ASSEMBLY HAVING A NUMBER OF HEAT EXCHANGERS, AND METHOD FOR EVAPORATING A WORKING MEDIUM

Abstract

The invention relates to an arrangement having multiple heat exchangers and a method for evaporating a working fluid by transferring heat from a heat source medium, which can be used in a particularly advantageous manner in connection with a system and a method for recovering energy from waste heat in a thermodynamic cycle, in which the waste heat is used as the heat source medium. In the arrangement with multiple heat exchangers, each heat exchangers has a heat source medium through passage and a working fluid chamber separated from that, and the heat source medium through-passages of the heat exchangers are or can be serially interconnected in a ring arrangement, wherein between the heat source medium through-passages of any two serially consecutive heat exchangers in the ring arrangement, one valve means is provided in each case, wherein a supply line for the heat source medium is provided, which can be connected selectively to the inlet of the heat source medium through-passage of each heat exchanger, and wherein a discharge line for the heat source medium is provided, which can be connected selectively to the outlet of the heat source medium through-passage of each heat exchanger.

Claims

1. An arrangement with multiple heat exchangers for evaporating a working fluid by transferring heat from a heat source medium, wherein each heat exchanger (10.1, 10.2, 10.3) has a heat source medium through-passage and a working fluid chamber separate from it, and the heat source medium through-passages of the heat exchangers (10.1, 10.2, 10.3) are or can be connected in series, preferably in a ring arrangement, between the heat source medium through-passages of any two serially consecutive heat exchangers (10.1, 10.2, 10.3), there is provided in each case one valve medium (12.1, 12.2, 12.3), a supply line (14) for the heat source medium is provided, which can be selectively connected to the inlet of the heat source medium through-passage of each heat exchanger (10.1, 10.2, 10.3), and a discharge line (15) for the heat source medium is provided, which can be selectively connected to the outlet of the heat source medium through-passage of each heat exchanger (10.1, 10.2, 10.3).

2. The arrangement with multiple heat exchangers according to claim 1, wherein switchable valve means (11.1, 11.2, 11.3, 13.1, 13.2, 13.3) are provided to create or break the selective connections of the supply and discharge lines (14, 15) to the heat source medium through-passages.

3. The arrangement with multiple heat exchangers according to claim 1, wherein the arrangement is designed in such a manner that the heat source medium through-passage of the heat exchanger (10.1, 10.2, 10.3), which has the highest pressure and/or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement, can be connected to the supply line (14) for the heat source medium, and that the heat source medium through-passage of the heat exchanger (10.1, 10.2, 10.3), which has the lowest pressure and/or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement, can be connected to the discharge line (15) for the heat source medium.

4. The arrangement with multiple heat exchangers according to claim 1, wherein the arrangement is designed in such a manner that the supply and discharge lines (14, 15) for the heat source medium can be connected sequentially and synchronously to the inlets and outlets respectively of the heat source medium through-passages of the heat exchangers (10.1, 10.2, 10.3) of the arrangement.

5. The arrangement with multiple heat exchangers according to claim 1, wherein the arrangement is designed in such a manner that the duration of the connection of the supply and discharge lines (14, 15) for the heat source medium to the heat source medium through-passage of a respective heat exchanger (10.1, 10.2, 10.3) is preset or can be controlled depending on the pressure and/or temperature of the working fluid in the heat exchanger (10.1, 10.2, 10.3), which has the highest pressure or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement.

6. The arrangement with multiple heat exchangers according to claim 1, wherein the arrangement is designed in such a manner that in an introduction phase, the introduction of the working fluid occurs into the working fluid chamber of the heat exchanger (10.1, 10.2, 10.3), which has the lowest pressure or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement, and in a discharge phase, the discharge of the working fluid occurs out of the working fluid chamber of the heat exchanger (10.1, 10.2, 10.3), which has the highest pressure or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement, and wherein the timespan of the introduction phase and the timespan of the discharge phase are essentially set to the same length, and the arrangement is further designed in such a manner that the further switching of the introduction and discharge phases between the heat exchangers (10.1, 10.2, 10.3) of the arrangement occurs synchronously and sequentially.

7. The arrangement with multiple heat exchangers according to claim 6, wherein the arrangement has at least three heat exchangers (10.1, 10.2, 10.3) and the arrangement is designed in such a manner that the heat exchanger(s) (10.1, 10.2, 10.3) that does not have/do not have the highest or the lowest pressure or temperature level of the working fluid, the working fluid remains enclosed in the working fluid chamber during the introduction and discharge phases of the other heat exchangers (10.1, 10.2, 10.3).

