US1983990A - Evaporator for refrigerators - Google Patents

Description

Dec. l1, 1934. L. P 1,983,990

EVAPORATOR FOR REFRI GERATORS 1 Original Filed April 11, 1929 4 fizzy.

Lewes/van? PHIL/PP INVENTOR Pa tented Dec. 11, 1934 1,983,990 EVAPORATOR FOR REFBIGEBATOBS LawrenceA. Philipp, Detroit, Mich assignor a Kelvinator Corporation, Detroit, Micln, a corporation of Michigan Application 12 Claim.

sorbing the heat from a refrigerator cabinet and for freezing water or other substances desired to be frozen therein.

An object of the invention is to provide an apparatus in which a thermostat is actuated automatically to cause the operation of a condensing unit immediately upon the disposition of a warm freezing tray in thermal contact with a portion of a refrigerant evaporating unit.

Another object of the invention is to provide an apparatus in which substantially all of the latent 'heat of fusion, in a substance desired to be frozen, is absorbed by an evaporating unit before a cycle of operations of such unit is completed.

Another object of the invention is to provide an apparatus in which a large portion, of the latent heat of fusion of a substance, is absorbed by a heat retaining medium during the time immedi- ;ately after a substance is disposed in the evaporating unit, and before the substance is frozen sufficiently to decrease the rate of heat exchange with an evaporating unit to such a degreethat such rate of heat exchange will be insufficient to prevent the suction line of "the apparatus from frosting.

Another object of the invention is to retain the aforesaid substantial amount of heat, absorbed from the beginning of a cycle of operations, in such relation that it can be absorbed by the expansion coil at a rate of exchange high enough to prevent frosting of the suction line before the substance is entirely frozen.

Another object of the invention is to provide an apparatus in which the latent heat of fusion of a substance contained in a freezing tray can be transmitted to an evaporating device in such manner as to maintain such unit continuously in operation until substantially all of the aforesaid latent heat has been removed from the substance.

Another object of the invention is to provide an artificial refrigeration apparatus which will operate automatically and continuously in response to the heat absorbed from a warm freezing .tray disposed therein during substantially the entire time required to freeze a substance contained in such tray.

Another object of the invention is to provide an apparatus embodying an evaporating unit capable of being employed for the purpose of freezing .substances contained in trays inserted therein in April 11, 1929, Serial No. 354,319 Renewed May 4, 1934 a relatively short time without materially increasing the refrigerating effect of such evaporating unit upon a refrigerator cabinet in which it is disposed.

Another object of the invention is to provide a refrigerant evaporating unit capable of being employed normally as a device for cooling a refrigerator cabinet to a predetermined average temperature, and, when required upon special occasions, also to be capable of employment as a freezing unit of very high efllciency, without materially changing the'operational characteristics thereof in its capacity as a cooling unit.

Another object of the invention is to provide a refrigerant evaporating unit capable of continuous operation whenever a warm freezing tray is disposed therein, and in which refrigerant liquid will 'be exposed to evaporation by the freezing tray before it is eifected by any other portion of said unit. Another object of the invention is to provide a :large amount of heat exchange surface, in thermal contact with a freezing tray, in'which refrigerant liquid is discharged directly from a refrigerant liquid expanding device.

Another object of the invention is to provide a refrigerant evaporating unit having a warm freezing tray receiving region capable of evaporating refrigerant liquid, for a. predetermined period, at a rate substantially greater than the capacity of a refrigerant condensing unit associated therewith, and during which period other portions of the evaporating unit will increase in temperature by absorbing heat from a refrigerator cabinet, thus providing a quantity of heat for evaporating refrigerant liquid when the rate of evaporation by the heat from the freezing tray decreases to a value below the capacity of the refrigerant condensing unit.

Prior to the invention it has been the practice to construct refrigerant evaporating units primarily for the purpose of cooling a refrigerator cabinet to a temperature low enough to preserve food substances contained in regions adjacent the evaporating unit, which regions were cooled by a circulation of refrigerated air therein. Such evaporating units were provided with sleeves or other suitable means in which trays, containing substances desired to be frozen, were inserted. These substances could be frozen after a 'substantial period of time had elapsed merely as a collateral function of the operation of the evapcrating unit as a device for cooling the refrig-' erator cabinet to a predetermined average temperature.

