US2794329A - Variable temperature refrigeration - Google Patents

Description

June 4, 1957 c. s. HERRICK VARIABLE TEMPERATUR REFRIGERATION Filed June 29, 1954 Fig.

Fig. 2.

km w J M n 22 v J: mwfiw c w United States Carlyle S. Herrick, Alplaus,

Electric Company, a corporation or" ew York Application June 29, 1954, Serial No. 440,024 6 Claims. c1. 62-115) This invention relates to refrigeration systems and specifically to a method and apparatus to secure variable temperature levels in such systems.

Variable temperature refrigeration systems are desirable in heat pump construction and in domestic and commercial refrigerators. It is desirable that a reverse refrigeration system or heat pump employ a refrigerant mixture whose composition is varied automatically to maintain a constant system capacity over a wide variation in evaporator temperatures. A single refrigerant system will not operate at constant capacity over such temperature variations.

Accordingly, it is an object of my invention to provide a new and improved refrigeration system in which a pair of partly miscible refrigerants are employed.

It is another object of my invention to provide a refrigeration system which circulates selectively a variable composition of refrigerants in response to the load upon the system.

It is another object of the invention to provide a refrigeration system in which the storage liquid receiver is maintained at condenser pressure.

It is another object of the invention to provide a refrigeration system in which the composition of the refrigerant mixture is determined by the evaporator temperature.

It is a further object of the invention to provide a novel method of refrigeration in which the composition of the refrigerant mixture in the refrigeration system is automatically varied to produce different temperature levels of refrigeration.

In carrying out my invention in one form, the composition of the refrigerant mixture is varied with the evaporator temperature to maintain a constant capacity refrigeration system.

These and various other objects, features and advantages of the invention will be the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a schematic view of one form of a refrigeration system which embodies my invention; and

Fig. 2 is a schematic view of a second form of a refrigeration system.

In Fig. 1 of the drawing, a variable temperature refrigeration system which is indicated generally at 10, comprises a compressor 11 which communicates on its high pressure side with a condenser 12. Condenser 12 is connected to a liquid running receiver 13 in which a pair of partly miscible refrigerants are in a mixture 14 to circulate through the refrigeration system. An outlet 15 circulates mixture 14 through an expansion valve 16 to a heat exchange coil 17 within a liquid storage receiver 18. Coil 17 is connected to an outlet 19 in communication with the inlet side of an evaporator 20. Coil 17 is positioned in receiver 18 to cool the receiver to evaporator temperature. Expansion valve 16 is shown to be of a conventional type which is operated by a pressure tube 21 and diaphragm 22. A temperatureatent better understood from "ice operated or thermostatic valve or sections of capillary tubing could be employed as the expansion device. Evaporator 20 communicates with the inlet or low pressure side of compressor 11.

The storage receiver 18 is filled completely with an additional supply of the same refrigerants in two separate partly miscible phases or layers 23 and 24. Each of phases 23 and 24'contain both refrigerants in different proportions. Both receivers 13 and 18 are maintained at condenser pressure. Receiver 18 is connected to receiver 13 through a tube 25. A capillary tube 26 connects receiver 18 to outlet 15 between receiver 13 and expansion valve 16 to circulate slowly a continuous stream of refrigerant phase 23 thereto under gravity head. Tube 25 will replenish the refrigerants in receiver 18 from refrigerant mixture 14 in receiver 13. The temperature in receiver 18 is determined by coil 17 therein while the pressure is regulated by condenser 12.

Thepair of refrigerants, which are employed in the refrigeration system, may be miscible at condenser temperature but must be only partly immiscible at customary evaporator temperatures. The pair of partly miscible refrigerants forms two separate phases in which each phase is rich in one of the refrigerants and contains also a substantial amount of the second refrigerant. The amount of the second refrigerant in each phase is controlled by the temperature. It is desirable to have a wide variation of phase composition with temperature in the customary evaporator temperature range, The two phases must also have different densitiesso that separation is possible by gravity. The pair of refrigerants must have different volatilities so that the refrigerating capacities of the system may be altered.

The following pairs of refrigerants are given as examples of suitable refrigerant mixtures to be employed in such a variable temperature system: ammonia (NI-I3) and Freon 12 (CFzClz), ammonia (NI-I3) and Freon 114 (C2F4Cl2), ammonia (NI-I3) and perfluorocyclobu tane (CsFs), ammonia (NI-I3) and Freon 115 (C2F5Cl), ammonia (N113) and perfluoropropane (CsFs), sulfur dioxide (S02) and periiuorocyclobutane (C4Fa), methylbromide (CI-13131) and perfluorocyclobutane (C4Fs), methylene chloride (CHzClz) and perfluoropropane (CsFa), ethylchloride (CzHsCl) and perfluoropropane (CaFs), perfluoropropane (CsFs) and methylbromide (Cl-lsBr), perfluoropropane (CaFa) and methylchloride (CHsCl), perfluoropropane (CsFs) and Freon 21 (CHFClz), perfluoropropane (CzFs) and Freon 31 (CI-IzFCl), perfluorobutane (C4Fm) and Freon 21 (CI-IFClz), perfluorobutane (C4F1o) and methylene chloride (CHsCl), perfluorobutane (C4F1o) and methylene chloride (CHzClz), perfluorobutane (C4F10) and ethylchloride (CzHsCl), Freon 115 (CzFsCl) and methylene chloride (CHzClz), and Freon 115 (CzFsCl) and sulfur dioxide (S02).

