US3420293A - Tubular heat exchanger with thermostatic valve - Google Patents

Description

Jan. 7, 1969 R. L. CAMPBELL 3,420,293

TUBULAR HEAT EXCHANGER WITH THERMOSTATIC VALVE Filed May 4, 1967 HIS A OR/VEY MN NN United States Patent O 3,420,293 TUBULAR HEAT EXCHANGER WlTH THERMOSTATIC VALVE Robert L. Campbell, Dayton, Ohio, assignor to United Aircraft Products, Inc., Dayton, ho, a corporation of Ohio Filed May 4, 1967, Ser. No. 636,187 U.S. Cl. 165-39 Int. Cl. F285. 27/00 9 Claims ABSTRACT F THE DISCLGSURE This invention relates to tubular heat exchangers, and particularly to a generally new construction and mode of operation of devices of that class wherein a control valve assembly is disposed in the core of the heat exchanger and extends through one end thereof to control flow of the tube side iluid.

An object of the invention is to provide a heat exchanger as described of a more compact form than were the control valve assembly to be externally located, as is conventional.

Another object of the invention is to provide a relationship of parts such that the control valve assembly is more sensitive to a sensed condition to achieve a stabilized temperature control.

A further object of the invention is to provide a. heat exchanger well constructed for growth in heat transfer capability without increasing the size of the heat exchanger itself.

Still another object of the invention is to provide a construction as described lending itself to ease of assembly and which is essentially trouble free in operation.

Other objects and structural details of the invention will more clearly appear from the following description, when read in connection with the accompanying drawings, wherein:

FIG. l is a view in longitudinal section of a tubular heat exchanger in accordance with the illustrated embodiment of the invention;

FIG. 2 is a view in cross section, taken substantially along the line 2-2 of FIG. l; and

FIG. 3 is a `fragmentary detail view of an alternate form of valve control.

Referring to the drawings, a tubular heat exchanger in accordance with the illustrated embodiment of the invention comprises an elongated tubular shell open at its opposite ends. Near such ends are respective header plates 11 and 12. These are tube sheets, accommodating the opposite ends of heat transfer tubes 13 in through holes drilled or otherwise formed in the plates. The tubes 13 extend between and interconnect the plates 11 and 12 and have a thin walled metallic construction for an eflicient conducting of heat through the walls thereof.

The opposite ends of the tubes 13 open through and beyond the respective header plates 11 and 12.

At one end of the shell 10 is an adapted ring 14 to which is bolted or otherwise secured a closure cap 15. A metallic O-ring 16 or the like is installed between cap and adapter ring 14 to seal against escape of pressure fluid from a chamber 17 formed between cap 15 and the adjacent header plate 11. The cap 15 has a central portion defining a pad 18 parallel to the header plate 11. On the inner surface of pad 18 is a recessed surface 19 machined to provide a flat valve seat. In the center of seat 19 is a longitudinal through opening 21 in pad 18 positioned to be concentric with shell 10 and header plate 11. Projecting from the outer surface of pad 18 is a boss 22 formed for connection with a fluid flowing conduit and having a central bore 23 communicating through opening 21 with what may be considered an end chamber 17.

At the opposite end of shell 10 a similar end chamber 2.4 is formed through the cooperation of an adapter ring 25 and a closure cap 26. In this instance, cap 26 has a rearwardly projecting boss 27 for connection in fluid flowing conduit. It has further an inwardly projecting cylindrical portion 28 terminating in an expanded flange 29 received in a sleeve 31 installed in a central opening 32 in header plate 12. Inwardly and outwardly projecting portions of the cap 26 have a common bore 33 opening through outer boss 27 and terminating in a vertical wall 34 from which expanded flange 29 projects. Radial openings 35 communicate bore 33 with end chamber 24.

