SORPTION HEAT PUMP AND CYCLE

Description

[0001] The invention relates to a sorption cycle process according to claim

[0002] A sorption cycle process is known from EP 3 964 770 A1. It proposes first pumping the lean solution and refrigerant from the low-pressure level to the high-pressure level and conveying them to the high-pressure absorber. A medium-pressure partial flow is extracted from the refrigerant upstream of the high-pressure absorber and expanded to the medium-pressure level, so that the solvent initially absorbs only a remaining high-pressure partial flow, and the resulting enriched solution subsequently absorbs the medium-pressure partial flow in the medium-pressure absorber.

[0003] In the background of the invention, EP 3 540 334 A1 discloses the use of a sorption heat pump as a heat transformer, in which the solution at a medium-pressure level absorbs a medium-pressure partial flow of the refrigerant and initially supplies the resulting absorption heat to a partial flow of the lean solution remaining downstream of the expeller. The rich solution at the low-pressure level absorbs a further portion of the resulting heat from the rich solution upstream of the throttle element in the expeller. Document EP 3 540 334 A1 discloses a sorption cycle process with the features according to the preamble of claim 1. Task

[0004] The invention is based on the object of reducing the energy requirement to reach the high pressure level. Solution

[0005] In heat pumps with a solution cycle, heat is released in the absorber with a temperature glide. The mixture of solvent and vaporous refrigerant initially heats up considerably upon entering the absorber and then cools down again as the refrigerant dissolves in the solvent.

[0006] The invention is based on the finding that the superheating at the absorber inlet known from the prior art for the phase change of the refrigerant from the gaseous to the liquid (dissolved) state during steam generation is not only unnecessary – here, a phase change occurs on the heat sink side at a constant temperature – but also limits the absorption of the refrigerant because the mixture in the absorber cannot be cooled further than slightly above the boiling point of the steam. As the refrigerant content decreases, the pressure ratio between the high-pressure level and the low-pressure level required for expulsion increases – and conversely, a high pressure ratio requires a high power consumption for the compressor and a low COP of the sorption heat pump.

[0007] Based on the known sorption cycle, the invention proposes that the solution transfers heat generated during the absorption of the medium-pressure partial flow to the solution at the high-pressure level in such a way that the latter expels the high-pressure partial flow of the refrigerant. Unlike the prior art, such a sorption heat pump does not require a compressor to compress the high-pressure partial flow from the medium to the high-pressure level. The energy saved thereby exceeds the additional energy required to pump the additional mass flow of the enriched solution to the high-pressure level.

[0008] Preferably, in a sorption cycle according to the invention, a heat transfer medium of the heat sink is divided into two parallel partial streams, and the heat generated during the absorption of the refrigerant at the medium-pressure level and at the high-pressure level is transferred to the partial streams. The partial streams of the heat transfer medium are then recombined. With very different spreads at the heat source and the heat sink, in such a sorption cycle according to the invention, the largest possible proportion of the refrigerant is absorbed at the medium-pressure level, and the resulting heat is transferred to the heat transfer medium of the heat sink, for example, to generate steam there.

[0009] Alternatively, in a sorption cycle according to the invention, the heat generated during absorption at the medium-pressure level and then the heat generated at the high-pressure level are transferred to a heat transfer medium in the heat sink. If the spread at the heat sink is much greater than at the heat source, the heat transfer medium in the heat sink is preheated in the medium-pressure absorber and only heated to the desired initial temperature in the high-pressure absorber.

[0010] Such a sorption heat pump preferably has an intermediate pump that pumps the solution enriched in the high-pressure expeller to the high-pressure level and conveys it at the high-pressure level into the high-pressure absorber. Pumping in two stages is more energy-efficient than the alternative single-stage pumping and intermediate expansion from the high-pressure to the medium-pressure level.

