WO2010139321A2

WO2010139321A2 - Stirling cooling arrangement

Info

Publication number: WO2010139321A2
Application number: PCT/DK2010/000079
Authority: WO
Inventors: Poul Erik Hansen; Frank Holm Iversen; Snorri Jonsson; Ana Mari Tataru Kjaer; Kaja Lenz; Klaus Reinwand; Jan Thomsen
Original assignee: Danfoss Compressors Gmbh
Priority date: 2009-06-05
Filing date: 2010-06-01
Publication date: 2010-12-09
Also published as: DE102009023970A1; WO2010139321A3

Abstract

The invention relates to a Stirling cooling arrangement (19 with at least one pis¬ ton (5, 6) to be movable in a drive unit (2) along a piston axis (7), and a dis- placer (14) to be movable in a displacer housing (15) along a displacer axis (16), the displacer housing (15) being guided through an isolating wall (17). It is endeavoured to keep the space requirements as small as possible. For this purpose, the piston axis (7) has a different spatial direction than the displacer axis (16).

Description

Stirling cooling arrangement

The invention relates to a Stirling cooling arrangement with at least one piston to be movable in a cylinder along a piston axis, and a displacer to be movable in a displacer housing along a displacer axis, the displacer housing being guided through an isolating wall.

A Stirling cooling arrangement is known from, for example EP 1 630493 A2. At one end the displacer housing has a cold side and at the other end a hot side. The cold side ends with the isolating wall. A heat exchanger is arranged at the end and is connected to a fan. The fan ensures that the air from a room to be cooled is led past the heat exchanger. The hot side comprises a further heat exchanger, and an adjacently arranged drive. The drive is located in a housing through which an air flow is generated by a fan.

A Stirling cooling arrangement works in accordance with the Stirling process. The Stirling process is a thermo-dynamic cycle process, in the ideal case consisting of two isothermal and two isochoric state changes of a gas. The dis- placer pushes the gas with constant mass through a regenerator (first isochoric state change, the volume remains the same, the temperature drops). The regenerator adopts heat from the gas. The resulting colder gas on the "cold side" of the displacer housing adopts heat from the outside, for example from a cooling compartment. Its volume increases at constant temperature (first isothermal state change). By means of the displacer, the gas is led through the regenerator again, where it adopts the heat stored here (second isochoric state change, the volume remains the same, the temperature increases). At constant temperature under reducing volume and increasing pressure, the gas emits heat to the environment (second isothermal change). The required drive power is supplied by the driving arrangement in the form of pressure impulses of the gas. In many cases, the driving arrangement is formed by a piston pump. In this connection, the piston in the pump and the displacer in the displacer housing work with a phase displacement of 90°. The main difference between the displacer and the piston is that on both sides of the displacer the pressure is the same, whereas the piston is used to generate pressure impulses.

As the Stirling process has a relatively good efficiency, a Stirling cooling ar- rangement is well suited for mobile cooling systems. The desired cooling output can often be generated with a lower weight than with a traditional refrigerant compressor. However, the Stirling cooling arrangement known from EP 1 630 492 A2 is relatively large, that is, it projects relatively much over the isolating wall. It is also possible to tilt the Stirling cooling arrangement from 90° and to arrange it in parallel to the cooling wall. In this case, however, a heat conductor will be required from the displacer housing to the other side of the cooling wall, said heat conductor having a negative influence on the efficiency of the cooling arrangement.

The invention is based on the task of keeping the space requirement of a cooling arrangement as small as possible.

With a Stirling cooling arrangement as mentioned in the introduction, this task is solved in that the piston axis has a different spatial direction than the displacer axis.

If different spatial directions are defined, for example, in a cathesic coordinate system, the piston axis can be placed in the X-direction and the displacer axis in the Y-direction. Thus, it is no longer required for the piston and the displacer to move in the same direction. This can be utilised to reduce the dimensions of the cooling arrangement. If, for example, the displacer axis is arranged perpendicularly to the isolating wall, which is expedient to locate the cold side of the displacer housing on one side and the hot side of the displacer housing on the other side of the isolating wall, the piston axis can be arranged in parallel to the isolating wall. The space required on the hot side of the isolating wall can thus be substantially reduced.

It is preferred that the piston axis and the displacer axis do not cross one another. This gives substantially more freedom to select the location of cylinder and displacer housing. For example, the cylinder can then be placed practically next to the displacer housing, so that the available space can be even better utilised.

Preferably, the piston axis has a direction that encloses an angle of 90° ± 10° with the direction of the displacer axis. This also applies, when the piston axis and the displacer axis do not cross one another. In this case, the angle is determined by displacing one of the two axes, until the two axes cross one another. Arranging the piston axis and the displacer axis at directions crossing each other under an angle of approximately 90° has advantages with regard to design.

