US3831578A

US3831578A - Range exterior surface cooling device

Info

Publication number: US3831578A
Application number: US00378290A
Authority: US
Inventors: R Draper; D Beecher; D Ayers
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1973-07-11
Filing date: 1973-07-11
Publication date: 1974-08-27
Anticipated expiration: 1991-08-27
Also published as: CA998084A

Abstract

A sealed tube containing a heat transport fluid is positioned in heat exchange relation with those exterior surfaces of a pyrolytic self-cleaning oven which are raised to relatively high temperatures during the heat cleaning cycle. The heat transport fluid boils and the vapor is directed by the tube away from the hot exterior surfaces and is placed in heat exchange relation with other parts of the range which are at relatively cooler temperatures and can therefore be used as a heat sink. At these cooler locations, condensation of the transport fluid occurs and thereby removes the latent heat of vaporization of the fluid from the hot surfaces.

Description

United States Patent [1 1 [1111 3,831,578 [451 Aug. 27, 1974 Draper et al.

[ 1 RANGE EXTERIOR SURFACE COOLING DEVICE [73] Assignee: Westinghouse Eectric Corporation,

Pittsburgh, Pa.

22 Filed: July 11, 1973 [21] Appl. No.: 378,290

[52] US. Cl. 126/19 R, 126/273 R [51] Int. Cl A211) 1/00 [58] Fieid of Search 126/19, 21, 21 A, 273,

[56] References Cited UNITED STATES PATENTS 2,779,143 l/1957 Brooks 165/105 X 12/1970 Klepzig 219/400 7/1972 Moore 165/105 Primary Examiner-Edward G. Favors Attorney, Agent, or Firm-E. C. Arenz [57] ABSTRACT A sealed tube containing a heat transport fluid is positioned in heat exchange relation with those exterior surfaces of a pyrolytic self-cleaning oven which are raised to relatively high temperatures during the heat cleaning cycle. The heat transport fluid boils and the vapor is directed by the tube away from the hot exterior surfaces and is placed in heat exchange relation with other parts of the range which are at relatively cooler temperatures and can therefore be used as a heat sink. At these cooler locations, condensation of the transport fluid occurs and thereby removes the latent heat of vaporization of the fluid from the hot surfaces. 1

10 Claims, 3 Drawing Figures PAIENTED AUG 2 71924 FIG. I

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to the art of arrangements used to lower the exterior surface temperatures of a pyrolytic self-cleaning oven range.

2. Description of the Prior Art The exterior surfaces of pyrolytic self-cleaning ovens currently available experience temperatures during the self-cleaning operation which may exceed proposed industry standards. These standards will establish maximum temperatures for all exposed exterior surfaces. The surface areas that are expected to most frequently exceed the proposed temperature standards are the front of the cooking platform, and the upper front part of the range side walls.

Experimentation and analysis show that these areas are heated by conduction through the metal path leading from the oven to the front of the oven liner across the interface between the cabinet and the liner and back along the exterior surfaces of the cabinet. Rela tively very little heat is supplied to the cabinet exterior surfaces on an outward radial path through the liner and then through the insulation and the various air spaces. Some methods currently known to solve this problem are: incorporating a system of heat breaks between the oven liner and the outside wall, and using fan forced air cooling. The first of these solutions has the disadvantage of requiring air gaps in the external metal components and also some loss of structural rigidity. The second of these methods, fan cooling, has the disadvantage of being relatively costly, since it incorporates electromechanical devices, and it is also subject to operational failure. In addition, the fan adds noise to an otherwise silent appliance.

Applicants are aware of no prior art considered pertinent to the invention. However, patents which may be ofinterest in the heat transport area are as follows: U.S. Pat. Nos. 3,379,118; 3,603,767.

SUMMARY OF THE INVENTION In accordance with the invention, a pyrolytic selfcleaning oven having exposed exterior surfaces which may be touched or exposed to adjoining cabinetry is provided with an arrangement including a sealed tube containing a heat transport fluid and means in heat exchange relation with selected areas of these exterior surfaces that are subject to reaching relatively high temperatures during the heat cleaning operation of the range, the tube means extending to remote locations where it is in heat exchange relation with structure that will not be substantially elevated in temperature during the heat cleaning operation. The volatile heat transport fluid vaporizes at the hotter areas and is condensed at the cooler structure so that heat transfer is effected between the hotter areas and the cooler structure through the medium of the heat transport fluid.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a partly broken isometric view of a pyrolytic self-cleaning electricrange incorporating cooling arrangements according to the invention;

FIG. 2 is a diagrammatic view of the activity of heat transport fluid within a reflux tube which may be in accordance with the invention; and,

FIG. 3 is a partly broken isometric view of a part of a range showing an alternate embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT A pyrolytic self-cleaning range 10 is shown in FIG. 1. The range generally includes a door 12, a range top burner platform 14, side wall 16, an oven liner l9, and back guard 18.