8. The arrangement with multiple heat exchangers according to claim 7, wherein the arrangement is designed in such a manner that for the heat exchanger(s) (10.1, 10.2, 10.3) that does not have/do not have the highest or the lowest pressure or temperature level of the working fluid, the heat source medium through-passage can be connected only to the heat source medium through-passage of the, or one of the, other heat exchanger(s) (10.1, 10.2, 10.3).

9. The arrangement with multiple heat exchangers according to claim 1, wherein the heat exchangers (10.1, 10.2, 10.3) of the arrangement are arranged or designed in such a manner that the inlet of the heat source medium through-passage of each heat exchanger (10.1, 10.2, 10.3) is located at a lower position level than the outlet of the heat source medium through-passage of the respective heat exchanger (10.1, 10.2, 10.3).

10. A method for evaporating a working fluid by the transferring heat of a heat source medium in an arrangement with multiple heat exchangers (10.1, 10.2, 10.3), which each have a heat source medium through-passage and a working fluid chamber separate from that, and whose heat source medium through-passages, are or can be interconnected in series, preferably in a ring arrangement, having the steps: sequential connecting of a supply line (14) for the heat source medium to the inlet of the heat source medium through-passage of a first heat exchanger (10.1, 10.2, 10.3) and the sequential connecting of a discharge line (15) for the heat source medium to the outlet of the heat source medium through-passage of a second heat exchanger (10.1, 10.2, 10.3), while the supply line (14) and discharge line (15) are separated from the inlet of the heat source medium through-passage of the second heat exchanger or the outlet of the heat source medium through-passage of the first heat exchanger (10.1, 10.2, 10.3) and, if present, from the inlets and outlets of the heat source medium through-passages of additional heat exchangers (10.1, 10.2, 10.3) of the arrangement.

11. The method for evaporating a working fluid according to claim 10, wherein the supply and discharge lines (14, 15) for the heat source medium are sequentially and synchronously connected to or separated from the heat source medium through-passages of the respective heat exchangers (10.1, 10.2, 10.3).

12. The method for evaporating a working fluid according to claim 10, wherein the heat exchanger (10.1, 10.2, 10.3), which has the highest pressure and/or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3), is connected to the supply line (14) for the heat source medium, and the heat exchanger (10.1, 10.2, 10.3), which has the lowest pressure and/or temperature level among the heat exchangers (10.1, 10.2, 10.3), is connected to the discharge line (15) for the heat source medium.

13. The method for evaporating a working fluid according to claim 10, wherein the duration of the connection of the supply and discharge lines (14, 15) for the heat source medium is preset with a respective heat exchanger (10.1, 10.2, 10.3) or is controlled depending on the pressure and/or temperature of the working fluid in the heat exchanger (10.1, 10.2, 10.3), which has the highest pressure or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement.

14. The method for evaporating a working fluid according to claim 10, wherein in an introduction phase, the feeding-in of the working fluid occurs into the working fluid chamber of the heat exchanger (10.1, 10.2, 10.3), which has the lowest pressure or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3), and in a discharge phase, the discharge of the working fluid occurs out of the working fluid chamber of the heat exchanger (10.1, 10.2, 10.3), which has the highest pressure or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3), and that the timespan of the introduction phase and the timespan of the discharge phase are essentially the same length, and the further switching of the introduction and discharge phases occurs synchronously and sequentially among the heat exchangers (10.1, 10.2, 10.3).

15. The method for evaporating a working fluid according to claim 10, wherein the arrangement has at least three heat exchangers (10.1, 10.2, 10.3) and for the heat exchanger(s) (10.1, 10.2, 10.3), which does not have/do not have the highest or lowest pressure or temperature level of the working fluid, the working fluid remains enclosed in the working fluid chamber during the introduction and discharge phases of the other heat exchangers (10.1, 10.2, 10.3).

16. The method for evaporating a working fluid according to claim 15, wherein for the heat exchanger(s) (10.1, 10.2, 10.3), which does not have/do not have the highest or lowest pressure or temperature level of the working fluid, the heat source medium through-passage is connected only to the heat source medium through-passage of the, or one of the, other heat exchangers (10.1, 10.2, 10.3).

17. The method for evaporating a working fluid according to claim 10, wherein the heat source medium is directed through the heat source medium through-passages of the heat exchangers (10.1, 10.2, 10.3) in such a way that it flows through the heat source medium through-passages at least partly against the influence of gravity.