- prior to such change of state.

In such refrigeration apparatus as soon as a warm freezing tray was disposed in thermal contact with a portion of an evaporating unit, the latent heat of fusion of the substances in the tray was absorbed by the evaporating unit and dissipated substantially throughout the entire mass of the latter thus reducing its average temperature to such degree that the condensing unit of the refrigeration apparatus was caused to be operated by some form of controlling device associated therewith.

Owing to the fact that the heat obtained from the freezing tray was distributed throughout a greater portion of the evaporating unit, it could not be employed for evaporating refrigerant liquid in the evaporating unit at a rate equal to the rate at which the evaporated liquid was condensed by the condensing unit. Consequently, the apparatus would operate only for a short time before the suction line would tend to become frosted by reason of the evaporation therein of refrigerant liquid which previously had not been evaporated in the evaporating unit.

In a refrigerating apparatus wherein the operation of a condensing unit was controlled by the suction pressure, the rate of refrigerant liquid evaporation likewise was not great enough, when the freezing tray wasv inserted in the evaporating unit, to maintain a rate of evaporation high enough to cause the continuous operation of the condensing unit. It has been proposed to vary the capacity of such evaporating units by changing the entire range of operation of the refrigeration apparatus. While such refrigeration apparatus is capable of freezing substances in trays at a relatively rapid rate, it is apparent that the evaporating units can not be made to meet this abnormal situation without cooling the entire refrigerating cabinet to-a degree much lower than that at which it is normally designed to operate.

This invention is embodied in a structure in which the freezing of substances contained in freezing trays is carried on independently of the function of cooling the refrigerator cabinet. Under normal conditions of operation, when the evaporating unit of such apparatus is employed merely for the purpose of cooling a cabinet in which it is installed, the periods of operation of a refrigerant condensing unit are controlled in the usual manner, that is under the influence of the temperature of the circulating air. By thus intermittently operating the apparatus, a refrigerator cabinet may be cooled to a required average temperature suitable for preservation of foods. When it is desirable to employ the apparatus for the purpose of freezing water or other substances contained in freezing trays, the latter merely are inserted in the evaporating unit, and, substantially without variation in the operation of the evaporating unit as a device for cooling the refrigerating cabinet, and, in an entirely automatic manner, the operational characteristics of the evaporating unit are so modified as to retain the condensing unit continuously in operation until substantially all of the latent heat of fusion of the substances contained ina freezing tray, is absorbed by the refrigerant liquid.

It is to be understood that the rate of heat exchange from any substance contained in a freezing tray, decreases very materially as the substance solidifies because the conductivity of a frozen substance is materially less than that Such variation being proportional to the thickness of the frozen substance, it is apparent that when a freezing tray containing a warm substance is first inserted in an evaporating unit, the rate of refrigerant liquid evaporation is far greater than it is when the substance is substantially frozen; that is, the rate of evaporation decreases as a function of the rate of heat exchange between the substance and the evaporating unit.

When a warm freezing tray is inserted in an evaporating unit, this invention provides means for absorbing some of the heat received from the freezing tray in a heat retaining medium from which it is obtainable to retain the evaporation rate of the refrigerant liquid at a substantially constant'value during the latter part of a cycle of operations. This heat absorbed by the heat retaining medium is retained in the immediate vicinity of a liquid refrigerant evaporating device incorporated in theevaporating unit, and is not dissipated throughout the entire mass of the latter wherein'it would be unavailable for the evaporation of the refrigerant liquid when the rate of heat exchange from the substance is decreased to oration rate required to maintain the condensing unit continuously in operation.

The invention also comprehends the employment of a control device which is immediately responsive to the heat embodied in the substance containedin a freezing tray introduced into the refrigerant evaporating unit. Consequently, the refrigeration apparatus will become operable for the purpose of freezing substances in a freezing tray long before the entire evaporating unit could be heated sufiiciently to cause such operation.

