Waste-heat recovery system

Abstract

A waste-heat recovery system may include a waste-heat recovery circuit in which a working fluid is circulatable and which has a high pressure region and a low pressure region. The system may also include a conveying device configured to drive the working fluid, a steam generator configured to evaporate the working fluid, an expansion machine configured to expand the working fluid via mechanical work, at least one condenser configured to condense the working fluid, a container arranged downstream of the at least one condenser, and a divider arranged in a container interior of the container which may divide the container interior into a first sub-chamber and a second sub-chamber. The second sub-chamber may be Tillable with a coolant, which is introducible into the at least one condenser fluidically separately from the working fluid via a fluid line, such that the working fluid is condensable via thermal interaction with the coolant.

Claims

1. A waste-heat recovery system comprising: a waste-heat recovery circuit in which a working fluid is circulatable and which has a high pressure region and a low pressure region; a conveying device arranged in the waste-heat recovery circuit configured to drive the working fluid; a steam generator arranged in the high pressure region of the waste-heat recovery circuit configured to evaporate the working fluid; an expansion machine configured to expand the working fluid via mechanical work; at least one condenser arranged in the low pressure region of the waste-heat recovery circuit configured to condense the working fluid expanded via the expansion machine; a container arranged downstream of the at least one condenser; and a divider arranged in a container interior of the container, the divider dividing the container interior into a first sub-chamber and a second sub-chamber, each having a variable volume; wherein the first sub-chamber is fluidically connected to the low pressure region of the waste-heat recovery circuit downstream of the at least one condenser; and wherein the second sub-chamber is fillable with a coolant, which is introducible into the at least one condenser fluidically separately from the working fluid via a fluid line, such that the working fluid is condensable via thermal interaction with the coolant.

2. The waste-heat recovery system according to claim 1, wherein: the first sub-chamber is fluidically connected to the low pressure region of the waste-heat recovery circuit via a first pressure-relief valve; and the first pressure-relief valve is configured to open and release a fluid connection between the first sub-chamber and the low pressure region of the waste-heat recovery circuit when a pressure of the working fluid in the first pressure-relief valve exceeds a predetermined first threshold pressure.

3. The waste-heat recovery system according to claim 2, wherein the divider includes a dividing membrane composed of a resilient material configured to expand when the pressure of the working fluid in the first pressure-relief valve exceeds the predetermined first threshold pressure such that the working fluid is flowable into the first sub-chamber and is accommodatable in the first sub-chamber.

4. The waste-heat recovery system according to claim 2, further comprising a second pressure-relief valve arranged in the fluid line configured to open, when a pressure of the coolant in the second pressure-relief valve exceeds a predetermined second threshold pressure, such that the coolant is dischargeable from the fluid line via a fluid outlet into a surroundings of the waste-heat recovery system.

5. The waste-heat recovery system according to claim 1, wherein: the at least one condenser is structured as a triple-flow condenser including three fluid paths; the working fluid is flowable through a first fluid path of the three fluid paths, the coolant is flowable through a second fluid path of the three fluid paths, and an additional coolant is flowable through a third fluid path of the three fluid paths; and the three fluid paths respectively extend fluidically separately from one another in the at least one condenser and are thermally coupled to one another such that heat is exchangeable between the working fluid and the coolant and the additional coolants.

6. The waste-heat recovery system according to claim 1, wherein: the at least one condenser is structured as a double-flow condenser including two fluid paths; the working fluid is flowable through a first fluid path of the two fluid paths and at least one of the coolant and an additional coolant are flowable through a second fluid path of the two fluid paths; and the two fluid paths respectively extend fluidically separately from one another in the at least one condenser and are thermally coupled to one another such that heat is exchangeable between the working fluid and the at least one of the coolant and the additional coolant.

7. The waste-heat recovery system according to claim 6, wherein: the at least one of the coolant and the additional coolant flowable through the second fluid path includes both the coolant and the additional coolant; and the fluid line, outside of the at least one condenser, leads into the second fluid path.

8. The waste-heat recovery system according to claim 6, wherein: the at least one of the coolant and the additional coolant flowable through the second fluid path includes the coolant; an additional double-flow condenser including an additional first fluid path and an additional second fluid path is arranged in the low pressure region of the waste-heat recovery circuit; and the working fluid is flowable through the additional first fluid path and the additional coolant is flowable through the additional second fluid path.

