MXPA99007052A - Cooling system with defrost by hot gas - Google Patents

Abstract

The present invention relates to a refrigeration system having a refrigeration cycle and an evaporator defrosting cycle, comprising: a compressor having a low pressure port and a high pressure port, a condenser having a gas port and a liquid port, and a coil extending between them, a temperature detector that detects the refrigerant temperature, said detector is operatively coupled with the condenser coil in an intermediate location of the gas port of the condenser and the liquid port of the condenser, to detect the temperature of the refrigerant passing through the condenser coil in said location, an evaporator having a liquid port and a gas port, an expansion valve arranged in a passage that communicates refrigerant from the liquid port from the condenser to the evaporator liquid port during the refrigeration cycle, a defrost valve It is arranged in a passage that communicates refrigerant from the liquid port of the evaporator to the liquid port of the condenser during the defrosting cycle, and an inversion valve to direct refrigerant flow from the high pressure port of the compressor to the port. condenser gas during the refrigeration cycle, the reversing valve directs flow from the evaporator gas port to the compressor's low pressure port during the refrigeration cycle, the reversing valve directs coolant flow from the high pressure port from the compressor to the evaporation gas port during the defrosting cycle, the reversing valve directs flow from the condenser gas port to the compressor's low pressure port during the defrost cycle, said defrost valve responding to said detector, and said detector being positioned to ensure that it is supplied only steam to the compressor during the defrost cycle

Description

REFRIGERATION SYSTEM WITH DISCHARGE AMIE TO CABIENTE GAS FIELD OF THE INVENTION The present invention relates generally to a cooling system and, in particular, to a cooling system with a hot gas defrost circuit having an inversion valve for periodic defrosting. BACKGROUND OF THE INVENTION Various techniques for thawing refrigeration systems are known. For example, a common method for defrosting a refrigeration system is to stop the refrigeration cycle and activate heaters placed near the evaporator coils. These heaters defrost and thaw the evaporator coil. This method, however, consumes a lot of time and often causes unwanted heating of the refrigerated area. Another method for defrosting cooling systems is to reverse the refrigeration cycle. When the refrigeration cycle is reversed, the hot refrigerant vapor from the compressor is directed into the evaporator outlet, through the evaporator, into the condenser outlet, through the condenser, and back into the compressor. A problem with this method is that often the temperature of the refrigerant entering the compressor is so low that some liquid is introduced into the compressor. This liquid can damage or destroy the compressor. In addition, the temperature of the refrigerant entering the evaporator is often too low for rapid or complete defrosting of the evaporator. Therefore, the defrost cycle may be time consuming or the evaporator may not be completely defrosted. A conventional refrigeration defroster system is shown in U.S. Patent No. 4,102,151 issued to Kramer, et al. The Kramer patent discloses a hot gas defroster system wherein the superheated refrigerant vapor from the compressor is directed to Through a tank full of water, the superheated refrigerant vapor heats the tank water to a high temperature, the hot coolant then passes through the evaporator to defrost the evaporator coil, the refrigerant leaving the evaporator is then directed to through the tank containing the hot water to reheat the refrigerant and ensure that all of it is in the form of vapor.The steam refrigerant then enters the compressor to complete the defrost cycle.This defroster system requires a system complex of tubes, valves and a large water tank.

Also shown in U.S. Patent No. 5,056,327, Lammert is granted a conventional refrigeration defroster system. The Lammert patent presents a defrosting system with hot gas in which, during the defrost cycle, a series of valves and tubes are used to direct the refrigerant through the compressor, evaporator, condenser and back to the compressor, thus using the condenser as reevaporator during the defrost cycle. The Lamert patent also presents a superheater in a defrost duct that receives refrigerant from the condenser outlet during the defrost cycle and supplies it to the compressor intake. In addition, the Lammert patent has a conduit, which is connected to the compressor outlet and the evaporator outlet, which is in a heat exchange relationship with the superheater in the defrost duct. The superheater allows the heat from the hot steam refrigerant discharged from the compressor to be used to heat the refrigerant supplied to the compressor outlet. This cooling de-icing system undesirably requires numerous valves, tubes and a superheater to "properly direct the refrigerant during the defrost cycle." Another conventional refrigeration system is presented in the United States Patent. Number 5, 050,400 also granted to Lammert. This Lammert patent presents a cooling system that includes a series of interconnected valves and liquid conduits that allow the refrigerant to flow in sequence from the compressor to the evaporator and, through a defrost duct, to the condenser and back to the compressor during the defrost cycle. This system includes a combined superheater / condensing tube located in the defrost duct to be used during the defrost cycle. The combined superheater / condensing tube includes a socket for receiving refrigerant from the condenser during the refrigeration cycle, a first outlet for supplying refrigerant liquid to the evaporator during the refrigeration cycle, and a second outlet for supplying refrigerant vapor to the compressor during the cycle of defrost. During the defrost cycle, the system also uses a closed liquid conduit that uses hot steam refrigerant discharged from the compressor to heat the refrigerant entering the compressor. This closed liquid conduit ensures that all refrigerant that enters the compressor is in the form of vapor. Undesirably, this cooling defrost system requires a lot of tooling, including several tubes and valves, to manage the refrigerant appropriately during the defrost cycle. This cooling system also requires the use of a superheater / condensing tube which increases the complexity and cost of the system. SUMMARY OF THE INVENTION The present invention is an improved refrigeration system with a simplified hot gas defrost circuit that eliminates the complexities of conventional defrosting systems. In one aspect of the invention, the refrigeration system includes a compressor, a condenser, an evaporator, an expansion valve, a defrost valve and an inversion valve. During the refrigeration cycle, the reversing valve directs the flow of refrigerant from the compressor to the condenser, and the reversing valve directs the flow of refrigerant from the evaporator to the compressor. During the defrost cycle, the reversing valve directs the flow of refrigerant from the compressor to the evaporator and then to the condenser, and the reversing valve directs the flow of refrigerant from the condenser to the compressor. Advantageously, the present invention provides a refrigeration system with hot gas defrosting efficient in energy consumption and cost efficient, particularly in temperate and cold climates. In addition, the present invention eliminates the complex system of tubes and valves required in conventional defrosting systems. In another aspect of the invention, the refrigeration system includes a condensing tube disposed between the condenser and evaporator. During the refrigeration cycle, the refrigerant leaving the condenser passes the defrost valve and enters the condensing tube. The refrigerant then flows out of the condensing tube, through the expansion valve and into the evaporator. During the defrost cycle, the refrigerant flows from the condenser into the compressor and the refrigerant flows from the evaporator into the condensing tube. The refrigerant then flows out of the condensing tube, through the defrost valve and into the condenser to complete the defrost cycle. In still another aspect of the invention, the cooling system includes two reversing valves. During cooling, a first reversing valve directs the refrigerant discharged by the compressor into the condenser and a second reversing valve directs the condenser refrigerant inside the condensing tube. The second reversing valve also directs the refrigerant from the condensing tube into the evaporator.

