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Publication numberUS3392541 A
Publication typeGrant
Publication dateJul 16, 1968
Filing dateFeb 6, 1967
Priority dateFeb 6, 1967
Publication numberUS 3392541 A, US 3392541A, US-A-3392541, US3392541 A, US3392541A
InventorsOtto J Nussbaum
Original AssigneeLarkin Coils Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Plural compressor reverse cycle refrigeration or heat pump system
US 3392541 A
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Description  (OCR text may contain errors)

o. J. NUSSBAUM 3,392,541 PL-URAL COMPRESSOR REVERSE CYCLE REFRIGERATION July 16, 1968 OR HEAT PUMP SYSTEM 6, 1967 5 Sheets-Sheet 1 Filed Feb.

IN VENTOR O-r-ro J- NUSSBAUM BY 0.5m lfimum=.% 1101 QLQL J ATTORNEYS ig z July 16, 1968 o. J. NUSSBAUM 3,392,541

PLURAL COMPRESSOR REVERSE CYCLE REFRIGERATION OR HEAT PUMP SYSTEM INVENTOR O-rro I NUSSBAUM ATTORNEY 8 o. J. NUSSBAUM 3,392,541 PLURAL COMPRESSOR REVERSE CYCLE REFRTGFIRATION July 16, 1968 OR HEAT PUMP SYSTEM 5 Sheets-Sheet Filed Feb. 6, 1967 INVENTOR O-r-roI- NUSSBAUM United States Patent 3,392,541 PLURAL COMPRESSOR REVERSE CYCLE RE- FRIGERATION OR HEAT PUMP SYSTEM Otto J. Nussbaum, Atlanta, Ga., assignor to Larkin Coils, Inc., Atlanta, Ga., a corporation of Georgia Filed Feb. 6, 1967, Ser. No. 614,136 8 Claims. (Cl. 62-484) ABSTRACT OF THE DISCLOSURE A refrigeration system including plural compressors and plural sub-systems respectively including one of the compressors, an inside heat exchanger coil and an outside heat exchanger coil in each of the sub-systems, the outside coils of each of the sub-systems being assembled together in a common fin bundle heat exchanger unit, and at least one of the sub-systems being reversible so that during its reverse cycle operation, the heat rejected by the outside coil of the sub-system undergoing cooling cycle operation supplies heat to refrigerant in the outside coil of the other sub-system which is in reverse or heating cycle operation to ensure adequate supply of heat to the sub-system in heating cycle operation.

The present invention relates in general to reverse cycle refrigeration or heat pump systems, and more particularly to reverse cycle refrigeration or heat pump system having a multiplicity of refrigeration subsystems, and including a compressor, condenser and evaporator, at least one of which is a reverse cycle system, and wherein the condenser circuit coils of all sub-systems are so associated in heat transfer relation to each other that the condenser coils of one sub-system in a reverse mode uses the heat rejected by the condensing coils of other subsystems as the source of heat for evaporating refrigerant therein.

Reverse cycle refrigeration systems used heretofore both for defrosting and heating, require a source of heat, which usually took the form of an outdoor coil which abstracted heat either from the surrounding ambient air or which was submerged in water of a relatively high temperature. This, of course, rendered operation of the system highly dependent on outdoor ambient or water temperature to provide the heat required for effective evaporation of the refrigerant in the outdoor coil in the heating or defrosting mode.

With regard to hot gas defrostable refrigeration systems, the main objection to currently used hot gas defrost systems is higher initial cost because they require in addition to the usual liquid line and suction line, a third line, for delivering hot gas to the evaporator for defrost. For this reason reverse cycle defrosting which does not require such a hot gas line, becomes quite desirable both from the viewpoint of the producer and the installer. Unfortunately, climatic fluctuations and changing temperatures at the heat source even during the course of a day make an ordinary outdoor heat source unreliable and for this reason reverse cycle has rarely been used for hot gas defrosting in the past.

An object of the present invention is the provision in a reverse cycle refrigeration or heat pump system having an outdoor coil, of a heat source for the outdoor coil which is independent of outdoor ambient, or Water temperatures and uses as a source of heat the heat rejection of another refrigeration compressor which is brought into heat transfer relationship with the outdoor coil of the system to be defrosted or to be used for heating.

