US2200549A - Indirect air heater - Google Patents

Description

May 14, 1940- H. L. GRAPP 2,200,549

INDIRECT AIR HEATER Filed April 4, 195s 2 sheets-sheet 1 1719.1 f5 ff www May 14, 1940. H. GRAPP INDIRECT AIR HEATER Filed April 4, 1938 2 Sheets-Sheet 2 I--- r- Il l rf MW pw .IVI n/.r JF f w f A T@ ma @indented May 14, 194() UNITED STATES PATENT ortica 2 Claims.

This invention relates to a heating device and particularly to such a device for heating a gas such as air. More specifically the invention relates to what is known as an indirect heater.

Such heaters are used to heat air to quite a high temperature and this heated air is used in various industrial drying and baking processes as in ovens where various objects have a coating dried thereon. Such heaters may also be used for space w heating. The type of the invention is that wherein the air is heated by a furnace which may use any suitable fuel such as gas or oil.

It is an object of the present invention to provide such a heater of simple, highly eflicient and inexpensive construction, and which can be easily assembled.

It is more specifically an object of the invention to provide such a heating device adapted to be disposed over a furnace and comprising a casing having extending vertically therethrough a plurality of rows of fiat narrow tubes through which the products of combustion from said furnace pass, means being provided for circulating air between said tubes in a circuitous path.

It is a further object of the invention to provide an indirect heater comprising a casing adapted to be disposed over a furnace having vertical side and end walls and novel top and bottom plates adapted to receive and support a large number of tubes extending therebetween through which products of combustion pass and between which the air to be heated is circulated,

said tubes being arranged for convenient cleaning.

These and other objects and advantages of the invention-will be fully set forth in the following description made in connection with the accompanying drawings in which like reference characters refer to similar parts throughout the several views and in which:

Fig. 1 is a view in vertical section taken substantially on line i--l of Fig. 2;

Fig. 2 is a view partially in top plan and partially in horizontal section taken substantially on 415 line 2--2 of Fig. 1; i

Fig. 3 is an end view of the heater as seen from the right of Fig. l;

Fig. 4 is a partial plan view of one of the tube holding plates, some tubes being shown in hori- 50 zontal section; f

Fig. 5 is a section taken on line 5-5 of Fig. 4 as indicated by the arrow; and

Fig. 6 is a partial perspective view of one of the j tubes used.

55 Referring to the drawings a device forming an indirect heater is illustrated, the same comprising a casing designated generally as l0 which is adapted to be disposed above or over a furnace. In the embodiment of the invention illustrated a furnace is indicated having end frames formed of vertical side angle members Il and transversely extending angle members l2. A channel member I3 extends about the top of the furnace, vertical plates or wall members M being shown as disposed between angle members Il and l2 and the 1 channel i3. The furnace is supported by vertical channel members l5 extending to channel I3, which support transverse angle members I6. Angle members i6 in turn support longitudinally extending bars l1 upon which are placed the brick I8 forming the bottom of said furnace. Brick I9 form the end Walls of said furnace and extend between members i6 and channel members i3. The furnace may have an inner lining material 20 and the furnace chamber has therein open brickwork 2l. Some suitable fuel burner such as an oil or gas burner will be disposed within said furnace, one end wall of which will be provided with a suitable opening la through which the burner or fuel supply conduit may extend.

The furnace described is one of somewhat usual construction and per se forms no part of the present invention. Casing l0 has a bottom plate ma which has side and end portions resting upon the channel members i3. A top plate lllb is provided which is a counterpart of plate I0 but reversely disposed and spaced above the latter a distance equal substantially to the height of casing il). Casing l0 has a frame extending thereabout at each end comprising the vertical angle members |00 and the top and bottom horizontal angle members ld. Spaced vertical plates ille extend across casing Hl and suitable insulating material 22 is disposed therebetween. Casing l0 will also have suitable vertical side walls lf supported by the vertical angle members lc. Plates l0 and lb have on their adjacent faces a plurality of rows of recesses lng. These are shown as rectangular in form and are formed by transversely extending projecting ribs Ih extending in parallel relation across plates Illa and lb and the spaced ribs lllz which extend between and join the ribs Ih. Within each recess log is a projecting oblong rib lily' having closely adjacent parallel sides and semi-cylindrical ends, each of said ribs |07' defining anl opening lilla through its plate. It will be noted as shown in Figs. 2 and 4 that the ribs |051' are in staggered relation, said ribs in one row being disposed centrally between the ribs in the adjacent row. Plates Illa and |0b each have a rib IUm extending thereabout atthe side opposite the ribs |07'. v A plurality of tubes 23 extend between plates I 0 and I 0b and have their ends respectively fitting over the ribs |09' in said plates. Suitable securing material 24 such as a heat resisting or asbestos cement may be disposed in the recesses |0g about the ends of tubes 23. Inner side plates |09' extend between plates Ia and |0b having their lower portions secured in an outer groove |0p by suitable cement. The tubes 23 may be of seamless or other convenient construction but in Fig. 6 a portion is shown made of one piece of metal bent into oblong form and having short projecting ribs 23a at one end of the tube which may be joined in any suitable manner as by welding. A plurality of horizontal partition forming plates 25 extend across casing I0 between the side walls IDf, said plates connecting with one end of casing I0. It will be noted that alternate partitions 25 have their ends spaced some distance from opposite ends of casing I0. Small curved plates 25a. are disposed at the ends of plates 25 engaging the end walls of the casing, one of said plates also being disposed at the lower rear corner of casing IU. An air inlet conduit 26 extends through the front end wall of said casing and thus through the plates Ille, the bottom of which is substantially aligned with the uppermost partition 25. An outlet conduit 21 also extends through the front end wall of said casing, the top of which is substantially aligned with the lowermost partition 25. As shown in Fig. 3 conduits 26 and 21 extend substantially the full width of casing |0. A vent hood 28 illustrated as made from sheet metal extends over the top of plate Illb so as to enclose all of the openings IUk, the same having flanges secured to plate |01) by the screws 29. Said hood is provided with a suitable opening at its rear end for the outlet of the gases of combustion and the same is shown as having a handle 30 on the top thereof. A plate 3| may be secured at each side of casing l0 extending throughout the length and heighththereof spaced therefrom and having flanges at its edges secured by screws 32 to angle members |0d. Suitable insulating material 33 may be disposed between plate 3| and the sides of casing l0.