The above described construction and arrangement of parts is one in which a tube side -uid may enter shell 10 at one end, distribute itself in an end chamber and flow longitudinally through the tubes 13 to the other end chamber and out of the shell. The shell 10 has openings 36 and 37 between the header plates 11 and 12 and respectively adjacent such plates. A shell side lfluid enters the shell by one of these openings, flows over and around the tubes 13 and leaves by way of the other opening. The tube side fluid and shell side fluid accordingly are in heat transfer relation to one another through the walls of tubes 13 and, in accordance with the general mode of operation of devices of this class, the iluid of higher temperature yields up some of its heat to the fluid of lower temperature. More effective heat transfer takes place if the shell side fluid is not permitted to flow directly between the openings 36 and 37 but rather is required to flow circuitously through the shell 10` making a number of generally cross flow passes across the tubes 13. To this end, longitudinally spaced apart batlles 3-8, 39 and 41 are disposed in shell 10 in transverse relation to the tubes 13. The baffles 38, 39 and 41 have a height corresponding approximately to three-fourths the internal diameter of shell 10. Seated to the shell interior on one side thereof the batlles accordingly provide a flow area between their outer ends and the opposite side of the shell. Arranged in an alternating order as illustrated, the baffles compel cross flow of the ilowing shell side fluid in s-uccessive passes as described. In the illustrated instance the opening 36 serves as the inlet for the shell side fluid while opening 37 is the outlet. Shell side tluid enters the shell at opening 36, is constrained by baille 38 to ilo-w across the bundle of tubes 13 to the opposite of the shell. There it is allowed to pass over the outer free end of baflle 33 and as compelled and directed by subsequently encountered baffles 39 and 41 makes successive passes across the tube bundle, the nal pass flowing the fluid transversely between baffle 41 and header plate 12 toward outlet 37.

Flow the shell side fluid to and from the shell 10 is by -way of an underslnng housing 42 attached to the shell exterior in a closing relation to openings 36 and 37. Housing 42 has an inlet 43 and an outlet 44 separated by a partition wall 45. In the latter is a through opening 46. A closure member `47 is mounted to one end of the housing `42 and slidably receives the stem of a valve 48 adapted to seat on partition 45 in a position closing opening 46. A compression spring 49 urges valve 4S to a seated position.

Shell side fluid enters the heat exchanger by Way of inlet 43, flows longitudinally of housing 42 to shell inlet 36. Flowing t-hrough the interior of shell 10 in the manner described, the shell side fluid discharges from shell outlet 37 and leaves the heat exchanger by way of outlet 44. Valve 48 normally denies by-passing flow between inlet 43 and outlet 44, compelling the shell side fluid to travel the described lroute through shell 10. However, in the presence of a pressure drop sufficient to overcome spring 49, valve y48 opens, allowing at least a part of the flowing fluid to pass directly to outlet 44.

The pressure of shell side fluid within the core of the heat exchanger thus is limited to a predetermined high value.

The tube side fluid enters t-he heat exchanger by way of boss 22, collects in chamber 17 and flows through tube 13 to chamber 24, leaving the heat exchanger by way of openings 35 and bore 33 in closure cap 26. The flow of tube side fluid is controlled by valve -means in the form of a cylindrical stem 51 cooperative with pad 13 to control flow through opening 21. The extremity of valve means 51 is blunt and recessed to provide an annular surface 52 adapted to engage seat 19 on pad 18 with a flush mating contact. The valve means is positioned to be concentric 'with opening 21, with surface 52 engaging seat 19 in a surrounding relation to opening 21 thus closing the opening in a seated position of the valve. The cylindrical valve stem 51 projects from one end of a cylindrical valve body 53 slidably mounted in a tubular housing 54. The housing 54 is received in a longitudinally nested relation to the bundle of tubes 13. It is concentrically disposed with respect to shell 10, within the shell, and has one end received in a central opening 55 in the header plate 11. The extremity of the tubular housing is flared into secure engagement with header plate 11, to anchor one end of the tubular housing. The other end terminates within the shell in spaced relation to the other header plate 12. Central openings in the baffles 38, 39 and 41 receive the housing 54 with a moderately close fit and assist in maintaining it positioned as illustrated.

