Sorption heat pump and loop process

Abstract

A sorption heat pump (1) and a sorption cycle process with gaseous refrigerant (14), liquid solvent (15) and a solution (18) which is a single-phase mixture of the solvent (15) and the refrigerant (14) are disclosed, wherein the solvent (15) first absorbs a medium-pressure partial stream (21) and then a high-pressure partial stream (22) of the refrigerant (14) at a high-pressure level, releasing the heat (26) generated in each case to a heat sink (16) outside the sorption cycle process, the solvent (15) and the medium-pressure partial stream (21) are pumped from a low-pressure level to the medium-pressure level, and the solution (18) is pumped to a high-pressure level after absorption of the medium-pressure partial stream (21) and a high-pressure partial stream (22), and the solution (18) is depressurized to the low-pressure level after absorption of the high-pressure partial stream (22).At the low-pressure level, heat is absorbed from a heat source (19) outside the sorption cycle, thereby expelling the refrigerant (14). It is proposed that the high-pressure partial flow (22) be compressed starting from the low-pressure level.

Description

[0001] The invention relates to a sorption heat pump with a low-pressure section, a medium-pressure section, and a high-pressure section, comprising a gaseous refrigerant, a liquid solvent, and a solution that is a single-phase mixture of the solvent and the refrigerant, and an absorption unit in which the solvent first absorbs a medium-pressure partial flow of the refrigerant in a medium-pressure absorber of the medium-pressure section and then a high-pressure partial flow in a high-pressure absorber of the high-pressure section, thereby releasing the heat generated in each case to a heat sink outside the sorption heat pump, with a medium-pressure pump and a medium-pressure compressor that pump the solvent and the medium-pressure partial flow from the low-pressure section into the medium-pressure absorber, and with a high-pressure pump and a high-pressure compressor that pump the solution after exiting the medium-pressure absorber and the high-pressure partial flow into the high-pressure absorber.with a desorber in which the solution in the low-pressure area absorbs heat from a heat source outside the sorption heat pump and thereby drives out the refrigerant, and with a throttling valve that expands the solution from the high-pressure area to the low-pressure area after absorption of the high-pressure partial flow. The invention further relates to a sorption cycle process in such a sorption heat pump.

[0002] EP4425072A1 proposes splitting the refrigerant in the medium-pressure range upstream of the medium-pressure absorber in a sorption heat pump and a sorption cycle of the aforementioned type, and further compressing the high-pressure partial flow to the high-pressure level. This further compression requires a minimum difference between the medium and high-pressure levels. Thus, either the medium-pressure level limits the absorbed medium-pressure partial flow and therefore the heating power delivered in the medium-pressure absorber, or a high high-pressure level heats the high-pressure partial flow to a temperature that is not technically necessary for steam generation. Both reduce the efficiency of the sorption heat pump. Task

[0003] The invention is based on the objective of increasing the efficiency of the sorption heat pump. Solution

[0004] Based on the known sorption heat pump, the invention proposes that the high-pressure compressor compresses the high-pressure partial flow from the low-pressure area after it exits the generator.

[0005] In solution-circulation sorption heat pumps, heat transfer in the absorber occurs via a temperature glide. The solution heats up at the absorber inlet through absorption of the vaporous refrigerant and is subsequently cooled by the heat transfer fluid of the heat sink during further absorption. In the prior art, the temperature at the absorber inlet during steam generation is higher than required for the isothermal phase change between the liquid and gaseous states of the heat transfer fluid. The unused exergy potential of this excess temperature reduces the efficiency of the known sorption heat pump.

[0006] The inventive division of the refrigerant at the low-pressure level and parallel compression of the partial flows from the low to the medium and high-pressure levels enables a smaller distance between the medium and high-pressure levels and thus an increased efficiency compared to the prior art through high absorption at the medium-pressure level and at the same time a high-pressure level that is not oversized for steam generation.

[0007] Preferably, in a sorption heat pump according to the invention, the medium-pressure absorber and the high-pressure absorber are arranged at the same geodetic height. The level of the liquid heat transfer fluid in the heat sink is then the same in both, and the heat absorbed in each corresponds to the gaseous heat transfer fluid produced and discharged. In such a sorption heat pump, the distribution of the heat transfer fluid from the heat sink between the medium-pressure and the high-pressure absorber does not require any further control.

