US2160928A - Split section heat exchanger - Google Patents

Description

w m n W@ n 9, i 3 m m w 765432 y .,wj a aofwfbswwjm 2, j J d jjjjjj 27 /g M2@ WM, 2 V Uv. .u` 0 A .b .r.` G 0/ m @MH Q G \J :EIL w o Q\\ E W w M m mi lj m w. M T v m im J `T F L June 6, 1939 Patented June 6, 1939 UNITED STATES 2,160,928 SPLIT SECTION HEAT EXCHANGER Vanderveer` Voorhees, Hammond; Ind., assignor to Standard Oil Company, Chicago, Ill., a-corporation of Indiana Appuation july 2s, 1937, serial No. 156,068

2 Claims.

This invention relates to heat exchangers of the type wherein two uid streams having different temperatures are passed in counter-current relationship to effect a heat transfer therebe- 5 tween, and more particularly to heat exchangers of this type which are composed of a plurality [l5 fractionator, for the purpose of effecting a heat exchange between this stream and the feed stock in order to utilize eiliciently the 4high temperature heat content o f this stream. It is 'well recognized that the loss of high temperature heat content, as for example at a temperature of 900 to 1000 F., which is not an unusually high exit temperature for the furnace exit stream, represents a very serious economic consideration. In other words, the loss of heat at 900 F. is a much more serious consideration than the loss of a similar amount, of heat at a considerably lower temperature. For this type of service itis almost essential that a heat exchanger of the billet or solid metal type be employed since this form of exchanger furnishes a most satisfactory means of conducting two streams of substantially the same cross section at substantially the same velocity in heat transfer relationship underrelatively highA pressures, the heat transfer medium in this case being the intervening metal between the heated-stream and `the stream being cooled. A further requirement of exchangers in this type of service is that they be so constructed that they may be readily and effectively cleaned of the carbon deposits which cannot be avoided in high temperaturek treatment of hydro-carbon oils. Thus it has been substantially impossible to transfer heat -from the outgoing voil of a cracking heater to the ingoing oil because of the deposition of a layer of carbon on the exchanger surfaces, which, because of its low heat conductivity, greatly interferes with heat transfer rates.

The present invention relates to the provision of a heat exchanger which is peculiarly adapted t0 the above service. The heat vexchange structures heretofore provided which come under the present particular classification have been subject to certain disadvantages to be pointed out, which disadvantages it is the object of my invention to overcome. For purposes of discussion these prior structures may be divided into two groups: first, the single solid metal billet or block type; and second, the built-up heavy metal section type. The patent to Keith 1,799,626 and the reissue patent to Wilson 19,701 disclose examples of the first type.v

Referring to the second grouping of this type of heat exchanger wherein it is proposed to build the exchanger by placing a plurality of heavy metallic members face-to-face, such for example as shown in the patent to Stancliffe 1,670,127, the following disadvantages are noted: first, the lack of provision for integral internally confined return bends for the traversing conduits; and second, the interposition of metallic interfaces between the heat transfer streams resulting in considerably lowering the eiiiciency of heat transfer as above pointed out. This latter disadvantage is present in the prior art wherever the sections of the conduits are contained Within the respective blocks whether the same be formed integral with the block itself or by pouring metal about the complete conduit sections. The exchangers formed according to the method employed in this group do solve the problem of handling a massive individual block of metal by building the structure in a plurality of sections. However, the further problems of effecting efficient heat transfer and providing for thorough cleaning are not satisfactorily solved. It is the object of this invention to solve all of these problemsfrnore effectively than has been done heretofore.` s

More specifically it is an object of the present invention to provide a heat exchanger of the type which Vis composed of a plurality of integral metal blocks, which exchanger is effective to accomplish heat exchange between two fluid streams of different temperatures, the heat transfer taking place principally through a solid metal transfer medium uninterrupted by any intervening interfaces except those between one metal and the two` vfluids. It isan object of the present invention to provide a heat exchanger ofthe-above type which is readily susceptible of being taken apart for shipment and handling and for exposing the passages thereinlfor the purpose of cleaning the same. It is another object of the .present invention to providea heat exchanger composed of solid integral metal blocks, which are cast by the use of simplepatterns without the necessity of employing complicated cores', and which can 'be cast veasily and cheaply. It is a still further ob- Y ject ofthe present invention to provide aheat `ex- 1 changer ofthe above ytype wherein a substantially true countercurrent flow is more completely efe 'the present invention to construct a heat exchanger of the above type wherein the heat eX- change passages therethrough are formed in a novel manner which materially decreases the amount of metal necessary in order to fabricate this structure and at the same time results in a substantially constant uninterrupted thickness of metal between the heat transfer passages. Another object is to provide a heat exchanger in which both the fluid being heated and the fluid being cooled pass through passages of substantially uniform cross-sectional area without dead y areas of low velocity where coke may deposit and interfere with heat exchange.