During the defrosting cycle, the first injection valve directs the refrigerant discharged by the compressor into the evaporator and the second reversing valve directs the refrigerant from the evaporator into the condensing tube. The second reversing valve also directs the refrigerant from the condensing tube into the condenser. Advantageously, the two reversing valves eliminate the need for a second conduit connecting the evaporator and the condenser. Advantages and further applications of the present invention will become apparent to those skilled in the art from the detailed description of the preferred embodiments and the drawings referred to herein, the invention not being limited to any form of particular embodiment. . BRIEF DESCRIPTION OF THE DRAWINGS These and other features of the invention will now be described with reference to the drawings of the preferred embodiments, which are intended to illustrate and not to limit the invention, wherein: Figure 1A is a drawing schematic of an embodiment of the present invention of a refrigeration system with hot gas defrost, including a condensing tube and sub-refrigerant coils as part of a condenser; FIG. IB is another schematic drawing of an embodiment of the present invention of a hot gas defrosting refrigeration system, including a condensing tube and coils of the subcooler as part of a condenser; Figure 2A is a schematic drawing of an embodiment of the system shown in Figure 1A, showing a defrost cycle; Figure 2B is a schematic drawing of an embodiment of the system shown in Figure IB, showing a defrost cycle; Figure 3 is a schematic drawing of another embodiment of the present invention, including a condensing tube between the condenser and the evaporator, showing a refrigeration cycle; Figure 4 is a schematic drawing of another embodiment of the system shown in Figure 3, showing a defrost cycle; Figure 5 is a schematic drawing of a further embodiment of the present invention, which "includes a condensing tube with an inlet valve in its outlet, showing a refrigeration cycle; Figure 6 is a schematic drawing of the embodiment of the system shown in Figure 5, which shows a defrost cycle; Figure 7 is a flow chart of yet another embodiment of the present invention, including a variable speed controller for the condenser fan; - Figure 8 is an elongated schematic drawing of a portion of an embodiment of the present invention, showing a thermostatic expansion valve; Figure 9A is a partially schematic elongated diagram of the thermostatic expansion valve shown in Figure 8, showing the valve only in the flow of the purge gate; Figure 9B is a partially schematic elongated diagram of the thermostatic expansion valve shown in Figure 8, showing the valve normal operation; and Figure 9C is a partially schematic, elongated diagram of the thermostatic expansion valve shown in Figure 8, showing the valve in the down draft mode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Therefore, the following detailed description of the preferred embodiments of the present invention is not intended to limit the scope thereof.as claimed, but is only representative of the "presently preferred embodiments of the invention." As shown in Figures IA and IB, a hot gas defrosting cooling system 10 is configured in accordance with a form In this embodiment, the cooling system 10 includes a compressor 12, preferably a compressor of the conventional type with a low pressure intake gate 14 and a high pressure outlet gate 16. Compressor 12 may include conventional vibration eliminators 18, 20 near outlet 14 and outlet 16, respectively, known to those skilled in the art As shown in Figure IB, cooling system 10 may also include a suction line 19 placed near the intake 14 of the compressor 12, but the suction filter is not required.The cooling system 10 also includes a conductive or 22 connecting the output gate 16 of the compressor 12 with. a reversing valve 24. The reversing valve 24 is connected via a conduit 26 to a first gas damper 28 of a condenser 30. The condenser 30 typically includes a series of serpentines 31 to facilitate heat transfer between the refrigerant and the condenser. environment surrounding the condenser 30. A sensor 32 located near the first gas gate 28"is used to measure the temperature of the coolant.The sensor 32 is preferably connected to a part of the coil 31 near the first gas gate 28, more preferably, the sensor is connected to the coil in a position in which the refrigerant is no longer superheated, and more preferably the sensor includes a temperature sensitive bulb located in the double curve return of the condenser coil. sensor 32 may be connected to any desired portion of coil 31 and may also be connected to conduit 26 close to the first mere gas gate 28. The condenser 30 is typically cooled by air and is located outside to facilitate heat transfer. The condenser 30 may include one or more fans (not shown in the accompanying Figures) to increase heat transfer. The condenser 30 preferably includes a condensing tube 36 and a subcooler 38 as part of the condenser coil. More preferably, the condenser 30 includes a condensing tube, a subcooler as set forth in the co-pending and joint application of the assignee Serial No. 08 / 500,319, filed July 10, 1995, which is incorporated herein by reference. title AREFRIGERATION CONDENSER, RECE? VKR AND SUBCOOLER SYS? EM =, which is incorporated herein by reference in its entirety. This capacitor is available from the transferee with the trade name of Sierra Circuit. In this preferred arrangement, the condensing tube and portions of the condenser lighter subreff allow an approximate 25% increase in heat transfer capacity, with a decrease of approximately 10% in the refrigerant charge required for efficient cooling. This arrangement increases considerably in the efficiency of both the cooling and defrosting cycles. The circuit also advantageously allows the cooling system to operate more efficiently in colder climates. Of course, one skilled in the art will understand that the cooling system does not require light or a condenser with a condensing tube and a subcooler as part of the condenser. The condenser 30 includes a first liquid gate 34 which is connected to the conduit 42. As shown in Figure IA, the conduit 42 is connected to a defrost valve 46 which is connected in parallel with a check valve 44 located in a bypass conduit 43. The defrost valve 46 and bypass conduit 43 are also connected to conduit 45. Bypass conduit 43 is connected to conduits 42 and 45 by branch T 41 and 47, respectively. The defrost valve 46 is preferably an expansion valve, more preferably a thermostatic expansion