COOLING SYSTEM UTILIZING A RECIPROCATING PISTON

Abstract

Cooling in the supersonic region of a compressible fluid is disclosed. The fluid is accelerated by a reciprocating piston to a velocity equal to or greater than the speed of sound in the fluid in an evaporator. No conventional mechanical pump is required to accelerate the fluid. A phase change of the fluid due to a pressure differential may be utilized to transfer heat from an element to be cooled.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to cooling via a supersonic fluid flow cycle. More specifically, the present invention is related to cooling systems that establish a supersonic cooling cycle using a reciprocating piston.

2. Description of the Related Art

Vapor compression systems are used in many cooling applications such as air conditioning and industrial refrigeration. A vapor compression system generally includes a compressor, a condenser, an expansion device, and an evaporator. In a prior art vapor compression system, a gas in a saturated vapor state is compressed to raise the temperature of that gas, the gas then being in a superheated vapor state. The compressed gas is then run through a condenser and turned into a liquid, and heat is rejected from the system. The condensed and liquefied gas is then taken through an expansion device, which drops the pressure and the corresponding temperature. The resulting refrigerant is then boiled in an evaporator, with the refrigerant absorbing heat. The saturated vapor is then returned to the compressor.

FIG. 1 illustrates a vapor compression system 100 as might be found in the prior art. In the prior art vapor compression system 100 of FIG. 1, compressor 110 compresses the gas to (approximately) 238 pounds per square inch (PSI) and a temperature of 190° F. Condenser 120 then liquefies the heated and compressed gas to (approximately) 220 PSI and 117° F. The gas that was liquefied by the condenser 120 is then passed through the expansion valve 130 of FIG. 1. By passing the liquefied gas through expansion valve 130, the pressure is dropped to (approximately) 20 PSI.

A corresponding drop in temperature accompanies the drop in pressure, which is reflected as a temperature drop to (approximately) 34° F. in FIG. 1. The refrigerant that results from dropping the pressure and temperature at the expansion value 130 is boiled at evaporator 140. Through boiling of the refrigerant by evaporator 140, a low temperature vapor results. The vapor is illustrated in FIG. 1 as having a temperature of (approximately) 39° F. and a corresponding pressure of 20 PSI.

The cycle carried out by the system 100 of FIG. 1 is an example of a vapor compression cycle. Such a cycle generally results in a coefficient of performance (COP) between 2.4 and 3.5. The COP, as illustrated in FIG. 1, is the evaporator cooling power or capacity divided by compressor power. It should be noted that the temperature and PSI references that are shown in FIG. 1 are exemplary and are for the purpose of illustration only.

FIG. 2 illustrates the performance that might be expected of a vapor compression system similar to that illustrated in FIG. 1. The COP illustrated in FIG. 2 corresponds to a typical home or automotive vapor compression system operating at an ambient temperature of (approximately) 90° F. The COP shown in FIG. 2 corresponds to a vapor compression system utilizing a fixed orifice tube system.

A system like that illustrated in FIG. 1 and FIG. 2 typically operates at an efficiency rate or COP that is far below that of system potential. To compress gas in a conventional vapor compression system like that illustrated in FIG. 1 (system 100) typically takes 1.75-2.50 kilowatts for every 5 kilowatts of cooling power. This exchange rate is less than optimal and directly correlates to the rise in pressure times the volumetric flow rate. Degraded performance is similarly and ultimately related to performance (or lack thereof) by the compressor 110.

Haloalkane refrigerants such as tetrafluoroethane (CH₂FCF₃) are inert gases that are commonly used as refrigerants in refrigerators and automobile air conditioners. Tetrafluoroethane has also been used to cool over-clocked computers. These gases are referred to as R-134 gases. The volume of an R-134 gas can be 600-1000 times greater than its corresponding liquid form. This multiplier shows that the theoretical efficiency of a system utilizing an R-134 gas is much higher than is currently being realized, and evidences the need for an improved cooling system that more fully recognizes system potential and overcomes technical barriers related to compressor performance.

