US2705877A

US2705877A - Heat transfer apparatus

Info

Publication number: US2705877A
Application number: US247845A
Authority: US
Inventors: Ralph E King
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1951-09-22
Filing date: 1951-09-22
Publication date: 1955-04-12
Anticipated expiration: 1972-04-12

Description

April-12, 1955 R. E. KING 2,

HEAT TRANSFER APPARATUS Filed Sept. 22, 1951 2 Sheets-Sheet 1 Raip'h E.

' His A-t'tbrngg,

April 1955 R. E. KING 2,705,877

HEAT TRANSFER APPARATUS United States Patent HEAT TRANSFER APPARATUS Ralph E. King, Erie, Pa., assignor to General Electric Company, a corporation of New York Application September 22, 1951, Serial No. 247,845

Claims. (Cl. 62117.8)

My invention relates to heat transfer apparatus and more particularly to heat transfer apparatus employed 1n refrigerating systems.

It is necessary in many devices to provide apparatus for effecting transfer or dissipation of heat. By way of example in refrigerating systems, it is necessary to (11581- pate heat from the compressed refrigerant, and this is normally effected by employing a condenser. In conventional apparatus, the condenser may be of the plate type, which includes a fiat sheet of metal with refrigerantconducing tubing brazed or welded thereto, or it may be of the finned tube type, with forced air circulation usually employed in the latter case. In connection with household refrigerators, for example, it is desirable to secure improved heat transfer and dissipation from the condenser because a smaller size condenser can then be employed, requiring less space, and it is further desirable to reduce the cost of such heat transfer apparatus.

It is an object of my invention to provide an improved heat transfer apparatus having a high rate of heat dissipation.

It is another object of my invention to provide an 1mproved heat transfer apparatus which canbe manufactured at lower cost from a reduced amount of material.

It is a further object of my invention to provide a particular positioning arrangement of the heat transfer apparatus to secure greater heat dissipation.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention, a conduit is arranged in serpentine form to provide a plurality of parallel passes, and a plurality of spaced parallel wires are secured to the passes of this conduit and extend transversely of these passes. The ratio between the diameter of the wires and the space or gap between adjacent wires is kept within a predetermined range for securing maximum heat dissipation from the apparatus. In mounting the heat transfer apparatus for use, for example, as a condenser on a household refrigerator, the apparatus is positioned at a predetermined angle with respect to the vertical, again for the purpose of securing a maximum of heat dissipation therefrom.

For a better understanding of my invention, reference may be had to the accompanying drawings, in which Fig. 1 is a side elevation view of a household refrigerator incorporating an embodiment of my invention; Fig. 2 is an enlarged view of the heat transfer apparatus taken along the line 22 in Fig. 1; Fig. 3 is a further enlarged view of a portion of the heat transfer apparatus taken along the line 3-3 in Fig. 2; Fig. 4 is a view of a portion of a modified form of heat transfer apparatus; Fig. 5 is a graph showing the variation in condenser temperature rise with changes in the ratio between the diameter of the wires and the gap therebetween; and Fig. 6 is a graph showing the variation in condenser temperature rise with the angle of positioning of the heat transfer apparatus.

Referring to Fig. 1, there is shown a household refrigerator including a cabinet 1, having a vertical rear wall 2. The refrigerator is cooled by a refrigerating apparatus including a heat transfer apparatus or condenser 3. The condenser 3 is mounted on the rear wall 2 of the refrigerator by brackets 4 and 5, which include loops 6 for engaging portions of the condenser. The brackets 4 and 5 are secured to the wall 2 by screws or other suit- "ice able fastening devices passing through slots 7 in these brackets.

As shown in Fig. 2, the heat transfer apparatus or condenser 3 includes a continuous conduit 8 which is formed to provide a plurality of parallel passes 9 arranged in the same general plane. In application of this heat transfer apparatus to a household refrigerator, for example, compressed refrigerant is circulated through the conduit 8 and the passes 9 thereof, for dissipating heat from the refrigerant. In order to facilitate the dissipation of heat from the refrigerant, a plurality of wires 10 are secured to the conduit 8. These wires extend transversely of the passes 9 of the conduit 8 parallel to the plane of the passes 9, and are secured to the wall of the conduit in any suitable manner, as by welding or brazing. The wires 10 are arranged parallel to each other in spaced relationship along the length of the passes 9 of the conduit 8. In the structure illustrated, the wires 10 are arranged on both sides of the passes 9 of the conduit, as shown more clearly in Fig. 3. In the form shown in Fig. 2, the second set of wires on the lower side of the conduit 8 are positioned directly below and in line with the wires 10 on the top surface of the conduit 8. However, some additional improvement in heat dissipation can be secured by staggering the two sets of wires, as shown in Fig. 4, so that those secured to the lower surface of the passes 9 of the conduit 8 are in line with the spaces 11 between the successive wires 10 which are secured to the upper surface of the passes 9 of the conduit 8, and vice versa.

In order to secure a maximum heat dissipation from the condenser, the ratio of the diameter of the wires to the space between successive wires is chosen in accordance with the relationship illustrated in Fig. 5. In this figure, the average rise in temperature of the condenser above ambient is plotted against factor which represents the ratio (d/g) of the wire diameter to the gap between successive wires. A diagram showing the significance of the dimensions a and g with respect to the wires and their spacing is included in Fig. 5. The graph illustrates the change in rise of temperature of the condenser with various ratios of d to g, for a ZOO-watt load and for a watt load. It can be seen that in both curves, the average rise in temperature of the condenser decreases with increase in the ratio d/g to a point where this ratio is approximately 0.4. Thereafter, further increase in the ratio d/g results in an increase rather than a decrease in temperature rise of the condenser. Therefore, to secure a maximum of heat dissipation, the ratio d/g is chosen to lie within the range from 0.3 to 0.5. Preferably, to secure the peak of effectiveness of condenser of this type, this ratio is chosen in the range between 0.35 and 0.45. As a commmercial embodiment, because of the additional factor of cost, wires having a diameter of A inch have been employed, these wires being spaced on 4 inch centers.