Advantageously, the cylinder and the displacer housing are connected to each other by a tubing. Thus, it is possible to provide a spatial distance between the cylinder and the displacer housing. The cylinder and the displacer housing do not have to be located immediately adjacent to one another. This gives further freedom for the design of the cooling arrangement, so that less space will be required.

Preferably, the tubing ends in the cylinder at a position in the circumferential direction that lies in a segment, which is adjacent to a peak and has a size of 45°, the peak being a point through which a line extends that crosses both the piston axis and the displacer axis under an angle of 90°. In a figurative manner of speaking, the peak of the cylinder is thus "at the top", whereas the tubing does not end quite at the top, but offset somewhat laterally to it. Thus, the tubing extends "in a slanted manner" from the cylinder. This makes it possible to arrange the cylinder and the displacer housing at a favourable position in relation to one another.

Preferably, the displacer housing and the cylinder overlap, at least partly. In at least one plane of a three-dimensional coordinate system a crossing of the projections of the cylinder and the displacer housing on this plane will appear. As the location of the displacer housing is fixed by the isolating wall, this is a particularly favourable utilisation of the space. Preferably, the cylinder extends into an extension of the displacer housing. In this case, a crossing of the projections of the cylinder and the displacer housing occurs in a plane, to which the piston axis extends perpendicularly. This has the advantage that the cylinder can be made with a relatively large diameter.

In this case, it is advantageous, if the tubing ends in an end face of the displacer housing. This gives favourable flow conditions.

In an alternative embodiment it may be provided that the displacer housing covers the cylinder at least partly in the direction of the displacer axis. Also this is a good opportunity of utilising the available space.

In this case, it may be advantageous if, in the circumferential direction, the tub- ing ends at a position of the displacer housing, in which the circumference of the displacer housing has the smallest distance to the cylinder. In a figurative manner of speaking, the tubing thus does not leave the cylinder right "at the top", but it ends "at the bottom" of the displacer housing.

Preferably, the tubing is curved, at least in sections. This gives more flexibility in running the tubing.

In the following, the invention is described on the basis of preferred embodiments in connection with the drawings, showing:

Fig. 1 a schematic cross-section through a Stirling cooling arrangement,

Fig. 2 a partial section M-Il according to Fig. 1 , and

Fig. 3 a perspective vies of a modified embodiment, partly in section.

A Stirling cooling arrangement 1 comprises a drive unit 2 and a cooling unit 3. In the present case, the drive unit 2 comprises a cylinder 4, in which two pistons 5, 6 are arranged. The two pistons 5, 6 are arranged to be movable in opposite directions along a piston axis 7. They are driven by electric magnets 8, 9 acting upon armatures 10, 11, which again are connected to the pistons 5, 6 by means of piston rods 12, 13. The piston axis 7 of Fig. 2 extends from the left to the right and in Fig. 1 perpendicularly to the drawing plane.

The cooling unit 3 comprises a displacer 14 that is movable in a displacer housing 15 along a displacer axis 16. The displacer 14 and the pistons 5, 6 are not mechanically connected to each other. They work with a phase displacement of approximately 90° to one another.

The displacer housing 15 is guided through an isolating wall 17. It projects at both sides of the isolating wall 17. In this connection, the side facing the drive unit 2 is called the "hot side" and the side of the displacer housing 15 arranged on the other side of the isolating wall 17 is called the "cold side". A first heat exchanger 18 is provided on the hot side, and a second heat exchanger 19 is pro- vided on the cold side. A regenerator 20 is located between the two heat exchangers 18, 19. The heat exchangers 18, 19 and the regenerator 20 are arranged in an annular gap formed between the displacer housing 15 and a cylinder liner 21 of the displacer housing 15.

The two heat exchangers 18, 19 and the regenerator 20, however, must not necessarily be arranged in the displacer housing 15, if it can be ensured in a different manner that the displacer housing 15 has a cold side and a hot side.

A cooling member 22 is fixed to the cold side of the displacer housing 15, a fan 23 ensuring an air flow through the cooling member 22. As the cooling member 22 has a heat conducting connection to the cold side of the displacer housing 15, heat is dissipated to the displacer housing 15 via the cooling member 22, said heat being transferred to the hot side of the displacer housing by means of the Stirling process. This enables an air-air cooling. Thus, not only can heat be exhausted from a closed room, thus cooling the room, but also a cooled air flow can be generated.

