US2693683A

US2693683A - Defrosting machine

Info

Publication number: US2693683A
Application number: US224319A
Authority: US
Inventors: Toothman Earl
Original assignee: EDWARD A DANFORTH
Current assignee: EDWARD A DANFORTH
Priority date: 1951-05-03
Filing date: 1951-05-03
Publication date: 1954-11-09
Anticipated expiration: 1971-11-09

Description

1954 E. TOOTHMAN 2,693,683

DEFROSTING MACHINE Filed May 3 1951 2 Sheets-Sheet l CONDENSER EECE/VEE INVENTOR. E/IEL T00 THMAN 2 Sheets-Sheet 2 1954 E. TOOTHMAN DEFROSTING MACHINE Filed May 3, 1951 N MIHMIH IN V EN TOR.

NNVI

EAEL Toormm/v United States Patent C DEFROSTING MACHINE Earl Toothman, San Francisco, Calif., assignor of onehalf to Edward A. Danforth, Palo Alto, Calif.

Application May 3, 1951, Serial No. 224,319

7 Claims. (Cl. 62-11755) This invention relates to a defrosting system and, more particularly, to a defrosting system for refrigeration units which employs hot gases from the compressor to heat, and thereby defrosts the evaporator coils.

In refrigeration systems employing a compressor, a condenser and evaporating coils and wherein a gas such as ammonia is compressed by the compressor and is then condensed in the condenser and evaporated in evaporating coils to cause refrigeration, the coils ice up or frost owing to condensation and freezing of water in the atmosphere.

Several defrosting systems have been suggested, and some of them are currently employed for automatically defrosting the evaporator coils. One type of automatic defrosting system employs the hot, compressed gases from the compressor as a source of heat to heat the coils. For this purpose by-pass means are provided for by-passing the condenser and conducting the hot gases directly to the evaporator coils. The by-pass means includes suitable valves, solenoids for operating the same and electrical timing means for operating the solenoids at predetermined intervals.

Certain dilficulties or disadvantages have been encountered in the installation and/or operation of prior automatic, hot gas defrosting systems. In one such system, during the refrigeration cycle hot gas from the compressor is passed through a heat storage vessel or reservoir containing a body of liquid. The hot gas heats the liquid, and this heat is employed during the defrosting cycle to vaporize liquid from the evaporator coils. In this system, the liquid, which constitutes the heat storage medium, is cooled very rapidly during the defrosting cycle, so much so that the liquid from the evaporator coils is not fully vaporized.

In another system, a direct heat exchange is provided during the defrosting cycle, between the hot gas from the compressor and the cold liquid from the evaporator coils. However, in this system, no provision is made for storage of liquid from the evaporator coils during the defrosting cycle. The refrigerant passes directly from the evaporator coils to the compressor. As a result, the supply of vapor in the suction line of the compressor is likely to be exhausted and, when this occurs, the compressor will simply pump liquid to the evaporator coils.

It is an object of the present invention to provide improved automatic defrosting means for refrigeration systems.

It is a further object of the invention to provide improved automatic defrosting means of the hot gas type for refrigeration systems.

Yet another object of the invention is to provide a hot gas defrosting system which obviates certain disadvantages of systems employed heretofore.

A further object of the invention is to provide a hot gas defrosting system which avoids the need for maintaining a supply of liquid to act as a heat reservoir.

Yet another object of the invention is to provide a hot gas defrosting system in which there is little or no likelihood of circulating liquid from the evaporator coils to the compressor, thence back to the evaporator coils.

Another object of the invention is to provide a hot gas defrosting system which can be easily and readily installed in an existing refrigeration system with a minimum of effort in the way of new connections and changes in the existing system.

These and other objects of the invention will be ap- 0 parent from the ensuing description and appended claims;

7 2,693,683 Patented Nov. 9, 1954 Certain forms of the invention are illustrated by way of example in the accompanying drawing and are described in detail hereinafter.

