US2693678A

US2693678A - Automatic defrosting system

Info

Publication number: US2693678A
Application number: US277555A
Authority: US
Inventors: Toothman Earl
Original assignee: EDWARD A DANFORTH
Current assignee: EDWARD A DANFORTH
Priority date: 1952-03-20
Filing date: 1952-03-20
Publication date: 1954-11-09
Anticipated expiration: 1971-11-09

Description

Nov 9,

Filed March 20, 1952 E. TOOTHMAN AUTOMATIC DEFROSTING SYSTEM 2 Sheets-Sheet l Condenser Receiver INVENTOR. Ear/ 7&0 fhman :EIlzzl Nov. 9, 1954 E. TOOTHMAN I 2,693,678

AUTOMATIC DEFROSTING SYSTEM Filed March 20, 1952 2 Sheets-Sheet 2 IN VEN TOR. Ear/ Toofhman United States Patent Office AUTOMATICDEFROSTINJG SYSTEM.

Earl 'To'othman, San Francisco, -Calif.-,-I assignorcof- .one half to Edward- A. Danforth; Palo'Alto, Calif.

ApplicatioirMarch 20, 1952,.Se'rialrNo. 277,555:

5. Claims. .(Cl.62-1-3),

up'or'frost owing to'condensation and freezing ofiwater vapor in the atmosphere:

Several defrosting systems have .beensuggested, and

someof themtare' currently employed for automatically defrosting the evaporator. coils: One type;- of automatic defrosting system employs the hot; compressed "gases" front thecompressorzas a source of heat to heat the coils.v For this purpose by-pass: means are provided for bypassing the condenseif'and conductingthe hot gases'to azheat storage :reservoir or directlyito' the. evaporator coils; Therby pass'means includessuitablevalves, solenoids: for operating the same. and electrical'timing means fox-"operating the solenoids. at predetermined intervals.

Certain difi'iculties or'disadvantages have been encountered in'the installation and/or" operation of prior automatic, hot' gas defrosting system's; In one" suchsystem, duiingtherefrigeration cycle hot ga's'xfrom' the compressor is passed through a heat storagevessel or reservoir containing a .body .of liquid. The hot'ga s heatsthe liquid, and this heat is employedduring .the' defrosting cycle to"vaporizeliqu id froma'the evaporator coils. In this 'sys tem;'the liquid, 'which'constitutes the heatstoragexmediunr, is. cooled very rapidly duringthe defrost.- ing cycle, so much so that'the. liquid from .the evaporator coiis'is l not fully vaporized.

In another systemya :directheat' exchange is provided during the defrosting cycle, between. the hot gas from. the compressor'and the cold Iiquidfrom the evaporatorcoils. However; 'in-thissystem; no provisionis made for storage of' liquid from the evaporatorcoils during the defrosting. cycle. Tliexrefrigerantpasses directly'irom the evaporatorzcoilsi. to the compressor; As a result, thesupply. of. vapor in the suction line of the-compressor is. likely. tobexhausted and, when this occurs; the compressor will. simply pump liquid to .the evaporator coils.

lntmyco-pendin'g' application .above referred to, animproved: type of: defrosting; system is. describedand claimed which employshot gas, which'is automatic and WhlCh h8 .S"C111IaiHI important advantagesover vprior defrosting systems.

It is.an.object of the present invention to provide. an automatic hot gas .defrostin'g. system which is. generally similarto that ofmyaforesaid co-pending application but whichxis superiorthereto';

Iti'sra further objectof the presentinventionto.provirle an .automatic hot. .gas defrosting system which 'tl S generally tosthat. of..the .aforesaid 'co.-.pending application but which'has certainnadvantageous adjustment. features;

Another. object ofthe present invention is tO..PI'OVld a hot gas. defrosting system which will'idefrost. evaporator coils'imore: quickly, and which. will. evaporate liquid: refrigerant .removed from evaporator. coils. more. quickly, than'..tl'1e. .defrosting .tsystem of said co-pending .rapplicanon...