valve. More preferably, the defrost valve 46 is an EMC type valve from SPORLAN Valve_ Company of Washington, Missouri. The EMC thermostatic expansion valve is described in more detail below. In another preferred embodiment, as shown in Figure IB, the cooling system 10 generally has the same components as those presented in relation to Figure 1A, but the defrost valve and the check valve are incorporated into a single one. valve 46a which acts as an expansion valve when the flow is in one direction and as a check valve when the valve is in the other direction. Valve 46a is also referred to as a thermal defrost expansion valve with an integral check valve. In addition, an equalizing tube 47a connects the valve 46a to the conduit 26 connecting the reversing valve 24 condenser 30. In addition, the bypass tube 43a includes a discharge valve 44a which, under certain circumstances, allows the refrigerant to be vented to the capacitor 30 if the pressure reaches a specific point. As shown in Figures IA and IB, a tube 49 connects the valves 46 and 46a to the sensor 32 of the condenser 30 and the tube allows the valves to be adjusted in accordance with the temperature of the refrigerant close to the outlet of the condenser 30. In In detail, the sensor ~ 32 preferably comprises a bulb filled with coolant and the tube 49 generally comprises a capillary tube which connects the bulb to the valves 46 and 46a. The bulb is preferably positioned in such a way that when the temperature of the coil coolant close to the sensor 32 varies, the temperature and pressure of the coolant in the bulb also varies. This causes a corresponding change in the pressure of the tube 49, and the change in pressure in the tube allows the valves 46 and 46a to be adjusted as desired. Referring again to Figure IA, the conduit 45 is connected to a bypass T 55 connecting parallel conduits 51 and 53. The conduit 51 includes a solenoid valve 48 and an expansion valve 50 connected in series. The solenoid valve 48 is preferably a liquid solenoid valve and the expansion valve 50 is preferably a thermostatic expansion valve, and more preferably an EMC type valve from SPORLAN Valve Company of Washington, Missouri, which is described in greater detail below. The thermal expansion valve 50 operates due to a pressure difference such that the high pressure liquid refrigerant becomes liquid refrigerant at low pressure before entering the evaporator 54. Connected in parallel with the expansion valve 50 a solenoid valve 48 is a check valve 52 on the conductor 53. Another bypass T 55 connects the conduits 51 and 53 to the conduit 57. The conduit 57 is connected to a first liquid gate 56 of the evaporator 54. The evaporator 54 preferably includes a conventional coil 58 and one or more fans (not shown) to assist in heat transfer between the coil of the evaporator 58 and the refigerated space. It will be appreciated that the refining system 10 in any of the embodiments presented herein may include one or more evaporators e.g. two or four, but it will be appreciated that the system may include any number of evaporators. Advantageously, this allows the system 10 to cool large areas or different areas. In addition, in contrast to conventional heat pumps having a temperature range of the refrigerant entering the 40-451F evaporator (with reference to the suction temperature), the temperature of the refrigerant entering the evaporator 54 of the system 10 is preferably about 25lF or less, but the coolant can also have a higher temperature. As shown in Figure IB, the conduit 45 includes a dual flow liquid filter 45a which filters the refrigerant when it flows in any of the conduit directions. The conduit 45 also includes a double-flow solenoid valve 48a in series with the valve 50a which acts as an expansion valve when the flow is in one direction and a check valve when the flow is in the other. This valve 50a is also referred to as a normal thermal expansion valve with an integral check valve. The 48a dual-flow solenoid valve, the expansion and retention valve combination 46a and 50a, and the 45a dual-flow liquid filter are available from SPORLAN Valve Company of Washington, Missouri and Aleo Controls Division of Emerson Electric GmbH &; Co. De Waiblingen, Germany. As shown in Figures 1A and IB, the evaporator 54 includes a first gas gate 60 connected by a bypass T 61 to a conduit 62 and a recovery container circuit 66. The conduit 62 includes a sensor 63 and a valve 64. The sensor 63 measures the temperature in the conduit 62 near the first gas gate 60 and the sensor 63 is connected via a tube 65 to the expansion valve 50. In detail, the sensor 63 comprises a bulb filled with coolant and the tube 65 comprises a capillary tube. The bulb is preferably located near the conduit 62 and in a heat exchange relationship with the refrigerant inside the conduit 62. When the refrigerant temperature inside the bulb changes, the temperature and pressure of the refrigerant in the bulb and the tube 65 also change. This change in pressure in the tube 65 is used to adjust the valves 50 or 50a. the recovery vessel circuit 66 includes a check valve 68 which controls the flow of the refrigerant through the circuit 66. The conduits 62 and 66 are joined in a bypass T 69 with a duct 70. The duct 70 is connected to the reversing valve 24 and reversing valve 24 is connected via conduit 72 to the low pressure inlet port 14 of compressor 12. As seen in FIG. IB, system 10 may also include a tube 67a connecting to the valve 50a with the conduit 62 in the evaporator 54. The tube 67a is preferably connected near the outlet of the evaporator 54, so that the pressure of the refrigerant leaving the evaporator can be communicated to the valve 50a. This allows the valve 50a to control the amount of refrigerant flowing inside the evaporator 54, which determines the amount of refrigerant leaving the evaporator. Advantageously, the valve 50a can work together with the sensor 63 and the tube 65 to determine both the temperature and the pressure of the refrigerant leaving the evaporator, such that the flow of refrigerant to the evaporator can be adjusted concomitantly. This allows the valve 50a to be used to ensure that no liquid refrigerant flows to the compressor 12 which can damage or destroy the compressor. As mentioned above, the cooling system 10 may include one or more condenser fans that facilitate heat transfer. These condenser fans are located near the condenser 54 and the fans, for example, can have variable speeds and can be controlled automatically according to factors such as the temperature and pressure of the refrigerant or the surrounding environment, but fans can also