Expansion valve for a heat exchanger application

Abstract

The present invention pertains to an expansion valve for a closed-circuit heat exchanger application. The valve comprises two ports, a valve opening, a valve seat with a closing edge and a valve element with a closing portion for closing the valve opening. According to the invention, the valve element comprises at least one recessed portion functioning as a bleed hole, that is provided with a circular cross section.

Description

[0001] The present invention pertains to an expansion valve for a closed-circuit heat exchanger application. The valve comprises two ports, a valve opening, a valve seat with a closing edge and a valve element with a closing portion for closing the valve opening. According to the invention, the valve element comprises at least one recessed portion functioning as a bleed hole, that is provided with a circular cross section.

[0002] Expansion valves in heat exchanger application are used for controlling the flow of the heat exchanger fluid across the application. Such valves may typically require bleed holes for allowing gradual pressure equalization at a given bleed rate across the two ports of the valve even in the closed position of the valve. The bleed holes make it possible to utilize smaller compressors with relatively low starting torques. These compressors are not capable of starting up in conditions with excessive pressure differences across the compressor. Such conditions with excessive pressure differences across the compressor may occur in particular in vapour compression refrigeration systems and if the expansion valve does not allow for some fluid leakage and a corresponding pressure equalization.

[0003] In order to ensure a well-defined bleed rate of the closed valve, the recessed portion has to be shaped and dimensioned such as to ensure a well-defined fluid flow across it. As the recessed portion is typically small in size, very small variations of the recessed portion's dimensions and / or positioning may result in unallowable fluctuations of the fluid flow across the recessed portion and correspondingly unallowable fluctuations of the bleed rate.

[0004] The aim of the present invention is to provide an improved expansion valve which overcomes this problem, and which facilitates a steady and well-defined bleed rate in the closed state of the valve.

[0005] This aim is achieved by an expansion valve according to claim 1. Advantageous embodiments of the invention are subject to the dependent claim.

[0006] According to claim 1, an expansion valve for a closed-circuit heat exchanger application is provided. The valve comprises two ports, a valve opening, a valve seat with a closing edge and a valve element with a closing portion for closing the valve opening. The two ports may be an inlet and an outlet port for flowing a refrigerant fluid through the valve. The valve opening, the valve seat and the valve element may be provided within the valve and / or along the fluid flow path inside the valve.

[0007] According to the invention, the valve element comprises at least one recessed portion functioning as a bleed hole, that is provided with a circular cross section. The recessed portion may be provided only at the radial position of the closing edge. This means that portions adjacent to the recessed portion are protruding relative to the recessed portion.

[0008] The positioning of the recessed portion on the valve element makes it possible to manufacture the recessed portion as part of the same manufacturing step, in which the entire valve element is manufactured. Highly precise manufacturing methods can be easily applied for providing the recessed portion, thereby ensuring the desired precise and stable characteristics of the bleed rate. The presence of the recessed portion ensures that even in the closed position of the valve some fluid flow may occur across the recessed portion, ensuring the desired bleed rate at the expansion valve of the heat exchanger application.

[0009] The recessed portion with its precise dimensions makes it possible to manufacture expansion valves with substantially the same capacity curve. The variation of maximum capacity of valves of the same type is well controlled and not significantly affected by the tolerances of the bleed holes. However, the share of the bleed capacity of the maximum capacity is considerably affected by the tolerances of the bleed holes. This is of particular significance as the bleed part of the capacity of the valve cannot be controlled by movement of the valve element.

[0010] This means that the capacity curve may differ substantially between two valves of the same type if there are considerable tolerances on the bleed hole, as is the case in the prior art. For some valves, the bleed part of the valve capacity may represent eg. 15% of the maximum capacity whereas for other valves it may be around eg. 30% of the maximum capacity. Hence, if such valves with varying bleed rates are installed in heat exchanger applications, the way these applications behave i.e. their characteristics will differ considerably due to the different bleeding stemming from the tolerances of the bleed holes.

[0011] The radial position of the recessed portion and the closing edge may refer to a radial direction referenced to a central axis of the valve and in particular the valve element.

[0012] The recessed portion may be only provided at the radial position of the closing edge in the sense that it is provided on only a small fraction of the valve element in its radial direction. For example, the recessed portion may have only half of the radial extension of the valve element. Furthermore, the recessed portion may be spaced apart from the central and outer portions of the valve element. Hence, the recessed portion may not be present at or excluded from the central and outer portions of the valve element.

