US2255588A - Method of heat transfer - Google Patents

Description

Sgpt. 9, 1941.

- E. F. HUBACKER METHOD OF HEAT TRANSFER Filed April 27, 1939 4 Sheets-Sheet 1 [NVENTOR ATT NEY Sept- 9, 1941- E. F. HUBACKER 2,255,588

METHOD OF HEAT TRANSFER Filed April 2'7, 1939 4 Sheets-Sheet 2 /NVENTOR far] 7. fluZacZer.

BY I M*MO\RNEV E. F. HUBACKER METHOD OF HEAT TRA NSFER.

Sept. 9, 1941.

Filed April 27, 1959 -4 Sheets-Shgei 3 INVENTOIR Z Ffluiaaier:

BY Mg AWE/ZQDRNEY Se t. 9, 1941. E. F. HUBACKER METHOD OF HEAT TRANSFER 4 Sheets-Sheet 4 Filed April 27, 1959 INVENTOR Z 47; Ffizziacier: BY M65 Patented Sept. 9, 1941 METHOD OF HEAT TRANSFER Earl F. Hubacker, Highland Park, Mich, assignor to Borg-Warner Corporation, Chicago, 111., a corporation of Illinois Application April 27, 1939, Serial No. 270,296

4 Claims. (Cl. 62178) This invention relates to the art of refrigeration and has reference to improved methods of and apparatus for heat transfer which are par-' ticularly useful in providing different temperature and humidity conditions within different compartments at the same time.\

This application is a continuation, .in part, of my prior application Serial No. 179,249, filed December 11, 1937, for Method of and apparatus for heat transfer, which in turn is a continuation, in part, of an application filed December 30, 1935, Serial No. 56,625, for Method of and apparatus for heat transfer.

A principal object of the invention is to provide an-improvement in the art of refrigeration by means of which refrigeration at different temperatures may be produced simultaneously.

Another object of the invention is to provide a new and improved form of evaporator construction which is adapted to refrigerate simultaneously at different temperatures.

Another object of the invention is to provide a novel and improved refrigerating system including an evaporator which comprises a plurality of separated sections so arranged that a refrigerant body or medium, comprising a plurality of liquid components, or a plurality of different refrigerants having different boiling points is exposed to substantially the same suction pressure in each of the sections in a definite order, as a result of which refrigeration is produced in each of the sections at a temperature different than that of the other sections.

Another object of the invention is to provide in a refrigerating system, an evaporator having one section wherein refrigeration at a low temperature is produced and another section wherein refrigeration at a different temperature is produced.

Another object of the invention is to proi'iide a novel form of heat transfer system wherein there is employed a liquid heat transfer or refrigerating medium which comprises a mixture or solution of'at least two refrigerants, said solution or mixture having a different boiling point than either of its components.

Another object of the invention is to provide a refrigerating system which is provided with a two-part evaporator, the liquid refrigerant mixture or solution in each of which part being exposed to substantially the same suction pressure, and the mixture or solution of refrigerants being of such a character that in one part of the evaporator the same boils or evaporates at a lower temperature than that at which'the mixture or solution boils in the other part of the evaporator.

Another object of the invention is to provide in a refrigerating system .an evaporator which will operate to produce refrigeration at two different temperatures.

Another object of the invention is to provide a new and improved form of refrigerator constructionhaving a plurality of refrigerated zones,

- each zone having different temperature and relative humidity conditions than those of the other zones.

Another object of the invention is to provide a novel process of refrigeration by means of which refrigeration at a plurality of different temperatures may be produced in a systemsimultaneously.

Another object of the invention is to provide new and improved forms of refrigerating apparatus which are useful generally in the refrigeration art and independently of the new and improved form of two-temperature refrigeration herein disclosed. v

As illustrated in the drawings, my invention is shown as being embodied in a refrigerating system and refrigerator of the so-called domestic type and which comprises in general a heat insulated compartment and a refrigerating system which includes two evaporators; one of the evaporators being arranged within the heat insulated compartment for cooling the air therein and the other of said evaporators being arranged within a second compartment within the heat insulated duce different temperature and humidity conditions in each of said compartments.

