[1]2 1 7 5 6 @ 0 2 8 United States Patent Office Patented July 24, 1956 2,756,028 ]BEAT EXCHANGE APPARATUS 5 Wilbur M. Byerley, Ridley Park, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 24, 1953, Serial No. 382,03'1 10 4 CUms. (Cl. 257-32) This invention relates to heat exchangers, such as feed- 15 water heaters, provided with verticary disposed water tubes forming a plurality of passes, more particularly to feedwater heaters of the above type having a desuperheatinsection in the last pass. In heat exchangers of the above type, it is desirable 20 to provide a shell which is removable for periodic tube inspection . Also, it is essential that condensate be prevented from forming or collecting within the desuperheating section, since condensate collected within the desuperh eating section defeats the purpose of that sec- 25 tion. In such a heat exchanger, it is also desirable to have a drain cooling section spaced horizontally from the desuperheating section. Since the flange connections for the shell are disposed in the lower region of the heat excliange r and encompass the drain cooling section and 30 the considerably hotter desuperheating section, maintaining the ff anges at a uniform temperature, which is essential to prevent buckling of the flanges, becomes a problem. It is an object of the invention to provide a feedwater heater of the above type having a vertically removable 35 shell in which leakage of fluid to atmosphere through the shell connection is substantially eliminated. It is a f arther object of the invention to provide a feedwater heater of the above type in which the flange connectio n means for the shell is maintained at a sub- 40 stantially common temperature throughout its periphery. A more specific object is provide, in a feedwater heater of the above type having a desuperheating section and a drain cooling section disposed at the bottom, an arrangement whereby the shell flange connection 45 means is in good heat transfer relation with fluid of substantially uniform temperature. These and other objects are effected by the invention as will be apparent from the following description taken in connection with the accompanying drawings, forming a part of this application, in which: 50 Fig. I is a central vertical section showing a heat ex- . changer embodying the invention, portions having been omitted for clarity of illustration; Fig. 2 is a cross section taken on line III-II of Fig. 1, looking upwardly; and 55 Fig. 3 is a cross section taken on I'me III-111 of Fig. 1, looking downwardly. Referring to the drawing in detail, there is shown a heat exchanger, generally designated 10, having a plu- 60 rality of vertically disposed U-shape or hairpin tubes 12 attached at their lower ends to a header member 14. The header rnember 14 is provided with an inlet chamber 16 and an outlet chamber 18 communicating with the open ends of the tubes 12. Thus, feed water for a boiler or the like (not shown) admitted to the inlet 65 chamber 16 flows upwardly through the tubes 12 to provide a first water pass a and thence downwardly to provide a second water pass b, from whence it discharges into the chamber 18 in a heated state, as will subse- 70 quently be described. The tubes 12 are disposed within a shell comprising a lower shell portion 20 attached at 2 its lower periphery to the header 14 and an upper shell portion 22 of inverted cup-shape. The lower and the upper shell portions 20 and 22, respectively, are provided with mating flange members 24 arranged to be clamped together by means of bolts 26 to seal the heating fluid provided therein, for example, superheated steam, from the atmosphere. A desuperlieating section 28 is provided in the lower portion of ' he second pass b by vertically extending tubular baffle structure 30, of generally semicircular cross section, enveloping the tubes 12 and defining a semi-annular space 32 with the upper and lower shell por@ons 22 and 20, respectively. The lower edge portion of the baffle structure 30 is attached to the upper surface of the header 14 in any desirable manner to provide a leakproof joint therewith. A cap member 34 hiving an upper horizontally disposed plate 35 and a downwardly extending peripheral flange portion 36 is stipported by the tubes 12 in a fluidt@.ght manner and is so positioned relative to the baffle structure 30 that the depending portion 36 encompasses the upper portion of the latter and together therewith defines a downwardly directed steam passage 38 coi-nmunicating with a main cooling space or condensing section 39. A steam inlet pipe 40 is provided in the lower shell portion 20 and extends therethrotigh into communicatiori with the desiiperheating section 28. A vent connection 42 is provided in the upper shell portion 22. Thus, superheated steam entering through the inlet connection 40 circulates upwardly through the desuperheating section 28 losing a portion of its superheat to the tubes contained therein and thence passes through the passage 38 at the upper end of the desuperheating section 28 into the condensing section 39, and condensing on its way upward. Any air and non-condensable gases are passed through the vent connection 42. A number of horizontal baffle plates 44 and 46 may be provided in the desuperheating section and the condensing section, respectively, ',O form a tortuous path for the steam, indicated by the arrows c, as it circulates through the heat exchan,-er. Although the manner in which the baffles 46 are supported on the tubes 12 has not been shown in detail, it will be understood that they may be supported thereon in any desired