WO2015002855A1

WO2015002855A1 - Heated fluid delivery with thermal management

Info

Publication number: WO2015002855A1
Application number: PCT/US2014/044782
Authority: WO
Inventors: William H. Glime
Original assignee: Swagelok Company
Priority date: 2013-07-03
Filing date: 2014-06-30
Publication date: 2015-01-08

Abstract

A valve and actuator assembly has a valve comprising a valve member and a valve seat, an actuator that opens the valve by moving the valve member into contact with the valve seat and closes the valve by moving the valve member away from the valve seat, and a temperature compensating element disposed between the actuator and the valve member. The temperature compensating element may comprise a material having a CTE that is lower than the CTE of the valve seat and the actuator stem.

Description

HEATED FLUID DELIVERY WITH THERMAL MANAGEMENT

RELATED APPLICATION

[0001] The present application claims the benefit of United States Provisional Patent Application serial no. 61/842,436 filed on July 3, 2013, for HEATED FLUID DELIVERY WITH THERMAL MANAGEMENT, the entire disclosure of which is fully incorporated herein by reference.

TECHNICAL FIELD OF THE DISCLOSURE

[0002] The inventions relate to heated fluid delivery arrangements, and more particularly to flow control devices that are adapted to control fluid delivery including liquid or gaseous fluid.

BACKGROUND

[0003] Valves are well known for use as flow control devices for gas and liquid fluid delivery. Valves include an associated actuator that opens and closes the valve on command. Actuators may be manually operated or automatically operated such as, for example, a pneumatic, electromechanical or hydraulic actuator. In the semiconductor industry as well as others, delivery of process fluids and chemicals during various processing operations is controlled using valves, for example, high purity valves. Some of the more common applications for valves are chemical vapor deposition (CVD) and atomic layer deposition (ALD). Other flow control devices that pertain to the present disclosure include but are not limited to regulators, filters, valves that use linear actuators such as bellows valves and diaphragm valves for example, surface mount valves and so on.

[0004] Often, process fluids and chemicals must be heated to a liquid or gaseous state for use in a particular application. In such cases, there is typically a temperature range or window that must be maintained for the process fluid, because cold spots or reduced temperature can produce undesirable condensation, while overheating can cause degradation of the process fluid or chemical. [0005] It is also known to deliver a process fluid or chemical to and from a flow control device through a substrate, manifold or other fluid delivery device or arrangement wherein the delivery device is heated to condition the process fluid to a desired temperature. The fluid delivery device provides a flow path for the process fluid to and from the various flow control devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Fig. 1 illustrates an exemplary thermal map for a traditional valve and actuator assembly,

[0007] Fig. 2 is an exemplary valve and actuator assembly on a heated substrate, in isometric,

[0008] Fig. 3 is a longitudinal cross-section of the assembly of Fig. 2,

[0009] Fig. 4 is an alternative embodiment of the assembly of Fig. 3,

[0010] Fig. 5 is an alternative embodiment of the assembly of Fig. 3,

[0011] Fig. 6 is an embodiment with a manually operated actuator,

[0012] Fig. 7 is another embodiment of the assembly of Fig. 1 with a heat distributor,

[0013] Fig. 8 is a longitudinal cross-section of the assembly of Fig. 7.

SUMMARY

[0014] A first inventive concept presented herein provides apparatus and methods for thermal management of a fluid delivery system for a heated process fluid or chemical (collectively hereafter the "process fluid".) In a first example of thermal management, a fluid flow control device that may be used for controlling flow of the heated process fluid, be it a liquid or gas, is operational over a prescribed temperature range for the process fluid without adverse effects on the flow capacity (Cv) of the flow control device. Stated another way, a first thermal management concept provides a flow control device that exhibits improved flow capacity uniformity across a prescribed operational temperature range of the process fluid. In an embodiment, a flow control device may be realized in the form of a valve and actuator assembly that includes a valve member, a valve seat, and a temperature compensating element disposed between the actuator and the valve member. The temperature compensating element compensates for a coefficient of thermal expansion (also referred to hereinafter as "CTE") mismatch between the actuator and the valve seat. Optionally, the temperature compensating element may also provide temperature isolation benefits between the actuator and the valve. Additional embodiments of this concept are presented herein.

