US2625917A - Fluid heating apparatus - Google Patents

Description

Jan. 20, 1953 w. BARNES FLUID HEATING APPARATUS Filed NOV. 16, 1950 FIG. 2

FIG.I

INVENTORI MARION W. BARNES C al.

ATTORNEYS;

Patented Jan. 20, 1953 FLUID HEATING APPARATUS Marion W. Barnes, Wilmette, IlL, assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware Application November 16, 1950, Serial No. 196,067

3 Claims.

This invention relates to an improved apparatus for heating fluids, and more particularly to an improved and more desirable construction and arrangement of fluid conduits within the small cylindrical type of up-draft heater.

In general, the cylindrical form of heater is used for small heat absorption operations, such as for example in the re-heating of fluid streams Within various stages of a fluid processing plant, or in small processing units such as catalytic polymerization plants eiiecting the conversion of hydrocarbon charge streams. The cylindrical form of heater has had tubes or fluid conduits disposed vertically adjacent the inside or the cylindrical wall forming the heating chamber, or in a helical or spiral form, with the spiral coils lying in a superimposed relationship. My present Patents Nos. 2,270,863 and 2,348,512 issued respectively January 27, 1942, and May 9, 1944, relate to a small type of cylindrical heater having radiant and convection heating sections. These patents also disclose the use of spirally formed flat coils within the convection heating sections. However, the plurality of flat spiral coils are expensive to construct, since the constantly changing radius of the spiral coil is difiicult to form in either field or shop fabrication.

It is, therefore, a principal object of the present invention to provide a plurality of layers of flat concentric pipe coils Within the upper convection heating section of the cylindrical type heater,

each coil or layer having a plurality of horizontally spaced concentric sections which are interconnected.

It is also an object of the present invention to provide a baffle within the upper portion of the heating chamber to form an annular shaped convection heating zone; which in turn is adapted to accommodate a plurality of layers of pipe coils having concentric interconnected sections.

It is of particular advantage to use sections of pipe which have a constant radius to in turn form a flat pipe coil, inasmuch as the constant radius sections may be readily formed in standard pipe bending apparatus, and special expensive shop fabrication may be eliminated. Also, concentric sections of pipe in any one layer may be readily interconnected in various ways to provide either series flow or parallel flow, whereas a spiral coil is limited to a single continuous series type of flow.

Briefly, the present invention provides a heater for fluid streams, comprising in combination, a vertically disposed substantially cylindrical refractory wall defining a heating chamber having a lower radiant heating zone and an upper convection heating zone, means for generating flame and hot combustion gases within a central portion of the lower radiant heating zone, a stack extending from the upper end of the cylindrical heating chamber, one or more fluid conduits dis posed adjacent the inside of the chamber wall within the lower radiant heating zone and out of the path of flow of the flames and hot combustion gases, and one or more convection heated fluid conduits within the upper convection heating zone which are disposed in the direct path of flow or hot combustion gases from the lower heating zone, the latter fluid conduit or conduits having a plurality of inter-connected horizontal or flat tubular coils, with each coil or layer thereof having a plurality of horizontally spaced concentrio sections which are less than 360 in length and connected one to another in a manner providing a desired fluid flow therethrough, and inlet and outlet means to each of the fluid conduits of the heating zones suitable for passing fluid mediums through said heating chamber.

Also, in accordance with a preferred embodiment of the present invention, a cylindrically shaped bafile is positioned within an upper portion of the heating chamber in a manner forming an annular shaped convection heating zone. Thus the layers of concentric sections of pipe forming th interconnected conduits within the convection heating zone, are subjected not only to the direct flow of hot combustion gases, but are disposed in a reduced cross-sectional area zone so that there is a higher velocity flow of the combustion gases through the annular zone, and an increasein the heat input to the fluid conduits. Heat absorption to a fluid stream is proportional to the mass velocity of the heating medium passing over the conduits, and increases with an increase in the mass velocity of therconvection heating combustion gas stream.

The improved construction and arrangement of the present apparatus for heating fluid streams will be more apparent upon reference to the accompanying drawing and the following description thereof, while additional advantageous features will be pointed out in connection with the description of the apparatus.

Figure 1 of the drawing is a sectional elevation view of the modified and improved circular heater.

Figure 2 of the drawing is a sectional plan view showing the interconnected concentric sections of tube in the convection heating zone of the chamber, as indicated by line 2-2 in Figure l of the drawing.

