US2137870A - Heating apparatus - Google Patents

Description

NOV. 22, 1938. J r; WOQDSON 2,137,870

HEAT I NG APPARATUS Filed Dec. 30, 1957 2 Sheets-Sheet 1 Fig.2..

XNVENTOR N; N James QwoodSbn Nov. 22, 1938. J. c. WOODSON HEATING APPARATUS Filed Dec. 30, 1957 2 Sheets-Sheet 2 INVENTOR Jam es C. Woodson MZM I 35 certain modifications.

Patented Nov. 22, 1938 PATENT OFFICE HEATING APPARATUS James 0. Woodson, Cleveland, Ohio, assignor to Lee Wilson Sales Corporation, a corporation of Ohio Application December 30, 1937, Serial No. 182,504

1 Claim.

in particular, to a heat exchange tube for a furnace such as that disclosed in Wilson Patent No. 1,952,402.

'5 Heat exchange tubes for installation in furnaces of the type shown in said patent have heretofore been cast from alloy steel which remains rigid at elevated temperatures. These castings are relatively costly and it is an object of the present in- 10 vention to provide heat exchange tubes which are less expensive to manufacture, which are equally as eflicient as the cast tubes, if not more so, from the standpoint of heat transmission, and have other important advantages. In accordance 15 with my invention I provide a heat exchange tube, the straight portion of which is fabricated from flat stock by bending it to cylindrical form and welding the abutting edges. One or more cast elbows associated with the fabricated portion 20 completes the tube. The elbows preferably have a thicker wall section than the-straight portion of the tube to resist the abrasive effect of the combustion gases and the elbows are also swelled out between their ends. An assembly of such elbow 25 or elbows and a fabricated straight tube provides a composite heat exchange tube in which relative movement of the parts is permitted on expansion and contraction thereof, thus entirely avoiding the stresses set up in an integral tube on heating 30 and cooling thereof.

A complete understanding of the invention may be obtained from the following detailed description thereof referring to the accompanying drawings illustrating a preferred embodiment with In the drawings:

Figure 1 is a partial transverse section through a furnace of the same general type as shown in the aforementioned patent, with the invention incorporated therein;

40 Figure 2 is a partial longitudinal sectional view of the furnace;

Figure 3 is a view partly in section and partly in elevation showing the construction of my composite tube in detail;

45 Figure 4 is an elevation of the lowerelbow of Figure 3;

' Figure 5 is a plan view thereof; and

Figure 6 is a partial sectional view showing a modified form of upper elbow.

50 Referring now in detail to the drawings, the A furnace indicated generally at l comprises a heating cover. removably disposed on a base l2. The base comprises a hearth l3 'supported on a structural framework indicated generally at 55 14 having piers l built up thereon for supporting zontal portions 23. v L upper ends ofthe stack portions 21, a sealing This invention relates to heating apparatus and,

charges of material to be treated such as stacks of sheets I 6. Protective covers [1 are disposed over the stacks with their lower edges seated in sealing channels l8.

The heating cover comprises a refractory lining 5 IS in a structural frame 20. Heat exchange tubes 2| have vertical portions 22 and horizontal portions 23 and 24, the latter extending through openings in the side walls of the cover II. The heat exchange tubes are spaced along the side walls and may also be installed on the end walls of the heating cover. The horizontal portions 23 and 24 have elbows 25 and 26 formed integral therewith. A stack portion 21 extends upwardly from the horizontal portion 23, A refractory lined passage 28 encloses the lower ends of the stack portions 21 and the outer ends of the hori- Seals 29 are provided at the channel 30 being formed on top of the passage 28.