18. Arrangement with multiple heat exchangers for evaporating a working fluid by transferring heat from a heat source medium, wherein each heat exchanger (10.1, 10.2, 10.3) has a heat source medium through-passage and a working fluid chamber separate from it, and the heat source medium through-passages of the heat exchangers (10.1, 10.2, 10.3) are or can be connected in series, preferably in a ring arrangement, between the heat source medium through-passages of any two serially consecutive heat exchangers (10.1, 10.2, 10.3), there is provided in each case one valve medium (12.1, 12.2, 12.3), a supply line (14) for the heat source medium is provided, which can be selectively connected to the inlet of the heat source medium through-passage of each heat exchanger (10.1, 10.2, 10.3), and a discharge line (15) for the heat source medium is provided, which can be selectively connected to the outlet of the heat source medium through-passage of each heat exchanger (10.1, 10.2, 10.3), wherein the arrangement is designed in such a manner that the heat source medium through-passage of the heat exchanger (10.1, 10.2, 10.3), which has the highest pressure and/or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement, can be connected to the supply line (14) for the heat source medium, and that the heat source medium through-passage of the heat exchanger (10.1, 10.2, 10.3), which has the lowest pressure and/or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement, can be connected to the discharge line (15) for the heat source medium, further wherein the arrangement is designed in such a manner that the supply and discharge lines (14, 15) for the heat source medium can be connected sequentially and synchronously to the inlets and outlets respectively of the heat source medium through-passages of the heat exchangers (10.1, 10.2, 10.3) of the arrangement.

19. The arrangement with multiple heat exchangers according to claim 18, wherein the arrangement is designed in such a manner that the duration of the connection of the supply and discharge lines (14, 15) for the heat source medium to the heat source medium through-passage of a respective heat exchanger (10.1, 10.2, 10.3) is preset or can be controlled depending on the pressure and/or temperature of the working fluid in the heat exchanger (10.1, 10.2, 10.3), which has the highest pressure or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement.

20. The arrangement with multiple heat exchangers according to claim 1, wherein the arrangement is designed in such a manner that in an introduction phase, the introduction of the working fluid occurs into the working fluid chamber of the heat exchanger (10.1, 10.2, 10.3), which has the lowest pressure or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement, and in a discharge phase, the discharge of the working fluid occurs out of the working fluid chamber of the heat exchanger (10.1, 10.2, 10.3), which has the highest pressure or temperature level of the working fluid among the heat exchangers (10.1, 10.2, 10.3) of the arrangement, and wherein the timespan of the introduction phase and the timespan of the discharge phase are essentially set to the same length, and the arrangement is further designed in such a manner that the further switching of the introduction and discharge phases between the heat exchangers (10.1, 10.2, 10.3) of the arrangement occurs synchronously and sequentially.

Description

[0022] The arrangement and the method according to the invention are explained hereafter using the attached drawings. Depicted are:

[0023] FIG. 1: a schematic illustration of an ORC process according to prior art with direct use of the heat source medium in the heat exchanger of the working fluid cycle;

[0024] FIG. 2: a schematic illustration of the “Misselhorn” process with an arrangement of the heat exchangers according to DE 102013009351;

[0025] FIG. 3: a schematic illustration of the “Misselhorn” process with heat exchanger arrangement according to the invention according to a first embodiment;

[0026] FIGS. 4A-C: as schematic illustration of the switching state within a cycle for the arrangement of the heat exchangers pursuant to FIG. 3; and

[0027] FIG. 5: a schematic illustration of a heat exchanger arrangement according to the invention pursuant to the second embodiment;

[0028] FIG. 6: T-Q diagram for a typical ORC process in two different operating modes; and

[0029] FIG. 7: a T-Q diagram for a 10-heat exchanger arrangement according to the invention.

[0030] FIGS. 1 and 2 were already explained in the introduction. FIG. 3 depicts a schematic illustration of the “Misselhorn” process corresponding to FIG. 2 with a heat exchanger arrangement according to the invention pursuant to a first embodiment. The functioning of this heat exchanger arrangement is explained by means of the sequence of FIGS. 4A to 4c. Even though for explanation purposes the depicted embodiment assumes three heat exchangers or heat transfer devices operating as evaporators, the number of heat exchangers is n≧2.

[0031] When increasing the number of heat exchangers operating as evaporators and that having the heat source medium passing through them sequentially, the curve shape of the working fluid and the heat source medium continue to approach each other in the arrangement's T-Q diagram. Furthermore, one shall note that the working fluid lines and working fluid chambers of the heat exchangers are not depicted in FIGS. 4A to 4C to enhance clarity.

[0032] Each heat exchanger 10.1, 10.2, 10.3 of the arrangement has a heat source medium through-passage with an inlet and outlet (not depicted) and a working fluid chamber separated therefrom, also having an inlet and outlet (not depicted), so that the material flows of the heat source medium and working fluid are separated. Between the heat source medium through-passage and the working fluid chamber, one shall ensure that the heat exchange is as efficient as possible, wherein the specific construction of the heat exchangers is not significant for the functioning of the invention, but only represents an optimization task. For example, the heat exchangers may be designed as pipe bundle-heat exchangers.

