US1829846A - Heat exchanger or desuperheater - Google Patents

Description

Nov. 3, 1931. w, H ARMACOST 1,829,846

vHEAT EXCHANGER OR DESUBRHEATER Flrd Jan. 2, 1950 /N VENTOR BY Q./Zm

ATTORNEY.

f changingthe liquid level inathe apparatus,

:.50 at the upper levels of the device as compared a Patented Nov. 1931 winiunn. ARMAoOsr, or

NnWiYyonx, AssGNoB. To THE surEnHEATERooM- PANY, onfNEW Yoan, N. Y.

HEAT Excnnnenn on -nnsurnnnna'rnn .Application nea January 2, 1930.v serial No. 418,086.

The present" invention relates to the art of heat exchange andaiins togprovideheat ex-y changers' which are economicaly to manufacture and'have a .high -capacityper unitzvol umelg Y fIn many installationsof'heat exchangers' and substantially all thoseused for desuper.

heating steam, it is preferred vto'einploy ex-f changers of the indirect type transferringqthe Y, 1,0 heat through the Walls of tubes or `the like.

In such installations,` it hasbeen foundV that the rate of heat transfer per unit area of surface is very great, .so that 'When liquid isused for absorbingthe' yheat .from the Iheating .'15 fluid, largel quantities-of vapor bubbles rise from the heat transferring surface in Contact With the lower portionof the liquid and often the quantity of vapor `thus developed is so large thatthe top surface of fthe liquid is in-y 20 suficient to permit the vapor -to disengage it self from the liquid vvithout causing foaming ,o1-carrying along liquid particles Withf'the vapor. AApsecond .diiiiculty which has been Y experienced in this typej of apparatus is vthat the 'bubbles rising from: the lower portion of Ythe heat transferring surface rise into Contact 'with the :upper portions of such surface and,

when the apparatus isvvorkinglat high` cal' pacity,.thereby insulate the upper portionl of heat transferring ysurface to suchv an extent thatiit becomes almost useless. A third diiiculty encountered in. the indirect tubular Atypefof heat exchanger has been to regulate itscapacity for heat transferring or desuperheating."ii"i Ordinarily this Vhas been done'by but, inthe. ordinary :type-o'f device, a small cha-nge. of liquid level hasresulted'insuch la large change in capacityv or the amount of desu'perheating that .the operatives have not 'been able practice toadjuSttlie vapparatns satisfactorily to meet changing conditions. f1 'It is the'obj ectof ,the-present invention'to Vprovide-a heatexchangerY adapted for use as a'superheatervand which will avoid the above ymentioned diicultiesj UIn accordance with my inventiornthe area Aof the liquid containing chamber taken vup by theA tubes for the heating fluid is decreased which vapor may disengage itself from the liquid is increased with increasing depth ofy the liquid. e. f j

'Novel features of my .apparatus are pointed out in theappended claims. My -inven.

tion, however, will best befunderstood from adetailed description of a specific heat jexchanger embodying the invention, and such a description will now be given in connection With the accompanying drawings in which j F ig, 1 is any elevational view partlyin ver-A tical section of a desuperheater in accordance with my invention.

Fig.;2 is a horizontal sectionon the line y 2-2of Fig, 1.

. yThe apparatus'illustrated inthe drawings is a known type ofdesuperheater in which heatingfluid suchV as steam-to be desuperheated is supplied to the inletY chamber 8 of the steamchest 9 through the pipe 10 and passes yfrom 8 into the outlet chamber 12 of thefsteam chest' through a tube bundle designated generally'by T 'and composed of inverted U-tubes. The tubes of bundle T extendupvvardlyand axially intoachamber 14 having a vertical axis and in which the transfer of heat occurs.` The chambers 8 and 12 are closed yat the top by a horizontal flue sheet 16m-Which the open`lower ends ofthe tubes ofbundleT are iixed and Vabove which the chamber141v containsl heat absorbing liquid, Water beingthe liquid employed when the apparatus is used for desuperheating steam. Vapor produced inthe upper chamber 14 may pass out through pipe 20 and, when saturated vsteam is produced in the, chamber, pipe 2O is ordinarily connected back into pipe'10 yso that *thetwo bodies of steam may be thoroughly mixed in passing through the' heat exchanger.

Thecapacity ofV such anapparatus is usually variedby varying the liquid levelin chamber 14 thereby varying the heat Ytransferring sur face in contact with the liquid.-

. l In accordance with the invention, the .top surface of the liquid is increased with increase of heat-transferring surface in oper-ation so as to; avoid the difficulty abovey mentioned. For this purpose, the tubes in chamber 14 are shown as larranged nvgroups 26,