Yet another object of the invention is to provide a hot gas defrosting system wherein, during the defrosting cycle, a selected, adjustable portion of-the hot gas from the compressor is' employed to heatthe fluid returning from the evaporator coils to the compressor, and whereinan adequate back pressure is maintained on the evaporator coils and an adequate gas supply and pressure are maintained in thesuction line of the compressor.

These and other objects of the invention will. be apparent from the ensuing description and appended claims.

Certain forms of the inventionare illustrated by way of example in the accompanyingdrawings and are described in detail hereinafter.

In the drawings,

Figure 1 is a more or less diagrammatic view of a refrigeration system including automatic. hot, gas de.-' frosting means constructed 'inaccordahce with the invention.

Figure 2 is a fragmentary view of the system of-Figure 1 showing the piping. and valve arrangement. employed to proportion the amount of 'hot gas which is,routed through the heat exchanger.-

Referring now to Figure l, a refrigeration systemgis there shown which comprises the usualcompressor 10, condenser 11, receiver 12, and evaporator'coils 13.. During normal operation of the system'a suitable gas, such as ammonia or Freon, 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 con-. duit 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 feeler1bulb (not shown), may be employed to operatehthe expan-. sion valve so as to maintain suitable refrigeration conditions; Drip pan .coils 20 are also. provided, as is a fan driven by a motor 31 forcirculating air over the coils.

The expanded gas from the coils, which may be partly liquefied, is returned to the compressor through a conduit 32 which, as in my aforesaid co-pendingapplication, leads to an accumulator vessel 33. The accumulator vessel 33 is provided witha gauge 34 and with an outlet conduit 35 which is" connected through a. conduit 36 with the inlet of the compressor 10. A valve 37 is provided in the conduit 36 which is controlled by a solenoid 38. A conduit 39 containing a manual ad-. justing valve 40 provides a connection between the accumulator 33 and a heat exchanger 45.

The heat exchanger is,a multiple gcharnber vessel comprising an outer vessel, 46, an intermediate vessel 47 and an inner vessel 48. The outer. vessel 46' and the intermediate vessel 47 form an annular chamber 49;, the intermediate and

inner vessels

47 and 48 form an annular chamber. 50; and theinner vessel 48 providesan. inner chamber 51.. The chambers49, '50 and 51 are sealed one from the other so that the only. meansof ingress; and. egress is through the piping herein described. The annular chamber 50' is provided with. baflies 52v which extend from the top to near the bottom.

The severalchambers of the heat exchanger 45 are connected with the remainder of my system .in the following manner; As stated, the accumulator .vessel 33 is connected through

conduits

35 and 39 and a valve 40 with the heat exchanger 45.. The conduit 39 connects withthe outer chamber 49 near its bottom at one side. A conduit 36a connects the upper end and opposite side of outer chamber 49 with the suction conduit 36, at a point betweenthe valve 37 and the compressor 10; A conduit 53 is provided which contains a hand valve. 54 and which connects the bottom of accumulator .vessel 33-with the bottom of inner chamber 51. As willbe seen, the lower end of conduit.53 within chamber 51- is formed with openings 55. A conduit 56 is provided which connects the upper. end of inner chamber 51 with corn duit 39, hence with outer. chamber. 49'.

A hot gas line 63 is provided which contains .a normally closed valve 66 which is openedwhen asolenoid-67. is energized. The hot gas-.tline is broken away at163a to indicate a piping arrangement=which vis described herein- PatenteiNom. 9,. 1 9.54-

below with reference to Figure 2. Beyond the point 63a, the hot gas line connects with drip pan coils 20, thence through a conduit 68 and a check valve 69, with the evaporator coils 13, as illustrated.

A conduit 64 containing a hand valve 64a connects the hot gas line 63 with intermediate chamber 50 of heat exchanger 45, and a conduit 65 connects the chamber 5'!) with the hot gas line 63 beyond the point 63a. As will be seen, the

conduits

64 and 65 are located on opposite sides of the baffles 52 and near the top of chamber 50. Hence, hot gas diverted through the chamber 50 must travel downwardly substantially the full length of the chamber, thence upwardly on the opposite side of the baffies 52.