[0015] A second inventive concept presented herein is to provide apparatus and methods for thermal management of a fluid delivery system for a heated process fluid or chemical with improved heat distribution within a flow control device for the process fluid. In an embodiment, a flow control device may be realized in the form of a valve that includes a valve member, a valve seat and a thermal distributor. The thermal distributor may be used to provide improved heat distribution within the valve. Additional embodiments of this concept are presented herein.

[0016] A third inventive concept presented herein is to provide apparatus and methods for thermal management of a fluid delivery system for a heated process fluid or chemical with improved flow capacity uniformity and also improved heat distribution. In an embodiment, a flow control device may be realized in the form of a valve and actuator assembly that includes a valve member, a valve seat, a temperature compensating element and a thermal distributor. The temperature compensating element compensates for a coefficient of thermal expansion (CTE) mismatch between the actuator and the valve seat, while the thermal distributor may be used to provide improved heat distribution within the valve. Optionally, the temperature compensating element may also provide temperature isolation benefits between the actuator and the valve. Additional embodiments of this concept are presented herein.

[0017] In an alternative embodiment of the first inventive concept herein, a flow control device may be realized in the form of a valve and actuator assembly that includes a valve member, a valve seat, and a temperature compensating element disposed between the actuator and the valve member. The temperature compensating element compensates for a coefficient of thermal expansion (CTE) mismatch between the actuator and the valve seat. The actuator may comprise a material having a first CTE, the valve seat may comprise a material with a second CTE, and the temperature compensating element may comprise a material having a third CTE, wherein the third CTE is lower than the first CTE and the second CTE. The second CTE and the first CTE may optionally be different or the same. Optionally, the temperature compensating element may also provide temperature isolation benefits between the actuator and the valve. Additional embodiments of this concept are presented herein.

[0018] A fourth inventive concept presented herein is to provide apparatus and methods for thermal management of a fluid delivery system for a heated process fluid or chemical to produce improved performance in manually actuated valves. In an embodiment, a flow control device may be realized in the form of a valve and a manual actuator assembly that includes a valve member, a valve seat, and a temperature compensating element disposed between the manual actuator and the valve member. The temperature compensating element compensates for a coefficient of thermal expansion (CTE) mismatch between the manual actuator and the valve seat to reduce or eliminate damage or distortion to the valve seat caused by thermal expansion of the valve seat. Additional embodiments of this concept are presented herein.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0019] With reference to Fig. 1 and the teachings according to the present disclosure, a thermal map was generated for a traditional valve and actuator assembly that is mounted on a heated substrate. In this example, the actuator A is mounted on top of a diaphragm valve B. The valve B is surface mounted on a heated substrate C. The substrate C is heated so as to maintain the process fluid within a desired or prescribed temperature range so that the process fluid, for example, maintains a liquid or gas state for delivery through the valve B to a downstream process location (not shown.) In this example, the substrate C may be heated to 150 °C. It will be noted that there is a significant temperature drop or gradient between the substrate C and the valve B. The valve B includes a valve body which might only be at a temperature of approximately 1 10 °C for this example.