9. The waste-heat recovery system according to claim 4, further comprising a non-return valve arranged fluidically parallel to the second pressure-relief valve configured such that the working fluid is flowable out of the container and back into the waste-heat recovery circuit when the coolant has escaped from the fluid line and when a pressure of the working fluid in the container exceeds a predetermined third pressure.

10. The waste-heat recovery system according to claim 1, wherein a temperature difference between an evaporating temperature of the coolant and a condensation temperature of the working fluid is at least 30 C.

11. The waste-heat recovery system according to claim 2, wherein the working fluid is at least one of ethanol, acetone, and cyclopentane and the predetermined first threshold pressure is approximately 10 bar.

12. The waste-heat recovery system according to claim 4, wherein the coolant includes water and the predetermined second threshold pressure is 1 bar to 1.5 bar.

13. The waste-heat recovery system according to claim 1, wherein the coolant includes at least one of glycol and salt.

14. The waste-heat recovery system according to claim 1, further comprising a temporary storage of a variable volume configured to temporarily store the working fluid arranged in the low pressure region of the waste-heat recovery circuit.

15. The waste-heat recovery system according to claim 1, wherein a temperature difference between an evaporating temperature of the coolant and a condensation temperature of the working fluid is at least 80 C.

16. The waste-heat recovery system according to claim 1, further comprising a fluid line pressure-relief valve arranged in the fluid line configured to open such that the coolant is dischargeable from the fluid line via a fluid outlet into a surroundings of the waste-heat recovery system when a pressure of the coolant in the fluid line pressure-relief valve exceeds a predetermined fluid line valve threshold pressure.

17. The waste-heat recovery system according to claim 16, further comprising a non-return valve arranged fluidically parallel to the fluid line pressure-relief valve configured such that the working fluid is flowable out of the container and back into the waste-heat recovery circuit when the coolant has escaped from the fluid line and a pressure of the working fluid in the container exceeds a predetermined container pressure.

18. A waste-heat recovery system comprising: a waste-heat recovery circuit in which a working fluid is circulatable and which has a high pressure region and a low pressure region; a conveying device arranged in the waste-heat recovery circuit configured to drive the working fluid; a steam generator arranged in the high pressure region of the waste-heat recovery circuit configured to evaporate the working fluid; an expansion machine configured to expand the working fluid via mechanical work; at least one condenser arranged in the low pressure region of the waste-heat recovery circuit configured to condense the working fluid expanded via the expansion machine; a container arranged downstream of the at least one condenser; a divider arranged in a container interior of the container, the divider dividing the container interior into a first sub-chamber and a second sub-chamber each having a variable volume; and a temporary storage of a variable volume configured to temporarily store the working fluid arranged in the low pressure region of the waste-heat recovery circuit; wherein the first sub-chamber is fluidically connected to the low pressure region of the waste-heat recovery circuit downstream of the at least one condenser via a first pressure-relief valve configured to open and release a fluid connection between the first sub-chamber and the low pressure region of the waste-heat recovery circuit when a pressure of the working fluid in the first pressure-relief valve exceeds a predetermined first threshold pressure; and wherein the second sub-chamber is fillable with a coolant, which is introducible into the at least one condenser fluidically separately from the working fluid via a fluid line, such that the working fluid is condensable via thermal interaction with the coolant.

19. The waste-heat recovery system according to claim 18, wherein the coolant includes water and at least one of glycol and salt.

20. A waste-heat recovery system comprising: a waste-heat recovery circuit in which a working fluid is circulatable and which has a high pressure region and a low pressure region; a conveying device arranged in the waste-heat recovery circuit configured to drive the working fluid; a steam generator arranged in the high pressure region of the waste-heat recovery circuit configured to evaporate the working fluid; an expansion machine configured to expand the working fluid via mechanical work; at least one condenser arranged in the low pressure region of the waste-heat recovery circuit configured to condense the working fluid expanded via the expansion machine; a container arranged downstream of the at least one condenser; and a divider arranged in a container interior of the container, the divider dividing the container interior into a first sub-chamber and a second sub-chamber each having a variable volume; wherein the first sub-chamber is fluidically connected to the low pressure region of the waste-heat recovery circuit downstream of the at least one condenser; wherein the second sub-chamber is fillable with a coolant, which is introducible into the at least one condenser fluidically separately from the working fluid via a fluid line, such that the working fluid is condensable via thermal interaction with the coolant; and wherein the divider includes a dividing membrane composed of a resilient material, the dividing membrane configured to expand such that the working fluid is flowable into the first sub-chamber and is accommodatable in the first sub-chamber when a pressure of the working fluid downstream of the at least one condenser exceeds a predetermined first threshold pressure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In each case schematically:

(2) FIG. 1 shows an example of a waste-heat recovery system according to the invention comprising a triple-flow condenser in schematic illustration.