In the operation of the refrigeration system which is shown in Fig. 1 of the drawing, compressor 11 pumps refrigerant mixture 14 through the condenser 12 to liquid running receiver 13. Refrigerant mixture 14 which may be miscible at condenser temperature is then circulated through outlet 15, expansion valve 16, coil 17, outlet 19, and evaporator 20 to the inlet side of compressor 11. Storage receiver 18, in which an additional supply of mixture 14 is contained in two separate partly miscible phases 23 and 24, is connected to both receiver 13 and outlet 15. Capillary tube 26 from receiver 18 provides a slow, continuous circulation of phase 23 to outlet 15 to vary the composition of refrigerant mixture 14 in response to the system load. Refrigerant phase 23 is shown to be the operating phase while the phase 24 is the storage phase. An increase in the evaporator temperature increases the concentration of the low capacity refrigerant in phase 23 v tions of the evaporator.

While a decrease in evaporator temperature increases the concentration of the high capacity refrigerant in phase 23. Thus, the capacity of the refrigeration system remains automatically constant over a Wide range of'temperature variations.- I V Refrigerant mixture 14 is withdrawn from receiver 13 through tube 25 to replenish the refrigerant's'in receiver 18 which are circulated to the system from phase 23 thereof. The composition. of refrigerant mixture 14 is determined by the system load through the pressure varia- Ho'wever, the volume of the refrigerant mixture remains constant in the refrigeration system through the addition of refrigerant phase 23 and the corresponding withdrawal of circulating mixture 14'.

In Fig. 2 of the drawing, a modified refrigeration system is shown in which the cooling coilsection 17 in Fig. 1 is eliminated. Storage receiver 18 is positioned in the refrigeration system'adjac'ent' evaporator 20m the outdoor air to coolthe refrigerants therein to evaporator temperature to provide separation into two separate partly miscible phases or layers 23 a'nd24. Liquid running receiver 13 is connected directly toevaporator 20 through outlet 15 with expansion valve, 16 therein. 'The refrigeration system of'Fig. 2 is'ot-herwise similar in structure and operation to the refrigeration system which is disclosed'in Fig. l.

As vwill be apparent to those skilled inthe art, the" objects of my invention are attained by the use of a refrigerant mixture which is varied with the evaporator temperature to maintain a constant capacity refrigeration system.

While other modifications of this invention and variations of apparatus which may be employed in' the scope of the invention have not been described, the invention is intended to include all such as may be embraced with in the following claims.

) What I claim as new and desirev to secure by Letters Patent of the United States is:

1. In a refrigeration system including acompressor, a condenser, and an evaporator, a pair of liquid receivers maintained at condenser pressure, a supply of partly miscible refrigerants in one of said receivers, a second supply partly miscible refrigerants in separate phases in the other receiver, and means to supply at least one of said phases tosaid first mentioned refrigerants to vary 4 the composition thereof.

2. In a refrigeration system including a compressor, a condenser, and an evaporator, a pair of liquid receivers maintained at condenser pressure, a supply of partly miscible refrigerants in one of said receivers, 21 second supply of partly miscible refrigerants in separate phases in the other receivers, means to selectively control the composition of said phases, and means to supply at least one of said phases to said first mentioned refrigerants to vary the composition thereof.

3. In a refrigeration system as set forth in claim 2,;

late a part of said'first refrigerant supply to said second refrigerant supply to replenish the volume thereof.

5. In a refrigeration system including a compressor,

a condenser, and an evaporator, a pair of liquid'receivers maintained at condenser pressure, a supply of partly miscible refrigerants in one'of said receivers, a second supply of partly miscible refrigerants in separate phases in the other receiver, said other receiver positioned adja-i cent the evaporator to selectively control the composition of said phases, and means to supply at least one of said phases to said first mentioned refrigerants to vary the composition thereof.

6. A method of refrigeration which comprises circulating a first supply of partly miscible refrigerants in a refrigeration system, providing a second supply of partly miscible refrigerants in separate phases at condenser pressure, circulating one of the phases to the first refrigerant supply to change the composition thereof, and

varying the composition of the phases in response to the system load.

References Cited in the file of this patent UNITED STATES PATENTS 2,255,584 Hubacker Sept. 9-, 1941 2,277,138 Newton Mar. 24,1942 2,682,756 Clark et al. July 6, 1954

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