WO2010139319A2

WO2010139319A2 - Stirling cooling arrangement

Info

Publication number: WO2010139319A2
Application number: PCT/DK2010/000077
Authority: WO
Inventors: Poul Erik Hantsen; Frank Holm Iversen; Snorri Jonsson; Jan Thomsen; Kaja Lenz; Klaus Reinwand
Original assignee: Danfoss Compressors Gmbh
Priority date: 2009-06-05
Filing date: 2010-06-01
Publication date: 2010-12-09
Also published as: WO2010139319A3; DE102009023979A1

Abstract

The invention relates to a Stirling cooling arrangement (1) with a driving unit (2) and a displacer arrangement (3, 4) that is connected to the driving unit (2) via a gas pipe (5). It is endeavoured to achieve a smooth operation of such a cooling arrangement. For this purpose, the displacer arrangement (3, 4) comprises at least two displacers (15), whose movements are adapted to each other.

Description

Stirling cooling arrangement

The invention relates to a Stirling cooling arrangement with a driving unit and a displacer arrangement that is connected to the driving unit via a gas pipe.

Such a Stirling cooling arrangement is, for example, known from EP 1 348 918 A1. The displacer arrangement comprises a displacer housing, in which a displacer is movable along a displacer axis. The driving unit comprises a piston that is movable in a cylinder along a piston axis. The piston axis and the displacer axis are coincident. A gas guiding path is arranged between the piston and the displacer.

Such a cooling arrangement works in accordance with the Stirling process.

A cooling arrangement working according to the Stirling process has a relatively good relation between the achievable cooling capacity and the mass. It is therefore particularly suited for mobile applications. With mobile applications, the demands on the running smoothness are increased. Also with sta- tionary applications, however, it is desired that the cooling arrangement works smoothly and causes the least possible vibrations.

The invention is based on the task of providing a smooth operation of a Stirling cooling arrangement.

With a Stirling cooling arrangement as mentioned in the introduction this task is solved in that the displacer arrangement comprises at least two displacer units, whose movements are adapted to each other.

During operation of a Stirling cooling arrangement, the displacer must reciprocate once during each cycle to push gas back and forth through the regenerator. During the movement of the displacer in the displacer housing, reaction forces occur that can, for example cause a vibration of the displacer housing. If, now, several displacer units are provided, the movements of the displacers can be adapted to each other in such a manner that the reaction forces are at least substantially neutralised. Thus, reaction forces are generated, the sum of which is smaller than the reaction force of only one dis- placer. The smaller the reaction forces acting on the displacer arrangement, the smaller the amplitude of an oscillation or vibration performed by the displacer arrangement. The smaller the amplitude, the smaller the interference caused by the noise generated by this vibration.

In a preferred embodiment, it is provided that at least two displacers are movable in counterphase to one another with at least one spatial direction component. The reaction forces caused by the displacers in the direction of the spatial direction component will then equalise one another. In this connection, it is assumed that the displacers generate the same reaction forces, which is in the simplest case achieved in that they have the same mass.

It is particularly preferred that two displacers are movable along the same displacer axis. In this case, the reaction forces of these two displacers are directed oppositely to one another. If these reaction forces have the same size, which is, for example, the case with displacers having the same mass, these reaction forces equalise each other. A vibration in the direction parallel to the displacer axis can be kept very small or even completely suppressed.

Preferably, the displacers are arranged in different displacer housings. This is a simple measure of ensuring that each displacer housing can be provided with a hot side and a cold side. The cold side is then arranged in a cooling compartment and the hot side is arranged outside the cooling compartment, so that the displacer arrangement can be used as a heat pump that transports heat away from the cooling compartment.

It is preferred that the displacer housings are connected to the driving unit with equal pipes. The pressure impulses generated by the driving unit in the gas that is adopted by the cooling arrangement can then be passed on in an equal manner to the displacers in the displacer housings. In this connection, "equal" relates to the effect that is achieved with the pipe, that is, the simul- taneous pressure action on the displacers in the same function direction. In the simplest case, this can be achieved in that the pipes have the same length and the same cross-section.

Preferably, the driving unit is made as a piston pump with at least one piston to be movable along a piston axis, the piston axis having a different spatial direction than the displacement axis, along which the displacers are movable. By means of the different spatial directions of the piston axis and the displacer axis, it is avoided that the reaction forces of piston and displacers superpose each other in the same direction. This results in a decoupling of these reaction forces is achieved. Thus, the reaction forces generated by the piston on the one side and by the displacers on the other side can be treated separately, and separate compensation means can be used for them.

Preferably, the displacer axis is arranged in a first plane that is perpendicular to a second plane, in which the piston axis is arranged. In a three- dimensional carthesic coordinate system, the displacer axis can, for example be arranged in the x-y plane, whereas the piston axis is arranged in the x-z plane. With regard to direction, thus a complete decoupling of the reaction forces caused by the displacers and the piston(s) is achieved.