In light of the theoretical efficiencies of systems using haloalkanes or other fluids, there is a need in the art for an improved cooling system that more fully recognizes system potential and overcomes technical barriers related to compressor performance. There is a further need for a cooling system that operates without the use of a conventional mechanical pump.

SUMMARY OF THE CLAIMED INVENTION

A first claimed embodiment is for a cooling system. The system includes a fluid flow path with a converging/diverging nozzle positioned therein. A reciprocating piston is positioned in the converging/diverging nozzle, and a driving mechanism is coupled to the reciprocating piston to impart linear motion to the reciprocating piston. The motion of the reciprocating piston accelerates a fluid in the fluid flow path so that the fluid flows in the critical flow regime. The fluid undergoes a pressure change so that the temperature of the fluid is reduced, thereby allowing heat to be exchanged with an element to be cooled.

A supersonic cooling method is also claimed. The method includes driving a reciprocating piston positioned within a converging/diverging nozzle to impart linear motion to the piston. The motion of the piston accelerates the fluid to a velocity equal to or greater than the speed of sound in the fluid. The acceleration also creates a low pressure region in which the fluid undergoes a phase change and a decrease in temperature. Heat may be exchanged either directly though the walls of the converging/diverging nozzle or via a heat exchange mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vapor compression cooling system as may be found in the prior art.

FIG. 2 is a pressure-enthalpy graph for a vapor compression cooling system like that illustrated in FIG. 1.

FIG. 3 is a sectional view of an exemplary supersonic cooling unit utilizing a reciprocating piston.

FIG. 4 is a pressure-enthalpy graph for a supersonic cooling system as described herein.

FIG. 5 illustrates a method of supersonic cooling utilizing a reciprocating piston.

DETAILED DESCRIPTION

Embodiments of the present invention implement a supersonic cooling cycle that increases efficiency as compared to prior art cooling systems. A system utilizing the present invention may operate at a COP of 2 or greater, 3 or greater, 4 or greater, 5 or greater, 6 or greater, 7 or greater, 8 or greater, 9 or greater, 10 or greater, 20 or greater, or 50 or greater. Embodiments of the present invention do not require a compressor or a conventional mechanical pump to operate. In place of these components is an electric motor or other driving mechanism that imparts a driving force. The elimination of the need for a conventional mechanical pump is beneficial in that the supersonic cooling system includes cavitation as part of the cooling cycle. Since cavitation is typically detrimental to the operation of a conventional mechanical pump, the elimination of the conventional mechanical pump benefits the operation of the system.

Part of the increase in COP for systems utilizing the supersonic cooling cycle with a reciprocating piston is due to the fact that such systems do not need to compress a gas as otherwise occurs at compressor 110 in a prior art vapor compression system 100 like the one shown in FIG. 1. A supersonic cooling system 300, as illustrated in FIG. 3, operates by accelerating a working liquid, which may be water, through a novel with a converging and diverging configuration (a converging/diverging nozzle) 305.

A ‘converging/diverging’ configuration is generally representative of a nozzle design that includes an inlet, throat, and exit with a continuous flow path in fluid communication with each section. The inlet section receives a fluid, which is ultimately expeller at the exit portion. The diameter of the flow path decreases (i.e., converges) from the inlet portion to the throat portion of the nozzle. The nozzle then expands (i.e., diverges) from the throat to the exit portion of the nozzle. The converging/diverging nozzle 305 may be advantageously positioned in the vertical orientation shown in FIG. 3.

Because the supersonic cooling system 300 utilizes the converging/diverging nozzle 305 to generate a cooling effect as further described herein, the system 300 does not require the use of a condenser 120 as does the prior art compression system 100 of FIG. 1. The system 300 utilizes a working fluid that flows through a fluid flow path. The fluid flow path includes the converging/diverging nozzle 305. The working fluid may be any suitable refrigerant chosen by a user of the system 300. The system 300 may utilize water as the working fluid to eliminate green house gas emission considerations.