As appears clearly from Fig. 1 , the piston axis 7 has a different direction in the room than the displacer axis 16. The piston axis 7 is perpendicular to the draw- ing plane. The displacer axis 16, however, extends from the left to the right in the drawing plane. The piston axis 7 and the displacer axis 16 do not cross one another. The piston axis 7 has a direction that encloses an angle of approximately 90° with the direction of the displacer axis 16. The directions of the two axes 7, 16 extend in parallel to the axes 7, 16.

The displacer housing 15 and the drive unit 2 are connected to one another via a tubing 24, the tubing 24 having a curved section 25. The tubing 24 ends in an end face of the displacer housing 15 that is substantially perpendicular to the displacer axis 16.

The tubing 24 ends in the drive unit 2 in an area that encloses approximately 45° originating from a peak 26 of the drive unit 2. The peak 26 is an imagined point, through which a line extends that is not shown in detail, and that crosses both the cylinder axis 7 and the displacer axis 16 under an angle of 90°. The fact that the tubing 24 extends under an obtuse angle in relation to the displacer axis 16 causes favourable space conditions.

As can be seen from Fig. 1 , the drive unit 2 is arranged so that it extends into an imagined extension of the displacer housing 15. Thus, in the direction of the displacer axis 16 the displacer housing 15 crosses the drive unit 2. Thus, it is possible to make the drive unit 2 with a relatively large diameter without excessively expanding the dimensions of the cooling arrangement 1.

On the hot side of the displacer housing 15 a further cooling member 27 is arranged that is connected to a fan 28. The fan 28 generates an air flow through the cooling member 27 to guide heat that has been transported from the cold side to the hot side by means of the cooling unit 3.

Fig. 3 shows a modified embodiment in a perspective view, partly in section. The same elements have the same reference numbers as in Figs. 1 and 2. For reasons of clarity, the perspective view shows neither the pistons 5, 6, nor the displacer 14. Fig. 3 merely shows the corresponding piston axis 7 and the corresponding displacer axis 16. It can be seen that compared to the embodiment according to Fig. 1 , the dis- placer housing 15 and the drive unit 2 are arranged differently in relation to each other. Here, the displacer housing 15 covers the drive unit 2 somewhat in the direction of the displacer axis 16. The tubing 25 again extends "in a slanted manner" from the drive unit 2, however ends in the displacer housing 15 at a circumferential position that has the smallest distance to the drive unit 2. Also with this embodiment, a very compact arrangement of the displacer housing 15, the isolating wall 17 and the drive unit 2 can be achieved.

The drive unit 2 can also be made with only one piston 5. It is preferred that the piston axis 7 extends in parallel to the isolating wall 17. This is, however, not absolutely required.

Claims

Patent claims

1. Stirling cooling arrangement with at least one piston to be movable in a cylinder along a piston axis, and a displacer to be movable in a displacer housing along a displacer axis, the displacer housing being guided through an isolating wall, characterised in that the piston axis (7) has a different spatial direction than the displacer axis (16).

2. Stirling cooling arrangement according to claim 1 , characterised in that the piston axis (7) and the displacer axis (16) do not cross one another.

3. Stirling cooling arrangement according to claim 1 or 2, characterised in that the piston axis (7) has a direction that encloses an angle of 90° ± 10° with the direction of the displacer axis (16).

4. Stirling cooling arrangement according to one of the claims 1 to 3, characterised in that drive unit (2) and the displacer housing (15) are connected to each other by a tubing (24).

5. Stirling cooling arrangement according to claim 4, characterised in that the tubing (24) ends in the drive unit (2) at a position in the circumferential direction, that lies in a segment, which is adjacent to a peak (26) and has a size of 45°, the peak (26) being a point through which a line extends that crosses both the piston axis (7) and the displacer axis (16) under an angle of 90°.

6. Stirling cooling arrangement according to one of the claims 1 to 5, characterised in that the displacer housing (15) and the drive unit (2) overlap, at least partly.

7. Stirling cooling arrangement according to claim 6, characterised in that the drive unit (2) extends into an imagined extension of the displacer housing (15).

8. Stirling cooling arrangement according to claim 7, characterised in that the tubing (24) ends in an end face of the displacer housing (15).

9. Stirling cooling arrangement according to claim 6, characterised in that the displacer housing (15) covers the drive unit (2) at least partly in the direction of the displacer axis (16).

10. Stirling cooling arrangement according to claim 9, characterised in that in the circumferential direction, the tubing (24) ends at a position of the displacer housing (15), in which the circumference of the displacer housing (15) has the smallest distance to the drive unit (2).

11. Stirling cooling arrangement according to one of the claims 4 to 10, char- acterised in that the tubing (24) is curved, at least in sections.