[0013] In a preferred embodiment of the invention, the recessed portion is formed integrally, preferably drilled, within the valve element. The drilling of the recessed portion may occur before or after the manufacturing of the remainder of the valve element. Preferably, the recessed portion may be first drilled after which the valve element may undergo a turning process. The circular cross section of the recessed portion may be the result of the drilling process used for creating the recessed portion.

[0014] In another preferred embodiment of the invention, the recessed portion is a blind bore. The blind bore may extend in the axial direction of the valve element, i.e. in the direction in which the valve element is movable for closing and opening the valve. Alternatively, the blind bore or recessed portion may extend at an angle of e.g. smaller than 45° relative to the axial direction of the valve element.

[0015] In another preferred embodiment of the invention, the recessed portion and the closing portion are formed integrally. Both these portions may be provided as part of the same component, i.e. the valve element. They may be arranged at the same radial position of the valve element.

[0016] In another preferred embodiment of the invention, the recessed portion is aligned with the closing edge in a radial direction of the valve and / or the recessed portion provides a fluid passage between the two ports in a closed position of the valve. The recessed portion and the closing edge may be aligned such that the closing edge divides the recessed portion into two parts of substantially equal cross-sectional area in a closed state of the valve. The two substantial equal parts correspond to an inlet and an outlet part of the recessed portion when functioning as a bleed hole.

[0017] In another preferred embodiment of the invention, the closing edge is fully circular. The closing edge may thus not contribute any bleeding function to the valve and renders the recessed portion the only portion of the valve, which provides such a bleeding function.

[0018] In another preferred embodiment of the invention, the recessed portion is oriented in an axial direction of the valve and / or offset in a radial direction from the centre of the valve element. The axial direction of the valve may correspond to the direction in which the valve element is movable for opening and closing the valve. The recessed portion may thus be easily formed using methods such as drilling or milling during the manufacturing of the valve element.

[0019] In another preferred embodiment of the invention, the diameter of the valve opening is in the range of 0,55 mm to 10 mm and / or the diameter of the recessed portion is in the range of 0,2 mm to 4 mm. Clearly, only matching diameters of the valve opening and the recessed portion can be selected, as a 4 mm recessed portion cannot be matched to a 0,55 mm valve opening.

[0020] In another preferred embodiment of the invention, the valve element comprises a radially central and preferably flat or flattened contact portion for contacting a rod. Alternatively, the valve element may be formed integrally with the rod. The recessed portion may be provided at a position between the rod and the widest portion of the valve element.

[0021] In another preferred embodiment of the invention, the valve element extends on both sides of the valve opening in all open and closed states of the valve. The valve element may thus be actuated from the side opposite to the closing edge. The valve element may also have an at least partially conical shape such that it can extend at least partially through the valve opening.

[0022] Further details and advantages of the invention are described with reference to embodiments shown in the figures. The figures show: Figure 1 a:side view of the expansion valve; Figure 1 b:sectional side view of the expansion valve; Figure 1c:detailed sectional view of the valve in its closed position; Figure 1d:detailed sectional view of the valve in its open position; and Figure 1e:detailed view of the valve element;

[0023] Figure 1a shows a side view of an embodiment of the expansion valve of the present invention. The valve is provided for a closed-circuit heat exchanger application, wherein the heat exchanger is not shown in the figures. The valve comprises two ports 1, 2, which may be oriented at an angle to each other, preferably at a right angle as shown in the figures. Other angles between e.g. 45° and 180° can also be applied within the scope of the invention. The two ports 1, 2 are provided for connecting the valve to the heat exchanger application.

[0024] The valve may comprise an actuator 10 such as a spring-loaded diaphragm. The spring provides a force acting in one direction, i.e. downward on the diaphragm, while the pressure of a refrigerant fluid in the refrigeration system provides an opposing, i.e. upward force acting on the diaphragm. The downward force acts to open the valve while the upward force acts to close the valve. In effect, when the pressure below the diaphragm is reduced than the valve will open and if the pressure increases the valve will close. The two ports 1, 2 may be an inlet and an outlet port for flowing the refrigerant fluid through the valve.

[0025] Figure 1b shows a sectional view of the expansion valve with details of the actuator 10 and the valve mechanism of the valve. The actuator 10 may comprise a spring, a diaphragm and a rod 6, wherein the rod 6 is provided for connecting the actuator 10 to a valve element 5.