Longitudinal sliding motion of the valve body 53 extends and retracts the outer end of valve means 51 relative to valve seat 19. The valve `body and integral valve stem extension 51 are parts of a control valve assembly further including a power type thermostat 56. The latter is a known type of device comprising a casing 57 containing a thermally sensitive material having the capability -of expansion with considerable force when heated. Case 57 is disposed to project from the inner end of tubular housing 54 in a manner to lie across the final pass traversed by the shell side fluid as it flows to shell outlet 37. The thermostat case accordingly is contacted by the shell side fluid under conditions in which the thermally sensitive material is exposed to the shell side fluid at the temperature at which it discharges from the heat exchanger core. The case S7 has a reduced diameter shank portion 58 extending into a vbushing 59 installed in the tubular housing 54 in a manner to be secure against relative longitudinal motion therein. The reduced diameter portion 58 terminates in a threaded stud 61 extending through the closed `bottom of bushing 59 and having a threaded connection therewith. A nut 62 locks the threaded stud 61 to bushing 59. Within the thermostatic power unit and extending longitudinally of reduced shank portion 58 and stud 61 is a plunger 63 extending through and beyond stud 61 toward valve body 53. The adjacent end of valve `'body 53 is open to a longitudinally recessed portion in which is a compression spring 64 projecting a piston 65 outwardly or rearwardly in the valve body, this motion being limited by an installed ring 66. Spring 64 urges piston 65 outwardly or rearwardly of the valve body 53 while a coil spring 67 urges the valve body S3 rearwardly or in a direction to cause piston 65 to engage plunger 63 with which it is aligned. The spring 67 is seated on a limit member 68 held in the tubular housing 54 near its one end within header plate 11 by a retainer ring 69.

The plunger 63 extends axially toward valve body 53 in the presence of a rising shell side fluid temperature, as sensed `by thermostatic power unit 56. The plunger acts on piston and through spring 64 moves valve body 53 axially to advance valve stem means 51 toward pad 18. At a predetermined high shell side fluid temperature the valve means 51 seats on pad 18 and closes off flow of the tube side fluid through opening 21. Should the shell side fluid temperature continue to rise and plunger 63 continue to extend, this motion is absorbed in an inward movement of piston 65 relative to body 53, compressing spring 64. The valve closing motion compresses spring 67 and provides a force for return of the valve body when the shell side fluid temperatures decrease. As such temperature reduces from a peak high value, the spring 64 initially returns piston 65 from any overtravel, forcibly retracting plunger 63 and recompressing the thermally sensitive material in case 57. As piston 65 reaches retainer ring 66 the continued retraction of plunger 63 is a function of bodily movement of valve body 53 as compelled by expanding spring 67. The described movement of body 53 serves also to retract valve stem means I51 from seat 18, reestablishing flow of the tube side fluid through opening 21.

The valve body 53 has external `bearing flanges 71 and 72 by which it is slidably mounted in housing 54. These have respective cutout portions 73 and 74. The limit member 68 has similar cutout portions 75. The construction is one to admit tube side fluid to both ends of valve body 53. In an open position of valve stem means 51, therefore, the body 53 is substantially balanced against the effects of fluid pressure so that its movements are a function solely of the opposing described spring and thermostatic influences.

The control valve assembly operates to maintain a minimum or maximum temperature value of the shell side fluid. In one environmental use to which the device of the illustrative embodiment is adapted, the tube side fluid is hot air under pressure, as drawn from the compressor of a jet engine while the shell side fluid is fuel en route from a place of storage to the engine. The heat exchanger with control valve assembly functions to heat the flowing fuel when heating is necessary to avoid icing conditions. Thus, at low fuel temperatures as for example temperatures below 45 F. valve means 51 stands in an open position, allowing hot air t-o enter the heat exchanger through opening 21 and to flow through tubes 13, thereby heating the fuel flowing over and around the tubes. As the temperature of the flowing fuel rises, in response to such heating, thermostatic power unit 56 reacts by projecting plunger 63 and moving the valve body to close or further to restrict flow of the incoming hot air. The heating effect thus is reduced as required or alternatively is turned on and off as temperature requirements of the fuel may indicate.

