VALVE FOR AN ADSORPTION HEAT PUMP AND USE OF THE VALVE IN AN ADSOPRTION HEAT PUMP

Abstract

A valve for an adsorption heat pump may include a first channel, a second channel, a third channel, a first valve unit, and a second valve unit. The first valve unit may include a first valve body and a first valve seat and may be constructed and arranged to open and close the first channel. A second valve unit may include a second valve body and a second valve seat and may be constructed and arranged to open and close the second channel. A spring element may be pre-stressed between the first valve body and the second valve body and may be constructed and arranged to provide a first closing force upon the first valve body in a first direction of the first valve seat and a second closing force upon the second valve body in a second direction of the second valve seat. An actuating drive may include a control rod and may extend through the first valve body and the second valve body. A first carrier element and a second carrier element may each be secured to the control rod. The first valve body, the second valve body, and the spring element may be positioned between the first carrier element and the second carrier element. The valve may be constructed and arranged to move between a closed position, a first open position, a second open position, and at least one intermediate position. In the closed position, the first valve unit and the second valve unit may be closed. In the first open position, the first valve unit may be fully open. In the second open position, the second valve unit may be fully open. In the at least one intermediate position, one of the first valve unit or the second valve unit may be partially open. The actuating drive may be constructed and arranged to hold the valve in the closed position, the first open position, the second open position, and the at least one intermediate position without power. The actuating drive may include a stepping motor and a gear unit. The stepping motor and the gear unit may be constructed and arranged to hold the valve in the closed position, the first open position, the second open position, and the at least one intermediate position via a currentless holding moment. The first valve unit and the second valve unit may include a valve opening characteristic of a flow coefficient dependent on an adjustment path which may not be linear. The valve opening characteristic may include at least one flat region.

Claims

1. A valve for an adsorption heat pump comprising: a first channel, a second channel, and a third channel; a first valve unit including a first valve body and a first valve seat, wherein the first valve unit is constructed and arranged to open and close the first channel; a second valve unit including a second valve body and a second valve seat, wherein the second valve unit is constructed and arranged to open and close the second channel; a spring element pre-stressed between the first valve body and the second valve body, wherein the spring element is constructed and arranged to provide a first closing force upon the first valve body in a first direction of the first valve seat, and a second closing force upon the second valve body in a second direction of the second valve seat; an actuating drive having a control rod, wherein the control rod extends through the first valve body and the second valve body; a first carrier element and a second carrier element each secured to the control rod, wherein the first valve body, the second valve body, and the spring element are positioned between the first carrier element and the second carrier element; wherein the valve is constructed and arranged to move between a closed position, a first open position, a second open position, and at least one intermediate position; wherein in the closed position, the first valve unit and the second valve unit are closed; wherein in the first open position, the first valve unit is fully open; wherein in the second open position, the second valve unit is fully open; wherein in the at least one intermediate position, one of the first valve unit or the second valve unit is partially open; wherein the actuating drive is constructed and arranged to hold the valve in the closed position, the first open position, the second open position, and the at least one intermediate position without power; wherein the actuating drive includes a stepping motor and a gear unit, wherein the stepping motor and the gear unit are constructed and arranged to hold the valve in the closed position, the first open position, the second open position, and the at least one intermediate position via a currentless holding moment; wherein the first valve unit and the second valve unit have a valve opening characteristic of a flow coefficient dependent on an adjustment path that is not linear; and wherein the valve opening characteristic includes at least one flat region.

2. The valve according to claim 1, wherein the actuating drive comprises a stepping motor linear drive.

3. The valve according to claim 1, wherein the actuating drive includes a plurality of centering elements constructed and arranged to center the control rod within the first valve body and the second valve body.

4. The valve according to claim 3, wherein the plurality of centering elements comprise a plurality of spring lugs on the first carrier element and the second carrier element.

5. The valve according to claim 1, wherein the valve opening characteristic includes a gradient varying over the adjustment path.

6. The valve according to claim 1, wherein the gradient of the valve opening characteristic further rises with a rising adjustment path.

7. The valve according to claim 1, wherein at least one of the first valve body and the second valve body includes a valve surface, and wherein the valve surface extends at an angle in relation to a valve axis of the at least one first valve body and the second valve body and varies in an axial direction.

