US3080915A

US3080915A - Heat exchanger

Info

Publication number: US3080915A
Application number: US809999A
Authority: US
Inventors: Thomas M Hamill
Original assignee: Individual
Current assignee: Individual
Priority date: 1959-04-30
Filing date: 1959-04-30
Publication date: 1963-03-12
Anticipated expiration: 1980-03-12

Description

March 12, 1963 T. M. HAMlLL. 3,080,915

HEAT EXCHANGER Filed April 30, 1959 I 5 Sheets-Sheet l Vhis Attorney March 12, 1963 T. M. HAMILL HEAT EXCHANGER ied' AprilAso, 1959 5 Sheets-Sheet 2 Thomas M. Hamill his Attorney March 12,1963 T. M. HAMILL HEAT EXCHANGER 5 Sheets-Shea?l 3 Filed April 30, 1959 l w .d t m m @di w a v J m H. um Nn nm/ M 7 Amm L O u r h I m LALT.

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Inventor:

v Thomas M, Hamill his Attorney March'lZ, 1963 T. M. HAMILL HEAT EXCHANGER 5 Sheets-Sheet 5 Filed April-' 1.59 1959 .Y 4 .J DI ...L /l

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` Inventor: Thomas M. Hamill his Attorney United States Patent` 3,680,915 HEAT EXCHANGER Thomas M. Hamill, 11 St. Claire Ave., Oid Greenwich, Conn. Fiied Apr. 30, 1959, Ser. No. 809,999 2 Claims. (Cl. 165 72) This inventionrelates to heat exchangers and this application is a continuation-in-part of my copending application Serial No. 464,104, tiled October22, 1954, and now abandoned.

The primary object of the invention is to provide animproved vapor to liquid heat exchanger of plural pass design on theliquid side wherein flow of liquid from one to a succeeding tube bank is reversed by a compartment connecting and discrete to those tube banks and having a return wall of such construction and arrangement as to minimize the pressure drop incident to the ow reversal.

Another object of the invention is to provide a vapor to liquid heat exchanger having a compartment of the character described for reversing the flow of liquid between a pair of tube banks wherein the return wall of each cornpartrnent is built into and removable with one of the end doors for ready access to the tubes of the connected banks and instead of being at over its portion confronting the tube ends, is substantially cylindrically concave in its entirety, with consequent marked decrease in the pressure cir-op attendant the reversal of iiow.

, A further object of the invention is to provide a vapor to liquid heat exchanger having for each adjoining pair of tube banks betweenwhich flow of liquid is to be reversed, a cylindrically concave return wall built into an adjoining end door -of the heat exchanger and forming with the confronting tube sheet a substantially semi-cylindrical, flow-reversing chamber embracing and discrete to the contiguous ends of the tubes of the pairof banks.

An additional object of the invention is to provide a vapor to liquid heat exchanger of the tube type and of plural liquid pass design, wherein an expansion joint connected to a header serves as a draw-off for both condensed and uncondensed vapor.

Another object of the invention is to provide an irnproved vapor to liquid heat exchanger which is compact, of high efficiency and adapted for single or plural unit installation.

Other objects and advantages of the invention will -appear hereinafter in the detailed description, be particularly pointed out in the appended claims and be illustrated in the accompanying drawings, in which:

FIGURE l is a side elevational View of a preferred embodiment of the heat exchanger of the present invention;

FIGURE 2 is a plan view of the heat exchanger of FIG- URE l;

FIGUREv 3 is a vertical sectional view taken along theV lines 3 3 of FIGURE l;

FIGURES 4 and 5 together are a vertical section on an enlarged scale, taken along the lines 4 4 of FIGURE 2;

FIGURE 6 is an end elevational view7 partly in vertical section, taken along the lines 6 6 of FIGURE 4;

FIGURE 7 is a vertical sectional view taken along the lines 7 7 of FIGURE 4;

FIGURE 8 is a vertical sectional view taken along the lines 8 8 of FIGURE 5;

FIGURE 9 is a vertical sectional view taken along thev lines 9 9 of FIGURE 5; and

FIGURE l0 is a fragmentary horizontal sectional view on an enlarged scale, taken along the lines 10-10 of FIGURE l.