manner., The baffles 46 and the cap member 34 for the desuperheating section have been shown as spaced slightly from the vertical wall of the upper shell member 22 to permit removal of the shell by lifting upwardly thereon after the bolts 26 have been removed froi7.i the flanges. This spacing is on the order of 1/16" in actual practice but has been exaggerated for clarity of illustration. By properly designing the desuperheating section 28, none of the stiperheated steam will condense therein, but condensation will occur after discharge therefrom into the condensing section 39. As condensate forms in the condensiiig sectio-@i and drops downwardly, that portion of the condensate which falls above the desuperheating section 28 is diverted by the cap member 34 so that no moisture enters the desuperheating section 28 but is permitted to accumulate exteriorly of the desuperheating section 28. A drain coolin.a section 48 is provided in the lower portion of the first pass a in side-by-side relation with the desup-@rheating section 28 and includes a baffle struc-' ture 50 having an upper tubular i)ortion 52 of generally semi-circular cross section enveloping the lower portion of the tubes 12 in the first pass a and a vertical partition 54 extending downwardly beyond the edge of the portion 52 and resting on the upper surface of the header 14. The partitibn 54 is attached to the header 14 in a fluidtight manner. The semi-circular portion 52 is spaced
[2]2,756,028 3 from the upper and lower sheu portions 22 and 20, respectively, and forms therewith a semi-annular space 56. The space 56 is closed at the lower end of the portion 52 by a semi-annular plate 51'. attached to the lower edge of the portion 52 and extending radially outwardly 5 tlierefron-i. Thus, it will be seen that - condensate forming in the main cooling chamber n-iay fall into the confities of the drain cooling section 48 and also around the baffle strticture 50 defining the same. A draiii connection 58 connected to the drain cooler 10 througb the lower portion of the shell serves to drain condensate fornied within the heat exchanger. A liqtiid level control mechanism, generally designated 60, of aii@r desire(] type having a valve 62 movable to open position by upward movement of a float mechanism 15 64 aid i-novable to closed position by downward movenieiit of the -,Ic,@it -@nechanism 64, is attached to the dischar,qe outlet 58 to control flow of condensate therefrom. As w,-Il understood in the art, the float mechanism 64 is cont,@iiied within a cbamber 65 having a pipe connec- 20 I;on 66 with the atmosphere %vithin the upper portion of the shell ,nd having a pipe contiection 67 with the upper portioii of ttie sliell at a level below that of the controlled heitht of the condensate. The liquid level control mechaii-'@sm 60 is adjusted to maintain the level of 25 the condensate witliin the heat exchanger at a height above the upper edge of the baffle structure 50 forming the drain cooling section 48, but below the outlet passage 38 e-f ibe desuperheating section. The drain c(,,oling section 48 may be provided with a 30 plurality of horizontal baffle plates 69 to provide a torti-7otis patli for the condensate, as it circulates therethrough on its way to the drain outlet 58, as indicated by the arrows d. O.peration 35 The beat exchanl-er heretofore described operates in substo.ntial@'@, the following manner. Superheated steam is admitted to the desuperheating section 28 through the stea.m inlet 40 znd circulates udwardly - therethrough in 40 a tortuciis path ,).roLnd the baffles 44 and the tubes 12 in the direction of the arrows c. At the upper end of the destiperheatin.- secti6n, the steam is deflected downwardly by the cap member throiigh the passage 38 into the condepsinp section 39. The superheated steam, in 45 circulatiiig tbrough the d-,superheatin.- s.-ction, loses a considerable amount of heat to the second water pass b. However, it retains a sufficient amount of superheat to prevent condensate forming therein. Upon entering the condensing section, the steam circu- 6( lates tipwardly from side to side around the baffles 46 and the tubes 12 losing its remaiding heat on its wa y upwardly to the vent 42. The steam will condense and fall down@vardly to the lower portion of the condensing section, flooding the region around the desuperheating 55 section 28 and filling the semi-annular space 32, the semiannular space 56 and the drain cooling section 48 to the level previously described. It wil.1 tbus be seen that the semi-annular spaces 32 and 56 form a continuous tubular wall of water extend- 30 ing from below the flanges 24 tipwardly above the flanges and shicididg them from the differences in tempertures between the desuperheating section 28 and the drain cooling sectioq 48. Since the water is at a stibstantially uniform temperattire, the flange members 24 are uniformly 65 heated tliroiivhout their peripheries, so that uneven expansion therein does not occur and buckling strains which would affect the seal formed thereby are substantially eliminated. It will also be noted that with the above arrangement 70 a desuperheating section and a drain cooling section may be advant-,igeously incorporated in a plural water pass heat exchanger in which the water tubes are mounted vertically and the upper'shell 22 is removable for inspection of the tubes. 75 4 While the invention his been shown in but one form, it will be obvious to tl-lose skilled iia the art that it is not so limited, btit is susceptible of various changes and modifications kNithout departing from the spirit thereof. What is