[0020] The temperature gradient across the interface between the valve B and the substrate C can be the result of a number of factors. For example, the valve body which supports a diaphragm D often is made of a low thermal conductivity material such as stainless steel, as is the substrate C. The surface mount technology also does not typically provide sufficient contact at the interface between the valve body and the substrate C for effective transfer of heat across the interface. Moreover, the actuator A commonly has aluminum parts, particularly an aluminum housing. Aluminum has a much higher thermal conductivity than stainless steel. The actuator A therefore tends to act as a heat sink and pull heat from the diaphragm valve B. This heat loss may occur through the actuator housing contact with the valve body, and may also occur as a result of contact between the valve diaphragm D and the actuator button E. In some actuator/valve designs the actuator stem may directly contact the diaphragm D rather than through use of a button. Either configuration can result in the diaphragm D being a "cold spot" for the process fluid that flows through the diaphragm valve B. Note from Fig. 1 that the diaphragm D is exposed to a temperature of only about 60 °C on the non-wetted side (the actuator side) of the diaphragm. This presents a reduced temperature zone in the region of the valve seat (the valve seat is just below the diaphragm D on the wetted side of the diaphragm D~see Fig. 3 for example) which is an undesirable result. Such lower temperature zones or cold spots can create undesired condensation of the process fluid, particularly in the region of the valve seat. There also can be a significant temperature gradient within the valve body itself, from the lower region near the heated substrate to the upper region at the diaphragm D and valve seat.

[0021] Another problem identified herein with a fluid delivery system for a heated process liquid or chemical is that the valve seat, which operates with the diaphragm D to open and close flow of the process fluid through the valve B, is commonly made of non-metallic polymer or elastomeric material, such as PFA. Polymer materials typically have a very high coefficient of thermal expansion (CTE) compared with metals such as stainless steel and aluminum. For example, PFA has a CTE of about 130xl0^"6 /°C whereas metals such as aluminum and stainless steel have CTEs of less than 30x10^"6 /°C. The effect of this CTE mismatch between the actuator and the valve seat is that when the valve is heated, the valve seat grows to a greater extent due to thermal expansion than the actuator and the diaphragm. This can reduce the gap between the valve seat and the diaphragm when the valve is in the open position, thereby reducing flow capacity (Cv) of the valve.

[0022] While the inventions are described herein with detailed description of the exemplary embodiments, the inventions will find application in many other embodiments. For example, the exemplary embodiments illustrate a diaphragm valve and a pneumatic actuator with surface mount technology used to interface the valve with a heated substrate. However, the inventions may readily be adapted for use with other flow control devices, including but not limited to bellows valves, regulators, filters, and other components that are operated with linear actuation. Also, the inventions are not limited to use with process chemicals but may be used with any liquids, gases or other fluids that are compatible with the particular flow control device being used. The inventions may also be used with manual actuators and automatic actuators such as pneumatic, hydraulic or electromechanical actuators. The inventions may also be used with substrate interfaces other than surface mount technology.

[0023] With reference to an embodiment shown in Figs. 2 and 3, a valve and actuator assembly 10 is shown and may include a diaphragm valve 12 or other flow control device and an actuator 14. The basic design and operation of the valve and actuator assembly 10 may be but need not be the same as the DE series valve and actuator products available commercially from Swagelok Company, Solon, Ohio, but modified as described herein. The actuator 14 may be mounted on top of the valve 12, and may be, for example, a pneumatic linear actuator. By linear actuator is meant that the actuator imparts a force on a valve member to operate the valve 12 using a linear displacement of an actuator stem or other actuator element. The valve 12 may be disposed on a fluid delivery device 16. The fluid delivery device 16 may be a substrate or manifold or other suitable component that includes an inlet flow path and an outlet flow path for a process fluid, for example a process chemical, for the valve 12. Although this embodiment illustrates a valve 12 that is disposed on the substrate 16 with a surface mount configuration, such is not required, and other mounting techniques or interfaces between the substrate 16 and the valve 12 may alternatively be used. Surface mount technology is well known in the art. A heater 18 may be used to apply heat to the substrate 16 so as to condition the process fluid witin a desired or prescribed temperature range based on the downstream use for the process fluid.