In operation the furnace comprising members I to 2| will be suitably red and the hot products of combustion will pass upward therefrom through the tubes 23. These products of combustion will pass into the vent hood 28 and will be led therefrom through a suitable conduit. Air will be blown into inlet conduit 2B and will pass into casing l0 and between the tubes 23 above the uppermost partition 25 to the rear end of the casing and will return below said partition and above the next adjacent partition 25 to the front end of casing I0 when it will again travel toward the rear end of casing I0 between tubes 23 above the lowermost partition 25 and will then return below said lowermost partition to and through a discharge conduit 21. 'Ihe air will be directed by conduit 21 to the desired point of use.

It will be noted that the air cannot take a straight path through the casing IIJ between tubes 23 but must change its course at each row of tubes due to the staggered relation of said tubes. The tubes have a large contact surface for the air and the air is quickly heated to a high degree by travelling in contact with said tubes, said air being heated both by radiation and convection. It will be noted that the air nearest the outlet conduit 21 encounters the hottest part of the tubes or the part which is heated by the hottest products of combustion. As stated, the large area of surface on the tubes and the arrangement thereof results in an eicient heating of said tubes and a very efficient heating of air travelling thereabout.

From the above description it will be seen that I have provided an extremely efficient heating device and one that is quite simple in construction. The device is compact and the space within the casing Ill is used to maximum eiliciency. The tubes are simple in form and are easily made and assembled. An important feature of the heater is that the tubes can be very easily cleaned. By removing the vent hood 28 which is easily done, a cleaning device can be moved vertically down through the tubes and the tubes thus cleaned of any deposit. The inner sides of the tubes are unobstructed and the cleaning can thus be easily and quickly accomplished.

The header plates |0a and lb are made of a cast alloy having appreciable percentages of chromium and nickel. In practice the plates have been found to `be very satisfactory when containing 11/2 percentage each of chromium and nickel. The cast plates are quite durable and do not tend to grow, that is to permanently expand and crack as a result of high temperature. The non-metallic packing or securing material 24 makes for easy assembly of the device and for quick and convenient removal of a tube should this be necessary.

The device has been amply demonstrated in actual practice, found to be very successful and eflicient and is being commercially made.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the parts, without departing from the scope of applicants invention, which generally stated, consists in a device capable of carrying out the objects above set forth, in the parts and combinations of parts disclosed and dened in the appended claims.

What is claimed is:

1. An indirect heating device adapted to be disposed over a source of hot gases of combustion having in combination, a casing having top and bottom plates, a plurality of rows of tubes extending between said top and bottom plates, said tubes having at parallel sides, said plates having openings therethrough alned with the openings in said tubes and having grooves extending about said openings therein in which the ends of said tubes are disposed and high temperature resisting material in said grooves about said tubes for holding the same in place whereby the ends of said tubes are protected from the hot gases passing therethrough and means for passing air longitudinally through said casing about said tubes.

2. An indirect heating device adapted to be disposed over a furnace having in combination, a casing having insulated vertical side and end walls and a bottom plate overlying said furnace, a plurality of rows of tubes extending from said bottom plate, said tubes having flat parallel sides and being very elongated in horizontal cross section, said tubes having their sides extending lengthwise of said casing, the sides of adjacent tubes being in close proximity, said bottom member having openings therethrough with which said tubes aline so that the hot products of combustion from said furnace rise through all of said tubes, a top plate over said tubes having openings with which said tubes aline, the ends of said tubes being disposed in said top and bottom 75 plates respectively, an inlet conduit extending into said casing adjacent said top plate, a plate extending horizontally from the bottom of said conduit around said tubes to the opposite end of said casing, an outlet conduit at the end of said casing below said inlet conduit and adjacent said bottom plate, a plate alined substantially with the top of said outlet conduit extending horizontally about said tubes to the opposite end of said casing and a plate extending from the end of said casing opposite said conduits around said tubes to adjacent the end of said casing with which said conduits connect whereby air entering said inlet will pass around said plates and said tubes to said outlet conduit. HERBERT L. GRAPP.

Images