Thermally actuated valve assembly

An improved heat exchanger, and flow control valve assembly associated with a heat exchanger, of the type wherein the temperature responsive flow control valve is integrated with the heat exchanger the valve assembly is well suited for mounting at the discharge port of the heat exchanger, without relying on rigid interaction with the inside wall of the discharge header or the tube ends in the discharge header. In this manner, the same basic valve assembly can be utilized in a variety of heat exchanger headers, merely by adapting the connection between the end of the valve assembly closest to the discharge port, and the housing or related structure of the heat exchanger at the discharge port. To the extent a relatively standard size valve assembly is to be used with heat exchangers having discharge conduits of different cross sectional area or shape, a baffle member can be placed around the valve assembly before insertion into the header.

BACKGROUND OF THE INVENTION

The present invention relates to heat exchangers, especially radiators, and to flow control valves associated therewith.

Heat exchangers have been employed in a variety of sizes, shapes, and fluid handling capabilities, for many years. Many fluid handling systems and processes in which heat is generated, require that the fluid be maintained within upper and lower limits of temperature, either for efficient operation of the process, or for safety reasons.

In typical heat exchange systems of this kind, a temperature sensitive control valve is associated with the main process, which in one state bypasses the heat exchanger and in another state diverts all or some of the process fluid through the heat exchanger, before returning the flow to the process. U.S. Pat. No. 3,440,833 discloses a modified heat exchange system, in which the flow control valve is integrated with the heat exchanger itself. The valve is situated in the outlet conduit of the heat exchanger, for sensing the temperature of the out flowing fluid and, in response to that temperature, taking either one position which permits flow through some of the heat exchange elements while blocking flow through the others, or another position that permits flow through all the heat exchange elements.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved heat exchanger, and flow control valve assembly associated with a heat exchanger, of the type wherein the temperature responsive flow control valve is integrated with the heat exchanger.

One of the improvements that is achievable with the present invention, is that the valve assembly is well suited for mounting at the discharge port of the heat exchanger, without relying on rigid interaction with the inside wall of the discharge header or the tube ends in the discharge header. In this manner, the same basic valve assembly can be utilized in a variety of heat exchanger headers, merely by adapting the connection between the end of the valve assembly closest to the discharge port, and the housing or related structure of the heat exchanger at the discharge port. In essence, the valve assembly is cantilevered into the discharge header, from the discharge port.

This capability not only reduces the cost and complexity of supporting the valve within the discharge header but, as previously indicated, avoids the further cost of providing for the customized rigid engagement of structure in the discharge header with structure on the valve assembly.

Moreover, the valve assembly can be fabricated and assembled entirely outside the heat exchanger, secured outside the heat exchanger to an end-fitting or the like defining the discharge port, and while attached to the end-fitting, easily inserted into to the discharge header. Upon external attachment of the fitting to the header or associated heat exchanger frame, the valve assembly is fully secured in place, ready for operation.

To the extent a relatively standard size valve assembly is to be used with heat exchangers having discharge conduits of different cross sectional area or shape, a baffle member can be placed around the valve assembly before insertion into the header. A perfect seal is not required between the baffle and the heat exchanger conduit wall, inasmuch as the same type of fluid is on both sides of the baffle and the leakage flow area as compared with the total available flow, is usually insignificant.

According to a related aspect, the improvement is directed to a heat exchanger having an inlet header with associated inlet port for receiving fluid having a variable temperature and an outlet header with associated outlet port for discharging fluid at a controlled temperature. A plurality of heat exchange tubes have upstream ends fluidly connected to the inlet header and downstream ends fluidly connected to the outlet header, whereby fluid can flow from the inlet port, into the inlet header, through each tube where heat is transferred, thereby cooling the fluid, before flowing into the outlet header, and out of the outlet port. A thermally actuated valve assembly is rigidly attached to the discharge port of the outlet header and spans the downstream ends of a plurality the tubes adjacent the outlet port. The valve assembly has a valve body selectively movable between (i) one position permitting flow of fluid from some of the tubes adjacent the outlet port through the outlet header to the outlet port while blocking flow of fluid from all other tubes through the outlet header to the outlet port and (ii) another position permitting flow of fluid from all of the tubes through the outlet header to the outlet port.

