WO2009146704A1

WO2009146704A1 - An expansion valve comprising a valve part with a piston portion

Info

Publication number: WO2009146704A1
Application number: PCT/DK2009/000129
Authority: WO
Inventors: Leo Bram
Original assignee: Danfoss A/S
Priority date: 2008-06-04
Filing date: 2009-06-03
Publication date: 2009-12-10

Abstract

An expansion valve (1) comprising an inlet opening (10), at least two outlet openings (7), a first valve part (2) and a second valve part (4) is disclosed. The inlet opening (10) is adapted to receive fluid medium in a liquid state, and the outlet openings (7) are adapted to deliver fluid medium in an at least partly gaseous state. The first valve part (2) comprises a piston portion (3), and the second valve part (4) comprises a piston receiving portion (5) adapted to receive the piston portion (3) of the first valve part (2). The piston receiving portion (5) has at least two openings (6) formed therein, each of the openings (6) being fluidly connected to one of the outlet openings (7). The openings (6) are arranged in such a manner that each of the openings (6) in combination with the piston portion (3) defines a valve. The first valve part (2) and the second valve part (4) are arranged movably relative to each other in such a manner that the mutual position of the first valve part (2) and the second valve part (4) defines an opening degree of each of the valves.

Description

AN EXPANSION VALVE COMPRISING A VALVE PART WITH A PISTON PORTION

FIELD OF THE INVENTION

The present invention relates to an expansion valve, in particular for use in a refrigeration system, e.g. an air condition system. The expansion valve of the present invention is adapted to distribute fluid medium to at least two parallel flow paths, e.g. in the form of at least two parallel evaporators or evaporator tubes.

BACKGROUND OF THE INVENTION

In a fluid circuit, such as a refrigerant circuit of a refrigeration system, it is sometimes desirable to split the flow path into two or more parallel flow paths along part of the fluid circuit. This is, e.g., the case in refrigeration systems comprising two or more evaporators arranged in parallel. It may further be desirable to be able to control the fluid flow to each of the parallel flow paths, e.g. in such a manner that a substantially equal fluid distribution is obtained, or in such a manner that the system is operated in an optimum manner, e.g. in terms of energy consumption or efficiency.

In some previous attempts to control distribution of refrigerant between two or more parallel flow paths in a refrigeration system, a distributor is arranged downstream relative to an expansion valve in the refrigerant flow path. Thus, the refrigerant is distributed after expansion of the refrigerant, i.e. the refrigerant is mainly gaseous. This has the disadvantage that it is very difficult to control the flow of refrigerant to obtain a substantially equal distribution between the parallel flow paths. DESCRIPTION OF THE INVENTION

It is an object of embodiments of the invention to provide an expansion valve which is capable of controlling distribution of fluid to two or more parallel flow paths.

It is a further object of embodiments of the invention to provide an expansion valve which is adapted to manage distribution of fluid to two or more parallel flow paths in an easy manner.

According to a first aspect of the invention the above and other objects are fulfilled by providing an expansion valve comprising:

- an inlet opening adapted to receive fluid medium in a liquid state,

- at least two outlet openings, each being adapted to deliver fluid medium in an at least partly gaseous state,

- a first valve part comprising a piston portion,

- a second valve part comprising a piston receiving portion adapted to receive the piston portion of the first valve part, the piston receiving portion having at least two openings formed therein, each of the openings being fluidly connected to one of the outlet openings, and the openings being arranged in such a manner that each of the openings in combination with the piston portion defines a valve,

wherein the first valve part and the second valve part are arranged movably relative to each other in such a manner that the mutual position of the first valve part and the second valve part defines an opening degree of each of the valves.

The expansion valve of the invention defines flow paths between the inlet opening and the at least two outlet openings. Fluid medium in a liquid state is received at the inlet opening and fluid medium in an at least partly gaseous state is delivered at the outlet openings. In the present context the term 'liquid state' should be interpreted to mean that the fluid medium entering the expansion valve via the inlet opening is substantially in a liquid phase. Similarly, in the present context the term 'at least partly gaseous state' should be interpreted to mean that the fluid medium leaving the expansion valve via the outlet openings is completely in a gaseous phase, or at least a part, e.g. a substantial part, of the volume of the fluid medium leaving the expansion valve is in a gaseous phase. Accordingly, at least a part of the fluid medium entering the expansion valve undergoes a phase transition from the liquid phase to the gaseous phase when passing through the expansion valve.