[0011] Such a sorption heat pump preferably has a medium-pressure absorber, with the solution first absorbing the medium-pressure partial flow of the refrigerant in the high-pressure ejector and then in the medium-pressure absorber. The heat generated in the medium-pressure absorber can then be additionally transferred to the heat sink.

[0012] Preferably, in such a sorption heat pump, a remaining depleted solution from the high-pressure expeller is expanded to the intermediate pressure level in a throttle valve and fed into the intermediate pressure absorber. The two solutions from the high-pressure expeller—the depleted solution at the high-pressure level and the enriched solution at the intermediate pressure level—are similar in temperature and composition and can therefore be mixed without significant loss of internal energy. Furthermore, the absorption capacity for the refrigerant in the intermediate pressure absorber increases with the solvent flow rate.

[0013] Alternatively, the depleted solution can be fed into the high-pressure absorber at the high-pressure level. The depleted solution then does not need to be expanded, thus avoiding the energy loss associated with expansion.

[0014] Such a sorption heat pump preferably has a solution heat exchanger in which the solution at the medium-pressure level absorbs heat from the solution at the high-pressure level. The absorbed heat is then available in the absorption unit for the heat sink.

[0015] In such a sorption heat pump, the medium-pressure absorber, the high-pressure absorber, and / or the high-pressure ejector are preferably plate heat exchangers. Such absorbers are technically simple, low-maintenance, and are available cost-effectively in a wide variety of designs on the market.

[0016] Such a sorption heat pump preferably has a throttle valve that expands the solution from medium pressure to low pressure after it exits the absorption unit and enters the expeller, and a pump and compressor that pump the solution and refrigerant from low pressure to medium pressure or high pressure after it exits the expeller. Such a sorption heat pump absorbs heat at a low temperature level and releases it again at a higher level. The rich solution cools in the throttle valve and can thus absorb the low-temperature heat. The gaseous refrigerant and the liquid solvent are fed separately to the absorption unit. Pumps are well-known devices in refrigeration technology and are available inexpensively in a wide variety of designs.

[0017] In such a sorption heat pump, the solvent is preferably water and the refrigerant is ammonia. Water and ammonia are natural substances and have proven their worth in refrigeration technology. Example

[0018] The invention is explained below using exemplary embodiments. Fig. 1 a first sorption heat pump, Fig. 2 a second sorption heat pump, Fig. 3 a third sorption heat pump and Fig. 4 a fourth sorption heat pump.

[0019] The Figure 1The first sorption heat pump 1 shown has an absorption unit 2, a throttle valve 3, an expeller 4, a separator 5, a compressor 6, a pump 7 and pipes 8 which connect the aforementioned in this order to form a circularly closed system, wherein the compressor 6 is arranged in a refrigerant branch 9 and the pump 7 is arranged in a solvent branch 10 running parallel thereto from the separator 5 to the absorption unit 2.

[0020] In one cycle of a sorption cycle process according to the invention, ammonia (NH 3 ) is absorbed as refrigerant 11 in a solution 12 of water as solvent in the absorption unit 2 and heat output is transferred to a heat sink 13. Feed water entering the absorption unit 2 from the heat sink 13 as heat transfer medium 14 of the heat sink 13 exits the absorption unit 2 as saturated steam. A stream of solution 12 exiting the absorption unit 2 at a high pressure level is expanded to a low pressure by the throttle valve 3 and heated in the expeller 4 from a heat source 16, wherein the heat transfer medium 14 of the heat source 16 is cooled. From the subsequent separator 5, the remaining solution 12 in the solvent branch 10 is pumped to the high pressure level by the pump 7 and in the refrigerant branch 9, a medium pressure partial flow 17 of the refrigerant 11 is pumped to a medium pressure level by the compressor 6 and conveyed into the absorption unit 2.

[0021] The absorption unit 2 has a throttle valve 18, a high-pressure expeller 19, a high-pressure absorber 20, a high-pressure separator 21 and another throttle valve 22.