be fixed fans that turn on and off. The fans can advantageously help to control the pressure of the refrigeration cycle 10. For example, during a refrigeration cycle, if the pressure is low or normal, the condenser fans are preferably turned off, but if the pressure is high, then the fans are turned off. Condenser fans are preferably switched on. Another feature of the system presented in the co-pending U.S. patent application No. 08 / 500,319 25 is a floating head system that allows the condenser pressure to vary with ambient temperature. In this system, the expansion valve requires a pressure differential of at least about 25 pounds, therefore, subcooling of refrigerant is often required before entry into the evaporator. At the initial start-up of the system, or after a defrost cycle, there is a large load on the compressor and the pressure controller makes the solenoid valve vascular, which is sensitive to the suction pressure of the compressor. Also at start-up, with a low-pressure refrigerant inside the condenser (the condenser may also include a condensing tube containing low-pressure refrigerant), a check valve supplies pressurized refrigerant to an expansion valve before supply of the refrigerant to the evaporator. A pressure relief valve is used for the hydrostatic pressure produced by the increase in temperature in the tube. Preferably, the floating head system is used in conjunction with the Sierra Circuit to advantageously allow the cooling system to operate in colder climates without requiring the use of condenser fans during defrosting. The system, of course, does not require the use of the floating head system or the Sierra Circuit. Figure IA illustrates a preferred embodiment of the refrigerant flow during the refrigeration cycle. In operation, the compressor 12 supplies high pressure, high temperature refrigerant to the conduit 22. The person skilled in the art will understand that the term conduit is broadly defined to include pipes, conduits, hoses and the like to direct the refrigerant during refrigeration cycles and of defrost. The reversing valve 24, during the refrigeration cycle, directs the refrigerant in vapor through the conduit 26 of the condenser 30. After the refrigerant condenses in a liquid, the liquid flows out of the liquid gate 34 into the interior of the conduit 42. The liquid flows through the open check valve 44, passing the defrost valve 46, and through the solenoid valve 48 and the expansion valve 50 to the evaporator 54. The closed check valve 52 prevents the the refrigerant flows through the bypass conduit 53. The liquid refrigerant then enters the evaporator 54 where it absorbs heat and transforms into gas. The gaseous coolant flows out of the first gas gate 60 and into the interior of the conduit 62. The coolant flows through the check valve 64 into the conduit 70 and the reversing valve 24. The check valve 68 prevents the coolant from flow through the circuit of the recovery vessel 66. The reversing valve 24 directs the refrigerant through the conduit 72 in the direction of the compressor _12_- This completes the refrigeration circuit shown in Figure IA. In Figure IB illustrates another preferred embodiment of refrigerant flow during the refrigeration cycle. In operation, the compressor 12 supplies high pressure and high temperature refrigerant to the conduit 22. The reversing valve 24, during the refrigeration cycle, directs the vapor refrigerant through the conduit 26 to the condenser 30. After the refrigerant condenses in a liquid, the liquid flows out of the liquid gate 34 into the passageway 42 and through the valve 46a which acts as a check valve. The liquid then flows through the double flow liquid filter 45a, the double flow solenoid valve 48a, and the valve 50a which acts as an expansion valve. The refrigerant flows through the evaporator 54 and exits the first gas gate 60 to enter the conduit 62. The refrigerant flows through the check valve 64 into the conduit 70 and to the reverse valve 24. The check valve 68 prevents refrigerant from flowing through the circuit of the recovery vessel circuit 66. The reversing valve 24 directs the refrigerant through the conduit 72 in the direction of the compressor 12. This completes the refrigeration circuit shown in FIG. IB. Figure 2A illustrates the flow of refrigerant during a defrost cycle for the embodiment shown in Figure IA. During defrosting, the hot refrigerant vapor from the compressor 12 flows through the conduit 22 to the reversing valve 24. The reversing valve directs the hot refrigerant vapor into the conduit 70 connected to the first gas damper 60 of the evaporator 54 The check valve 64 is closed to prevent the high pressure refrigerant vapor from passing through the conduit 62. The refrigerant flows through the circuit of the recovery vessel 66 and the check valve 68 inside the evaporator 54. The hot gas flows through the evaporator 54 for defrosting and thawing the components within the evaporator 54, for example the coil 58 and the recovery container. The high pressure liquid refrigerant then flows out of the first liquid gate 56 of the evaporator and into the conduit 57. The check valve 52 which is located in the bypass pipe 53 is opened to allow the coolant to pass the valve 50 and the solenoid valve 48. The solenoid valve 48 is preferably closed in such a way that all the refrigerant flows through the bypass conduit 53. The refrigerant flowing through the conduit 45 then passes the defrost valve 46. The defrost valve 46 it is preferably a thermostatic expansion valve which decreases the pressure of the refigerator. The closed check valve 44 prevents the flow of the refrigerant through the bypass conduit 43. The low pressure refrigerant then flows through the condenser 30 and into the conduit 26. The condenser fans can be left on for operation in temperate climates . In colder climates, where the environmental pressure differential is lower, the condenser fans are preferably turned off to facilitate the return of the condenser to the cooling operation, the reversing valve 24 then directs the refrigerant into the conduit 72 connected to the condenser. low pressure inlet gate 14 of compressor 12. This completes the defrost circuit shown in Figure 2A. Figure 2B illustrates the flow of the refrigerant during a defrost cycle for the embodiment shown in Figure IB. during defrosting, the hot refrigerant vapor from the compressor 12 flows through the conduit 22 to the reversing valve 24. The reversing valve directs the hot refrigerant vapor-inside the conduit 70 connected to the first gas damper 60 of the evaporator 54 The check valve 64 is closed to prevent the high pressure