The inlet opening and the outlet openings may preferably be fluidly connected to one or more other components, such as other components of a refrigeration system. The expansion valve may advantageously form part of a flow system, such as a flow circuit.

The expansion valve comprises a first valve part and a second valve part. The first valve part comprises a piston portion, and the second valve part comprises a piston receiving portion adapted to receive the piston portion of the first valve part. The piston portion and the piston receiving portion are preferably sized and shaped in such a manner that the piston portion fits, e.g. slidingly, inside the piston receiving portion.

The piston receiving portion has at least two openings formed therein. Each of the openings is fluidly connected to one of the outlet openings. Furthermore, the openings are arranged in such a manner that each of the openings in combination with the piston portion defines a valve. Thus, the openings of the piston receiving portion provide flow paths towards the outlet openings, and the fluid flow towards each of the outlet openings is determined by the valve defined by the corresponding opening and the piston portion. The first valve part and the second valve part are arranged movably relative to each other. This may be achieved by mounting the first and/or the second valve part in a manner which allows it/them to move relative to the remaining parts of the expansion valve. Thus, the first valve part may be movable while the second valve part is mounted in a fixed manner. As an alternative, the second valve part may be movable while the first valve part is mounted in a fixed manner. Finally, both of the valve parts may be movably mounted. In all of the situations described above a relative movement between the first valve part and the second valve part is possible, thereby defining a mutual position of the first valve part and the second valve part. This mutual position determines an opening degree of each of the valves defined by the openings and the piston part. Thus, the opening degrees of the valves, and thereby the amount of fluid medium supplied to each of the outlet openings, can be adjusted by adjusting the mutual position of the first valve part and the second valve part. Since the opening degrees of the valves are defined by the mutual position of the first valve part and the second valve part, the opening degrees are adjusted synchronously, thereby at least substantially maintaining a distribution key among the outlet openings.

When the first valve part and the second valve part perform relative movements, the piston portion and the piston receiving portion are also moved relative to each other, thereby moving the piston portion and the openings relative to each other. This defines the opening degree of the valve defined by the openings and the piston portion. Thereby the opening degrees of the valves can be controlled in a very easy manner, e.g. simply by moving the piston portion received in the piston receiving portion. Furthermore, the opening degrees are controlled simultaneously as described above, thereby at least substantially maintaining the fluid distribution key among the at least two outlet openings of the expansion valve. This is an advantage.

Furthermore, since the valve parts define a valve towards each of the outlet openings, the expansion valve has a fluid distributing function, i.e. it may be seen as having a fluid distributor forming part thereof. This is an advantage, because the distribution of the fluid medium between the outlet openings thereby takes place either before or during expansion of the fluid medium. Thereby it is obtained that the fluid medium is distributed while at least a substantial part of it is in the liquid phase. This makes it easier to control the distribution. Furthermore, it makes the expansion valve suitable for use in flow systems of the microchannel type.

The piston receiving portion may be hollow and it may have a substantially cylindrical shape. According to this embodiment the piston receiving portion has a substantially circular cross section, the size and shape of the cross section being substantially independent of a position along a substantially axial direction. Thereby a piston having a circular cross section of a matching size can be received in the piston receiving portion, and the piston is allowed to perform movements along the substantially axial direction.

As an alternative, the piston receiving section may have a non-circular cross section, e.g. an oval, a triangular, a quadrangular, a rectangular, a hexagonal, etc. cross section. The cross section may even have a non-regular shape. In any case the size and shape of the cross section is preferably independent of a position along a substantially axial direction, thereby allowing a piston having a matching size and shape to be received and perform axial movements inside the piston receiving portion.