Figure 3 of the drawing is a sectional plan view as indicated by line 3-3 in Figure 1 of the drawmg.

Figure 4 of the drawing indicates in a plan View a plurality of concentric pipe sections interconnected to provide a parallel flow for separate fluid streams.

Referring now to the drawing, there is shown a cylindrical outer wall I a conically shaped roof 2, and a lowerfloor 3, all constructed of a suitable refractory material, such as fire-brick, or cast material having good refractory characteristics. A suitable metallic shell 4 is indicated as enclosing the roof and side refractory wall I, while a lower extension of the shell 5 provides means for elevating the furnace structure and anchoring it to a suitable foundation 6, with a space below the furnace floor 3 to accommodate one or more burners.

In the present embodiment, a centrally positioned burner 1 fires upwardly through a burner block 8 into the lower portion of the enclosed furnace chamber. The burner '1 is supplied with a suitable combustible gaseous fuel by way of line 9 and control valve ID, with air being supplied to the Venturi portion of the burner to provide a suitable combustible mixture. Supported on the furnace floor 3 above the burner block 8 is a checker work of refractory brick or blocks l l arranged to diffuse the flame from the burner and provide uniform distribution of radiant heat into the lower portion of the furnace structure. The upper end of the furnace chamber is provided with a suitable combustion gas outlet stack 12 and an adjustable damper l3. Thus, the flame and hot combustion gases generated within the lower portion of the furnace provides high temperature radiant heating therein while in the upper portion of the structure hot combustion gases may provide hot convection heating to suitably placed fluid conduits or tubes and then pass outwardly through the upper stack l2.

One or more fluid conduits may be placed adjacent the inside of refractory wall I in order to be subjected to high temperature radiant heating from the flame and hot combustion gases issuing from burner black 8 and the refractory grid H. The present embodiment shows a plurality of flat circular tube sections l4 positioned in superimposed relationship throughout substantially the entire lower and radiant heating portion of the furnace chamber. The adjacent sections It are connected one to another by means of suitable U bends or the like such as Is and I6, so that there is a continuous flow of the fluid stream through the heating chamber. As shown in Figures 1 and 3, the circular and concentric sections M are connected successively by the U bends 1-6 and I6 to provide a series fluid flow through the radiant heating zone of the chamber. In an alternative arrangement, not shown, a continuous helically shaped coil may be placed in the lower radiant heating section. However, in either arrangement, the lower fluid coil or conduit connects with the lower of the plurality of flat coils I 5 within the upper portion of the heating chamber, by means of the upper connection means 16'.

The upper end of the heating chamber has a cylindrical baffle I! which is suspended from the roof 2, or 'otherwise held in a suitable vertical position. This baflie has a lower conioally shaped end suitable to deflect the hot combustion gases into the annular convection zone I 9, which lies between the baffle I1 and the inside of wall I.

Fluid conduits or tubes within the convection heating zone are preferably spaced relatively close to one another, both vertically and horizontally, and the convection heating space itself is of preferably reduced cross-sectional area so that the hot combustion gases pass therethrough at a relatively high velocity. As noted hereinbefore, it is desirable to provide a relatively high mass velocity with respect to the tubular conduits in order to obtain a greater heat absorption by the fluid stream or streams. The present embodiment indicates four superimposed flat coils I 5 within the upper annular convection heating space I9, however, it is of course not intended to limit the improved concentric arrangement of tubes within the circular form of heater to any particular number of layers of superimposed coils.

As may be better shown in Figure 2 of the drawing, each of the flat coils I5 has a plurality of concentric tube sections which are less than 360 in length so that suitable U bends or the like may interconnect adjacent sections and form a continuous coil providing a continuous series flow through the entire flat coil. A suitable inlet or outlet 23 passes through the roof 2 and connects with one end of the outer concentric section 2i. Tube section 2! extends nearly 360 around the furnace chamber to a U bend 25 which connects it to the next inner concentric section 22 and the latter extends nearly 360 around to a second U bend or connecting piece 26. The bend 26 connects tube section 2 2 to the next inner section 23, and the latter extending around nearly 360 to a third U bend section which is suitable to connect it with an inner concentric section 24. The other end of inner section 25 connects by means of a vertically or angularly positioned U bend 28 with the inner concentric section of a next lower flat coil or layer of tubes P5. The sections of this next lower coil and all the other vertically superimposed coils are connected and spaced in a manner similar to that of Figure 2 of the drawing. Thus, a continuous series 'fiuid flow passes through interconnected concentric sections to an outer section of the next to the top coil and from the latter downwardly through a U bend 2s into a still lower layer or flat coil l5, with fluid flow continuing inwardly towards the central portion of the heater in this coil to an inner concentric section and to a U bend to which connects with the lower flat coil l 5. It may thus be seen, that fluid flow passes alternately inwardly and outwardly in the successive layers of superimposed flat coils of the tubular members.

