US3127876A - Heavy duty fluid heater - Google Patents

Description

Apri-l 7, 1964 A. A. OLSON 3,127,876

HEAVY DUTY FLUID HEATER Filed June 30, 1961 3 Sheets-Sheet 1 ARTHUR A. OLSON BY L7 ATTO EY Apnl 7, 1964 A. A. OLSON 3,127,876

HEAVY DUTY FLUID HEATER Filed June 3o, 1961 s sheets-sheet 2 1I FIG. e

INVENTOR ARTHUR A. oLsoN FIG. 4 35 BY mf Aog April 7, 1964 A. A. oLsoN 3,127,876

HEAVY DUTY FLUID HEATER Filed June 50, 1961 5 Sheets-Sheet 3 FIG. 5

/ INV ENTOR ARTHUR A. oLsoN lo 2 ATTORNY United States Patent O 3,127,376 HEAVY DUTY FLUID EEATER Arthur A. Glson, 4156 Windsor Aye., Youngstown, @hin time sa, taai, ser. are. raides 4 Claims. (6E. 12in-276) This invention relates to apparatus for heating fluids, primarily but not necessarily air, and is concerned with improved features of construction for such apparatus to render the same practical for very heavy duty. Thus, the invention deals with a iluid heater of the kind suitable for heavy industrial service and for furnishing very large volumes of high temperature air, for example, for such uses as metal-melting cupolas, as an initial heating stage for metallurgical blast furnaces, and as an initial heating stage for supplying high temperature air to wind tunnels. In apparatus of this nature the requirement of practical operating efliciency as well as considerations of construction, useful life, and maintenance poses certain problems which are sought to be overcome by the principles of the present invention.

The primary object of the invention is the provision in apparatus of the general character and for the purposes enumerated above of an arrangement whereby a simply designed and relatively inexpensive heat-exchanging assembly may be subjected to an extraordinarily high rate of heat input without excessive deterioration of the clements of the assembly and while yet achieving a high degree of operating eiliciency.

A further object of the invention is the provision in apparatus of the kind outlined above of a practical arrangement wherein the heat-exchanging assembly may be constructed as a unit separate from the combination comprised of the outer shell or casing and the burner; its various connections, and fiue components to facilitate the construction and erection of the apapratus as well as the inspection, maintenance and repair thereof.

The above and other objects and advantages of the invention will become apparent upon consideration of the following specification and the accompanying drawing wherein there is illustrated certain preferred embodiments of the invention.

In the drawing:

FIGURE 1 is a vertical section through a gas-tired air heating furnace constructed in accordance with the principles of the invention;

FIGURE 2 is a horizontal section taken along the line II-Il of FIGURE 1;

FIGURE 3 is a fragmentary elevation of a detail of construction of the apparatus of FIGURE 1;

FIGURE 4 is a fragmentary plan view of another detail of construction of the apparatus of FIGURE 1;

FIGURE 5 is a fragmentary side elevation of the apparatus of FIGURE 1, showing the heat-exchanging assembly thereof in partially withdrawn position; and

FIGURE 6 is a vertical section through a slightly modilied form of the apparatus of FIGURE 1.

In the illustrated embodiments of the invention there is provided astructural steel frame 10 which supports, in elevated position, the suitably insulated bottom wall 11 andcylindrical side wall 12 of the combustion chamber of the apparatus. Extending centrally through the bottom wall 11 is an upwardly directedrefractory burner port 13 which is supplied with a suitable combustible mixture by theburner 14 which may be of conventional construction. Burner 14 is supplied with gas through aline 15 and with air under pressure from ablower 16 which may be conveniently housed in a building or enclosure outside of the general circumference of the heater. In actual practice, theburner 14 and its supply conduits and controls are so selected that a very high rate of heat input may be attained and this requires, of course, the exist- V. ICC

ence of a very hot high-velocity column of gaseous products above theport 13. Normally the radiation effect :from such a flame would be highly damaging to closely adjacent heat-exchanging elements, and, as will appear below, some of the more important features of the present invention involves the arrangement and disposition of these elements als well as a flow pattern for the gaseous products whereby the deleterious effects of the radiatron are minimized.