Use of a thermostatic power unit 56 as the sensor has practical advantages, as for example obviating the need for servomechanisms and the like. Within the instant inventive concepts, however, the thermostatic power unit could be replaced by bellows or the like responding to changes in pressure drop of the shell side fluid or to other changing conditions of the shell side fluid, with intermediate means effecting adjustment of a valve means 51. Alternatively, the bushing 59 and mounted thermostat could be replaced by an electric solenoid suitably controlled to project and retract a plunger corresponding to the plunger 63 to effect bodily movements of a valve `body within housing 54.

In the illustrated embodiment of the invention, heat transfer tubes 13 are provided in rows forming an assembly which at its top and bottom is spaced a substantial distance from side walls of the shell 10. The result is to provide above and below the tube bundle flow chambers of low flow resistance. The total pressure drop across the heat exchanger for the shell side fluid thus is relatively low. Also the shell side fluid is enabled easily to distribute itself before beginning each pass across the tube bundle for uniform flow through such pass.

As indicated, the internal placement of the control valve assembly lends compactness to the heat exchanger combination, provides for the sensing of true temperature values and avoids lag or delay in response. The construction lends itself to simplified installation of the control valve assembly, as well as access for inspection and replacement. The expanded liange 29 seated in and closing a larger center opening in header plate 12 is integral with end closure cap 26. Removal of this cap withdraws ange 29 and opens thermostatic unit 56 to access. In assembling the heat exchanger parts thereof are interconnected in subassemblies and brought together. Thus, the header plates 11 and 12, tubes 13 and baffies 38, 39 and 41 define a core which in the present instance further includes tubular housing 54 and installed bushing 59. These parts are assembled together and placed in the shell with the resulting assembly being subjected to a brazing operation. The subassembly comprising housing 42 and valve 48 is secured as by welding to the exterior of shell 10. Thermostatic power unit 56 is inserted through header plate 12 to seat in bushing 59 with its stud 61 projecting therethrough. From the opposite end of the tubular housing, using a suitable tool, jam nut 62 is secured in place. Valve body 53 is installed from the same said opposite end of the tubular housing, assuming a position wherein valve means 51 projects through and beyond header plate 11. Installation of spring 67, limit means 68 and retainer ring 69 adjusts the valve body to a position of contact with thermostatic plunger 63. The end caps 15 and 26 are bolted in place to respective rings 14 and 25 which may be secured to the shell 10 as a part of the brazing process. Pad 18 is placed thereby in an adjacent facing relation to the surface 52 on valve means 51 With the parts being ready for cooperative action as described.

The reduced diameter portion 58 of the thermostatic power unit 56 has `O-ring seals 76 and 77 mounted thereon. Other seals 78 are installed in the periphery of expanded flange 29. As a result the tube side and shell side iiuids are separated in a manner to preclude mixing.

Mounting of the valve components in a center tube within the core assembly -has particular utility in an environmental use as presently described. The thermostatic power unit is protected by contact by excessive air temperatures as is overtravel spring 64 and to a large extent compression spring 67 as well. Both springs are out of the main hot air flow path. The flowing hot air moves with considerable pressure and velocity effects. The support of tubes 13 by baiiies 38, 39 and 41 substantially inhibits vibratory action.

The heat exchanger valve combination disclosed is designed for growth. Increased heat transfer performance can be obtained by lengthening the path of flow of the shell side iiuid over the tubes, through use of additional baiiies, within allowable pressure drop specifications. Minor modifications to the modulating air iiow control by increasing the valve diameter seat will increase available air flow. The surface area within the tube bundle can be increased a substantial amount with a minimum increase in allowable fuel pressure drop by adding rows of tubes 13. All growth changes can be made in an existing heat exchanger construction.

Valve surface 52 engages valve seat 19 with a substantially square contact inhibiting leakage. By controlling the clearance between the flanges 71 and 72 of the valve body with respect to tubular housing 54, the valve may be made self-adjusting within limits to assure a uniform contact between surfaces 52 and 19.