In the drawings:

Figure 1 is a diagrammatic view of a refrigeration system including automatic defrosting means constructed in accordance with the invention;

Figure 2 is a diagrammatic view of a defrosting system constructed in accordance with the invention, as applied to an existing refrigeration system.

Referring to Figure 1, a refrigeration system is there shown which includes the usual compressor 10, condenser 11, receiver 12 and evaporator coils 13. During normal operation of the system a suitable gas, such as ammonia, is compressed in the compressor 10. It is then conducted through a conduit 14 to the condenser 11 and is there condensed to a liquid, and the liquid refrigerant is then conducted through a conduit 15 to the receiver 12 for storage. From the receiver the liquid refrigerant is conducted through a conduit 16 and is expanded by an expansion valve 17 into a header 18, thence into the evaporator coils 13. Suitable automatic means well-known in the art, such as a feeler bulb (not shown), may be employed to operate the expansion valve so as to maintain suitable refrigeration conditions. Drip pan coils 20 are also provided, as is a fan driven by a motor/31 for circulating air over the coils.

The expanded gas from the coils, which may be partly liquefied, is returned to the compressor through a conduit 32. However, it is not returned directly to the compres sor. Instead, and in accordance with my invention, it is conducted first to an accumulator vessel 33 from which the vapor passes through a conduit 34 to an outer vessel 35 which forms a part of a heat exchanger and re-evaporator 36. Thence the vapor passes through a suction line 37 to the inlet of the compressor.

It will be seen that my system also includes a conduit 38 which is connected to the outlet of the compressor to by-pass the condenser and which communicates with, and extends to the bottom of an inner vessel 39 which is disposed within the outer vessel 35, and which also forms a part of the heat exchanger 36. Thence a hot gas line 40 leads to the drip pan coils 20 which are connected to the evaporator coils 13 through a conduit 41 containing a check valve 42, and through the conduit 16. A normally closed valve 45 is provided in the conduit 38 which is opened by a solenoid 46 when the latter is energized.

Another feature of the present invention comprises a connection between the vapor space in the receiver 12 and the outer vessel 35 through the medium of a conduit 47 containing a normally closed valve 48 which is opened when a solenoid 49 is energized. A manually operable shut-off valve 50 is also provided.

Electric current is provided for operating the defrosting system by a circuit comprising a timing switch 51 which may be of standard construction, a power lead 52 connected to each of the solenoids 46 and 49 and through a branch lead 52a to the fan motor 31, a power lead 53 connected to a terminal of the time switch and leads 54 and 55 connecting other terminals of the time switch with the fan motor 31 and the solenoids 46 and 49, respectively.

Operation during the refrigeration cycle proceeds as described above; i. e., gas is compressed in the compressor 16 and passes through the conduit 14 to the condenser 11 where it is condensed. It then passes through the conduit 15 to the receiver 12. The liquid refrigerant then passes through the conduit 16 and expansion valve 17 and is expanded into the evaporator coils 13 from which it returns to the condenser by way of the suction line 32 to the accumulator vessel 33, thence through con- .duit 34 to the outer vessel 35, thence through suction line 37 to the inlet of the compressor. At predetermined intervals, in accordance with the setting of time switch 51, the valves 45 and 48 are opened by the solenoids 46 and 49. At the same time the motor 31 and fan 30 are stopped. When the valves 45 and 48 are opened, hot gases from the compressor by-pass the condenser 11 and pass through the conduit 38 to the inner vessel 39 of the heat exchanger 36, thence through the hot gas line 40 to the drip pan coils 20 and, through the check valve 42 and lines 41 and 16, to the evaporator coils 13. Defrosting is thereby accomplished by passage of the hot gases through the

coils

20 and 13. In passing through the

coils

20 and 13, the hot compressorgases will push through the coils liquid refrigerant which remains in the coils at the end of the refrigeration cycle. Also, to some extent the hot gases themselves may be condensed. This liquid refrigerant passes, along with the gases, through the conduit 32 to the accumulator vessel 33, which serves as a the evaporator coils 13 and the heat exchanger 36, only vapor can reach the heat exchanger.