For a better understanding of the invention, reference may now be had to the accompanying drawing forming a part of this specification in which:

Figure 1 is a fragmentary cross-sectional view of an artificial refrigerating apparatus illustrating an evaporating unit embodying one form which the invention may assume:

Figure 2 is a longitudinal cross-sectional view through the evaporating unit illustrated by Figure 1;

Figure 3 illustrates a mechanical condensing unit which may be incorporated in an apparatus embodying the invention;

Figure 4 is a fragmentary cross-sectional view of an evaporating unit embodying another form which the invention may assume;

Figure 5 is a fragmentary cross-sectional view of another form of evaporating unit in which the invention may be embodied;

Figure 6 is a view illustrating the lower side of a removable freezing unit embodied in the structure illustrated by Figure 5;

Figure 7 is a cross-sectional view of the freezing unit illustrated by Figure 6.

A refrigerator cabinet 11 employed in practising the invention is provided with a refrigerant evaporating unit 12 secured therein by any suitable means (not shown). A brine tank 13 embodied in the evaporating unit is provided with an opening 14,through which a heat retaining medium, such as calcium chloride brine, for example, is introduced. A cap 16, for the opening 14, is adapted to prevent the escape of the brine solution by evaporation or otherwise.

A refrigerant expansion valve 17, secured by bolts (not shown) on a boss 18 projecting from the brine tank 13, is adapted to discharge sulphur a value below the evapdioxide or other suitable refrigerant liquid into a relatively long evaporating conduit 19 having a relatively small cross-sectional area. Byemploying a conduit of such dimensions it is apparent that the ratio, between the area exposed to the refrigerant liquid in such conduit, and the amountof refrigerant liquid contained therein, numerically is relatively large.

The conduit 19, adapted to be wound spirally or in any other suitable manner, is soldered, as indicated at 21, throughout substantially its entire length to the lower surface of a horizontally disposed freezing tray sleeve 22 disposed internally of the brine tank 13 in an upper portion thereof.

The end of the coil 19, opposite the expansion valve 1'7, is connected, either internally or externally of the tank 13, to-a second spirally wound section of evaporating conduit 23. The conduit 23 likewise is soldered, as indicated at 24, to the lower surface of a freezing tray receiving sleeve 26 projecting into the tank 13 immediately below and in spaced relation to the sleeve 22. The sleeves 22 and 26 are adapted respectively to receive trays 27 and 28 adapted to contain water or other substances desired to be frozen.

The discharge end of the conduit 23 is adapted to be connected to a larger refrigerant fluid evaporating conduit 29 which is disposed in any suitable manner within the tank 13 in the brine solution surrounding the sleeves 22 and 26. The opposite end of the conduit 29 emerges from the brine tank 13 immediately adjacent the end of one' of the sleeves 23 or 24 through a collar 31. It is to be observed that as soon as the tray is disposed in a sleeve adjacent the collar, the temperature of the latter will be increased almost immediately by the conduction of heat from the bottom of the tray through a relatively short heat conductive path in the portion of the brine tank therebetween.

A thermostat 32, having a fluid containing bulb 30 connected by a metallic clip 33 to the end of the conduit 29 projecting through the collar 31, is adapted to be connected by conductors 37 in series with a motor 34 of a refrigerant condensing unit 36. The end of the conduit 29 merges into a suction line 38 communicating with a refrigerant fluid compressor 39 which is driven by the motor 34 through a belt and pulley power transmission mechanism 41.

During the operation of the condensing unit 36 evaporated refrigerant fluid is withdrawn from the evaporating unit 13 through the suction line 38 by the compressor 39. This evaporated refrigerant fluid is discharged by the compressor 39 at a relatively high pressure into a condenser 42 from which, in turn, it is discharged in a liquid statethrough a receiver 43 and a conduit 44 from the refrigerant expansion device 17.

A pair of baflle plates 46 are soldered, or otherwise rigidly secured to the opposite edges of the sleeve 22 within the tank 13, in such manner as to project'downwardly a substantial distance below the bottom of the sleeve, thus providing only a limited amount of space between the lower ends of the bafiles and the sleeve 24 for the circulation of brine within the tank. The sleeve 26 is likewise provided with a pair of baffle plates 47 which are disposed in the same relation to the latter sleeve as the baflie' plates 46 are to the sleeve 22. The plates 47 likewise prevent the circulation of brine from beneath the sleeve 26 to other portions of the tank 13 except in the space beneath the lower edges of the bailies.