As indicated above, the control valve assembly lends itself to other forms wherein temperature or pressure sensing means, or manually actuated means, indirectly effects flow control of the tube side iiuid. An example appears in FIG. 3 wherein a tubular shell 79 mounts header plates ,81 (one shown) between which are disposed heat transfer tubes 82. An end cap 83 closes one end of the shell 79 and defines with the adjacent header plate 81 an intermediate chamber 84. A central opening in cap 83 admits tube side fluid under pressure to chamber 84 to flow longitudinally through tubes 82. Flow through opening 85 is controlled by a sleeve type valve 86 having a tapered nose portion 87 and a cylindrical skirt portion 88, the latter being slidable on a stationary boss-like projection 89 integral with insert means 91 installed in an end of a tubular housing 9 2 corresponding to the tubular housing 54 of the FIG. l embodiment. The housing 92, like housing 54, is fixed to be longitudinally disposed in the tube bundle and to project at one end into and through a header plate 81. The boss-like projection 89 is open at its end into the housing 92 and is closed at its other end except for a restricted orifice-like opening 93. A needle valve 94 extends from housing 92 through header plate 81 into boss-like projection 89 and is adapted to seat in to close orifice opening 93. A spring 95 may be provided to -urge valve 94 to a closed position While temperature or pres sure sensing means installed in housing 92 within the heat exchanger core are provided to retract the valve to an open position. The tapered nose valve 87 has a reduced diameter opening 96 in its center. Radial port means 97 connect the interior of boss-like projection 89 to chamber 84.

Operation of a device as illustrated and described will largely be self-evident. Tube side fluid is free to flow through opening 85 through restricted passage 96 into a chamber 98 interiorly of valve 87. With valve 94 closed pressure in chamber 98 reacts on the outer end of bosslike projection 89 and urges valve 87 closed, the valve `87 presenting a larger surface area to closing pressure than is provided to an opening pressure at opening 85. Upon retraction of valve 94, however, the pressure in cham'ber 98 reduces whereupon the pressure available to force valve 87 open is effective to open the valve and iiow of the tube side fluid in volume takes place through opening 85 directly into chamber 84.

What is claimed is:

1. A tubular heat exchanger, including a shell; spaced apart header plates in said shell; heat transfer tubes extending between said plates and defining a tube bundle, tube side and `shell side fluids iiowing in heat transfer relation respectively through and around said heat transfer tubes, means attaching to said shell in an adjacent spaced relation to one of said header plates having a tube side iiuid flow lopening in series relation to said tubes, a modulating tube side fluid fiow control valve assembly disposed longitudinally of said shell within the tube bundle, including valve means extensible through said one header plate and cooperating with said attaching means to control iiow of tube side fluid through said opening therein, a tubular housing longitudinally nested in said tube bundle and mounting said control valve assembly therein, one end of said tubular housing being open and interengaging with said adjacent header plate to align with an opening therein through which said valve means projects, said control valve assembly further including a valve body slidable in said tubular housing and means to extend and retract said valve body therein, said attaching means including a pad upon which said valve means seats in response to an extending motion of said valve body to close the opening in said attaching means, the other end of said tubular housing terminating within the tube bundle between said header plates, and la thermostat anchored in to react on the said other end of said tubular housing, said thermostat having temperature housing sensing means projecting beyond the tubular housing into the tube bundle to be contacted by the shell side fluide flowing over the heat transfer tubes, -said thermostat fuurther having a plunger projecting into the tubular housing to engage said valve body, a rising shell side fluid temperature extending said plunger correspondingly to extend said valve body.

2. A tubular heat exchanger according to claim 1, characterized by spring means opposing extension of said valve body and operable upon a lowering shell side fluid temperature to retract said valve body and said plunger.

