ADSORPTION APPARATUS COMPRISING A HEAT RECOVERY SYSTEM

Abstract

The invention relates to an adsorption machine, comprising at least a first and a second adsorber unit which are each connected to a forward motion (VL) and a return motion (RL), in order to supply heat from a heat transfer medium of the adsorber unit conducted through the forward motion (VL) to the adsorber unit or to remove said heat from the adsorber unit to the heat transfer medium; each adsorber unit works alternately in a desorption phase as a desorber, wherein heat is removed from the heat transfer medium to the desorber and in an adsorption phase as an adsorber, wherein heat is removed from the adsorber to the heat transfer medium; the adsorption machine comprises further at least two heat transfer medium circuits, namely a heating circuit with a heat source for heating up of the heat transfer medium, and a cooling circuit with a heat sink for cooling of the heat transfer medium. The invention is characterized in that a control unit is provided which switches the forward motions (VL) and the return motions (RL) individually alternately to the heating circuit and the cooling circuit in such a way that the return motion with the highest temperature always feeds its heat transfer medium to the heating circuit.

Description

The subject matter of the present invention is an adsorption machine, in particular an adsorption cooling machine for refrigeration.

Thermally driven adsorption machines on the basis of solid adsorption for heating and cooling purposes have been known for some time. In the process conventional working substance pairs—sorption material and adsorbate—such as for example zeolite and water are used. Adsorption machines with such a working substance pair are for example described with DE 198 34 696, DE 199 61 629, DE 100 38 636, DE 101 59 652 or DE 102 17 443.

Various technical demands are made on adsorption machines. Particularly important are the demands for a high thermal ratio, a high power density and an easy adjustability of the heat loss. The thermal ratio of the effective heat to the driving heat—here and in the following named Coefficient of Performance (COP)—depends essentially on the shares of the sorptive and of the sensitive heat transformation during an operating cycle. By sorptive transformation one understands the release of the sorption heat arising in the case of the adsorption of the working gas or the absorption of the sorption heat required for desorption, whereas the sensitive heat transformation describes the energy turnover which occurs in the case of the heating up or cooling down of the entire system.

In order to achieve particularly high thermal ratios more and more sophisticated systems were developed, wherein in particular through the arrangement of a multitude of adsorber units, which are permeated successively by the heat transfer medium and switched in a multitude of cycles, the highest possible heat recovery is strived for. By heat recovery one understands any recovery of heat—sorptive as well as sensitive—from the adsorption phase, wherein the recovered heat can be used for the desorption phase, in order hence to reduce the energy expenditure of external heat sources for the desorption.

Adsorption machines with two adsorber units are conventionally used for refrigeration. In these refrigerating machines the adsorber units work alternately as adsorbers or desorbers. The conventional control systems in the process work between the adsorption phases with heat recovery phases which partially conduct the heat energy of the adsorber unit that is still hot to the adsorber unit that is still cold. Through these heat recovery phases the energy present in the system is reused to a certain extent, so that less energy must be supplied from the outside. The efficiency of this heat recovery is thus critical for the efficiency of the entire adsorption machine.

Conventional control system concepts conduct the heat transfer medium during the heat recovery phase in parallel or serial fashion through both adsorbers. For this purpose additional components are required, for example reversing valves or pumps in the heat transfer medium circuit system. Moreover this heat transfer medium circuit is operated uncoupled from the other circuits. This leads to the pumps mostly connected externally to the adsorption machine not being able to send any volumetric flow through the system during the time of the heat recovery and must either be switched off or conducted past the system in a bypass. The disadvantages of these systems are the considerable technical expenditure, the susceptibility to failure and the high manufacturing and maintenance costs.

The invention is based on the object of specifying an adsorption machine and a method for heat recovery in an adsorption machine which are improved with regard to the named disadvantages. In particular the number of components should be reduced in comparison with the known adsorption machines without worsening the heat recovery, but rather possibly improving said heat recovery. In particular the heat recovery should be able to be performed without interruption of externally applied volumetric flows.

The object according to the invention is solved by an adsorption machine with the features of Claim 1 and a method with the features of Claim 12. The dependent claims describe advantageous and particularly expedient embodiments of the invention.

The adsorption machine according to the invention comprises in other words at least a first and a second adsorber unit, a heat transfer medium and at least two heat transfer medium circuits with a temperature difference ΔT_X, of which one heat transfer medium circuit is a heating circuit and the other heat transfer medium circuit is a cooling circuit. Each adsorber unit works in a first desorption phase as a desorber and works in a second adsorption phase as an adsorber, wherein the heat transfer medium exhibits a lower temperature in a return motion from a desorber than in a forward motion to the desorber, and the heat transfer medium exhibits a higher temperature in a return motion from an adsorber than in a forward motion to the adsorber.