The piston receiving portion may be provided with a lining having openings arranged at positions corresponding to the positions of the openings of the second valve part. The lining may, e.g., provide a low friction interface towards the piston portion, thereby allowing the relative movements between the piston portion and the piston receiving portion to be performed in a relatively smooth manner and with minimal energy loss. Alternatively or additionally, the lining may provide a sealing effect towards the piston portion. Alternatively or additionally, the openings of the lining may define the opening profiles of the valves defined by the openings and the piston portion. This will be described in further detail below. According to one embodiment, a geometry of the openings of the lining and/or the openings of the second valve part may define a correspondence between opening degree of the valves and mutual position of the first valve part and the second valve part. The openings may, e.g., have a specific shape, and relative movements of the piston portion and the piston receiving portion may result in the piston portion covering a varying area of the openings. For instance, the openings may be in the form of narrow slits and the relative movements between the piston portion and the piston receiving portion may take place along a longitudinal direction of the slits. In this case the opening degrees of the valves vary as a substantially linear function of the mutual position of the piston portion and the piston receiving portion. Alternatively, the openings may have other shapes, such as substantially circular, oval, triangular, tear drop shaped, etc., in which case the variation in opening degree is non-linear in response to variations in relative position of the piston portion and the piston receiving portion.

The correspondence between opening degree of the valves and mutual position of the first valve part and the second valve part may be defined solely by a geometry of the openings of the lining. In this case it may be easier to provide openings of an accurate size and shape in the lining than in the piston receiving portion. The openings of the piston receiving portion may, thus, be relatively coarse, while the openings of the lining provide a desired profile of the valves towards the outlet openings. Furthermore, identical valve parts may be used for expansion valves having different correspondence between opening degree of the valves and mutual position of the first valve part and the second valve part, simply by inserting a lining in which the openings have a geometry defining a desired correspondence.

The first valve part and the second valve part may be adapted to perform substantially linear relative movements. The substantially linear relative movements may, e.g., be performed along a substantially axial direction. In this case the relative movements of the piston portion and the piston receiving portion preferably correspond to ordinary movements of a piston. The openings of the piston receiving portion may be arranged substantially annularly, and the axial movements of the piston portion relative to the piston receiving portion may cause the piston portion to cover a varying area of the openings, thereby varying the size of the openings towards the outlet openings.

As an alternative, the first valve part and the second valve part may be adapted to perform substantially rotational relative movements. In this case the piston receiving portion preferably has a substantially circular cross section allowing the piston portion to perform rotational movements inside the piston receiving portion.

As another alternative, the first valve part and the second valve part may be adapted to perform relative movements which are partly substantially linear and partly substantially rotational. An example of such a relative movement is a movement following a substantially helical path.

At least two of the openings of the piston receiving portion may be disposed along a substantially axial direction of the piston receiving portion. The openings may be arranged substantially at the same annular position.

Alternatively or additionally, at least two of the openings of the piston receiving portion may be disposed along a substantially annular direction of the piston receiving portion. The openings may be arranged at the same axial level. In this case axial movements of the piston portion relative to the piston receiving portion will cause the piston to simultaneously cover a varying portion of each of the openings. Accordingly, the piston may advantageously be arranged to perform axial movements in this case.

The openings may be disposed along an axial direction as well as along an annular direction. In this case the openings may be arranged in a helical pattern. The expansion valve may further comprise a thermostatic element, and the first valve part and/or the second valve part may be operatively connected to the thermostatic element, relative movements of the first valve part and the second valve part thereby being caused by the thermostatic element. According to this embodiment, the thermostatic element determines the opening degrees of each of the valves defined by the openings and the piston portion, i.e. the thermostatic element simultaneously determines the mass flow to each of the outlet openings.

According to a second aspect of the invention the above and other objects are fulfilled by providing a refrigeration system comprising:

- at least one compressor,

- at least one condenser,

- at least two evaporators arranged in parallel along a refrigerant flow path of the refrigeration system, and

- an expansion valve according to the first aspect of the invention, said expansion valve being arranged in such a manner that each of the at least two outlet openings is arranged to deliver refrigerant to one of the evaporators.