8. The valve according to claim 1, wherein the first channel, the second channel, and the third channel each open into a central chamber.

9. An adsorption heat pump with a valve according to claim 1, wherein the valve is constructed and arranged to switch between a high temperature heat carrier and a medium temperature heat carrier.

10. The valve according to claim 3, wherein the plurality of centering elements further center at least one of the first valve body and the second valve body.

11. The valve according to claim 1, wherein the first carrier element and the second carrier element extend radially outward from the control rod.

12. The valve according to claim 1, wherein the flat region is a step.

13. A valve for an adsorption heat pump comprising: a first channel, a second channel, and a third channel, and wherein the first channel, the second channel, and the third channel each open into a central chamber; a first valve unit including a first valve body and a first valve seat, wherein the first valve unit is constructed and arranged to open and close the first channel; a second valve unit including a second valve body and a second valve seat, wherein the second valve unit is constructed and arranged to open and close the second channel; wherein at least one of the first valve body and the second valve body includes a valve surface, and wherein the valve surface extends at an angle in relation to a valve axis of the at least one first valve body and the second valve body and varies in an axial direction; a spring element pre-stressed between the first valve body and the second valve body, wherein the spring element is constructed and arranged to provide a first closing force upon the first valve body in a first direction of the first valve seat, and a second closing force upon the second valve body in a second direction of the second valve seat; an actuating drive having a control rod, wherein the control rod extends through the first valve body and the second valve body, and wherein the actuating drive includes a plurality of centering elements constructed and arranged to center the control rod within the first valve body and the second valve body; a first carrier element and a second carrier element each secured to the control rod, wherein the first valve body, the second valve body, and the spring element are positioned between the first carrier element and the second carrier element; wherein the valve is constructed and arranged to move between a closed position, a first open position, a second open position, and at least one intermediate position; wherein in the closed position, the first valve unit and the second valve unit are closed; wherein in the first open position, the first valve unit is fully open; wherein in the second open position, the second valve unit is fully open; wherein in the at least one intermediate position, one of the first valve unit or the second valve unit is partially open; wherein the actuating drive is constructed and arranged to hold the valve in the closed position, the first open position, the second open position, and the at least one intermediate position without power; and wherein the actuating drive includes a stepping motor and a gear unit, wherein the stepping motor and the gear unit are constructed and arranged to hold the valve in the closed position, the first open position, the second open position, and the at least one intermediate position via a currentless holding moment.

14. The valve according to claim 13, wherein the actuating drive comprises a stepping motor linear drive.

15. The valve according to claim 13, wherein the carrier elements extend radially outward from the control rod.

16. The valve according to claim 13, wherein the plurality of centering elements further center at least one of the first valve body and the second valve body.

17. The valve according to claim 13, wherein the plurality of centering elements comprise a plurality of spring lugs on the first carrier element and the second carrier element.

18. The valve according to claim 13, wherein the first valve unit and the second valve unit have a valve opening characteristic of a flow coefficient dependent on an adjustment path that is not linear and includes at least one flat region.

19. The valve according to claim 18, wherein the valve opening characteristic includes a gradient varying over the adjustment path.

20. The valve according to claim 18, wherein the flat region is a step.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] There are shown, respectively diagrammatically

[0030] FIG. 1 illustrates a schematic diagram of an adsorption heat pump;

[0031] FIG. 2 illustrates a schematic diagram of a sorption module of the adsorption heat pump;

[0032] FIG. 3 illustrates an example arrangement of three sorption modules;

[0033] FIG. 4 illustrates a temperature profile in the sorption phase, in the adsorption phase, in the desorption phase and on a change from the adsorption phase to the desorption phase;

[0034] FIG. 5 illustrates a basic sectional illustration through a valve according to the invention;

[0035] FIG. 6a-e illustrate different positions in which a valve according to the invention can be situated;

[0036] FIG. 7 illustrates a valve opening characteristic with a progressive course;

[0037] FIG. 8a-c illustrate an enlarged illustration of the region A of FIG. 5 with three different positions of a valve unit of the valve;

[0038] FIG. 9a,b illustrate an enlarged illustration of the region A of FIG. 5 to clarify the course of the valve surface;

[0039] FIG. 10 illustrates a valve opening characteristic of a valve with a step;

[0040] FIG. 11a,b illustrate an enlarged illustration of the region A in a different embodiment of the valve with a step-shaped characteristic, as is illustrated in FIG. 10.