[0026] The valve mechanism is shown in figures 1c and 1d in enlarged views, wherein figure 1c shows the valve in a closed position and figure 1d in an open position.

[0027] The valve comprises a valve seat 4 with a closing edge 41, wherein the closing edge 41 defines or surrounds the valve's valve opening 3. The valve opening 3, the valve seat 4 and the valve element 5 may be provided within the valve and / or along the fluid flow path inside the valve.

[0028] The valve element 5 with a closing portion 52 is provided for closing the valve opening 3. The valve is in a closed position when the valve element 5 engages the valve seat 4 or contacts the valve seat 4 by seating on the valve seat 4 and only leak or bleed flow passes through the valve. The closing portion 52 may be a part of the valve element 5 which contacts the closing edge 41 in a closed position of the valve. The closing portion 52 may be an outer surface of the valve element 5 oriented towards the valve seat 4 and especially the closing edge 41. The valve element 5 and the rod 6 may be arranged on opposite sides of the valve seat 4.

[0029] The valve element 5 comprises at least one recessed portion 51 of circular cross section, functioning as a bleed hole, that may only be provided at the radial position of the closing edge 41 and that provides a passage for the refrigerant fluid to pass through the valve even in its closed position. The recessed portion 51 extends only over a limited distance in the radial direction on the valve element 5. For example, the recessed portion 51 may only be provided on the valve element 5 at a radial position which corresponds to between 2% and 90%, preferably between 10% and 70% and more preferably between 20% and 40%, of the extension of the valve element 5 in its radial direction.

[0030] The closing portion 52 may be at least partially toroidal, wherein the recessed portion 51 may interrupt the closing portion 52 such that the closing portion 52 cannot contact the closing edge 41 along the entire circumference of the closing edge 41. The closing portion 52 may be part of an at least partially conical face of the valve element 5 oriented towards the valve opening 3.

[0031] The positioning of the recessed portion 51 on the valve element 5 makes it possible to manufacture the recessed portion 51 during the same manufacturing step, in which the valve element 5 itself is manufactured. Highly precise manufacturing methods can be easily applied for providing the recessed portion 51, thereby ensuring the desired precise and stable characteristics of the bleed rate.

[0032] The recessed portion 51 may be formed integrally, preferably drilled, within the valve element 5. The drilling of the recessed portion 51 may occur before or after the manufacturing of the remainder of the valve element 5. The recessed portion 51 may be drilled in a direction parallel to the longitudinal axis A shown in figures 1c and 1d. The longitudinal axis A may correspond to the central axis of the valve and the valve element 5 and / or to the direction in which the valve element 5 is movable between the closed and open position of the valve.

[0033] In the embodiments shown in the figures, the recessed portion 51 is a blind bore. The blind bore may extend in the axial direction of the valve element 5.

[0034] Figure 1d clarifies that the recessed portion 51 may be aligned with the closing edge 41 in a radial direction of the valve. This means that a central axis, central plane and / or central portion of the recessed portion 51 may be aligned with the closing edge 41 and / or positioned at the same radial distance as the closing edge 41.

[0035] In the case of a circular cross section recessed portion 51 shown in figure 1c and 1d, the central axis of the recessed portion 51 is aligned with the closing edge 41 provided at the valve seat 4.

[0036] In the closed position of the valve shown in figure 1c, the recessed portion 51 provides a fluid passage across the valve and / or between the two ports 1, 2. The valve element 5 and the recessed portion 51 are shaped such that the valve is not fully closed even in its closed position. Rather, the recessed portion 51 ensures that fluid can pass across the valve and / or between the two ports 1, 2 even in the closed position of the valve.

[0037] The recessed portion 51 and the closing edge 41 may be aligned such that the closing edge 41 divides the recessed portion 51 into two parts of substantially equal cross-sectional area or flow area in the closed state of the valve. These two substantial equal parts correspond to an inlet and an outlet part of the recessed portion 51. As the two parts of the recessed portion 51 are substantially equal, they ensure that the size of the recessed portion 51 can be minimized for a given desired bleed rate.

[0038] The closing edge 41 may be fully circular. There may be no recesses, indents or any other structures at the closing edge 41 providing additional leakage across the valve. The closing edge 41 may thus not contribute any bleeding function to the valve and render the recessed portion 51 the only portion of the valve, which provides such a bleeding function.