The upper end portion of thecylindrical side wall 12 of the combustion chamber Iis formed or ahollow metal annulus 17. At least the upper portion of the inner cylindrical wall 1S of thisannulus 17 is open to the combustion chamber so that products of combustion may enter into the annulus from the combustion chamber and be exhausted out through a suitable flue or flues, not shown, which in practice are connected to theannulus 17. It should be noted at this point that the inner surface of thewall 18 is aligned with the inner surface of thewall 12 and that the top wall (19) of theannulus 17 is a Jlat annular ring which forms a support for the heat-exchanging assembly now to be described.

The heat-exchanging assembly of the apparatus is mounted on a fabricated inverted cup-shaped housing 2i) having alower flange 21 adapted to overlie and be supported on theflat ring 19 when the parts are completely assembled as shown in FIGURE 1. As shown in this latter ligure, there is secured within the housing 20 a pair of two vertically spaced toroidalshaped tubes 22 and 23, the lower one 23 of which may be taken as the air inlet header while the upper one is used as the air outlet header. Suitable inlet andoutlet conduits 24 and 25, respectively, may be coupled with these headers to conduit the ow of air. It should be understood that theheaders 22 and 23 are made of suitable metal and are fixed in thehousing 20 by welding, for example. In practice, theoutlet header 22 is made of high quality alloy steel while the inlet header may be made of ordinary carbon steel. As shown, the side wall of thehousing 20 outwardly of theheaders 22 and 23 as well as the top wall of the housing above theupper header 22 and within this latter header are suitably insulated. The top wall ofcasing 20 and the insulation carried thereby is formed with a centrally disposedaperture 26 to slideably receive aplug assembly 27 which serves as an observation port and as an access and pressure relief door as will be understood.

Connected at their upper ends into theheader 22 and at their other ends into theheader 23` are a multiplicity of generally deep U-shaped air-conductingtubes 28 which are preferably made of heat-resistant stainless steel and are connected to the headers `122 and 23 preferably by welding. The lower lobes of thetubes 23 are looped inwardly, as shown at 29, to provide ease of expansion and contraction and thereby prevent excessive strains at the points of juncture with headers Z2 and 23. Rigidly secured -to and depending ydownwardly `from the inner surface of thelower header 23 is acylindrical metal bale 30 which is imperforate and which extends well down into theloops 29 of the tubes 2S. Thisbaille 30 is also preferably formed of heat-resistant stainless steel.

To obtain la maximum amount of heat-exchanging surface and for another important purpose to be later described a suicient number of thetubes 28 are employed to give a `double ring of both the radially inward and radially outward reaches of the tubes, as shown in FIG- URE 2. Further, the `diameters of theindividual tubes 23 are so chosen in relation to their number and spacing that the radially inward reaches of the tubes effectively screen thebafe 30 from the sight of the vertical projection of theburner port 13.