Referring now to Figure 2, in which the heat exchanger 45 is shown in plan view, piping 63a is shown as connecting the two branches of hot gas conduit 63. The piping 63a comprises Ts at 70, elbows at 71 and straight runs of pipe as illustrated. In a specific installation, of course, this piping arrangement can be varied from that shown. The important consideration is that the piping 63a be such that, with the valve 64a wide open, the path of least resistance between the two branches of hot gas line 63 is through conduit 64, chamber 50 and conduit 65. Hence, by adjusting valve 64a, any desired gropstartion of the hot gas can be routed through cham- Suitable electrical controls are also provided. Thus a time switch 80 is provided having four

terminals

81, 82, 83 and 84. Power leads 85 and 86 are provided which are connected to terminals 81 and 82, respectively. The fan motor is connected to power lead 86 by means of a lead 87 and to terminal 84 by a lead 88. The solenoid 38 is connected to power lead 86 and is connected by a lead 89 to terminal 84. Solenoid 67 is connected to power lead 86 and is connected to terminal 83 by a lead 90.

The time switch 80 is, of course, provided with a clock or other timing mechanism (not shown) which is connected to the terminals 81 and 82 and which is adjusted to initiate and terminate the defrosting cycle at regular intervals. During the refrigerating cycle, terminals 81 and 84 are connected so as to energize the fan motor 31 (which operates fan 30) and the solenoid 38 (which maintains valve 37 in open condition). Terminals 81 and 83 are not connected. hence solenoid 67 remains de-energized and valve 66 remains closed during the refrigeration cycle. At the commencement of the defrosting cvcle, terminals 81 and 83 are connected and terminals 81 and 84 are disconnected. Hence valve 37 is closed and fan 30 is stopped. Solenoid 67 is energized and opens valve 66.

In operation the system thus described functions as follows: During the refrigerating cycle, valve 66 will be closed and valve 37 will be open. Gaseous refrigerant is compressed in the com ressor and is passed via conduit 14 to condenser 11 wherein it is cooled and condensed to the liquid state. Liquid refrigerant is passed to receiver 12 through conduit 15 and is stored in the receiver. Thence. it passes via conduit 16 and expansion valve 17 to header 18, thence through evaporator coils wherein it evaporates and cools the surrounding environment. Thence, the gases, which may contain entrained liquid, pass via header 18 and conduit 32 to accumulator vessel 33. Thence, the gases pass through

conduits

35 and 36, and through the open valve 37, to compressor 10, thus completing the circuit.

At regular intervals, in accordance with the setting of time switch 80, the solenoid 38 is de-energized so as to close valve 37 and the solenoid 67 is energized so as to open valve 66. Also, the fan motor 31 is stopped. This commences the defrosting cycle, which is as follows:

Hot gas from the compressor passes through the first or nearer branch of line 63 and divides at the first T 70. A portion of the hot gas passes through the piping 63a and the remainder passes through conduit 64, intermediate chamber 50 and conduit 65. The two portions recombine at the second T 70 and proceed to the drip pan coils and evaporator coils 13, where they accomplish defrosting. The fluid from the evaporator coils, which consists of both gas and liquid, passes through conduit 32 to accumulator vessel 33. Liquid refrigerant accumulates in the bottom of the vessel 33 and is indicated as 33a.

A suitable back pressure is maintained on the coils 13 by means of valve 40, which admits gas from the vapor space 33b in vessel 33, through conduit 39, to

4 outer vessel 49 of heat exchanger 45. This gas is, of course, heated by heat interchange with hot gases bypassed through the intermediate chamber 50. In addition to the gas so introduced with chamber 49, a further quantity of gas is introduced in the following manner:

Liquid 33a from vessel 33 is conducted through conduit 53 and is sprayed through holes 55 into inner chamber 51 of heat exchanger 45. The amount of liquid sprayed into chamber 51 is controlled by means of valve 54. The liquid refrigerant sprayed into chamber 51 is heated and vaporized by heat interchange with hot gas in intermediate vessel 50. The resulting vapor or gas is conducted via conduit 56 and conduit 39 to outer chamber 49. All of the gas from chamber 49 is conducted through conduit 36a to conduit 36, thence to 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, lubricant employed to lubricate the compressor will find its way into the evaporator coils. Whenv hot gas is introduced into these coils during defrosting it will push the lubricant from the evaporator along with the liquid refrigerant. An efiicient heat exchanger or re-evaporator will serve to re-evaporate the liquid refrigerant but it will not evaporate the lubricant because its vapor pressure is much lower than that of the refrigerant. Yet it is highly undesirable to return liquid lubricant to the suction line of the compressor; slugging and other undesirable results will occur. This problem has been attacked heretofore by separating the lubricant from the refrigerant vapor by means of a trap, and returning the entrapped lubricant to the crankcase of the compressor.

The valve 54 and the holes 55 shown in Figure 1 provide a means of returning lubricant directly to the suction of the compressor without slugging, and they avoid the necessity of a trap and of returning lubricant to the crankcase. As explained above, the liquid refrigerant is sprayed into the chamber 51 and is heated and vaporized therein by heat interchange with hot gas in the intermediate vessel 50. Under these conditions the liquid refrigerant is rapidly vaporized or flashed, and the compressor lubricant is necessarily atomized and finely dispersed in the refrigerant vapor. The resulting fine dispersion of liquid lubricant in refrigerant vapor can then be supplied directly to the suction line of the compressor without slugging and without the necessity of trapping the lubricant and returning it to the crankcase of the compressor.

At the commencement of operation of my hot gas defrosting system, certain adjustments will be made. Thereafter it will not, ordinarily, be necessary to make adjustments except at long intervals of time. Initially, the valve 40 will be adjusted to provide a suificient back pressure in the coils 13; i. e., a sufficient pressure, hence a sufficient temperature to accomplish defrosting in the desired period of time. The valve 54 will be adjusted to maintain a sufficient pressure in the outer chamber 49 and suction line 36, to supply the compressor 10 with an adequate flow of gas. Thevalve 64a will be adjusted to accomplish substantially completely vaporization of liquid in

chambers

49 and 51 and to prevent liquid from reaching the compressor 10. It will be understood, of course, that the gauge 34 on accumulator vessel 33, and a gauge (not shown) communicating with chamber 49 will be observed to assist in the regulation of valves 40, 54 and 64a. will be adjusted to initiate and maintain the defrosting cycle at a frequency and for a duration sufiicient to accomplish the intended defrosting job without heating the interior of the refrigerator.

It will be apparent that the control valves 40, 54 and 64a and the time switch are interdependent and that and a single defrosting system of my invention may be used with several sets of coils, defrosting the same simultaneously. Or a smgle compressor and a defrosting The time switch 80- system for each set of coils may be used, in which case the coils could be defrosted successively.

In any given case, the accumulator vessel is preferably designed to have a capacity equal to that of the coils which are being defrosted, so that there is no likelihood of liquid reaching the suction line of the compressor.

It will, therefore, be apparent that a defrosting system has been provided which is simple, automatic and reliable in its operation and which is effective to defrost evaporator coils in a short period of time and to completely gasify the liquid refrigerant from the coils.

I claim:

1. A hot gas defrosting system comprising a heat exchanger including a hot gas compartment, a liquid refrigerant compartment and a spent gas compartment, said hot gas compartment being in heat exchange relation with said liquid refrigerant and spent gas compartments; said system also comprising a receiving vessel, a compressor and an evaporator, means for conducting hot gas from the compressor to the evaporator and for conducting at least a portion thereof through said hot gas compartment during the defrosting cycle, means for conducting spent gas and liquid refrigerant from said evaporator to said receiving vessel, means for conducting spent gas from said receiving vessel through the spent gas compartment to the compressor, means for conducting liquid refrigerant from the receiving vessel into the liquid refrigerant compartment to cause evaporation thereof, and means for conducting vaporized refrigerant from the liquid refrigerant compartment to the spent gas compartment.