[0039] The closing edge 41 may have a diameter of approximately 50% ±20% of the outer diameter of the valve element 5.

[0040] The recessed portion 51 may be oriented in an axial direction of the valve. In particular, a central axis or plane of the recessed portion 51 may be arranged in parallel to the longitudinal axis A of the valve.

[0041] The recessed portion 51 may be offset in a radial direction from the centre of the valve element 5. The recessed portion 51 may thus be easily formed using methods such as drilling during the manufacture of the valve element 5. The recessed portion 51 may also be offset in a radial direction from the outer edge of the valve element 5, such that the recessed portion 51 is provided approximately in the middle between the outer edge of the valve element 5 and the longitudinal axis A of the valve, wherein the longitudinal axis A of the valve may be aligned with a central axis of the valve element 5.

[0042] The diameter of the valve opening 3 may be in the range of 0,55 mm to 10 mm, while the outer diameter of the valve element 5 may be larger by a factor of 2 ±0,5. The diameter or the radial extension of the recessed portion 51 may be in the range of 0,2 mm to 4 mm. The recessed portion 51 may extend in a radial direction partially within and partially outside the radius of the closing edge 41, such that the recessed portion 51 provides a passage between the valve's two ports 1, 2, even in the closed position of the valve.

[0043] The valve element 5 may be provided to extend on both sides of the valve opening 3 and preferably the valve seat 4 in all open and closed positions of the valve. The valve element may thus be present both, above and below the valve opening 3 at all positions of the valve. The valve element 5 may comprise an at least partially conical portion, which is at least partially inserted into the valve opening 3 and preferably into the valve seat 4. The actuator 10 for actuating the valve element 5 may be connected to the narrow end of the valve element 5. The wide end of the valve element 5 may be connected to a spring for preloading the valve element 5 in a direction for closing the valve opening 3. The valve element 5 may thus be provided for being actuated from the side opposite the rod 6 relative to the closing edge 41.

[0044] Figure 1e shows a detailed view of the valve element 5. The recessed portion 51 and the closing portion 52 are shown positioned on a conical face of the valve element 5. The recessed portion 51 and the closing portion 52 may be formed integrally with each other. Both these portions may be provided as part of the same component, i.e. the valve element 5. They may be arranged at the same radial position of the valve element 5.

[0045] The valve element 5 may comprise a radially central and preferably flat or flattened contact portion 53 for contacting the rod 6 shown in figures 1b to 1d. Alternatively, the valve element 5 may be formed integrally with the rod 6. The recessed portion 51 may be provided between the rod 6 and the widest portion of the valve element 5. The rod 6 may be provided for connecting the valve element 5 to the actuator 10.

Claims

1. Expansion valve for a closed circuit heat exchanger application, comprising two ports (1, 2), a valve opening (3), a valve seat (4) with a closing edge (41) and a valve element (5) with a closing portion (52) for closing the valve opening (3), characterized in that the valve element (5) comprises at least one recessed portion (51) functioning as a bleed hole, that is provided with a circular cross section.

2. Expansion valve according to claim 1, characterized in that the recessed portion (51) is formed integrally, preferably drilled, within the valve element (5).

3. Expansion valve according to any of the previous claims, characterized in that the recessed portion (51) is a blind bore.

4. Expansion valve according to any of the previous claims, characterized in that the recessed portion (51) and the closing portion (52) are formed integrally.

5. Expansion valve according to any of the previous claims, characterized in that the recessed portion (51) is aligned with the closing edge (41) in a radial direction of the valve and / or that the recessed portion (51) provides a fluid passage between the two ports (1, 2) in a closed position of the valve.

6. Expansion valve according to any of the previous claims, characterized in that the closing edge (41) is fully circular.

7. Expansion valve according to any of the previous claims, characterized in that the recessed portion (51) is oriented in an axial direction of the valve and / or offset in a radial direction from the centre of the valve element (5).

8. Expansion valve according to any of the previous claims, characterized in that the diameter of the valve opening (3) is in the range of 0,55 mm to 10 mm and / or that the diameter or the radial extension of the recessed portion (51) is in the range of 0,2 mm to 4 mm.

9. Expansion valve according to any of the previous claims, characterized in that the valve element (5) comprises a radially central and preferably flat or flattened contact portion for contacting a rod (6).

10. Expansion valve according to any of the previous claims, characterized in that the valve element (5) extends on both sides of the valve opening (3) in all open and closed states of the valve.

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