COMBINATION HEAT TRANSFER PANEL AND WALL SHIELD FOR USE WITH STOVES AND OTHER RADIANT HEATERS

Abstract: The device comprises a case housing two parallel, spaced curtains (34, 36) defining first and second convection cham­ bers (38, 40). The case is adapted for location either against, or in spaced relation to a structural wall behind a radiant heater. It is formed with a large central opening (20) permitting entr­ ance of radiant energy from the stove, a cold air inlet (64) communicating with the convection chambers either at the lower end of the case or at the sides, and a hot air exhaust (32) communicating with the upper end of the convection cham­ bers. The outermost curtain (34) may be constructed for adjustment between positions in which it absorbs or reflects radiant energy as desired.

Description: "COMBINATION HEAT TRANSFER PANEL AND WALL SHIELD FOR USE WITH STOVES AND OTHER RADIANT HEATERS" This invention relates to a combination heat transfer panel and wall shield for use with stoves and other radiant heaters. Due to the limited nature of the supply of fossil fuels, it is apparent that these fuels should be reserved for areas in which they are uniquely useful and most critical. Residential and commercial space heating is not necessarily one of those areas. Thus, we have witnessed in recent years new interest in exploring alternative systems of harnessing energy-for space heating; which energy can be derived economically from inexhaustible or replenishable sources. Such systems include nuclear reactors, geothermal and solar devices, windmills, ocean-wave-mills, etc. Included in this category of alternative energy systems is the wood or coal burning heater/stove. Although wood is not an inexhaustible source of energy, it is replenishable. The revival of the traditional Franklin iron stove has been accompanied by the development of numerous refined embodiments of the traditional stove. New features include the principles of air-tightness, thermostatic control, preheating of combustion air, etc. All such features tend to increase the efficiency of combustion so as to maximise the extraction of useful heat from a given amount of fuel. Although the recent proliferation of iron and steel heater/stoves may well help to ease the burden on petroleum supplies, their installation in conventional wood-frame structures can present problems of safety and convenience. One fundamental problem is the fact that such radiant heaters must be installed with specific minimum clearances from combustibles, if they are to be installed safely. Such clearances can exceed three feet in some cases. This means that the floor space behind such a stove can be virtually useless to the home owner, floor space for which he has paid dearly, Although radiant h-eaters are most effective when installed in the middle of a room, the vast majority of installations are not of this type and mainly for aesthetic or practical reasons, the heaters are placed as close as possible to walls or corners. One negative effect of this type of installation, from an efficiency point of view, is that a significant portion of the heat which is radiated from the rear of the stove is absorbed by the back wall and perhaps lost to the outdoors. Some manufacturers design their stoves with steel baffles attached to the rear of their units in order to minimize the amount of radiant heat produced there. Although reduced clearances can be achieved in this manner, it is clear that such a baffled unit produces less total heat than does an unbaffled stove and thus runs counter to the aim of extracting a maximum amount of heat from a given amount of fuel. Prior art directed toward distance reduction for radiant heaters has for the most part been restricted to specified procedures of field masonry. For example, brick walls are constructed with carefully maintained air spaces behind them to insure a free flow of cool air along the back side. One drawback to this method is the cost involved - in some cases additional footings are required to carry the load of the additional masonry. In many instances such footings are not feasible. Another method of distance reduction involves the use of prefabricated steel wall panels and hollow sheet metal pans filled with insulation. Whether or not this method of wall protection is truly effective from a safety point of view, these panels do suffer from the aesthetic standpoint. Other methods include the use of various factory-made precast cement panels which are installed with spacers to insure the free flow of cool air on the backside. In various ways, these panels all suffer from problems of weight, cost, inconvenience, and aesthetics. The invention consists in a combination heat transfer panel and wall shield for use with non-solar radiant heaters and consisting of a case adapted for location either directly against, or in spaced relation to, a structural wall behind a radiant heater characterised in that it comprises a base, a header, and side panels, the front of the case facing the heater having an opening to permit entrance of radiant heat within the case, a first curtain assembly mounted across the front opening'of the case, a second curtain assembly mounted a spaced distance behind and substantially parallel to the first curtain assembly, thereby defining a convection chamber between the first and second curtain assemblies, a cold air. inlet communicating with the lower end or with the sides of the convection chamber, and a hot air exhaust communicating with the upper end of the convection chamber. The invention thus has the advantages of providing a convenient, aesthetically pleasing, and functional protective covering for combustible walls, when these walls are exposed to sources of high radiant heat. In addition to its function of protecting combustible surfaces, another primary function is to provide an effective means of utilizing heat energy from a radiant heat source and redirecting or converting it in such a manner that it proves most useful for the purpose of heating space. Another important function