In the operation of the structure embodying the invention, the thermostat 32 is adjusted in such manner that undernormal conditions of operation, wherein the evaporating unit-is employed merely for the purpose of cooling the refrigerator 11, it will close the circuit through the motor 34 and cause the operation of the condensing unit 36 when the temperature of the refrigerator 11 increases beyond apredetermined maximum frigerator 11 to a.predetermined minimum temperature. Thisoperation of the condensing unit between such maximum, and minimum temperatures in the refrigerating unit is known as a single cycle of operations.

When a warm freezing tray 28 is disposed'in the sleeve 26 adjacent one end of which the evaporating conduit 29 projects through the collar 31, the heat from the tray is transmitted within a very short time through the sleeve 26, the tank 13, the collar 31, the end of the conduit 29, and the clip 33, to the bulb 30 of the thermostat 32. Hence, even though the temperature in the refrigerator 11 is relatively low, the temperature of the bulb 30 will be increased to the aforesaid predetermined maximum value, thus causing the actuation of the thermostat 32 for the purpose of closing the circuit through the motor 34 as a result of which the operation of the condensing unit 36 ensues. Thereupon condensed refrigerant fluid will be discharged by the expansion valve 17 into the evaporating conduit section 19.

If the tray 27 also contains a substance at a relatively high temperature, the refrigerant liquid in the conduit 19 will be evaporated at a relatively high rateowing to the efficient conduction of heat. from the tray 2'7 to the conduit. However, in view of the fact that the external surface of the conduit 19 is exposed to a limited quantity of the brine in the brine tank 13, the

temperature of such quantity will be increased ,materially during the evaporation of the liquid in the conduit 19. Under normal circumstances, this heated brine being of less specific gravity than the cold brine with which it is associated in the brine tank 13, would immediately rise to the top of the tank and, consequently, would not be available at a later period for the purpose of giving up its heat to the evaporation conduit 19. Thus it is apparent that the brine tank 13 and sleeves 22 and 26'form a double wall sheet metal housing which protects the ice trays from the warming influence of circulating air. By virtue of this construction together with the soldering of each coil 19 and 23 throughout its entire length to its respective sleeve 22 and 26, a cooling unit is provided in which water or other substance can be frozen quickly.

However, owing to the presence of the baffles 46 projecting below the bottom of the sleeve 22, such heated brine tends to remain in the immediate vicinity of the conduit 19. When the rate of heat exchange between the conduit 19, through the heat exchanging portion of the sleeve 22 and the freezing tray,27 is reduced by the partial freezing of the substance contained in the latter, the heat of the brine will be employed for the purpose of increasing the normal evapora tion rate in the conduit 19, and thus maintaining it substantially at a constant value.

In the event the substance in the tray 27 is already frozen when the tray 28 is inserted in the evaporating unit, no substantial amount of heat will be absorbed by the evaporating conduit 19 by reason of its being immersed in the previously cooled brine contained in the tank. Consequently, such refrigerant liquid will be conducted through the conduit 19 to the conduit 23, the temperature of which is increased to a relatively high degree by the presence of the warm freezing tray 28 therein. The refrigerant liquid will be evaporated in the latter conduit at a relatively high rate and, likewise, the brine solution beneath the sleeve 26 will be heated and confined by the baflles 47 in a manner identical to that hereinbefore described when a warm freezing tray 27 was inserted in the sleeve 22.

It is apparent, during the time immediately after one of the trays is inserted in the evaporating unit, that the evaporation of refrigerant fluid will occur at a rate substantially equal to, or even greater than, the capacity of the refrigerant condensing unit to withdraw the evaporated fiuid from such unit. In such event, the temperature of the brine in portions of the tank not associated with the conduits 19 and 23 will be gradually increased by the absorption of heat from the interior of the refrigerator 11. Thus it will be seen that it is permissible for the rate of evaporation of a fluid in the conduits 19 and 23 eventually to fall slightly below that required to maintain the condensing unit in continuous operation by reason of the fact that refrigerant liquid will be evaporated in the conduit 29 for a substantial period of time before the end of the conduit associated with the thermostat 32 cools the bulb thereof to the predetermined minimum temperature required to open the circuit through the motor 34. However, this final stage of evaporation of the refrigerant liquid must not be permitted to occur until the apparatus is operated for a considerable period of time in absorbing heat from the trays 27 and 28 at substantially the capacity of the machine.