Further objects, advantages and uses of my invention will become apparent from a reading of the following detailed description and claims in connection with the appended drawing which form a part of this specification and wherein:

Figure 1 is an end elevation of my improved heat exchanger;

Figure 2 is a vertical cross section taken on line 2 2 of Figure 3;

Figure 3 is a plan view taken on line 3-3 of Figure 2.

Heat exchanger I 0 is shown as composed essentially of a plurality of integral metal blocks II to I'I, generally rectangular in vertical cross section placed face-to-face. Two substantially coextensive conduits X and Y of substantially constant cross-sectional area traverse a sinuous path back and forth between the respective adjacent faces of the blocks forming the exchanger IU, the respective ends of these conduits being provided with inlets and outlets for connection into two uid streamsl of different temperatures for effecting a heat transfer between these streams.

These conduits X and Y are provided in a novel manner. Outside or bottom block II is formed preferably by being cast of metal in one integral piece with a plurality of substantially parallel depressions IIa in the face thereof. These substantially parallel depressions IIa are joined in series by return bend depressions IIa. The sinuous trench-like path winding back and forth across the inner face of block II consti-` tutes one-half of a complete section of conduit Y. Adjacent block I2 is formed in a similar manner being distinguished from outside or bottom block II in having a pair of sinuous depressions formed in opposite faces thereof, these depressions being staggered. Sinuous depressions I2b and connecting return bend depressions I2b formed on the under side of block I2 match with the corresponding depressions IIa and IIa' in the face of block II, the whole defining a complete section of conduit Y entirely confined between the adjacent faces of blocks I I and I2 with no outside return bends. Special attention is directed to the fact that the return bends are each formed with an elliptical cross section. The long axis of the ellipse is positioned parallel to the face of the block 'and converges into a circular cross section in the straight parallel portions. This construction has the very significant advantage of enabling a closer disposition of conduits X and Y. This is necessary because the adjacent faces of blocks return bends cross over each other and thus control the spacing between conduits X and Y. By giving the return bends an elliptical cross section, conduits X and Y may be placed closer together along the parallel positions which are circular in cross section, thus requiring less metal for the whole structure.

'Ihe adjacent section of conduit X lying between adjacent faces of blocks I2 and I3 just above the section of conduit Y, just described, is formed in a like manner. Depressions I2a, I2a of block I2, together with cooperating complementary depressions' I3b and I3b of block I3 define this adjacent section of conduit X (see Figure 2).

Special attention is directed to the fact that with conduits X and Y constructed as described with one-half of each formed in opposite faces of the same integral block, heat exchange between fluids in these conduits takes place through the continuous uninterrupted intervening metal of the block.

This construction is repeated in the case of the faces of blocks I4, I5, I6 and I 'I, hence detailed description thereof will not be necessary further than to point out that sections of conduits X and Y alternate between successive faces. Cooperating passage I8 passes through blocks I2 and I3 to join the right-hand end of the section of conduit Y lying between the adjacent faces of blocks II and I2 with the corresponding rightvhand end of the section of conduit Y lying between the adjacent faces of blocks I3 and I4 (see Figure 2). Passage I9 (shown in dotted lines (Figure 2)) likewise connects the lefthand end of the section of conduit Y lying between adjacent faces of blocks I5 and I6. Pas'- sage 20 through blocks I6 and Il connects the right-hand end of the top section of conduit Y (likewise shown in dotted lines Figure 2) with connector 2I. The opposite end of conduit Y communicates with connector v 22 attached to the outside face of block II through a lateral passage 23 in block II.

The sections of conduit X describe a similar circuitous path between alternate pairs of adjacent faces. It will be seen that conduit X enters through the outside of block I1, is formed by depressions I1b, IIbi and I6a and I 6a passing back and forth in a circuitous path between I6 and I1, hence down through a passage f irrned in` blocks I5 and I6 to connect with the left-hand end of the section of conduit X lying between the adjacent faces of blocks I4 and I5. 'Ihis connecting passage, as well as the right-hand end of this section of conduit X and the section of conduit X lying between blocks I2 and I3, is not indicated on the drawing but its location will be apparent. These communicating connections are in the lower portion of the exchanger (looking at Figure 1) which portion is cut off by the section taken on line 2 2 but they correspond to passages I8 and I9 in the upper portion of the exchanger (see Figure 2). The other end of conduit Xis connected to outside connector 24 by a passageway formed through block II (see Figure 1).