3. A tubular heat exchanger, including a shell; spaced apart header plates in said shell; heat transfer tubes extending between said shell; heat transfer tubes extending between said plates and defining a tube bundle, tube side and shell side fluids flowing in heat transfer relation respectively through and around said heat transfer tubes, means attaching to said shell in an adjacent spaced relation to one of said header plates having a tube side fluid flow opening in series relation to said tubes, a modulating tube side fluid flow control valve assembly disposed longitudinally of `said shell within the tube bundle, including valve means extensible through said one header plate and cooperating with said attaching means to control flow of tube side fluid through said opening therein, said attaching means having the form of a pad, said valve means being extensible to seat on said pad to close the opening in said attaching means and retractable to allow flow through said opening, and a tubular housing longitudinally nested in said tube bundle and having an open end received in said adjacent header plate to communicate therethrough with the space between said adjacent header plate and said attaching means, the control valve assembly being mounted in said housing and further including a thermostat installed in to project from the opposite end of said tubular housing to sense the temperature of the shell side fluid, and said control valve assembly still further including a valve body slidable in said housing and terminating at one end in said valve means, a yielding connection being interposed between said thermostat and said valve body accommodating overtravel of said thermostat after seating of said valve means on said pad.

4. A tubular heat exchanger according to claim 3, characterized by means for substantially balancing said valve body endwise in said housing against the effects of tube side fluid pressure.

5. A tubular heat exchanger, including a shell and a cap closing one end of said shell and having a tube side fluid flow opening therein, spaced apart header plates in said shell, said shell having spaced apart openings between said header plates for in-llow and out-flow of a shell side fluid, a tubular housing longitudinally disposed in said shell and spaced from the walls thereof, a control valve assembly mounted in said tubular housing and extensible through one of said header plates to control flow of the tube side fluid through said closing gap, and heat transfer tubes in said shell extending between and interconnecting said header plates, said tubes being arranged in multiple transverse rows substantially to surround said tube housing, said control valve assembly including a rst valve adapted to seat on said cap to close said opening therein against the pressure of tube side fluid and providing an interior chamber in which tube side fluid is admitted to maintain said first valve normally closed and said valve assembly further including a second valve extensible from within the tubular housing to deny and permit escape of fluid from said interior chamber.

6. A tubular heat exchanger, including a shell and a cap closing one end of said shell and having a tube side fluid flow opening therein, spaced apart header plates in said shell, said shell having spaced apart openings between said header plates 'for in-flow and out-flow of a shell side fluid, heat transfer tubes in said shell extending between and interconnecting said header plates, said tubes for-ming a tube bundle, means constraining the shell side fluid to flow over the tube bundle in a plurality of passes, a tubular housing longitudinally disposed in said shell nested within the tube bundle, a control valve mounted in said tubular housing and extensible through one of said header plates to control flow of the tube side fluid, and thermostatic means disposed between said header plates in said tube bundle in the path of llow of the shell side fluid as it flows through one of said passes to operate said valve.

7. A tubular heat exchanger according to claim 6, characterized in that said control valve includes a first valve movable against the pressure of incoming tube side fluid to close flow through the opening in said cap and providing an interior chamber in which tube side uid is admitted to maintain said first valve normally closed and said control valve further including a second valve extensible from within the tubular housing to deny and permit escape of fluid from said interior chamber.

8. A tubular heat exchanger according to claim 6, characterized in that said thermostatic means is anchored in to react on said tubular housing, said housing being formed freely to expose said thermally sensitive end to the flowing shell side fluid.

9. A tubular heat exchanger according to claim 8, characterized in that said thermostatic means is positioned to dispose the thermally sensitive and thereof opposite the out-flow opening in said shell in the final one of said plurality of passes.

References Cited UNITED STATES PATENTS 1,344,423 6/1920 Manker 236--19 1,881,771 10/1932 Lyman 236-93 3,109,589 11/1963 Kimm 165-39 XR 3,145,928 8/1964 Parker et al. 165-158 XR 3,353,590 11/1967 Holman 165--158 XR ROBERT A. OLEARY, Primary Examiner.

MANUEL A. ANTONAKAS, Assistant Examiner.

U.S. Cl. X.R. 23 6-019

Images