Referring now in detail to the drawings, in which like reference characters designate like parts,'the heat ex- Sl Patented Mar. 12, i963 ICC changer of the present invention is a vapor to liquid heat exchanger in which heat is transferred between gaseous and liquid media, the gaseous medium herein being termed vapor and usually being a gas, such as steam, which is in the liquid phase at room temperature. While of especial value in the form disclosed in heating pineapple juice during processing of the latter, it will be recognizedthat the heat exchanger of the present invention has wide application in the transfer of heat between vapors and liquids.

The illustrated heat exchanger is comprised of a piurality of tube banks 1, contained in or enclosed by a shell or jacket 2, of rectangular cross-section, the shell 2 being banded laterally at spaced points throughout its length to withstand the vapor pressuresto which it is subjected by suitable means, such as the illustrated interlocked channelirons 3. The several tube banks 1 are arranged side by side or in superimposed relation and each is comprised of one or a plurality, and preferably the same number, of liquid-conducting tubes 4, the several tubes desirably being of the same diameter and having parallel axes and those within each bank being equally spaced, so that for each tube of each bank there is in each of the adjoining banks a corresponding or counterpart tube with which it is aligned in a direction normal to the banks. The several tubes 4 are anchored at their opposite ends in headers or tube sheets 5, one of which is fixed to the shell 2 and the other of which is connected to the shell by an expansion joint 6 formed of an expansion plate 7 encircling and disposed substantially normal to the longitudinal axis of the shell and a frusto-pyramidal'hood or cover S rigidly connected to the expansion plate 7 and the adjoining tube sheet and tapering or inclined inwardly beyond the expansion plate so as to join the associated tube sheet within the lateral confines of the shell. The opposite ends of the heat exchanger are enclosed by end doors 9, each of which, when in service, is sealed fluid-tight to the adjoining of the tube sheets 5, as by bolts 1t), the end doors also preferably being hinged to the associated of the tube sheets to facilitate their opening and access to the tubes 4 for cleaning or other purposes.

A principal feature of the invention is the interior construction of the end doors 9 by which each, with the connected tube sheet 5, is made to provide one or, more generally, a plurality of compartments 11 for reversing the flow of fluid between a pair of adjoining tube banks. While the concept in general is old in heat exchangers of the tube type of employing compartments formed by partitioning end doors in lieu of individual reverse bends for reversing llow between a plurality or multiplicity of tube banks, its applications have been on a rather hit or miss basis, with the primary objective ready access to the tubes and this attained at an inordinate expense to operating eiiciency because of the greatly increased pressure drop between the tube banks. The -hit or miss nature of such applications is demonstrated by all prior heat exchangers of this type, none of which is uniform in its flow-reversing chambers and most of which use their chambers indiscriminately, some to connect two and others a multiplicity of tube banks. Nor is there any indication in such prior art that the return Walls of such chambers should be of any particular shape, even though the function of each is essentially the same. Thus, in the compartments of a single heat exchanger, the return walls of some compartments will be arcuately concave, while those of others will be substantially flat.

Bringing -order out lorf chaos, it has now been found that the advantage of now-reversing compartments in ready access to the tubes can be retained with a rninimumi loss Aof Vpressune attendant the flow reversal if two conditions are fultilled, one, that-each compartment be open only to a pair of adjoining tube banks, and the other, that each compartment be substantially semi-cylindrical with its return wall substantially cylindrically concave and the ratio of its width to its `depth about 2:1. Taking as the `best that the prior art had to offer, a heat exchanger fulfilling the tirst of these conditions but not the second, each compartment having a return wall presenting a at surface to the ends `of the connected tube banks, comparative tests, even at low operating velocities of about 41/2 feet per second, have shown that a heat exchanger equipped with compartments meeting both conditions will have at least 10% better heat transfer for .the same initial head, due to the lesser pressure drop, and the expectancy curves are such as to indicate a further increase 4in this eiciency to as much as l5-20% with more normal operating velocities of 7-8 feet per second.