It is to be understood that various substances required to be frozen in an evaporating unit of a refrigerating apparatus may contain different quantities of heat which are required to be extracted therefrom before such substances are frozen. Consequently, it may be desirable to construct refrigerating units of different or varying freezing capacities each especially designed for the purpose of freezing a particular substance. For the purpose of this specification the heat required to be extracted from a single tray of water is assumed to be a standard.

The refrigerant evaporating unit illustrated by Figure 4 embodies all of the essential elements of the evaporating units illustrated by Figures 1 and 2 except that a different form of freezing structure is associated with the upper tray. Otherwise, the reference numerals and description regarding Figures 1 and 2 are applicable to Figure 4. Instead of employing the sleeves 22 and 26 in the brine tank 13, a single sleeve 48 is adapted to contain both of the trays 27 and 28. A metallic plate 49 composed of cast aluminum, iron, copper, etc. is secured horizontally in an intermediate portion of the sleeve 48 upon metallic brackets 51 which may be secured rigidly to the vertical sides of the sleeve 48 by soldering or other suitable means. The conduit section 19 is adapted to be cast in the interior of such plate, and is associated with the evaporating unit in substantially the same manner as it is in Figure 1.

In Figure 5, the reference characters and description employed in regard to Figure 1 likewise are applicable to corresponding elements of this form of evaporating unit. The tray 2'7 is adapted to be associated with the brine tank 13 in the usual'manner without employing the coil 19. Thus, refrigerant liquid from the expansion valve 19 is discharged directly into the freezing coil 23 which is soldered to the lower surface of a removable plate 52 adapted to be supported within the sleeve 26. In this form of the invention the baffle plates 46 are not to be employed on the sleeve 22 by reason of the fact that it is desirable to permit the heated brine to circulate from beneath the sleeve. This freezing plate, together with a properly arranged controlling device, may be employed in any refrigerant evaporating rating unit in which it is desired to incorporate the cardinal principles of this invention.

Inasmuch as the structures embodying the invention, as disclosed by Figures 5 and 6, are operable in substantially the same manner as that disclosed by Figure 1, it is unnecessary to repeat the mode of operation as relating thereto.

It is to be understood that the expansion conduit 19, as illustrated by Figure 1, may be entirely eliminated from the evaporating unit, thus providing a structure in which the tray 28 will be frozen at a greater rate than the tray 27. In such structure as soon as the substance in the tray is completely frozen, the latter will be transferred to the sleeve 22, and another inserted in the sleeve 26.

Although a brine solution in many respects is preferable to any other form of heat retaining medium it is possible to embody the invention in a structure employing cast iron, aluminum, brass, earthenware or bituminous material for this purpose. Likewise it is not essential to employ tubular conduits for the purpose of evaporating refrigerant liquid. Other well known devices suitable for the purpose of evaporating refrigerant liquid may be substituted therefor if preferred.

While the preferred form of the invention has been illustrated with particular relation to a dry system employing an expansion valve and thermostat for controlling the operation thereof, it is obviously capable of application in any other form of refrigeration apparatus.

Although the specification discloses only the preferred forms of this invention, and describes in detail only certain applications thereof, it will be apparent ,to those skilled in the art that the invention is not so limited but that various modifications and changes may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What I claim is:

1. A refrigerant evaporating conduit having a relatively high evaporation capacity disposed in thermal contact with a heat exchanger, a brine solution associated with the heat exchanger, said brine solution being confined to prevent its circulation away from the expansion conduit after becoming heated, and means for controlling the flow of refrigerant through said conduit in response to changes in temperature of said brine.

2. A refrigerant evaporating unit comprising a metallic heat exchanger, disposed in a horizontal plane, for supporting a freezing tray containing warm substance to be frozenra relatively long evaporation conduit of small cross sectional area disposed throughout substantially its entire length in thermal contact with the heat exchanger, a liquid heat retaining medium in thermal contact with the conduit, and vertically disposed baflies'secured to and projecting a substantial distance below the edges of the heat exchanger for preventing circulation of the heat retaining medium away from the evaporating conduit after its absorption of heat.