Consequently the heat transfer medium is cooled from a forward motion in an adsorber unit working as a desorber, because heat is transferred from the heat transfer medium to the adsorber unit, and the heat transfer medium is heated up from a forward motion in an adsorber unit working as an adsorber, because heat is transferred from the heat transfer medium to the adsorber unit.

The heating circuit basically serves the purpose of transferring heat from a heat source which is connected to the heating circuit to the heat transfer medium so that said heat transfer medium can heat up the desorber. The cooling circuit basically serves the purpose of removing heat from the heat transfer medium by means of a heat sink so that said heat transfer medium can cool the adsorber.

The heating circuit can also be described as a high temperature circle (HT circle) and the cooling circuit can be described as a mean temperature circuit (MT circle). Accordingly by HT source the heat source of the heating circuit is meant and by MT sink the heat sink of the cooling circuit is meant, see FIG. 1.

The temperature difference between the high temperature circuit and the mean temperature circuit is presently termed as ΔT_X, wherein the temperature T_H corresponds to the upper limit of the temperature difference ΔT_X of the two heat transfer medium circuits. The temperature T_H is that temperature to which the heat transfer medium should be set in the high temperature circuit.

The temperature T_M corresponds to the lower limit of the temperature difference ΔT_X of the two heat transfer medium circuits and that temperature to which the heat transfer medium should be set in the mean temperature circuit.

Through the embodiment according to the invention an adsorption machine can be created whose heat recovery is at least as great as in the case of conventional adsorption machines and which in the process manages without the integration of additional components in the machine.

In particular the heat recovery of the adsorption machine according to the invention can take place as a subprocess integrated in the total process, wherein no volumetric flow interruption occurs. The heat recovery can take place solely with valves and in particular pumps, which are required for the sorption phases anyway.

In particular in an adsorption machine in accordance with the present invention provision is made that the temperature difference ΔT_X is at least 10° C. in particular at least 20° C. and especially preferably at least 25° C. In the process in particular provision can be made that the heat transfer medium in the high temperature circuit exhibits a temperature T_H of at least 70° C. and a maximum of 90° C., and in particular from 75 to 85° C. In principle the adsorption machine according to the invention or the method according to the invention is however suitable for any temperature differences and temperature level.

In an alternative embodiment of the invention an adsorption machine according to the invention can exhibit three heat transfer medium circuits, wherein the high temperature circuit exhibits a temperature difference ΔT_X to a second mean temperature circuit and exhibits a temperature ΔT_Y to a third lower temperature circuit, and wherein the temperature difference ΔT_Y is greater than the temperature difference ΔT_X.

With an adsorption machine according to the invention advantageously each adsorber unit is not firmly connected to a heat transfer medium circuit or assigned to it as usual, but rather is assigned to a heat transfer medium circuit dependent on its temperature in the return motion. This is in particular achieved as a result of the valves not both being positioned in the same direction in the forward and return motion of a component in a control phase, but rather having the position made dependent on the adjacent temperature level. In an adsorption machine according to the invention the valves can be positioned in the forward motion of both adsorber units at the beginning of the heat recovery phase in such a way that the “new” desorber receives the heat transfer medium from the high temperature circuit and consequently is heated up. The return motion of this “new” desorber, which is still cold, however continues to be conducted to the mean temperature circuit until the temperature level increases significantly, in particular by a preset extent or to a temperature equal to or above the return motion of the “old” desorber, which is the “new” adsorber. Similar to this the forward motion of the “new” adsorber is connected to the mean temperature circuit, so that this “new” adsorber is cooled. The return motion of the “new” adsorber, which is still hot, however continues to be connected to the high temperature circuit until the temperature level decreases significantly, in particular by a preset extent or to a temperature equal to or below the return motion of the “old” adsorber, which is the “new” desorber.

FIG. 1 shows a hydraulic diagram of an exemplifying embodiment of an adsorption machine according to the invention.

As one recognized in FIG. 1, the valves of the forward motion group ( . . . _VL_. . . ) are differently connected during the heat recovery than those of the return motion group ( . . . _RL_. . . ). One advantage of this adsorption machine consists in the fact that a heat recovery can take place without interruption of the external volumetric flows.

With this during the heat recovery, the heat transfer medium is conducted to the high temperature circuit at all times with the highest available temperature in the return motion of the system. As a result of this, on the one hand the energy which must be provided from the outside to the system is minimized and on the other hand through the embodiment of the adsorption machine it is also guaranteed that at all times the heat transfer medium will be conducted to the cooling circuit with the lowest temperature, so that the least possible energy must be recooled. In particular, the energy requirements are reduced when in accordance with an embodiment of the invention pumps, as they are described in the introductory part of the description with regard to the known control concepts, are conserved.