The working fluid is accelerated in the converging/diverging nozzle 305 by a reciprocating piston 310. The reciprocating piston 310 is coupled to a driving mechanism that imparts reciprocating linear motion to the piston. The driving mechanism may be a crankshaft, a linear actuator, or a cam system. The driving mechanism may be powered by any suitable driving device, such as an electric motor.

The velocity of the linear travel and the size of the reciprocating piston 310 are selected based on factors unique to a particular installation. The factors may include, but are not limited to, the working fluid utilized in the installation and the amount of cooling power desired. The construction of the reciprocating piston 310 may be designed to ensure that the reciprocating piston 310 imparts sufficient suction on the working fluid to accelerate the fluid to at least the speed of sound in the fluid.

Fluid flow into and out of the converging/diverging nozzle 305 may be controlled by a pair of check valves. A first check valve 315 is positioned upstream of an inlet 320 of the converging/diverging nozzle 305. The first check valve 315 ensures that working fluid only enters the inlet 320 of the converging/diverging nozzle 305 with limited or no backflow. A second check valve 325 is positioned downstream of an outlet 330 of the converging/diverging nozzle 305. The second check valve 325 ensures that working fluid flows only outward through the outlet 330 with backflow eliminated or greatly limited. The outlet 330 may be installed at a position just below the lowest point of travel of the reciprocating piston 310.

As an alternative, the reciprocating piston 310 may be configured to impart a positive pressure on the working fluid to accelerate the fluid to a velocity greater than or equal to the speed of sound in the fluid. In such a case, the reciprocating piston may be disposed at the inlet 320 or upstream from the inlet 320 of the converging/diverging nozzle 305. In a first cycle the piston 310 may draw fluid into the inlet 320, and in a subsequent second cycle the piston 310 may drive the fluid through the converging/diverging nozzle 305. The positive pressure may be provided by the decreasing volume between the piston and the inlet 320 during the second cycle.

The working fluid may be introduced to the converging/diverging nozzle 305 from an accumulator 335 coupled to the inlet 320 of the converging/diverging nozzle 305. The accumulator 335 may be utilized to regulate the flow of the working fluid, and to reduce fluctuations in the flow. A pressure set valve 340 may be coupled to the accumulator to control the pressure of the working fluid in the accumulator 335, thereby controlling the pressure of the fluid entering the fluid flow path. The pressure in the accumulator 335 may be set to a pressure just above the vapor pressure of the working fluid.

The working fluid may contain certain non-condensable components such as air. To remove the non-condensable components, a trap 335 may be coupled to the fluid flow path. The trap 335 may be equipped with a bleed valve 355 to expel the non-condensable components from the fluid flow path. The trap 335 may be positioned at the highest point of the fluid flow path to increase its efficiency. The cooling system 300 may need to be periodically drained and/or recharged with working fluid. To this end, a charge/drain valve 345 is coupled to the fluid flow path.

The cooling cycle created by the system 300 is initiated with the reciprocating piston 310 at its lowest position in a cylindrical portion of the converging/diverging nozzle 305. The cooling cycle begins with an upward movement of the reciprocating piston 310 imparted by the driving mechanism. As the reciprocating piston 310 moves upward, working fluid may be drawn from the accumulator 335 through the first check valve 315. The working fluid is accelerated as it flows through the converging/diverging nozzle 305 and reaches its maximum velocity in the throat of the nozzle 305. At this point, the velocity of the working fluid will be equal to or greater than the speed of sound in the working fluid.

As the fluid is accelerated through the converging/diverging nozzle 305, the static pressure of the fluid at the throat drops below the vapor pressure of the fluid. Cavitation occurs so that the working fluid in at least a part of the converging/diverging nozzle 305 is a dual phase fluid including the liquid phase and the vapor phase. The vapor phase mixing with the liquid working fluid reduces the speed of sound in the working fluid. As the working fluid continues to flow through the converging/diverging nozzle 305, still more vapor is formed through evaporation (boiling) of the fluid caused by supersonic flow in the expanding area of the converging/diverging nozzle 305. These factors may allow the formation of a compression wave that is utilized in the acceleration of the working fluid.