The valve assembly preferably comprises an upper section having an upper, perforated sidewall spanning the downstream ends of the tubes adjacent the outlet port, a lower section having a lower, perforated sidewall spanning the downstream ends of at least one of the other tubes, an imperforate circumferential exterior wall intermediate the upper and lower sidewalls, confronting the conduit, and an internal annular shoulder defining a valve seat within the exterior wall. The thermally responsive wax actuator is situated longitudinally within the valve assembly and exposed to fluid discharged from the tubes adjacent the port into the outlet header through the perforated wall of the upper section of the valve assembly. The actuator has a housing including an annular external shoulder confronting the valve seat; whereby (i) at a first temperature of the fluid entering the header from the plurality of adjacent tubes in the header the external shoulder on the housing fluidly seals against the valve seat such that fluid from the tubes adjacent the outlet port flows through the upper section to the outlet port while flow of fluid from tubes below the valve seat is substantially blocked by the seated valve and the confrontation of said wall with the conduit and (ii) at a higher temperature the wax expands, thereby lifting the housing shoulder off the valve seat to permit fluid flow from tubes below the valve seat to the upper section of the valve assembly and through the outlet header to the outlet port.

The valve assembly may optionally include a stationary, imperforate baffle extending radially outwardly at the rigidly connected flanges and defining the radially outermost limits of the valve assembly, for closely following the internal cross section of the outlet header or conduit.

In another aspect, an embodiment is directed to a valve assembly for insertion into a conduit, comprising specially adapted upper and lower sections. The upper section includes a tubular nozzle defining a longitudinal flow axis, an upper flange formed at one end of the nozzle and extending transversely to the axis, a lower flange axially spaced from the upper flange and extending transversely to the axis, and a perforated side wall rigidly connected between the upper and lower flanges. The lower section has an upper flange located concentrically within and rigidly connected to the lower flange of the upper section, an end stop axially spaced from the upper flange of the lower section, a perforated sidewall rigidly connected between the upper and lower flanges of the lower section, and an internal annular shoulder defining a valve seat at the junction of the upper and lower sections. A thermally responsive wax actuator is situated longitudinally within the upper section of the valve assembly and has a housing including an annular external shoulder confronting the valve seat. The housing contains a thermal wax and the actuator has a piston projecting from within to a free end bearing on the end stop. The piston is axially movable in response to thermal expansion and contraction of the wax. A spring or the like in the upper section biases the housing against the valve seat. A stationary, imperforate baffle extends radially outwardly at the rigidly connected flanges and defines the radially outermost limits of the valve assembly.

The heat exchanger is herein described in a particular orientation, according to which “upper” and “lower” are used as terms of relative orientation. Another significance advantage of the present invention is that the operational effectiveness is independent of orientation of the heat exchanger. Therefore, the terms “upper” and “lower” cannot be understood as literal limitations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows a heat exchanger1having a main frame or body10and an associated flow control valve100. The frame includes an inlet header12having an inlet port14at one end and a plug16at the other end. Similarly, an outlet header18is provided on the opposite side of the body10, with outlet port20and plug22at the other end. A multiplicity of heat exchanger tubes24A-24M are vertically spaced apart and have interleaved fins or the like exposed to air or other heat exchange medium. Process fluid in the inlet header12enters each tube though the inlet ends26and exits each tube through the outlet ends28into the outlet header18. The inlet flow30is shown entering the header12along the header longitudinal axis32. This flow is of variable temperature according to the heat generated in the main process (not shown). The inlet fluid travels through the tubes26, transferring heat through the fins to the heat exchange medium, before entering the outlet header18at a reduced temperature.

In this type of heat exchanger, all or some of the process fluid flows in direction30into the inlet header12, and at least some of that fluid continuously flows in the direction38until it reaches the tube ends28whereupon it continues to flow out of the heat exchanger as indicated at40. In this particular heat exchanger, such continuous flow in direction38occurs only in tubes24A and24B. This is a result of the valve100blocking flow of the fluid46in the outlet header18below the flow barrier associated with the valve, in this instance at the level of tube24C. Under these circumstances, fluid in tubes24C-24M, and in the inlet and outlet headers below tube24C, remains substantially stagnant.

