US3681934A

US3681934A - Refrigeration and defrost system

Info

Publication number: US3681934A
Application number: US71434A
Authority: US
Inventors: Arthur F Tudury
Original assignee: Bangor Punta Operations Inc
Current assignee: Bangor Punta Operations Inc
Priority date: 1970-09-11
Filing date: 1970-09-11
Publication date: 1972-08-08
Anticipated expiration: 1989-08-08

Abstract

The system includes a closed cycle, series connected compressor, condenser, expansion valve and evaporator with refrigerant flowing through the system in one direction for the refrigerating cycle. For defrosting, a conduit is provided for delivery of subcooled refrigerant from the outlet of the condenser to the outlet of the evaporator, a pump being provided to pump refrigerant in the opposite direction through the evaporator to effect defrosting thereof.

Description

United States Patent 1 1 3,681,934 Tudury [4 1 Aug. 8, 1972 [s41 REFRIGERA'I IONANDDEFROST 3,081,606 3/1963 Brose ..62/498 P SYSTEM 2,713,249 7/1955 Schordine ..62/1 55 [72] Inventor: Arthur F. Tudury, Hillsborough,

Pnmary Examiner-Meyer Perlin Calif 94010 I Attorney-Patrick J. Walsh [73] Assignee: Bangor Punta Operations, Inc.,

Greenwich, Conn.

Filed: Sept. 11, 1970 Appl. No.: 71,434

us. 01. ..62/l56, 62/196, 62/276 1111. C1 ..F25d2l/06 Field of Search ..62/l51, 156,81, 155,275, 62/278, 196, 197, 498 P [57] ABSTRACT conduit is provided for delivery of subcooled refrigerant from the outlet of the condenser to the outlet of the evaporator, a pump being provided to pump refrigerant in the opposite direction through the evaporator to effect defrosting thereof.

[56] References Cited 4 Clains, 1 Drawing Figure UNITED STATES PATENTS 2,983,114 5/1961 NOakeS ..62/278 500 480 f E 34 ZGb 32 ACCUMULATOR i PATENTED AUG 8 I972 momwwmnzzOo [NV ENTOR ARTHUR F TUDURY 10.5132 DOO REFRIGERATION AND DEFROST SYSTEM This invention relates to a refrigeration system and particularly relates to a refrigeration system having an improved defrosting system.

In the conventional closed refrigeration cycle, which includes a compressor, condenser, expansion valve and evaporator, the refrigerant passes through several states. On the high pressure side of the cycle, the refrigerant in a superheated vapor state flows from the outlet of the compressor into the condenser whereupon it gives up heat and is subsequently delivered in a subcooled substantially pure liquid state to the expansion valve. On the low pressure side of the cycle on the other side of the expansion valve, cold low pressure saturated refrigerant is supplied to the evaporator whereupon the latter absorbs heat. The state of the refrigerant is thereby changed to a superheated condition at the inlet of the compressor. In conventional defrost systems, a conduit is often provided to connect the outlet side of the compressor to the inlet side of the evaporator bypassing the condenser and expansion valve to provide superheated high pressure refrigerant in the vapor state to the evaporator to warm the coils and hence provide a defrosting action. While this type of system provides a defrosting action, such action is not efficient as the heat capacity of the superheated vapor is quite low, for example as compared to the heat capacity of the refrigerant in the liquid state. Consequently, the defrosting action must be performed over a considerable period of time. It is, in certain instances, desirable to provide a quick, efficient and effective defrosting action.

To the foregoing end, the present invention provides, in a conventional closed refrigerating cycle including a compressor, condenser, expansion valve, and evaporator respectively serially connected one to the other, a defrost system characterized by high efficiency and minimum defrosting time. The present invention provides a conduit connecting between the outlet of the condenser and the outlet of the evaporator coils (as used in the refrigeration cycle) for delivery of subcooled refrigerant to the coil. A pump is also provided in the conduit and pumps the subcooled liquid from the condenser through the coils in a direction opposite to the direction in which the refrigerant flows through the coils for refrigerating purposes. The subcooled liquid has a very substantial heat capacity and accordingly operates efficiently to give up heat at the-evaporator coils to provide a quick responsive defrosting action. Also, the provision of a pump in the defrost conduit between the condenser and evaporator coils further pressurizes the subcooled liquid and increases its heat capacity with the result that the refrigerant in the evaporator coils can give up heat even more rapidly thereby providing a quicker defrosting action. Optionally, the subcooled liquid can be pumped through a liquid heater on its way to the evaporator coils whereby the heat capacity of the refrigerant is increased hence further decreasing the time for effective defrosting action. A conduit bypassing the expansion valve is pro vided for directing, during the defrosting cycle, the refrigerant exiting from the evaporator coils back to the condenser or to a liquid receiver fed by the condenser.