Thus, the expansion valve according to the first aspect of the invention may advantageously be arranged in a refrigeration path of a refrigeration system, e.g. a refrigeration system used in a cooling arrangement or an air condition system.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in further detail with reference to the accompanying drawings in which Fig. 1 is a cross sectional view of an expansion valve according to a first embodiment of the invention,

Fig. 2 is a perspective view of a lining for the expansion valve of Fig. 1 ,

Fig. 3 is a schematic illustration of the expansion valve of Fig. 1,

Fig. 4 is a schematic illustration of an expansion valve according to a second embodiment of the invention,

Fig. 5 is a schematic view of an expansion valve according to a third embodiment of the invention, and

Fig. 6 illustrates correspondence between relative position of the first and second valve part and opening degree for four different opening geometries.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. 1 is a cross sectional view of an expansion valve 1 according to a first embodiment of the invention. The expansion valve comprises a first valve part 2 comprising a piston portion 3 and a second valve part 4 comprising a piston receiving portion 5. The piston portion 3 is arranged inside the piston receiving portion 5 in such a manner that the piston 3 is movable along an axial direction.

The piston receiving portion 5 has four openings 6, two of which are visible, arranged therein. Each of the openings 6 is fluidly connected to an outlet opening 7 adapted to deliver fluid in an at least partly gaseous phase as indicated by the arrows.

A lining 8 is arranged in an interior part of the piston receiving portion 5. The lining 8 is provided with a number of longitudinal slits 9, three of which are visible. At least some of the slits 9 are arranged at positions corresponding to the positions of the openings 6. Accordingly, the slits 9 and the openings 6 define four fluid passages towards the outlet openings 7. The expansion valve 1 of Fig. 1 may be operated in the following manner. Fluid medium in a substantially liquid state is received in the expansion valve 1 via inlet opening 10 as indicated by the arrow. The fluid medium is led through the piston receiving portion 5 towards the slits 9 formed in the lining 8, through the slits 9 and leaves the expansion valve 1 via the outlet openings 7. During this fluid medium is expanded, and the fluid medium leaving the expansion valve 1 via the outlet openings 7 is therefore in an at least partly gaseous state.

As mentioned above the piston portion 3 is movable along a substantially axial direction relative to the piston receiving portion 5. The axial position of the piston portion 3 determines how large a portion of the slits 9 is covered by the piston portion 3. Thus, the axial position of the piston portion 3 determines how large the openings towards the outlet openings 7 are. Accordingly, the piston portion 3 and the slits 9 in combination define four valves, and the opening degrees of these valves are determined by the axial position of the piston portion 3 relative to the piston receiving portion 5.

Fig. 2 is a perspective view of a lining 8 for the expansion valve 1 of Fig. 1. Three of the slits 9 are clearly visible. In the embodiment illustrated in Figs. 1 and 2 the lining 8 is a separate part which can be inserted inside the piston receiving portion 5. The slits 9 define the geometry of the openings of the valves defined by the openings 6 and the piston portion 3. Thus, a correspondence between axial position of the piston portion 3 and opening degree of the valves can be designed by selecting a suitable geometry of the slits 9 and/or by replacing the slits 9 by openings having a different shape. This will be described further below with reference to Fig. 6.

Fig. 3 is a cross sectional view illustrating an expansion valve 1 according to a second embodiment of the invention. Fig. 3 shows a first valve part 2 comprising a piston portion 3 and a second valve part 4 comprising a piston receiving portion 5. A number of openings 6, two of which are visible, are provided in the piston receiving portion 5, each opening 6 being fluidly connected to an outlet opening. The openings 6 are disposed substantially annularly in the piston receiving portion 5, similarly to the situation illustrated in Fig. 1. Accordingly, the axial position of the piston portion 3 simultaneously determines an opening degree of each of the valves defined by the openings 6 and the piston portion 3.

Fig. 4 is a cross sectional view illustrating an expansion valve 1 according to a third embodiment of the invention. Similarly to Fig. 3, Fig. 4 shows a first valve part 2 comprising a piston portion 3 and a second valve part 4 comprising a piston receiving portion 5. A number of openings 6, eight of which are visible, are provided in the piston receiving portion 5, each opening 6 being fluidly connected to an outlet opening 7. The openings 6 are disposed substantially equidistantly along a substantially axial direction, as well as substantially angularly.

The piston portion 3 comprises four regions having an increased cross sectional diameter. These four regions are arranged at positions corresponding to four different axial positions of the openings 6 of the piston receiving portion 5. The axial position of the piston portion 3 determines how large a portion of each of the openings 6 is covered by a corresponding enlarged diameter region of the piston portion 3. Thereby the axial position of the piston portion 3 simultaneously determines the opening degrees of the valves defined by the openings 6 and the piston portion 3.