Burners 3| extend into the horizontal tube portions 24 and are connected to a fuel supply main 32 carried on brackets 33 secured to the framework of the cover ll Referring now more particularly to Figures 3 5 through 6 for a detailed showing of the tubes 2|, it will be seen that the fabricated portions 22 thereof have a thinner wall section than the cast portions 23 and 24. It will also be observed that the latter are provided with reduced ends 34 which cooperate with the lower and upper ends of the portion 22 to form bell and spigot joints. These joints may be made permanent by welding as at 35 if desired. Expansion and contraction of the resulting unitary tube is permitted by the clear- 35 ance between the portion 23 thereof and the side wall of the furnace asshown in Figure 1. It will also be observed that the elbows 25 and 26 aresomewhat larger in cross-sectional area than the horizontal sections 23 and 24. This permits combustion gases from the burners 3| to sweep around the elbows with a minimum of abrasion or scouring of the latter.

A, modified form of upper elbow is shown in Figure 6 at 36. Like the tube portions 23 and 24,

elongated horizontal portion 38 having an elbow 39 and a vertical portion 40 extending upwardly through the roof of the cover and having seals 4| at the upper ends thereof. Hangers 42 depending from the roof of the cover provide. support for the inner ends of the tubes. The outer ends are fixed in the wall of the cover, in the same manner as the horizontal tube portions 24. Burners 43 are mounted in the vertical tube portions 38 and are supplied with fuel from a main.

The vertical portions 40 of the tubes shown in Figure 2 are preferably fabricated by forming and welding flat stock, in the manner already described with reference to the vertical tube portions 22. The elbows 39 are similar to those shown at 26 while the horizontal tube portions 33 are similar to the tube portions 24 except that they are longer. Alternatively, the horizontal portions 38 may also be fabricated froinflat stock and connected to the elbows 33 by bell and spigot joints such as illustrated in Figure 3. The vertical tube portions 40 have tabs 45 welded thereto with slots 46 therein. These slotted tabs engage studs 41 welded to the elbows 39, thus providing a relatively loose connection between the Vertical and horizontal tube portions. This permits expansion and contraction of the tube portions 38 and 40 without introducing undesirable stresses into these parts. The hangers 42 include rollers 48 which facilitate expansion and contraction of the horizontal tube portion 38.

The thickness of the wall of the vertical tube portions 40 is less than that of the elbows 39,

the ratio of thicknesses being about as shown in Figure 3. The same is true ofthe horizontal tube portions 38 if they are fabricatedinstead of cast integral with the elbows 39.

It will be apparent from the foregoing explanation that the heat exchange tube disclosed possesses marked advantages over similar tubes as heretofore constructed, from the standpoint of manufacturing cost, thermal efliciency and useful life. The portions of the tube subject to the greatest wear, viz., the elbows where the direction of the combustion gases is changed, are composed of castings having a wall thickness sufflcient to stand the abrasive or scouring action of the gases for long periods of time. The vertical portions of the tubes, being fabricated from flat stock somewhat thinner than the walls of the cast elbows, have ample strength and, at the same time, are more eflicient from the standpoint of heat transfer than tubes cast in one piece with substantially the same wall thickness throughout. The vertical portions of the tubes, obviously, are subjected to relatively little scouring action by the gases passing therethrough. The advantage of the composite tube shown in Figure 2 in avoiding stresses due to expansion and contraction has already been mentioned as has also the fact that provision is made for free expansion and contraction of the tubes of the type shown in Figure l, the parts of which are permanently attached by welded joints. Even without this special provision, "the flexibility of the vertical tube portions 22 resulting from their relatively thin wall section permits them to compensate for considerable expansion and contraction without stressing the cast portions 23 and 24 to a serious degree.

Although I have illustrated and described herein but a preferred embodiment of the invention with certain modifications, it will be understood that changes in the construction disclosed may be made without departing from the spirit of the invention or the scope of the appended claim.

I claim:

- A radiant heating element adapted to be mounted within an enclosure to be heated, such as a furnace, said element comprising a substantially cylindrical tube for conveying hot fluids and an elbow communicating with one end of said tube, said elbow having one end of substantially the same size as said tube and an intermediate portion swelled out to provide a sectional area substantially greater than that of said tube. v

. JAMES C. WOODSON.

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