HEAT TRANSFER DEVICE

Abstract

The invention relates to a device for heat transfer, comprising a low temperature heat exchanger (3) and a high temperature heat exchanger (5), the heat exchangers (3, 5) being connected to one another by means of a connecting line such that a heat transfer medium flows through the high temperature heat exchanger (5) and through the low temperature heat exchanger (3) in succession, at least one dwell time tank (19) being arranged in the connecting line.

Claims

1.-20. (canceled)

21. A device for heat transfer, comprising a low temperature heat exchanger (3) and a high temperature heat exchanger (5), the heat exchangers (3, 5) being connected to one another by means of a connecting line such that a heat transfer medium flows through the high temperature heat exchanger (5) and through the low temperature heat exchanger (3) in succession, wherein at least one dwell time tank (19) is arranged in the connecting line.

22. The device as claimed in claim 21, wherein the high temperature heat exchanger (5) and the low temperature heat exchanger (3) in each case form a section of one heat exchanger, and the connecting line branches off from the region, through which the heat transfer medium flows, of the low temperature heat exchanger and issues into that region of the high temperature heat exchanger through which the heat transfer medium flows.

23. The device as claimed in claim 22, wherein the region, through which the heat transfer medium flows, between the low temperature heat exchanger (3) and the high temperature heat exchanger (5) has a flow barrier, and the connecting line connects the regions, through which the heat transfer medium flows, of the low temperature heat exchanger (3) and of the high temperature heat exchanger (5) to one another, so that the heat transfer medium flows out of the section forming the high temperature heat exchanger (5), via the connecting line, into the section forming the low temperature heat exchanger (3) or out of the section forming the low temperature heat exchanger (3), via the connecting line, into the section forming the high temperature heat exchanger (5).

24. The device as claimed in claim 21, wherein the dwell time tank (19) comprises at least two storage cells (25), and the individual storage cells (25) are connected to one another in the direction from the low temperature heat exchanger (3) to the high temperature heat exchanger (5) in each case via a connection from the lower region of a first storage cell (25) to the upper region of an adjacent second storage cell (25).

25. The device as claimed in claim 24, wherein the connection between two storage cells (25) comprises a cell interspace (31), the connection from the cell interspace (31) to the upper region of the second storage cell (25) being formed with an overflow (47) and that from the cell interspace (31) to the lower region of the first storage cell (25) being formed by a partition (41) with an orifice (33), so that, in the case of a throughflow of the storage cells (25) from the high temperature heat exchanger (5) to the low temperature heat exchanger (3), the liquid flows in each case through the orifice (33) in the lower region of the partition (41) into the cell interspace and via the overflow (47) out of the cell interspace (31) into the second storage cell (25) or, in the case of a flow in the opposite direction, flows via the overflow (47) into the cell interspace (31) and through the orifice (33) in the lower region of the partition (41) out of the cell interspace (41) into the first storage cell (25).

26. The device as claimed in claim 24, wherein at least one storage cell (25) is closed by means of a cover (51), so that a gas space (49) is formed between the liquid in the storage cell (25) and the cover (51).

27. The device as claimed in claim 26, wherein a pipeline (53) branches off from at least one gas space (49) and is immersed into the liquid of a storage cell (25) positioned nearer to the low temperature heat exchanger (3) or into the liquid in the connection of two adjacent storage cells (25), at least one of the adjacent storage cells (25) having a lower temperature than the temperature of the storage cell (25) from the gas space (49) of which the pipeline (53) branches off.

28. The device as claimed in claim 27, wherein, in addition, a pipeline branches off from at least one gas space (49) of a storage cell (25) and is immersed into the liquid of a storage cell (25) which is positioned nearer to the high temperature heat exchanger (5).

29. The device as claimed in claim 24, wherein all the storage cells (25) are closed by means of a cover (51), and a pipeline (53) branches off at the cover (51) from all the storage cells (25), apart from that positioned nearest to the low temperature heat exchanger (3), and issues in the adjacent storage cell (25) positioned nearer to the low temperature heat exchanger (3) or in the connection of the storage cell (25) to the adjacent storage cell (25) which is positioned nearer to the low temperature heat exchanger (3), and a gas outlet (55) branches off from the cover (51) of the storage cell (25) which is positioned nearest to the low temperature heat exchanger (3).