Another object of the present invention is the provision of a reverse cycle refrigeration or heat pump system having a multiplicity of sub-systems each including a com- 3,392,541 Patented July 16, 1968 pressor, outdoor condenser coils and an evaporator, one or more of which subsystems is reversible to a defrosting or heating mode, wherein the outdoor condenser coils of both sub-systems are disposed in heat transfer relation to each other to cause the condenser coils of the sub-systems in refrigerating or cooling mode to serve as a heat source for the condenser coil of the subsystem in defrosting or heating mode.

Another object of the present invention is the provision of a reverse cycle refrigeration system as described in the preceding paragraph, wherein the condenser coils of the plural sub-systems are incorporated in a single air-cooled condenser unit having coils forming plural individual circuits sharing a common fin bundle.

Yet another object of the present invention is the provision in a reverse cycle refrigeration as described in any of the preceding paragraphs, of novel condensing pressure control means for the condensing coils in thermal transfer relationship with each other.

Other objects, advantages, and capabilities of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings illustrating preferred embodiments of the invention.

FIGURE 1 is a schematic diagram of a reverse cycle refrigeration system embodying the present invention;

FIGURE 2 is a somewhat diagrammatic section view of a multiple circuit condenser unit which may be used in the system of FIGURE 1;

FIGURE 3 is a diagrammatic illustration of a condensing pressure control arrangement usable therewith; and

FIGURES 4 and 5 are schematic diagrams of modifications of the reverse cycle refrigeration system.

Referring to the drawings, and particularly to FIG- URES 1 and 2, the reverse cycle refrigeration system of the present invention involves a multiplicity of refrigeration sub-systems indicated generally by the reference characters 10 and 11. The system 10 comprises a conventional compression 12 having a high or discharge side and a low or suction side, the compressor discharge being connected through a four-way valve 13 and conduit 14 to the inlet of condensing or outdoor coil 15, the outlet of which is connected through one branch conduit 16 and check valve 16 to receiver 17 and through another branch conduit 18 and an expansion valve 18 to a receiver outlet conduit 19 extending at one end into the receiver 17 through a filter-dryer 1'9 and sight glass 19", if desired, and at the other end through a solenoid valve 20 and thermostatic expansion valve 21 to the inlet of evaporator or indoor coil 22. The outlet of evaporator 22 is coupled through outlet line 23, four-way valve 13 and suction line 24 having a conventional accumulator 25 therein to the suction side of compressor 12. A by-pass conduit 26 controlled by check valve 26 permitting flow only from r the evaporator 22 toward condensing coil 15 by-passes the solenoid valve 24} and expansion valve 21.

Similarly, the sub-system 11, which is here shown as a non-reversible sub-system but may also be reversible if desired, comprises a compressor 12a connected through conduit 14a to the inlet of condensing or outdoor coil 15a, the outlet of which is connected through conduit 16a to receiver 17a. The receiver outlet conduit 19a connects the receiver to the inlet of evaporator 22a, through thermostatic expansion valve 21a, and the evaporator outlet is connected through suction line 24a directly to the suction side of compressor 12a.

The four-way valve 13 has connection a to the compressor discharge, connection [2 to the condenser inlet conduit 14, connection 0 to the evaporator outlet conduit 23, and connection 0' to the suction line 24, together with an internal valve member or members for interconnecting connections a and b, together and conneetions c and d together in the refrigeration or cooling mode of sub-system If), and for interconnecting connections (1 and together and connections I) and d together in the defrost or heating mode of system 10.

The condensing or outdoor coils 15 and 15a form a common condenser-heat source 2.7 for the pair of subsystems 10, 11 with the coils thereof forming two separate and individual circuits so farranged that the coils or refrigerant carrying tubes thereof are always in close proximity to each other so as to'facilitate heat transfer from one circuit to the other. There are a variety of ways this may be accomplished, as by a tube-in-tube heat exchanger in which the tube of refrigerant circuit would be located inside the tube of refrigerant circuit 11 or both refrigerant circuits may be on the refrigerant side of a shell-and-tube heat exchanger filled with water; and transfer of heat from one circuit to the other may be by way of the water. Numerous other possibilities to accomplish the same purpose may suggest themselves to those familiar with this art.

However, a preferred embodiment of the common condenser-heat source 27 is to incorporate the condensing coils and 15a in a single condenser unit of tubes forming two individual circuits sharing a common fin bundle, as diagrammatically shown in FIGURE 2. This common condenser-heat source unit 27 is in the form of a fin and tube condenser unit wherein the tubes are arranged in a sinuous path by U-shaped bends at the ends of the respective straight tube sections, but wherein the tubes are so arranged that two separate and distinct refrigerant circuits are provided. One means for arranging the tubes to form the condensing coil circuit 15 for system 10 and to form the condensing coil circuit 15a for the system 11 in a common fin bundle structure is illustrated in FIG- URE 2, one of the fins being indicated by the reference character 28, and the tube or conduit sections for the condensing coil 15a being shown in heavy lines while the tube sections forming the condensing coil 15 are shown in lighter lines to visually distinguish them.