[0022] The solution 12 is first divided into a high-pressure partial stream 23 and a medium-pressure partial stream 24. The latter is expanded to the medium-pressure level in the throttle valve 18 and fed into the high-pressure expeller 19, where it receives the refrigerant 11. The enriched solution 12 exiting the high-pressure expeller 19 is fed into the expeller 4 via a solution collector 25.

[0023] The high-pressure partial stream 23 of the solution 12 absorbs the heat released in the high-pressure expeller 19 and separates a high-pressure partial stream 26 of the refrigerant in the high-pressure separator 21. This is absorbed by the remaining depleted solution 12 in the high-pressure absorber 20 and transfers the heat released to the heat transfer medium 14 of the heat sink 13. The solution 12 exiting the high-pressure absorber 20 is expanded to the intermediate pressure level in the additional throttle valve 22 and also fed into the solution collector 25.

[0024] The expeller 4, the high-pressure absorber 20 and the high-pressure expeller 19 are plate heat exchangers.

[0025] The Figure 2The second sorption heat pump 27 shown essentially corresponds to the first sorption heat pump 1. In contrast, the absorption unit 28 of the second sorption heat pump 27 has a medium-pressure absorber 29. The heat transfer medium 30 of the heat sink 31 is first divided into two partial flows 33 before entering the medium-pressure absorber 29 and the high-pressure absorber 32. The partial flows 32 flow through the medium-pressure absorber 29 and the high-pressure absorber 32 in parallel; these partial flows absorb the heat generated there and are reunited after exiting the same. Upon entering the absorption unit 28 at the medium pressure level, the medium pressure partial flow 34 of the refrigerant is also initially divided into two partial flows 35, which are fed in parallel into the high pressure expeller 18 and the medium pressure absorber 29 and are successively absorbed by the solution 36 in the high pressure expeller 18 and the medium pressure absorber 29.

[0026] The absorption unit 28 further comprises an intermediate pump 37 and two control valves 38. The solution 36 exiting the medium-pressure absorber 29 is first pumped to a high-pressure level by the intermediate pump 37 and then divided: A first partial stream 39 flows via the control valves 38 into the high-pressure absorber 32. A second partial stream 40 flows into the high-pressure expeller 41, absorbs heat there, and separates a high-pressure partial stream 43 of the refrigerant 11 in the high-pressure separator 42, which is then fed into the high-pressure absorber 32 and absorbed there. The depleted solution 36 remaining from the high-pressure separator 42 is fed into the high-pressure absorber 32 with the first partial stream 39 of the solution 36.

[0027] The Figure 3The third sorption heat pump 44 shown essentially corresponds to the second sorption heat pump 27. In contrast, in the third sorption heat pump 44 the poor solution 46 remaining in the high-pressure separator 45 is expanded to the medium-pressure level in a throttle valve 47 and is led into the medium-pressure absorber 49 with the enriched solution emerging from the high-pressure expeller 48.

[0028] The Figure 4 The fourth sorption heat pump 50 shown and the sorption cycle process according to the invention taking place therein essentially correspond to the third sorption heat pump 1. In addition, the fourth sorption heat pump 50 has a solution heat exchanger 51 between the medium pressure level and the high pressure level.

[0029] During operation of the fourth sorption heat pump 50, the expeller 52 absorbs a power of 825 kW from the heat source 53. A flow of 13.1 kg / s of the heat transfer medium 54 from the heat source 53 flows in at temperatures below 100 °C and out at temperatures below 85 °C. The medium-pressure absorber 55 has a power of 678 kW, and the high-pressure absorber 56 has a power of 322 kW. A flow of 0.437 kg / s of the heat transfer medium 57 from the heat sink 58 flows into the absorption unit 59 at temperatures below 100 °C and out at temperatures below 120 °C and under 2 bar.