It has been further found that, where such heat transfer apparatus is employed, for example, mounted on the rear wall of a refrigerator, improved heat dissipation can be secured by inclining the plane of the condenser at an angle to the vertical, i. e., at an angle to the rear wall of the refrigerator, as shown in Fig. l. The condenser 3 is mounted, as shown in Fig. 1, with the passes 9 of the conduit 8 extending horizontally and with the transverse wires ltl therefore extending more or less vertically. With the usual arrangement employed for household refrigerators in kitchens, there is a limited space available between the rear wall of the refrigerator and the wall of the kitchen, and hence there is a limited amount of tilting which can be effected for securing improved heat transfer from the condenser. For example, with a condenser of the type herein disclosed, having a capacity adequate for the larger sizes of household refrigerators, a maximum inclination of about 6 degrees to the vertical is permissible within the limited space of some 3 inches available at the rear of the refrigerator.

While further improvement in heat transfer can be secured by still greater inclination relative to the vertical, reaching a maximum when the condenser is horizontal. it is a particular advantage of the type of heat transfer apparatus herein disclosed that, with the limited amount of tilt permissible, a material increase in heat transfer can still be efiected. This improvement in the heat transfer from this apparatus is graphically illustrated in Fig. 6, wherein the average rise in temperature of the condenser above ambient temperature is plotted against the position of the condenser, first in a vertical position and then inclined at 6 degrees to the vertical. Again, as in Fig. 5, the relationship is plotted both for a ZOO-watt load and for a 100-watt load. It can be seen from Fig. 6 that in both cases there is a material decrease in the rise in temperature of the condenser, resulting from the positioning of the condenser at an angle of 6 degrees with respect to the vertical. It has been further found that this improvement in heat dissipation is not possible with the use of conventional structures such as the finned tube condensers, and that the mounting of such structures at an angle of, for example, 6 degrees with the vertical, which again is approximately the maximum angle which can be secured in the space available, has practically no effect on the average rise in temperature of the condenser. Therefore, in confined regions where only a limited space is available for tilting the condenser to secure better air flow over the surfaces, the condenser disclosed herein has a material advantage over conventional heat transfer apparatus in securing maximum heat dissipation.

While I have shown and described a specific embodiment of my invention, 1 do not desire that my invention be limited to the particular construction shown and de scribed and I intend, by the appended claims, to cover all modifications within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A heat transfer apparatus comprising a continuous serpentine conduit formed to provide a plurality of parallel passes in the same general plane and a plurality of spaced nonconnecting parallel wires on each side of said serpentine conduit, said wires being secured to the passes ofsaid conduit and extending transversely of said passes parallel to said plane, the ratio of the diameter of said wires and the spacing between adjacent wires on each side of said conduit being in the range from 0.3 to

2. A heat transfer apparatus comprising a continuous serpentine conduit formed to provide a plurality of parallel passes in the same general plane, a first set of a plurality of spaced nonconnecting parallel wires secured to said passes on one side of said serpentine conduit and a second set of spaced nonconnecting wires secured to said passes on the opposite side of said serpentine conduit, the wires in each of said sets extending transversely of said passes parallel to said plane, the ratio of the diameter of said wires and the spacing between adjacent wires in each set being in the range from 0.35 to 0.45.

3. A heat transfer apparatus comprising a continuout serpentine conduit formed to provide plurality of parallel passes in the same general plane, a first set of a plurality of spaced parallel wires secured to said passes on one side of said conduit and extending transversely of said passes parallel to said plane, and a second set of a plurality of spaced parallel wires secured to said passes on the opposite side of said conduit and extending transversely of said passes parallel to said plane, the ratio between the diameter of said wires and the spacing between adjacent wires in each set being in the range between 0.3 and 0.5, said first set of wires and said second set of wires being arranged so that the wires of one set are in alignment with the spaces between the wires of the other set.

4. A heat transfer apparatus comprising an assembly including a continuous serpentine conduit formed to provide a plurality of parallel passes in the same general plane and a plurality of nonconnecting spaced parallel wires on each side of said serpentine conduit, said wires being secured to the passes of said conduit and extend 'ing transversely of said passes parallel to said plane, the

ratio of diameter of said wires to the spacing between adjacent wires on each side of said conduit being in the range from 0.3 to 0.5, and means for mounting said assembly, said assembly being so positioned that said passes of tubing extend horizontally and the plane of said assembly is disposed to an angle to the vertical of approximately 6 degrees.

5. A refrigerator comprising a cabinet including a vertical rear wall, a heat transfer apparatus comprising an assembly including a continuous serpentine conduit formed to provide a plurality of parallel passes in the same general plane and a plurality of nonconnecting spaced parallel wires on opposite sides of said serpentine conduit, said wires being secured to the passes of said conduit and extending transversely of said passes parallel to said plane, the ratio of diameter of said wires to the spacing between adjacent wires on each side of said conduit being in the range from 0.3 to 0.5, and means for mounting said assembly on said rear wall, said assembly being so positioned that said passes of tubing extend horizontally and the plane ofsaid assembly is disposed at an angle to said rear wall of approximately 6 degrees.

References Cited in the file of this patent UNITED STATES PATENTS