US2363526A

US2363526A - Heat exchanger

Info

Publication number: US2363526A
Application number: US348839A
Authority: US
Inventors: James C Hobbs
Original assignee: Individual
Current assignee: Individual
Priority date: 1940-07-31
Filing date: 1940-07-31
Publication date: 1944-11-28
Anticipated expiration: 1961-11-28

Description

Nov. 28, 1944. J. H5558 2,363,526

HEAT ExcHANER Filed July 31, 1940 Y 4 Sheets-Sheet 2 Fig.3

INVENT OR.

25 Ja 95C pbbs v ATTORNEY.

Nov. 28, 1944. J. c. HOBBS HEAT EXCHANGER Filed July 31, 1940 4 SheetS -Sheet 4:

Y INVENTOR. James C Hobbs ATTORNEY.

. Fig. 1;

' section;

Patented Nov. 28, 1944 OFFICE 2,363,526 nsn'r EXCHANGER James C. Hobbs, Palnesvllle, Ohio Application July :1, .1940, Serial No. 348,839

6 Claims.

The invention herein disclosed relates to heat exchangers of a type wherein heat is transferred from one fluid medium to another within an enclosing pressure vessel. In some forms of heat 1 exchangers one fluid may. be brought into direct contact with another, whereas in others of the type specifically described herein, one fluid may be confined within tubes disposed within thevessel and another admitted to the vessel into intimate contact with such tubes, whereby the tube walls constitute intermediary heat exchange surface between the fluids.

The invention has for an object the provision of a heat exchanger wherein the transfer of heat from one fluid to another is accomplished with high efliciency and maximum utilization of the fluid having the higher temperature.

An additional object is in the effective utilization of intermediary heat transfer surface'as in the case for example where one of the fluids is carried within tubes.

Further objects include improvements in th formation of fluid-tight joints between associat- -ed parts of the structure, and in the utilization of the pressure fluid in maintaining such joints in a fluid-tight condition.

These and other objects and advantages of the invention will be apparent from the ensuing description and from the accompanying drawings, in which: I

Fig. 1 is an elevational view in section illustrating an embodiment of the invention;

Fig. 2 is an enlarged fragment of Fig. 1;

Fig. 3 is a plan of the Fig. 1 embodiment;

Fig. 4 is a plan section along line H of Fig. 5 illustrates a detail;

Fig. 6 illustrates the element of Fig. 5 as assembled;

Fig. 7 is a sectional elevation of a modification;

Fig. 8 is a side elevation of Fig. 7 partly in Figs. 9 and 10 are'plan views of Fig.7, Fig. 9 being enlarged and partly in section along line 9-4.

The heat exchanger illustrated in Fig. 1 includes an elongated pressure vessel I, wherein a generally cylindrical shell 2 is provided at opposite ends with pressure heads 3 and l welded thereto. The shell 2 is preferably formed of a plurality of telescoping sections 5, 6, I, 8 of different diameters with adjacent sections remov- 257-224) heat-exchange fluids. Fluid-tight connections l2 and I3 are made to

heads

3, 4 to provide the desired inlet and outlet connections for the fluid which is conducted through the bundle of tubes ll. This form of heat exchanger is particularly adapted for use inan upright position,.that is, with the longitudinal axis of the shell extending vertically, in which case a liquid such as boiler feed water under pressure may becaused to flow upwardly through the tubes II, the lower connection l2 constituting an inlet connection for 7 the water and the upper connection IS an outlet connection. A condenslble heating medium such as superheated steam may be admitted to the shell through one or more connections l4, I5 adjacent the upper end of the tube bundle, and directed into intimate contact with the tubes through which the cooler fluid is conducted.

