US2505379A

US2505379A - Multiple temperature refrigerator

Info

Publication number: US2505379A
Application number: US614919A
Authority: US
Inventors: Ralph L Benson
Original assignee: Avco Manufacturing Corp
Current assignee: Avco Manufacturing Corp
Priority date: 1945-09-07
Filing date: 1945-09-07
Publication date: 1950-04-25
Anticipated expiration: 1967-04-25

Description

April 25, 195() R. L. BENSON IIULTIPLE TEMPERATURE REFRIGERATOR Filo@ Sept. 7, 1945 Patented Apr. 25, 1950 MULTIPLE TEMPERATURE REFRIGERATOR Ralph L. Benson, Birmingham, Mich., assignor to Aveo Manufacturing Corporation, a corporation of Delaware Application September 7, 1945, Serial No. 614,919

s claims (ci. ca -11s) The invention relates to refrigerating systems.v

One obiect of the invention is to provide a refrigerating system which includes an evaporator in a cooling compartment and an evaporator in a freezing compartment and in which one of the evaporators consists of continuous tubing of substantially uniform and relatively small diameter for progressively producingr the desired pressure drop to provide the diilerential temperatures required for maintaining cooling temperature in one compartment and freezing temperature in the other compartment.

Another object of the invention is to provide a refrigerating system which includes an evaporator coil in the cooling compartment associated with freezing trays and formed of a length of relatively small and uniform diameter tubing for producing progressive drops in pressure of the refrigerant and causing ice to be produced successively in the trays so that the water in one of the trays will befrozen faster than in the other trays.

Another object of the invention is to provide a refrigerating vsystem which includes cooling and freezing compartments and evaporator coils which are simple in construction and can be economically fabricated.

Other objects of the invention will appear from the detailed description.

The invention consists in the several features hereinafter set forth and more particularly deilned by claims at the conclusion hereof.

In the drawings:

Fig. 1 is a view of a refrigerating system embodying the invention.

Fig. 2 is a perspective of the evaporator coil in the cooling compartment.

The invention is exemplified with a refrigerator cabinet I, which includes a cooling compartment 2, and a separate freezing compartment 3. The cabinet is provided with walls for insulating the cabinet and insulating the compartments from each other. The cabinet is usually provided with a. door or doors `for access to the compartments.

The refrigerating apparatus comprises a unit 4 which includes an enclosed electric motor and a compressor for the refrigerant driven by said motor, which may be of any suitable construction, as well understood in the art, for compressing and liquifying refrigerant. 'I'he pressure or discharge side of the compressor is connected by a pipe 5 to a condenser 6.

An evaporator, generally designated 20, is 1ocated within the cooling compartment 2. Evaporator 20 comprises a box-like member 2| and 2 f an evaporator coil 22. Coil 22 is connected by a capillary tube 9 to the discharge side of the condenser for delivering restricted and controlledow of refrigerant from the high pressure side of condenser 6 to coil 22. Member 2| comprises parallel side-walls 24. a back-wall usually located forwardly of the back of compartment 2. a top-wall 25, a bottom-wall 26, shelves 21 and 28 substantially parallel with bottom-wall 26, andl a door 23 for closing the front of member 2| and providing access to the spaces in said member. Trays 29, 30 and 3| for freezing cubes are supported on bottom-wall 26 which serves as a shelf, and shelves 21 and 28, respectively.

The evaporator coil 22 consists of continuous tubing of relatively small bore and comprises a looped member or section 34 secured in heat exchange relationship to the underside of bottomwall 26 which functions as a shelf for one of the freezing trays, a looped member or section secured in heat exchange relationship with the underside of shelf 21, a leg 31 connecting members 34 and 35, a looped member or section 36 secured in heat exchange relationship with the underside of shelf 28, and a connecting leg 38 between members 35 and 36. Coil 22 is connected by means of a tube I3 of equal or greater size bore than the bore of coil 22 to an evaporator I0 for the freezing compartment 3. The refrigerant from capillary tube 9 circulates rst through the lower member 34, then through the intermediate member 35, and then through the upper member 36 so that the progressively greater drop in pressure in member 36 will cause ice to be frozen first in the upper tray 3|, then in the intermediate tray 39, and then in the lowermost tray 29. Sections 34, 35, 36 of coil 22 all operate at temperatures suiliciently low to freeze the water in trays 29, 30, 3|. This low temperature imparted to the bottom-wall 26 and shelves 21 and 28 conducts heat, which coupled with the heat removed from side-.walls 24 of member 2| by convection currents over shelves 21 and 28 in member 2| will maintain the side-walls 24 of member 2| at a sufficiently low temperature to maintain the temperature in the cooling compartment 2 Within the desired temperature range.

An evaporator I0 is provided for the freezing compartment 3 for maintaining freezing temperature in said compartment. A tube I3 conducts refrigerant from the discharge side of the evaporator section 36 of coil 22 to the evaporator I0. The discharge side of the evaporator I0 is' connected to an accumulator I4 which is connected bya suction-tube I5 connected to the suction-side of the compressor in the unit 4,V and includes a portion I6' in heat-exchange relation with capillary tube 9.'