In operation, assuming both systems 10 and 11 to be in refrigeration mode with the four-way valve 13 positioned to communicate connections a and b with each other and connections 0 and d with each other, refrigerant flow is from the compressor 12 through the four-way valve 13 and conduit 14 to the condensing or outdoor coils 15 of the common condenser-heat source unit 27, and from there through the check valve 16 and conduit 16 to the receiver 17. From the receiver 17, the liquid refrigerant proceeds through the filter-dryer 19' and sight glass 19", and through conduit 19 through the evaporator 22 through the open solenoid valve 20 and the thermostatic expansion valve 21. The vaporized refrigerant is conducted from the evaporator 22 through line 23, four-way valve 13, and suction line 24 including the accumulator to the suction side of the compressor 12. Similarly, for system 11, refrigerant flow is from the compressor 1211 through the conduit 14a to the coils 15a of the common condenser-heat source 27 and from there through conduit 16a to the receiver 17a. The liquid proceeds from the receiver 17a through the conduit 19a and thermostatic expansion valve 21a to the evaporator 22a, the vaporized refrigerant being then conducted from the evaporator 22a through suction line 24m to the suction side of the compressor 120. In this case, the common condenser-heat source 27 functions as a condenser for both systems 10 and 11. Consequently, there is no substantial heat exchange between the systems 10 and 11 during this part of the cycle.

When the four-way valve 13 is adjusted to the defrost or heating mode, communicating connections a and 0 together and connections b and d together, the compressor 12 discharges through the four-way valve 13 and outlet conduit 23 to the exit end of the evaporator 22 which new functions as condenser. Condensed liquid from the evaporator 22 bypassing the expansion valve 21 and solenoid valve 26 through by-pass conduit 26 and chcckvalve 26, passes through the liquid line 19 in a direction opposite that described in connection with the refrigeration mode, and it now enters the exit end of the set of coils 15 of the common condenser-heat source 27 through the line 18 and expansion valve 18'. The condensing coils 15 or outdoor coils, new function as an evaporator for system 10, with the heat for evaporation supplied by the condensing coils 15a of system 11. From the viewpoint of system 11, the condensing capacity is augmented by virtue of the cooling effects supplied by evaporation of refrigerant in the coils 15 of system 10. The evaporated refrigerant passes from the inlet end of the coils 15 through the conduit 14 to enter the four-way valve 13 through connection b, and is communicated from connection d communicating with four-way valve connection I), to the conduit 24a and accumulator 25 to the suction intake of the compressor 12 completing the cycle. The expansion valve 18 controlling the coils 15 during defrost, may be either of the thermostatic type or of the constant pressure type, or it may also be a capillary tube.

While the above-described system, except for the unit 27, involves the use of components of two refrigeration systems, indicated as system 10 and system 11, this neverthless represents quite a practical means of providing a heat source for the outdoor coil of the system in heating or defrost mode which is independent of outdoor ambient or water temperatures. Most frequently, commercial and industrial refrigerant plants employ more than one refrigeration system. For this reason, it becomes quite feasible to utilize the heat rejected by one refrigeration system for defrosting or heating with another system. Quite recently, packaged refrigeration systems have become available in which two or more individual condensing units are built into a single package or rack, where they often share a common condenser coil. It therefore becomes feasible in such installations involving more than one refrigeration system, to arrange the condensing or outdoor coils for each of the systems in heat transfer relationship with each other as by the common condenser-heat source unit 27 having a common fin bundle, or by other arrangements, such as a tube-in-tube heat exchanger or other arrangeemnts mentioned above. While in the embodiment of FIGURES 1 and 2, the system 10 is shown as a reverse cycle defrost system, while the system 11 is shown as a conventional refrigeration system, it will be apparent that the combination of two or more systems may be thus used; for example, both systems 10 and 11 may be of reverse defrost cycle type.