An arcuate baflle I6 is spaced inwardly of the shell 2 opposite each of the vapor connections ll, ii to prevent impingement 'of the entering stream of high temperature vapor against the tubes H, the battle preferably being removably supported within the shell by having its upper edge received in a recess H in head 4, and its lower edge welded to an arcuate bar I8 removably secured to the shell as by a plurality of connectors, such as cap screw Ill. The stream of vapor is thus diverted circumferentially around the lateral edges of the baflle l6 and enters the tube compartment at decreased velocitythrough the openings 20 adjacent the interior wall surface of their lengths by means of plates 2| which also serve as baflles for directing the flow of heating fluid over and along the tubes in a substantially sinuous path generally counter to the upward flow of the liquid within the tubes. Each supporting plate or baflle 2| as detailed in Figs. 5 and 6 extends inwardly acrossv the tube bundle from an outer position including the outermost row of tubes 22 to an inner position including the central row of tubes 23, each plate being of-seg- .mental formation and having clearanceholes 24 of the same arrangement and spacing as tubes I I. The plate is pivotally supported at 25 by projectionsof weld metal for example on tubes of the central row 23 and, due to the clearances provided around the tubes ll, each plate may be assembled in an inclined position across the tube bundle with the lower outer edge adjacent the inner wall of the shell. In the inclined position, the

plates are wedged between successive rows of tubes and thereby provide a substantial support for the tubes II to maintain the tubes in spaced relation and to prevent vibration. The use of circular tube holes 24 in combination with tubes H of smaller circular cross section provides spaces at opposite slds of each tube which contribute to satisfactory heat transfer even close to the baflles'2l.

The transfer of heat from the hotter vaporous medium to the colder fluid results in a condensation of vapor within the shell and the formation of a pool of condensate at the bottom. A valved connection 26 provides a. means for withdrawing condensate from the shell as required, for example, for cleaning, or for limiting the depth to which the condensate is permitted to accumulate. The level of condensate may be automatically maintained at a substantially constant predetermined value by means of a known type of fioating'device 21 having upper and

lower connections

28, 29 respectively to the vapor and condensate spaces of the vessel, and being operatively connected as by rod 30 to the valve 3| in the drain connection 26. I

The

pressure heads

3 and 4 are provided with access openings 32 which are fitted with removable covers or closure members 33, each in the form of a solid disc received within the cylindrical inner end portion 34 of the opening 32. The circumferential surface of the member 33 includes an inner portion 35 of a diameter providing a restricted clearance relative to the surface 34, and an outer portion 36 of reduced diameter providing an annular .recess 3'! for one or more layers of packing 38. The base 39 of the recess is inclined to the central axis of the opening and coincides with the surface of a cone hav ing its apex toward the exterior of the fitting. A follower ring 40 has an under bearing surface 4! in contact'with the packing of the same in- .clination as the base surface 39. A retainer ring 42 is screwed into the threaded outer end of the opening 32 and bears against the upper bearing surface 43 of the follower ring, the common areas -of contact between the

rings

42 and 40 being in a plane normal to the central axis of the fitting. The threads 44 are of relatively coarse pitch and loosely fitted with a clearance of about three times normal to facilitate assembly and removal. Tension members in the form of bolts 45 extend through openings 46 in the retainer ring 42 and are threaded into openings 4'! in the cover 33, nuts 48 being threaded on the bolts 45 for holding the part-s in proper assembled relation and for adjustably applying an initial compressive force on the packing 38 sufficient to seal the joint at low internal pressures. During normal operation, the pressure of fluid within the vessel exerts an additional compressive force which will cause the packing to expand radially and along the inclined surfaces of the recess and follower ring to further increase the tightness of the joint. Nuts 49 may be welded or otherwise secured to thef bolts 45 at their outer ends for convenience in turning the bolts into and out of the cover 33.

