US1746982A - Air heater - Google Patents

Description

Feb. ll, 1930.

H. A. ATWATER AIR HEATER Filed Nov. 14, 1927 5 Sheets-Sheet l A TTORNE Y Feb; 11, 1930. H. A` ATwATER 1.746,982

AIR HEATER Filed Nov. 14, 1927 5 Sheets-Sheet 2 A TTORNE Y Feb. 11, 1930. H. A. ATWATER 1,746,982

AIR HEATER Filed Nov. 14. 1927 5 Sheets-Sheet 3 IN VEN TOR Harig] fl. Hiv/diei, Inra/WMM ATTORNEY Patented Feb. 11, 1930 PATENT; OFFICE HARRY A. ATWATER, OF KANSAS CITY, MISSOURI AIR HEATER Application led November 14, 1927. Serial No. 233,082.

The present invention relates to heat eX- change apparatus, and aims to provide a novel, improved and more efficient apparatus for air preheating purposes through the medium of heat recovered from the waste flue gases, in connection with furnace and boiler equipment.

One of the objects of my invention is to provide an apparatus in which the heat eX- change is carried on in a more effective and economical manner, by reversing the usual method of conducting the air and heating medium through the apparatus, whereby I cause the flow of air to be preheated to take place through the space between the gas tubes or fiues and the interior wall surfaces of the housing or casing, while the hot gases are conducted in the opposite direction through said tubes or flues. i

A further object of the invention isto provide a construction in which the tendency of the parts to become warped or distorted 1s reduced to a minimum by providing` connections which permit the necessary compensat 5 ing movement in response to temperature changes at those points where more or less destructive strains would otherwise be imposed upon the connections or joints on account of such changes in temperature. In

carrying out this purpose, I provide connections between the hot gas tubes or iues and the adjacent structural work which will permit of a limited amount of relative play or slidingaction, while preventing any leakage 5 of air or gas to any such extent as would materially diminish the efficiency of the operation.

A further object of my invention is to provide hot gas tubes or flues of a type which will permit either reversal of position thereof, or convenient replacement of the units from time to time, as required.

lVith the foregoing general objects in View,

the invention will now be described by reference to the accompanying drawings, illustratino' one form of apparatus or equipment which I have devised for embodying the proposed features of improvement, after which such features and combinations thereof deemed to be novel will be forth and claimed.

In the drawings Figures 1 and 2 are fragmentary elevations illustrating a portion of the air intake side and also a portion of the air outlet side, respectively, of my apparatus;

Figure 3 is a vertical sectional elevation of the apparatus, representing a section taken on the line III-III of Figure l;

Figure 4 is a perspective view illustrating in detail a portion of the interior structure of the apparatus, comprising the tubes or tlues and spacing members;

Figure 5 is a fragmentary longitudinal sectional elevation, representing a section 'taken partly along the line V-V of Figure 7;

Figure 6 is an enlarged detail perspective showing a portion of one of the collar members for the upper ends of the gas flues or tubes;

Figure 7 is an enlarged vertical sectional detail View, taken on the line VII-VII of Figure 10 and illustrating the connections between the housing and casing and the upper 7 collar members;

Figure 8 is a horizontal section on the line VIII-VIII of Figure 7 Figure 9 is a plaif View, partly broken away, showing one of the tube spacing plates; and

Figure l0 is a broken plan view, showing a portion of the top of the apparatus.

In the usual construction of air preheating devices or recuperators, as now commonly followed, it has been the practice to conduct the air to be preheated through the several units of the flue or tube assembly, leaving' the hot gas to pass through the space between the tubes or flues and the outside casing of the 90 apparatus. In such practice, since the eX- pansion of the tubes or flues is not materially greater than that of the casing or outside housing, it is practicable to secure the tube structure rigidly and permanently in place, without providing for any compensating movement between the tube assembly and the outside framework. In all such ap paratus, however, there is present a certain amount of expansion and contraction, with particularly set the usual strains imposed upon the struetural elements, which can only be absorbed, where there is no compensating movement provided for, by a warping, twist-ing, or other deformation of these parts of the structure.

In this connection it seems that prior practice has laid undue emphasis upon the question of leakage or non-leakage ofthe parts of these preheater constructions, due to an apparently mistaken notion that the structure must be maintained practically air or gas-tight; and yet even in those constructions where permanently secured and immovable connections were provided between the tube or iiue. assembly and the outside framework, whereby an originally air-tight structure was secured, it seems quite certain that the apparatus could not possibly remain indefinitely in this air and gas-tight state, due to the necessity of the contraction and expansion strains being absorbed by the warping and distortion of the tube assembly and its connections to the outside framework.