FIGURE 3 illustrates schematically one form of condensing pressure control which may be provided to effect control of the condenser-heat source 27. This condenserheat source control may, for example, as illustrated in FIGURE 3, comprise a series of damper blades 30 disposed to regulate air flow over the air-cooled condenserheat source unit 27, the damper blades 30 being actuated through a linkage diagrammatically indicated at 31 by a conventional damper operator 32 having a piston which is moved directly by refrigerant pressure from a sealed container 33 of refrigerant in heat transfer relation with coil 27, as for instance shown diagrammatically in FIG- URES 2 and 3. The pressure of the sealed refrigerant change in the container 33 rises and falls in response to a change in air temperature at the condenser-heat source unit, thus operating the damper blades. Other known methods of condensing pressure control may also be employed, depending upon whether an air-cooled, watercooled, or evaporative-cooled condenser is used. In certain instances, the cooling effect of the refrigerant evaporating during defrost in system 10 may be sufiicient to supply the entire condensing needs of system 11 so that the dampers 30 may be fully closed at that time, preventing air flow over the common condenser-heat source unit 27.

The defrost operation in the system of FIGURES 1 and 2, may be, for example, initiated automatically by a conventional timing device, the function of which is to switch the four-way valve 13 into the defrost position communicating connections a and 0 together, and connections b and d together, while at the same time stopping air movement by the fan of the evaporator 22. Defrost may be terminated at a pre-set span of time, or by a thermostatic device which senses the temperature of the surface of evaporator 22. Upon completion of defrost, the four-way valve 13 is returned to its normal refrigeration position, but flow of liquid to evaporator 22 is not resumed for a short interval so as to make it possible to evacuate any residual liquid from the evaporator 22 and reduce the refrigerant pressure in the evaporator back to normal. This may be accomplished by maintaining the solenoid valve 20 closed for approximately one minute after completion of defrost, at the same time maintaining the fan of evaporator 22 stopped. The defrost timer should also be provided with means to maintain the compressor 12a in operation while the four-way valve 13 is in the defrost position.

FIGURE 4 is a slightly modified version of the system of FIGURE 1, in which the heat of the liquid refrigerant is also utilized. The system of FIGURE 4 is a receiverless system, the condenser outlet conduit 16 having the check valve 16 therein by-passing the expansion valve 18' and the continuation of the condenser outlet line 16, which is indicated for convenience by the reference character 19 to facilitate co-relation with FIGURE 1, has an accumulator-heat exchanger 40 therein whereby the liquid refrigerant flowing in the liquid line 19 is in heat-transfer relationship With vaporized refrigerant returning from the evaporator coil 22a of the system 11 through its conduit 23a and suction line 24a to the compressor 12a. Similarly, the condenser outlet line 16a, of system 11 extends through an accumulator-heat exchanger 41, in heattransfer relationship with the vaporized refrigerant returning from evaporator 22 through the suction line 24 to the compressor 12 of system 10, the continuation of conduit 16a being indicated at 19a and extending through the thermostatic expansion valve' 21a to the inlet of the evaporator 22a.

It will be apparent that with this arrangement of FIG- URE 4, when the four-way valve 12 is in the defrost position, connecting the discharge of compressor 12 through the evaporator outlet conduit 23 to the exit end of evaporator 22 and connecting the conduit 14 at the inlet of the condensing coils 15 through the accumulator-heat exchanger 41 to the suction side of the compressor 12, the accumulator-heat exchanger 41 supplements the common condenser-heat source 27 by transfer of heat from the liquid flowing in the internal coils of the accumulatorheat exchanger 41 to the vaporized refrigerant returning from the outdoor coils 15 to the suction side of the compressor 12, while the heat rejected by liquid refrigerant flowing in the coil of the accumulator-heat exchanger 40 when the system is in either the refrigeration or defrost mode is transferred by heat exchange to the refrigerant returning from the evaporator 22a to the suction side of compressor 12a to re-evaporate any liquid phase refrigerant that may be returning from the evaporator 22a. This is particularly useful when the system 11 is a hotgas defrost system, wherein, for example, a hot-gas defrost line 43 controlled by a hot-gas solenoid valve 44, both shown in broken lines to indicate that they may be optionally included or omitted, is provided to selectively connect the discharge side of compressor 12a to the inlet end of the evaporator 22a, in which event it is necessary to ensure reevaporation of any refrigerant which condenses in the evaporator 22a during the defrost cycle to prevent return of liquid refrigerant to the compressor 12a. Of course, the sub-system 11 of the FIGURE 4 arrangement may be either a conventional refrigeration system which omits the hot-gas line 43 or a hot-gas defrostable system as shown.