In the operation of the apparatus, `air or other fluid to be heated is supplied to theheader 23 under considerable pressure so that the fluid passes through thetubes 28 at a -fairly high velocity. Because of the parallel arrangement of the respective tubes, the same pass substantially equal amounts of fluid so that the tubes attain a uniform temperature. Also, the velocity of the fluid in the tubes is such that the metal of the tubes while attaining a tfairly high temperature will be maintained wit-hin a safe operating temperature range even though an enormous quantity of heat is being emitted by theburner 13, 14. contributing, however, to the protection of the inner reaches of thetubes 28 and the baffle 30y is the rapid downward flow of an annular column of the products of combustion which wipes downwardly longitudinally along said inner reaches. It is obvious that if the iiame is emitted from the burner at high velocity and in a jet-like stream, .the same will tend to proceed to the top wall of the combustion chamber but since the top portion of the combustion chamber is closed, the llame pencil or stream will tend to mushroom out as it approaches the top of the combustion chamber and thereafter the products of combustion will proceed downwardly in the annular column as aforesaid. It will be understood that high intensity fluid heaters of the general kind involved herein are normally operated with a high forced draft. The intense heat of the flame is somewhat dissipated during the mushroomin g yaction aforesaid so that no intense radiation is emitted from the downwardly moving annular column of gases, and while these gases are largely transparent they appear to have an effective insulating etfect against the intense radiation of the centrally disposed and upwardly flowing pencil of dame. Also, the rapid upward ow of hot gases immediately above theburner port 13` has an aspirating effect of drawing cooler gas from the region of the bottom of inner reaches of thetubes 28 into sheathing relation about the center hot core of the flame and keeps the combustion chamber temperature within safe limits. In any event, the spacing of the inner reaches of the tubes 2b effectively `shields thebaffle 30 from this radiation so that the baiie is maintained within safe operating temperature. While, of course, appreciable radiation does impinge on thetubes 28, the rapidly moving duid in the tubes keep the same at a safe temperature as explained above.

Dur-ing normal opera-tion of the apparatus, the inner reaches of thetubes 28 expand much faster than the outer reaches of the tubes during warm-up periods and may remain at a higher temperature and thus remain expanded to a greater extent during `stable conditions of operation. This tends to throw the bottom portions or loops of the tubes radially outward, and to maintain the tubes in proper positions, I provide an abutment on the outer reach of each of thetubes 28. As shown in FIGURE 3, this abu-tment consists of aweb 30 which is welded longitudinally onto thetube 23 and to which in turn is welded a length ofbar 31. As shown, the ends of thebar 31 project above and below the web Ztl and are bent inwardly as shown at `52 to act as runners when the heat-exchanging assembly is slid into and out of the combustion chamber. The assembly is so fabricated that the bars or shoes 3:1 have a loose sliding fit with the inner surface of thecylindrical wall 12 of the combustion chamber. In operation, if the bottom portions or loops of the tubes tend to move radially outward, any excess movement is effectively restrained by engagement of theshoes 31 with theside wall 12. As shown more clearly in FIGURES l and 2, theside wall 12 is a composite affair having anouter steel shell 33 which adequately resists any radially outward forces which may be exerted by the `shoes 31.

Positioned radially outward of thecylindrical baffle 30 and encompassing the outer reaches of thetubes 28 is a plurality of spirally disposed baffles 34 which are shown schematically in FIGURES l and and more in detail in FIGURE 4. Thesebaffles 34 each consists of aninner sheet metal ring 35 (which is preferably made in sections) and an outer ring 36 (also preferably made in sections). Therings 35 and 36 are notched as shown in FGURE 4 to receive thetubes 28 and the radial dimensions of the rings are such that the rings may be overlapped as `shown and secured together by suitable means, not shown. The thus assembled baflies 34 are secured to the tubes 2S at `spaced points preferably by welding so that the baffles will remain longitudinally fixed on the tubes. The outer 'diameters of the baffles 3'4 are made slightly smaller than the inner diameter of thecombustion chamber wall 12 so as not to impede the sliding movement of the heat-exchanging assembly into and out of the combustion chamber.

The effect of the :spiral baflies 34 is to cause the heating gases which enter the annular passage at the bottom of thebaffle 30 to move upwardly toward the breaching 17 in a spiraling manner whereby the passage length is increased and whereby the gases pass over theheatex changing tubes 28 substantially normal to the longitudinal axis of these tubes. This results in a greater absorption of heat from the products of combustion before the latter yleaves the furnace and thus in a greater efficiency of operation.