of the device described herein is that of utilizing heat that normally is absorbed and lost by the walls located directly behind radiant heaters. Moreover the invention provides a combination heat transfer panel and wall shield for use with stoves and other radiant heaters which is simple in construction, efficient in operation, low in cpst, easily maintained, and attractive in appearance. The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a foreshortened vertical elevation of one embodiment of combination heat transfer panel and wall shield according to this invention, with parts broken away to show interior construction. Fig. 2 is a foreshortened transverse sectional view taken along line 2-2 of Fig. 1, Fig. 3 is a foreshortened longitudinal sectional view taken along line 3-3 of Fig. 1, Figs. 4 and 5 are fragmentary views similar to Fig. 3 but illustrate alternate operating pbsitions of the panel. The hereindescribed combination heat transfer panel and wall shield is adapted for use with non-solar radiant heaters such as wood and coal burning stoves and fireplaces; as well as oil, kerosene and alcohol burning heaters and electric heaters. It is designed particularly for use with wood and coal burning stoves. As shown particularly in Fig. 3, the device is adapted for placement directly against a structural wall 10, which it shields, and behind a stove or other radiant heater (not illustrated) located nearby on the side opposite the wall. The device is housed in a case comprising a base 12, a pair of upstanding side walls 14 and a header 16. These structural elements are fastened to each other by means of bolts, welding, or other suitable securing means. The back of the case preferably has a large opening 18 to conserve material. The front of the case has a large central opening 20 which faces the radiant heater and admits radiant heat to the interior of the device. In cross section, heater 16 has the general contour of the letter G, arranged face down. It may be formed integrally from a single sheet of bent sheet metal. It comprises a short back wall segment 22, a top segment 24, a front wall segment 26, and a reversely bent inner segment 28, 28a. The floor 28a of the reversely bent segment is provided with opening 30 the purpose of which will appear later. Front segment 26 is provided with a long opening 32. This serves as a hot air exhaust vent for the assembly. The case above described houses two spaced curtain assemblies arranged parallel to each other in the plane of the case. The first curtain assembly, indicated generally at 94, is toward the front and serves the primary function of controlling the admission of radiant energy into the interior of the case. The second curtain assembly, indicated generally at 36, serves the primary purpose of providing a heat shield to protect wall 10. Both curtain assemblies serve the further purpose of directing the flow of heat trapped and/or generated by the apparatus out of hot air exhaust vent 32. To this end, the two curtain assemblies are spaced from each other and from the structural wall in such a manner as to provide a first, or outer, convection chamber 38 and a second, or inner, convection chamber 40. It will be observed that in the illustrated embodiment structural wall 10 itself provides one of the defining surfaces for inner convection chamber 40. The first or outer curtain assembly 34 preferably comprises a plurality of vertically or horizontally arranged louvres which preferably are arcuate in contour and which preferably are components of the venetian blind sub-assembly illustrated in Fig. 3. The construction of the venetian blind sub-assembly is substantially conventional. It comprises a plurality of vertical, ladder-shaped straps 42 made of fibreglass threads or other flexible, non-combustible material. The straps support a plurality of horizontally arranged louvres 44, and a base rail 46 in the usual manner. Straps 42 are supported on rollers 48 which in turn are fixed at spaced intervals to a shaft 50. The shaft in turn is supported rotatably on brackets 52 mounted on the floor 28a of the reversely bent terminal segment of the G-shaped header 16. By pulling on straps 42, or on a conventional pull cord, not illustrated, the louvres 44 may be shifted between a first position in which one of their faces is toward the front, a second position in which the other of their faces is toward the front, or to any intermediate position. This makes it possible to adjust the curtain so that it either absorbs the radiant energy entering through opening 20 or reflects it back to the exterior. This is accomplished by painting one side of the louvres 44 with a white, metallic, or other radiant-energyreflecting coating and painting the other side of the louvres with a black, or other dark coloured radiant-energy-absorbing coating. Thus, for example, when the louvres are in their Fig. 3 position, with their light coloured convex surfaces facing outwardly, they present a barrier which reflects radiant energy back into the space in which it is generated. However, when the louvres are in their Fig. 5 position, the radiant energy is absorbed by the louvres and is transmitted to the interior of the case. The venetian blind assembly may be positioned and spaced by means of the wire clips spacers indicated generally at 54 and illustrated particularly in Figs. 1 and 3. They include a central, reversely bent central segment 56 which is secured to the adjacent side wall 14 by means of bolts 58. A bent anchoring segment 60 penetrates the adjacent end of rail 46. The opposite terminal portion 62 extends downwardly and abuts against the inner front of the case, thereby insuring a properly spaced relation between the outer curtain assembly 34 and the inner curtain assembly 40. The construction of the cooperating inner curtain assembly 36 is illustrated particularly in Figs. 2 and 3. In the embodiment illustrated, the curtain comprises a sheet 66, which is preferably a corrugated sheet of highly heat conductive aluminum or other incombustible material. The