Another object of the'invention is to provide a new and improved form of refrigerating system which will operate to produce refrigeration at a plurality of, different temperatures simul taneously.

Another object of the invention is to provide a new and improved form of evaporator construction which has one part particularly designed for fast ice freezing and for thelow temperature storage of frozen foods and another part which is particularly designed for aircooling and is of such capacity and operated at such a temperature relative to the space to be cooled as to provide more favorable temperature and humidity conditions within-such space, for the storage of foodstuffs.

Another object of the invention is to provide a new and improved form of refrigerating system and refrigerant for use therein, so that said system will operate to produce'refrigeration at a plurality .of different temperature levels at the same time.

' Another object of the invention is to provide a new and improved form of two-temperature refrigerating system, which is simpler in construction, more efficient in operation, more dependable in operation, and less expensive to build than two-temperature systems of the type heretofore known to the art. I

Another object of the invention is to provide a newv and improved form of evaporator contofore used. 1

Another object of the invention is to provide condenser 23 arranged within the apparatus compartment 24 and operatively connected to a pairof evaporators 30 and 32 arranged within the compartment 20. The discharge side of the compressor is connected to one end of the conbe supplied to the motor through an electric conduit 34 adapted for attachment to an ordinary electric receptacle. The supply of current to the motor is under the control of a suitable thermostatic switch as willbe explained hereinafter.-

. ranged in the upper left-hand corner of the coma new and improved system for ice freezing and air cooling functions, and a new arrangement of the evaporators which perform such functions within a heat insulated compartment.

' Other objects and advantagesof the invention will be apparent from a consideration of the following specification taken in conjunction with theaccompanying' drawings of which there are four (4) sheets and wherein:

Fig. 1 is an elevational view of a household refrigerator withpartsbroken away and illustrating the application of my invention in conjunction therewith;

Fig. 2 is an enlarged front elevational view of the evaporator and the arrangement thereof relative to the space within the heat insulated compartment;

Fig. 3 is a side elevational view of the evaporator shown in Fig. 2;

Fig. 4 is a horizontal section taken in the plane on the line 44 of Fig. 3 looking in the direction of the arrows; I

Fig. 5 is a top plan view of the evaporator;

Fig. 6 is a vertical sectional view taken in a plane along the line 6-6 of vFig. 5 looking in the direction of the arrows;

Fig. 7 is a horizontal section taken in a plane along the line 'i'| of Fig. 6 looking in the direction of the arrows; I

Fig. 8 is a horizontalv section taken in a plane partment 20, and the evaporator 32 is arranged alongside of the evaporator 30. The evaporator .30, as will be more fully explained hereafter, comprises a low temperature or ice freezing evaporator which is constructed and arranged for operating at relatively low temperatures, for example, from 0 to 10 F. and is shielded from the circulating air within the compartment 20, to define a relatively low temperature or freezing zone.

along the line 88 of Fig. Blocking in the direc sulated compartment or relatively high temperature cooling zone 20, the opening I to which is closed by door 22, and an apparatus compartment. 24. Therefrigerator also includes, as illustrated,

the two evapo-.

The evaporator 32 is particularly'designed for air cooling and is constructed and arranged to operate at a temperature level of from 19 to 29 F., the area of the evaporator 32 exposedto the circulating air within the compartment 20 being suflicien't so as to produce a temperature within the compartment preferably of from 35 to 40 F. during the normal operation of the system.

Referring now to Fig, 10 wherein the refrigerant circulation of the two evaporators is illustrated, liquid refrigerant from the condenser and under the control of a suitable refrigerant expansion control is supplied to the low temperature evaporator 30 through liquid line 36 and vaporous refrigerant is retumed to the'intake side of the compressor from the evaporators through the suction line 38. The evaporator 30, as illustrated, consists of a plurality of refrigerated plates or shelves 42, 44 and 46, each shelf comprising a flat metallic plate having a coiled refrigerant duct 50 ingood thermal conductivity with the underside thereof. Liquid refrigerant is supplied to the coils or ducts 50 of the shelves 42, 44 and 46, in series, in-the order named, the refrigerant flow through the ducts 53 being in the direction indicated by the a trows. From the upper shelf 46 of the'low temperature freezer 30' refrigerant is' supplied.

ing evaporator comprises a finned plate evapo'-' rator exposed to the air within the provision compartment 20 and the details of the construca refrigerating system of the compressor-condenser-expander type and which system includes tion of which will be described hereinafter. The suction line 33 is connected to an upper header 54 of the'evaporator 32 for returning vaporous refrigerant and lubricant entrained therewith to the intake side of the compressor.