30. The device as claimed in claim 24, wherein all the storage cells (25) are closed by means of a cover (51), and a pipeline branches off out of the cover (51) from all the storage cells (25), apart from that positioned nearest to the high temperature heat exchanger (5), and is immersed into the liquid of the adjacent storage cell (25) which is positioned nearer to the high temperature heat exchanger (5).

31. The device as claimed in claim 27, wherein, at at least one end, immersed into the liquid, of the pipeline (53), a gas distributor is formed, by means of which gas flowing through the pipeline (53) is distributed in the form of small bubbles in the liquid.

32. The device as claimed in claim 27, wherein the pipelines (53) branching off from the cover (51) are immersed at least into the lower third of the liquid when the storage cell (25) is filled as far as the overflow (47).

33. The device as claimed in claim 27, wherein a compressor, by means of which the gas is transported into the liquid of the adjacent storage cell (25) or into the cell interspace (31), is accommodated in the pipeline (53).

34. The device as claimed in claim 24, wherein a device for conveying the liquid is arranged in the connection between two adjacent storage cells (25).

35. The device as claimed in claim 21, wherein the low temperature heat exchanger (3) is an evaporator and the high temperature heat exchanger (5) is a superheater.

36. The device as claimed in claim 21, wherein an adding point for a regeneration catalyst (75) is positioned upstream of a dwell time tank (19).

37. The device as claimed in claim 36, wherein a control unit or regulating unit is comprised, by means of which the addition of the regeneration catalyst is controlled and/or regulated.

38. The device as claimed in claim 21, wherein the heat transfer medium is a molten salt.

39. The device as claimed in claim 38, wherein the regeneration catalyst is water.

40. A solar power plant comprising the device as claimed in claim 21 as an evaporator and superheater.

Description

[0056] In the figures:

[0057] FIG. 1 shows a diagrammatic illustration of a device with low temperature heat exchanger, high temperature heat exchanger and dwell time tank,

[0058] FIG. 2 shows a dwell time tank with a plurality of storage cells connected in series,

[0059] FIG. 3 shows a dwell time tank in a further alternative embodiment,

[0060] FIG. 4 shows a dwell time tank in a fourth alternative embodiment,

[0061] FIG. 5 shows an embodiment of the invention in which a high temperature heat exchanger and a low temperature heat exchanger are arranged in one apparatus.

[0062] FIG. 1 illustrates diagrammatically a device with a low temperature heat exchanger, a high temperature heat exchanger and a dwell time tank.

[0063] A device 1 with a low temperature heat exchanger 3 and with a high temperature heat exchanger 5 may be used, for example, for the evaporation and superheating of water. In this case, the low temperature heat exchanger 3 is an evaporator and the high temperature heat exchanger 5 is a superheater.

[0064] The low temperature heat exchanger 3 and the high temperature heat exchanger 5 may in each case be designed, for example, as illustrated here, as tube bundle heal: exchangers. Alternatively, however, any other type of construction known to a person skilled in the art can be employed for heat exchangers. Thus, for example, plate heat exchangers, spiral heat exchangers or any combination of different types of heat exchanger may also be used.

[0065] Furthermore, it is also possible that the low temperature heat exchanger 3 and the high temperature heat exchanger 5 are combined structurally in one apparatus.

[0066] In operation, a fluid to be heated passes via an inflow 7 into the low temperature heat exchanger 3 and is heated in the latter. If the low temperature heat exchanger 3 is an evaporator, the fluid is evaporated in this, so that saturated steam, if appropriate even already slightly superheated steam, occurs. The fluid heated in the low temperature heat exchanger 3 is extracted at an outlet 9 and is delivered via an inflow 11 to the high temperature heat exchanger. In the high temperature heat exchanger 5, the fluid is heated further or, if the high temperature heat exchanger 5 is a superheater, the fluid delivered as steam is superheated in the high temperature heat exchanger 5. The heated fluid or the superheated steam then emerges from the high temperature heat exchanger at an outlet 13 and can be delivered for further use, for example to a turbine for driving a generator for current generation when the device 1 is employed in a power plant, for example a solar power plant.