use of a corrugated sheet is preferred because of its increased surface area, because it can be rolled up for packaging, and because of its increased rigidity and strength. It will be noted from Fig. 3 that curtain 66 terminates at its upper endEhort of header 16 and at its lower end short of base 12. There thus is provided a passageway which is a 'continuation of cold air inlet 64 at the bottom of the curtain and another passageway which communicates with hot air vent 32 at the upper end of the curtain. The illustrated means for hanging curtain 66 comprises a plurality of hooks 68 the upper bent ends of which are welded or otherwise affixed to the undersurface of top segment 24 of the header 1 6 and the lower bent portions of which enter openings in the upper margin of curtain 66, provided for the purpose of hanging the curtain. In carrying out the invention a number of alternatives are clearly possible. These are not illustrated, but are self evident from the foregoing description. For example, whereas in the illustrated embodiment, the cold air inlet is provided at the lower end of the case, another embodiment of the invention might provide for the introduction of cold air from the sides, either into the front convection chamber 38, or into the rear chamber 40, or into both. In any case, if cold air is introduced from the sides, experience indicates that either one or both curtains should extend either close to or all the way to the base 12 in order to maximize the chimney effect within the panel. A back wall of aluminum foil o other similar material might be placed over the combustible structural wall 10 to provide additional protection against the hazard of fire. - Instead of a single inner curtain assembly 36, there might be provided a plurality of parallel curtains spaced apart to isolate a volume of air between them. A sheet of heat absorbent glass might be placed in front of the outer louvered curtain 34 to maximise the chimney effect of convected warm air in convection chambers 38, 40. A mechanical blower might be provided to force air through the apparatus at an accelerated rate. The space behind inner curtain 36 might refilled with fibreglass or other incombustible insulation. A plurality of louvered curtains 34 might be used, and the louvres might be arranged in either vertical or horizontal configurations. The inner curtain 66 might be coated with various special coatings, for example, a selective absorbing coating which absorbs radiant heat efficiently but which does not radiate heat well, thereby absorbing heat re-radiated from front curtain 34 and from structural wall 10. Whatever the embodiment employed, the operation of the hereindescribed combination heat transfer panel and wall shield is as follows: When mounted against a combustible structural wall 10 and screening the same from a stove or other closely juxtaposed radiant heater, the heat transfer panel receives radiant energy from the radiant heater through its front opening 20. If it is desired to reflect the heat back into the space from which it comes, louvres 44 are arranged with their convex reflective surfaces facing outwardly as shown in Fig. 3. If, on the other hand, it is desired to absorb and transfer the radiant energy, the louvres are adjusted with their concave black heat absorbing surfaces facing outwardly as shown in Fig. 5. In this case the heat energy is absorbed and transferred to the first and second convection chambers 38 and 40, respectively, where a chimney effect is established. Cold air is drawn into the bottom of the unit through cold air inlet 64 and passes upwardly through convection chambers 38, 40. It exhausts from the unit through hot air vent 32. Depending upon the intensity of the radiant heat source and upon the nature of the back wall 10,, either of two treatments may be used with respect to inner curtain 66. The more radiant-energy-absorptive the curtain the greater will be the amount of heat transferred to the air flowing along its surface. Higher, too, however, will be the temperature of the back wall 10. The more radiant-energyreflective the curtain 66, the greater will be the amount of heat reflected away from itself and from the back wall 10. The result in this latter case will be a lower back wall temperature, but less heat transfer to the convected air. Different field conditions may require different treatments to realise fully both the benefits of heat transfer and of adequate wall protection. If it is desired to decrease the chimney effect, louvres 44 may be opened to various angles. A minimum chimney effect in front convection chamber 38 will result from a wide open, that is horizontal, position such as is shown in Fig. 4. If none of the above intensifying effects is required, the front of the panel may be constructed of a series of fixed louvres. Although less versatile than the system of movable louvres, the fixed louvre system will by itself intensify the conduction of heat around the unit due to the irregular surfaces of the louvres and to the increased surface exposed, as compared to that provided by monolithic flat surfaces. Inlet and exhaust air may be supplied and delivered in a variety of combinations through associated duct work or dampers, not illustrated, to suit the needs of the particular installation. Thus cooler room air may be introduced, circulated through the convection chambers and returned to either the same room, to an adjacent or upstairs room, or out of doors. Cool outdoor air may be introduced and directed either back outdoors, into the heated room, or into an adjacent or upstairs room. Adjacent room air may be introduced and circulated in like manner. In all of these applications, the unit standing closely adjacent the combustible structural wall 10 serves as a shield which prevents combustion of the wall. Accordingly, it is possible to place the stove or other radiant -heater much closer to the wall than otherwise would be possible, thereby conserving a significant square footage of floor space which then may be put to a useful purpose.