Another modification is shown in FIGURE 5 wherein the concepts of the present invention are incorporated in a plural compressor system similar to the systems of FIG- URES l and 4, but wherein both sub-systems, indicated by reference characters and 111, have a four-way valve 13, 13a therein to render both sub-systems reversible. The system of FIGURE 5 may operate normally as a rnuti-stage cascade refrigeration system, the sub-system 110 to the left of FIGURE 5, corresponding generally to sub-system 10 and serving as the second stage refrigeration system in the refrigeration mode and the sub-system 111 corresponding generally to sub-system 11 of FIGURE 1 serving as the first-stage of the cascade system in the refrigeration mode. The reference characters in FIGURE 5 corresponding to those used in FIGURE 1 designate correspoding components. In the refrigeration mode of the system of FIGURE 5, refrigerant is discharged from compressor 12a and four-way valve 13a to conduit 23a to coils 22a now serving as a condenser. The condensed refrigerant passes through by-pass conduit 26a and check valve 26'a, liquid line 19a and expansion valve 18'a into coils 15a of the common condenser-heat source unit 27, where the refrigerant vaporizes and returns to compressor 12a through four-way valve 13a.

In the sub-system 110, the refrigerant discharged from compressor 12 passes through four-way valve '13 and conduit 14 to the condensing coils 15 of the common condenser-heat source unit 27, the condensed refrigerant bypassing the expansion valve 18 through check valve 16', and being conveyed through liquid line 19, liquid solenoid valve 20 and thermostatic valve 21 to the evaporator 22. The vaporized refrigerant then returns to the suction side of the compressor 12 through the evaporator outlet conduit 23, four-way valve 13, and suction conduit 24 having the accumulator 25 therein. It will be apparent that the vaporization of refrigerant in the coils 15a, now serving as the first-stage evaporator, cools the second-stage refrigerant flowing in the condensing coils 15 to provide a twostage cascade refrigeration system.

When the system 110 is to be reversed for the defrost or heating cycle, the other sub-system 111 associated therewith must also be reversed. Thus, in the defrost mode, the four-way valves 13a and 13 are adjusted, so that the refrigerant discharge from compressor 12a flows directly through conduit 14a to the coils 15a, condensing therein and flowing through check-valve 16'a and thermostatic expansion valve 21a to the coils 22a, now serving as an evaporator, and then returning to the compressor through conduits 23a, 24a and accumulator 25a.

Similarly, refrigerant discharge from the compressor 12 flows through the four-way valve 13 and conduit 23 to the evaporator 22 and then through check valve 26', liquid line 19 and expansion valve 18' to the coils 15, where the refrigerant vaporizes and returns through the four-way valve 13, suction line 24 and accumulator 25 to the compressor 12. Therefore, the heat rejected by condensation of refrigerant in the coils 15a now serving as a first-stage condenser supplies heat to the second-stage refrigerant evaporating in the coils 15 through thermal transfer therewith as described in connection with the preceding embodiments.

While several modifications of the present invention have been specifically shown and described, it is apparent that other modifications may be made within the spirit and scope of the invention, and it is desired, therefore, that only such limitations be placed on the invention as are imposed by the prior art and set forth in the appended claims.

What is claimed:

1. A plural compressor reversible refrigeration system comprising first and second compressors, a first refrigeration circuit serving a first space to be conditioned including said first compressor, inside heat exchanger coil means within said first space, outside heat exchanger coil means located outside said first space and means for selectively interconnecting said coil means with said first compressor in a cooling cycle mode coursing refrigerant through said outside coil means to condense therein and through said ins-ide coil means to vaporize therein and in a heating cycle mode coursing refrigerant from said first compressor through said inside coil means to condense therein and reject heat to said first space and through said outside coil means to vaporize therein, and a second refrigerant circuit means serving a second distinct space to be conditioned communicating with said second compresor for conveying compressed gaseous refrigerant adjacent to said outside coil means and condense said gaseous refrigerant thereat in intimate heat transfer relation to refrigerant in said outside coil means for supplying heat rejected during condensing thereof to the refrigerant in said outside coil means when said first refrigeration circuit is in its heating cycle mode.

2. A refrigeration system as defined in claim 1, wherein said second refrigerant circuit means includes condensing coil means incorporated with said outside coil means in a single heat transfer device of the fin and tube having first and second sets of conduit coils forming the respective outside coil means and condensing coil means and defining two physically separate and individual refrigerant circuits, said heat transfer device having plural heat transfer fins disposed in highly thermally conductive physical contact with the conduit coils of both said sets defining a common fin bundle shared by both said sets and said sets of coils each having parallel straight coil segments interspersed between straight coil segments of the other set in closely adjacent relation throughout said heat transfer device.