However, wien it is remembered that the {iow of air conducted through the apparatus is at a relatively low pressure, and the negative pressure or suction of the hot gas How is a similarly weak factor, it will at once be seen that no leakage of any material consequence can take place through any small cracks or crevices wiich may be present in the tube structure or its connections, if the area of such openings is kept down to as small an extent as possible, rllherefore, if joints of a sliding character, or connections of any other compensating nature, be provided between the tube assembly and the remaining structure of the apparatus, and the areas of the crevices between the relatively moving elements of these connections be maintained as small as possible in lcomparison with the areas of the main air and gas passages there will be a negligible leakage by way of these compensating connections, since itis of course obvious that the air and gas flow will follow the least restricted course.

As has already been stated, the practice heretofore has been to conduct the air to be preheated through the ducts, or tube or flue assembly, and simultaneously to cause the hot flue gases to flow through the space between this assembly and the interior face of the casing or housing. Thus the housing or casing as well as the metal of the tubes or ducts is subjected to the extreme heat of the lue gases, so that the heat effect upon the casing is practically the same as that taking place in the tubes. In the practice proposed by my invention, a reversal of this method is adopted, in that l conduct the hot flue gases through the ducts or tubes of the flue assembly, and simultaneously cause the air to be preheated to 'liow through the space between this tube or flue assembly and the interior walls of the casing. By this method it is apparent that the stages of the temperature are stepped up more gradually from the exterior of the housing to the interior of the chiots or tubes, and the metal of the casing is not subjected to such extremes in temperature. As a result, the expansion changes in the duct-s 0r tubes are materially greater than those taking place in the casing, compared with former practice; and in addition to effecting increased economy, due to less loss of heat to the outside atinosphere, 1 am able to confine the more important variations by contraction and expansion, due to temperature changes, to the tube assembly and its connections, where the compensating features of my invention are introduced.

Referring now to the drawings in detail, these illustrate my invention as embodied in an apparatus comprising an exterior housing or casing made up of sheeting 12 supported and braced by angles 111, the top and bottom of the housing being open for the passage therethrough of the hot flue gases, while a flanged air intake opening 16 is provided through one side of the housing near the top (Figures 1 and 3), and a similar air discharge opening 18 is provided through the opposite side of the housing near the bottom (Figure 2). Jfipertiue-d plates 19 are secured to the upper corners of the housing for convenience in lifting or otherwise handling the apparatus. Opposite to the opening 18 is also provided an opening 2O for assembly and clean-out purposes, and normally closed by a sheet of asbestos 21 and plate 22, as illustrated in Figure 3.

Each of the gas chiots comprises a tube member of sheet metal. shaped to provide a relatively thin iiue element 24, open at top and bottom to permit the movement of the gases upward through the tube assembly. The tubes are of a width substantially equal to that of the interior of the casing 12, and their side margins 2al are tapered so as to widen the air space between the tubes at these points as indicated at 25 in Figures 4 and 8, and thereby forming flaring intake and outlet passages to produce stream-line effects at the openings 1G and 18, respectively.

The base framework of the apparatus includes longitudinal channels 26, to which are secured in gas-tight relation, as by welding, the ends of transversely extending collar members 2S which are of a size and shape adapted for slidingly engaging (with a snug lit) the lower ends of the tubes 2e as shown in Figure 5. Each pair of adjoining collars 28 is connected by a tapered closure portion 29 for closing up the lower ends of the air spaces between the tubes, and also forming the tapered gas inlet openings to the gas passages between the tubes, as shown in Figures 4 and 5. For further sealing effect, spacing bars 35 comprised of sheet metal packed with asbestos 36, are mounted transversely between the collars 28 and over the closure portions 29, these bars serving also to space and brace the collars and the telescoping lower ends of the tubes 24.

Inside each closure member are secured, as by welding, the lower ends of a. series of angles 30, in spaced, parallel and upwardly projecting relation, for extending the whole length of the tubes 24, and thereby bracing and stiflening the same and preventing any collapsing tendency as well as splitting up or laning the iiow of hot gases through the tubes. At their upper ends the angles 30 are secured to a strap or bar 82, whereby they are held apart in equally spaced relation.

rlhe tubes 24 are further strengthened and stitlened by means of laterally projecting fins or ribbons 34 secured by welding to one face of each tube in equally spaced and parallel relation for cooperating with the next adjoining tube in laning the tlow of air through the spaces between the tubes.

At the top of the apparatus is arranged a series of separate and independently removable collar members, in general similar in size and shape, when assembled, to those already described. ln Figure 6 is illustrated a perspective view of an end portion of one of said collar units, the same comprising a closure portion 29 connecting two side collar forming portions 28 and terminating in the flaring end 28H for fitting Within the tapered side margins 24 of the tubes. As illustrated in Figure 5, in assembling, each pair of adjoining collar units cooperates to provide the collar structure for telescoping within the upper end of one of the tubes, and an upper set of spacing bars 35 is used for spacing and bracing the parts at the upper ends of the tubes, the same as at the lower ends.