[0067] If the low temperature heat exchanger 3 and the high temperature heat exchanger 5 form a structural unit, the fluid heated in the part forming the low temperature heat exchanger 3 passes directly into the part forming the high temperature heat exchanger 5.

[0068] To heat the fluid, a heat transfer medium is used. In the embodiment illustrated here, this is carried in countercurrent to the fluid to be heated. The heat transfer medium is delivered via a heat transfer medium inflow 15 to the high temperature heat exchanger 5. In the high temperature heat exchanger 5, the heat transfer medium transmits heat to the fluid to be heated and subsequently leaves the high temperature heat exchanger 5 via a heat transfer medium outflow 17. According to the invention, a pipeline forming the heat transfer medium outflow 17 issues in a dwell time tank 19.

[0069] After running through the dwell time tank 19, the heat transfer medium is delivered to the low temperature heat exchanger 3 via a heat transfer medium inflow 21. In the low temperature heat exchanger 3, the heat transfer medium transmits heat to the fluid to be heated and then leaves the low temperature heat exchanger 3 via a heat transfer medium outflow 23.

[0070] In the dwell time tank 19, the heat transfer medium may, for example, be regenerated if this is possible at a lower temperature than the maximum temperature to which the heat transfer medium is heated and, moreover, if the heat transfer medium changes reversibly at the maximum temperature. Such heat transfer media are, for example, as already mentioned above, nitrite salts which react at high temperatures to form oxide and nitrate salt, with nitrogen monoxide being split off. At low temperatures and when the dwell time is sufficiently long, the nitrate salt and the oxide will react with the nitrogen monoxide again to form nitrite salt.

[0071] In the embodiment illustrated in FIG. 1, the dwell time tank 19 has a plurality of storage cells 25. The heat transfer medium, after running through the high temperature heat exchanger 3, is introduced via a first pipeline 27 into a first storage cell of the dwell time tank 19. The first pipeline 27 in this case issues in the lower region, so that the heat transfer medium is introduced into the first storage cell at the bottom and the heat transfer medium already contained in the storage cell is displaced upward. The storage cell 25 is closed on top, and the second pipeline 29 branches off from the cover and ends in the lower region of a second storage cell 25. The displaced heat transfer medium is thus pressed into the second pipeline 29 and through the second pipeline into the second storage cell 25. This may be repeated with any number of storage cells, the number of storage cells depending on their size and on the desired dwell time of the heat transfer medium in the dwell time tank 19.

[0072] A pipeline then branches off from the last storage cell 25 and forms the inflow 21 to the low temperature heat exchanger 3.

[0073] Alternatively to the flow direction illustrated here, it is also possible that the heat transfer medium is carried in the low temperature heat exchanger 3 and in the high temperature heat exchanger 5 in each case in cocurrent to the fluid to be heated. In this case, too, the heat transfer medium can flow first through the high temperature heat exchanger 5 and thereafter through the low temperature heat exchanger 3. Furthermore, it is also possible, independently of the throughflow of the low temperature heat exchanger 3 and high temperature heat exchanger 5, that the heat transfer medium flows first through the low temperature heat exchanger 3 and thereafter through the high temperature heat exchanger 5.

[0074] FIG. 2 illustrates a dwell time tank which is constructed from a plurality of storage cells.

