Catalytic Heater

Abstract

The invention is a tubular shaped gas operated thermocatalytic heating element formed of a ceramic fiber with a pair of adjustable reflector wings to direct the radiating energy in varying directions. The catalyst impregnated fiberous element, plugged at both ends, is axially supported on a hollow rod which also acts as a manifold for evenly dispersing the gaseous fuel through the porous element; the coupling at one end, between the rod and element, allows longitudinal movement therebetween so that expansion of the support rod is not transmitted to the element.

Description

The invention relates to gas operated heaters and more particularly to a catalytic type unit which utilizes butane, propane or natural gas as a fuel; oxidized by passages through a catalyst-coated layer of ceramic fiber. Catalytic combustion heaters have particular utility in applications such as workshops, offices, warming houses and breeding pens for farm animals, drying ovens and in particular areas where dangerous inflammable gases are present such as filling stations. Not only is catalytic combustion without flame, but due to its combustion efficiency, carbon monoxide is substantially eliminated as a by-product.

In the prior art, catalytic heaters have essentially utilized a planar element, some of which have a partial curvature (such as U.S. Pat. No. 3,024,836), while others have been dome shaped. Prior to the present invention, tubular shaped elements were not practical because of their restricted length due to the structural weakness of the unsupported ceramic fibers. Another problem is in the different co-efficients of expansion between the ceramic elements and the metal supporting structure. The expansion difference causes the weaker ceramic elements to crack or fracture. Another problem with tubular shaped elements has been sealing the ends of the tube against gas leaks. To achieve a uniform temperature along the length of the element, changes in the gas flow to the element must be effected to compensate for the increased flow resistance longitudinally through the element. This problem is described in U.S. Pat. No. 3,191,659.

The present invention has avoided all of the above mentioned problems with a tubular element of substantial unsupported length plugged at each end and supported on a hollow gas manifold rod. The element is formed from a relatively dense aluminum silicate fiber generally known in the industry under the brand name of Fiberfrax, which is a product of the Carborundum Company. The tubular shape can be molded or rolled on a mandril from a sheet. The gas manifold rod not only provides a uniform flow of gas through its length but supports the heating element at its ends. Due to coupling structure between the rod and the element, the expansion and contraction of the rod is not transferred to the element, yet a gas seal between the rod and the element is maintained. The leakage problem at the end of the elements is corrected by the use of threaded end plugs. The course deep threads of the plug cut their way into the inside surface of the fiberous element in such a manner to create a gas seal therebetween.

The tubular shape of the element is very compact in that it has roughly three times the surface area or heat output as a planar element of the same width. The radiant heat output from the upper half of the element is reflected downward off a pair of adjustable reflecting surfaces, giving a concentration of radiant heat energy over a variable area.

It is therefore the principal object of the present invention to provide a gas operated highly efficient catalytic heater which can vary the direction and intensity of its heat energy.

Another object of the present invention is to provide a catalytic heater particularly adaptable in the poultry industry as a chick brooder.

A further object of the invention is to provide a compact catalytic heater which maintains a uniform heat output over its entire area.

Another object of the present invention is to provide a catalytic heater wherein the ceramic element is held independent of the heater's supporting structure.

For a better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings and its scope will be pointed out in the appended claims.

FIG. 1 is a side elevational view of the heater unit;

FIG. 2 is an end elevational view;

FIG. 3 is a longitudinal section of the heating element to an enlarged scale with portions broken away in the center to conserve space;

FIG. 4 is a section taken along line 4 -- 4 of FIG. 1;

FIG. 5 is a section taken along line 5 -- 5 of FIG. 3; and

FIG. 6 is an exploded perspective view of the entire heating unit.

Referring now to FIGS. 1 and 6 of the drawing, the heater unit is generally identified by reference numeral 10. In viewing FIG. 6, the heater includes a tubular heating element 12 connected to a base member 14 by a pair of support brackets 15 and 16 which are all enclosed by a wire mesh shield 18. Pivotally connected to the base 14 are a pair of reflector wings 19 and 20, which can best be seen in the assembled views of FIGS. 2 and 4. Each of the wings 19 and 20 have reflective surfaces 21 and 22 on their respective undersides and mounting flanges 23 at each end thereof. The reflector wings 19 and 20, support brackets 15 and 16, and base member 14 are all fabricated by sheet metal bending and spot welding. The base member 14 has a triangular cross section with two surfaces 25 and 26 which also act as reflectors for the element 12. The sheet metal ends 27 of the base have an opening 28 for receipt of a wing nut and bolt 29. The bolt 29 attaches the support brackets 15 and 16 and the reflector wings 19 and 20 to the base member 14 through respective holes 30 and 31. Completely surrounding the the heating element 12 is a U-shaped wire mesh shield 18 with sheet metal end plates 32. A pair of flanges 33 on the edge of the shield 18 are snapped in place over the outer edges of the base 14 to retain the shield in position. The open slot 34, in the shield end plates 32, allows receipt of the extending gas manifold tube 35.

The heating element 12 made of a fiberous ceramic material 13, is tubular in shape with a substantially uniform wall thickness. The active catalyst is impregnated into fiberous material 13 by any of the means well known in the industry. Mounted in opposite ends of the element 12 are plug members 36 and 37, both of which carry a very course thread 38. Due to the softness of the ceramic fiber, the plug threads 38 will easily cut threads in the inside surface of the element 12. This threaded joint between the plug and the element provides a gas tight seal. For added strength to the element, a ceramic cement can be placed in the thread grooves of the plugs prior to insertion in the element.