Referring again to FIGURE l, it will be observed that both theheaders 22 and 23 as well as the connections from thetubes 28 into these headers are all effectively within the insulated combustion chamber of the combined apparatus and since these headers and connections are of metal having a high coeflicient of heat transmission, such as stainless steel, the total effective heat exchanging surface is materially increased and there is excellent economy in the use of the metal. Therefore, in relation to the overall cost of the combined apparatus, a maximum output of heated uid may be obtained. For high pressure operation, the toroidal shaped headers are ideal since it is well understood that a round pipe or tube Will retain a maximum degree of fluid pressure for a given side wall thickness. These headers, however, are rather expensive in material and fabricating cost and are normally used only for high pressure service. If the fluid to be heated is circulated under low pressure, the construction shown in FlGURE 6 will normally be preferred.

ln the embodiment of the invention shown in FIGURE 6, the normally fixed portion of the apparatus comprised of theframe 19, the bottom andside walls 11 and 12 and theburner port 13 as well as theannular flue 17 is identical with that of the first described embodiment. The upper or removable housing of this embodiment, designated by reference numeral 20', is somewhat modified to replace the toroidal shaped headers with annular box-shaped headers Z2 and 23 which are cheaper to construct. In this embodiment of the invention, theannular inlet header 23 in itself forms the side wall of thehousing 20 and also provides the ange which rests on the annular supportingring 19 of the normally fixed component of the assembly. Theheader 23 is somewhat enlarged to receive a large volume of cold fluid to be heated and it will be understood that this body of fluid provides sufficient insulation for the side wall of thehousing 20. Theoutlet header 22 is positioned concentrically within theheader 23 to facilitate connection of the heat exchanging tubes and to position the same in exposed relation within the combustion chamber toincrease the total heat exchanging surface. The heat exchanging tubes, herein designated by reference numeral 28', are generally similar in design and function with the tubes 2S of the first described embodiment but it should be observed that the concentric relation of the headers Z2 and 23 permit the upper ends of these tubes to remain straight. They are thus easier to form and easier to connect to the at bottom walls of the headers.

In both embodiments of the invention, the upper ends of the fluid-conducting tubes are connected to the headers in staggered relation to permit the large number of tubes illustrated to be employed-otherwise there would be insufficient circumferential space at the header receiving the upper ends of the inner reaches of the tubesand to permit the screening the baille 30 from the very hot flame ejected by theburner 13, 14. In the embodiment of FIGURE 6, the baille 3i? is secured by welding to the lower inner edge of the header 23', both the header 22' and theheader 23 preferably being constructed of weldable steel.

While the above description deals specifically with gasred furnaces it should be obvious that all the principles of the invention are equally applicable to oil-fired heaters.

It should now be apparent that I have provided an improved uid heating furnace for heavy industrial uses which accomplishes the objects initially set out. By the use of the principles of the invention, it is possible to construct units of enormous capacity as regards fluid volume, pressure and temperature which are practical in concept and efficient in operation. Maximum use is made of the relatively expensive materials used and the herein taught flow principles for the products of combustion in relation to the fluid movement permits all the metal of the heat exchanging surfaces to be operated at maximum allowable safe temperatures whereby very efficient high temperature combustion may be employed and enormous heating capacities attained in apparatus of practical size. It should be obvious that the principles of my invention are applicable to apparatus of varying specific designs, and reference should accordingly be had to the appended claims in determining the scope of my invention.

I claim:

1. In a fluid heating furnace an elongated combustion chamber having end walls and a side wall, inlet and outlet headers extending along said side wall adjacent one of said end walls, a plurality of generally U-shaped fluidconducting tubes connected at their ends to said headers and extending longitudinally along said side wall toward the other end wall, a baille interposed between the longitudinally reaches of the respective tubes to direct products of combustion to flow longitudinally along the inner reaches of said tubes in one direction and thereafter longitudinally along the outer reaches of said tubes in the other direction, a burner port in one of said end walls to direct a llame stream longitudinally into said chamber, said inner reaches of said tubes being arranged in two closely spaced layers adjacent the inner surface of said baille with the reaches in one layer being staggered with respect to the reaches in the other layer and the diameters of the reaches being such that the inner surface of said baille is entirely hidden from said flame stream,

2. Apparatus according to claim 1 further characterized in that said chamber is cylindrical and in that said burner port is in the other of said end walls, and an annular exhaust port for the products of combustion in the side wall of said chamber adjacent said headers, the arrangement being such that the inner reaches of said tubes inwardly of said baffle is insulated from said flame stream by a longitudinally moving annular column of combustion gases positioned between said stream and said inner reaches.