Fig. 5 is a cross sectional view illustrating an expansion valve 1 according to a fourth embodiment of the invention. Similarly to Figs. 3 and 4, Fig. 5 shows a first valve part 2 comprising a piston portion 3 and a second valve part 4 comprising a piston receiving portion 5. Four openings 6 are provided in the piston receiving portion 5, each opening 6 being fluidly connected to an outlet opening 7. The openings 6 are disposed substantially equidistantly along a substantially axial direction.

The piston portion 3 comprises four regions having an increased cross sectional diameter. Accordingly, the embodiment shown in Fig. 5 is very similar to the embodiment shown in Fig. 4. However, in the embodiment of Fig. 5 only one opening 6 is provided per axial level.

Fig. 6 illustrates correspondence between opening degree of the valves defined by the openings 6 and the axial position of the piston portion 3 for four different geometries of the openings 6. The geometries need not be defined directly by the openings 6, but may be defined by openings formed in a lining 8 arranged in the piston receiving portion 5, similarly to the slits 9 shown in Figs. 1 and 2.

The four different geometries are shown at the top of the Figure and marked A, B, C and D, respectively. A is a narrow slit, B is a triangular like shape with two slightly curved sides, C is a triangle and D is a circle.

The graph shown below the geometries illustrates opening degree or mass flow as a function of axial position of the piston portion for each of the four geometries. It is clear from the graph that the variations in opening degree in response to axial movements of the piston portion is highly dependent on the geometry of the openings.

Claims

1. An expansion valve (1) comprising:

- an inlet opening (10) adapted to receive fluid medium in a liquid state,

- at least two outlet openings (7), each being adapted to deliver fluid medium in an at least partly gaseous state,

- a first valve part (2) comprising a piston portion (3),

- a second valve part (4) comprising a piston receiving portion (5) adapted to receive the piston portion (3) of the first valve part (2), the piston receiving portion (5) having at least two openings (6) formed therein, each of the openings (6) being fluidly connected to one of the outlet openings (7), and the openings (6) being arranged in such a manner that each of the openings (6) in combination with the piston portion (3) defines a valve,

wherein the first valve part (2) and the second valve part (4) are arranged movably relative to each other in such a manner that the mutual position of the first valve part (2) and the second valve part (4) defines an opening degree of each of the valves.

2. An expansion valve (1) according to claim 1, wherein the piston receiving portion (5) is hollow and has a substantially cylindrical shape.

3. An expansion valve (1) according to claim 1 or 2, wherein the piston receiving portion (5) is provided with a lining (8) having openings (9, A, B, C, D) arranged at positions corresponding to the positions of the openings (6) of the second valve part (4).

4. An expansion valve (1) according to claim 3, wherein a geometry of the openings (9, A, B, C₁ D) of the lining (8) and/or the openings (6) of the second valve part (4) define a correspondence between opening degree of the valves and mutual position of the first valve part (2) and the second valve part (4).

5. An expansion valve (1) according to any of the preceding claims, wherein the first valve part (2) and the second valve part (4) are adapted to perform substantially linear relative movements.

6. An expansion valve (1) according to claim 5, wherein the substantially linear relative movements are performed along a substantially axial direction.

7. An expansion valve (1) according to any of the preceding claims, wherein at least two of the openings (6) of the piston receiving portion (5) are disposed along a substantially axial direction of the piston receiving portion (5).

8. An expansion valve (1) according to any of the preceding claims, wherein at least two of the openings (6) of the piston receiving portion (5) are disposed along a substantially annular direction of the piston receiving portion (5).

9. An expansion valve (1) according to any of the preceding claims, further comprising a thermostatic element, wherein the first valve part (2) and/or the second valve part (4) is/are operatively connected to the thermostatic element, relative movements of the first valve part (2) and the second valve part (4) thereby being caused by the thermostatic element.

10. A refrigeration system comprising:

- at least one compressor,

- at least one condenser,

- at least two evaporators arranged in parallel along a refrigerant flow path of the refrigeration system, and an expansion valve (1) according to any of the preceding claims, said expansion valve (1) being arranged in such a manner that each of the at least two outlet openings (7) is arranged to deliver refrigerant to one of the evaporators.