In particular an adsorption machine according to the invention comprises two adsorber units. These adsorption machines can in particular produce cold in a two-stage, cyclical process. In order to generate a continuous cold flow at least two adsorber units are counter connected, so that one adsorber unit is being dried while the other one produces cold. Fundamentally this process runs all the more effectively the more the sorption material has been dried previously—which in turn best succeeds with higher driving temperatures.

Accordingly an adsorption refrigerating machine is also the subject matter of the present invention. This adsorption refrigerating machine comprises at least two adsorber units, one heat transfer medium, at least two heat transfer medium circuits with a temperature difference ΔT_X and one control unit, wherein each adsorber unit works in a first desorption phase as a desorber and in a second adsorption phase works as an adsorber, and wherein the heat transfer medium in a return motion of the desorber exhibits a lower temperature than in the forward motion to the desorber and wherein the heat transfer medium in a return motion of the adsorber exhibits a higher temperature than in a forward motion to the adsorber, and wherein the heat transfer medium with the highest temperature in the return motion of the first or any further adsorber unit is connected to the high temperature circuit.

Along with the adsorption machine itself a method for heat recovery in an adsorption machine in accordance with Claim 12 is also the subject matter of the present invention. In especially preferred manner in the process the temperatures of the return motions are compared with each other and the return motion with the highest temperature is assigned to the high temperature circuit.

The operating cycle of an adsorption machine according to the invention can flow as follows. First minerals with a large inner surface, in particular zeolite or silica gels, are dried by heat supply during a desorption phase. When the material has been sufficiently dried the heat supply is stopped and a valve to a water container is opened. Due to the enormous inner surface and the special crystal structure there is a very great suction of water vapor or the evaporating of water in the second container. As is the case with any evaporation process there is now a great temperature decline in the water depending on the operating state up to the formation of ice.

In order to produce a continuous cold flow two such systems are counter connected so that one adsorber unit is drying while the other one is producing cold. Alternately the present adsorption machine can comprise three adsorber units or at least three adsorber units. In particular provision is made in the process that one adsorption machine comprises a maximum of five adsorber units. In principle however the output of the adsorber machine can be continuously expanded by the simple addition of further adsorber units.

With an adsorption machine in accordance with the present invention in particular by a reduction of the necessary pumps the current consumption and also the generation of noise can be significantly reduced. At the same time the electrical efficiency is improved. For example the adsorption machine can exhibit pumps exclusively in the external heat transfer medium circuits, that is between the heat sources and/or heat sinks and the adsorber units, for example a single pump per eternal circuit, as shown in FIG. 1. The adsorber units themselves can be designed free of pumps.

Waste heat or excess heat from existing systems can be used as a heat source, for example engine-based cogeneration systems, solar plants or process waste heat.

Claims

1. Adsorptive machine, comprising

at least a first and a second adsorber unit which are each connected to a forward motion (VL) and a return motion (RL), in order to supply heat from a heat transfer medium of the adsorber unit (1) conducted through the forward motion (VL) to the adsorber unit or to remove said heat from the adsorber unit to the heat transfer medium;

each adsorber unit works alternately in a desorption phase as a desorber, wherein heat is removed from the heat transfer medium to the desorber and in an adsorption phase as an adsorber, wherein heat is removed from the adsorber to the heat transfer medium;

the adsorption machine comprises further at least two heat transfer medium circuits, namely a heating circuit with a heat source for heating up of the heat transfer medium, and a cooling circuit with a heat sink for cooling of the heat transfer medium, wherein

a control unit is provided which switches the forward motions (VL) and the return motions (RL) individually alternately to the heating circuit and the cooling circuit in such a way that the return motion with the highest temperature always feeds its heat transfer medium to the heating circuit;

characterized in that the control unit is designed in such a way that in the transition of the first adsorber unit from the desorption phase to the adsorption phase and in the transition of the second adsorber unit from the adsorption phase to the desorption phase or vice versa first it connects the forward motion (VL) of the adsorber unit which is connected as the new desorber to the heating circuit so that the new desorber is fed from the heating circuit and thus heated up, and the return motion (RL) of this new desorber continues to be connected to the cooling circuit until the temperature level of the heat transfer medium in the return motion (RL) is increased by a preset extent, or is warmer than the return motion (RL) of the other adsorber unit, and the return motion (VL) of the new adsorber is connected to the cooling circuit so that this new adsorber is cooled and the still warm return motion (RL) of the new adsorber continues to remain connected to the heating circuit until the temperature of the heat transfer medium in the return motion (RL) has decreased by a predetermined extent, or up to or below the temperature of the return motion (RL) of the other adsorber unit.