[0075] In the embodiment illustrated in FIG. 2, the dwell time tank 19 comprises a plurality of storage cells 25. In each case two adjacent storage cells 25 have a connection which is configured such that the lower region of one storage cell 25 is connected to the upper region of an adjacent storage cell 25. The connection is configured here in the form of a cell interspace 31. So that liquid transport via the cell interspace 31 can be implemented, the cell interspace 31 is connected via a lower orifice 33 to the lower region 35 of the one storage cell 25 and via an upper orifice 37 to the upper region 39 of the adjacent storage cell 25. The cell interspace 31 and the orifices 33, 37 may be implemented, for example, such that the cell interspace 31 is delimited with respect to the one storage cell 25 by means of a first wall 41 and with respect to the adjacent second storage cell 25 by means of a second wall 43. The first wall 41 in this case ends above the bottom 45 of the storage cell 25 and the cell interspace 31 such that the lower orifice 33 is formed between the bottom 45 and the first wall 41. Alternatively, it is, of course, also possible to form a sufficiently large orifice in the first wall 41. By contrast, the second wall 43 stands on the bottom between the cell interspace 31 and the adjacent storage cell 25, the second wall 43 ending, below the maximum filling height of the storage cell 25, in an overflow 47, so that the liquid flows out of the one storage cell 25 via the overflow into the cell interspace 31. Alternatively to the overflow 47, it is also possible to form in the corresponding position in the second wall 43 an orifice through which the liquid can flow.

[0076] A gas space 49 is located above the liquid in each storage cell 25. The gas space 49 is closed by means of a cover 51. A pipeline 53 branches off from the gas space 49. The pipeline 53 is in this case routed such that it issues in the liquid of an adjacent storage cell 25. So that overpressure does not build up in the last storage cell 25, the latter is provided with a gas outlet 55 through which the gas can be taken off. The gas taken off from the gas outlet 55 may either be discharged into the surroundings or preferably be delivered to a storage cell 25 again, for example via a separate gas inflow.

[0077] The liquid is introduced into the dwell time tank via an inflow 57 and is discharged via an outflow 59. In this case, either the inflow 57 is located in the lower region of a storage cell 25 and the outflow is located in the upper region or at the end of a cell interspace 31 or the inflow is located in the upper region in the outflow in the lower region.

[0078] FIG. 3 shows a dwell time tank in a further embodiment.

[0079] In the embodiment illustrated in FIG. 3, the dwell time tank has a plurality of floors 61. The floors 61 are configured such that the liquid flows onto the uppermost floor via the inflow 57. The inflow is in this case located on one side of the floor. On that side of the floor which faces away from the inflow, an outflow 63 is formed, which serves at the same time as an inflow for the floor 61 lying underneath. The liquid flows through the outflow 63 onto the floor 61 lying underneath and, via the floor 61, to a further outflow 63 which again is arranged on the opposite side. This is repeated until the outflow 59 from the dwell time tank has been reached. By the inflows and outflows 63 being in each case arranged at opposite ends, the liquid flows through the dwell time tank 19 in a meandering manner.

[0080] A fourth embodiment of a dwell time tank is illustrated in FIG. 4.

[0081] In contrast to the embodiments illustrated in FIGS. 1 to 3, the dwell time tank 19 illustrated in FIG. 4 is designed in the form of a pipe coil 65. The heat transfer medium flows via the inflow 57 into the pipe coil 65, flows through the pipe coil, with the result that the desired dwell time is achieved, and then leaves the pipe coil 65 through the outflow 59.

[0082] In the embodiments illustrated in FIGS. 1, 3 and 4, the gas formed is entrained in the form of dispersed bubbles together with the heat transfer medium, so that, for regeneration, if there is a sufficient dwell time, the latter can react directly with the secondary products formed for regeneration purposes.

[0083] FIG. 5 shows an embodiment of the invention in which the high temperature heat exchanger and low temperature heat exchanger are arranged in one apparatus.

[0084] In the embodiment illustrated in FIG. 5, the high temperature heat exchanger 5 and low temperature heat exchanger 3 form in each case a section of the device 1. In this case, the medium, for example water, to be evaporated and to be superheated is delivered via an inflow 7 to the low temperature heat exchanger 3 used as an evaporator. In the low temperature heat exchanger 3, the medium to be evaporated flows through a first tube bundle 67 of U-shaped form. At that end of the tubes of the U-shaped tube bundle 67 which is opposite to the inflow 7, the evaporated medium is extracted from the section forming the low temperature heat exchanger 3 and is delivered by means of a saturated steam line 69 to the section forming the high temperature heat exchanger 5. In the section forming the high temperature heat exchanger 5, a second pipeline bundle 71 of U-shaped form runs, in which the medium delivered as saturated steam is superheated.