3. Apparatus according to claim 2 further including bailles interposed in the space between the inner surface of the side wall of the combustion chamber and the outer surface of the first mentioned baille, said baffles being spirally arranged with respect to the longitudinal axis of said chamber whereby the products of combustion are caused to have a substantial component of wiping movement normal to the outer reaches of said tubes.

4. A fluid heating furnace comprising an upstanding frame supporting an upstanding open-topped cylindrical combustion chamber having a supporting ring at its upper end, a fuel burner disposed centrally in the bottom wall of said combustion chamber and positioned to emit an upwardly directed flame into said combustion chamber, an inverted cup-shaped housing having a lower annular surface adapted to be detachably supported on said ring, a pair of heat-conductive annular fluid headers mounted in the upper region of said housing, a plurality of downwardly looped fluid-conducting tubes connected at their ends to the respective headers, a cylindrical battle carried in depending relation by said housing and interposed between the inner and outer vertical reaches of said tubes, means disposed circumferentially of the upper end of said combustion chamber but below the top of said baille to withdraw the products of combustion from said chamber, and a baffle assembly arranged spiraliy about the outer surface of said cylindrical battle and encompassing the outer vertical reaches of said tubes to cause the products of combustion to liow spit-ally about the side wall of said chamber and normal to said outer reaches.

References Cited in the file of this patent UNITED STATES PATENTS 2,048,373 Carroll July 21, 1936 2,524,637 Ruegg Oct. 3, 1950 2,725,873 Walter Dec. 6, 1955 2,757,649 Coughlin Aug. 7, 1956 2,790,435 Johnson Apr. 30, 1957

Claims (1)

1. IN A FLUID HEATING FURNANCE AND ELONGATED COMBUSTION CHAMBER HAVING END WALLS AND A SIDE WALL, INLET AND OUTLET HEADERS EXTENDING ALONG SAID SIDE WALL ADJACENT ONE OF SAID END WALLS, A PLURALITY OF GENERALLY U-SHAPED FLUIDCONDUCTING TUBES CONNECTED AT THEIR ENDS TO SAID HEADERS AND EXTENDING LONGITUDINALLY ALONG SAID SIDE WALL TOWARD THE OTHER END WALL A BAFFLE INTERPOSED BETWEEN THE LONGITUDINALLY REACHES OF THE RESPECTIVE TUBES TO DIRECT PRODUCTS OF COMBUSTION TO FLOW LONGITUDINALLY ALONG THE INNER REACHES OF SAID TUBES IN ONE DIRECTION AND THEREAFTER LONGITUDINALLY ALONG THE OUTER REACHES OF SAID TUBES IN THE OTHER DIRECTION, A BURNER PORT IN ONE OF SAID END WALLS TO DIRECT A FLAME STREAM LONGITUDINALLY INTO SAID CHAMBER, SAID INNER REACHES OF SAID TUBES BEING ARRANGED IN TWO CLOSELY SPACED LAYERS ADJACENT THE INNER SURFACE OF SAID BAFFLE WITH THE REACHES IN ONE LAYER BEING STAGGERED WITH RESPECT TO THE REACHES IN THE OTHER LAYER AND THE DIAMETERS OF THE REACHES BEING SUCH THAT THE INNER SURFACE OF SAID BAFFLE IS ENTIRELY HIDDEN FROM SAID FLAME STREAM.

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