US2635439A - Refrigerant evaporating element - Google Patents

Description

April 1953 A. PHILIPP REFRIGERANT EVAPORATING ELEMENT 2 SHEETSSHEET l n ZIIII- INVENTOR. QA/PI/Va'flM/HPP BY Arroklvtr Filed Aug. 9, 1950 Aprll 21, 1953 L. A. PHlLlPP REFRIGERANT EVAPORATING ELEMENT 2 SHEETS--SHEET 2 Filed Aug. 9, 1950 w w 1 RP 0 H E "u M H m. m 2 5 m flm a T u A g m n I I Y 0 m B s 5 mm a Patented Apr. 21, 1953 REFRIGERANT EVAPORATING ELEMENT Lawrence A. Philipp, Detroit, Mich., assignor to Nash-Kelvinator Corporation, Detroit, Mich., a corporation of Maryland Application August 9, 1950, Serial No. 178,505

4 Claims.

This invention relates to refrigerating apparatus and more particularly to the arrangement of the cooling system thereof and the arrangement for defrosting same.

One of the objects of the present invention is to provide for refrigerators, an improved defrosting system for the rapid defrosting of a refrigerant evaporator together with automatically operable control mechanism for returning the refrigerating apparatus to normal operation.

Another object of the invention is to provide for rapid defrosting of a refrigerant evaporator of the so-called direct expansion type by utilizing the small amount of refrigerant which during the "off phase of the refrigerating cycle drains to straight parallel bottom runs of the evaporator as a heat conveying medium for conveying heat uniformly over the surfaces of the evaporator.

Another object of the invention is to provide an improved arrangement for attaching a heater'to a refrigerant evaporator to provide increased efliciency in the defrosting of the evaporator.

A further and more specific object of my invention is to provide a refrigerating apparatus which includes a refrigerant evaporating element having bottom, side and top walls about which refrigerant flows in a single sinuous passageway wherein the bottom and side walls have straight parallel runs and the top wall has U-shaped portions which connect the straight runs of each of the side walls and through which refrigerant is circulated by a refrigerant circulating element during the "on phase of the refrigerating cycle, with the circulating element having a sufficient charge of refrigerant therein so that small droplets of refrigerant enter the refrigerant evaporating element and some pass therethrough to an accumulator at the outlet of the passageway so that when the circulating element ceases its operating phase some liquid refrigerant is present throughout the sinuous passageway, and that which is in the U-shaped portions on the top of the evaporating element and side walls thereof and accumulator will flow to the straight parallel runs in the bottom wall, and to extend a heating element transversely across and in thermal contact with said straight runs of the bottom portion so that the heating element will evaporate said liquid and thereby increase the vapor pressure in the entire sinuous passageway to cause the evaporated refrigerant to move up pairs of straight passageways to the upper part where the connecting U-shaped portion joins the pairs of straight passageways at which point the temperature of the evaporator causes the refrigerant to condense adjacent the U-shaped portions and run back down the pairs of straight passageways where it again comes in contact with the heating element to again evaporate and maintain increased vapor pressure and temperature in the evaporating element to thereby quickly and effectively defrost said refrigerant evaporating element.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings: Y

Fig. 1 is front view in elevation of a refrigerator embodying my invention having a door shown in open position and interior parts of the refrigerator broken away;

Fig. 2 is a view taken along the line 2-2 of Fig. 1;

Fig. 3 is an isometric view of a refrigerant evaporator together with a diagrammatic showing of the system and defrosting arrangement;

Fig. 4 is an enlarged fragmentary view taken along the line 44 of Fig. 2;

Fig. 5 is a view of the evaporator shown in flat together with certain associated parts; and

Fig. 6 ma fragmentary isometric view of the evaporator showing certain details of its construction.

Referring to the drawings by characters of reference, the household type of refrigerator shown comprises, in general, a cabinet 20, a refrigerant evaporator 22, a refrigerant condensing or circulating element 24, and a refrigerating apparatus control or thermostatic switch 26. In the present arrangement of the above units, the evaporator 22, condensing element and the control 26 are disposed within the cabinet with the evaporator 22 and control 26 adjacent the top of the cabinet and the condensing element 24 adjacent the bottom of the cabinet. The condensing element 24 and the evaporator 22 may be operatively connected by a capillary tube 28 and a return conduit 30.