Because the working fluid flows in at least a portion of the converging/diverging nozzle 305 at a velocity equal to or greater than the speed of sound in the fluid, the cooling system 300 operates in the critical flow regime of the working fluid. In this regime, the pressure of the fluid in the system 300 may remain almost constant and then ‘jump’ or ‘shock up’ to the ambient pressure as the cooling cycle is completed.

Because cooling system 300 accelerates the working fluid and creates a pressure differential through the linear movement of the reciprocating piston 310, cooling system 300 does not require the use of a conventional mechanical pump. The reduced amount of hardware required to operate the cooling system 300—there is no need for either a compressor or a conventional mechanical pump—gives rise to a greatly improved coefficient of performance (COP) for the system.

When the reciprocating piston 310 reaches the top of its stroke in the cylindrical portion of the converging/diverging nozzle 305, the movement of the piston stops, and acceleration of the fluid is also stopped. The vapor bubbles in the fluid continue to rise in the converging/diverging nozzle 305 until the bubbles reach the lower surface of the reciprocating piston 310. The static pressure in the converging/diverging nozzle 305 increases until the bubbles collapse and the fluid flows out of the converging/diverging nozzle 305 through the outlet 330.

During the acceleration phase of the cooling cycle, the phase change and pressure differential in the converging/diverging nozzle 305 generate the cooling effect for the supersonic cooling system 300. The working fluid absorbs heat from the walls of the converging/diverging nozzle 305. Heat transfer to an object to be cooled may be facilitated by a heat exchanging mechanism 350. The heat exchanging mechanism 350 may include fins on the surface of the converging/diverging nozzle 305. A circulating fluid heated by the object to be cooled may be thermally coupled to the heat exchanging mechanism 350. FIG. 4 illustrates a pressure-enthalpy graph for a supersonic cooling system operating in accordance with FIG. 3.

In the supersonic cooling system 300, the working fluid travels through the fluid flow path to generate a cooling effect via the method delineated in FIG. 5. In a step 510, the motive force for moving the fluid is provided by linear motion of the reciprocating piston 310. In a step 520, the working fluid is drawn through inlet 320 into the converging/diverging nozzle 305 at least in part by suction created by the linear motion of the reciprocating piston 310.

In a further step 530, the fluid is accelerated through the converging/diverging nozzle 305. During the acceleration step 530, a cavitation effect is created in the converging/diverging nozzle 305. As the working fluid flows through the converging/diverging nozzle 305, the suction generated by the linear motion of the reciprocating piston 310 accelerates the working fluid. A decrease in pressure and a phase change in the working fluid result in a lowered temperature of the fluid to create a cooling effect in step 540.

Critical flow rate, which is the maximum flow rate that can be attained by a compressible fluid as that fluid passes from a high pressure region to a low pressure region (i.e., the critical flow regime), allows for a compression wave to be established and utilized in the critical flow regime established in the converging/diverging nozzle 305. Critical flow occurs when the velocity of the fluid is greater than or equal to the speed of sound in the fluid. In critical flow, the pressure in the converging/diverging nozzle 305 will not be influenced by the exit pressure. In step 550, the working fluid may ‘shock up’ to the ambient conditions as the fluid exits the converging/diverging nozzle 305.

The pressure change of the fluid in the system 300 may include a range of approximately 20 PSI in the low pressure region to 100 PSI in the high pressure region. In some instances, the pressure may be increased to more than 100 PSI or more than 150 PSI. In some embodiments, the low pressure region may be at a pressure of less than 1 PSI. For installations using water as the working fluid, an initial pressure of the fluid may be 30 PSI. Depending on the characteristics of any given application, the pressure change range may vary from that described immediately above.