3. A refrigerant evaporating unit comprising a planular metallic heat exchanger, a relatively long evaporating conduit having a relatively small cross-sectional area disposed in good thermal contact, throughout substantially its entire length, with one side of the heat exchanger, and a thermostat connected to the heat exchanger by a relatively short heat conductor.

4. A refrigerant evaporator comprising a brine tank having a freezing tray sleeve projecting therein, a curved conduit of relatively small cross sectional dimensions disposed in thermal contact with a lower portion of said sleeve only, another conduit of larger cross sectional dimensions than the first connected to the latter in series and comprising a conduit of relatively small cross,

sectional area having substantially its entire length arranged to form a horizontal shelf for the support of a freezing tray on the upper surface thereof, and a conduit of relatively larger cross sectional area connected in series with the latter and arranged in a region remote therefrom for cooling the interior of the insulated compartment.

6. The combination with an insulated refrigerating compartment suitable for the circulation of air internally thereof, of a relatively small conduit having substantially its entire length arranged to form a horizontal shelf for the support of a freezing tray on the upper surface thereof, and a larger conduit connected in series with the latter and arranged for cooling circulating air in the interior of the refrigerator to provide a cage substantially surrounding the first mentioned conduit.

7. The combination with an insulated refrigerating compartment suitable for circulation of air internally thereof, of a relatively small curved conduit disposed longitudinally and in heat exchanging relation to the bottom portion only of a freezing tray disposed thereon, and a relatively larger conduit forming a cage surrounding the latter and arranged for cooling circulating air in the interior of the aforesaid insulated compartment.

8. The combination with a refrigerator cabinet for the circulation of air internally thereof, of a relatively small conduit for the absorption of heat from a freezing tray disposed in thermal contact therewith, a relatively larger conduit connected in series with the latter and forming a cage arranged for cooling circulating air in the refrigerator and substantially surrounding the relatively small conduit, means for sup l ing refrigerant fluid first to the relativelysmall conduit and thereafter to the other conduit, and a thermostat directly connected to said relatively larger conduit.

9. A refrigerating apparatus comprising a metal heat exchanger, an evaporator coil of small cross sectional area secured in intimate contact with the heat exchanger, a larger evaporator coil connected to said'coil in series and spaced from the heat exchanger, a refrigerant condensing unit operatively connected to the evaporator coils whereby refrigerant is admitted to the first mentioned coil'and withdrawn from the larger coil, and means directly connected to the larger coil and responsive to the temperature of the larger coil and the 'heat exchanger for controlling the operation of the condensing unit. I I

10. A mechanical refrigerator comprising a refrigerant condensing unit, a heat insulated refrigerating compartment suitable for the circulation of air internally thereof, a metallic heat exchanger disposed within said compartment, an evaporator coil disposed within the compartment having a portion in direct contact with the underside only of said heat exchanger and a portion spaced therefrom, means for delivering refrigerant from the condensing unit to'that portion of the coil contacting the heat exchanger, means for withdrawing refrigerant from the evaporator coil remote from-the heat exchanger, and means responsive to the temperature of the circulating air in the compartment and the heat exchanger for controlling the operation of the condensing unit.

11; A cooling unit for use in a household type refrigerator comprises a double wall sheet metal housing, a volatile refrigerant within said housing, said housing being open in the front for the reception of an ice tray and providing a shield for protecting the ice tray fram the circulating air, and a refrigerant conveying conduit having substantially its entire length arranged to form a horizontally disposed heat absorber, said conduit being positioned within the confines of the housing and forming the heat absorber for the bottom of an ice tray within the housing.

12. A cooling unit for use in a household type refrigerator comprising a double wall sheet metal housing, a volatile refrigerant within said housing, said housing being open in the front for the reception of an ice tray and providing a' shield for protecting the ice tray from the circulating air, and refrigerant conveying means connecting the refrigerant therein in series circuit relation with the volatile refrigerant in said double wall housing, said refrigerant conveying means forming in its entirety a horizontally disposed heat absorber'and being positioned within the confines of the housing and forming the heat absorber for the bottom of an ice tray within the housing.

LAWRENCE A. PHILIPP.

Images