Only when the heat exchange capacity of tubes24A and B is insufficient to maintain the fluid temperature below the threshold, as sensed by the thermal sensing element of the valve100, will the valve open to provide a fluid path from the previously isolated volume46in the outlet header18, through the valve and axially44out of the outlet port20. In the illustrated embodiment, the outlet fitting42defining the outlet port20, also secures the valve assembly100within the outlet header18.

FIG. 2shows the details of the valve assembly100in the outlet header18under cold conditions, whereby flow remains continuous through tubes24A and24B only. The valve assembly includes an upper section102spanning the downstream ends of the plurality of “continuous flow” tubes24A,24B adjacent the outlet port, having an upper flange104extending transversely to the axis and defining an internal axial flow path106, as well as a lower flange108axially spaced from the upper flange and extending transversely to the axis. A perforated side wall110is rigidly connected between or integrally formed with the upper and lower flanges.

A lower section112of the valve assembly has an upper flange114located concentrically within and rigidly connected to the lower flange108of the upper section, an end stop116axially spaced from the upper flange of the lower section, and a perforated side wall118rigidly connected between or integrally formed with the upper and lower flanges116. An internal shoulder120defining a valve seat is formed at the junction of the upper and lower sections102,112.

A thermally responsive wax actuator122is situated longitudinally within the upper section102and exposed to the fluid discharged from the tubes24A,24B into the outlet header and passing through the perforated wall110of the upper section of the valve assembly. This fluid continuously flows through opening106for discharge at40. The actuator has a housing124including an annular external shoulder126confronting the valve seat120. The housing contains a thermal wax128which acts directly or through a diaphragm and stem arrangement129or the like (in a conventional manner) on an actuating piston130. The piston has one end within the housing and another, free end132projecting from the housing and bearing on the stop116. A coil spring134or other resilient means known in this or related fields of technology, is provided in the upper section102, for biasing the housing against the valve seat120. The spring, housing, and piston are in essence aligned between the spring seat formed in the flange140and the piston seat formed in the end stop116, with the spring rate sufficient to maintain the shoulder126of the housing, against the valve seat120, during all variations of fluid temperature exiting the tubes24A,24B, up to a threshold temperature.

At the threshold temperature, the valve opens, as shown inFIG. 3. Depending on the particular composition of the wax128, a temperature exceeding the threshold can produce a rapid change in wax volume, or the change in volume can be proportional to the change in temperature above the threshold. In any event, upon reaching the threshold temperature, the wax expands but, due to the hard stop of the piston132, the only available movement is against the spring134whereby the shoulder126on the housing will lift from the valve seat120. As a result of the perforated side wall118of the lower section of the valve assembly, relatively cool fluid46in the outlet header18will immediately flow pass the open valve seat, mix with the excessively hot fluid exiting from tubes24A and24B, thereby quickly reducing the temperature of the outflow40. Thereafter, flow resumes through all of the tubes24A-24M and the maximum heat exchange effectiveness will be sustained until the temperature adjacent the outlet port drops to a second threshold. The decreasing fluid temperature causes the wax to contract, displacing the housing sufficiently to seal at the valve seat120.

It should be appreciated that the operational effectiveness of the heat exchanger depends on maintaining no, or relatively low, flow between the valve assembly100and the inside wall of the outlet header18. The header18preferably has a circular cross section, and the valve assembly100, having a substantially cylindrical shape, would likewise have a substantially circular cross section. Under these circumstances, the leakage flowing from the lower portion46of the header18into the upper section102of the valve assembly100and mixing with the fluid from tubes24A and24B, would be of acceptable levels. This is preferably achieved by a short, substantially cylindrical portion of the outer side wall of the valve assembly100having a diameter that is approximately equal to the inner diameter of the tubular outlet conduit18. If this side wall on the valve assembly is intermediate the perforated side wall110of the upper section102and the perforated side wall118of the lower section112, a baffle is formed that blocks flow into the upper section. Only if the housing shoulder126is lifted off the valve seat120, will fluid in the lower volume46of the header18pass up into the upper section of the valve assembly for discharge at40.

