US3568465A

US3568465A - Single evaporator for combination refrigeration apparatus

Info

Publication number: US3568465A
Application number: US830755A
Authority: US
Inventors: Robert C Jung
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1969-06-05
Filing date: 1969-06-05
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09
Also published as: AU1544070A

Abstract

IN EVAPORATOR IS DISCLOSED FOR USE IN A REFRIGERATOR OF THE TYPE HAVING BOTH A FROZEN FOOD COMPARTMENT AND A FRESH FOOD COMPARTMENT IN AIR FLOW COMMUNICATION WITH AN EVAPORATOR CHAMBER ENCLOSING A SINGLE EVAPORATOR. THE REFRIGERANT TUBING OF THE EVAPORATOR IS FLATTENED AND SPIRALLY WOUND ABOUT, AND IN CONTACT WITH, A METAL CYLINDER THROUGH WHICH THE MOISTURE LADEN RETURN AIR FROM THE FRESH FOOD COMPARTMENT IS INITIALLY DIRECTED FOR ENTRY INTO THE EVAPORATOR CHAMBER. THE MOISTURE IN THE RETURN AIR IS DEPOSIED AS FROST ON THE INTERNAL WALLS OF THE CYLINDER, REFRIGERATED BY CONDUCTANCE THROUGH THE TUBING SO THAT SUBSTANTIALLY DRY, COOL AIR EXITS FROM THE CYLINDER TO MIX WITH THE RELATIVELY DRY RETURN AIR OF THE FROZEN FOOD COMPARTMENT DIRECTED TO THE EVAPORATOR CHAMBER. THE MIXED AIR IS DRAWN OVER THE EXTERIOR WALLS OF THE CYLINDER AND IN CONTACT WITH THE FLATTENED WALLS OF THE CLOSELY SPACED COILS OF THE REFRIGERANT TUBE, FURTHER COOLING THE AIR FOR RETURN TO THE RESPECTIVE COMPARTMENTS. A DEFROSTER IS ALSO PROVIDED IN THE CYLINDER FOR PERIODIC DEFROST OF THE FROST ACCUMULATION.
D R A W I N G

Description

R. C. JUNG March 'I 9A; 1971 SINGLE EVAPORATOR FOR COMBINATION REFRIGERATION APPARATUS Filed June 5. 1969 2 Sheets-Sheet l FIG.|

INVENTOR Rober? C. Jung WITNESSES n ATTORNEY R. c. JUNG March 9, `1971 SINGLE EVAPORATOR FOR COMBINATION REFRIGERATION APPARATUS 2 Sheets-Sheet Filed June`5. .1969

FEC-5.3

FIG.4

Unte States Patent I 3,568,465 SINGLE EVAPORATOR FOR COMBINATION REFRIGERATION APPARATUS Robert C. .I ung, Columbus, Ohio, assignor to Westinghouse Electric Corporation, Pittsburgh, Pa. Filed June 5, 1969, Ser. No. 830,755 Int. Cl. F25d 17/06 ILS. Cl. 62-419 10 Claims ABSTRACT F THE DISCLOSURE In evaporator is disclosed for use in a refrigerator of the type having both a frozen food compartment and a fresh food compartment in air flow communication with an evaporator chamber enclosing a single evaporator. The refrigerant tubing of the evaporator is flattened and spirally wound about, and in contact with, a metal cylinder through which the moisture laden return air from the fresh food compartment is initially directed for entry into the evaporator chamber. The moisture in the return air is deposited as frost on the internal walls of the cylinder, refrigerated by conductance through the tubing so that substantially dry, cool air exits from the cylinder to mix with the relatively dry return air of the frozen food compartment directed to the evaporator chamber. The mixed air is drawn over the exterior walls of the cylinder and in contact with the flattened walls of the closely spaced coils of the refrigerant tube, further cooling the air for return to the respective compartments. A defroster is also provided in the cylinder for periodic defrost of the frost accumulation.

