Claims
- 1. In a method of operating a vapor compression refrigeration system wherein an evaporator removes heat from a medium which is circulated through said evaporator in heat exchange relation with an evaporator coil in said evaporator, said coil including an inlet which is in flow communication with an expansion device and an outlet which is in flow communication with a compressor,
the improvement comprising:
supplying a mixture of refrigerant vapor and liquid at a given mass flow rate and at a given volumetric flow velocity to the evaporator coil inlet, said mixture including a substantial vapor portion, substantially all of said liquid being converted to vapor as said mixture passes through said evaporator coil, said given linear velocity and the relative amounts of vapor and liquid present in said mixture at said evaporator coil inlet being sufficient to provide efficient heat transfer between said mixture and said medium along substantially the entire length of said coil, whereby the build-up of frost on said evaporator coil is substantially reduced enabling said vapor compression refrigeration system to be operated without requiring a defrosting cycle over a substantially increased number of refrigeration cycles as compared to a conventional vapor compression refrigeration system operating at the same cooling load and evaporating temperature conditions.
- 2. The method of claim 1 wherein approximately {fraction (1/2)}% of the mass of refrigerant liquid/vapor mixture is in a liquid state at said outlet of said evaporator coil during the portion of each refrigeration cycle when said expansion device is actively supplying said mixture of said refrigerant vapor and liquid to said evaporating coil inlet.
- 3. The method of claim 1 wherein the volumetric velocity of said refrigerant vapor and liquid mixture at said evaporator coil inlet is at least 10% greater than the volumetric velocity of refrigerant fluid feed to an evaporator inlet in a conventional vapor compression refrigeration system of the type wherein an expansion device is located in close proximity to inlet of the evaporator operating at the same cooling load and which utilizes an evaporator coil of the same size and has an equal flow rate for the medium circulated through said evaporator.
- 4. The method of claim 3 wherein the volumetric velocity of said refrigerant vapor and liquid mixture at said evaporator coil inlet is from approximately 10% to 25% greater than the volumetric velocity of the refrigerant feed to the evaporator inlet of said conventional vapor compression refrigeration system.
- 5. The method of claim 3 wherein the volumetric velocity of said refrigerant vapor and liquid mixture at said evaporator coil inlet is approximately 18% greater than the volumetric velocity of the refrigerant feed to the evaporator inlet of said conventional vapor compression refrigeration system.
- 6. The method of claim 1 wherein the mass flow rate of said refrigerant vapor and liquid mixture at said evaporator coil inlet is at least 5% greater than the mass flow rate of refrigerant fluid feed to an evaporator in a conventional vapor compression refrigeration system of the type wherein an expansion device is located in close proximity to inlet of the evaporator operating at the same cooling load which utilizes an evaporator coil of the same size and has an equal flow rate for the medium being passed through said evaporator.
- 7. The method of claim 6 wherein the mass flow rate of said refrigerant vapor and liquid mixture at said evaporator coil inlet is from approximately 5 to 20% greater than the mass flow rate of refrigerant feed to the evaporator inlet of said conventional vapor compression refrigeration system.
- 8. The method of claim 6 wherein the mass flow rate of said refrigerant vapor and liquid mixture at said evaporator coil inlet is approximately 12% greater than the mass flow rate of the refrigerant feed to the evaporator inlet of said conventional vapor compression refrigeration system.
- 9. In a method of operating a vapor compression refrigeration system wherein a medium having a given relative humidity is withdrawn from a refrigerated compartment, circulated through an evaporator in heat exchange relation with an evaporator coil, and returned to said compartment, said evaporating coil including an inlet which is in flow communication with a refrigerant expansion device and an outlet which is in flow communication with a compressor, the improvement comprising, supplying a mixture of refrigerant vapor and liquid to the evaporator coil inlet, said mixture including a substantial vapor portion, substantially all of said liquid being converted to vapor as said mixture passes through said evaporator coil, said mixture being supplied to the evaporator coil at a given linear velocity, measured at the evaporator inlet, and the relative amounts of liquid and vapor present in said mixture at said evaporator coil inlet being sufficient to provide efficient heat transfer between said mixture and said air medium along substantially the entire length of said coil, the differential temperature between said coil and said air medium adjacent at least the inlet to said evaporator during at least a portion of a refrigeration cycle being sufficient to substantially maintain said given relative humidity in said medium and thereby substantially eliminate the build-up of frost along substantially the entire length of said evaporator coil.
- 10. The method of claim 9 wherein said medium is air.
- 11. The method of claim 10 wherein said air medium is circulated in counter-current relation to the flow of refrigerant vapor and liquid particles in said evaporating coil wherein the temperature of the air being supplied to said evaporator from said refrigerated compartment is equal to or lower than the temperature of the evaporating coil inlet during at least the portion of a refrigeration cycle.