Plug member 36 has a central opening for receiving the threaded nipple 39 which in turn is threaded into gas manifold pipe 35. A nut 41 is tightened against plug 36, creating a gas seal between the plug and the nipple 39. The outer end of nipple 39 is attached to a source of gas, not shown in the drawing. Some form of pressure reducing device would regulate the gas flow from a reservoir tank into the manifold pipe 35.

Plug 37 has an initial bore 42 for receiving the free end of manifold pipe 35. Bore 42 is rebored to a larger diameter opening 45 for easy receipt of the head of bolt 44. Closing the end of pipe 35 is a bolt 44 having a head diameter slightly greater than the diameter of opening 42, thereby preventing removal of the pipe 35 from the plug 37. Threaded into the outer end of opening 45 is a closure cap 47 which prevents any gas from escaping from the opening 45 in the plug 37. Due to the space on both sides of the bolt head 44, the pipe 35 is free to move longitudinally independent of plug 37 as the pipe 35 expands and contracts. The manifold pipe 35 has a series of gas outlet holes 50 spaced along its length. The spacing between the holes 50 from the gas inlet end toward the closed end decreases for reasons hereafter described. The diameter of the holes are small enough to create adequate defusion of the gas so that there will not be hot spots on the outer surface of element 12.

The carrier material 13 used in the heating element is an aluminum silicate; a ceramic fiber commonly known under the brand name of Fiberfrax, a product of the Carborundum Company. Other types of silicate fibers or any high temperature resistant fiber may be used. The catalytically active material is impregnated or coated on the fibers by different methods well known in the trade. While platinum is the catalyst generally used, other active elements can be used. While not shown in the drawing, the catalytic element 12 can be molded with a wire mesh tube concentrically therein for added structural rigidity.

OPERATION

As distinguished from a planar type catalytic heater which radiates in one direction, the tubular element 12 radiates heat energy in all directions. In viewing FIG. 4, the heat radiating from the upper half of the element 12 is reflected downward off the reflective surfaces 25, 26, 21 and 22. By loosening wing nuts 26, the reflector wings 19 and 20 can be moved to vary the direction and intensity of the heat. When not in use, the wings can be folded together surrounding the heating element 12.

When the unit 10 is in operation, gas under pressure is supplied to manifold pipe 35 through inlet nipple 39. The gas passes through the small openings 50 at a high velocity into the air space 51 surrounding the pipe. Due to the high velocity flow through the openings, there is adequate turbulation in the air space to effect an even gas flow out through the porous element 13.

When the catalytic element 12 has reached its operating temperature, the metal manifold pipe 35 will have expanded in length an increment greanter than the ceramic element 12, due to their different co-efficients of expansion. Since the plugged end of pipe 35 is free to move longitudinally in plug 37, this expansion is not passed on to the delicate ceramic element 12.

It is understood that variations from the form of the invention disclosed herein may be made without departure from the spirit and scope of the invention and that the drawings and specification are to be considered as merely illustrative rather than limiting.

Claims

Having described the invention with sufficient clarity to enable those familiar with the art to construct and use it, I claim:

1. A thermocatalytic heating device which is supplied gas under pressure comprising:

a base support means;

a tubular shaped catalytic heating element having open ends composed of a catalyst-coated gas permeable ceramic fiber;

a pair of self-threading plug members each threaded into an open end of the element in gas tight relation; and

a gas manifold pipe connected to the base means, passing through the heating element and each plug member in supporting gas tight relation, said pipe having an inlet for supplying gas therein and coupling means between one of the plug members and the manifold pipe allowing the plug to slide longitudinally on the pipe whereby contraction and expansion of the manifold pipe are not transmitted to the ceramic element.

2. A thermocatalytic heating device as set forth in claim 1, including a liquid ceramic cement in the threads of the plug members prior to threading the plug into the element whereby the bond is strengthened between the fiberous element and the plug member.

3. A thermocatalytic heating device as set forth in claim 1, wherein each plug member has a concentric opening therein for receiving the manifold pipe, one of which passes only partially through the plug; said coupling means being between the plug with the partial opening and the manifold pipe which allows the manifold pipe to move longitudinally independent of the plug member, whereby expansion and contraction of the manifold pipe is not transmitted to the ceramic element.

4. A thermocatalytic heating device as set forth in claim 1, wherein the ceramic fiber is aluminum silicate and the catalyst coating is platinum.

5. A thermocatalytic heating device as set forth in claim 1, including movable reflector means attached to the base support for directing the radiating energy in varying directions.

6. A thermocatalytic heating device as set forth in claim 1, including a pair of reflectors longitudinally positioned with respect to the element, pivotally attached at their ends to the base means for directing the radiating energy from the element in a specific direction.

7. A thermocatalytic heating device as set forth in claim 1, wherein the ceramic fiber is aluminum silicate with a density of between 10 and 20 pounds per cubic foot and the catalyst is platinum.

8. A thermocatalytic heating device as set forth in claim 1, including longitudinally spaced perforations in the manifold pipe, the spacing between the perforations decreasing from the gas inlet end, whereby more even dispersal of gas throughout the length of the element is provided.