[0008] Alternatively, the partial flows of the heat transfer fluid into the two absorbers can also be regulated via valves.

[0009] Preferably, a sorption heat pump according to the invention comprises a solution heat exchanger in which the solvent absorbs heat from the solution at the high-pressure level. The absorbed heat is then available in the medium-pressure absorber for the heat sink. In particular, the solvent can absorb the heat at the medium-pressure level.

[0010] Preferably, in a sorption heat pump according to the invention, the medium-pressure absorber and / or the high-pressure absorber are plate heat exchangers. Such absorbers are technically simple, require little maintenance, and are readily available on the market in a wide variety of cost-effective designs.

[0011] Preferably, the solvent in a sorption heat pump according to the invention is water and the refrigerant is ammonia. Water and ammonia are natural substances and have proven their worth in refrigeration technology.

[0012] Based on the known sorption cycle process, the invention proposes that the high-pressure partial flow be compressed starting from the low-pressure level. The sorption cycle process according to the invention takes place in a sorption heat pump according to the invention and is characterized by the advantages described above.

[0013] Preferably, in a sorption cycle according to the invention, a heat transfer fluid from the heat sink is divided into two parallel partial flows. The heat generated during the absorption of the medium-pressure partial flow is transferred to a first partial flow, and the heat generated during the absorption of the high-pressure partial flow is transferred to a second partial flow. The partial flows of the heat transfer fluid are then recombined. In such a sorption cycle according to the invention, if there are very different temperature differences between the heat source and the heat sink, the largest possible medium-pressure partial flow is absorbed at the medium-pressure level, and the heat generated is transferred to the heat transfer fluid of the heat sink, for example, to generate steam.

[0014] Alternatively, preferably, in a sorption cycle process according to the invention, the heat generated during the absorption of the medium-pressure partial flow and subsequently the heat generated during the absorption of the high-pressure partial flow are first transferred to a heat transfer medium of the heat sink. If the temperature difference at the heat sink is much greater than at the heat source, the heat transfer medium of the heat sink is thus preheated in the medium-pressure absorber and only heated to the desired output temperature in the high-pressure absorber.

[0015] Preferably, a sorption cycle process according to the invention delivers 0.5 to 15 MW to the heat sink. Furthermore, preferably, in a sorption cycle process according to the invention, the heat absorbed at the heat source results in a temperature difference of less than 60 K, preferably less than 15 K, and the heat delivered at the heat sink results in a temperature difference of less than 30 K. In this power range and at such low temperature differences, a sorption heat pump according to the invention operates particularly efficiently.

[0016] Preferably, the pressure ratio of the high-pressure level to the medium-pressure level is less than 1.5. Such low pressure ratios cannot be achieved with commercially available compressors; they are only made possible by the compression of the high-pressure partial flow from the low-pressure level to the high-pressure level according to the invention. Example of implementation

[0017] The invention is explained below with reference to an exemplary embodiment. The sorption heat pump 1 according to the invention, shown in the figure, has a low-pressure section 2, a medium-pressure section 3, and a high-pressure section 4, an absorption unit 5, a throttle valve 6 between the high-pressure section 4 and the low-pressure section 2, an ejector 7 and a separator 8 in the low-pressure section 2, a medium-pressure compressor 9 and a medium-pressure pump 10 between the low-pressure section 2 and the medium-pressure section 3, a high-pressure compressor 11 between the low-pressure section 2 and the high-pressure section 4, a high-pressure pump 12 between the medium-pressure section 3 and the high-pressure section 4, and pipes 13 that connect the throttle valve 6, ejector 7, and separator 8 via the medium-pressure pump 10, medium-pressure compressor 9, and high-pressure pump 12 to the absorption unit 5, and in this order to form a closed system.

[0018] In a cycle of a sorption cycle process according to the invention with ammonia (NH 3 ) as refrigerant 14 in water as solvent 15, a flow of 1.35 kg / s of solvent 15 absorbs a flow of 0.29 kg / s of refrigerant 14 in the absorption unit 5 and releases heating power to a heat sink 16.