The cabinet 20 may be of any suitable construction and may, for example, comprise. in general, a metal casing 3| and a metal liner 32. Suitable heat insulation is preferably provided between the liner and casing walls to decrease rate of heat leakage therethrough into the cabinet. The liner 32, which is boxlike in shape, forms walls of a food storage compartment 34 having ,an access opening at the front of the cabinet which is closed by a suitable door 36. As shown, the evaporator 22 is disposed within the food storage compartment 34 adjacent the top wall thereof and may be suspended from this wall by suitable hangers (not shown). Beneath the bottom wall of the food storage compartment 34, a machinery compartment 38 is provided to receive the refrigerant condensing element 24. The compartment 38 is formed by the casing sides and by a door 40 which closes the compartment at the front of the cabinet. In the present construction, the door 40 is hinged at its bottom edge to the cabinet proper and carries a storage bin 42 within the ma chinery compartment 38. A sheet metal flue member 44 is secured to theback of the cabinet at the bottom thereof to induce air flow upward through the machinery compartment 38 for the purpose of carrying away heat of condensation and other heat which tends to remain in the machinery compartment.

The condensing or circulating element 24 comprises, in general, a motor compressor unit 46 and a refrigerant condenser 48. The condenser 48 may be of the well known fin-type of condenser tube and may be mounted substantially horizontally in an opening in the bottom of the machinery compartment beneath the motor compressor 46.

The refrigerant evaporator 22 is of the socalled dry or direct-expansion type comprising, a

refrigerant flow tube 50 having U-shaped portions 5|, a heat absorber-container 52, and a refrigerant accumulator 54. As shown in Fig. 1, the evaporator 22 extends substantially across the width of the food storage compartment 34 a and as shown in Fig. 2, extends from the liner rear wall substantially to the door 34 to provide suitable storage capacity for ice cubes and for storin foods and other items to be kept in a frozen state. Preferably, the container 52v is closed at the front thereof by a hinged door 56, located adjacent the inner side of the cabinet main door 34.

To construct the evaporator 22, the evaporator tube 50 may be secured to one side of a rectangular, sheet metal blank and the metal sheet and tube bent together along the dot-and-dash bend lines 58 to form a sleeve. As shown in Fig. 5, the evaporator tube 52 is arranged sinuously on the sheet metal blank such that the tube runs extend longitudinally of the sheet with the U-shaped portions, turns or bends 5! adjacent the end edges thereof. Any suitable sheet material, such as sheet steel, may be used and the evaporator tube 50 may be welded or be otherwise suitably secured to the sheet. One end of the sleeve is closed by a sheet metal wall or panel 62 to the back of which is attached a refrigerant accumulator 54 which may be made of tubing and be welded or be otherwise secured to the panel.

It will therefore be noted that the refrigerant evaporating element 22 includes a single sinuous passageway which extends over the major portion thereof and when bent into box-like formation has straight parallel runs on the bottom and side walls thereof, which straight runs are connected together by U-shaped portions on the top wall thereof where the U-shaped portions on one half of the top wall oppose the U-shaped portions on the other half of the top wall.

The capillary tube 28 is connected to the inlet end, as at 66, of the evaporator tube, and the outlet end of the evaporator tube, as at 68, is connected to the under-side of the refrigerant accumulator 54. The return conduit 30 is preferably '4 connected to the accumulator 54 at the top thereof where gaseous refrigerant is withdrawn for return to the motor compressor unit 46.

The thermostatic switch 28 is illustrated diagrammatically as comprising a switch blade 12 and a thermostatic power element 14. A pair of lead Wires 16, 18 are provided for connecting the compressor motor to a suitable source of electrical energy, and the switch blade 12 is located in lead wire 18 to control the compressor motor circuit. The switch blade 12 may be pivoted at one end thereof and the other or free end of the switch blade may carry a contact 80 for co-oper ation with a fixed contact 82 in making and breaking the circuit of the compressor motor. The power element 14 may comprise a bellows 84 and tube 86 which may be charged with any of the suitable heat responsive, expansible-contractable fluids. The bulb end, as at 88, of tube 86 is preferably attached to the side wall of the evaporator so that the thermostatic switch will respond to changes in temperature of the warmest portion of the evaporator. The bellows 84 has a movable end wall 90, and I connect this end wall 80 and switch blade 12 together by a connecting rod or pin 92. Preferably, the connecting pin 82 is attached to the blade 12 substantially midway between the blade ends.

, In operation of the refrigerating apparatus the motor compressor, under control of the thermostatic switch 26, delivers refrigerant to the condenser 48 whence liquid refrigerant is supplied in proper amounts by the flow controlling capillary tube 28 to the evaporator tube 50 to maintain desired refrigeration. From the upper region of the accumulator 54, gaseous refrigerant is withdrawn by and returned to the compressor via the return conduit 30 for condensing by the condensing element.