Preferably, the displacer axis and the piston axis extend without intersecting each other. This means that on their whole extension the displacer axis and the piston axis has a predetermined minimum distance to one another. This is a further measure of realising a favourable decoupling.

In a preferred embodiment, it is provided that each displacer housing is guided through a leg of an isolating plate having a U-shape. The U-shaped isolating plate then separates the cold side of the displacer housing from the hot side. The driving unit is then also arranged on the hot side.

Preferably, the piston axis extends in parallel with the legs. It is also favourable, if the piston axis extends in parallel to the base of the U-shaped isolating plate. The space available can then be well utilised. In the following, the invention is described on the basis of preferred embodiments in connection with the drawings, showing:

Fig. 1 a schematic view of a first embodiment of a cooling arrangement,

Fig. 2 a displacer arrangement of the cooling arrangement in a schematic cross-sectional view,

Fig. 3 a driving unit of the cooling arrangement according to Fig. 1 in a schematic cross-sectional view,

Fig. 4 a modified embodiment of a cooling arrangement.

A cooling arrangement 1 , as shown schematically in Fig. 1, comprises a driving unit 2 and a displacer arrangement that is formed by two displacer units 3, 4. The driving unit 2 is connected to the displacer units 3, 4 via a T-shaped pipe 5 that comprises a section 6 that is common for both displacer units 3, 4 and two similarly formed sections 7, 8. A gas pressure impulse that is generated by the driving unit 2 reaches the two displacer units 3, 4 at the same time, so that it also causes the same effect in the two displacer units 3, 4.

Each displacer unit 3, 4 has a displacer housing 9, 10. The two displacer housings 9, 10 are guided through an isolating plate 11. The isolating plate 11 is made in a U-shape with a base 12 and two legs 13, 14. The driving unit 2 is, at least partly, arranged between the two legs 13, 14. The isolating plate 11 separates a hot side of the displacer housing 9, 10, at which the pipe 5 ends, from a cold side that is located at the other side of the isolating plate 11. Both on the hot side and on the cold side of the displacer housings 9, 10 cooling members or heat conducting members can be arranged. For reasons of clarity, they are not shown here. Also not shown for reasons of clarity, are fans or ventilators guiding an air flow along the hot side to cool it, or along the cold side to carry air to be cooled to that side. Fig. 2 is a schematic view of the design of the displacer 4. The displacer unit 3 is made in the same manner.

In the displacer housing 10, the displacer unit 4 has a displacer 15 that is movable along a displacer axis 16, when the driving unit 2 supplies a corresponding gas pressure impulse via a connection 17 that is connected to the pipe 5.

The displacer 15 is guided in a cylinder 18. The cylinder 18 is connected to the displacer housing 10 via a foot 19. The foot 19 comprises several openings 20, through which the gas from the connection 17 can enter the intermediate space between the cylinder 18 and the displacer housing 10. This intermediate space comprises a first heat exchanger 21 , a regenerator 22 and a second heat exchanger 23. The heat exchangers 21 , 23 serve the purpose of discharging heat from the passing gas to the displacer housing 10. The regenerator 22 stores heat for a short period.

Here, the Stirling process runs as follows: Gas supplied to the displacer housing 10 through the pipe 5 and the connection 17, is pushed through the regenerator 22. In this connection, the gas has a constant mass. The regenerator 22 adopts heat from the gas. The temperature decreases. The volume remains unchanged (first isochoric state change). The gas on the cold side of displacer housing 10, now having a lower temperature, adopts heat from the environment. It volume increases at constant temperature (first isothermal state change). The displacer 15 is displaced in the direction towards the connection 17 under enlargement of an expansion chamber 24. This activates a resonance spring 25. The return movement of the displacer 15 causes gas from the expansion chamber 24 to flow through the regenerator 22 again, where it adopts the stored heat. The temperature increases. The volume remains constant (second isochoric state change). At unchanged temperature and under reduction of the volume, the gas then discharges heat to the environment on the hot side of the displacer housing 10 (second isothermal state change). The required driving power for the displacer is supplied by the driving unit 2 in the form of pressure impulses, as explained below.

As can be seen from Fig. 1 , the displacer axes 16 of the two displacer ar- rangements 3, 4 correspond. As the two displacer units in the displacer arrangements 3, 4 are acted upon in the same manner by pressure impulses via the pipe 5, they work in counterphases, that is, they move away from each other at the same time or in the direction of each other at the same time. This gives rise to reaction forces that act upon the displacer housings 9, 10, but equalise each other, as they have the same size and work in opposite directions. Thus, it can be avoided that the reaction forces of the dis- placers 15 cause a vibration of the cooling arrangement.