[0085] For evaporation and superheating, a heat transfer medium is used which, in the embodiment illustrated here, is carried in countercurrent to the medium to be evaporated and to be superheated. For this purpose, a deflecting sheet 73 is provided in each case in the section forming the high temperature heat exchanger 5 and in the section forming the low temperature heat exchanger 3. The deflecting sheet 73 is in this case positioned such that pipelines of the tube bundles 67, 71 of U-shaped form are led around the deflecting sheet 73. Thus, the heat transfer medium also flows around the deflecting sheet 73 along the pipelines of the U-shaped tube bundles 67, 71.

[0086] After flowing through the section forming the high temperature heat exchanger 5, the heat transfer medium is conducted into the dwell time tank 19, runs through this and passes out of the dwell time tank 19 into the section forming the low temperature heat exchanger 3, flows through the section forming the low temperature heat exchanger 3, along the pipelines, accommodated therein, of the first U-shaped tube bundle 67 and around the deflecting sheet 73, and is thereafter extracted from the low temperature heat exchanger via the heat transfer medium outflow 23.

[0087] To regenerate the heat transfer medium, a regeneration catalyst may be added to the dwell time tank 19. This regeneration catalyst is metered, for example at the inflow into the dwell time tank 19, into the heat transfer medium via an adding point 75 for the regeneration catalyst.

[0088] Alternatively, it is, of course, also possible to meter the regeneration catalyst into the dwell time tank 19 at any desired point. Preferably, however, the metering of the regeneration catalyst takes place in the region of the inflow into the dwell time tank 19 or into the heat transfer medium outflow 17 from the high temperature heat exchanger 3, said heat transfer medium outflow issuing to the dwell time tank 19.

[0089] If the regeneration catalyst used is water, this is preferably separated from the heat transfer medium downstream of the dwell time tank 19 in the flow direction, independently of the design of the high temperature heat exchanger and low temperature heat exchanger. For this purpose, it is possible, for example, to lower the pressure, so that water dissolved in the heat transfer medium changes to the gas phase. After phase separation, the water can then be condensed out of the gas phase. The condensed-out water is preferably metered into the dwell time tank 19 again as regeneration catalyst.

LIST OF REFERENCE SYMBOLS

[0090] 1 Device [0091] 3 Low temperature heat exchanger [0092] 5 High temperature heat exchanger [0093] 7 Inflow to the low temperature heat exchanger [0094] 9 Outflow from the low temperature heat exchanger [0095] 11 Inflow to the high temperature heat exchanger [0096] 13 Outflow from the high temperature heat exchanger [0097] 15 Heat transfer medium inflow into the high temperature heat exchanger [0098] 17 Heat transfer medium outflow from the high temperature heat exchanger [0099] 19 Dwell time tank [0100] 21 Heat transfer medium inflow into the low temperature heat exchanger [0101] 23 Heat transfer medium outflow from the low temperature heat exchanger [0102] 25 Storage cell [0103] 27 First pipeline [0104] 29 Second pipeline [0105] 31 Cell interspace [0106] 33 Lower orifice [0107] 35 Lower region [0108] 37 Upper orifice [0109] 39 Upper region [0110] 41 First wall [0111] 43 Second wall [0112] 45 Bottom [0113] 47 Overflow [0114] 49 Gas space [0115] 51 Cover [0116] 53 Pipeline [0117] 55 Gas outlet [0118] 57 Inflow into the dwell time tank [0119] 59 Outflow from the dwell time tank [0120] 61 Floor [0121] 63 Outflow [0122] 65 Pipe coil [0123] 67 First U-shaped tube bundle [0124] 69 Saturated steam line [0125] 71 Second U-shaped tube bundle [0126] 73 Deflecting sheet [0127] 75 Adding point for the regeneration catalyst