A reflux tube 20 is installed on the underside of the top platform 14, running generally along the front lip 22 and each side 24 of the platform. The tube is held in close contact with the inner side of the front lip 22 for a substantial portion 25 of the length of the lip by fastening means such as metal pinch clamps spot welded to the flange of the lip. The tube is contoured to bend at the front corners of the platform 14 and slope in a slightly upward direction along the inner face of both sides of the platform. A section 26 of the tube 20 is held in contact with the inner face of each side 24 near the top and at the rear of each side by metal clamps similar to those used on the front lip 22. Although metal clamps are used to maintain contact in the preferred embodiment other methods such as brazing or thermally conductive adhesives could also be used. The ends 27 of the tube located at the rear of each side are sealed. The front contact portion 25 of the tube as well as the side contact sections 26 are shaped as elongated circles in cross-section in order to increase the contact area and hence the heat transfer between the surfaces and the tube.

Prior to the ends of the tubes being sealed, the tube is evacuated and partly refilled with a liquid heat transport fluid 28 (FIG. 2). The heat transport fluid is a vol atile liquid such as a fluorinated hydrocarbon refrigerant or even water. Refrigerant 11 is used in the preferred embodiment. At ambient temperatures the heat transport fluid is in its liquid phase.

During heat cleaning operations of the range, the front lip 22 becomes relatively hot and because of the intimate contact established between the tube 20 and the inner side of the front lip 22 at the contact portion 25, a substantial amount of the heat in the front lip is transferred to the tube and to the transport fluid 28 (FIG. 2) therein. Eventually sufficient heat is transferred to the transport fluid to cause nucleate boiling of the transport fluid. When this occurs, the vaporized transport fluid 30 (FIG. 2) moves through the tube away from the source of the heat, i.e., the front lip. The vapors move through the tube to the sections 26 along each side which are in contact with the sides 24 of the top platform. The sides of the top platform in this rear area are substantially cooler than the front of the platform. As a result, heat is transferred from the vapor to the sides 24 of the platform until eventually, the vapors, having lost heat at least equivalent to their latent heat of vaporization, condense into the liquid phase and settle on the bottom of the tube. Because of the constant downward slope of the tube from the side condensing sections 26 to the front portion 25, the condensed transport fluid 28 flows to the front portion 25 of the tube, into position to begin again the boiling condensing cycle just completed.

During the heat cleaning operation of the range, both boiling in the front portion 25 of the tube as well as condensing in the side sections 26 of the tube will occur simultaneously. As a result, as shown in FIG. 2, the liquid phase 28 of the transport fluid flows along the bottom of the tube in a direction from side sections 26 to front portion 25, while the vapor phase 30 of the transport fluid flows in the opposite direction, that is from front portion 25 to side sections 26. The boiling condensing cycle is continuous within tube 20 during the heat cleaning operation and any time the front lip reaches the maximum allowable temperature.

The second embodiment of the invention, a thermosiphon, is also shown in FIG. 1. A generally rhombic loop of tubing 32 is located in the hinge space 33 between the side wall 16 and the insulation retainer 34 which holds the thermal insulation 35 against the oven liner at each side wall of the range. The front leg 36 of the loop is shaped as an elongated circle in crosssection with a flatter side of the circle in intimate contact with the inner side of the front lip 38 of the side wall. These two surfaces are held in a relatively tight heat exchange relation by fastening means such as spring clamps (not shown) bolted or spot welded to the front lip of the side wall wrapper. The top leg 40 and the bottom leg 42 of the loop are slightly sloped from a low point at their junction with the front leg to a high point at the rear. The back leg 44 thus has a higher centroid than the front leg and it also has the shape of an elongated circle in cross-section, with the flatter side of the circle held in intimate contact with the inner side of the side wall 16. This puts the flatter side of the back leg at a right angle with the flatter side of the front leg and hence requires a transition in sectional shape therebetween, which in this embodiment is accompished at the corners of the loop. The back leg of the loop is held in intimate contact with the side wall wrapper by metal clamps (not shown) attached to the side wall by welding or brazing. The loop could also be constructed from tubing of various sectional shapes, i.e., square or rectangular.

As in the first embodiment described, the loop is evacuated and partly filled with the heat transport fluid which in this embodiment is also refrigerant 11. The loop is then sealed.