Hence, liquefied refrigerant cannot reach' the compressor; only vapor can reach it. This vapor is effectively heated in. the heat exchanger 36 by heat interchange with the hot compressor gases. An ample supply of vapor for the compressor is assured by reason of the body of liquid refrigerant in the accumulator vessel '33 and' in the receiver 12'. Both of these vessels are in communication with the vessel 35 during the defrosting cycle, and provide an. ample supply of vapor. The heat interchange between incoming vapor and outgoing hot gases in the'heat' exchanger prevents supplying any liquid refrigerantto the compressor.

At the conclusion of the defrosting cycle, the solenoids 46 and 49 will be tie-energized and the valves 45 and 438 will assume their normally closed positions to restore the system to normal refrigerating conditions.

Referring now to Figure 2, in which parts similar to those in Figure l are similarly numbered;.a modified form of defrosting system is illustrated which is adapted for use with an existing refrigeration system. The. refrigeration system comprises a compressor 10,. a condenser 11, av receiver 12 and evaporator coils 13. Spent refrigerant is returned to the compressor through a conduit 32a containing a normally open valve 60 which is closed only when a solenoid 61 is energized through leads .62. A separate defrosting system is provided which is generally designated as 65. This defrosting system comprises an accumulator vessel 33 and a heat exchanger 36, as in the case of the defrosting system of Figure l and, as in the case of Figure l, the heat exchanger includes an outer vessel 35 and an inner vessel 39. This system is connected with the refrigeration system in the-following manner: The outlet conduit 14 f the compressor 10 is connected through a conduit 66 and a normally closed valve 67 to the bottom of the inner vessel39. The valve 67 is opened by a. solenoid 68 when the latter is energized through leads 69'. A hot gas line 46 connects the upper end of the inner vessel 39 tothe drip pan coils 2.0 and the evaporator coils 13, and the outlet end ofthe evaporator coils 13 is connected through a conduit 32 to the accumulator vessel 33. The upper end of. the accumulator vessel 33 is connected through a. conduit 34 containing a hand valve 70 to the outer vessel 35 and the bottom of the accumulator vessel 33 is connected through a conduit 71 and an expansion valve 72 to a nozzle '73 which is so located as to spray fluid onto the outer surface of the inner vessel 39. A conduit 74 connects the outer vessel 35 with the inlet of the compressor 10.

In operation the refrigeration system will operate in essentially the manner as described above with reference to Figure l; i. e., hot compressed gases from the compressor will pass through the conduit 14 into the condenser 11 and the condensed refrigerant will pass through the conduit 15 to the receiver 12, thence through the conduit 16 and expansion valve 17 into the evaporator coils '13. However, instead of returning to the compressor through the defrosting system asin the system of Figure 1, the spent refrigerant will return directly to the compressor through the conduit 32a.

At predetermined intervals, in accordance with the setting of a time switch (not shown), the solenoids 61 and 68 will be energized to close the valve 60 and open the valve 67. Hot gases from the compressor will then pass through the conduit 66 to the inner vessel 39 of the heat exchanger 36 and will then pass through theconduit 40 to thedrippan coils'2tl' and the evaporator coils 13.

4 Liquid refrigerant and spent gas or vapor from the evaporator coils 13 will pass through the conduit 32' to the accumulator vessel 33. Vapor from the upper end of the accumulator vessel 33 will pass through the conduit 34 to the outer vessel 35 of the heat exchanger 36 and will be heated therein by the hot gases in the inner vessel 39. The warm vapor will then pass through the conduit 7 4 to the inlet of the compressor 10.