DETAILED DESCRIPTION OF THE DRAWINGS

[0041] An adsorption heat pump 10 illustrated in FIG. 1 has a high temperature heat source 12, a medium temperature heat sink 14 and a low temperature heat source 16. In addition, the adsorption heat pump 10 has at least one, for example three, sorption modules 18. The at least one sorption module 18, illustrated by way of example in FIG. 2, comprises a sorption zone 20, which contains a sorption means 22 and is heated and cooled in alternation. In a desorption phase of the sorption zone 20, the sorption zone 20 is heated by the high temperature heat source 12 and in an adsorption phase the sorption zone 20 is cooled by the medium temperature heat sink 14. Furthermore, the sorption module 18 has a phase change zone 24, in which a working medium 26 can condense and vaporize. The sorption module 18 has a fluid connection 19 between the phase change zone 24 and the sorption zone 20, through which the working medium 26 can arrive from the phase change zone 24 to the sorption zone 20 and back.

[0042] The high temperature heat source 12 controls the temperature of a high temperature heat carrier 28, which circulates in a high temperature circuit 30. The high temperature circuit has a high temperature feed 32, in which the high temperature heat carrier 28 is directed to the at least one sorption module 18, and a high temperature return 34, via which the high temperature heat carrier 28 is returned to the high temperature heat source 12.

[0043] The high temperature heat source 12 has a temperature above the ambient temperature, preferably over 80 C., particularly preferably over 100 C., for example 110 C. The high temperature heat source 12 can represent a waste heat source from any desired energy conversion- or valued-added processes or else can obtain the thermal energy, from chemical energy, for example by combustion, or from cost-free solar energy.

[0044] The medium temperature heat sink 14 cools a medium temperature heat carrier 36, which circulates in a medium temperature circuit 38. The medium temperature circuit 38 has a medium temperature feed 40, into which the medium temperature heat carrier 36 is directed from the medium temperature heat sink 14 to the sorption module 18. Furthermore, the medium temperature circuit 38 has a medium temperature return 42, via which the medium temperature heat carrier 36 can be directed from the at least one sorption module 18 back to the medium temperature heat sink 14.

[0045] The temperature of the medium temperature heat sink 14 corresponds approximately to the ambient temperature. The temperature is actually somewhat greater than the ambient temperature, so that via a heat exchanger, thermal energy can be emitted from the medium temperature circuit 38 to the environment. For this, the medium temperature heat sink 14 has a cooler, for example a water- or air cooler.

[0046] The low temperature heat source 16 controls the temperature of a low temperature heat carrier 44, which circulates in a low temperature circuit 46. The low temperature circuit 46 has a low temperature feed 48, in which the low temperature heat carrier 44 is directed to the at least one sorption module 18. Furthermore, the low temperature circuit 46 has a low temperature return 50, in which the low temperature heat carrier 44 is directed from the at least one sorption module 18 back to the low temperature source 16.

[0047] The temperature of the low temperature heat source 16 lies below the ambient temperature and serves for the cooling, for example, of vehicles, buildings or a refrigerator or similar. When something is cooled by means of the low temperature heat carrier 44, this is heated in the low temperature heat source 16, hence the designation source.

[0048] In the case of a heat pump application, the low temperature heat source 16 can also be formed by the environment in the form of external air, geothermal heat or solar heat, the heat of which is received at low temperature and is emitted via the medium temperature circuit 14 at a higher heating temperature level for heating a room or a building. In this case, the high temperature heat source 12 is produced by a combustion process of a chemical energy carrier, the thermal energy of which is likewise used for heating at the temperature level of the medium temperature circuit 14.

[0049] The sorption modules 18 have a first flow channel 52, which is in thermal contact with the sorption zone 20, in particular with the sorption means 22. Thereby, a heat carrier, which flows through the first flow channel 52, can control the temperature of the sorption means. Furthermore, the sorption modules 18 have a second flow channel 54, which is in thermal contact with the phase change zone 24, so that the phase change zone 24 can be temperature-controlled by a heat carrier which flows through the second flow channel 54.