The principle of operation, that is, thermal shortcircuiting, for this embodiment is the same as that previously described. However, in this embodiment boiling of the heat transport fluid occurs at the front leg 36 since the front leg is in contact with the upper part of the front lip 38 of the side wall which is the area of the side wall that reaches the highest temperature during the heat cleaning operation. The vaporized transport fluid moves from the front leg 36 through the top leg 40 and condenses in the back leg 44, since the back leg is in heat exchange relation with a relatively cooler area of the side wall 16 and one which remains at temperature below the boiling point of the transport fluid. The condensed transport fluid flows down the back leg and forward through the bottom leg 42. When the liquid reaches the front leg, the cycle is complete, but it will repeat continuously throughout the heat cleaning operation of the range.

The reflux tube 20 and the thermosiphon loop 32 can be used in a heat cleaning range separately or in combination, since each embodiment transfers heat to an essentially different heat sink. The sink for the loop 32 is in the rear part of the wrapper side wall 16. The sink for the tube 20 is the rear part of the top platform 14. The joint 45' between the platform and the side wall wrapper provides sufficient thermal discontinuity and heat dissipation to allow the embodiments to work in combination.

Alternate embodiments which enhance the dissipation of heat at the heat sink areas are shown in FIG. 3. Air vents 46 are cut in the top surface of the sides 24 of the top platform 14. These air vents serve to promote the natural movement of air in an upwardly direction through the hinge space 33 (FIG. 1) between the insulation retainer 34 and the side wall 16. This movement of air serves to remove heat from the sink areas at the rear of the upper platform 14 and the rear of the side wall wrapper 16. The air vents can also be used in combination with both the tube 20 and the loop 32 or with each separately.

In addition, the capacity of the heat sink of the reflux tube 20 can be significantly increased by extending the tube out of the rear of the range 10 into the space behind the back guard panel 18 and connecting the tube to a finned air cooled heat exchanger48 as shown in FIG. 3. The heat exchanger is cooled by the natural upward movement of air along the back of the range during heat cleaning operations. In this variation condensation of the vaporized heat transport fluid 30 (F IG. 2) occurs in the heat exchanger. Some control of the degree of surface cooling can be achieved by varying the size of the heat exchanger.

We claim:

1. A pyrolytic self-cleaning oven including:

an exterior cabinet having surfaces at the forward part of said oven subject to being touched or located closely adjacent to wood cabinetry with which the oven is installed;

a forwardly open, thermally insulated oven liner in said cabinet;

sealed tube means in heat exchange relation with selected ones of said forward surfaces subject to reaching relatively high temperatures during heat cleaning operation, said tube means extending to remote rearward locations of said oven where said tube means is in heat exchange relation with structure not subject to being substantially elevated in temperature by said heat cleaning operations;

a volatile heat transport fluid within said tube means that vaporizes in said tube means at said selected surfaces and is condensed at said remote location so that heat transfer is effected between said selected forward surfaces and said remote rearward locations through the medium of said heat transport fluid.

2. In a self-cleaning oven of claim 1 wherein:

said sealed tube means comprises a reflux tube slightly sloped from a low point at said selected forward surfaces to a higher point at said rearward locations to promote the gravity return of said transport fluid in its liquid phase along the lower part of said tube.

3. In a self-cleaning oven of claim 1 wherein:

said sealed tube means comprises a continuous loop disposed in a substantially vertical plane so that as said transport fluid is condensed at said remote rearward locations, said condensed fluid flows downwardly away from said remote location through a return limb of said loop.

4. A pyrolytic self-cleaning oven including:

exterior cabinet structure and a front door therefor, said cabinet structure including at least opposite side walls and structure closely adjacent the top edge of said door;

a forwardly-open oven liner in said cabinet, said liner having thermal insulation on its exterior, said thermal insulation being spaced from at least said opposite side walls of said cabinet structure to define air passage spaces therebetween;

sealed tube means located in each of said air passage spaces and containing a volatile heat transport fluid, said tube means having a forward portion in heat exchange relation with a forward portion of said side walls, and a rearward portion in heat exchange relation with cabinet structure rearwardly from said side wall forward portion for effecting heat transfer therebetween.

5. The self-cleaning oven of claim 4 wherein:

said rearward cabinet structure comprises a rearward portion of said side walls.

6. The self-cleaning oven of claim 4 wherein:

said air passages include an outlet opening at their upper ends.

7. The self-cleaning oven of claim 4 including:

sealed reflux tube means containing a volatile heat transport fluid having one portion in heat exchange relation with said structure closely adjacent the top edge of said door, and another portion extending to and in heat exchange with said cabinet structure located rearward from said structure closely adjacent the top edge of said door.