[0030] At a low pressure level of 23 bar, 2.94 kg / s of the rich solution 60 containing 65.5% refrigerant flows into the expeller 52 at 82 °C, and at 97 °C, a medium-pressure partial flow 62 of 0.91 kg / s is separated in the separator 61 to form 98% pure, gaseous refrigerant. This medium-pressure partial flow is compressed to a medium pressure level of 54 bar by the compressor 63 and fed to the absorption unit 59 at 186 °C. The remaining flow of 2.03 kg / s of solution 60, still containing 51% ammonia, is also pumped to the medium pressure level by the pump 64, absorbs 241 kW of heat from the rich solution 60 in the solution heat exchanger 51, and enters the absorption unit 59 at 121 °C.

[0031] In the high pressure expeller 65, the solution 60 below 139 °C absorbs the first partial stream 66 of 0.49 kg / s of the refrigerant 11 and leaves it in 2.52 kg / s of the enriched solution 60 with 60% ammonia below 125 °C, is combined with 2.26 kg / s of the depleted solution 60 with 56% ammonia below 136 °C and is led in the mixture with 58% ammonia below 131 °C into the medium pressure absorber 55, there absorbs the second partial stream 67 of 0.42 kg / s of the refrigerant 11 and leaves the medium pressure absorber 55 in a stream of 5.2 kg / s with 61.5% ammonia below 123 °C.

[0032] The enriched solution 60 is pumped to the high-pressure level of 56 bar below 123 °C by the intermediate pump 68 and divided into two partial streams 70, 71 of 2.6 kg / s each by the control valves 69. The second partial stream 71 of the enriched solution 60 is heated to 136 °C in the high-pressure expeller 65 and expels the high-pressure partial stream 73 of 0.34 kg / s of the 96% pure refrigerant 11 in the high-pressure separator 72. In the high-pressure absorber 56, the first partial stream 70 of the enriched solution 60 absorbs the high-pressure partial stream 73 of the refrigerant. The rich solution 60 leaves the solution collector 74 below 123 °C, flows through the solution heat exchanger 51, and is throttled to the low-pressure level in the throttle valve 75.

[0033] In the figures are 1Sorption heat pump 2Absorption unit 3Throttle valve 4Extractor 5Separator 6Compressor 7Pump 8Pipe 9Refrigerant branch 10Solvent branch 11Refrigerant 12Solution 13Heat sink 14Heat transfer medium of the heat sink 15Heat source 16Heat transfer medium of the heat source 17Medium-pressure partial flow of the refrigerant 18Throttle valve 19High-pressure expeller 20High-pressure absorber 21High-pressure separator 22Throttle valve 23High-pressure partial flow of the solution 24Medium-pressure partial flow of the solution 25Solution collector 26High-pressure partial flow of the refrigerant 27Sorption heat pump 28Absorption unit 29Medium-pressure absorber 30Heat transfer medium of the heat sink 31Heat sink 32High-pressure absorber 33 Partial flow of the heat transfer medium 34 Medium-pressure partial flow 35 Partial flow of the refrigerant 36 Solution 37 Intermediate pump 38 Control valve 39 Partial flow of the solution 40 Partial flow of the solution 41 High-pressure expeller 42 High-pressure separator 43 High-pressure partial flow of the refrigerant 44 Sorption heat pump 45 High-pressure separator 46 Solution 47 Throttle valve 48 High-pressure expeller49Medium-pressure absorber 50Sorption heat pump 51Solution heat exchanger 52Extractor 53Heat source 54Heat source heat transfer medium 55Medium-pressure absorber 56High-pressure absorber 57Heat sink heat transfer medium 58Heat sink 59Absorption unit 60Solution 61Separator 62Medium-pressure partial flow of the refrigerant 63Compressor 64Pump 65High-pressure extractor 66Partial flow of the refrigerant 67Partial flow of the refrigerant 68Intermediate pump 69Control valve 70Partial flow of the solution 71Partial flow of the solution 72High-pressure separator 73High-pressure partial flow of the refrigerant 74Solution collector 75Throttle valve