[0024] The valve 12 includes a valve body 12a having an inlet flow passage 20 and an outlet flow passage 22 that communicate with the inlet and outlet flow paths respectively in the below-mounted substrate 18. The valve may also be alternatively operated with reverse flow. The flow passages 20, 22 open to a valve chamber 24 that is sealed by a valve member, for example, an overlaying diaphragm 26. An annular valve seat 28 surrounds the inlet flow passage 20. The valve 12 is closed to fluid flow by the diaphragm 26 being moved into contact with the valve seat 28, and is opened to fluid flow by the diaphragm 26 moving away from the valve seat 28. The diaphragm 26 often may be a springless domed diaphragm having a natural unstressed state for the open position of the valve 12. Or alternatively the diaphragm having the ability to self-recover a state that defines the open position of the valve 12. Or alternatively, the diaphragm 26 may be a tied diaphragm that is joined to the actuator so that the actuator is able to deflect the diaphragm in both directions to open and close the valve 12.

[0025] The actuator 14 may be an automatic actuator, for example a pneumatic actuator, or alternatively may be a hydraulic actuator, electromechanical actuator and so on. Another alternative is that the actuator 14 may be a manual actuator as described below. For a conventional pneumatic actuator 14, the actuator has an actuator housing 14a that contains a piston 30 that is used to open and close the valve 12 by imparting linear movement to an actuator stem 32 against an upper non-wetted surface of the diaphragm 26. An optional button 34 may be used in some cases that directly contacts the non-wetted side of the diaphragm 26. A spring 36 biases the actuator 14 to a closed position (referred to in the art as a normally closed valve), with pneumatic pressure 38 being applied to a pressure chamber 40 and used to lift the piston 30 (as viewed in the drawings) so that the diaphragm relaxes away from the valve seat 28 to open the valve 12. Alternatively, a normally open actuator/valve configuration may be used. Also alternatively more than one piston may be used.

[0026] The actuator 14 in Figs. 2 and 3 is modified from known actuator designs by preferably shortening the actuator stem 32 (to maintain preferably the envelope dimension of the actuator) and inserting a temperature compensating element 42 in between the actuator stem 32 and the button 34. Alternatively, the optional button may be omitted. In Fig. 3 the temperature compensating element 42 is in the form of a cylindrical rod, but other geometric shapes may be used, for example, a sphere or ball.

[0027] The valve seat 28 oftentimes comprises a polymer material that has a higher coefficient of thermal expansion as compared to other materials used in the valve and actuator assembly 10. For example, the valve seat 28 may comprise PFA or PTFE (e.g. TEFLON^®) having a CTE of about 130xl0^"6 °C^"' ). As shown in the chart below, relative to stainless steel (e.g. 316 SS) and aluminum (e.g. Al-6061), the valve seat 28 may have a much higher CTE:

[0028] When the temperature of the valve body and/or the process fluid increases, the valve seat 28 expands significantly more than the components in the actuator 14 (notably the piston and actuator housing may commonly be made of aluminum) and the valve 12 (commonly made of stainless steel). This temperature related growth of the valve seat 28 means that when the process fluid and the valve 12 are heated by the substrate 16, the gap between the valve seat 28 and the diaphragm 26 can be significantly reduced, resulting in a drop in Cv of the valve 12 at higher temperatures.

[0029] The temperature compensating element 42 is selected to comprise a material with a CTE that is less than the CTE of the valve seat 28 as well as less than the CTE of the actuator stem 32 and the optional button 34. With such an arrangement, the temperature compensating element 42 will exhibit less thermal expansion or growth with increasing temperature as compared to the valve seat 28 and the actuator housing 14a and so effectively the gap between the diaphragm 26 and the valve seat 28 will not change significantly so as not to affect the Cv of the valve 12. In other words, the lower thermal expansion component and the higher thermal expansion components are free to expand in parallel. The element 42 above the button (or alternatively the diaphragm directly) expands in parallel with the lower actuator cylinder and actuator stem, and the differential expansion is the product of the height of the element 42 and the difference in CTE between element 42 and actuator cylinder. If the element 42 were of the same material as the actuator cylinder there would be no change in the position of the button that controls the diaphragm height (or the diaphragm itself) because the element 42 would expand the same amount as the actuator cylinder. If the element 42 is of a material such that is does not expand at all then the position of the button (or the diaphragm alternatively) in contact with the element 42 would change by an amount equal to the height of the element 42 and the CTE of the cylinder. The shape of the element 42 is not critical (other than its effective height). As examples, the temperature compensating element 42 may comprise INVAR or Zirconia or ZERODUR to name just a few examples.