The evaporator I for the freezing compartment 3 comprises a sheet metal wall or liner 40 extending around the bottom, top, sides and back of freezing compartment 3 and a coil 4I of looped tubing which is secured in heat exchange relationship to the outer faces of liner 40. The bore of coil 22 is so proportioned relatively to evaporators 20 and I 0 and the capacity of the compressor in unit 4 that it will cause a substantial pressure drop due to the flow of the refrigerant therethrough. The heat laden refrigerant flows from evaporator III through an accumulator I4 and tube I5 to the suction side of the compressor in unit 4. The tubing of evaporator coil 4I is of suitable diameter so that there is substantially no drop of pressure in the refrigerant flowing from tubel I3 to suction tube I5, thereby producing a freezing temperature, for example, 6 to 8 Fahr. in the freezing compartment 3 at the highest possible refrigerant pressure.

It has been found that with a standard onei'lfth horse-power compressor unit 4 and a standard capillary tube 9, the tubing of coil 22 having a bore of .125 inch and a length of 19.5 feet using Freon 12 as refrigerant, resulted in a difference in the pressure across the evaporator 20 of about fifteen pounds per square inch or about 30 Fahr. It has also been found that when the bore of the tubing of coil 4I of evaporator I0 is approximately one-fourth inch in diameter and approximately 24 feet in length, there is little, if any, difference in pressure between that at the outlet of tube I3 and that at the accumulator I4. It has also been found that in lieu of the refrigerated liner type of evaporator I0, a refrigerated or cooling plate of the type generally known as a D0le" plate may be used.

The operation of the motor of the compressor may be automatically controlled for maintaining predetermined temperature ranges in the compartments, respectively, by a thermostatic switch I6 responsive to the temperatures in the cooling compartment 2 and the evaporator 20. Current is supplied for the operation of the motor by line-conductors I1 and I8 which are connected to a suitable source of electric current, switch I6 being included in one of the line-conductors to automatically start and stop the motor and cornpressor responsively to a desired or predetermined range of temperature in the cooling compartment.

The operation will be as follows: When the temperature in the cooling compartment 2 or the temperature in the ice trays 29, 30, 3|, drops to a predetermined temperature thermostatic switch I6 will close the circuit for the motor of unit 4 and the compressor will compress refrigerant and circulate it from the high pressure side of the compressor, successively through the condenser 6, capillary tube 9, sections 34, 35 and 36 of evaporator coil 22, tube I3, evaporator coil 4I and suction-tube I5 to the low pressure side of the compressor. Capillary tube 9 restricts the flow of the refrigerant to the evaporator coil 22, thereby reducing the liquid pressure from that in the condenser 6 to the pressure desired at the inlet to the evaporator coil 22. There lwill be progressive drop in pressure ofthe refrigerant in

sections

34, 35, 38 of evaporator coil 22, which will cause the upper section 36 to freeze the cubes in the uppermost tray 3 I, then in the intermediate tray 30, and then in the lowermost tray v29, and the refrigerant leaving coil section 88 will be at the pressure in the evaporator I0.

In practice, it has been found to be advantageous, when ice cubes are quickly desired,vto freeze the cubesin one tray as quickly as possible. The refrigerant flowing through section 36 will freeze the cubes in the upper tray 3l more quickly than those in the intermediate and lower trays, so that the freezing of some cubes will be expedited to render them more quickly available. The progressive pressure drop in sections 34, 35, 36 of evaporator coil 22 tends to reduce or avoid the accumulation of frost which dehumidifles compartment 2 because the coil section 34 which is exposed to the air in compartment 2 is only slightly below freezing temperature. The temperature of the fast-freezing `shelf 28 is subs'fantially below that of the exposed bottom-wall 26 and is isolated from the air in compartment 2 by said wall 26 and shelves 21, 28, the rear-wall of evaporator member 2I and the door 23. 'I'he relatively small size of the tubing forming the evaporator coil 22 and the progressive pressure drop therein prevent trapping of liquid in the upper section 36 during 01T cycles. The pressure drop of the refrigerant circulating through coil 22 will reduce the refrigerant pressure flowing into tube I3 and evaporator ID to produce the desired temperature range, for example, 6 to 8 Fahr., in the freezing compartment 3 for the preservation of the products therein in a frozen condiion. When the temperature in the cooling compartment reaches the temperature desired, thermostatic switch I5 will open and cause the motor and compressor to be stopped and the circulation of the refrigerant to be discontinued.

The invention exemplifies a refrigerating system withan evaporator coil formed of sections for producing a progressive pressure drop of the refrigerant circulating therethrough to expedite the freezing of the cubes in one of the freezing trays in advance of the others. The invention also provides a refrigerating system which comprises a cooling compartment and a freezing compartment and evaporators therein formed of continuous tubing for producing the desired differential temperatures in the cooling compartment and the' freezing compartment without valves or moving parts.