[0050] For each sorption module 18, the adsorption heat pump 10, as illustrated by way of example in FIG. 2, has a plurality of valves 56, for example four, therefore a first valve 77, a second valve 79, a third valve 80 and a fourth valve 84. With the valves 56, the two flow channels 52, 54 are connected to the circuits 30, 38 and 46.

[0051] The valves 56, as illustrated for example in FIG. 5, have respectively a first connection 58, a second connection 60 and a third connection 62. A first channel 64 extends from the first connection 58, a second channel 66 extends from the second connection 60, and a third channel 68 extends from the third connection 62. The three channels 64, 66 and 68 open in a central chamber 69, via which a fluidic connection between the three channels is produced or is able to be produced.

[0052] The valves 56 make possible a plurality of switching positions, as are illustrated by way of example in FIG. 6a-e. In a closure position 70, the first channel 64 and the second channel 66 are closed, so that no fluidic connection is present between the individual channels. In a first open position 72, the first channel 64 is open and the second channel 66 is closed, so that a first fluidic connection 71 exists between the first channel 64 and the third channel 68. In a second open position 74, the second channel 66 is open and the first channel 64 is closed, so that a second fluidic connection 73 exists between the second channel 66 and the third channel 68. Furthermore, the valves 56 have at least one intermediate position 75, in which the first channel 64 or the second channel 66 is partially open. Thereby, a throttled fluidic connection exists between the first channel 64 and the third channel 68 or between the second channel 66 and the third channel 68.

[0053] Via the first valve 77 of the valves 56 an inlet 76 of the first flow channel 52 is connected to the high temperature supply 32 and the medium temperature feed 40. Here, the third connection 62 is connected to the inlet 76 of the first flow channel 52, so that the third channel 68 of the first valve 77 is fluidically connected to the inlet 76 of the first flow channel 52. The first connection 58 is connected to the high temperature feed 32, and the second connection 60 is connected to the medium temperature feed 40. Thereby, the first flow channel 52 of the sorption module 18 can be switched over between the high temperature feed 32 and the medium temperature feed 40 and thereby a heating phase and a cooling phase can be switched over.

[0054] In the desorption phase, in which the sorption means 22 is to be heated, a fluidic connection is produced between the inlet of the first flow channel 52 and the high temperature feed 32. In the adsorption phase, the first valve is switched such that a fluidic connection is produced between the first flow channel 52 and the medium temperature feed 40, so that the sorption means 22 can be cooled by the medium temperature heat carrier 36.

[0055] An outlet 78 of the first flow channel 52 is connected via the second valve 79 of the valves 56 to the high temperature return 34 and the medium temperature return 42. Here, the third connection 62 of the second valve 79 is connected to the outlet 78 of the first flow channel 52, and the first connection 58 of the second valve 79 is connected to the high temperature return 34, and the second connection 60 of the second valve 79 is connected to the medium temperature return 42. This second valve 79 is switched in accordance with the first valve 77 in the desorption phase to the high temperature return 34 and in the adsorption phase to the medium temperature return 42.

[0056] Furthermore, the adsorption heat pump 10 has for each sorption module 18 the third valve 80, which connects an inlet 82 of the second flow channel 54 to the medium temperature feed 40 and to the low temperature feed 48. In a condensation phase, in which the working medium 26 condenses in the phase change zone 24, the third valve 80 is switched such that a fluidic connection exists between the second flow channel 54 and the medium temperature feed 40. Thus, the phase change zone 24 can be cooled by the medium temperature heat carrier 36. In a vaporization phase, the third valve 80 is switched such that a fluidic connection exists between the second flow channel 54 and the low temperature feed 48. Thereby, in the vaporization phase, the working medium 26 vaporizing in the phase change zone 24 can receive heat from the low temperature heat carrier 44 and thereby cool it.