[0030] With reference to Fig. 4, another embodiment of a valve and actuator assembly 10' may but need not share many of the same components as the embodiment of Figs. 2 and 3 and like reference numerals are used. Note in this example the actuator 14 uses two pistons, an upper piston 44 and a lower piston 46. The difference in the two embodiments is that in Fig. 4, the lower piston 46 replaces the piston 30 and the temperature compensating element 42, so that the lower piston 46 itself is the temperature compensating element that is disposed between the valve seat 28 and the actuator 14. For example, the lower piston 46 may be made of a material having a lower CTE than the valve seat 28 or the upper piston 44 or the actuator housing 14a, for example one of the materials noted above for the temperature compensating element 42. With such an arrangement, the temperature compensating element 46 will exhibit less thermal expansion or growth with increasing temperature as compared to the valve seat 28 and the actuator housing 14a and so effectively the gap between the diaphragm 26 and the valve seat 28 will not change significantly to affect the Cv of the valve 12.

[0031] Fig. 5 is another embodiment that is similar in most respects to the Fig. 4 embodiment except that the pistons 48 and 50 may be conventional pistons, made of aluminum, for example. As an alternative to a cylindrical rod as in the embodiment of Figs. 2 and 3 herein, the temperature compensating element 52 may be realized in the form of a sphere or ball that is disposed between the actuator stem 32 and the optional button 34 or directly in contact with the diaphragm 26. The ball 52 may be made of a material having a lower CTE than the valve seat 28 or the lower piston 50 or the actuator housing 14a, for example one of the materials noted above for the temperature compensating element 42. With such an arrangement, the temperature compensating element 52 will exhibit less thermal expansion or growth with increasing temperature as compared to the valve seat 28 and the actuator housing 14a and so effectively the gap between the diaphragm 26 and the valve seat 28 will not change significantly to affect the Cv of the valve 12.

[0032] With reference to Fig. 6, in an alternative embodiment to Figs. 2 and 3, the automatic actuator 14 may be replaced with a manual actuator 54. A distinction between a direct drive manual actuator and a spring biased automatic or manual actuator is that the direct drive manual actuator stem in the valve closed position is axially fixed. This is because actuation involves rotating the handle that through a threaded coupling with the actuator stem causes axial displacement of the actuator stem. When the valve undergoes increasing temperature, the valve stem cannot move axially, and so the higher CTE valve seat can become highly compressed to the point of being damaged and deformed. When the valve is then cooled down, the damaged valve seat can lose compressive contact with the valve member. By positioning the temperature compensating element between, for example, the actuator and the valve member, this damage to the valve seat can be reduced or eliminated due to the CTE mismatch between the temperature compensating element 42 and the actuator.

[0033] A direct drive manual actuator 54 commonly includes a handle 56 that is manually turned to open and close the valve. Manually rotating the handle 56 causes linear displacement of the actuator stem 58, by operation of a threaded coupling 59, which moves the diaphragm 26 to open and close the valve. The assembly further includes a temperature compensating element 42 which may be, for example, an INVAR cylindrical rod as in the embodiment of Figs. 2 and 3. Without the temperature compensating element 42, when the valve is heated the valve seat 28 will expand and can become deformed so that when the valve is then cooled the valve seat can lose contact with the diaphragm because the manual valve cannot self adjust. By including the temperature compensating element 42, the thermal expansion and growth of the valve seat 28 is compensated because the temperature compensating element 42 does not thermally expand or grow to the same extent as the actuator stem 58, so that the valve seat 28 will not become deformed when the valve is heated in the closed position. The valve will therefore remain closed after the valve temperature is reduced.