Accordingly, it is a primary object of the present invention to provide an improved defrosting action in a refrigeration system.

It is another object of the present invention to provide a more efficient defrosting system in a refrigeration cycle wherein subcooled refrigerant is employed to provide the defrosting action.

It is still another object of the present invention to provide an improved defrosting system in a refrigeration cycle wherein the defrosting action is accomplished in a minimum of time.

These and further objects and advantages of the present invention will become more apparent upon reference to the following specification, appended claims and drawing wherein the sole drawing FIGURE discloses a schematic representation of a conventional refrigeration cycle employing the improved defrosting system hereof.

Referring now to the drawing, there is disclosed a conventional refrigeration cycle including a compressor 10, a condenser 12, a pair of

thermal expansion valves

14a and 14b, and a pair of evaporator coils 16a and 16b. As will be appreciated, a conduit 18 communicates between the outlet side of compressor 10 and condenser 12 for delivery of refrigerant in a superheated vapor state at high pressure to condenser 12. v

The outlet side of condensor 12 lies in communication with a liquid receiver 22 through a conduit 20 from which liquid is withdrawn via a conduit 24. Conduit 24 supplies the subcooled refrigerant from liquid receiver 22 to the thermal expansion valves 14 via branch conduits26a and 26b. The outlet sides of

expansion valves

14a and 14b lie in communication with respective evaporator coils 16a and

16b conduits

28a and 28b respectively,

conduits

28a and 28b supplying saturated low pressure refrigerant from the expansion valves to the coils. The low pressure superheated refrigerant flows from coils 16a and 16b via

conduits

30a and 30b respectively for delivery to an accumulator 32 via a main conduit 34. Accumulator 32' lies in communication via conduit 36 with the inlet side of compressor 10.

There is thus disclosed a closed refrigeration cycle where in the direction of flow of the refrigerant is indicated by the arrows in full line in the drawing. Particularly, the superheated refrigerant in the vapor state flows through conduit 18 from compressor 10 to condenser 12 wherein it is cooled and changed to the liquid state. The subcooled liquid refrigerant then flows via conduit 20 from condenser 12 into liquid receiver 22 and from the latter through

thermal expansion valves

14a and 14b via

conduits

24 and 26a and 26b. Saturated cold low pressure refrigerant is thus delivered via

conduits

28a and 28b to the evaporator coils whereat heat is absorbed from the surrounding medium. The refrigerant is returned in a superheated state to accumulator 32 and compressor 10 via

conduits

34 and 36 respectively. The foregoing describes the operation of a conventional refrigeration cycle,'dual coil units being employed in the disclosed form rather than a single coil unit.

In accordance with the present invention, a main defrost conduit 40 lies in communication between the liquid receiver 22 and a pump 42. The pump 42 further pressurizes subcooled refrigerant received from liquid receiver 22 and delivers this subcooled liquid refrigerant via a conduit 44, and

branch conduits

46a and 46b which lie in communication with

conduits

30a and 30b respectively on the outlet sides of the evaporator, to coils 16a and 16b. A pair of

conduits

48a and 48b lie in communication with

respective conduits

28a and 28b between the associated coils and expansion valves and lie in respective communication with

conduits

26a and 26b.

Conduits

48a and 48b thus bypass the respective

thermal expansion valves

14a and 14b. A closed defrost cycle is thus provided comprising liquid receiver 22, conduit 40, pump 42, conduit 44,

branch conduits

46a and 46b, evaporator coils 16a and 16b,

conduits

28a and 28b,

bypass conduits

48a and 48b and

return conduits

26a, 26b and 24.