[0057] In addition, the adsorption heat pump has for each sorption module the fourth valve 84, which connects an outlet 86 of the second flow channel 54 to the medium temperature return 42 and to the low temperature return 50. In accordance with the third valve 80, the fourth valve 84 in the condensation phase switches a fluidic connection between the second flow channel 54 and the medium temperature return 42, and in the vaporization phase a fluidic connection between the second flow channel 54 and the low temperature return 50.

[0058] During operation of the adsorption heat pump 10, the sorption modules 18 are operated cyclically. The desorption phase and the adsorption phase alternate. In the adsorption phase, the first valve 77 and the second valve 79 are switched such that the sorption zone 20 is cooled by the medium temperature heat carrier 36. Thereby, the sorption means 22 can adsorb the working medium 26, whereby the pressure within the sorption module 18 is reduced. Thereby, the liquid working medium 26, localized in the phase change zone 24, can vaporize, whereby the working medium 26 can receive thermal energy. Thereby, the phase change zone 24 is cooled. Through the cooling of the phase change zone, thermal energy can be accordingly received from the low temperature heat carrier 44, whereby the latter is cooled.

[0059] For this, in the vaporization phase the third valve 80 and the fourth valve 84 are switched such that the low temperature heat carrier 44 flows through the second flow channel 54 and thereby is in thermal contact with the phase change zone 24. The adsorption phase takes place accordingly substantially simultaneously with the vaporization phase, in which the desired effect, namely of the cooling of the low temperature heat carrier 44, is achieved. This phase is also named the useful phase.

[0060] In a regeneration phase, on the other hand, the sorption zone 20 is heated, so that the desorption phase of the sorption zone 20 is initiated. This is achieved in that the first valve 77 and the second valve 79 are switched such that the high temperature heat carrier 28 flows through the first flow channel 52 and therefore is in thermal contact with the sorption means 22 and can heat the latter. Thereby, the sorption means 22 delivers the working medium 26, so that the pressure in the sorption module 18 rises and therefore the working medium 26 can condense.

[0061] In order to condense the working medium 26 in the phase change zone 24, in the thereby initiated condensation phase, the third valve 80 and the fourth valve 84 are switched such that the medium temperature heat carrier 36 flows through the second flow channel 54 and is therefore in thermal contact with the phase change zone 24 and can cool this. Thereby, it can be achieved that the working medium 26 condenses in the phase change zone 24 and is available there in the useful phase for vaporization.

[0062] On a changeover from the regeneration phase to the useful phase and vice versa, the sorption zone 20 must be brought from the desorption phase into the adsorption phase or vice versa, and the phase change zone 24 from the condensation phase to the vaporization phase or vice versa. These are distinguished respectively by a considerable temperature difference, so that through a simple simultaneous switching over of the respectively corresponding valves 77 and 79 and 80 and 84 between the regeneration phase and the useful phase as a result of the sensitive heat capacities, considerable amounts of heat are diverted into the respectively complementary circuit. Thereby, in particular, high temperature heat is lost from the high temperature heat source 12 to the medium temperature heat sink 14 and from the latter to the low temperature heat source 16.

[0063] In order to reduce the respective heat losses, during the transition between the regeneration phase and the useful phase and vice versa, so-called cross-connections are set, in which for example the first flow channel 52 is connected at the inlet side to the high temperature feed 32 and at the outlet side to the medium temperature return 42. Thereby, on a changeover between the phases, the unproductive diversion of heat from a circuit of higher temperature into a circuit of lower temperature can be reduced.

[0064] On the changeover from the adsorption phase to the desorption phase, the high temperature heat carrier 28 heats the sorption zone 20. Thereby, the high temperature heat carrier 28 cools down. This lost heat must be applied, but does not bring about any thermal pumping output. Consequently the efficiency is thereby reduced.

[0065] When the high temperature heat carrier 28 flows slowly through the first flow channel 52, the high temperature heat carrier cools down approximately to the temperature of the sorption zone 20, namely the temperature of the medium temperature heat carrier 36. In the sorption zone 20, a temperature gradient 85 then forms, wherein on the inlet side the temperature can be at the temperature 87 of the high temperature heat carrier 28 and on the outlet side the temperature of the sorption zone 20 can be at the temperature 89 of the medium temperature heat carrier 36, as is shown for example in FIG. 4. During the temperature change phase, the temperature gradient 85 shifts from an inlet side 81 of the sorption zone 20 up to an outlet side 83 of the sorption zone 20, so that during almost the entire temperature change phase from adsorption to desorption, the high temperature heat carrier 28, which emerges from the first flow channel 52, has the temperature 89 of the medium temperature heat carrier 36. Thereby, it is expedient to return the high temperature heat carrier 28, cooled in the sorption zone 20, into the medium temperature circuit 38 instead of into the high temperature circuit 30.