The evaporators 30 and 32, it will be observed. are connected in series and due to the fact that there are no restrictions or pressure regulating means between the two evaporators, refrigerant 3 in the coils or ducts of both of the evaporators a conipressonindicated generally at 26, and a 7 will be exposedtosubstantially the same suction pressure. Under these conditions, if a single refrigerant such as sulphur dioxide ($02) or any one of the F refrigerants now being marketed under the name Freon is used in the refrigerating system, as could be done, the evaporation of refrigerant would take placein both of the evaporators and in all parts .thereof at substantially the same temperature level. While a single refrigerant could be used in the arrangement illustrated, the present invention contemplates the operation of the evaporator 30 at a lower temperature level than the evaporator 32. One example of a means which may be employed to obtain the production of refrigeration at different temperature levels in the evaporators 30 and 32 is the use in the system of a refrigerant which consists of a solution or mixture of two or more refrigerant components such "as, for example, a refrigerant consisting of 80 to 90%, by weight, of (F-21) dichloromonofluoromethane (CHClzF) and to by weight, of (F-12 dichlorodifiuoromethane (CClzFz). Other examples of refrigerants comprising a mixture or solution of two or more refrigerant components suitable for use in the system herein illustrated and capable of effecting the operation of the evaporators at different temperature levels are:

Sulphur dioxide (S02) and trichloromonofiuoromethane (CClaF) (F-ll) Sulphur dioxide (S02) and dichloromonofluoromethane (CHClzF) (F-21) I Sulphur dioxide (S02) and dichlorotetrafluoroethane (C2C12F4) (F-114)' I Methyl chlorid (CHsCl) and dichlorodifiuoromethane (CC12F2) (F-12) Methyl chloride (CHsCl) and trichloromonofluoromethane (CClsF) (F-ll) Methyl chloride (CHsCl) and dichlorotetrafluoroethane (C2C12F4) (F-114) Methyl chloride (CH3C1) and dichloromonofluoromethane (CHClzF) (F-21) Dichlorodifluoromethane (CC12F'2) (F-l2) and trichloromonofluoromethane (CClsF') (F-ll) Dichlorodifluoromethane (CClzF-z) (F-12) and dichlorotetrafluoroethane (C2Cl2F4) (F-l14) In addition to the foregoing mixtures or solutions, other mixtures or solutions of two or more refrigerant components may be used. For further examples of mixtures reference may be had to my prior copending application Serial No. 179,249, filed December 11, 1937, for Method of and apparatus for heat transfer.-

Dichlorodifiuoromethane (CClzFz), trichloromonofluoromethane (CClsF) dichlorotetrafluoroethane (C2Cl2F4) and dichloromonofiuoromethane (CHClzF) chemically may be classified as fluorine derivatives of an aliphatic halogen compound, and are commercially referred to as F-12, F-11, F-114 and F-21, respectively.

Theoretically, if a mixture of approximately 20% of F-12 in F-21 at 10 lbs. absolute pressure is supplied to the low temperature evaporator 30, a shelf temperature of 10 F. ought to be produced. In the low temperatur evaporator 30, the F-12 will evaporate from the mixture or solution in a much larger concentration than 20% and will thereby reduce the concentration of F-12. The almost pure F-21 will then feed over through conduit 52 to the higher temperature evaporator 32 and at 10 lbs. absolute will vaporizeat approximately 25 F.