A joint is provided for each of the water connec'tions I 2, l3 which is similar in certain respects to that provided for the cover 33. The head 4 for example is counterbored to provide a transverse seating surface 50, a conical seating surface 5|, and a cylindrical joint surface 52 of a diameter providing an annular space 53 around the pipe l3. A base rin 54 of rhomboidal cross section as shown, may be welded to the pipe as by weld metal 65,, the ring providing an upper bearing surface 56 of conical formation relative to an apex toward the exterior of the head 4. The advantage in thus providing the desired enlargement at one end of the pipe or tubing I3 is that forging of the pipe ends is avoided, and theresulting welded connection is subjected to relatively low fiber stress because of the wide circumferential band over which it extends and because of the fact that longitudinal stresses in cylindrical hydraulic structures are only onehalf the radial stresses. The inner end of the compositely formed pipe I3, including the base weld metal 61.

ring 54 and weld metal 55, is shaped to provide surfaces companionate to the

counterbore surface

50, 5|, 52 in order to restrict the leakage path for fluid when the pipe I3, including its integrally associated parts, is in the normally seated position within the counterbore. A ring of packing 5'! is inserted within the annular space 53 and is contacted by the under bearing surface 58 of follower ring 59 of the same angularity as the opposing bearing surface 56 of base ring 54. A pipe joint bushing or nut 69 is threaded into the outer end of the counterbore, utilizing threads 6! of relatively large pitch and clearances, the bushing bearing against the outer surface 62 of follower ring 59 over a common area of contact in a, plane normal to the axis of the joint.

The expansion joints 9, I0 for connecting adjacent sections of the shell 2 are of a type permitting relative movement of the telescoping parts without subjecting the joints to longitudinal forces, and facilitatin external inspection of the tube bank throughout a substantial portion of its length. Referring to Fig. 2 in which joint 9 is detailed, the inner shell section 6 is provided with a circumferential band 63 having an outer facing 64 of corrosion-resistant metal, the band being secured to the section 6 as by weld metal 65, and a stop ring 66 being secured to the band 63 adjacent its inner margin as by When the facing 64 is formed of a separate metallic sheet. instead of an integral surface structure of the band 63, one edge of the facing sheet may be flanged over an edge of the band 63 as at 68 and held in place by the fillet weld 65, the other end being extended beyond the stop ring 66 and held in place by the fillet weld 61. The outer shell section 5 is provided with a stop ring 69 secured in position as by weld metal 10 and having a bearing surface H normal to the central axis of the section as a seat for the correspondingly surfaced removable filler ring 12 which forms the base of the annular packing space 73. The inner transverse surface 14 of the filler ring 12 is of conical formation relative to an apex toward the inner end of the inner section 6, the ring of compressible packing material 15 being clamped between the conical surface 14 and an opposing surface 16 of the same angularity on the follower gland 11. A flange 18 is provided on gland 11 for the accommodation of holding bolts I9 which are screwed into lugs on the outer shell section 5, a nut 8| being fitted to each bolt 19 for adjustably compressing the packing 15.

The form of heat exchanger illustrated in Figs.

7-10 inclusive is especially adapted for heating boiler feed-water by means of blow-down water from the boiler circulatory system, the pressures on both liquids ranging from about 2000 to 2500 lbs. per square inch. The device includes an elongated pressure vessel llll containing a bundle of U-tubes I 02 and having connections whereby one liquid is directed through the tubes while the other liquid is admitted to the interior of the vessel for intimate surface contact with the tubes.

.The vessel MI is formed of a plurality of shell sections circumferentially welded as at I03, the uppermost section I04 being fltted with inlet and outlet connections I05, I for one of the heat exchange fluids, the. lowermost section I01 forming a bottom end closure, and the intermediate section I08, or sections, providing the main cylindrical shell portion. The bottom section I0! is preferably fitted with a drain connection I09.

The uppermost section I04 has an end opening IIO which is closed by the pressurehead III including a cup-shaped member Hz to which the ends of U-tubes I02 are connected. The opening H0 is preferably counterbored to provide a cylindrical jointsurface H3, a transverse seating surface I I4, and an intermediate filleting surface II5, the cup-member II2 having external facing surfaces of similar formation. The member II2 is internally surfaced to include a cylindrical wall portion IIG within which thediscshaped closure member I I1 is received, a circumferentially sealed joint being formed between the members II! and H2 of the type provided for cover 33 (Fig. 2). Both joints employ similar parts in the same relation and such parts are sages I22, I23 through the member which are flared in the direction of the open ends of tubes I02. An advantage of making the inlet and outlet connections to. the tubes through the pressure sealed cover H1 is that the stresses and j necessary metal thicknesses are reduced in com-.- parison with head constructions wherein such connections are made through a cylindrical wall of the pressure shell. A diaphragm I24 extending across the spacebetween the cover Ill and the tube sheet portion I25 of cup member II2 maintains aseparation between the liquid flowing into, and out of tubes I02, the diaphragm being formed of spaced strips I26 attached to the cover III which resiliently engage the slotted member I21 on the tube sheet and permit relative movement.