[0034] As explained above and with reference again to Fig. 1, not only can there be a temperature gradient across the interface between the heated substrate C and the valve B, but within the valve itself there can be a temperature gradient from the portion of the valve body that is closest to the substrate and the portion of the valve body that is closest to the valve member D and the valve seat. The reduced temperature in the portion of the valve body near the valve member D and the valve seat is in part due to the heat sink effect of the actuator A and the low thermal conductivity of the material for the valve B (for example, stainless steel) as well as other possible factors.

[0035] With reference to Figs. 7 and 8, in an embodiment of the third inventive concept described above, a valve and actuator assembly 60 may include an actuator 62 and a valve 64. The actuator 62 and the valve 64 may be but need not be the same design as in the embodiment of Figs. 2 and 3, or other embodiments as described herein and alternatives thereof. A thermal or heat distributor 66 may be disposed about the valve body 68. The heat distributor 66 may be realized in the form of a shroud or cap that surrounds the valve body 68 and preferably is in intimate contact therewith to facilitate thermal or heat exchange between the valve body and the heat distributor. For example, the heat distributor may have a conforming shape to the exterior geometry of the valve body 68, as well as a lower portion of the actuator housing as needed. Fasteners such as bolts 70 may be used to mount the heat distributor 66 on the valve body, and the same fasteners 70 may be used to surface mount the valve and actuator assembly 60 onto a substrate (not shown). For ease of assembly the heat distributor 66 may optionally be a split body or made of multiple pieces so that it can be installed onto a previously assembled valve and actuator assembly 60.

[0036] Preferably, the heat distributor 66 is made of a high thermal conductivity material, for example aluminum, that has a higher thermal conductivity than the valve body 68. An upper portion 72 of the heat distributor 66 also preferably extends up and around the valve body and a lower portion 74a of the actuator housing 74 so that the heat distributor 66 provides a more even heat distribution within the valve body 68, particularly around the valve seat 76 portion of the valve body 68.

[0037] To help retain this distributed heat in the valve region of the assembly, the actuator housing 74 may be provided with a reduced or necked-down wall thickness 74b near the region of the optional button 78 or the valve member 80 (for example, a diaphragm) and the valve seat 76. This reduced wall thickness portion 74b acts as a thermal choke to reduce heat conduction up into the actuator 62. Additional thermal isolation of the valve 64 may be provided using a temperature compensating element 82 as described in other embodiments herein. In an embodiment, the temperature compensating element 82 may be realized as a ball of low thermal conductivity, for example, made of INVAR, Zirconia or ZERODUR or other suitable material. The temperature compensating element 82 therefore acts as a thermal isolator or insulator to reduce heat transfer from the valve member 80 to the actuator stem 84. In cases where the valve seat 76 has a high CTE, the temperature compensating element 82 also provides the benefit of maintaining a consistent Cv for the valve as described hereinabove because the temperature compensating element 82 may be made of a lower CTE and disposed between the actuator stem 84 and the valve member 80 (see the description as to the embodiments of Fig. 5 for example).

[0038] Thermal management as taught herein for a flow control device that controls flow of a heated process fluid, therefore, may be used to provide a Cv that is more uniform across a desired or prescribed temperature range than can be achieved without thermal management; and may be used to provide a more uniform heat distribution or profile within the flow control device than can be achieved without thermal management; or the two concepts may be used together with the same flow control device to realize both benefits.

[0039] It is intended that the scope of the inventions not be limited to the particular embodiments disclosed for carrying out the inventions, but that the inventions will include all embodiments falling within the scope of the appended claims.