[0019] Feedwater, entering the absorption unit 5 at a temperature below 100 °C at a flow rate of 0.874 kg / s, acts as the heat transfer medium 17 for the heat sink 16 and exits the absorption unit 5 as saturated steam at 120 °C. A stream of solution 18, exiting the absorption unit 5 at a high pressure of 41 bar at a flow rate of 1.64 kg / s at 124 °C, is expanded to a low pressure of 15 bar by the throttle valve 6 and heated to 96.5 °C in the desorber 7 from a heat source 19. The heat transfer medium 20 from the heat source 19, entering the desorber 7 at 100 °C, is thereby cooled to 90 °C. From the subsequent separator 8, the solvent 15 is pumped by the medium-pressure pump 10 and a medium-pressure partial flow 21 of the refrigerant 14 is pumped by the medium-pressure compressor 9, each to a medium-pressure level of 36 bar and a high-pressure partial flow 22 of the refrigerant 14 is pumped by the high-pressure compressor 11 to a high-pressure level of 41 bar and conveyed into the absorption unit 5.

[0020] The absorption unit 5 comprises a medium-pressure absorber 23 and a high-pressure absorber 24. The heat transfer fluid 17 from the heat sink 16 is first divided into two partial flows 25 before entering the medium-pressure absorber 23 and the high-pressure absorber 24. The partial flows 25 pass through the medium-pressure absorber 23 and the high-pressure absorber 24 in parallel, and after exiting them, the partial flows 25 are recombined.

[0021] The medium-pressure partial flow 21 of the refrigerant 14 enters the absorption unit 5 at the medium-pressure level at 183 °C. In the medium-pressure absorber 23, the solvent 15 absorbs the medium-pressure partial flow 21 and releases heat 26 to the heat transfer medium 17 of the heat sink 16. At the selected medium-pressure level, the mixing temperature of the vaporous refrigerant and the solvent 15 is higher than the vapor temperature to be generated, so that the medium-pressure partial flow 21 can be absorbed with heat release. The medium-pressure partial flow 21 therefore does not need to be compressed to the high-pressure level, which saves compression work and increases efficiency. The solvent 15 would heat up considerably more than necessary at the high-pressure level. By supplying refrigerant at the medium-pressure level, the solution 18 heats up less at the high-pressure level. The exergy losses are therefore low.

[0022] The solution 18 exiting the medium-pressure absorber 23 is pumped by the high-pressure pump 12 into the high-pressure absorber 24, where it absorbs the high-pressure partial flow 22 and releases further heat 26 to the heat transfer medium 17 of the heat sink 16. The renewed supply of refrigerant 14 at the high-pressure level results in a higher mixing temperature, allowing the high-pressure partial flow 22 to also be absorbed with heat release.

[0023] The absorption unit 5 has a solution heat exchanger 27 in which the solvent 15 at the medium-pressure level absorbs heat from the solution 18 exiting the high-pressure absorber 24 at the high-pressure level. The solution 18, highly enriched with the coolant, is cooled in the solution heat exchanger 27 and expanded from the high-pressure to the low-pressure level in the throttling valve 6. During this process, the temperature drops sufficiently for the solution 18 to absorb enough heat from the heat source 19.

[0024] The ejector 7, the medium-pressure absorber 23, the high-pressure absorber 24 and the solution heat exchanger 27 are plate heat exchangers. The characters are

[0025] 1 Sorption heat pump 2 Low-pressure area 3 Medium-pressure area 4 High-pressure area 5 Absorption unit 6 Throttle valve 7 Ejector 8 Separator 9 Medium-pressure compressor 10 Medium-pressure pump 11 High-pressure compressor 12 High-pressure pump 13 Piping 14 Refrigerant 15 Solvent 16 Heat sink 17 Heat transfer fluid of the heat sink 18 Solution 19 Heat source 20 Heat transfer fluid of the heat source 21 Medium-pressure partial flow 22 High-pressure partial flow 23 Medium-pressure absorber 24 High-pressure absorber 25 Partial flow 26 Heat 27 Solution heat exchanger