The invention is not tobe understood as limited to the details described, since these may be modified within the scope of the appended claims without departing fr'om the spirit and scope of the invention.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is:

l. Refrigerating apparatus comprising a cooling compartment, an evaporator disposed in said compartment, said evaporator including a series of tube coils providing a plurality of spaced sections connected in series, freezing trays associated with said sections, refrigerant liquefying means connected to the inlet of said evaporator, and a return line connecting said refrigerant liquefying means to the outlet of said evaporator, the ratio of the internal diameter of said tube to the length thereof being of the order of .125 to 234 for progressively producing freezing in said trays associated with said sections.

2. Refrigerating apparatus comprising a cooling compartment, an evaporator in said compartment, said evaporator including a series of tube coils providing vertically-spaced horizontally-disposed sections connected in series, freezing trays asoasvo of said evaporator, the ratio of the internal di` ameter of said evaporator tube to the length `thereoi.' being of the order o'f .125 to 234 for progressively producing freezing'in said trays.

3. In a refrigerator having a plurality of compartments to be cooled to different temperatures, a refrigeration system comprising an evaporator disposed within the highr temperature compartment, said evaporator comprising Va. plurality of looped sections connected in series and adapted to receive ice trays, a compressor, a condenser, a delivery conduit provided with a highly restricted passageway throughout its length connecting said condenser and the inletof said evaporator, said evaporator tubing having a restricted passageway therethrough of uniform diameter throughout its length of greater diameter than that of said delivery conduit and providing a progressive pressure drop and different rate of freezing in the trays in each of said sections, a second evaporator connected to the outlet of said first-mentioned evaporator comprising a continuous tubing extending substantially entirely around four walls of the lower temperature compartment, said second evaporator having a passageway therethrough having an internal diameter at least twice that of the internal diameter of said firstmentioned evaporator tubing and providing a minimumV pressure drop throughout said secondmentioned evaporator, and tubing connecting the outlet of said evaporator to the inlet of saidcomi presser. A

4. In a refrigerator having a plurality of comproviding vertically-spaced horizontally disposed sections connected in seriesfreezing trays associated with said sections, a compressor, a condenser, a delivery conduit provided with a highly restricted passageway through its length connecting said condenser and the inlet oi said evaporator, said evaporator tubing having a restricted passageway of uniform diameter throughout its length and of a greater diameter than that of said delivery conduit, said evaporator tubing also having the ratio of itslength to its diameter such that a progressive pressure drop is produced through said evaporator sections and a diierent rate of freezing is produced in the trays associated with each of said sections, and tubing connecting the outlet of said evaporator to the inlet of said compressor.

6. In a refrigerator having a compartment to be cooled, a refrigerator system comprising. an evaporator disposed within the compartment, said .evaporator comprising a series of tube coils proin saidtrays associated with each of said sections,

partments to be cooled to different temperatures, a refrigerator system comprising an evaporator disposed within thel -higher temperature compartment, said evaporator comprising continuous tubing including a plurality of looped sections connected in series and adapted to receive ice trays, a compressor, a condenser, a delivery conduit` having a highlyy restricted passageway throughout its length connecting said condenser and said evaporator, the ratio of the internal diameter of each said evaporator tubing to the `vlength thereof being of the order of .125 to 234 for providing a different-freezing rate in the trays in each of said evaporator sections, an evaporator Aconnected to the outlet of said rstmentioned evaporator, .said second-mentioned -evaporator Vcomprising a continuous conduit extending substantially. entirely around four walls of said lower temperature compartment, the ratio of the internal diameter of said conduit to itslength being oi the order of- .25 to 288 for providing a minimum pressure drop throughout said evaporator, and tubing connecting the outlet of ,said second evaporator to the inlet of said compressor.

5. In a refrigerator having a compartment to be cooled, a refrigerator system comprising an evaporator disposed within said compartment. nid evaporator comprisingl a series of tube coils viding vertically-spaced horizontally disposed sections connected in series, a freezingtray associ-` ated with each of said sections, a compressor, a

' condenser, a delivery conduit provided with a highly restricted passageway through .its length connecting said condenser and the inlet of said evaporator, said evaporator tubing having a'restricted passageway of uniform diameter throughout its length and of a greater diameter than that of said delivery conduit, the tubing of said 'evap rator creating a sufiicient' restriction to the flow of refrigerant to produce a substantial and progresslve drop in the pressure of the refrigerant between the inlet and the outlet of said evaporator whereby a different rate of freezing is producedA and tubing connecting rator tothe inlet of said compressor.

RALPH L. BENSON. REFERENCES f The following references are of record. in

ille of this patent: UNITED sTA'rEsPATEN'rs OTHER REFERENcEs Article named rressure Drops 1n Lines," by Guy R. King onypages 41-44 of the February issue 1949, of Refrigeration,publlshed. `l Company,- 433 Principles of.Refrigeration,*\ by W, published by Nickerson Collins Co.. mens l by Nickerson and Collins Ave., Chicago, Ill. Y

annee. Third edition.

the outlet of saidevapo-