This can be implemented in conjunction with facilitating fabrication of the valve assembly, by having flange108initially be a cylindrical extension of the upper section102, for receiving the upper flange114of the lower section112after the actuator122has been seated in the upper section102. Upon radially inward crimping, the extension forms the flange140whereby the upper flange114of the lower section is captured. Moreover, the lower flange108of the upper section can have a slightly larger diameter than the remainder of the upper section, forming a shoulder136or the like. The increased diameter of the cylindrical portion142of the flange thus provides the baffle142for restricting flow along the periphery of the valve assembly.

It should be appreciated, however, that the valve assembly100can readily be utilized in a heat exchanger having a outlet header18of a different diameter, or of a cross section that is non-circular. Under these circumstances, either an annular space, or a space of varying dimensions, would be created between a substantial circular side wall of the valve assembly and the adjacent side wall of the header18. In essence, the header is a conduit within which the valve assembly must be coaxially mounted. A distinct baffle can then be located, for example on shoulder136, having a shape that will substantially fully span the space between the valve assembly and the surrounding conduit wall, regardless of shape. The baffle can thus have a circular inner edge, for resting on the shoulder136, and an outer edge of a shape that will conform with the cross sectional shape of the conduit inner wall. One such distinct, stationary, imperforate baffle extending radially outwardly at the rigidly connected flanges and defining the radially outermost limits of the valve assembly, will be described with respect toFIGS. 6.

The valve assembly100is preferably anchored in the vicinity of the outlet port20, to project longitudinally into the outlet header18. This can be accomplished by securing the valve assembly to a fitting42, and securing the fitting42via bolts or the like48, to threaded bores50or the like in the conduit18and/or the frame10,52. Preferably, the upper section102of the valve assembly includes a nozzle or the like138that is externally threaded for engagement with internal threads in the bore of fitting42. The portion of the fitting42that enters the header conduit for engagement with the nozzle138, has an external groove54for receiving an O-ring or the like56to prevent leakage flow out of the heat exchanger, instead of through the outlet port106.

The embodiment of the valve assembly200show inFIGS. 4 and 5is very similar to that shown inFIG. 3, except that a groove202is formed on the interior of the rim portion204of the lower flange206in the upper section208, for receiving a snap ring210to secure the flange212of the lower section214of the valve assembly, thereby encapsulating the actuator216in relation to the valve seat218.

FIG. 6Ais a detailed view of the valve100ofFIG. 1, shown in the hot flow condition ofFIG. 3, but with a distinct baffle member144carried on shoulder136of the upper section102of the valve.FIG. 6Bis a further detailed view of the how the baffle144is staked in position on the valve, to resist the upward hydraulic pressure in the cold condition associated withFIG. 2. As described above, the radially outer surface of the baffle144need not be circular, but could be oval or polygonal, to closely match the interior wall of the conduit.

In the illustrated embodiment, before installation the baffle is slipped over the sidewalls110of the upper section of the valve, to the annular ledge or shoulder136formed by the annular solid material defining the external cylindrical wall142. The valve may have a plurality of spaced apart sidewalls110, and preferably three equilaterally spaced sidewalls will be pinched with a tool in a known manner to deform the material as shown at146, including the formation of a ridge or the like148immediately above, and preferably bearing on the upper surface of the baffle144. The lower shoulder136prevents downward movement of the baffle, and the ridge148prevents upward movement of the baffle, when subjected to fluid pressure within the heat exchanger.

FIG. 6Bshows that the portion of the upper section of the valve forming the wall142is, in essence, a ring142′ that circumscribes the axis of the valve. Similarly, the baffle144is in essence a ring144′ that circumscribes the axis of the valve, while resting on the shoulder136, which also circumscribes the valve axis as indicated at136′. Preferably, the baffle144is situated laterally of the housing124of the thermal actuator, with the support shoulder136and associated cylindrical wall142being situated laterally of the seating surface120and the sealing surface126, which ultimately control whether the valve is open or closed.

It should be appreciated that other techniques for retaining the baffle144in place may also be used, such as by pinning above the baffle, in the vicinity of ridge148, or through the baffle.