Claims

I Claim:

1. A fluid delivery arrangement, comprising: a valve comprising a valve member and a valve seat, an actuator that opens said valve by moving said valve member into contact with said valve seat and closes said valve by moving said valve member away from said valve seat, a manifold that provides a fluid path for fluid into and out of said valve, said manifold being adapted to be heated, a temperature compensating element disposed between said actuator and said valve member, said element compensating for a CTE mismatch between said actuator and said valve seat.

2. The arrangement of claim 1 wherein said valve comprises a diaphragm valve.

3. The arrangement of claim 2 wherein said actuator comprises a pneumatic actuator or a manual actuator.

4. The arrangement of claim 1 or 2 wherein said valve seat comprises a polymer or other non-metal material.

5. The arrangement of claim 1 wherein said actuator comprises an aluminum housing, said valve comprises a stainless steel valve body, said valve member comprises a stainless steel diaphragm, and said valve seat comprises a non-metal material such as a polymer.

6. The arrangement of claim 1 or 5 wherein said element comprises a material with a CTE (xlO^"6 °C^"' ) that is less than approximately 10.

7. The arrangement of claim 6 wherein said valve seat comprises a material with a CTE greater than approximately 50.

8. The arrangement of claim 7 wherein said actuator comprises a material with a CTE greater than approximately 25.

9. A valve, comprising: a valve body comprising a flow path for fluid from an inlet to an outlet, a valve member disposed in said valve body and that is adapted to be moved between a first position and a second position, a valve seat that cooperates with said valve member to open and close the valve when said valve member is in said first and second positions respectively, a thermal distributor that is disposed on said valve body and conducts heat to a valve seat portion of the valve.

10. The valve of claim 9 wherein said thermal distributor comprises a material with a thermal conductivity (Watts/meter Kelvin) greater than approximately 100 and said valve body comprises a material with a thermal conductivity less than 25.

1 1. The valve of claim 9 in combination with an actuator that opens the valve by moving said valve member into contact with said valve seat and closes the valve by moving said valve member away from said valve seat, a temperature compensating element disposed between said actuator and said valve member, said element providing a CTE mismatch between said actuator and said valve seat.

12. The valve of claim 9 in combination with an actuator that opens the valve by moving said valve member into contact with said valve seat and closes the valve by moving said valve member away from said valve seat, and a heat barrier element disposed between said valve member and said actuator, said heat barrier element reducing heat transfer between said valve element and said actuator as compared to when said heat barrier element is not present.

13. The combination of claim 12 wherein said heat barrier element also provides a CTE mismatch between said actuator and said valve seat.

14. The arrangement of claim 1 or 1 1 wherein said temperature compensating element comprises INVAR.

15. The combination of claim 13 wherein said heat barrier element comprises Zirconia or ZERODUR.

16. A valve and actuator assembly, comprising: a valve comprising a valve member and a valve seat, an actuator that opens said valve by moving said valve member into contact with said valve seat and closes said valve by moving said valve member away from said valve seat, a temperature compensating element disposed between said actuator and said valve member.

17. The valve and actuator assembly of claim 16 wherein said temperature compensating element compensates for a CTE mismatch between said actuator and said valve seat.

18. The valve and actuator assembly of claim 17 wherein said temperature compensating element comprises a material having a CTE that is lower than a CTE of said actuator and said valve seat.

19. A valve and actuator assembly, comprising: a valve comprising a valve member and a valve seat, an actuator that opens said valve by moving said valve member into contact with said valve seat and closes said valve by moving said valve member away from said valve seat, a temperature compensating element disposed between said actuator and said valve member, said actuator comprising a material having a first CTE, said valve seat comprising a material with a second CTE, and said element comprising a material having a third CTE, wherein said third CTE is lower than said first CTE and said second CTE.

20. The assembly of claim 19 wherein said first CTE and said second CTE are the same as each other or alternatively are different from each other.