refrigerant vapor from passing through the conduit 62 and the refrigerant flows through the recovery vessel circuit 66 and the check valve 68 into the evaporator 54. The hot gas flows through. the evaporator 54 for defrosting and thawing the components within the evaporator 54, for example the coil 58 and the recovery container. The high pressure liquid refrigerant then flows out of the first liquid gate 56 of the evaporator, into the conduit 57 and through the valve 50a which acts as a check valve and through the double flow solenoid valve 48a. The refrigerant flowing through the conduit 45 then passes through the double flow liquid filter 45a and the valve 46a which, for the refrigerant flowing in this direction, is a thermostatic expansion valve that lowers the refrigerant pressure. The equalizing tube 47a connected to the valve 46a includes a temperature sensitive bulb which measures the temperature of the refrigerant in the conduit 26 and the valve 46a includes a pressure sensor which measures the pressure of the refrigerant entering the condenser 30. Valve 46a controls the amount of refrigerant that enters the condenser during the defrost cycle to ensure that only steam escapes from the condenser and no liquid is supplied to the compressor. The low pressure refrigerant then flows through the condenser 30 and into the conduit 26. The condenser fans can be left on for operation in temperate climates but in colder climates, where the environmental pressure differential is lower, the fans of the The condenser is preferably turned off to facilitate the return of the condenser to the cooling operation. The reversing valve 24 then directs the refrigerant into the conduit 72 connected to the low pressure inlet gate 14 of the compressor 12. This completes the defrost circuit shown in Figure 2A.

The defrost cycles shown in Figures 2A and 2B preferably end when a predetermined pressure is reached in the system 10. Under certain circumstances, since the pressure of the system 10 could accumulate hydrostatically, the discharge valve 44a of the bypass tube 43a it allows the refrigerant to pass the valve 46a and flows directly to the condenser 30 if the pressure exceeds a predetermined point. Advantageously, the discharge valve 44a is adjustable, such that the pressure at which the valve 44a allows the flow can be adjusted according to the desired use of the system 10. Additionally, the evaporator fans are preferably turned off during the cycle. defrosting to prevent them from blowing hot air into refrigerated spaces. More preferably, the vapors of the evaporator are controlled by an electronic time delay by which the fans do not ignite after the defrost cycle until the evaporator coil is cooled following the refrigeration cycle. In addition, the condenser fans are preferably ignited at full speed to ensure maximum cooling of the refrigerant flowing through the condenser 30 during the defrost cycle. Another preferred embodiment of the hot gas defrosting refrigeration system 10 is shown in Figures 3-4. Although the invention described in this embodiment uses a Sierra Circuit, the advantages and benefits of the present invention can also be achieved without the use of this type of capacitor. The embodiment of the hot gas defrosting refrigeration system 10 shown in Figures 3-4 is particularly advantageous for operation in colder climates where the condenser 30 can be "under heavy loads." This embodiment of the invention it generally includes the components shown in Figures L and 2A, but it will be understood that this embodiment or other embodiments presented in this document may include the components shown in Figures IB and 2B, or any desired combination of components discussed above. As shown in Figures 3-4, the cooling system includes a condensing tube 310 generally located between the condenser 30 and the evaporator 54. In detail, the conduit 43 includes a bypass T 312 connected in series with the valve retention 44. Bypass T 312 allows refrigerant to flow through conduit 314 and within from a socket 315 of the condensing tube 310. The bypass T 312 is also connected to a bypass duct 324 which is connected to the duct 53 with the check valve 52. Thus, the bypass duct 324 connects to the ducts 43 and 53. The condensing tube 310 includes an outlet 316 which is connected to the conduit 318. The conduit 318 is connected to a bypass T 320 located in the conduit 45. Located between a bypass T 320 and the solenoid valve 48 is a check valve 328 and located between the bypass T-3-20 and the defrost valve 46 there is a check valve 326. As in the case of conventional condensation tubes, the condensation tube 310 used in this embodiment of the present invention (1) provides heat for the inlet of the condenser 30 and (2) provides additional refrigerant inside the evaporator 54. Advantageously, the condensing tube 310 It compensates for ambient temperatures in colder climates that would otherwise be insufficient for proper operation of condenser 30. Condensing tube 310 also provides the flexibility that is required for field installation of the refrigeration system, an expert in the art will recognize that the condensation tube can be used with various embodiments of the present invention, the use of the condensing tube is not required. Figure 3 illustrates a preferred embodiment of the refrigerant flow during a refrigeration cycle. In operation, the compressor 12 supplies high pressure and high temperature reflectance to the conduit 22. The reversing valve 24, during the refrigeration cycle, directs the vapor refrigerant through the conduit 26 of the condenser 30. The liquid refrigerant leaves the capacitor 30 through conduit 42 and enters bypass conduit 43. Closed check valve 326 causes the coolant to flow through conduit 43. Coolant passes through open check valve 44, bypass tee 312, the duct 314 and enters the condensing tube 310. The refrigerant does not flow through the duct 324 and into the bypass duct 53 since the check valve is closed 52. The liquid refrigerant exits condensing tube 310 through the conduit 318 and enters conduit 45 through bypass tee 320. Check valve 328 allows coolant to flow through the outlet. solenoid valve 48 and expansion valve 50 while closed defrost valve 46 prevents flow of refrigerant to condenser 30. Coolant enters evaporator 54 through first liquid gate 56 and exits evaporator 54 through the first gas damper 60. The refrigerant flows through the conduit 62, the check valve 64, the conduit 70 and enters the reversing valve 24. The check valve 68 prevents the refrigerant from flowing out of the first damper gate. gases 60 and within the circuit of the recovery