Fluid flow through the series connected fluid conduits may be either downward or upward through the furnace chamber, with a fluid stream entering through thereof 2 and inlet 28] to become first heated in the upper annular convection zonelil andthe plurality of coils I5, to become subsequently subjected to high temperature radiant heating within the helical coil I ll prior to being discharged from the furnace chamber by way of outlet 3!. Alternatively, fluid flow may be upwardly through the furnace chamber, a fluid stream entering by way of line 3! and being subjected to high temperature heating in coil it prior to passing through the lower temperatu're convection heating zone It and passing outwardly by way of conduit 25).

It is a principal feature of the present improved tube arrangement to utilize concentrically formed and uniformly spaced tube sections within the heating zones more clearly shown in Figures 2 and 3 or the drawing, so that all portions of the coils may be more readily formed and fabricated for use in circular heaters. Concentric sections are not only more easily formed and fabricated but may be interconnected in different ways to provide more versatility in adapting a heater of this type to any desired processing operation. For example, while the embodiment, illustrated in Figures 1, 2 and 3, shows a continuous series flow through each of the superimposed conduits and coils, it may be noted that various modifications may readily be accomplished, with the concentric sections of the flat coil in any one layer accommodating parallel flow of separate fluid streams and the various concentric sections of each flat coil being interconnected by suitable U bends which provide the desired parallel flow either inwardly from the outer of the concentric sections, or alternatively outwardly from the inner concentric sections of a plurality of sections in each coil. Figure 4 of the drawing shows diagrammatically a parallel flow for separate fluid streams passing through the convection heating zone of the furnace, with the particular embodiment indicating six concentric sections of pipe interconnected by suitable U bends to provide the desired flow. It may be further noted that it is not intended to limit the tube arrangement to any set number of concentric sections, for a greater or lesser number of sections may be utilized in any particular heater, without being limited to the particular number shown in either Figure 2 or 4 of the present drawing.

I claim as my invention:

1. A heater for fluids, comprising in combination, a vertically disposed substantially cylindrical refractory wall defining a heating chamber having an upper convection heating zone, means for generating flame and hot combustion gases within the lower portion of said heating chamber, a stack extending from the upper end of said cylindrical heating chamber, a convection heated fluid conduit within said upper convection heating zone disposed in the direct path of flow of hot combustion gases from the lower portion of the chamber and having a plurality of interconnected horizontal layers of tube coils, with each layer thereof having a plurality of horizontally spaced concentric coil sections which are less than 360 in length and are connected one to the other providing a fluid flow therethrough within each layer, and inlet and outlet means connected to said fluid conduit.

2. A heater for fluids, comprising in combination, a vertically disposed substantially cylindrical refractory wall defining a heating chamber, means for generating flame and hot combustion gases within the lower portion of said heating chamber, a combustion gas outlet stack extending from the upper end of said heating chamber, a vertically positioned cylindrical bafile having a conically shaped lower end positioned within the upper end of said heating chamber and forming an annular shaped upper convection heating zone, a fluid conduit within said upper annular shaped convection heating zone disposed in the direct path of flow of hot combustion gases from the lower portion of the chamber to said outlet stack, said fluid conduit formed of a plurality of interconnected horizontal tubular coils, with each horizontal coil thereof having a plurality of horizontally spaced concentric tubular sections which are less than 360 in length and are connected successively one to another providing a series flow therethrough and inlet and outlet means connected to said fluid conduit.

3. The heater of claim 2 further characterized in that said plurality of interconnected horizontal coils have connecting means alternately between the inner and smaller diameter concentric coils of vertically adjacent coils and between the outer larger diameter concentric coils of vertically adjacent coils, whereby a series fluid flow through said fluid conduit within said upper convection heating zone passes alternately inwardly and outwardly therethrough.

MARION W. BARNES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 859,305 Lemp July 9, 1907 2,348,512 Barnes May 9, 1944

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