(3) FIG. 2 shows a first alternative of the example of FIG. 1 comprising two double-flow condensers in a partial illustration,

(4) FIG. 3 shows a second alternative of the example of FIG. 1 comprising only one double-flow condenser.

DETAILED DESCRIPTION

(5) In schematic illustration, FIG. 1 shows an example of a waste-heat recovery system 1 according to the invention. The waste-heat recovery system 1 comprises a waste-heat recovery circuit 2, in which a working fluid A circulates and which is divided into a high pressure region 3 and into a low pressure region 4. In the waste-heat recovery circuit 2, a conveying device 5 in the form of a pump 6 is located, which serves to drive the working fluid A. A steam generator 7 for evaporating the working fluid A is furthermore located downstream of the conveying device 5, thus in the high pressure region 3. An expansion machine 8 for expanding the working fluid A by outputting mechanical work is located downstream of the steam generator 7. A condenser 9 for condensing the expanded working fluid A is located downstream of the expansion machine 9, thus in the low pressure region 4.

(6) A container 10, in the container interior 11 of which a divider 12 is provided, is located downstream of the condenser 9 in the low pressure region 4. Said divider 12 divides the container interior 11 in a fluid-tight manner into a first and a second sub-chamber 13a, 13b, each of a variable volume.

(7) The already mentioned conveying device 6 is located downstream of the container 10, such that the waste-heat recovery circuit 2 is closed.

(8) The divider 12 can be embodied as dividing membrane 19 of a flexible material. Preferably a resilient material. The divider 12, which is embodied as dividing membrane 19, can have an expanded state, which is shown in FIG. 1, in which the first sub-chamber 13a has a maximum volume and the second sub-chamber 13b has a minimal volume. However, the divider 12, which is embodied as dividing membrane 19, also has a relaxed state, in which the first sub-chamber 13a has a minimal volume and the second sub-chamber 13b has a maximum volume. For illustration purposes, the dividing member 19 or the divider 12, respectively, is suggested in FIG. 1 in dashed illustration in the relaxed state.

(9) The first sub-chamber 13a is connected to the low pressure region 4 of the waste-heat recovery circuit 2 downstream of the condenser 9 via a first pressure-relief valve 14a. The first pressure-relief valve 14a is embodied in such a way that, when a predetermined first threshold pressure p.sub.1 of the working fluid in the first pressure-relief valve 14a is exceeded, the latter switches from a closed state, in which a fluid connection for the working fluid A between the first sub-chamber and the low pressure region 4 is closed, into an open state. In the open state, the fluid connection between the first sub-chamber 13a and the low pressure region 4 is released for the flow-through with the working fluid A. If ethanol, acetone or cyclopentane is used as working fluid A, a value of approximately 10 bar can be selected as first threshold pressure p.sub.1.

(10) The second sub-chamber 13b of the container interior 11 is filled with a coolant K, which can be guided into the condenser 9 via a fluid line 15 fluidically separately from the working fluid. The working fluid A can be condensed in the condenser 9 by thermal interaction with the coolant K. Water, which can contain glycol or a salt, can be used as coolant K. The coolant K is thereby ideally selected in such a way that as much heat as possible can be discharged in response to the evaporation of said coolant.

(11) As can further be seen in FIG. 1, a second pressure-relief valve 14b is located in the fluid line 15. The second pressure-relief valve 14b is embodied in such a way that, when a predetermined second threshold pressure p.sub.2 of the coolant K in the second pressure-relief valve 14b is exceeded, the latter switches from a closed into an open state, such that the coolant K can be discharged from the fluid line 15 into the surroundings 16 of the waste-heat recovery system 1 via a fluid outlet 21. In an alternative, the second pressure-relief valve 14b can be forgone. In this case, the ambient pressure p.sub.2 of the surroundings 16 takes over the valve function of the pressure-relief valve 14b.