While I have shown my exchanger with the blocks composing it lying in the horizontal planev it is to be understood that the structure is adapted to be positioned with the blocks resting on their edges in a manner like that of the leaves of a filter press. This latter arrangement is considered to have certain advantages with respect to'cleaning, since when so positioned the sections may be moved out one at a time and readily cleaned. Where .this latter method of positioning the exchanger is to be employed it will of course b'e necessary to provide a suitable platform or trackway on which to slide the parts successively.` This'trackway would take the place of the usual crane and in certain instances antifriction means may readily be employed between the bottom of the exchanger sections and its trackway to facilitate movement of the heavy parts. Although I contemplate the use of both methods, the positioning of the exchanger by placing one block upon-the other, a crane or similar device being relied upon to move the sections for the purpose of cleaning, will be used in most instances.

Each of the blocks Il to I1 are formed about their outer periphery with outwardly extending protuberances 25 having recesses formed therebetween for the introduction of a tool, such for example as a crowbar, for the purpose of assisting in separating the sections when it is desired to disassemble and clean passages X and Y between the faces of the exchanger. This structure is of particular importance where the exchanger is arranged to handle hydrocarbon fluids which have a, tendency to coke up the passages and thus add to the difficulty of separation of the blocks.

Cooperating openings 26 through the respective blocks \are provided` for the reception of bolts 21 and nuts 28 in sufficient number to 'maintainV the respective faces of the blocks in sealed engagement even under considerable pressures. It is to be noted that nuts 28 are provided on both ends of these bolts in order to facilitate the disassembly of the exchanger. v

The adjacent faces of the blocks are machined prior to assembly'as for example by means of a planing operation to give a suicient fit to effect a seal when the' nuts 28 are tightened. As soon as carbon begins to deposit in the crevices about the -passages of the conduits X and Y this seal becomes even more effective. `In `lower temperature operation an additional gasket may be provided by forming an auxiliary passage 30 around the heat exchanger adjacent its outer edge and between the respective faces. I propose to force under high pressure an antileak compound of asbestos, graphite and residual oil into the passage 30. i

The blocks composing my exchanger may be readily and economically formed by casting available metals such as iron, steel, aluminum, duriron, calite and other high chromium chemically and thermally resistant alloys, including stainless steel and alloys of these metals, the selection of a particular metal depending upon' temperature conditions to be encountered in the particular installation and 'the nature of the fluids involved in the heat exchange. The depressions formng the conduits can thus be cast into the faces of the blocks by sand-casting operations using-simple patterns, the only Acore lcasting necessary being that .required to form the transverse or connecting passages. Only two patterns are necessary'in order to form the depressions in the faces of the blocks in accordance with the present invention, the pattern for the end sections and one for each intermediate section. While I prefer to cast the blocks forming my exchanger, I also contemplate other well known methods such as drop-forging.

It will thus be seen that my improved construction possesses the following advantages: First, it may be cast of iron, steel or any suitable alloy with a minimum amount of machining and no welding, thus effecting a low initial cost. By virtue of forming the conduits in the faces of the metallic blocks increased eciency in heat transfer is effected, since'this transfer takes place through a continuous uninterrupted body of metal. The structure is easily and readily taken apart for the purpose of thorough and effective cleaning. No outside return bends are made necessary since the return bends of my structure are formed integrally in the respective faces of the blocks. The novel construction of the return bends in elliptical cross section results in a considerable saving in the amount of metal required and also in a more uniform thickness of metalbetween conduits X and Y. A generally countercurrent flow of the two streams in continuous uninterrupted heat exchange relationship is effected.

Since many different embodiments of my invention may be made without departing from the spirit thereof, I do not desire to limit myself to the foregoing description further Vthan is indicated by the following claims which should be construed as broadly as the prior art will permit.

I claim:

1. A heat exchanger composed of a plurality of integral metal blocks placed face-to-face in series relation and including a first outside block, a plurality of intermediate blocks, and a second outside block, a sinuous conduit confined between each adjacent pair of said faces, said respective conduits being formed by juxtaposed complementary depressions in said respective adjacent faces, said complementary depressions comprising a plurality of substantially' parallel circular sectionedconduits connected at their ends in series by return bends formed within the confines of said blocks, said return bends being e1- liptically shaped in cross section and connecting with said parallel circular sectioned conduits,

additional'passages through said blocks transverse of said faces and joining alternate ones of said sinuous conduits in series relation, whereby to define two continuous generally countercurrent paths for the flow of two fluids of different temperatures in heat exchange relation to each other, means connecting said paths with' two fluid streams having different temperatures for effecting a heat exchange therebetween, each of said intermediate integral blocks functioning as a continuous uninterrupted metal heat transferring medium between said streams.

2. The heat exchanger of claim 1 wherein the conduits in alternate faces are staggered with respect to each other.

VANDERVEER vooarnizris.`

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