In the above described so-called dry or direct expansion type evaporators, a small amount of liquid is present therein when the refrigerant condensing element ceases operation and that which is in the upper U-shaped portion and accumulator drains to the bottom of the evaporator where it collects in the straight parallel runs at this time. In accordance with my invention I utilize this liquid refrigerant in the bottom straight runs of the evaporator to provide for eflicient and rapid defrosting of the evaporator. To this end I provide a heater 94 which is arranged to heat the liquid refrigerant in the bottom runs of the evaporator and cause it to evaporate and flow up each side of the evaporator and across the evaporator top into the U- shaped portions 5|. Thus, by having the bottom and side walls arranged in parallel straight runs which are connected on their ends by U-shaped portions and extending the heater transversely across the straight runs in the central portion of the evaporator, it is found that liquid refrigerant is being heated by the heater 94 to cause it to evaporate the refrigerant and thereby increase the vapor pressure and temperature throughout the entire sinuous passageway and, due to evaporation of this refrigerant, it flows up pairs of parallel passageways to the U-shaped portions. In other words, refrigerant will flow up two parallel passageways where at the top the same are united by U-shaped portions and at the top of the evaporator, which is cold before defrosting takes place, the refrigerant in the U-shaped portion condenses and runs backwardly down the U-shaped hairpin p passa e where it again comes in contact with the bottom wall of the evaporator adjacent the heater which again causes the liquid refrigerant in this hairpin-shaped passageway to evaporate and maintain the vapor pressure and temperature in the evaporating element sufficiently high enough to quickly defrost the evaporator. In other words, there is a multiplicity of hairpin-shaped passageways, some going up one side and across a portion of the top of the evaporator and the others going up the otherside of the evaporator and across a portion of the top of the evaporator. Thus, the heating element causes evaporated refrigerant to move up both sidesand to the U-shaped portions on the top of the evaporator, thus giving a plurality of independent hairpin-like passages to distribute heat throughout surfaces of the evaporator. It has thus been found that by the numerous independent hairpin loops heat may be more rapidly distributed than would by an attempt to apply a heating element to one portion of the sinuous passageway and attempt to drive evaporated re frigerant from one end of the evaporator to the other, because in that case the liquid refrigerant which would be evaporated and flowing tothe opposite end of the evaporator where it may condense and not return back to the heating element to repeat the cycle of evaporation and condensation.

In order to provide for efficient heat transfer between the heater 94 and the evaporator 22, a heat transfer member or plate 96 is preferably attached to the bottom of the evaporator to receive both the evaporator tube straight runs extending across the bottom of the evaporator and the resistance heater or coil. The plate 96 extends substantially from front to rear of the evaporator transversely across the bottom straight runs of the evaporator, and is provided with a number of channels 98 for respectively receiving the evaporator tube straight runs so as to obtain large surface contact between the heat exchanging parts. In the plate 96 there is a plurality of recesses 91 to receive the resistance heater 94 and effect a large surface contact between the parts. The heater 94 is preferably U- shaped and extends immediately beneath and across all of the evaporator bottom runs in efiicient heat transfer relationship therewith.

A push-button control, designated generally by the numeral I00, is provided to control the heater 94 and is also arranged to be actuated by the thermostatic switch 26 to cut out the heater 94 when defrosting of the evaporator has been completed. The push-button control I00 is diagrammatically represented as a switch having a contact I02 movable between pairs of fixed contacts I04, I06 and I08, IIO. Contacts I04, I06 and I08 are in the main lead wire I6 of the compressor motor and contact I I0 is connected by a lead wire II2 to one terminal of the heater 94, which has its other terminal connected by a lead wire I I4 to main lead wire I8. Thus, when switch I00 is pushed, the circuit of the compressor motor at contacts I04, I06 is broken, and contacts I08, I I0 are bridged to complete the following circuit of the heater: From main lead wire I6 through contacts I08, I02, IIO, lead wire H2, resistance heater 94 and lead wire H4, to the main lead wire I8. The heater 94 then heats the small amount of liquid refrigerant in the bottom runs of the evaporator to effect rapid defrosting of the evaporator, as previously described, by utilizing the small amount of liquid refrigerant in the evaporator as a heat transfer medium to distribute the heat over the entire area of the evaporator.

Carried by the thermostatic switch blade 12 is a push rod' II6 arranged'to engage and move push-button switch contact I02 away from contacts I08, I I0, when the temperature of the evaporator increases to a determined temperature at which defrosting of the evaporator should be complete. The blade I2 is. preferably made sufficiently flexible to permit push rod II6 to engage and move switch contact I02 after engagement of contact with contact 82. It will be understood that switch I00 may be of any of the wellknown suitable snap-acting switche whereby the thermostatic switch need only initiate movement of the push-button switch to effect actuation thereof. When the thermostatic switch actuates the push-button switch, the circuit of the heater 94 is broken and the circuit of the compressor motor is re-established for normal cyclingop'eration ofthe system.