3. A plural compressor reversible refrigeration system serving first and second distinct spaces to be separately conditioned thereby, each respectively including a compressor, outside coils located outside the spaces to be conditioned, an evaporator in the respective space to be conditioned and conduits interconnecting the same in respective individual refrigeration circuits, said first and second sub-systems each having means for selectively interconnecting the components thereof in a cooling cycle mode wherein refrigerant is coupled from said compressor to the outside coils thereof to condense therein and thence to the evaporator thereof to vaporize therein and said first sub-system having means for interconnecting the components thereof in a heating cycle mode wherein the refrigerant is coupled from said compressor to said evaporator to condense therein and thence to said outside coils to vaporize therein, means for operating said first subsystem in its heating cycle mode wherein heat is rejected to said first space while said second sub-system is in its cooling cycle mode, and said outside coils of both said first and second sub-systems being located in intimate heat transfer relation to each other for transfer of heat rejected by condensing refrigerant in the outside coils of said second sub-system to the refrigerant in said outside coils of said first sub-system while the latter is in its heating mode to provide a source of heat for vaporization of refrigerant in the outside coil of the first subsystem during its heating cycle.

4. A reversible refrigeration system as defined in claim 3, wherein said outside coils of both said sub-systems are incorporated in a single heat exchanger device having 8 a pair of physically independent refrigerant flow circuits for the respective sub-systems disposed in good thermal communication with each other to effect good heat transfer from either of said outside coils to the other, said coils comprising first and second sets of conduit coils each having parallel straight coil segments interspersed between straight coil segments of the other set in closely adjacent relation throughout said heat transfer device.

5. A reversible refrigeration system as defined in claim 3, wherein said outside coils of both said sub-systems are incorporated in a single heat transfer device of the fin and tube type having first and second sets of conduit coils forming the outside coils of said respective sub-systems and plural heat transfer fins defining a common fin bundle for said sets of conduit coils, and said sets of coils each having parallel straight coil segments interspersed between straight coil segments of the other set in closely adjacent relation throughout said heat transfer device.

6. A reversible refrigeration system as defined in claim 3, wherein said second sub-system includes a liquid conduit for communicating condensed liquid refrigerant from said outside coils to said evaporator, and said first subsystem includes a second heat exchange device connected in said liquid conduit for flow of liquid refrigerant therethrough and having selective connections with said outside coils and said compressor of said first sub-system during the heating cycle of the latter for flow of vapor phase refrigerant within said second heat exchange device in physically separated but intimate thermal exchange relation to said liquid refrigerant for transfer of heat from the latter to said vapor phase refrigerant.

7. A reversible refrigeration system as defined in claim 6, wherein said second sub-system includes means for selectively conducting hot gaseous refrigerant directly from the compressor discharge to the evaporator thereof for defrosting of said evaporator, and a third heat exchange device coupled between the evaporator and compressor of said second sub-system and between the evaporator and outside coils of said first sub-system for physically separated flow of refrigerant from said two subsystems in intimate heat transfer relation to each other.

8. A reversible refrigeration system as defined in claim 3, wherein said outside coils of said two sub-systems are located in an ambient air fiow path for heat exchange with the ambient air, control means for control of ambient air flow over said coils including damper means movable between closed position preventing air fiow over said coils and open positions admitting such air flow, refrigerant pressure responsive operating means for moving said damper means to said positions, and means for coupling said operating means to refrigerant pressure conditions indicating the air temperature at the region of said outside coils for activating the latter to position said damper means.

References Cited UNITED STATES PATENTS 2,221,688 11/1940 Gibson 62-160 2,241,033 5/1941 Huggins 62-175 2,241,060 5/1941 Gibson 62-160 2,769,314 11/ 1956 Wheeler 62-160 2,919,558 1/1960 Lauer 62-160 3,103,794 9/1963 Kyle 62-160 WILLIAM J. WYE, Primary Examiner.

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Classifications
U.S. Classification62/184, 62/335, 62/324.3, 62/510, 62/183, 62/175
International ClassificationF25B13/00, F25B7/00, F25B47/02, F25B49/02
Cooperative ClassificationF25B49/027, F25B13/00, F25B47/025, F25B7/00, F25B2400/06
European ClassificationF25B47/02B2, F25B49/02D, F25B13/00, F25B7/00