8. The self-cleaning oven of claim 7 wherein:

said cabinet structure includes a platform; and

said another portions of said reflux tube are in heat exchange relation with the rearward portion of the sides of said platform.

9. The self-cleaning oven of claim 4 including:

sealed reflux tube means containing a volatile heat transport fluid having one portion in heat exchange relation with said structure closely adjacent the top edge of said door and another portion extending to an air cooled heat exchanger mounted exterior to said exterior structure at the rear thereof.

10. A pyrolytic self-cleaning oven comprising:

a forwardly open oven liner having thermal insulation on its exterior;

exterior cabinet structure including at least a top cooking platform spaced above said insulation to maintain an air space therebetween, said platform having a front portion closely adjacent the top forward edge of said oven liner;

sealed tube means positioned within said air space with a first length portion of said tube in heat exchange relation with said front portion of said platform and a second length portion in heat exchange relation with a rearward portion of said platform;

ity return of said condensed fluid.

Claims

1. A pyrolytic self-cleaning oven including: an exterior cabinet having surfaces at the forward part of said oven subject to being touched or located closely adjacent to wood cabinetry with which the oven is installed; a forwardly open, thermally insulated oven liner in said cabinet; sealed tube means in heat exchange relation with selected ones of said forward surfaces subject to reaching relatively high temperatures during heat cleaning operation, said tube means extending to remote rearward locations of said oven where said tube means is in heat exchange relation with structure not subject to being substantially elevated in temperature by said heat cleaning operations; a volatile heat transport fluid within said tube means that vaporizes in said tube means at said selected surfaces and is condensed at said remote location so that heat transfer is effected between said selected forward surfaces and said remote rearward locations through the medium of said heat transport fluid.

2. In a self-cleaning oven of claim 1 wherein: said sealed tube means comprises a reflux tube slightly sloped from a low point at said selected forward surfaces to a higher point at said rearward locations to promote the gravity return of said transport fluid in its liquid phase along the lower part of said tube.

3. In a self-cleaning oven of claim 1 wherein: said sealed tube means comprises a continuous loop disposed in a substantially vertical plane so that as said transport fluid is condensed at said remote rearward locations, said condensed fluid flows downwardly away from said remote location through a return limb of said loop.

4. A pyrolytic self-cleaning oven including: exterior cabinet structure and a front door therefor, said cabinet structure including at least opposite side walls and structure closely adjacent the top edge of said door; a forwardly-open oven liner in said cabinet, said liner having thermal insulation on its exterior, said thermal insulation being spaced from at least said opposite side walls of said cabinet structure to define air passage spaces therebetween; sealed tube means located in each of said air passage spaces and containing a volatile heat transport fluid, said tube means having a forward portion in heat exchange relation with a forward portion of said side walls, and a rearward portion in heat exchange relation with cabinet structure rearwardly from said side wall forward portion for effecting heat transfer therebetween.

5. The self-cleaning oven of claim 4 wherein: said rearward cabinet structure comprises a rearward portion of said side walls.

6. The self-cleaning oven of claim 4 wherein: said air passages include an outlet opening at their upper ends.

7. The self-cleaning oven of claim 4 including: sealed reflux tube means containing a volatile heat transport fluid having one portion in heat exchange relation with said structure closely adjacent the top edge of said door, and another portion extending to and in heat exchange with said cabinet structure located rearward from said structure closely adjacent the top edge of said door.

8. The self-cleaning oven of claim 7 wherein: said cabinet structure includes a platform; and said another portions of said reflux tube are in heat exchange relation with the rearward portion of the sides of said platform.

9. The self-cleaning oven of claim 4 including: sealed reflux tube means containing a volatile heat transport fluid having one portion in heat exchange relation with said structure closely adjacent the top edge of said door and another portion extending to an air cooled heat exchanger mounted exterior to said exterior structure at the rear thereof.

10. A pyrolytic self-cleaning oven comprising: a forwardly open oven liner having thermal insulation on its exterior; exterior cabinet structure including at least a top cooking platform spaced above said insulation to maintain an air space therebetween, said platform having a front portion closely adjacent the top forward edge of said oven liner; sealed tube means positioned within said air space with a first length portion of said tube in heat exchange relation with said front portion of said platform and a second length portion in heat exchange relation with a rearward portion of said platform; said tube containing a volatile heat transport fluid which vaporizes in said first length portion and condenses in said second length portion, said tube having a downward slope from said second length portion to said first length portion to promote gravity return of said condensed fluid.