For reasons to be described, flow control valves are provided in the various conduits.

ln bypass conduits

48a and 48b, there are provided

respective check valves

50a and 50b to prevent flow of refrigerant from bypassing the

expansion valves

14a and 14b during operation of the refrigerating system and to pemiit outflow of refrigerant from the coils to the return line 24 bypassing the thermal expansion valves during the defrosting cycle. A pair of normally

open valves

52a and 52b b provided in

conduits

30a and 30b respectively and a normally closed valve 54 is provided in defrost supply line 44. Also, a pair of normally closed valves 56a and 56b are provided in the

branch supply conduits

46a and 46b. Valves 52a, 52b, 54, 56a and 56b are preferrably electrically actuated, by operation of a time A clock indicated at T. The time clock may be provided with an electrical output which actuates the valves, through suitable conventional electrical circuitry, not shown, at the time or times set for the defrosting action.

In use, the time clock is set normally to actuate the valves as desired, preferrably from one to four times per day. Actuation of the valves interrupts the normal refrigerating cycle previously described and initiates the defrosting cycle. Particularly, by

opening valves

54, 56a and 56b, and closing normally

open valves

52a, 52b, subcooled refrigerant from the receiver 22 may be pumped by pump 42 via

conduits

40, 44, branch conduits 46aand 46b, and portions of

conduits

30a and 30b into the evaporator coils 163,41 and 16b for flow therethrough in a direction reversed from the direction of flow of the refrigerant therethrough during the refrigeration cycle. Since the subcooled refrigerant from the outlet side of the condenser or receiver has a high heat capacity, which heat capacity is increased further by action of pump 42, the subcooled refrigerant supplied to the evaporator coils rapidly, effectively, and efficiently gives up heat to provide a quick defrosting action at the coils. The refrigerant thereupon flows from the coils via

conduits

28a, 28b,

bypass conduits

48a, 48b through check valves 50a 50b, and

conduits

26a, 26b back to the receiver via return conduit 24. This defrosting action occurs for a predetermined time interval, under the control of timer T, at the expiration of which

valves

52a, 52b, are returned to their normally open positions and

valves

54, 56a and 56b are closed. Pump 42 is also deactivated such that the refrigeration cycle may once again be initiated. The defrosting action is sufficiently rapid as to permit the main compressor 10 to continue pressurizing the refrigerant from the accumulator 32 for delivery into the condenser 12 and receiver 22. In other words, the defrosting cycle is ,7 further increase the capacity of the subcooled liquid to give off beat and hence to further minimize the time for defrosting. A relief valve 60 is carried by heater 58 and is set to relieve the pressure buildup when valves 54 I and 56a, 56b are closed after the defrost cycle.

Also, a valve and sight glass combination 62 is provided on the bottom portion of accumulator 32 for automatically draining liquid refrigerant and oil from accumulator 32. Particularly, the valve is wired in series with the compressor motor so that the valve is open when the compressor is running and is closed when the compressor is idle.

It will thus be appreciated that the objects of the present invention are fully accomplished in that there is provided an efiective and efficient defrosting cycle in a conventional refrigeration system. Particularly, by the foregoing described invention, defrosting time is reduced to a minimum as the subcooled liquid provided the evaporator coils during the defrosting action-has significantly greater heat capacity than vaporized refrigerant and can hence give off heat at a more rapid rate than conventional defrost cycles providing vaporized refrigerant directly from the compressor to the evaporator coils.

The invention may be embodied in other specific forms without departing from the spirit or, essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the forgoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. A refrigeration and defrosting system comprising a compressor, a condenser, receiver, a thermal expansion valve, and an evaporator, conduit means connecting said compressor, condenser, receiver, valve and evaporator in series to define a first circuit for normally flowing a refrigerant therethrough in a direction to provide a refrigeration cycle, a pump having an inlet and an outlet and conduit means connecting said receiver to said pump inlet, said pump outlet to said evaporator, and said evaporator to said receiver to define a second circuit for the flow of subcooled liquid refrigerant from said receiver to said evaporator and return to said receiver for defrosting the evaporator.

2. The system according to claim 1 including a conduit bypassing said expansion valve for returning refrigerant from said evaporator to said receiver during the defrosting cycle.

3. The system according to claim 2 including means for preventing flow of refrigerant in the refrigerating cycle trough said bypass conduit.

4. The system according to claim 1 including a heater disposed in said connecting means defining said second circuit between said condenser and said evaporator for supplying additional heat to the subcooled refrigerant prior to its flow through said evaporator.