US2364130A - Heat exchange apparatus - Google Patents

Description

Dec. 5, 1944.

G. E. CLANCY HEAT EXCHANGE VAPlsvaRmUs Filed March 2, 1942 l exhaustpipe. ,l

, The` general object of,` the (present Ainvention is Patented Dec.`5, `1944 N -UNITlEDY- STATE S PATENT om@ iHiiATxCHANGEArPARArri-isi" y l Gilbert E;` ClaneylLos Angeles, Calif., assignor to ffnfApplieation Marsh 2, ieiaserialln.'iaalesaff` iolaiin.; (Cim-241i This invention relates generallyytotheat exichangeapparatus,zand` more. particularly to; uid heaters and boilers Aidesignedx to utilizethe waste 'heat ":of exhaust gases lofi. anfaircraft or 'f other internalN combustion engine, though sarly :limited thereto. f l l being 1in aceordance (with thefbroken line l--gl of Aircraft :of modernwdesignlare commonly i 4equippedwith,cabin heating systems and `with water heaters, and" may "havefiuse `for steam as` a medium 'for' driving l `the turbines f of ngenerators andtthelikei Heat exe-hangers designed to derive theffheatforjsuoh typical f needs from the exhaustl 'gases of!! the engine have fbeen `incorporateddireotlyin the exhaust pipe. `The exhaust pipe of alarge aircraft may be, for `instance, abo-util"` in diameter, and the exhaust gases owing through thpipewillirange in tem'- perature betweenY 1200`jarid` 17009 "Under such conditions,` the heat exchanger may, if `properly designed, derive sullicientheat for all these needs `from the exhaust gases,`th0ugh prior leflortsu to "providelsuitable apparatus of the gclassinentioned fthe provision ofa heatfexchange ,arrangement yieldingl a sufeientl'y high rate of heat" transfer "between "the exhaust `gases and the ,.flld'tobe "heated and finally; the provision lof.; a. construction "which, does notV set [up objectionable turflo Fig. 3 `isa fragmentaryview showing agportron or vthe l metal plank tof f Vwhich the shell for the .boiler is` formed prior to;V `formation ofthe radial indentationsrand i l `Eig; 4` is a detailV similar to a` portion of Fig. ,2,` but showing a modification. v

" l` The briller` of the'lpreserit'invention; designated generally by numeral I0;;emb'odies a tubular shell as the exhaust pipeioan aircraft engine. Thus, i

or' sleeve fl l formed tyiiiicallyand` preferably of lligauge sheet'steelnadapted to be made` upzas a section` orlasnconduit; carrying hot gases, such as here typically illustrated, thesleeve. I'I isshown as `receivingWithints right:` lfiandfend,- the end lportionof `exh'alistfppe section` IZ, understood: to lead from the exhaustmmanifoldrof van aircraft` engine;` and as .received at its `left hand end within the end portionief"ei'zliaustpipe section: i 27 under- Stood to dischargeto atmosphere. n Sleeve Ill is i secured tothe exhaust pipe section" |2xeand lf2` in any 'suitable manner, las for nstanceixby means V'of screws `I4 passing through perforated lugs iso l of `the sleeve With-allfitemperaturechangs to` "lISand/Wisee" lg; l); i

"Illle'sleeve" Il is formed with a plurality of `lorigitu'dinal'ly extending lexpansionfjoints, permitting `ne cessa-ry `radial `expansion l and contraction 'Which the boiler', issubjected `3In the: present bulence inthe exhaustgases, nor inrany other way materially increase the` back `pressure in` the ,to provide a simple, ,ruggedgand relatively inexpensivegfwaste heat)heater4 for ,boiler `which overcomes Vallfofi the .abovelmentioned prob1ems. l 1- .With thislgenerallobjeotiinlview,I `now proceed Atoa detailed `descir'ilntion of one presentpreferredillustrative yeiiibodirrlent :of the invention,