Fromthe foregoing description it will now be understood that I have provided an improved system for defrosting evaporators of household type refrigerators. It will be understood that by locating a heating element on'the bottom of a direct expansion evaporator, I utilize, as a heat transference medium, the small amount of refrigerant which collects at the bottom of the evaporator to distribute heat uniformly over the entire surface of the evaporator whereby to effect rapid defrosting action. It will also be understood that I have arranged the heating element to extend transversely of the evaporator tube runs substantially midway of the ends thereof, whereby the refrigerant in the bottom of the evaporator is caused to move away from the heater in opposite directions therefrom or so that the refrigerant is divided to carry heat to both sides and part of the evaporator 'top to increase further rapidity of defrosting of the evaporator. Furthermore, the latent heat of evaporation moves to the upper part of the evaporator where the refrigerant condenses and returns back to the heating element through each of the hairpin-like passageways extending up the sides and across portions of the top of the evaporator. When this condenses in these hairpin-shaped passageways, the liquid refrigerant returns to the heater where it is again evaporated and the latent heat of evaporation moves throughout surfaces of the evaporator, as previously stated herein, thus maintaining the vapor pressure and temperature of the evaporator sufficiently high enough to quickly defrost the evaporator so that frozen foods and the like stored therein do not have an opportunity to warm up to the melting point before the defrosting cycle is completed and the evaporator is back in operation to maintain such foods in frozen condition. In addition it will be understood that I have provided improved control of the heater by utilizing the thermostatic switch which controls operation of the refrigerating system to function also in automatically cutting out the heater when defrostin of the evaporator is completed.

Although only a preferred form of the invention has been illustrated, and that form described in detail, it will be apparent to those skilled in the art that various modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. Refrigerating apparatus comprising in combination a refrigerant evaporating element having bottom, side and top walls about which re- 7 frigerant flows in a sinuous passageway, the bottom and side walls having straight parallel runs and the top wall having U-shaped portions connecting the straight runs on each of the side walls, a refrigerant circulating element adapted to circulate refrigerant through said evaporating element during the on-phase of the refrigerating cycle, said circulating element having sufllcient liquid refrigerant so as to cause a small amount of liquid to remain in said evaporating element at the end of the operating phase of said cycle, and a heating element extending transversely across and in thermal contact with said straight runsof said bottom portion only and being arranged to heat said liquid refrigerant to evaporate same to increase the vapor pressure and temperature in the evaporating element and cause said evaporated refrigerant to rise to the top wall of the evaporator in said U -shaped portions where the temperature of the evaporator causes said refrigerant to condense and return back to said straight portions to be re-heated by said heating element to evaporate and maintain increased vapor pressure and temperature in said evaporating element to thereby quickly and effectively defrost said refrigerant evaporating element.

2. Refrigerating apparatus comprising in combination a refrigerant evaporating element having bottom, side and top Walls about which refrigerant flows in a sinuous passageway, the bottom and side walls having straight parallel runs and the top wall having U-shaped portions connecting the straight runs of the side walls with the U-shaped portions connecting the straight runs of one side wall terminating in spaced relation to the U-shaped portions connecting the straight runs of the opposite side wall, and a heating element extending transversely across and in heat exchange relation with only said straight runs of said bottom wall.

3. Refrigerating apparatus comprising in combination a volatile refrigerant evaporator including a sinuously wound coil providing a plurality of parallel spaced apart straight runs positioned upon substantially the same horizontal plane and a plurality of pairs of U-shaped bends with the bends of each pair being above said straight runs in horizontal alignment and each pair being spaced from the other with the connecting members of each U-shaped bend in one pair opposing the connecting members of the other pair, and a heating device arranged in thermal contact with said straight runs only along the bottom portion thereof.

4-. Refrigerating apparatus comprising in combination a volatile refrigerant evaporator including a sinuously wound coil providing a plurality of parallel spaced apart straight runs positioned upon substantially the same horizontal plane and a, plurality of connecting U-shaped bends extending above said straight runs, and a heating element extending transversely across said straight runs only along the bottom portion thereof.

LAWRENCE A. PHILIPP.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,913,433 Doble June 13, 1933 2,313,390 Newton Mar. 9, 1943 2,386,613 Johnson Oct. 9, 1945 2,410,194 Baker Oct. 29, 1946 2,413,236 Johnson Dec. 24, 1946 2,428,667 Henriquez Oct. 7, 1947 2,500,298 Smith Mar. 14, 1950 2,511,419 Smith June 13, 1950

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