BACKGROUND OF THE INVENTION The present invention relates to a single evaporator in a refrigeration unit having separate compartments which are maintained at different temperatures. An example of such a refrigeration unit is a refrigerator having a freezer food compartment maintained at a temperature below freezing, and a fresh food compartment maintained at a temperature slightly above freezing. Although it has been found economically advantageous to provide a single evaporator in such a unit, this has given rise to other problems; one of which is the rapid frost buildup on the evaporator due to the moisture laden air returning to the evaporator chamber from the fresh food compartment. Such frost buildup requires frequent defrosting for efcient operation of the evaporator. However, frequent defrosting is costly to operate and reduces the refrigeration capacity of the unit since the temperature of the evaporator and associated parts must be raised suiliciently to defrost and then lowered again to refrigerate. The heat added during each defrost must be removed during the refrigeration cycle and requires lengthy operation of the initial refrigeration cycle after each defrost. Further, the heat added during defrost produces some surface thawing of refrigerated articles in the freezer compartment contributing to the shortening of food storage capabilities of the refrigerator.

The frost is deposited on the evaporator generally in the vicinity of initial contact with the moisture laden returned air on the air inlet side of the evaporator thereby decreasing the volume of air that can effectively ow through the evaporator, which in turn decreases the efficiency of the evaporator. In the Well known n-on-tube evaporators commonly employed in the refrigeration system of the present type, previous attempts have been made to decrease the necessary frequency of defrosting of the evaporator. Exemplary among such attempts are modications of the evaporator by extending the leading edge of the ns beyond the refrigerant tubing so that more 3,568,465 Patented Mar. 9, 1971 even distribution of ice buildup is possible before the frost restricts the air flow to an inefficient amount, such as is shown in U.S, Pat. No. 3,324,678, and also increasing the distance between the fins of the evaporator to permit greater accumulation before air flow becomes blocked such as is shown in U.S. Pat. No. 3,212,285. However, in these evaporators it is still apparent that frost will continue to buildup at the inlet side of the evaporator to such a degree that the evaporator will eventually become blocked to sufficient passage of air therethrough. For further ecient operation it is further apparent that in such illustrative evaporators the frost would still restrict the return air entrance of the evaporator although the remainder of the evaporator would provide sufficient cooling if accessible to the air flow.

SUMMARY OF THE INVENTION The present invention relates to an evaporator for use in a refrigeration unit such as disclosed in the aboveidentified U.S. patents. The present evaporator comprises a flattened refrigerant tubing spirally wound about a central cylinder. The moisture laden return air from the fresh food compartment of a refrigeration unit is directed into the cylinder through a return air conduit where it is cooled and its moisture is deposited in the form of frost on the walls of the cylinder. The cylinder has a suflciently large cross-sectional area so that the frost accumulation does not prevent efficient volumetric flow therethrough. The return air thus stripped of its moisture, exits at the opposite end of the cylinder where it is forced to mingle with the relatively dry return air from the freezer compartment. The mixed air is then drawn over the exterior Walls of the cylinder and in contact with the flattened refrigerant tubing where it is further cooled prior to being returned to the respective compartments of the refrigerator. A defroster of any well known type is disposed within the cylinder so that when the frost accumulated therein acquires a suiicient thickness throughout the length of the cylinder such that the moisture is no longer stripped from the return air flowing therethrough, the cylinder can be defrosted.

DRAWING DESCRIPTION FIG. 1 is a vertical front sectional schematic view of a refrigerator employing the evaporator of the present invention;

FIG. 2 is a vertical sectional view taken generally along line II-II of FIG. 1;

FIG. 3 is an isometric vieW of the refrigerant tubing and central cylinder of the present evaporator with a piece broken away to schematically show the internal defroster, and

FIG. 4 is an enlarged sectional view taken along line IV-IV of FIG. 1, showing typical frost accumulation of the evaporator.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. l and 2 the present invention is shown as incorporated in a combination refrigerator unit 2 of well known construction having a single refrigerant evaporator I6 for maintaining freezing temperatures in a frozen food compartment 4 and temperatures in the range of 35 to 40 F. in a fresh food compartment 6. The compartments 4 and 6 are thermally insulated from each other by a horizontal insulating partition 8. The freezer compartment 6 has a bottom compartment liner 10 supported a short distance above the partition 8, and a rear wall 12 spaced inwardly from the inner insulated rear wall 14 of the refrigerator cabinet 2. A single evaporator I6 is disposed in the evaporator chamber 2i) formed between walls l2 and 14. Air from the freezer compartment 4 is returned to the evaporator chamber 20 through openings 22 in the forward portion of liner 10, communicating with the space between liner and partition 8 which terminate at the rear thereof into the evaporator chamber 20. The return air from the fresh food compartment 6 is directed through a return air conduit 24 extending from the evaporator chamber 20, through the insulating partition 8 and into the fresh food compartment 6. A vent fan 26 is disposed in the upper portion of the evaporator chamber and is actuated by an electric motor 28 connected in a common electric circuit with the motor driven refrigerant compressor so that the fan 26 runs simultaneously with the compressor as is well known in the art. The fan 26 draws the refrigerated air from the exit side of the evaporator and forces part of it through openings 30 in the rear wall 12 of the freezer compartment 4, with the remaining portion of the refrigerated air being forced rearwardly through an air duct 32 in the rear wall insulation 34 which discharges into the fresh food cornpartment 6. Thus, the evaporator chamber 20 is in air flow communication with both the freezer compartment 4 and fresh food compartment 6.

