature in response to the temperature within the purger.

12. The refrigeration purger system of claim 11 wherein the control unit operates at least one purge point valve to direct a flow of mixed refrigerant and air to the purger.

13. The refrigeration purger system of claim 12 wherein the algorithm includes at least one refrigerant lookup table having data associated with a refrigerant property as a function of temperature and pressure, the algorithm including data related to refrigeration system operating parameters.

14. The refrigeration purger system of claim 13 wherein the purger includes a fluid level sensor configured to send a signal to the control unit that is proportional to the refrigerant level in the purger, the algorithm determining a purge time based on one of a refrigeration level, the condensing temperature, and the pressure within the purger.

15. The refrigeration purger system of claim 14 wherein the refrigerant level sensor is a float level sensor.

16. A control unit for a refrigeration purger system, the control unit having an algorithm configured to control a purging cycle that purges air collected in the purger unit and determining an estimate of refrigerant loss during the purging cycle, the algorithm having a refrigerant lookup table that includes data associated with at least one of a refrigeration system operating pressure, a refrigerant density as a function of temperature, an air density as a function of temperature, a volumetric ratio of refrigerant to air as a function of temperature, and a weight ratio of refrigerant to air as a function of temperature, the algorithm further using a purge duration parameter, a purger temperature parameter, and a purger refrigerant fluid level to estimate refrigerant loss.

17. The control unit of claim 16 wherein the control unit is operative connected to at least one purger operational valve to control the temperature within the purger and operatively connected to at least one purge point valve to control a flow of a mixture of refrigerant and air to the purger in response to the purger refrigerant fluid level.

18. A refrigeration system comprising:

a compressor;

a condenser in fluid communication with the compressor;

an evaporator in fluid communication with the compressor; and

a refrigeration purger system comprising: a purger unit having an upper chamber and a lower chamber in fluid communication with the upper chamber, a head connects to the upper chamber; at least one of a pressure sensor and a temperature sensor mounted on the head and configured to measure an associated state within the upper chamber; and a control unit connected to the at least one pressure and temperature sensor, the control unit having an algorithm configured to control a purging cycle that purges air collected in the purger unit and determining an estimate of refrigerant loss during the purging cycle.

19. The refrigeration system of claim 18 wherein the algorithm includes at least one refrigerant lookup table having data associated with a refrigerant property as a function of temperature and pressure, the algorithm including data related to refrigeration system operating parameters.

20. The refrigeration system of claim 19 wherein a coil is disposed within the upper chamber, the coil being in fluid communication with the compressor such that the control unit maintains a condensing temperature within the upper chamber, the upper chamber further including a fluid level sensor configured to send a signal to the control unit that is proportional to a refrigerant level in the purger, the algorithm determining a purge time based on one of a refrigeration level, the condensing temperature, and the pressure within the purger.