Claims: C L A I M S 1. A combination heat transfer panel and wall shield for use with non-solar radiant heaters and consisting of a case adapted for location either directly against, or in spaced relation to, a structural wall behind a radiant heater characterised in that it comprises a base (12), a header (16), and side panels (14), the front of the case facing the heater having an opening (20) to permit entrance.of radiant heat within the case, a first curtain assembly (34) mounted across the front opening (20) of the case, a second curtain assembly (36) mounted a spaced distance behind and substantially parallel to the first curtain assembly, thereby defining a convection chamber (38) between the first and second curtain assemblies, a cold air inlet (64) communicating with the lower end or with the sides of the convection chamber (38), and a hot air exhaust (32) communicating with the upper end of the convection chamber. 2. A combination heat transfer panel and wall shield as claimed in claim 1, characterised in that the second curtain assembly (36) is positioned towards the centre of the case, thereby defining a second convection chamber (40) behind the first convection chamber (38), and the cold air inlet (64) and the hot air exhaust (32) communicate with both of the convection chambers. 3. A combination heat transfer panel and wall shield as claimed in claim 2, characterised in that the first curtain assembly (34) comprises a louvered curtain assembly. 4. A combination heat transfer panel and wall shield as claimed in claim 2 or 3, characterised in that the first curtain assembly (34) comprises a venetian blind having louvres (44) adjustable between open, closed and intermediate positions. 5. A combination heat transfer panel and wall shield as claimed in claim 4, characterised in that the louvres (44) are arcuate with their convex faces coated with a radiantenergy-reflective material and their concave faces coated with a radiant-energy-absorbing material, or vice-versa. 6. A combination heat transfer panel and wall shield as claimed in claim 4 or 5, characterised in that the first curtain assembly comprises a venetian blind (44) having a bottom rail (46) and including mechanical spacers (56) fastened to the ends of the rail for spacing the curtain a predetermined distance from the second or inner curtain assembly (36). 7. A combination heat transfer panel and wall shield as claimed in claim 2, characterised in that the second curtain assembly (36) comprises a sheet having either a radiant-energyreflective surface or a radiant-energy-absorptive surface. 8. A combination heat transfer panel and wall shield as claimed in claim 7, characterised in that the second curtain assembly (36) comprises a corrugated sheet (66) and mounting means for the second curtain assembly comprises hangers (68) interconnecting the header (16) and the upper margin of the corrugated sheet. 9. A combination heat transfer panel and wall shield as claimed in any preceding claim characterised in that the header (16) comprises a structural sheet of substantially G-shaped cross section; and mounting means for mounting the first curtain assembly (34) comprises the closed, reversely bent terminal segment of the G receiving the upper end of the first curtain assembly; and mounting means for mounting the second curtain means assembly -(36) comprises hangers (68) suspended from the central segment of the G and engaging the upper margin of the second curtain means. 10. A combination heat transfer panel and wall shield as claimed in any preceding claim including dampered ducts connected to the cold air inlet (64) and the hot air exhaust (32) and arranged for withdrawing cold air from and delivering hot air to selected space areas.

Inventors: WILSON, THOMAS T.
Applicants: EPOXON PRODUCTS, INC.
Application year: 1980
Main classification: F24B3
IPC codes: F24D19, F24H9, F24C1, F24C15