Along each side of the framework of the casing or housing, near the top thereof, I also secure to a fixed channel member 39, as bywelding, a notched spacing plate 37, with the notches or recesses 38 of said plate facing inward for embracing the converging margins 24 of the tubes, thereby holding the same apart in the proper spaced relation.

At each end of each of the upper collar members is secured an angle element 40 servine to close the ends of the closure portion 29, and also projecting into position for engagement between a pair of asbestos packing strips 41, as shown in Figure 7. Each of the upper strips 4l is engaged by a follower bar or plate 42 engaged by adjustable clamping screws 43, threaded through an angle piece 44 removably attached by bolts 45 to the upper framework. Each of the lower packing strips 41 rests upon the fixed channel member 39, and with the parts assembled as illustrated in Figure 7 it is apparent that the same are securely held together in substantially gas-tight relation, and at the same time by removal of the angles 44 and bars or lates 42, access may be had to the tube assem- Ely for removal or replacement of such tube elements as may require attention from time to time.

It is thus apparent that l have devised a practical and etlicient apparatus for carrying out thevarious desired objects ofthe invention, as above set forth. By conducting the hot gases through the tubes 24 instead of through the space between the tube assembly and the casing, a more gradual stepping up of the temperatures from that of the outside atmosphere to the interior of the tubes is obtained, with the result that the casing is not subjected to Such extreme temperature variations, and the loss of heat through the casing by radiation is reduced; at the same time there is less oxidation and scaling ed of the casing metal. The sliding and telescopic character of the joints between the tubes and collar members permits all relative movement necessary to compensate for the temperature changes in the tube assembly, and, forreasons already given, the leakage past these telescopic joints is altogether negligible, and is more than offset by the advantages gained by the compensating character of the tubes and their connections. The removable tube structure, whereby these may be reversed or replaced, is also a very desirable and practical feature in prolonging the useful life of the apparatus.

While l have herein described and illustrated what l have found vto constitute a very practical and satisfactory form of embodiment of the invention, l desire to reserve the right to make all such changes or modilica.- tions as may fairly fall within the scope of the appended claims.y y

Having thus described my invention,l what I claim and desire to secure by Letters Patent is l. An air preheating apparatus comprising a housing or casing provided with oppositely located air receiving and discharge openings, a series of liXed collar members at the lower ends of said housing, a series of collar members providing removable collar connectionsV at the upper end of said housing, and a plurality of independent conduit elements each open at both ends and slidingly connected with said collar-members at both the upper and lower ends of the housing.

2. An air preheating apparatus comprising a housing or casing provided with oppositely located air receiving and discharge openings, a series of collar members secured in fixed and spaced relation at the lower end of said housing, a series of collar members providing spaced and removable collar connections at the upper end of the housing, a plurality of conduit element-s each open at both ends and slidingly connected with said collar members at both ends of said housing, and means for closing the spaces between adjoining conduit elements at both ends thereof.

3. An air preheating apparatus comprising a housing or casing provided with oppositely located air receiving and discharge openings, a series of collar members secured in fixed and spaced relation at the lower end of said housing, a series of collar members providing spaced and removable collar connections at the upper end of the housing, a plurality of conduit elements each open at both ends and slidingly connected with said collar members at both ends of said housing, means for closing the spaces between adjoining conduit elements at both ends thereof, and combination packing and spacing bars removably mounted between the upper and lower ends of said conduit elements for spacing the same and for sealing the spaces between the ends thereof.

4. An air preheating` apparatus compris ing a housing or casing provided with oppositely loca-ted air receiving and discharge openings, a series of xed collar members at the lower ends of said housing, a series of collar members providing removable collar connect-ions at the upper end of said housing, a plurality of independent conduit elements each open at both ends and slidingly connected with said colla-r members at both the upper and lower ends of the housing, and means carried by said lower series of collar members for forming interior bracing for said conduit elements and dividing the gas flow therethrough.

5. An air preheating apparatus comprising a. housing or casing provided with oppositely located air receiving and discharge openings, a series of fixed collar members at the lower ends of said housing, a series of collar members providing removable collar connections at the upper end of said housing, a plurality of independent conduit elements each open at both ends and slidingly connected with said collar members at both the upper and lower ends of the housing, and fixed spacing devices removably engaging the upper ends of said tubes for maintaining the same in rigidly spaced relation.

6. An air preheating apparatus comprising a housing or casing provided with oppositely located air receiving and discharge openings, a series of fixed collar members at the lower ends of said housing, a series of collar members providing removable collar connections at the upper end of said housing, a plurality of independent conduit elements each open at both ends and slidingly connected with said collar members atbot-h the upper and lower ends of the housing, and means for removably retaining said upper series of collar members in communicating relation with the upper ends of said conduit elements.

In witness whereof I hereunto aix my signature.

HARRY A. ATVATER.

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