- 12. The method of claim 10 wherein said given linear velocity is at least 400 feet per minute.
- 13. The method of claim 10 wherein said linear velocity is at least from 400 to 750 feet per minute.
- 14. A vapor compression refrigeration system comprising:
a compressor for increasing the pressure and temperature of a refrigerant vapor, said compressor having an inlet and an outlet; a condenser having an inlet in flow communication with the outlet of said compressor for liquefying pressurized refrigerant vapor received from said compressor; an expansion device having a first inlet which, during a cooling mode of operation of said refrigeration system, is in flow communication with an outlet of said condenser for receiving liquid refrigerant from said condenser and vaporizing a substantial portion of the same; an evaporator including an evaporating coil having an inlet and an outlet, said evaporating coil being in heat exchange relation with an air medium along substantially the entire length of said coil; an evaporator feed line providing flow communication of said expansion device with said evaporating coil inlet; a suction line providing flow communication of said evaporating coil outlet with said compressor inlet; said expansion device and said evaporator feed line, during a cooling mode of operation of said vapor compression refrigeration system, being sized to provide said evaporating coil inlet with a refrigerant liquid and vapor mixture that includes a substantial vapor portion, said evaporating coil being sized to provide said refrigerant liquid and vapor mixture with a linear velocity sufficient to provide efficient heat transfer along substantially the entire length of said coil; and, a sensor in said suction line operatively associated with said expansion device for regulating the flow of refrigerant from the inlet of said expansion device to the inlet of said evaporating chamber.
- 15. The vapor compression refrigeration system of claim 14 wherein said expansion device is a multi-functional valve which includes a second inlet, said second inlet being in flow communication with the outlet of said compressor when said refrigeration system is in a defrost mode of operation during which the pressurized refrigerant vapor which is discharged from said compressor outlet is supplied to said multi-functional valve, through said evaporator feed line and into the inlet of said evaporator coil.
- 16. The vapor compression refrigeration system of claim 15 wherein said multi-functional valve includes a second inlet, a first passageway coupled to the first inlet, said first passageway being gated by a first valve, a second passageway coupled to the second inlet, the second passageway being gated by a second valve, and a metering valve positioned in the first passageway which is activated by the sensor in said suction line.
- 17. The vapor compression refrigeration system of claim 16 wherein each of said first and second valves is a solenoid valve.
- 18. The vapor compression refrigeration system of claim 14 wherein said sensor is temperature activated.
- 19. The vapor compression refrigeration system of claim 14, further comprising a unit enclosure and a refrigeration case, wherein the compressor, evaporator and expansion device are located within the unit enclosure and wherein the evaporator is located within the refrigeration case.
- 20. The vapor compression refrigeration system of claim 14 wherein said expansion device comprises a thermostatic expansion valve.
- 21. The vapor compression refrigeration system of claim 14 wherein said expansion device comprises an automatic expansion valve.
- 22. The vapor compression refrigeration system of claim 14 wherein said expansion device comprises a capillary tube.
- 23. The vapor compression refrigeration system of claim 14 wherein said expansion device is closer to the outlet of said condenser than to the inlet to said evaporating coil.
- 24. The vapor compression refrigeration system of claim 14 wherein said expansion device is adjacent the outlet of said condenser.
- 25. A vapor compression refrigeration system comprising:
a compressor for increasing the pressure and temperature of a refrigerant vapor, said compressor having an inlet and an outlet; a condenser having an inlet in flow communication with the outlet of said compressor for liquefying pressurized refrigerant vapor received from said compressor; an expansion device which, during a cooling mode of operation of said refrigeration system, is in flow communication with an outlet of said condenser for receiving liquid refrigerant from said condenser and vaporizing a substantial portion of the same, said expansion device including a thermostatic expansion valve having an inlet and an outlet, the outlet of said thermostatic expansion valve being in series flow communication with an inlet to a multifunctional valve which includes an expansion chamber whereby liquid refrigerant supplied to said expansion device undergoes a two-stage expansion; an evaporator including an evaporating coil having an inlet and an outlet, said evaporating coil being in a heat exchange relation with an air medium along substantially the entire length of said coil; an evaporator feed line providing flow communication of said expansion device with said evaporating coil inlet; a suction line providing flow communication of said evaporating coil outlet with said compressor inlet; said expansion device and said evaporator feed line, during a cooling mode of operation of said vapor compression refrigeration system, being sized to provide said evaporating coil inlet with a refrigerant liquid and vapor mixture that includes a substantial vapor portion, said evaporating coil being sized to provide said refrigerant liquid and vapor mixture with a linear velocity sufficient to provide efficient heat transfer along substantially the entire length of said coil; and, a sensor in said suction line operatively associated with said expansion device for regulating the flow of refrigerant from the inlet of said expansion device to the inlet of said evaporating chamber.