Claims

1. Sorption heat pump (1) with a low-pressure section (2), a medium-pressure section (3) and a high-pressure section (4), with gaseous refrigerant (14), liquid solvent (15) and a solution (18) which is a single-phase mixture of the solvent (15) and the refrigerant (14), and • with an absorption unit (5) in which the solvent (15) first absorbs a medium-pressure partial flow (21) of the refrigerant (14) in a medium-pressure absorber (23) of the medium-pressure section (3) and then a high-pressure partial flow (22) of the refrigerant (14) in a high-pressure absorber (24) of the high-pressure section (4), thereby releasing the heat (26) generated in each case to a heat sink (16) outside the sorption heat pump (1), • with a medium-pressure pump (10) and a medium-pressure compressor (9) which pumps the solvent (15) and the medium-pressure partial flow (21) from the low-pressure section (2) into the Medium-pressure absorber (23) convey, • with a high-pressure pump (12) and a high-pressure compressor (11),which convey the solution (18) after exiting the medium-pressure absorber (23) and the high-pressure partial flow (22) into the high-pressure absorber (24), • with a desorber (7) in which the solution (18) in the low-pressure area (2) absorbs heat from a heat source (19) outside the sorption heat pump (1) and thereby drives off the refrigerant (14), and • with a throttle valve (6) which expands the solution (18) after absorption of the high-pressure partial flow (22) from the high-pressure area (4) into the low-pressure area (2), , characterized by the fact that The high-pressure compressor (11) compresses the high-pressure partial flow (22) after exiting the ejector (7) from the low-pressure area (2).

2. Sorption heat pump (1) according to the preceding claim, characterized by the fact that the medium-pressure absorber (23) and the high-pressure absorber (24) are arranged at the same geodetic height.

3. Sorption heat pump (1) according to one of the preceding claims, characterized by a solution heat exchanger (27) in which the solvent (15) in the medium pressure range (3) absorbs heat from the solution (18) in the high pressure range (4).

4. Sorption heat pump (1) according to one of the preceding claims, characterized by the fact that the medium pressure absorber (23) and / or the high pressure absorber (24) are plate heat exchangers.

5. Sorption heat pump (1) according to one of the preceding claims, characterized by the fact that the solvent (15) is water and the refrigerant (14) is ammonia.

6. Sorption cycle process with gaseous refrigerant (14), liquid solvent (15) and a solution (18) which is a single-phase mixture of the solvent (15) and the refrigerant (14), wherein: • the solvent (15) first absorbs a medium-pressure partial stream (21) of the refrigerant (14) at a medium-pressure level and then a high-pressure partial stream (22) at a high-pressure level, releasing the heat (26) generated in each case to a heat sink (16) outside the sorption cycle process; • the solvent (15) and the medium-pressure partial stream (21) are pumped from a low-pressure level to the medium-pressure level, and the solution (18) is pumped to a high-pressure level after absorption of the medium-pressure partial stream (21) and a high-pressure partial stream (22); • the solution (18) is depressurized to the low-pressure level after absorption of the high-pressure partial stream (22).at the low-pressure level, it absorbs heat from a heat source (19) outside the sorption cycle process and thereby expels the refrigerant (14), , characterized by the fact that The high-pressure partial flow (22) is compressed starting from the low-pressure level.

7. Sorption cycle process according to the aforementioned claim, characterized by the fact that A heat carrier (17) of the heat sink (16) is divided into two parallel partial flows (25) and the heat (26) generated when absorbing the medium-pressure partial flow (21) is transferred to a first of the partial flows (25) and the heat (26) generated when absorbing the high-pressure partial flow (22) is transferred to a second of the partial flows (25) and the partial flows (25) are then brought together again.

8. Sorption cycle process according to one of claims 6 and 7, characterized by 0.5 to 15 MW of heat delivered to the heat sink (16) (26).

9. Sorption cycle process according to one of claims 6 to 8, characterized by the fact that the absorbed heat at the heat source (19) causes a temperature difference of less than 60 K, preferably less than 15 K, and the released heat (26) at the heat sink (16) causes a temperature difference of less than 30 K.

10. Sorption cycle process according to one of claims 6 to 9, characterized by a pressure ratio of the high-pressure level to the medium-pressure level of less than 1.5.

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