.with .the lower levels yso that the surface at y 126e, 26?) and 260, the lengths of the tubes iny vertically spaced apart a materially greater l distance than the space between the leg portionsof the'tubes insuch groups;v nfThus'itY will be seen that the tubes in group 26 maintain a substantially even spacingthroughout 1` their entirelengths andthe same is true ofy the tubes in groups 26a, 266 and 26a-and also the distancebetween the legs of the Us of tubes in adjacent groups such as 26 and 26aV is substantially the-same as that between the legs of tubes in group 26 oruin group 26a, butthe vertical distance between theV bridge portionslof tubes in adjacent groups,'such as group 26 and group 26a, is muchgreater than f the horizontal "distance between the legs of :such tubesb Consequently, if the liquid level in chamber 22 israi'sed above the upperends of the -tubesof group 126, the free or top surface ofthe liquid available for disengaging i Y the'vapor'is increased and the vapor bubbles 4rising alongthe vertical lengths of the tubes may spread toward the free spacetlius vprovided inthe centery ofthe tube bundle to thereby lessen the concentration'fof vapor along the upper portions of the'vapor form-V ing surfaces. Again when'the liquid llevel passes the upper-end ofthe tubes inlgroup ,26a an additional free top surface and free central spaceis provided and this also occurs when the liquid level'is raised above the tubes ingroups 266 and 260=respectively. Indicati ing the-levels of thefupper ends of groups 26, 26a, 266 and 260 respectively `by horizontal lines B, C, D, and E and the bottom of chamber14 by line vA it'vhas'been found satisfactory 1n actual practice, to vmake the distancesAB,

' BC, CD andfDE respectively, proportional to 24, 3.2, 48 and 9 6. With this "specificarrangement ofheattransferring elements, the apparatus has one-quarter of its full capacity with 'the rliquid level at B, one-half its full capacity with the water level at C, threeqpaErters full capacity at D, and full capacity a ,y l i,

- The operation of an apparatus' in accordance with my invention will be' in general obvious from the foregoing description. j n Forconvenience of reference, however, it maybe-stated that'fas the heating fluid or steam to be desuperheated passes through tubes T, bubbles ofvaporf are formed which pass `up'along the vertical sections ofthe tubesbut as the 'stream of bubblesreaches the levels"B,lC,fD and E at whichthevverticalg'spacingbetween vthe ,tubes is increased,

'"f the bubbles `*tend to spread` toward the free the capacity of the central space thus provided, thereby avoiding largely the tendency to foam and to insulate the .upper heat transferringsurfaces of the tubes. Furthermore, by spacing the tubes as described, the capacity ofthe apparatus changes relatively.V slowly between the levels B and C, G and'D, and D andy E respectively, soy that the operator can adjust apparatus as desired without difficulty. Y 1

While two rows'or layers of tubes have been shown in each group such as 26, it will be obvious that the'se'parate groups may each comprise a greater 'or lesser number of layers'. It will be obvious also thatin order to increase the steam liberating surface in proportion to the' increase in capacity with thef depth of liquid,` the number of tubes in each group should be quite small and the groups quite close together. However, the relative number and spacing of the tubes andl groups as shown and described, has been found'satisfactory in practice.

:,zvAs the arrangement of tubes accordingfto myu invention involves using tubes having relatively largevariations in length, the resistance to steam :How through the longer tubes may be relatively mu'ch larger. than that through the shorter ones 'so that the steam flow in kthe groups of tubes is unequal. This may be avoided, if desired, by placing restrictions in the shorter tubes or by varying the 'sizes of the tubes inthe different groups vso that the longer tubes will have a greater internal diameter'. i While I have disclosed a specific apparatus acting Aas a desuperheater and havingfU=tubes lying in vertical planes, it will be understood that the form of apparatus herein disclosed is illustrative only and that my invention `may be applied tov other types ,of indirect heat exchangers su'ch', for instance, .as one having straight horizontal tubes. a

I' 1. A heat exchangerhavinga chamber for liquid, tubes for heating fluid passing through said chamber,y said chamber and tubes being so proportioned and arranged that the area of the top surface ofthe liquid increases with increase in depth of the liquid,

Y Y *l j D y a pressure chamber connected to one` end of safety valve 22 lis usually provided for` 'chamber14.= c

each of said tubes, and another pressure chamberconnected to the other end ofeach of said tubes. j

2. A heat exchanger as set forth inclaim Y 1 and in which thetubes are arranged in vertical planes. Y I

3. VA heat exchanger having a chamber for liquid having auvapo'rroutlet, inverted U- tubes for heating fluid passing through'said chamber, said tubes being arranged in groups and having the bridgeportions of' one group vertically above those of shorter groups and izo the bridge' portions ofthe tubes in adjacent y groupsspaced vertically a greaterzdistance than the distance between the leg portions. of

said adjacent groups to provide a space for the vapor to diverge from the tube surfaces and to separate from the'liquid surface, a pressure chamber connected to one end of each of said tubes, and another pressure chamber connected tov the'o'therA end olfeach of said v tubes.

I 4. AV heat exchanger having achamber and tubes therein for containing a heating Huid v and a liquid therein in Contactv with the outsides ofsaid'tubessaid chamber and tubes having an arrangement such that the portion of thephorizontal cross-section of the chamberroutside said tubes increases in passing'upward fromthe bottom of the chamber,

a pressure chamber connected -to one endiof j each 'of said tubes, and another pressure chamber connected tothe other end of each of saidv tubes.

5. A heat exchangerl comprising a chamber f Afor liquid, U-tubes With legs extending longitudinallv thereinl and for conducting a heating Huid therethrough, a liquid within said chamber in Contact with said tubes, said 'chamber and tubes having an rarrangement such vthat the portion of the horizontal crossf section of said chamber outside said tubesincreasesin passing upward from the bottomy y* oi the chamber', a pressure chamber connectedk to onerend of each ofsaid tubes, and anotherY pressure chamberconnectedto the other end ofl each of said tubes. p

WILBUR H."ARMACOST.

Images