The pressure head II I is circumferentially sealed in its assembled position within the'opening IIO,by means of a pressure-sealed joint of the same general type as used for cover I II, the upper rim portion of the cup member II2 being of reduced'dia'meter to provide a similar packing recess 31 adjacent the cylindrical joint surface I I3, the packing 38 being compressed between correlower pressures.

inside or outside the main shell without any additional parts.

The sealed joints for feed-water connections ently sealed to the wall of the shell along its longitudinal edges and on the side adjacent the inlet connection I05,-by means of sealing strips I33 formed of metallic laminations of varyin widths.

The path of fluid on eachside of the baflle I3l from inlet I05 to outlet I06 is increased and the surface contact with tubes I02 improved by 'a staggered arrangement of baflles such as I34, I35, I38, some of which (I34, I35) may extend partially across the bundle from one wall of the shell or the other, while others (I36) may traverse only an intermediate portion of the bundle. The arrangement of baiiles indicated in Fig. B is to be taken as a single illustration, since these or similar baffles may be used in various positions and numbers depending for exampleon velocity flow requirements or the extent to which the tubes need to be supported.

Heat exchangers of the type described have a fundamental characteristic in that the metallic components are relatively thin throughout, notwithstanding the very high operating pressures of one or both of theheat exchange fluids; at the same time the unit stresses are relatively low as compared with the high stresses involved in prior apparatus operating at the same or even The fact that the sizes of the pressure chambers are reduced to a minimum results in a decrease in pressure loading, thus contributing to lower material costs and weights, the latter being an important factor in providin adequate support of the devic in the plant.

spondingly inclined conical surfaces of the recess and follower ring 40. The holding bolts 45 pass through eircumferentially spaced openings in a It will be noted that in a device such as shown in Fig. 7, the pressure head. cup is utilized both as a tube sheet and as a pressure s aled closure for the main shell, thereby reducing the'number of joints to be sealed to a minimum and enabling the tubes to be testedunder full pressure either In the foregoing disclosure of the invention ref erence has been made to certain specific embodiments in explanation of the principles involved, in'accordance with statutory provisions; however, it is to be understood that variations may be made in the form of apparatus without departing from the spirit-of the invention, and that certain features may be useful irrespective of others.

I claim:

1. In a heat exchanger comprisingan elon cylindrical wall portion fitting Within the cylindrically walled shell opening and an end wall portion formed as a tube sheet to which adjacent ends of said tubes are connected, said vessel having an opposite end wall portion comprising a closure plate received interiorly of said cylindrical wall portion, means for circumferentially sealing said closure plate to said vessel and said vessel to said shell, and means for transmitting pressurevessel and on saidtube sheet from within said shell to the walls of saidpressure vessel and shell respectively, said means for transmit ting fluidpressure forces to said shell comprising a retainer ring within saidshell opening of smaller inside diameter than the outside. dia'mi eter of said pressure'vessel.

2. In combination, fora heat exchanger comprising 'an elongated shell, a pressure -.,vessel for closing said shell at one end,-a bundle of-tubes for disposition within said shell having inflow and outflow connections with said vessel, said .vesselhaving an opening providing access to said tubes v and means for. removably closing said opening including a cover movable within and substantially filling said opening, means forming compartments withinsaid vessel including a diaphragm separating said inflowand outflow connections, said diaphragm extending between relatively movable opposite walls, of said vessel-and being movablyi sealed to one of said walls, means including pasopening terminating in a base surface of which I associated with one .of said covers.