Referring now to FIGS. 3 and 4, the evaporator 16 of the present invention, comprises an evaporator tube 18, preferably of aluminum, having a generally flattened oval crosssection providing relatively wide side walls 36 and narrow end walls 40. The flattened tube 18 is spirally wound about a central cylinder 44 also preferably of aluminum, and also having a substantially oval crosssection providing relatively wide side walls 46 and narrow end walls 50. The evaporator tube 18, as wound extends along substantially the full length of the cylinder 44 with the windings of the tube 18 spaced a short distance from each other to provide access for air to the space between adjacent windings as is shown in FIG. 4. As is also shown, evaporator tube 18 is wound in such a manner that one of its narrow end walls is in contact with the exterior walls of the cylinder 44 so that the wide side walls 36 of adjacent windings of the tube 18 face each other. It is noted that no mechanical bonding between cylinder 44 and tube 18 is necessary as the cylinder 44, having preferably been shaped from a round cylinder, would have sufficient natural resiliency so that after insertion in the center of the spirally wound tube 18 it would spring-back somewhat and provide suflicient contact between the wall 40 of tube 18 and the

walls

46 and 50 of cylinder 44.

The evaporator cylinder 44 with tube 18 spirally wound thereon is horizontally disposed and generally centrally locate'd in the evaporator chamber 20. Also, as is more clearly shown in FIGS. 2 and 4, the total width of the evaporator 16 corresponds generally to the width of the evaporator chamber 20 so that there is substantially no air flow over the relatively narrow end walls of the evaporator tube 18. Air blocks 54 and 56 are placed in the evaporator compartment 20 adjacent each end thereof, above each end of the cylinder 44 and extend between the rear wall 12 of the freezer compartment and the rear wall 14 of the evaporator chamber to restrict upward air flow to the portion of the evaporator chamber 20 containing the refrigerant evaporator tube 18.

The discharge end of the fresh food return air conduit 24 is connected to the inlet end of cylinder 44 through an insulated coupling member 58 providing a thermal break therebetween. The discharge end 62 of the cylinder 44 is spaced a short distance from the end of the evaporator chamber 20 and is open for discharge of the air to the chamber 20.

A defroster of any of the well known types such as a heater wire 60, shown in FIG. 3, or a radiant heat defrost means may be disposed within the cylinder 44 and electrically connected to be actuated under a predetermined condition as is well known in the art.

The advantages of the evaporator 16 operating in the environment of a combination refrigeration unit having two separate compartments maintained at different temperatures can best be illustrated through the following description of typical air flow in the unit when the refrigerant compressor and vent fan 26 are operating in the normal manner providing the evaporator tube 18 with refrigerant and causing forced circulation of the air within the compartments 4 and 6 and chamber 20.

The moisture laden air in the fresh food compartment 6 returns to the evaporator chamber 20 through return air conduit 24 and vents into cylinder 44, the walls of which have been cooled through conductance by the surrounding evaporator tubing 18. As the return air is cooled, moisture therein is deposited on the cold inner walls of the cylinder 44 in the form of frost. FIG. 4 illustrates a typical buildup of frost 70 in the evaporator cylinder 44 and on the tubing 18 and shows the accumulation at a period of heavy frost load just prior to defrost. Under such heavy frost conditions, cylinder 44 still has a sufficient open cross-sectional area to permit an efficient volume of air therethrough; however, the flow of air in the evaporator chamber 20 through the passages between consecutive windings of the evaporator tubing 18 has become restricted by frost accumulation on the tubing 18 prohibiting efficient volumetric flow thereby. Although the greater part of the moisture carried in the return air is deposited as frost on the inner walls of cylinder 44, the frost buildup on which defrost initiation is dependent, namely the frost on the evaporator tube 18, is due to the cooler surface of the evaporator tube 18 which is able to remove further moisture from the relatively dry cool air discharging from the cylinder 44.