2. The adsorption machine in accordance with claim 1 characterized in that the control unit is designed in such a way that it always switches the return motion (RL) with the lowest temperature in such a way that it feeds its heat transfer medium to the cooling circuit.

3. The adsorption machine according to claim 1, characterized in that a temperature difference ΔTX between the heating circuit and the cooling circuit amounts to at least 10° C. or at least 20° C. or at least 25° C.

4. The adsorption machine according to claim 1, characterized in that the adsorption machine comprises three heat transfer medium circuits.

5. The adsorption machine according to claim 4, characterized in that the third heat transfer medium circuit is a low temperature circuit and exhibits a temperature difference ΔTY to the heating circuit, wherein the temperature difference ΔTY is greater than the temperature difference ΔTX.

6. The adsorption machine according to claim 1, characterized in that the heat transfer medium with the lowest temperature is assigned to the low temperature circuit.

7. The adsorption machine according to claim 1, characterized in that the adsorption machine comprises at least three adsorber units.

8. The adsorption machine according to claim 1, characterized in that water, water vapor or oil is used as the heat transfer medium.

9. The adsorption machine according to claim 1, characterized in that each adsorber unit comprises zeolite as an adsorbing agent.

10. The adsorption machine according to claim 1, characterized in that the adsorption machine is a refrigerating machine.

11. A method for heat recovery in an adsorption machine comprising at least a first and a second adsorber unit which are each connected to a forward motion (VL) and a return motion (RL), in order to supply heat from a heat transfer medium of the adsorber unit conducted through the forward motion (VL) to the adsorber unit or to remove said heat from the adsorber unit to the heat transfer medium and further comprising at least two heat transfer medium circuits, namely a heating circuit with a heat source (3) for heating up of the heat transfer medium, and a cooling circuit with a heat sink (4) for cooling of the heat transfer medium, wherein

each adsorber unit works alternately in a desorption phase as a desorber, wherein heat is removed from the heat transfer medium to the desorber and in an adsorption phase as an adsorber, wherein heat is removed from the adsorber to the heat transfer medium; and

the forward motions (VL) and the return motions (RL) are switched individually alternately to the heating circuit and the cooling circuit in such a way that the return motion with the highest temperature always feeds its heat transfer medium to the heating circuit;

characterized in that in the transition of the first adsorber unit from the desorption phase to the adsorption phase and in the transition of the second adsorber unit from the adsorption phase to the desorption phase or vice versa first the forward motion (VL) of the adsorber unit which is connected as the new desorber is connected to the heating circuit so that the new desorber is fed from the heating circuit and thus heated up, and the return motion (RL) of this new desorber continues to be connected to the cooling circuit until the temperature level of the heat transfer medium in the return motion (RL) is increased by a preset extent, or is warmer than the return motion (RL) of the other adsorber unit, and the return motion (VL) of the new adsorber is connected to the cooling circuit so that this new adsorber is cooled and the still warm return motion (RL) of the new adsorber continues to remain connected to the heating circuit until the temperature of the heat transfer medium in the return motion (RL) has decreased by a predetermined extent, or up to or below the temperature of the return motion (RL) of the other adsorber unit.

12. The method in accordance with claim 11, characterized in that the return motion (RL) with the lowest temperature is always switched in such a way that it feeds its heat transfer medium to the cooling circuit.

13. The method in accordance with claim 12, characterized in that the switching of the forward motions (VL) and of the return motions (RL) takes place by means of a control unit which compares the temperatures of the return motions (RL) with each other.

14. The method in accordance with claim 11, characterized in that the switching of the forward motions (VL) and of the return motions (RL) takes place by means of a control unit which compares the temperatures of the return motions (RL) with each other.

15. The adsorption machine according to claim 2, characterized in that a temperature difference ΔTX between the heating circuit and the cooling circuit amounts to at least 10° C. or at least 20° C. or at least 25° C.

16. The adsorption machine according to claim 2, characterized in that the adsorption machine comprises three heat transfer medium circuits.

17. The adsorption machine according to claim 3, characterized in that the adsorption machine comprises three heat transfer medium circuits.

18. The adsorption machine according to claim 2, characterized in that the heat transfer medium with the lowest temperature is assigned to the low temperature circuit.

19. The adsorption machine according to claim 3, characterized in that the heat transfer medium with the lowest temperature is assigned to the low temperature circuit.

20. The adsorption machine according to claim 4, characterized in that the heat transfer medium with the lowest temperature is assigned to the low temperature circuit.