The driving unit 2 comprises a cylinder 26, in which two pistons 27, 28 are arranged to move along a piston axis 29. Each piston 27, 28 is connected to an armature 30, 31 of a linear motor, each linear motor comprising a coil arrangement 32, 33. Acting accordingly upon the two coil arrangements 32, 33 with electrical current will cause that the two armatures 30, 31 and thus also the two pistons 27, 28 are moved in exact counterphase to one another. When the two pistons 27, 28 are moving towards each other, gas is displaced through the pipe 5 to the displacer arrangements 3, 4. When the two pistons are moving away from each other, gas is sucked in again from the displacer arrangements 3, 4.

In the same manner as with the displacers 15, the counterphase movement of the similarly designed pistons 27, 28 causes that reaction forces generated by the pistons 27, 28 and the elements connected to them have the same size and opposite directions. These reaction forces then equalise each other, so that also the operation of the driving unit generates no vibrations or only very small vibrations.

Fig. 1 is a schematic view of the axes x, y, z of a cathesic coordinate system. In this connection, the axis x extends from the left to the right, the axis y from the bottom upwards and the axis z is perpendicular to the drawing plane. It can be seen that the displacer axis 16 is in the x-y plane, whereas the piston axis 29 is in the y-z plane. These two planes are perpendicular to one another, so that the reaction forces, if they should still exist, cannot influence each other mutually. The displacer axis 16 and the piston axis 29 do not intersect each other. This also contributes to a decoupling. Thus, the operation of the cooling arrangement can take place completely without, or at least almost completely without, vibrations.

Fig. 4 shows a modified embodiment, in which the same elements are provided with the same reference numbers. The embodiment of the cooling arrangement according to Fig. 4 comprises three displacer arrangements 3, 4, 34, the displacer axis 16a, 16b of the displacer arrangements 3, 4 enclosing an angle of 90° in relation to one another. A displacement axis 16c of the displacer arrangement 34 encloses and angle of 45° with each of the two displacer axes 16a, 16b. Otherwise, the displacer arrangement 34 has the same design as the displacer arrangements 3, 4.

When moving the displacer in the displacer arrangement 3, reaction forces occur, which can be subdivided in two components Fax, Fay. When moving the displacer in the displacer arrangement 4, reaction forces occur, which can be subdivided in two components Fbx, Fby. The components Fax, Fbx have the same size. Thus, the resulting sum of the reaction forces in the x direction is 0. An oscillation of the cooling arrangement 1 according to Fig. 4 in the x direction is thus not caused by the displacer arrangements 3, 4, 34.

The driving unit 2 can be turned around the y-axis by 90° in relation to the view in Fig. 4, so that the driving unit 2 has the same alignment as in Fig. 1. As, however, it can with a high certainty be assumed that, due to the pistons 27, 28 working in counterphase, the driving unit 2 does not generate oscillations either, the alignment of the driving unit 2 is of inferior importance.

Claims

Patent Claims

1. Stirling cooling arrangement with a driving unit and a displacer ar- rangement that is connected to the driving unit via a gas pipe, characterised in that the displacer arrangement (3, 4) comprises at least two displacers (15), whose movements are adapted to each other.

2. Cooling arrangement in accordance with claim 1 , characterised in that at least two displacers (15) are movable in counterphase to one another with at least one spatial direction component.

3. Cooling arrangement in accordance with claim 2, characterised in that two displacers (15) are movable along the same displacer axis.

4. Cooling arrangement in accordance with one of the claims 1 to 3, characterised in that the displacers (15) are arranged in different displacer housings (9, 10).

5. Cooling arrangement in accordance with claim 4, characterised in that the displacer housings (9, 10) are connected to the driving unit (2) through equal pipes (6, 7; 6, 8).

6. Cooling arrangement in accordance with claim 4 or 5, characterised in that the driving unit (2) is made as a piston pump with at least one piston (27, 28) to be movable along a piston axis (29), the piston axis (29) having a different spatial direction than the displacement axis (16), along which the displacers (15) are movable.

7. Cooling arrangement in accordance with claim 6, characterised in that the displacer axis is arranged in a first plane (x-y) that is perpendicular to a second plane (y-z), in which the piston axis (29) is arranged.

8. Cooling arrangement in accordance with claim 6 or 7, characterised in that the displacer axis (16) and the piston axis (29) extend without intersecting each other.

9. Cooling arrangement in accordance with one of the claims 4 to 8, characterised in that each displacer housing (9, 10) is guided through a leg (13, 14) of an isolating plate (11) having a U-shape.

10. Cooling arrangement in accordance with claim 9, characterised in that the piston axis (29) extends in parallel with the legs (13, 14).