[0066] Accordingly, on a changeover form the desorption phase to the adsorption phase, therefore on a cooling of the sorption zone 20, the heat which is stored in the sorption module 18 can be returned through a corresponding cross-connection into the high temperature circuit 30. Thereby, the thermal energy which was withdrawn from the high temperature circuit 30 during the heating of the sorption zone 20, is returned again during cooling of the sorption zone 20. Consequently, the harmful diverting of heat during the temperature changeovers can therefore be reduced.

[0067] This effect can be utilized particularly efficiently when during a temperature change phase the heat carrier flows only in a throttled manner through the first flow channel 52.

[0068] Through these cross-connections, volume flows are shifted to and from the high temperature circuit 30 to the medium temperature circuit 38 and vice versa. For this, for example, compensating reservoirs can come into use, which permit a temporary mass displacement between two circuits. Over one cycle, however, the displacements balance out. Furthermore, when a plurality of sorption modules are used, these are usually used in a phase-shifted manner, so that the displacement of the heat carriers between the circuits also balances out at any moment. This is the case in particular when the cross-connection phases of two modules, which are switched over in a complementary manner, take place simultaneously, for an equal length and with the same volume flow. In practice, several of these provisions can also be combined.

[0069] Through a corresponding connecting of the third valve 80 and fourth valve 84, heat can also be recovered from the phase change zone 24 at the temperature changeovers. As the phase change zone 24 is also heated or cooled by the phase change of the working medium 26, only a small portion of the heat can be recovered. The greater the heat output through the phase change compared to the heating output through the heat carrier, the less heat can be recovered. Therefore, a greater flow speed of the heat carriers would be expedient. However, with too great a flow speed, the heat carrier can not fully assume the temperature of the phase change zone. Consequently, a compromise must be found, in which the flow speed of the heat carrier delivers the best result. Finely incrementable intermediate positions of the valves 56 are therefore advantageous.

[0070] The valves 56 have a first valve unit 88, with which the first channel 64 can be opened and closed. Thereby, the first valve unit 88 can control a fluidic connection between the first channel 64 and the third channel 68, so that a fluidic connection between the first connection 58 and the third connection 62 can also be controlled by the first valve unit 88. The first valve unit 88 has a first valve body 90 and a first valve seat 92. When the first valve body 90 is pressed into the first valve seat 92, the first valve body 90 closes the opening formed by the first valve seat 92 and therefore closes the first channel 64. When the first valve body 90 is raised from the first valve seat 92, an annular gap 94 forms between the first valve body 90 and the first valve seat 92, through which a fluid can flow. The valves 56 have respectively a spring element 96, which acts upon the first valve body 90 with a closing force which presses the first valve body 90 into the first valve seat 92.

[0071] In addition, the valves 56 have a second valve unit 98 with a second valve body 100 and a second valve seat 102. The second valve unit 98 is designed in accordance with the first valve unit 88 such that it can open and close the second channel 66 of the valves 56. The second valve seat 102 surrounds the flow cross-section of the second channel 66. When the second valve body 100 is pressed into the second valve seat 102, the second valve body 100 closes an opening formed by the second valve seat 102 and therefore also closes the second channel 66.

[0072] The second valve unit 98 can accordingly open and close the second channel 66. Thereby, the second valve unit 98 can control a fluidic connection between the third channel 68 and the second channel 66. Accordingly, a fluidic connection between the second connection 60 and the third connection 62 is controlled by the second valve unit 98.

[0073] The spring element 96 of the valves 56 also acts upon the second valve body 100 with a closing force which presses the second valve body 100 in the direction of the second valve seat 102.