2. A hot gas defrosting system comprising a heat exchanger including concentrically arranged hot gas, liquid refrigerant and spent gas compartments, said compartments being arranged with the spent gas compartment outermost, the liquid refrigerant compartment innermost and the hot gas compartment intermediate said other compartments; a receiving vessel; means for conducting hot gas from a compressor to an evaporator and for diverting at least a portion thereof through the hot gas compartment during the defrosting cycle; means for conducting spent gas and liquid refrigerant from the evaporator to the receiving vessel; means for conducting spent gas from the receiving vessel to said spent gas compartment; means for conducting liquid refrigerant from the receiving vessel to said liquid refrigerant compartment; means for conducting vaporized refrigerant from the liquid refrigerant compartment to the spent gas compartment; and means for conducting vaporized refrigerant and spent gas from the spent gas compartment to the compressor.

3. A hot gas defrosting system comprising a heat exchanger including concentrically arranged hot gas, liquid refrigerant and spent gas compartments, said compartments being arranged with the spent gas compartment outermost, the liquid refrigerant compartment innermost and the hot gas compartment intermediate said other compartments; a receiving vessel; means for conducting hot gas from a compressor to an evaporator and for diverting at least a portion thereof through the hot gas compartment during the defrosting cycle; means for conducting spent gas and liquid refrigerant from the evaporator to the receiving vessel; means for conducting spent gas from the receiving vessel to said spent gas compartment; means for conducting liquid refrigerant from said receiving vessel and spraying it into said liquid refrigerant compartment; means for conducting vaporized refrigerant from the liquid refrigerant compartment to the spent gas compartment; and means for conducting vaporized refrigerant and spent gas from the spent gas compartment to the compressor.

4. A hot gas defrosting system comprising a compressor and an evaporator, means for supplying hot gas from the compressor to the evaporator and means for conducting spent gas and liquid refrigerant from the evaporator; a receiving vessel for receiving said spent gas and liquid refrigerant; a heat exchanger including a hot gas compartment, and also a liquid refrigerant compartment and a spent gas compartment in heat exchange relation with said hot gas compartment; means including a valve for diverting a portion of the hot gas supply from the compressor through said hot gas compartment during the defrosting cycle, said valve being adjustable to control the proportion of hot gas so diverted; means including an adjustable back pressure. valve for conducting spent gas from said receiving vessel to said spent gas compartment; means including an adjustable valve for conducting liquid refrigerant from said receiving vessel to said liquid refrigerant compartment; means for conducting vaporized refrigerant from said liquid refrigerant compartment to said spent gas compartment; and means for conducting the combined spent gas and vaporized refrigerant from said spent gas compartment to said compressor.

5. A hot gas defrosting system comprising a compressor and an evaporator, means for supplying hot gas from the compressor to the evaporator and means for conducting spent gas and liquid refrigerant from the evaporator; a receiving vessel for receiving said spent gas and liquid refrigerant; a heat exchanger including a hot gas compartment, and also a liquid refrigerant compartment and a spent gas compartment in heat exchange relation With said hot gas compartment; means including a valve for diverting a portion of the hot gas supply from the compressor through said hot gas compartment during the defrosting cycle, said valve being adjustable to control the proportion of hot gas so diverted; means including an adjustable back pressure valve for conducting spent gas from said receiving vessel to said spent gas compartment; means including an adjustable valve for conducting liquid refrigerant from said receiving vessel and spraying the same into said liquid refrigerant compartment; means for conducting vaporized refrigerant from said liquid refrigerant compartment to said spent gas compartment; and means for conducting the combined spent gas and vaporized refrigerant from said spent gas compartment to said compressor.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,246,244 Consley June 17, 1941 2,564,310 Nussbaum et a1 Aug. 14, 1951 2,611,587 Boling Sept. 23, 1952 2,632,304 White Jr Mar. 24, 1953 2,641,908 La Porte June 16, 1953