Liquid refrigerant. in the accumulator Vessel 33 will pass through the conduit 71, will be expanded by the expansion valve 72 and will be sprayed by the nozzle 73 against the warm outer surface of the inner vessel 39. Liquid thus transferred from the accumulator vessel 33 to the heat exchanger will be instantly vaporized by the hot gases in the inner vessel 39 and the vapor will be drawn through the conduit 74 into the inlet of the compressor 10. There is an important advantage in this mode of operation, which can be explained as follows: As is well known, in the operation of a refrigeration system the lubricant employed to lubricate the cornpressor'will find its way into the evaporator coils. When hot gas is introduced into the coils during, defrosting, it will push the lubricant from these coils along with liquid refrigerant. An efiicient re-evaporator will evaporate the liquid refrigerant but it will not evaporate the lubricant, because its vapor pressure is much lower than that of the refrigerant. It is highly undesirable to return liquid lubricant to the suction line of the compressor; slugging and other undesirable results will occur. Heretofore it has been a common practice to collect lubricant in a trap and return it to the crankcase of the compressor. 7 i

The: expansion: valve 72 and the nozzle 73 shown in Figure 2 provide a means for returning lubricant to the compressor without slugging and without using a lubricant trap.

As explanied above, when the liquid refrigerant is sprayedonto the warm outer surface of the inner vessel 39, it is instantly vaporized: By reason of this instant vaporization or flashing of liquid refrigerant, and by reason of spraying the liquid refrigerant and entrained compressor lubricant, the lubricant is necessarily atomized and finely dispersed in the refrigerant vapor. The resulting fine dispersion of liquid lubricant in refrigerant vapor is then supplied to the suction line of the cornpressor without the above-mentioned difficulties and without'th ecessity of using a lubricant'trap.

After installation ofthe defrosting system of Figure" 2, the hand valve 70' will be adjusted manually until the defrosting system is operatingproperly. Thereafter, further adjustment of valve 70 is unnecessary eXcept' occasionally.

It willthus be apparent that a defrosting system has been provided which is effective to defrost evaporator coils. of an automatic refrigeration unit by the action of the hot gases from the compresson. In one of its forms, this defrosting. systeniis adapted to. installation as an integral part of a refrigeration system; In another form it is adapted to installation as a separate unit in an existing refrigeration unit. The defrosting system of the present invention obviates certain disadvantages which have been encountered in previous hot gas defrosting systems. Thus, the necessity of maintaining and heating a body of liquid is obviated. Also an ample supply of vapor for the compressor is assured at'all times. The defrosting s. stem vof the ,presentinvention is simple to install and to operate and it is dependable in its operation. V

Iclaim;

1. In apparatus ofthe character descri'bed comprising a closed refrigeration system including a compressor, a condenser, and an evaporator. and a closed hot. gas defrosting system for periodicallivlby-passing. thec ndenSer and circulating hot gas from compressor to the evaporator, thence back to. the compressor, the improvement which comprises: an accumulator vessel. for receiving refrigerant. from the evaporator during the defrosting cycle and for storing liquid refrigerant so. received; and heat exchange means interposed. between the accumulator vessel and the compressor for receiving refrigerant from the accumulator vessel and heatingit by heat transferred from hot gas from the compressor during the defrosting cycl an mean in rconn ctings i accumulator v l and'hcat exchange .m ans;lsa;id accumulatorv sel hav s a capacitysufficient to receive and entrap the entire'volume of liquid contained in the evaporator at the commencement of the defrosting cycle; said interconnecting means being such as to prevent the passage of continuous liquid phase from the accumulator vessel into the heat exchange means but to permit passage of vapor or or finely dispersed liquid from the accumulator vessel into the heat exchange means.

2. In apparatus of the character described comprising a closed refrigeration system including a compressor, a condenser and an evaporator and a closed hot gas defrosting system for periodically by-passing the condenser and circulating hot gas from the compressor to the evaporator, thence back to the compressor, the improvement which comprises: an accumulator vessel for receiving refrigerant from the evaporator during the defrosting cycle and for storing the entire volume of liquid contained in the evaporator at the commencement of the defrosting cycle; heat exchange means interposed between the accumulator vessel and the compressor for receiving refrigerant from the accumulator and heating it by heat transferred from hot gas from the compressor during the defrosting cycle; and means for transferring vapor from the accumulator vessel to the heat exchanger, such means preventing passage of continuous liquid phase from the accumulator vessel into the heat exchanger.