In fulfilling the lforegoing conditions as to its flow-reversing compartments, the heat exchanger of this invention has each of its end doors 9 divided on its inner face into a plurality of recesses or concavities 11b by `dividing members, ribs or partitions 12 which, with the recesses, extend transversely `or laterally of the door, parallel to the tube banks 1 `and normal to the axes of the tubes 4, the ribs joining or merging with and the recesses being closed at their ends by the side or lateral walls 13 of the door. Embracing or straddling an adjoining pair of tube banks and sealed, separated or made discrete from each adjoining compartment by engagement of one of the ribs 12 with the end gasket 14 interposed between each end do-or 9 and the associated tube sheet 5, each of the recesses 11b forms with the included portion of the associated tube sheet one of the dow-reversing compartments 11 for receiving fluid trom one bank of tubes and passing it on to the next bank. In the preferred construction, in which the tube banks 1 are uniformly spaced and have the same number of tubes 4 and the end doors 9 are rectangular, the plurality of compartments 11 are uniform or identical in their dimensions as well as in their shape. In any case, the compartmenting of the end doors is relatively staggered, so that the banks of the pair open to a compartment in one end door are open to different compartments in the other end door, the compartments of the two doors thus causing the liquid to flow in turn through each succeeding bank and reverse its direction of iiow between banks.

Conveniently cast integrally with the end doors 9, if the latter are made of cast iron or like matetrial, the tube end-confronting, return or iioW-reversing walls 16 of the compartments f11 are substantially cylindrically concave, not only over the area each presents to the ends of the pair of tube banks 1 which its compartment 11 connects, but in their entirety. Each of the compartments 11, in fulfillment of the second of the two conditions, being substantially semi-cylindrical with the ratio of its width to its depth on the order of 2:1 and its shape or con figuration, when, as here, the tube sheets are flat, being determined by the shape of its return wall 16, the latter in turn is substantially semi-cylindrical and has the same ratio between its width and depth. To maintain its discreteness to the pair of adjoining tube banks which its compartment connects as well las further to minimize resistance to reversal of iiow, each of the return walls 16 is made to embrace the contiguous ends of the connected pair of banks and sealingly engage the adjoining tube sheet thereabout and at lthe same time is restricted in its width substantially to the corresponding outside dimension or span of the connected banks. The compartments 11 of Athe present heat exchanger are each substantially semi-cylindrical and discrete or open only to the tubes 4 of the pair of tube Ybanks 1 which it connects. Quite evidently by minimizing turbulence and consequent resistance to fluid ow during pass reversal, the described compartments impart to the heat exchanger of this invention an operating etiiciency markedly better than prior exchangers having how-reversing walls built into` their end doors and comparable with that of individual reverse bends, While retaining the advantage inherent in inabuilding the return walls of ready accessibility to the tubes.

For leading the fluid, whose temperature is to be increased or otherwise varied, to and from the heat exchanger, the end compartment 11a in one of the end doors 9, i.e., the door at the left of the heat exchanger as viewed in the ligues, lare connected, respectively, to inlet and outlet manifolds 17 and 18. Of the two manifolds, the inlet manifold 17 will normally be connected to a suitable pump (not shown) for driving the fluid through the heat exchanger, and the outlet manifold 18 to discharge piping (not shown), or either or both of the manifolds may be connected to another heat exchanger, depending on whether the heat exchanger is to be used alone or grouped with others. If desired to check the efiiciency of the Iheat exchanger periodically, thermometers (not shown) may be mounted in the end compartments 11a of one or both end doors, through suitable, normally plugged, openings 19.

Of multiple pass design on the vliquid side in the manner above described, the heat exchanger also preferably is multi-pass on the vapor side and the vapor also preferably iiows counter to the flow of the liquid, ie., the liquid and vapor enter the heat exchanger Afrom opposite sides and exist correspondingly. For the latter purpose the steam or other vapor is introduced into the tube sheets S through an inlet or feed pipe 20 positioned on the liquid-discharge side of the heat exchanger. Within the shell the vapor is directed through a plurality of passes by one or more, here two, baffles 21 extending lengthwise of the shell 2 and each interposed between adjoining of tube banks 1, the baffles dividing the interior of the shell into a plurality of longitudinally extending vapor-pass passes 22. Each of .these longitudinal baffles 21 terminates at one end 23 short of one of the tube sheets, the spaced end being staggered relative to that of thte preceding baflie, so that the vapor at the end of each pass will reverse its flow and proceed in the opposite direction through the passage of the succeeding pass.