vessel 66. The reversing valve 24 directs the refrigerant through the conduit 72 to the compressor 12. This completes the refining circuit shown in Figure 1. Figure 4 illustrates the flow of refrigerant during a defrost cycle for the preferred embodiment shown in Figure 3. During defrosting, the hot refrigerant The compressor 12 flows through the conduit 22 to the reversing valve 24. The reversing valve directs the hot refrigerant vapor into the conduit 70. The refrigerant flows through the recovery vessel circuit 66 because the check valve 64 is closed. The refrigerant leaving the evaporator 54 flows through the bypass conduit 53 and into the conduit 324 because the solenoid valve 48 is closed. The refrigerant flows through the bypass T 312 and into the condensing tube 310 through the conduit 314. The check valve 44 prevents the refrigerant from flowing into the conduit 42. The refrigerant exits condensing tube 310 through the conduit 318 and enters conduit 45. Coolant passes through check valve 326, defrost valve 46, conduit 42 and enters condenser 30. Check valve 328 prevents refrigerant from flowing to solenoid valve 48. The refrigerant then enters the condenser 30 through the first liquid gate 34 and exits the condenser 30 through the first gas gate 32. The coolant flows through the conduit 26 to the reverse valve 24 where the valve of the condensation tube 24 directs the refrigerant through the conduit 72 to the compressor 12. This completes the defrost cycle. The embodiment shown in Figures 5-6 further simplifies the use of condensing tube 310 in the cooling and thawing cycles, which advantageously provides for efficient operation in colder climates. This embodiment generally includes the components shown in Figures 3-4, but includes a second reversing valve 510 located near the condensing tube 310. The second reversing valve 510 is connected to the conduit 512. The conduit 512 connects the reversing valve 510 to bypass conduit 43 and conduit 45 via bypass T 514. Second reversing valve 510- is also connected to outlet 315 of condensing tube 310 through conduit 516. The reversing valve 510 it is also connected to the outlet 316 of the condensing tube 310 through the conduit 520. In addition, the reversing valve 510 is connected to the conduit 522, which is connected by a bypass T 524 to the bypass conduit 51 and 53.

In operation of the refrigeration cycle shown in Figure 5, the compressor 12 supplies hot vapor refrigerant to the conduit 22. The first reversing valve 24 directs the refrigerant-through the conduit 26 and into the condenser 30. The refrigerant that exits of the condenser 30 passes through the bypass conduit 43 because the defrost valve 46 is closed. The refrigerant then flows through conduit 512 to the second reversing valve 510. The second reversing valve 510 directs the refrigerant into condensing tube 310 through conduit 516. Coolant leaving condensing tube 310 flows to through conduit 520 where second reversing valve 510 directs the refrigerant into conduit 522. Coolant passes through solenoid valve 48 and cooling valve 50 and enters evaporator 54. Coolant does not flow through the bypass conduit 53 because the check valve 52 is closed. The refrigerant then passes through the evaporator 54 and exits through the conduit 62. The closed check valve 68 prevents the refrigerant from flowing through the recovery vessel circuit 66. The refrigerant then flows through the conduit 70 where the first valve The inverter 24 directs the refrigerant through the conduit 72 to the compressor 12. In operation of the defrost cycle shown in Figure 6, the compressor 12 supplies hot steam refrigerant to the conduit 22. The first reversing valve 24 directs the hot steam to through the duct 70 where it flows through the recovery vessel circuit 66 because the check valve 64 prevents the refrigerant from entering the duct 62. The hot steam refrigerant defrosts the evaporator 54 and exits through the first gate for liquid 56. The refrigerant then flows through the bypass line 53 because the solenoid valve of 48 is closed. The refrigerant then flows through conduit 522 where the second reversing valve 510 directs the refrigerant into condensing tube 310 through conduit 516. Coolant leaving condensing tube 310 flows into conduit 520 where the second reversing valve 510 directs the refrigerant through line 512. Coolant flows through bypass T 514 and passes through defrost valve 46 and enters condenser 30. Check valve ~~ 44 prevents refrigerant from flowing through the bypass tube 43. The refrigerant exiting the condenser 30 flows through the conduit 26 where the first reversing valve 24 directs the refrigerant through the conduit 72 to the compressor 12. This completes the defrost cycle. Advantageously, the embodiments shown in Figures 5-6 use substantially the same conduits and main components of the embodiments shown in Figures 1-2. Figure 7 illustrates a preferred embodiment of the present invention utilizing a variable speed controller for the condenser fan. As discussed above, one or more fans may be used in conjunction with the condenser to increase heat transfer between the condenser and the surrounding environment. Advantageously, the variable speed controller can be used with any embodiment of the present invention and, more preferably, with the embodiments shown in Figures 1-6. More preferably, this embodiment of cooling systems 710 includes a compressor 712 and a reversing valve 714. A conduit 716 allows the refrigerant to flow from the compressor 712 to the reversing valve 714 and the conduit 718 allows the refrigerant to flow from the reversing valve 714 to the compressor 712. The cooling system 710 also includes a condenser 720 connected to the reversing valve 714 via the conduit 722. The conduit 722 ^ preferably allows the refrigerant to flow in any direction between the condenser 720 and the investment valve 714, depending on whether a defrosting refrigeration cycle is being used. The capacitor 720 is also connected to a conduit 724. The conduit 724 includes a bypass T 726 which is connected to the conduits 728 and 730. The conduit 728 includes a derivation T 732 connected to the conduit 734 which is connected to the outlet of the conduit 728. condensation tube 736. Condensation tube 736 includes an outlet connected to conduit 738. Conduit 738 is "connected to conduit 730 by a bypass tee 740. Conduits 728 and 730 are connected by a bypass tee 742 to a conduit 744, which is connected to the evaporator 746. The evaporator 746 is connected by a conduit 748 to an inversion valve 714. The conduits 724, ~ 728, 730, 744 and 748 preferably allow the refrigerant to flow in any