(12) If water with glycol or a salt is used as coolant K, as already proposed above, between 1 bar and 1.5 bar turns out to be particularly advisable as value for the second threshold pressure p.sub.2.

(13) In the example of FIG. 1, the condenser 9 is located between the second pressure-relief valve 14b and the container 10. In an alternative, which is not shown in the figures, the second pressure-relief valve 14b can, however, also be located between the condenser 9 and the container 10. In the example of FIG. 1, the condenser 9 is furthermore embodied for a simultaneous thermal interaction of the working fluid A with the coolant K from the container and with a further, additional coolant K*, for example with coolant water. The condenser 9 thus has three fluid paths 17a, 17b, 17c, which are fluidically separated from one another, for the working fluid, the coolant K introduced from the container 10 into the condenser 9 and said additional coolant K*.

(14) As can further be gathered from FIG. 1, a non-return valve 18 can be located fluidically parallel to the first pressure-relief valve 14a between the container 10 and the waste-heat recovery circuit 2. Said non-return valve 18 serves the purpose of making is possible that the working fluid A can flow from the first sub-chamber 13a of the container 10 back into the waste-heat recovery circuit 2, when coolant K has escaped from the fluid line 15 into the surroundings 16, thus in the case of a quasi emptied fluid line 15.

(15) In the case of this scenario, it is thus not required to fill the waste-heat recovery circuit 2 with further working fluid A. For this purpose, the non-return valve 18 opens in response to exceeding a predetermined, third pressure p.sub.3 of the working fluid A in the container 10 and thus also in the non-return valve 18, such that it is made possible for the working fluid A to flow back into the actual waste-heat recovery circuit 1. A temporary storage 20 of a variable volume for temporarily storing the working fluid A can be located in the low pressure region 4 of the waste-heat recovery circuit 2. An arrangement of the temporary storage 20 as shown in FIG. 1 downstream of the container 10 or of the condenser 9, respectively, and upstream of the conveying device 5 is in particular conceivable.

(16) The mode of the operation of the container 10 as well as of the two pressure-relief valves 14a, 14b in the waste-heat recovery system 2 is as follows:

(17) If the fluid pressure of the working fluid A downstream of the condenser 9 rises beyond the first threshold pressure p.sub.1, the first pressure-relief valve 14a opens and the working fluid A can flow into the first part 13a of the container in the form of steam. The divider 12 in the form of the dividing membrane 19 is expanded in this way, such that the volume of the first sub-chamber 13a increases and the volume of the second sub-chamber 13b is accordingly reduced by the same amount. The coolant K located in the second sub-chamber 13b is thereby pushed via the fluid line 15 into the condenser 9, where a heat exchange with the working fluid A takes place as well. The working fluid A is cooled in this way. Due to the different threshold pressures p.sub.1, p.sub.2 of the two pressure-relief valves 141, 14b, working fluid A, which is now liquid, continues to flow into the first sub-chamber 13a and continues to displace the coolant K from the second sub-chamber 13b. The condensation of the working fluid A in the condenser 9 still ensured in this way. If the coolant K in the second pressure-relief valve 14b exceeds the second threshold pressure p.sub.2, the second pressure-relief valve 14b opens and the coolant K can escape into the surroundings 16 of the waste-heat recovery circuit 2. Damages to the waste-heat recovery circuit 2 and in particular to the condenser 9 is avoided in this way.

(18) Due to the fact that the second pressure-relief valve 14b opens at a threshold pressure p.sub.2 in the pressure region between 1 bar and 1.5 bar, when the coolant is water, an evaporation of the water takes place at approximately 100 C. to 110 C. in the example scenario, an evaporation of the water takes place at approximately 100 C. to 110 C. when the coolant is water.

(19) Due to the fact that evaporation enthalpy is required for evaporating the coolant, a small mass of coolant K can absorb a relative large amount of heat, so that relatively little coolant K has to be stored in the condenser 9 or in the container 10, respectively. Due to the fact that the first threshold pressure p.sub.1 of the first pressure-relief valve 14a is approximately 10 bar, it can be attained that, when using ethanol, acetone or cyclopentane as working fluid A, the latter condenses at 150 C., while, as already described, the coolant K evaporates at approximately 100 C. to 110 C. This driving temperature difference of an evaporation temperature of the coolant K and of a condensation temperature of the working fluid A leads to a better heat transfer between working fluid A and coolant K and thus to an improved efficiency of the condenser 9 and thus of the entire waste-heat recovery circuit 2.