In actual performance, however, the evaporator, as illustrated, with a 20% concentration of F-12 entering the low temperature evaporator is something less than 20%.

the shelves, or low temperature evaporator 30,

will not produce a temperature of 10 F. at 10 lbs. absolute due to the fact that, first, the liquid refrigerant mixture supplied through the liquid line 36 must be reduced in temperature to the boiling temperature and this reduction in temperature is obtained by vaporizing a high concentration of F-12 so that the final concentration Second, in cooling more heat is added to the refrigerant mixture and the final temperature obtained is an average between the boiling point of the initial concentration and the concentration leaving the shelves. From actual experience it appears possible to obtain approximately one half of the theoretical spread.

The temperature spread between the evaporators 30 and 32, however, will vary materially with the heat load in the compartment 20 due to the fact that the available refrigeration per pound of mixture is constant, and since more refrigerant or mixture is circulated at higher loads, more refrigeration is available at the lower temperature level.

A greater temperature spreadbetween the evaporators 30 and 32 may be obtained by using a larger concentration of F-12, for example.

It appears desirable to operate the low temperature evaporator 30 at a temperature level of approximately 10 F. and the air cooling sec tion at a temperature of approximately 19 F.

In a system of this type, the addition of F-12 tends to increase the condenser head pressure and thereby increase the power input to the compressor. However, it has been found that in a well built compressor with low friction losses, the increase in head pressure increases the power input very slightly and there is a tendency for an overall gain in power consumption per day because the suction pressure increases slightly and both evaporators are somewhat more efflcient, due to the improved ebullition resulting with a quantity of refrigerant which is a mix-.

from the increased quantity of gas flowing through them, and, also, due to the extended surface provided by the fins on the air cooling evaporator.

The mixture just described of F-l2 and F-21 may be classified by what is commonly termed a normal boiling point mixture. In this mixture the boiling point is always between the boiling point of the pure constituents. In operation, a system such as the one illustrated is'charged ture or solution of a plurality of refrigerant components such as a 20% solution of F-12 in F-21. Where the evaporator comprises a plurality of sections or parts, as illustrated in the drawings, the refrigerant medium will operate to produce refrigeration at a lower temperature in the evaporator 30- than in the evaporator 32 because the refrigerant solution or mixture in the evaporator 30 will contain a different percentage of the components of the refrigerant than the solution or mixture which vaporizes in the evaporator 32. As the solution in the evaporator 30 will boil at a lower temperature than the solution in the evaporator 32, there will be a temperature diflerential or spread between the evaporators 30 and 32.

The refrigerant medium in circulating through the system is discharged from the compressor into the condenser where condensation of all of the vaporousrefrigerant takes place, and is thence conducted, under the control of a refrigerant expansion control, to the low temperature evaporator 38 wherein a part of the solution or Y nent in it than is present in the mixture or solution in the evaporator 38. The liquid refrigerant discharged into evaporator 32 has a higher boiling point than the boiling point of the solution in the evaporator 38, and, hence, will boil at a higher temperature. Therefore, it is apparent that refrigeration at a lower temperature level will be produced in the evaporator 38 than in the evaporator 32.

. The vaporous refrigerant from both of the evaporators 38 and 32 will collect in the upper part of the header 54 from whence suction line 38 conducts such refrigerant vapor together with whatever lubricant may be entrained therein to the intake side of the compressor. The average composition of the gas passing through the suction line should always be the same as the average compositionof the liquid entering evap-" orator 38 through liquid line 36.

The-details of construction of the two evaporators are illustrated in Figs. 2 to 9, inclusive, and to which figures reference will now be made. The inner wal'l'or lining of the compartment 28 may be provided by a sheet metal milk so terminating at its 'front in a flat face 62 upon which a breaker strip or throat lining 64 is seated. The breaker strip. 64 extends continuously around 1 v the door opening and is adapted to cooperate with agasket, carried by the door 22, for sealing the access opening to the compartment 28 when the door 22 is in closed position. An L-shaped partition 66 extending from the back wall of the compartment 28 to the'front thereof cooperates with the lining 68 at the upper left-hand corner of the compartment 28 to define a low temperaturecompartment 2| in which the evaporator 38'is disposed. 'The edges of the partition 66 may be provided with 'flanges 68 which seat against the flat surface of the tank 68 and are provided with bolt holes through which, and