direction, depending on the cycle desired refrigeration- or defrost.The refrigeration system 710 shown in the Figure "7 also includes a variable speed controller 750" which is connected by a tube 752 to a sensor 754. This sensor 754. measures the repression of the refrigerant in the line 724. Connected to the variable speed controller 750 is a sensor 756 which measures the ambient temperature near the condenser 720. The variable speed controller 750 is connected by an electrical cable 758 to the condenser fan 760. Although only one fan is shown in the appended figure, a variety of fans can be used. The variable speed controller 750 controls the speed of the condenser fan 760 according to the temperature measured by the sensor 756 and the pressure within the conduit 724. Preferably, an ALCO FV31 speed controller manufactured by Aleo Controls Division of Emerson Electric is used. GmbH &Co. of Waiblingen, Germany to control the speed of the condenser fan 760. For example, the Variable Speed Controller - 750 can decelerate or shut off the condenser fan 760 in response to colder ambient temperatures because the pressure difference in the cooling system is less than a system of warmer ambient temperatures. In particular, the range of ambient temperatures for proper operation of the refrigerant is approximately -201C to + 551C. therefore, the operation of the fan is preferably controlled in such a way that the temperature of the refrigerant generally remains within the desired temperature range. Alternatively, the controller 750 may include a switch (not shown) for selecting the operation of the condenser fan 760 for a continuous minimum speed or the fan 750 may be selectively controlled to be paid when the ambient temperature is formed below a point previously determined. The previously determined point, for example, can be selected at the factory at the time of installation or can be selected by the user. The person skilled in the art will understand that the point previously determined could depend on the particular type of refrigerant used in the system or the location of the refrigeration system, advantageously, the variable speed controller 750 provides a faster defrost cycle and more efficient in such a way that the system can quickly return to the refining site. Figure 8 shows a preferred embodiment of the defrost valve 46 for use with any of the forms of embodiments of the invention. As discussed above, the defrost valve 46 is preferably a thermostatic expansion valve, and more preferably an EMC thermostatic expansion valve from SPORLAN Valve Company of Washington, Missouri. The EMC type de-icing valve advantageously allows the cooling system to operate in two different modes. In particular, the EMC type de-icing valve operates in an Atiro downward mode = when the evaporator load is at its maximum, and in a normal or Aretener mode = when the system is at a desired temperature. During the Aretener mode =, the evaporator load is at a minimum.

In detail, the load on the refrigeration system is generally the maximum during the start of the refrigeration cycle or. Or during a refrigeration cycle after a defrost cycle. Therefore, the system operates in a down draft mode because the down draft mode allows the greatest flow of refrigerant through the system. In particular, the load can be two to three times greater during the pull down mode than in the hold mode. Therefore, the system works in the down draft mode until it reaches your desired temperature. The system operates economically during normal operation since the retention mode decreases the amount of refrigerant flowing through the defrost valve. The EMC-type valve desirably includes a purge feature capable of being sealed again to allow the valve to operate at a flatter flow rate compared to a superheat curve. The flatter flow rate curve allows the valve to respond to change when the coolant superheats more stably. As shown in Figure 8, the EMC type de-icing valve includes a spring 810 and a slide piston 81-2. The valve includes a port 820 connected to a conduit 822. The conduit 822 allows liquid communication with a conduit 824 extending laterally through a portion of the piston 812. The conduit 824 is connected to a longitudinally extending conduit 826. The coolant can also flow into an annular conduit 825 surrounding the piston 812. The refrigerant flowing through the valve enters a chamber 828. The liquid chamber 828 is in liquid communication with a conduit 830 that allows the refrigerant to leave the liquid. valve. As best seen in Figure 9A, the EMC-type valve preferably includes a re-sealable purge feature. The purge feature allows the valve to respond to changes in the cooling system more quickly and more stably. In detail, the refrigerant flows through conduit 822 and into annular conduit 825 and conduit 826. Coolant can not flow through conduit 826 because pin 832 prevents flow through conduit 834. Pin 832 is shaped of cone to prevent flow through the conduit 834. The refrigerant can not flow through the conduit 825 either because the inclined portion 838 of the piston 812 is connected to a portion 840 of the valve body. However, the coolant can flow through the small annular opening 842 which lies between the collar 836 and the pin 812. The coolant flowing through the opening 842 flows through the side opening 844 and into the chamber 838. As best seen in Figure 9B, valve 46 preferably includes a retention mode. - During the retention mode, the coolant flows through the conduit 826 and the conduit 834 because the pin 832 is at least partially removed from the conduit 834. As best seen in Figure 9C, during the fire mode downwardly the coolant can flow through the conduits 826 and into the chamber 828. Additionally, the coolant can also flow through the annular conduit 825 since the piston 812 moves downward to allow the flow of the refrigerant between the body of the piston 840 and the inclined portion 838 of the piston 812. Therefore, the down draft mode allows the flow of the largest amount of refrigerant through the valve 46. Preferably, the down draft mode effectively doubles the capacity of the valve compared to the retention mode. Therefore, the EMC-type valve offers variable refrigerant flow capacity to substantially maintain the constant flow rate in accordance with the pressure within the refrigeration system. Although the present invention has been described with respect to certain particular embodiments, other embodiments apparent to those skilled in the art are also within the scope of the invention. Accordingly, it is intended to define the scope of the invention only through the following claims.