(20) The working fluid A and the coolant K are preferably selected in such a way and the two threshold pressures p.sub.1, p.sub.2 are determined in such a way that said temperature difference between an evaporation temperature of the coolant K and a condensation temperature of the working fluid A is at least 30 C., preferably at least 80 C. A particularly high heat transfer between the working fluid A and the coolant K can be ensured in this way, which has an advantageous effect on the efficiency of the waste-heat recovery system 1 and which in particular increases the operational safety, because an overpressure can be reduced largely without danger in the system in response to a malfunction.

(21) FIG. 2 shows a first alternative of the waste-heat recovery system 1 of FIG. 1. In the example of FIG. 2, two condensers 9a, 9b, which are separated from one another, are located in the waste-heat recovery circuit 2 for condensing the working fluid A in the low pressure region 4. Both condensers 9a, 9b are realized as double-flow condensers. The condenser 9a has a first fluid path 17a for the flow-through with the working fluid A, and a second fluid path 17b for the flow-through with the coolant K. The two fluid paths 17a, 17b run fluidically separately from one another in the condenser 9a, but are thermally coupled to one another for the heat exchange between the working fluid A and the coolant K.

(22) The additional condenser 9b has a first fluid path 28a for the flow-through with the working fluid A, and a second fluid path 28b for the flow-through with the additional coolant. The two fluid paths 28a, 28b run fluidically separately from one another in the condenser 9b, but are thermally coupled to one another for the heat exchange between the working fluid A and the additional coolant K*. The first condenser 9a serves to cool the working fluid A in the case of failure, thus in the case of a fluid pressure of the working fluid A, which is too high, due to insufficient cooling. The additional condenser 9b also cools the working fluid A during the nominal operation of the waste-heat recovery system 1, thus when no failure is at hand.

(23) FIG. 3 shows a second alternative of the waste-heat recovery system 1 of FIG. 1. In the example of FIG. 3as well as in the example of FIG. 1the condenser 9 is embodied for a simultaneous thermal interaction of the working fluid A with the coolant K from the container 10 as well as with the further, additional coolant K*, for example with coolant water. However, the condenser 9 only has twoand not threefluid paths 17a, 17b. The fluid path 17a serves for the flow-through with the working fluid A. The fluid path 17b generally serves for the flow-through with the additional coolant K* in the nominal operation of the waste-heat recovery system 1.

(24) The waste-heat recovery system 1 of FIG. 3 differs from the waste-heat recovery system 1 of FIG. 1 in that the fluid line 15 leads into the second fluid path 17b at an outlet point 25, i.e. the second sub-chamber 13b and the fluid path 17b are fluidically connected. In the case of failure, the coolant K is thus pushed out of the container 10 into the second fluid path 17 by means of the additional coolant K*. By means of a non-return valve 26 located in the fluid path 17b, it is ensured that the coolant K flows into the fluid path 17b in the flow direction of the additional coolant K*. A (third) pressure-relief valve 14c located in the fluid path 17b opens when a predetermined third threshold pressure p.sub.3 is exceeded, such that the mixture of coolant K and additional coolant K* can be discharged into the surroundings 16 analogously to the examples of FIGS. 1 and 2. The third threshold pressure p.sub.3 has to thereby be larger than the working pressure of the additional coolant K* in the nominal operating state of the waste-heat recovery system 1. The third pressure-relief valve 14c can be embodied as non-return valve 27.

(25) A mixing of the coolant K with the coolant K* is accepted in the case of the alternative of FIG. 3, because a maintenance of the entire waste-heat recovery system 1 needs to be carried out in any event, when said failure occurs. In contrast to the waste-heat recovery system 1 of FIG. 1, the waste-heat recovery system 1 according to FIG. 3 has the advantage that the (second) condenser 9b can be forgone.

(26) In an alternative of FIGS. 1 to 3, the first pressure-relief valve 14a can in each case be forgone. In the case of this alternative, the divider 12 acts as pressure-relief valve. For this purpose, it comprises a dividing membrane 19 of a resilient material, which expands when the predetermined first threshold pressure p.sub.1 of the working fluid A is exceeded, such that the working fluid A can then flow into the first sub-chamber 13a.