aligned holes in the tank 68, bolts 18 extend for securing the partition 66 in place. Preferably a .gasket I2 is arranged between the flanges 68 and the wall of the tank 68 so as to provide a thermal'break therebetween, and also so as to effectively seal the compartment 2| around the edges thereof. A continuous rectangular metallic frame 14, covered by a continuous rubber gasket I6, is fitted at the front 'of the partition 66, and between the same and the opposite walls of the tank 68 defining the compartment 2| (as illustrated in Fig. 4) to define an access opening to the compartment 2|. The gasket 16 is arranged between the frame-I4 and the partition 66 at the bottom and the right-hand side of the compartment 2| and between the frame 14, andthe tank lining 68 at the top and left-hand side of the compartment 2| and, as illustrated in Fig. 4, thereby sealing theframe 14 to the walls of the compartment 2|. 1 The gasket I6 includes a, continuous hollow' bead I8 which cooperates with the edges of a-dished door member 88 to seal the interior'of the compartment 2| from the shelves 42, 44 and 46 of the low'temperature evaporator 38 may be bolted to vertical straps 98 and these straps in turnare bolted, or otherwise suitably secured, such as by bolts 82, to the tank lining 68 for supporting such shelves. The frame 14 also is bolted by bolts 94 to the tank lining 68 at the left-hand side and top thereof, and to the partition 66 at the right-hand side and bottom, for securing the same in place. Preferably, the straps 88 are spaced from the tanklining by gaskets 96 held in place by bolts 82. The right-hand side of the shelves 42, 44

and 46, at the front and rear thereof, are connected to the partition 66 so as to be supported thereby and through insulating links 98. A false bottom I88 may be provided insideof the compartment 2 I and supported upon the horizontal portion of the partition 66 so as to provide an additional shelf. The shelves 42, 44, 46 and I88 provide surfaces adapted to support liquid holding trays, such as ice trays I82.

The shelf I84 may extend across the compartment 28 immediately below the evaporators 38 and 32 and be provided with a part having spaced guide rails I86 adapted for slidingly supporting a pan I88, the top of the pan being open and spaced slightly below the bottom of the partition 66, so that such partition 66 in eifect forms a cover for the pan and permits a restricted circulation of air between vthe'interior of the pan and the compartment 28. A water collecting bottle ||8 may be suitably supported behind the pan I88 and have an opening immediately below a drain port II2 formed in the partition 66, the bottle II8 serving to collect the drip from the inside of the compartment 2 frosting" thereof.

The air cooling evaporator 32, as'illustrated,,

comprises a vertical metallic plate having refrigerantducts or passageways 4 provided internally thereof, and having fins II6 secured thereto,v in good thermal conductivity with the refrigerant in the ducts H4. The evaporator 32 may consist of a pair of metallic plates II8 of suitable configuration and which are stamped, or otherwise formed, previous to the assembly thereof, with grooves or channels which after the assembly of theplates II8; form the ducts Ill. The plates '8 also are formed prior to assembly so as to provide the liquid distributing header 55 and the upper header 54. Every pair of the ducts 4 are cross connectedat the bottomand communicate with-the headers 55 and at the upper ends thereof open into the bottom of the upper header 54. The conduit 52 extends through header 55 and is provided with a. series of openings I28 which discharge liquid and .vaporous refrigerant upwardly in every other duct 4 so as to expedite the circulation of liquid through the ducts H4; The .plates 8 may be secured together, such as by welding, and, likewise, the fins are preferably'welded or soldered to the sides of the evaporator and in good thermal conductivity with the walls of ducts II4,