Claims (16)

1. CLAIMS 1. A refrigeration system that has refrigeration and thawing cycles, comprising: a compressor that has a low-pressure gate, a high-pressure gate; a condenser that has a gate for gases and a gate for liquids; an evaporator that has a gate for liquids and a gate for gases; an expansion valve arranged in a conduit that communicates the refrigerant from the liquid gate of the condenser to the liquid gate of the evaporator during the refrigerant site; a defrosting valve arranged in a conduit that communicates the refrigerant from the liquid gate of the evaporator to the liquid hatch of the condenser during the defrost cycle; and a reversing valve to direct the flow of refrigerant from the compressor high-pressure gate to the condenser gas damper during the cooling cycle, the reversing valve directing the flow from the evaporator gas damper to the gate low pressure of the compressor during the refrigeration cycle, the reversing valve directing the flow of the refrigerant from the compressor high-pressure gate to the evaporator gas damper during the defrost cycle, the reversing valve directing the flow of the gate for condenser gases to the compressor's low pressure gate during the defrost cycle.
2. 2. The cooling system of claim 1 wherein the condenser includes a portion of compression tube and a portion of subcooler between the gas gate and the liquid gate.
3. 3. The cooling system of claim 1 wherein the expansion valve and the defrost valve are in the same conduit.
4. 4. The refrigeration system of claim 1 - further comprising valves disposed between the condenser and the evaporator to allow the use of tubes for common liquids during the refrigeration and defrosting cycles.
5. 5. The cooling system of claim 1 further comprising a solenoid valve disposed between the condenser and the expansion valve, wherein the solenoid valve for liquids is opened during the refrigeration cycle and closed during the defrost cycle.
6. The cooling system of claim 1 further comprising: a compression tube disposed between the condenser and the evaporator, the compression tube having an inlet and an outlet; a check valve provided for the refrigerant to pass the defrost valve and enter the inlet of the compression tube during the refrigeration cycle, the refrigerant flowing from the outlet of the condensing tube during the refrigeration cycle, the refrigerant flowing from the exit from the condensing tube to the evaporator during the refrigeration cycle; and a valve provided for the refrigerant to pass the expansion valve and enter the condensate tube inlet during the defrost cycle, with the refrigerant flowing from the condensate tube outlet to the condenser during the defrost cycle.
7. The cooling system of claim 1 wherein the refrigerant flows from the compressor into the evaporator during the defrost cycle through the recovery vessel circuit.
8. The cooling system of claim 1 further comprising a fan operatively coupled to the condenser, the fan having a variable speed controller.
9. 9. The cooling system of claim 8 wherein the fan is pressure sensitive.
10. 10. The cooling system of claim 1 wherein either the expansion valve or the defrost valve comprises a low flow gate and a high flow gate.
11. The cooling system of claim 10 wherein the high flow gate is activated by pressure to maintain a constant flow rate in cold climates.
12. 12. The refueling system with hot gas defrost comprising a compressor, a condenser, and an evaporator, each having inputs and outputs interconnected by conduits for the refrigerant to flow in sequence through the compressor, the condenser, the evaporator and to the compressor during a refrigeration cycle, and to flow in sequence to through the compressor, the evaporator, the condenser and the compressor during a defrost cycle, the system further comprising: a reversing valve to direct the flow of refrigerant from the compressor to the condenser and from the evaporator to the compressor during the refrigeration cycle , the reversing valve directing the flow of refrigerant from the compressor to the evaporator and from the condenser to the compressor during the defrost cycle; an expansion valve and a solenoid valve in serial communication at an evaporator inlet; a condensing tube disposed between the defrost valve and the solenoid valve; and an inversion valve that allows the refrigerant to flow into the condensing tube from the condenser during the refrigeration cycle and into the condensing tube from the evaporator during the defrost cycle.
13. The cooling system of claim 12 further comprising a check valve in parallel with a defrost valve and a condenser outlet.
14. 14. The cooling system of claim 12 wherein the condenser has a sub-chiller portion and a condensing tube portion between the inlet and the outlet of the condenser.
15. 15. The cooling system of claim 12 further comprising a fan operably coupled to the condenser, the fan having a variable speed controller that is responsive to pressure differences.
16. 16. The cooling system of claim 12 wherein either the expansion valve or the defrost valve comprises a low flow gate and a high flow gate that are activated by pressure to maintain a constant flow rate in cold climates. or warm.