In the conventional vapor to liquid heat exchanger the batiie or baies for reversing iiow of the vapor normally tre spaced equi-distantly so that the passages for the several passes are of the same cross-section. This has the disadvantage of a progressive decrease in the velocity of the Vapor due to the pressure drop, with corresponding decrease in -heat transfer toward the vapor discharge end of the heat exchanger. To counteract this pressure drop, the longitudinal baffles 21 o-f the instant heat exchanger are so spaced relative to each other and to the shell 2 that the cross-sectional area of the passage 22 for each of the passes is less than that for the preceding pass, the progressively decreasing cross-sectional area counteracting the pressure drop and maintaining the vapor velocity `and heat transfer high throughout the several passes. v

A second factor responsible for reduced efiiciency in the conventional heat exchanger is that vapor condensing in one pass tends to deposit 4as droplets on the tubes contained in a succeeding pass, with consequent partial blanketing and decrease in the heat transfer coefiicient of the latter. This tendency is here overcome by sloping each of the longitudinal baiiies 21 laterally or transversely, so as to provide a transverse gradient for causing any vapor condensate to flow towards a longitudinal side or side wall 24 of the shell 2. Once at the side wall 24, the condensate is enabled .to flow down it to the bottom or bottom wall 25 of the shell through a plurality of longitudinally spaced slots 26 between the side edges of the baies 21 and the shell, thus effectively shielding the tubes of the next pass from this condensate. The desired slotting at the sides of the baffles may conveniently be produced by the use of baffles of less Iwidth than the shell which, for support, are spot-welded `at intervals to the side Walls 24.

Were the vapor ilo-W directed by the longitudinal bales 21, alone, the desired high vapor velocity throughout the shell would be obtained, but without assurance 0f full contact between the vapor and Iall of the tubes. Such :full contact and correspondingly high heat transfer efciency, is here obtained by transverse bailes 27 each connected at three edges to the shell 2, las b-y spot-welding, and having an irregular fourth edge 28 spaced from the confronting of the side walls 24 -of 'the shell. The spaced irregular edges 28 of the transverse bales 27, like the spaced ends 23 of .the longitudinal bales, are relatively staggered, so that the vapor will be directed by each transverse baffle towards an opposite side of the shell and :thus have the desired motion cross-wise as well as longitudinally of the shell in each pass. The high velocity attendant the progressive decrease in cross-sectional area of the several vapor passes, coupled with the cross-flow derived from the transverse battles 27, effectively eliminates the rforrnlation of stratified pockets of vapor within the shell. In addition to their production of cross-flow, the transverse bafes 27 may also be employed as intermediate tube supports, eac-h of the illustrated two bales, `for this purpose, receiving and supporting a different bali bf the tubes.

As the vapor completes the last of its passes over the tubes 4 it is ydirected into 'a chamber 29 within .the expansion joint A6, which encircles the shell and is deiined by the confronting walls of the shell 2, the expansion plate 7 and the hood 8. 'In the chamber 29 and projecting at one end into the sump 30 fforming its lower portion is a conduit for exhausting uncondensed vapor from the lheat exchanger, the conduit here being in the Vfor-m of a pair of pipes 31 which extend upwardly in the chamber alongside the shell and project at their upper ends through the hood 8. At the same time any condensate entrained in the vapor or flowing oil .the bottom wall 25 -ot the shell 2, drops into the sump 30 and is discharged therefrom through a discharge lopening 32. Either the natural hydraulic gradient or, and preferably, mounting of the heat exchanger so that the bottom wall 25 of its shell 2 slopes toward .the sump 30, may be relied upon yfor causing condensate ou the bottom wall to ilo-w therefrom into the sump.

From the above detailed description, it will be apparent that there has been provided an improved vapor to liquid heat exchanger iwhich, while possessing yother important features, improves over prior exchangers mainly by use of lflow-reversing compartments which have their return walls in the end doors for ready access to the .tubes and by their particular construction yand arrangement attain this objective without the sacrifice in operating efficiency heretofore considered essential. It should be understood that the `described land disclosed embodiment is merely exemplary of the invention and that `all moditications are intended to `be included which do not depart vfrom either the spirit of the invention or the `scope of the lappended claims.

Having described my invention, l claim:

1. A vapor to liquid heat exchanger comprising a shell substantially rectangular in cross-section, spaced tube sheets in said shell adjacent ends thereof and closing ends of a vapor compartment therein, a plurality of tubes of equal diameter in said shell and extending 'through said tube sheets, said tubes being arranged in a plurality of substantially parallel tube banks ,for passing liquid through said shell between a liquid inlet and a liquid Ioutlet therein, said banks each including the same number of tube-s each aligned in a direction normal to said banks with a tube of each adjoining bank, end doors disposed outwardly of said tube sheets and closing ends of said shell `and confronting opposite ends of said banks, and relatively staggered compartments at opposite ends of said tube banks each for connecting an end of a bank to an adjoining end ont a succeeding bank for reversing iiow of liquid therebetween, each compartment including a concave semi-cylindrical return -wall in one Aof the end -doors and embracing and substantially equal in width to .the outside span of contiguous ends of the pair of tube banks connected thereby, and said return wall sealingly engaging .the adjoining tube sheet about said ends of said connected pair lfor limiting access thereto to its compartment.