5. A pressure vessel having a counterbored opening in' a wall thereof, the counterbore of said the major portion is of concentric conical formanon tapering inwardly from substantially the maximum diameter of said counterboraa fluid flow connection to said vessel comprising a tubular member jinserted within saidopening and sages through said cover for admitting fluid under pressure to one of said compartments and fordischarging said fluid from another, means for circumferentially sealingsaid cover to said vessel in eluding a retainer ring received im said opening and acting to transmit thrust due to internal pressure on said cover to the wall o f, said vessel packing material positioned between 'said cover and ring forlsealing, and means'cooperating in' tension with said ring and cover for applying a compressive force to said packing.

3. In a heat exchanger, a pressure vessel, a bundle of tubes having inflow and outflow connectionswith said vessel, ,saidvessel having an openi'ng providing access to said tubes andmeans for closing said opening. includinga cover disposed within and substantially filling said opening,

means for'mingcompartments within said vessel including a diaphragm separating said inflow and outfiow.con.nections, said diaphragm extending substantiallycentrally across said vessel between opposite walls thereof, said cover providing one of said-walls, neans'including passages through said cover. for admittingfluid under pressure to one of said compartments and for discharging said fluid from another, said passages having inlet portions disposed more nearly adjacent the central portion of said cover than the peripheral limits 'of said cover and tube connections, said passages having their inner ends flared eccentrically. toward the periphery of said tube connections; .means for circumferentially sealing said cover to said vessel including a retainer ring received in said opening for transmitting thrust dueto internal pressure on said cover t the wall of "said vessel, and inlet forming. therewith an annular packing space about .said member, said member having an en,- largement atits inner end formed with a conical end surface adapted to enter into centering engagementwith the conical base surface of said counterbore, said enlaregeineiit being formed with a conical bearing surface of opposite angularity at the innerend of said annular packing space, whereby the longitudinal dimension of said enlargement is maximum at itsjuncture with said I tubular member, packing material within said space, an annular sealing member having a contacting surface with said packing materia1 of substantially the same angularity in the same direction as said bearing surface, and a bushing threaded within said counterbore formoving said tubular and sealing members relatively for cir-' culmferentially sealing said-member to said ves- S i 6. A pressure vesselehaving -a counterbored opening in a'wall thereof, the counterbore of said opening terminating in a base surface of which the major portion is of concentric conical formation tapering inwardly from substantially the maximum" diameter of said counterbore, a fluid flow connection to said vessel comprising a tubular member inserted within said opening and forming therewith anannular packing space; about said member, said member having an-enlargementat its inner end formed with a conical end surface adapted to enter into centering engagement with the conical base-Surface of said counterbore, said enlargement comprising a ring of substantially rhomboidal cross-section and weld metal joining-said ring to the body portion of said member, one face of said ring defining a and outlet connections for said passages extending through the central opening in said retainer ring. I 4. In a heat exchanger, an elongated shellhav ing a cylindrically formed opening at one end for access to its interior, a pressure vessel within said shell opening constituting a removable cover therefor, said pressure vessel having a cylindrical side wall portion defining an access opening at its outer end and having atransverse inner wall portion at the end adjacent the interior ofsaid shell, said pressure vessel having a removable cover within said outer end opening forming the outer end wall portion of said .vessel, means for admitting fluids under pressure to said shell and vessel, means for sealing said covers in said shell portion, said weld'metal providing said conical end centering surface, the opposite face 'of'said ring providing a conical bearing surface of opposite angularity at the inner end of'said annular packing space whereby the longitudinal dimen, sion of said enlargement is maximum at its juncture with said body portion,- packing material within' said space, an annular sealing member having a contacting surface with said packing. material of substantially the same angularity in e the same direction as said bearing surface, and

a bushing threaded within said counterbore for moving said tubular and sealing members relatively for circumferentially sealing said member to said Vessel.

- JAMES C. HOBBS.