[0074] The spring element 96 is arranged between the first valve body 90 and the second valve body 100, so that the spring element 96 can press both the first valve body 90 and also the second valve body 100 into the respective associated valve seat 92, 102, in order to close the respective valve units 88 and 98. Accordingly, the two valve units 88 and 98 are arranged lying opposite one another, so that the spring element 96 arranged between the first valve body 90 and the second valve body 100 can respectively exert a closing force on the valve bodies. The opening directions of the two valve units 88, 98 are accordingly in opposition.

[0075] The valves 56 have respectively an actuating drive 104 with a control rod 106 and with a drive 108, which drives the control rod 106. The control rod 106 engages through the first valve body 90 and the second valve body 100 and is mounted in a sliding manner in axial direction in the first valve body 90 and in the second valve body 100. In addition, the actuating drive 104 has a first carrier element 110 and a second carrier element 111, which are held securely on the control rod 106 and are arranged such that, between the two carrier elements 110, 111, the first valve body 90, the spring element 96 and the second valve body 100 are arranged.

[0076] The carrier elements 110, 111 have such a radial extent that, when the control rod 106 is displaced in axial direction, the first valve body 90 is raised by the first carrier element 110, or the second valve body 100 by the second carrier element 111, from the respective valve seat 92 or 102, and thereby accordingly the first channel 64 or the second channel 66 is opened.

[0077] The drive 108 is designed such that a holding moment, without power, of the drive 108 is sufficient in order to overcome the closing forces of the spring element 96, so that the actuating drive 104 can hold the first or the second valve unit 88, 98 in a position in which the first valve body 90 or the second valve body 100 is raised from the respective valve seat 92, 102. Thereby, the valve 56 can pause in an open position, therefore in a position in which either the first channel 64 or the second channel 66 is open, without consuming energy. This enables an energy-efficient control of the adsorption heat pump, whereby overall the efficiency of the adsorption heat pump is improved.

[0078] Accordingly, intermediate positions, in which the valve bodies 90, 100 are only partially raised from the respective valve seat 92, 102, can also be held in the position without power.

[0079] The drive 108 has, for example, a stepping motor 107 which, due to the type of construction, has a certain holding moment. By selection of a corresponding gear unit 109, in particular of the transmission of the gear unit 109, a holding moment of the actuating drive 104 can thereby be achieved, which is sufficient in order to hold the valve units in all positions without power, in particular in a currentless manner.

[0080] In addition, a gear unit can also be selected which is self-inhibiting. Thereby, likewise, the position of the valve units 88, 98 can not be altered by the spring force of the spring element 96 or compressive forces which act on the valve bodies 90, 100.

[0081] The force which the actuating drive 104 can exert is greater than the closing force exerted by the spring element 96 in addition to compressive forces caused by pressure differences between the third channel 68 and the first channel 64 or the second channel 66.

[0082] In addition, the actuating drive 104 has centering elements 112, which center the control rod 106 and thereby also the first valve body 90 and the second valve body 100, so that a precise positioning of the valve bodies 90, 100 to the respective valve seats 92, 102 is provided.

[0083] The centering elements 112 can be formed, for example, by spring lugs. In particular these spring lugs are arranged on the carrier elements 110, 111.

[0084] The two valve units 88 and 98 have respectively a valve opening characteristic 114, which defines a flow coefficient 116 of the respective valve unit depending on an adjustment path 118. The adjustment path 118 corresponds to the deflection of the respective valve bodies 90, 100 out from the respective valve seat 92, 102. The flow coefficient is provided by the following formula:

k.sub.v=Q(/p).sup.1/2,

[0085] wherein Q is the effective area with the regard to flow of the respective valve unit, is the density of the fluid, and p is the pressure gradient applying at the valve unit. The effective area with regard to flow takes into account here both the flow cross-section and also other geometric characteristics influencing flow.

[0086] Preferably, the two valve units 88, 98 and hence the valves 56 have a valve opening characteristic 114, which is not linear. In particular, the valve opening characteristic 114 has varying gradients.

[0087] In regions in which the valve opening characteristic 114 has a small gradient, therefore is flat, the flow coefficient 116 alters only slightly on a change of the adjustment path 118, compared to regions in which the valve opening characteristic 114 has a greater gradient and is therefore steeper.