3. A refrigeration system comprising a compressor, a condenser, a receiver and an evaporator and means connecting the said elements to provide a closed refrigeration system; and a closed, hot gas defrosting system for periodically by-passing the condenser and circulating hot gas from the compressor to the evaporator, thence back to the compressor; said hot gas defrosting system comprising an accumulator vessel for receiving refrigerant from the evaporator during the defrosting cycle and for storing liquid refrigerant so received; a heat exchanger interposed between the accumulator vessel and the compressor for receiving refrigerant from the accumulator and heating it by heat exchange with hot gas from the compressor; and means connecting the receiver with the heat exchanger to supply vaporized refrigerant thereto during the defrosting cycle, said means comprising a conduit providing such connection and an automatic valve in said conduit which is closed during the refrigeration cycle and open during the defrosting cycle.

4. A refrigeration system comprising a compressor, a condenser, a receiver and an evaporator and means connecting said elements to provide a closed refrigeration system; and a hot gas defrosting system therefor, said defrosting system comprising an accumulator vessel, a heat exchanger comprising a first vessel for receiving hot gases and a second vessel for receiving cold refrigerant, means connecting the outlet of the evaporator with said accumulator, means connecting accumulator with said second vessel to supply cold refrigerant vapor thereto, means connecting said second vessel with the inlet of said compressor, means connecting the outlet of the said compressor with said first vessel, means connecting said first vessel with the inlet of said evaporator, and means connecting said receiver with said second vessel for supplying vaporized refrigerant thereto.

5. A hot gas defrosting system comprising a compressor having an outlet for hot compressed gas and an inlet, an evaporator for evaporating condensed refrigerant, a heat exchanger, an accumulator vessel having a capacity suflicient to receive and entrap the entire volume of liquid contained in the evaporator at the commencement of the defrosting cycle; said system also comprising a defrosting circuit for conducting hot gas during the defrosting cycle from the compressor outlet through the heat exchanger to the evaporator, for passing spent vapor and liquid expelled from the evaporator to said accumulator, for passing refrigerant vapor from the accumulator to the heat exchanger Without passing continuous liquid phase thereto, and for passing refrigerant vapor from the heat exchanger to the compressor inlet.

6. A hot gas defrosting system comprising an accumulator vessel for receiving spent vapor and liquid refrigerant from the evaporator of a refrigeration system, a heat exchanger comprising inner vessel and an outer vessel in heat exchange relation, means for supplying hot compressed gas to said evaporator through said inner vessel, means for returning spent vapor and liquid refrigerant from the evaporator to said accumulator vessel, means for conducting liquid refrigerant from said accumulator vessel to said outer vessel and for spraying same on the surface of said inner vessel, and means for conducting heated refrigerant vapor from said outer vessel to said compressor.

7. A refrigeration system comprising a compressor, a condenser, a receiver and an evaporator and means connecting' said elements to provide a closed refrigeration system; and a hot gas defrosting system therefor, said defrosting system comprising an accumulator vessel having a capacity sufiicient to receive and entrap the entire volume of liquid contained in the evaporator at the commencement of the defrosting cycle, a heat exchanger comprising a first vessel for receiving hot gases and a second vessel for receiving cold refrigerant, means connecting the outlet of the evaporator with said accumulator, means connecting the accumulator with said second vessel to supply cold refrigerant vapor thereto Without supplying continuous liquid phase thereto, means connecting said second vessel with the inlet of said compressor, means connecting the outlet of the said compressor with said first vessel, and means connecting said first vessel with the inlet of said evaporator.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,970,340 Ruff Aug. 14, 1934 2,430,960 Soling Nov. 18, 1947 2,440,146 Kramer Apr. 20, 1948 2,526,379 Maseritz Oct. 17, 1950 2,564,310 Nussbaum et a1. Aug. 14, 1951 2,611,587 Boling Sept. 23, 1952 2,632,303 Smith Mar. 24, 1953 2,641,908 La Porte June 16, 1953