.reference Abeing had to "theaccompanying draw:-

l is an` elevation, :With-.parts brokenzaway,

`of `a boiler in accordance iwiththe presentinvention indicatedTaal: made up iirraniexhagust 1 pipe `such lasthatvoi an-aireraftenginepthenbroken r laway portion at thefright-nand end er the view 1555 nreferredfembodiment'of the invention,` theseexparisien joints? are inf the 1form of a plurality oi annularly spaoed longitudinallyextending in- -dentatins v2 n; bent'inwardly substantially radially ifr'o'ii'i the-metal of the' sleeve, and extending subfstantiallyfrom vend to end :ofA the sleeve `in `direoi tions` parallel to its; central longitudinaltaxis.` i fis `best shown inY Fig; 2yeach such indentation is deiined .by @two longitudinally `extending wall por- `tionsfl `forming ,a'reentrant -angleof for instanceabut twoprlthreedegrees (the drawing showsfthe anglefsomewhat exaggerated), affordingtfsubstantial freedomefor radial and eircumferential contraction or; expansion. The inden- Vtations 20 may extendinwardly within' the sleeve typicallyuand preferablyv to adistanee substan- .1.' 50

tiallyhalf itsfradius; l `Indelfitations, `20,.iyterminate. `Just short of the connections"oi-tl'xegsleeveV Il with the exhaust .pipe; as `indicatedfat .20a (Fig.` l), and `the end fiplortions of the sleeve,joutwardly of the ends of Ithe indentations," are closed to-permit the effecting of a proper closure with the exhaust pipe. The manner of accomplishing this closure will be apparent from a consideration of Fig. 3, which is la detail showing a fragmentary end portion of the initially flat rectangular blank from which the sleeve will be understood to be formed. In Fig. 3, B designates the fragmentary portion of the blank,and letter C an edgewhich is eventually to become one end of the sleeve. Edge C is-forrned with a plurality of rectangular notches such'as abcd, one for each of the indentations (but one such notch appearing in Fig. 3), and it will of course be understood that the edge of the blank opposite to edge C will be formed with corresponding notches of the same kind'. The

.metal is severed for a short distance beyond points b and c, to form a straight edge ebcf. The

yits flat sides in contact with the sleeve, substanmetal is then bent inwardly along longitudinal gifcrease lines eg and fh, being at the same timer folded in the reverse direction at crease line i9' to form the apex of the indentation. 'I'hus the areas represented by egyi and fhai will forni the two walls 2| of the indentation. In this operation, edges ab and cd are butted against one another, and they are then welded together, as indicated at 24 in Fig. l. The openings then left at the ends of the wall members 2| (between the edges represented by ei and fi in Fig. 3)V are closed by welding, as indicated at 25 in Figs. l and 2.

In the particular embodiment of the invention here disclosed, the sleeve or shell is, as stated, formed from a rectangular blank, so that a longitudinal seam is necessarily provided. This. may

conveniently be located at the apex of ,one of the indentations 20, and the seam closed by welding, as indicated at 26 in Fig. 2.

Mounted on the sleeve is a. coil 30 compris.. ing a number of spaced turns of steel tubing 3|, preferably and here shown as ilattenedsomewhat, so as to increase the area of contact with the sleeve. This tubing is welded along each of its edges to the sleeve as indicated at 21, so as to reduce materially the resistance to flow of heat from the sleeve to the tubing. However, as will be evident from the drawing, the weld-integration of the tubing to the sleeve is discontinuous, being interrupted Wherever the tubing bridges across an Aindentation 20.

The end of the coil,at the downstream end of the sleeve |b| is connected to the supply of water or other liquidV to beheated or evaporated,

, and the other end of the coil is of course connected to whatever isto be supplied with the hot water, steam, etc.

The hydraulic radius of the sleeve is reduced, and the pick-up of heat from the exhaust gases correspondingly augmented, by the use of radially disposed longitudinally extending fins here illustratively shown as welded to the interior surface of the sleeve. These fins 35 are positioned in parallelism with the central longitudinal axis of the sleeve, so as to avoid setting up turbulence in the exhaust gases flowing through the sleeve, as wellasvthe creation of back pressure on .the engine, and they are preferably and herev shown as extending about two thirds of the distance from the wall of the sleeve to its center, the fins being here sh-own as uniformly spaced between the radial heat expansion indentations 20.

The boiler as thus described has many unique advantages. Considered first from the standpoint of heat transfer, the following features are to be noted. The radial fins 35, as well as the radial indentations 20, reach deeply into the eX- tially -increases the area. of contact between the sleeve and the coil, and hence further materially increases the rate of heat transfer. Moreover, the attening of the tubing reduces itshydraulic radius,v and hence increases the rate of heat transfer from the tubing to the water or other liquid contained therein, as will be evident to those skilled in the art.