as illustrated in Fig. 8. The evaporator 32, as

I during the dewill be apparent from Figs. and 6, is spaced from the partition 66 so as to permit the circulation of air in the compartment 20 in heat exchange relationship with both sides of the evaporator 32. shelf I04, is arranged below the evaporator 32 for collecting the drip therefrom and is provided with a spout I26 for discharging such drip into the receptacle H0 through the open top thereof. The evaporator 32 preferably is supported from the walls of the tank 60 by means of a plurality of brackets I28 bolted thereto. The partition 66 may be formed to provide a shield- I30 which is arranged in front of the evaporator 32, and this shield may be used for supporting a cold control or thermostatic switch I32 having manual control I34, by means of which the temperature setting of the switch may be changed, and as well as to provide a cut-off for the current supply to the motor compressor unit. The cold control consists of a switch which is operated by thermostatic element I36 clamped to one side of the air cooling evaporator 32. The switch I32 opens and closes the motor circuit so as to operate the compressor in such a way as to maintain the temperature of the evaporator 32 and the compartment 20 within certain predetermined limits.

A shallow tray I24, carried by the The openings through which the conduits 36 and 52 extend through the partition 66, preferably are sealed by gaskets.

In the operation of the evaporators and 32, and with the system charged with one of the binary refrigerants referred to, vaporization of liquid refrigerant will take place in the coils of the shelves 42, and 46 producing refrigeration at a suitable low temperature level. evolved in the coils of the evaporator 30, together with the liquid refrigerant is thence conducted by conduit 52 and distributed by means of header 55 to the ducts of evaporator 32. Upon the absorption of sufficient heat refrigerant will vapor- The gas ize in the ducts, collect in the header 54 and thence be returned by the suction line to the intake side of the compressor where all of the refrigerant vapor is compressed and subsequently condensed in the condenser. As the liquid refrigerant delivered to the evaporator 32 has a reduced amount of the higher volatile component, the temperature at which refrigerant will vaporize in the evaporator 32 is higher than that at which evaporation is effected in the evaporator 30 and, hence, evaporator 32 will operate at a higher temperature level. The fins H5 provide an extended heat exchange surface for the evaporator 32, and, due to the fact that airpasses in heat exchange relationship with both sides of the evaporator 32, the temperature of the compartment 20 may be maintained lower, but at a higher relative humidity than is now possible in evaporators now generally being used. While I have shown one particular system of obtaining different temperatures in the evaporators 30 and 32, it is of course contemplated that other systems might be used in connection with the evaporators 30 and 32 so as to maintain the operation thereof at different temperature levels.

While the invention has been described with some detail, it is to be understood that the description is for the purpose of illustration only and is not definitive of the limits of the inventive idea. The right is reserved to make such changes in the details of construction and arrangement of parts as will fall within the purview of the attached claims.

I claim:

1. The method of producing refrigeration which form to said solution.

2. The method of producing refrigeration which comprises forming a liquid solution of I (CC12F2) and (CHClzF), partially evaporating saidsolution to producerefrigeration at a first temperature, transferring the resulting liquid and vapor to form a body of refrigerant at another point having a boiling point different than that of said solution, evaporating refrigerant from said body of refrigerant to produce refrigeration at a temperaturedifferent than that produced by evaporating refrigerant from said solution, condensing the refrigerant vapor and returning the same in liquid form to said solution.

3. The method of producing refrigeration which comprises forming a liquid solution of (CClaFa) and (CClaF), evaporating liquid from said solution to produce refrigeration at one temperature, transferring liquid from said solution to form a body of refrigerant at another point having a boiling point different than that of said solution, evaporating refrigerant from said body of refrigerant to produce refrigeration at a temperature different than that produced by evaporating refrigerant from said solution, condensing the refrigerant vapor andreturning the same in liquid form to said solution.

4. The method of producing refrigeration which comprises forming a refrigerant medium by mixing together polyhalogen substituted lower aliphatic hydrocarbons in which at least one of the substituted halogen atoms is fluorine, said hydrocarbons which are placed together having different boiling points and retaining said 'different boiling'characteristics, evaporating liquid from said solution to produce refrigeration at one temperature, transferring liquid from said solution to form a body of refrigerant at another point having aboiling point different than that of said solution, evaporating refrigerant from said body of refrigerant to produce refrigeration at'a temperature different than that produced by evaporating refrigerant from said solution, condensing therefrigerant vapor and returning the same in liquid form to said solution.

EARL F. HUBACKER.

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