Claims

1. A sorption cycle - with a gaseous refrigerant (11) and a liquid one-phase solution (12, 36, 46, 60) of the refrigerant (11) in a solvent; - wherein the solution (12, 36, 46, 60) absorbs a medium-pressure partial flow (17, 34, 64) of the refrigerant (11) at a medium-pressure level, and wherein the solution (12, 36, 46, 60) absorbs a high-pressure partial flow (26, 43, 73) of the refrigerant (11) at a high-pressure level and wherein the solution (12, 36, 46, 60) emits heat generated from absorbing the medium-pressure partial flow and generated from absorbing the high-pressure partial flow to a heat sink (13, 31, 58) outside of the sorption cycle; and - wherein the solution (12, 36, 46, 60) after absorbing the refrigerant (11) absorbs heat from a heat source (16, 53) outside of the sorption cycle and thus expels the refrigerant, characterized in that the solution (12, 36, 46, 60) emits heat generated by absorbing the medium-pressure partial flow (17, 34, 62) to the solution (12, 36, 46, 60) at the high-pressure level, so that the latter expels the high-pressure partial flow (26, 43, 73) of the refrigerant (11).

2. The sorption cycle according to the preceding claim, characterized in that a heat carrier (30, 57) of the heat sink (31, 58) is divided into two partial flows (33) run in parallel and characterized in that heat generated from absorbing the refrigerant at the medium-pressure level and at the high-pressure level is emitted to the two partial flows (33) and characterized in that the two partial flows (33) of the heat carrier (30, 57) are subsequently joined again.

3. The sorption cycle according to one of the preceding claims in a sorption heat pump (1, 27, 44, 50), characterized in that the solution (12, 36, 46, 60) - absorbs the medium-pressure partial flow (17, 34, 62) and the high-pressure partial flow (26, 43, 73) in an absorption unit (2, 28, 59), - expels the refrigerant (11) in a generator (4, 52), and absorbs the medium pressure partial flow (17, 34, 62) in a high-pressure generator (19, 41, 48, 65).

4. The sorption cycle according to the preceding claim, characterized in that an intermediary pump (37, 68) pumps the solution (36, 46) enriched in the high-pressure generator (41, 48, 65) to the high-pressure level and feeds the latter at the high-pressure level into the high-pressure absorber (32, 56).

5. The sorption cycle according to the preceding claim, characterized in that the solution (36, 46, 60) absorbs the medium-pressure partial flow (34, 62) of the refrigerant in the high-pressure generator (41, 48, 65) first, and thereafter in the medium-pressure absorber (29, 49, 55).

6. The sorption cycle according to the preceding claim, characterized in that a reduced solution (46, 60) remaining from the high-pressure generator (48, 65) is expanded in a throttle valve (47) to the medium-pressure level and run into the medium pressure absorber (49, 55).

7. The sorption cycle according to one of the claims 3 through 6, characterized in that the solution (60) at the medium-pressure level absorbs heat from the solution (60) at the high-pressure level in a solution heat exchanger (51).

8. The sorption cycle according to one of the claims 3 through 7, characterized in that the high-pressure generator (19, 41, 48, 65), the medium- pressure absorber (29, 49, 55), and / or the high-pressure absorber (20, 32, 56) are plate heat exchangers.

9. The sorption cycle according to one of the claims 3 through 8, characterized in that a throttle valve (3, 75) expands the solution (12, 36, 46, 60) after exiting the absorption unit (2, 28, 59) from the high-pressure level to the low-pressure level to enter the generator (4, 52), and a pump (7, 64) and a compressor (6, 62) pump the solution (12, 36, 46, 60) and the refrigerant (11) after exiting from the generator (4, 52) from the low pressure level to the medium pressure level or to the high-pressure level.

10. The sorption cycle according to one of the claims 3 through 9, characterized in that the solvent is water and the refrigerant (11) is ammonia.