[0088] By selection of the course of the valve opening characteristic 114, regions can therefore be reached in which the flow coefficient 116 can be adjusted particularly precisely.

[0089] In FIG. 7 for example a progressive valve opening characteristic 114 is illustrated. With small adjustment paths 118 and hence with small flow coefficients 116, the valve opening characteristic 114 is flat, so that over the adjustment path 118 and hence by the actuating drive 104 the flow coefficient 116 of the valve can be adjusted very precisely. This is advantageous in particular in the temperature change phases in which the flow speed of the respective heat carrier is to be small and is to be able to be adjusted as precisely as possible. In the region of high flow coefficients 116, the valve opening characteristic 114 is steeper. Thereby, the flow coefficient 116 can indeed no longer be adjusted so precisely, instead the required adjustment path 118 reduces in order to fully open the valve 56 or respectively the respective valve unit 88, 98.

[0090] The shape, in particular the course of the valve opening characteristic 114 is provided by the geometry of the valve bodies and of the valve seats. In particular, the course or the shape of a valve surface 120 of the valve bodies 90, 100 is relevant for the course of the valve opening characteristic 114. The valve bodies 90, 100 have respectively a rim 122, with which the valve bodies 90, 100 lie against the respective valve seats 92, 102 and thereby seal the opening. A seal 124 may possibly be provided, in order to improve the sealing effect.

[0091] Proceeding from the rim 122, the valve surface 120 extends axially in the closing direction of the respective valve unit and radially inwards. In particular, the valve surface 120 can be designed so as to be convex. The valve surface 120 projects into the valve seat 92, 102 in the respective valve unit, when the respective valve body 90, 100 lies in the valve seat.

[0092] When the valve body 90, 100 is partially raised out from the valve seat 92, 102, the annular gap 94 forms. The width of the annular gap is provided by the distance of the valve surface 120 to the respective valve seat 92, 102, in particular by the radial distance.

[0093] Through the fact that the valve surface 120 extends both in axial direction and also in radial direction inwards, the annular gap widens with an increasing adjustment path 118 of the respective valve bodies 90, 100 out from the valve seat 92, 102. The inclination of the valve surface 120, therefore an angle 127 to a valve axis 126, which corresponds substantially to an axis of the control rod 106 and also determines the direction of the adjustment path 118 of the two valve bodies 90, 100, determines the gradient of the valve opening characteristic 114. When the angle 127 of the valve surface 120 to the valve axis 126 is large, the gradient of the valve opening characteristic 114 is large. The gradient of the characteristic corresponds here approximately to the tangent of the angle 127 of the valve surface 120 to the valve axis 126.

[0094] If now the valve surface 120 is curved, for example convex, the valve surface 120 has an angle 127, varying in axial direction, to the valve axis 126. Thereby, the gradient of the valve opening characteristic 114 also varies depending on the adjustment path 118. Consequently, through adaption of the valve surface 120, the valve opening characteristic 114 can be adjusted.

[0095] In particular, the valve surface 120 has in the vicinity of the rim 122 a small angle 127 to the valve axis 126. This region is relevant for the valve opening characteristic 114, with small adjustment paths 118 of the respective valve body 90, 100 from the respective valve seat 92, 102. In regions which have a greater distance to the rim 122, the valve surface 120 has a greater angle 127 to the valve axis 126, so that with greater adjustment paths 118 the gradient of the valve opening characteristic 114 becomes greater.

[0096] In another variant of the valves 56, as are illustrated for example in FIG. 10, 11a and 11b, the valve opening characteristic 114 has steps 125, in particular a plateau region 128.

[0097] This can be expedient for example when a previously known defined flow coefficient 116 is to be reliably adjusted. By the plateau 128 a wide region is produced for the adjustment part 118, in which the desired flow coefficient 116 of the valve 56 is achieved. This can be achieved in that the valve bodies 90, 100 have a valve surface 120 with steps 130. In particular, the valve surfaces 120 have a region 132, in which the angle 127 to the valve axis 126 is very small, in particular 0. Alternatively, provision can also be made to adjust a negative angle 127, in order to achieve as flat a plateau 128 as possible.

[0098] Otherwise, this variant coincides with the previously described variant.