The indentations 20 and the fins 35 both function as heat intercepting and conducting fins, be-

-ing designed to absorb a substantial quantity of heat from the gases and to `convey heat at a rapid rate to the sleeve gig. 4 shows a modiiication, in which the fins 35a are tapered in thickness, being thickest at their butt ends, that is, at point of juncture with the sleeve. Since all portions of the fins absorb heat from the hot gas, and since the heat intercepted by the-fins ows outwardly toward the sleeve, the quantity of heat carried` by the fins necessarily increases in the same direction, with some tendency to overheat theouter portions of the fins. The described thickening of the fins toward their butt ends accommodates this increased heat flow'.

The coil of the boiler as described cannot burn out even though operated dry. This follows from the fact that the heat radiation surface of the coil, arranged on the outside of the shell, is equal to or greater than the radiation surface of the sleeve, and so long as the sleeve itself does not burn out, it is impossible to convey sufcient heat from the sleeve to the coil to burn out the latter.

Neither the sleeve nor the coil is subject to fracture under the rather substantial expansive forces arising either from the extreme heat to which the apparatus is subjected, or from pos' sible freezing of water in the coil. The described expansive joints in the sleeve allow it to expand or to contract radially and circumferentially, or to twist somewhat about its 1ongitudinal axis to accommodate itself to any stresses placed upon it under any contemplated service conditions. as Weld-integrated to the sleeve, but with a necessary break in the weld line whenever the tubing bridges across an expansion joint. This results in a structure having, some capability for yielding torsionally about its central longitudinal axis with any torsional stress that may be set up owing to differential rates of expansion or contraction between the sleeve and the coil. The structure as described is capable of expanding, contracting, or working or giving in any required direction, with any stress placed upon it owing to high heat, rapid temperature changes, or freezing up, all possibility of fracture resulting from any temperature conditions which will be experienced under service conditions having been eliminated.

The flattening of the tubing of which the coil Vis composed safeguards against bursting of the coil upon freezing up. Thus, since the cross- The described weld-integration TheV coil has been described i pressure on the engine. i Certain of the advantageous features of strucv ducting surface. i

sectional area of `a round tube is greater `than `that of a flattened tube, if water left in the `coil should freeze, and therefore expand,V the eiect i will be merely to force the attened tubing to assume a more rounded shape, such change of shape being sufficient to provide the increased volume required.

The disposition of the indentations 2|!` and fins 35 in planes parallel to the sleeve is of im,-

possibility of fracture of the structure under any temperature condition which may be experienced in practical service, impossibility of burning out the coil, even if dry, and substantially complete avoidance ofincreasing theback ture and operation which have been described 2o I circumferentially spaced and longitudinally exi tending openindentations which project inward-` apply` to heat exchangers in general as Well as to boilers, and apply also Whether the high temperature fluid or the loW temperature fluid `oWs through the inner sleeve. For instance, the

provision of the expansion and contraction joints 20 takes care of the stresses which would i otherwise `be set up by differential expansions or metallically bonded with the first member, car-` ries a uid at another temperature. In any such circumstances the expansion joints 20 ac- 3()` contractions in such a structure Where one 1 member (the innerimember here) carries fluid at one temperature, and the other member (the outer `member here) in metallic contact orV commodate differential contractions and eXpansionsiand also materially increase the heat con- In the `specific illustrative form `which has the iiuid carrying members allows free expanbeen described the spiral tube form of one of sion and contraction `of that member with the longitudinal changes of dimension of the other member which is here shown as tubular; `While the expansion joints 2|] in the latter'zmember accommodate that member to `the lateral or i circumferential contractionsand expansions of f the first mentioned or spiralmember.

`It is of course to `be understood that the drawing, and description are `to be considered as merely illustrative of the invention in one of its possible practical forms, and; that various'` `changes in design, structure and arrangement may be made Without departing from the spirit and scope ofthe claim.

I claim:

In heat vexchange apparatus,l the combination of a fluid carrying member having `a heatconductive, fluidconning Wall ofgeneral tubular formation,A said Wall including' a :plurality of ly, from the inner surface of those portions of the wall which liebetween the indentations, into the interior of the tubular `member to form inter,- nalhollowheatconductive ns, said indentations being externally Open to the surrounding atmosphere` at their outer edges and forming fluid confining portions of the wall which also provide `for circumferential contraction and expansion; means connected with an end of the tubular lmember for feeding a fluid exclusively through the interior of said member, the interiors of the open indentations being `isolated from the fluid feed; and another fluid carrying member composed of a helically coiled tube with` longitudinally spaced turns closely surrounding the indented tubular Wall, :physically and heat-` conductively integrated with the `Wall betWeenI the circumferentially spaced indentations, and bridging their outer openings.

GILBERT E ciuirIc-Y.`

invention or of the appended

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