The cooling effect of the system 300 may be realized in an object to be cooled by putting the object in direct contact with the converging/diverging nozzle 305. The transfer of heat from the object to be cooled into the system 300 may also be accomplished in an optional step 560. In optional step 560, the working fluid is thermally coupled to a heat exchange mechanism 350. The heat exchange mechanism 350 may be thermally coupled to a heated circulating fluid from the object to be cooled by the supersonic cooling system 300.

While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. The descriptions are not intended to limit the scope of the invention to the particular forms set forth herein. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments. It should be understood that the above description is illustrative and not restrictive. To the contrary, the present descriptions are intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims and otherwise appreciated by one of ordinary skill in the art. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.

Claims

1. A cooling system, the system comprising:

a fluid flow path including a converging and diverging nozzle; and

a reciprocating piston positioned within the converging and diverging nozzle, wherein linear motion associated with the reciprocating piston accelerates a fluid in the fluid flow path such that the fluid flows in the critical flow regime and undergoes a pressure change while traversing the flow path at the converging and diverging nozzle, the pressure change reducing the temperature of the fluid.

2. The system of claim 1, further comprising a driving mechanism coupled to the reciprocating piston to impart linear motion to the reciprocating piston.

3. The system of claim 1, wherein the acceleration of the fluid flow by the reciprocating piston generates a compression wave that influences the temperature of the fluid.

4. The system of claim 1, wherein the linear motion of the reciprocating piston generates suction, the suction inducing cavitation in the fluid.

5. The system of claim 1, wherein the converging and diverging nozzle is thermally coupled to an element to be cooled by the fluid.

6. The system of claim 1, wherein the converging and diverging nozzle is thermally coupled to a heat exchange mechanism.

7. The system of claim 1, wherein the fluid pressure change induced by the reciprocating piston is from approximately 150 PSI to approximately 10 PSI.

8. A cooling method, the method comprising:

driving a reciprocating piston within a converging and diverging nozzle to impart linear motion, wherein the linear motion of the piston accelerates fluid flowing through the converging and diverging nozzle to a velocity equal to or greater than the speed of sound in the fluid; and

exchanging heat introduced into the fluid flow path via a cooling effect created during a phase change of the fluid, the phase change induced through the acceleration of the fluid through the converging and diverging nozzle by the reciprocating piston.

9. The method of claim 8, wherein a compression wave is created in the fluid as the fluid passes from a high pressure region to a low pressure region of the converging and diverging nozzle.

10. The method of claim 9, further comprising creating cavitation, the cavitation created as a result of the linear motion of the reciprocating piston, and wherein the cavitation assists in formation of the compression wave.

11. The method of claim 8, wherein the exchange of heat occurs at a heat exchanging mechanism thermally coupled to the converging/diverging nozzle.

12. The method of claim 8, wherein the linear motion of the reciprocating piston creates suction that draws the fluid through the converging/diverging nozzle.

13. The method of claim 8, further comprising moving the fluid from a high pressure region to the low pressure region as the result of a suction effect generated by the reciprocating piston.

14. The method of claim 8, wherein the phase change corresponds to a pressure change of the fluid.

15. The method of claim 14, wherein the pressure change of the fluid occurs within a range of approximately 0.5 PSI to approximately 175 PSI.

16. The method of claim 14, wherein the pressure change of the fluid involves a change to a pressure greater than or equal to 200 PSI.

17. The method of claim 14, wherein the pressure change of the fluid involves a change to a pressure less than or equal to 10 PSI.

18. The method of claim 9, wherein the fluid shocks up to an elevated pressure as the fluid exits the low pressure region.

19. A cooling system, the system comprising:

a fluid flow path including a converging and diverging nozzle; and

a reciprocating piston in fluid communication with the converging and diverging nozzle, the reciprocating piston accelerating a fluid in the fluid flow path to a velocity greater than or equal to the speed of sound in the fluid by imparting motion to the fluid such that the fluid flows in the critical flow regime and undergoes a pressure change while traversing the flow path at the converging and diverging nozzle, the pressure change reducing the temperature of the fluid.

20. The cooling system of claim 19, wherein the reciprocating piston is upstream from a fluid inlet of the converging and diverging nozzle.