2. A vapor to liquid heat exchanger comprising a shell substantially rectangular in cross-section, `spaced tube sheets in said shell adjacent ends thereof and closing ends of -a vapor compartment therein, a plurality of tubes of equal diameter in said shell and extending through said tube sheets, said tubes being arranged in a plurality of substantially parallel -tube banks for passing liquid through said shell between a liquid inlet and la liquid -outlet therein, said banks each including the same number of tubes each aligned in a `direction normal to said banks with a ltube of each adjoining bank, end doors disposed outwardly of said tube sheets and closing ends of said -shell and confronting opposite -ends of said banks, and relatively staggered compartments at opposite ends of said tube banks each for connecting an end of a bank to an `adjoining end of a succeeding bank for reversing ilow oi liquid therebetween, each compartment including a concave semi-cylindrical return wall in and extending transversely of one of :the end doors and embracing contiguous ends of the pair of tube banks connected thereby, fandsaid return Wall sealingly enga-ging the -adjoining tube sheet about said ends of said connect/ed pair f-or llimiting yaccess .thereto to its compartment.

References Cited in the le of this patent UNITED STATES PATENTS 652,296 Sims June 26, 1900 919,208 Patitz Apr. 20, v1909 982,405 :Wiki Ian. 24, 1911 1,558,573 Bancel Oct. 27, 1925 1,678,027 Wagner July 24, 1928 1,700,498l Hughes Ian. 29, 1929 1,792,060 Bancel Feb. 10, `1931 1,884,210 Potter Oct. 25, 1932 1,947,098 ODcnnell Fe-b. 13, 1934 1,979,975 Maniscalco Nov. 6, 1934 y2,344,269 Saco Mar. 14, 1944 2,413,360 Maguire et al. Dec. 31, 1946 2,530,443 Walker Nov. 2l, 1950 FOREIGN PATENTS 1,001,826 IFrance Oct. 23, 1951

Claims

2. A VAPOR TO LIQUID HEAT EXCHANGER COMPRISING A SHELL SUBSTANTIALLY RECTANGULAR IN CROSS-SECTION, SPACED TUBE SHEETS IN SAID SHELL ADJACENT ENDS THEREOF AND CLOSING ENDS OF A VAPOR COMPARTMENT THEREIN, A PLURALITY OF TUBES OF EQUAL DIAMETER IN SAID SHELL AND EXTENDING THROUGH SAID TUBE SHEETS, SAID TUBES BEING ARRANGED IN A PLURALITY OF SUBSTANTIALLY PARALLEL TUBE BANKS FOR PASSING LIQUID THROUGH SAID SHELL BETWEEN A LIQUID INLET AND A LIQUID OUTLET THEREIN, SAID BANKS EACH INCLUDING THE SAME NUMBER OF TUBES EACH ALIGNED IN A DIRECTION NORMAL TO SAID BANKS WITH A TUBE OF EACH ADJOINING BANK, END DOORS DISPOSED OUTWARDLY OF SAID TUBE SHEETS AND CLOSING ENDS OF SAID SHELL AND CONFRONTING OPPOSITE ENDS OF SAID BANKS, AND RELATIVELY STAGGERED COMPARTMENTS AT OPPOSITE ENDS OF SAID TUBE BANKS EACH FOR CONNECTING AN END OF A BANK TO AN ADJOINING END OF A SUCCEEDING BANK FOR REVERSING FLOW OF LIQUID THEREBETWEEN, EACH COMPARTMENT INCLUDING A CONCAVE SEMI-CYLINDRICAL RETURN WALL IN AND EXTENDING TRANSVERSELY OF ONE OF THE END DOORS AND EMBRACING CONTIGUOUS ENDS OF THE PAIR OF TUBE BANKS CONNECTED THEREBY, AND SAID RETURN WALL SEALINGLY ENGAGING THE ADJOINING TUBE SHEET ABOUT SAID ENDS OF SAID CONNECTED PAIR FOR LIMITING ACCESS THERETO TO ITS COMPARTMENT.