The return air from the fresh food compartment, after being pre-cooled and dried in the cylinder 44, discharged therefrom where it is prevented from being immediately drawn upwards by virtue of the air block 54 above the discharged end 62, and thus forced to mix with the relatively dry return air from the frozen food compartment 6 entering the evaporator chamber 20 below the evaporator 16.

The mixed return air is then drawn upwards over the evaporator 16 by the vent fan 26. The air is confined to flow through the narrow passages defined `by walls 36 of the consecutive windings of the tube 18, the outer walls 46 of the cylinder 44 and the

walls

12 and 14 of the evaporator chamber 20. The wide side walls 46 of the oval cylinder 44 provide sufficient height for the evaporator 16 so that the mixed air flowing through the passages between the windings of the evaporator tube 18 has a long vertical passage for efficient heat transfer between the air and the evaporator.

After thus being cooled, the air is returned to the respective compartments 4 and 6 of the refrigerator by vent fan 26 through vents 30 and conduit 32 as is well known in the art.

Thus, with the present evaporator, the critical area on which frost accumulates so as to require defrost operations is subjected to relatively dry cool air, substantially reducing the rate of frost buildup, prolonging the periods between necessary defrosting, and thereby reducing defrosting operations and unwanted effects therefrom. Also, the construction of the evaporator provides long narrow passageways to which the air flowing therethrough is confined, thereby exposing the air to suflicient cooling surfaces to provide the desired refrigerated air.

Further, the fabrication of such an evaporator having the attened evaporator refrigerant tube wound in a helix about a central cylinder without any mechanical bonding necessary therebetween is obviously faster, less complex, and less expensive than the well known fin-on-tube type evaporator.

What is claimed is:

1. In a refrigeration unit having a plurality of cooling compartments maintained at different temperatures with a single evaporator disposed in a chamber in the unit in air ow communication with said compartments, said evaporator comprising:

air passage means receiving moisture laden return air for initial cooling and drying;

cooling means encircling said central air passage means at spaced intervals substantially along its length for further cooling the return air from the said compartment as it passes over said cooling means.

2. The refrigeration unit of claim 1 wherein said air passage means comprises a metal cylinder connected at one end to a return air duct from one of said compartments and having the other end open to discharge air into the evaporator chamber.

3. The refrigeration unit of claim 2 wherein said cooling means comprises a flattened refrigerant evaporator tube having relatively wide side walls and relatively narrow end walls.

4f. The refrigeration unit of claim 3 wherein said evaporator tube is spirally wound with one end wall in contact with said metal cylinder.

5. The refrigeration unit of claim 4 wherein the evaporator chamber has blocking means confining the discharged air to flow across said evaporator.

6. The refrigeration unit of claim 5 having means dening a plurality of passages for the ow of discharged air across said evaporator.

7. The refrigeration unit of claim 6 wherein the means defining passages comprises said evaporator chamber, said cylinder, and adjacent side walls of said spirally wound evaporator tube.

A single evaporator Ifor a refrigeration unit having separate compartments maintained at different temperatures, said evaporator comprising:

refrigerated evaporator tubing serially connected in a closed refrigeration circuit with compressor and condenser means;

air passage means for initially receiving moisture laden return air from at least one of said zones; and wherein said evaporator tubing encircles said air passage means at relatively closely spaced intervals substantially along the length of said passage means.

9. The evaporator of claim 8 wherein the air passage means comprises a metal cylinder and said evaporator tubing is spirally wound about said cylinder.

10. The evaporator of claim 9 wherein the evaporator tubing and metal cylinder are in Contact substantially along the length of said tubing.

References Cited UNITED STATES PATENTS 2,187,470 l/ 1940 Collins 62--419 2,546,417 3/1951 Anglin 62-419 2,783,623 3/1957 Dodge 62w-426 2,856,760 10/1958 Walter 62-426 3,019,619 2/1962 Hilliker 62-419 WILLIAM I. WYE, Primary Examiner U.S. Cl. X.R. 62-407, 426, 272, 276