- 26. In a method of operating a vapor compression refrigeration system wherein an evaporator removes heat from a air medium which is passing through said evaporator in heat exchange relation with an evaporator coil in said evaporator, said coil including an inlet which is in flow communication with an expansion device, said evaporator coil also having an outlet which is in flow communication with a compressor, the improvement comprising:
providing said expansion device with an expansion valve having an outlet which communicates with an inlet to a multi-functional valve which includes an expansion chamber; supplying a liquid refrigerant to said expansion device where it undergoes a two-stage series expansion to produce a mixture of refrigerant vapor and liquid which is supplied at a given mass flow rate and at a given linear velocity to the evaporator coil inlet, said mixture including a substantial vapor portion, substantially all of said liquid being converted to vapor as said mixture passes through said evaporator coil, said given linear velocity and the relative amounts of vapor and liquid present in said mixture at said evaporator coil inlet being sufficient to provide efficient heat transfer between said mixture and said medium along substantially the entire length of said coil, whereby the build-up of frost on said evaporator coil is substantially reduced enabling said vapor compression refrigeration system to be operated without requiring a defrosting cycle over a substantially increased number of refrigeration cycles as compared to a conventional vapor compression refrigeration system operating at the same cooling load and evaporating temperature conditions.
- 27. The method of claim 26 wherein said medium is air.
- 28. The method of claim 27 wherein the mass flow rate of said refrigerant vapor and liquid mixture at said evaporator coil inlet is at least 5% greater than the mass flow rate of refrigerant fluid feed to an evaporator in a conventional vapor compression refrigeration system of the type wherein an expansion device is located in close proximity to inlet of the evaporator operating at the same cooling load which utilizes an evaporator coil of the same size and has an equal flow rate for the medium being passed through said evaporator.
- 29. The method of claim 27 wherein the mass flow rate of said refrigerant vapor and liquid mixture at said evaporator coil inlet is from approximately 5 to 20% greater than the mass flow rate of refrigerant feed to the evaporator inlet of said conventional vapor compression refrigeration system.
- 30. The method of claim 27 wherein the mass flow rate of said refrigerant vapor and liquid mixture at said evaporator coil inlet is approximately 12% greater than the mass flow rate of the refrigerant feed to the evaporator inlet of said conventional vapor compression refrigeration system.
- 31. The method of claim 27 wherein said given linear velocity is at least 400 feet per minute.
- 32. The method of claim 31 wherein said linear velocity is at least from 400 to 750 feet per minute.
- 33. The method of claim 27 where one stage in said two-stage series expansion is modulated.
- 34. The method of claim 27 wherein the first stage in said two-stage series expansion is modulated.
- 35. The method of claim 27 wherein some liquid is present in said mixture at said outlet of said evaporator coil during the portion of each of said refrigeration cycles when said compressor is operating.
- 36. In a method of operating a commercial or industrial vapor compression refrigeration system which includes a compressor, a condenser, an expansion device in series flow communication with each other via a refrigerant circuit and wherein the compressor and condenser are remote from said evaporator and said expansion device is closer to said condenser than to said evaporator, said evaporator being supplied with a mixture of refrigerant vapor and liquid, the improvement comprising:
controlling the flow rate of said refrigerant vapor and liquid mixture in a substantial portion of the refrigerant circuit between said condenser and evaporator so that it has a linear velocity which is at least 20% greater than the linear velocity of a refrigerant feed in a substantial portion of a refrigeration circuit between a condenser and evaporator in a conventional commercial or industrial vapor compression refrigeration system operating at the same cooling load and evaporating temperature conditions.
- 37. The method of claim 36 wherein said expansion device is in flow communication with an inlet to said evaporator via an evaporator feed line and so the linear velocity of said refrigerant vapor and liquid mixture in a substantial portion of the length of said evaporator feed line is at least 400 feet per minute.
- 38. The method of claim 37 wherein the linear velocity of said refrigerant vapor and liquid mixture in a substantial portion of said evaporator feed line is from approximately 400 to 750 feet per minute.
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of my copending application Ser. No. 09/228,696, filed Jan. 12, 1999.
Continuations (1)
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Number |
Date |
Country |
Parent |
09443071 |
Nov 1999 |
US |
Child |
10304878 |
Nov 2002 |
US |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
09228696 |
Jan 1999 |
US |
Child |
09443071 |
Nov 1999 |
US |