[0033] The heat source medium through-passages of the heat exchangers are or can be interconnected in series, preferably in a ring arrangement or ring line 16, by the outlet of the heat source medium through-passage of a heat exchanger being connected to the inlet of the heat source medium through-passage of a subsequent heat exchanger in the ring arrangement, wherein between the heat source medium through-passages of any two serially consecutive heat exchangers 10.1, 10.2, 10.3 in the ring arrangement, there is provided in each case one valve 12.1, 12.2, 12.3, with which the connection can be selectively disconnected. Valves 12.1, 12.2, 12.3 are designed as switchable and preferably remote-actuated valves. They may be designed as controlled or simple check valves, if one ensures based on the pressure level of the heat source medium that a backflow into the heat source medium through-passage of a heat exchanger within the ring arrangement does not occur upstream of the heat source medium introduction location.

[0034] A supply line 14 for the heat source medium can be selectively connected to the inlet of the heat source medium through-passage of each heat exchanger and a discharge line 15 for the heat source medium can also be selectively connected to the outlet of the heat source medium through-passage of each heat exchanger. To do so, there are also provided, in the connecting lines between the supply line and the section of the ring line between the respective ring line valve 12.1, 12.2, 12.3 and its respective heat exchanger located downstream, switchable and preferably remote-actuated valves 11.1, 11.2, 11.3 to create and disconnect the selective connections of the supply line to the heat source medium through-passages. Accordingly, switchable and preferably remote-actuated valves 13.1, 13.2, 13.3 are provided in the connection lines between discharge line 15 and the section of the ring line between the respective ring line valve 12.1, 12.2, 12.3 and its respective heat exchanger located upstream in order to create and to disconnect the selection connections of the discharge line to the heat source medium through-passages.

[0035] The combination of connection lines and valves as well as the switchability of the valves of the arrangement is designed in such a manner that within a cycle still to be described below the inlet of the heat source medium through-passage of the heat exchanger, which has the lowest pressure and/or temperature level of the working fluid among the heat exchangers of the ring arrangement, can be connected to the discharge line for the heat source medium, and that the outlet of the heat source medium through-passage of the heat exchanger, which has the lowest pressure and/or temperature level of the work medium among the heat exchangers of the ring arrangement, can be connected to the discharge line for the heat source medium. When there are more than two heat exchangers in the arrangement, for the heat exchanger(s) that do not have the highest or the lowest pressure or temperature level of the working fluid, the heat source medium through-passage can only be connected to the heat source medium through-passage of the, or one of the other, heat exchanger(s), so that the heat source medium is directed in series through the heat exchanger.

[0036] Preferably, the supply and discharge lines for the heat source medium can be sequentially and synchronously connected to the heat source medium through-passages of the heat exchanger of the arrangement, so that the described further switching of the heat exchangers can occur within any given cycle in a simultaneous and clearly delineated manner. Furthermore, the arrangement is designed in such a manner that the duration of the connection of the supply and discharge lines for the heat source medium to the heat source medium through-passage of a respective heat exchanger is preset to a duration corresponding to the configuration of the arrangement and at least for a certain operating period over several cycles. Preferably, it is also possible however that the duration is controlled depending on the pressure and/or temperature of the working fluid in the heat exchanger, which among the heat exchangers in the arrangement has the highest pressure or temperature level of the working fluid, because this heat exchanger provides the evaporated working fluid for the work engine. With this control unit, one can ensure a quasi-continual supply of vaporous working fluid to the work engine at a pressure as constant as possible and one can thereby ensure operation without large outlet or engine speed fluctuations.

[0037] The connection lines and switchable valves for the working fluid as well as the working fluid chambers are not depicted in FIGS. 4 and 5, but are indicated in FIG. 3. In terms of the working fluid cycle, the multiple heat exchanger arrangement according to the invention can be integrated in the working fluid cycle of the “Misselhorn” cycle process known from DE 102013009351 for example and modifies the heat exchanger or heat releaser arrangement (see FIG. 3). The disclosure of DE 102013009351 is thus included here in regard to the working fluid cycle by making reference to the disclosure as a whole. The arrangement according to the invention also namely controls by means of a corresponding valve arrangement the connection/separation of the heat exchanger or heat transfer units to/from the cycle process in such a manner that the heat exchanger units

run through the individual phases of feeding in the working fluid, heating the working fluid, including in the respective heat exchangers, and discharging the vaporous working fluid out of the heat exchanger into the work engine in a sequential and time-offset manner in each case.

[0038] The arrangement is thereby to be designed in such a manner that the introduction of the working fluid takes place into the working fluid chamber of the heat exchanger, which among the heat exchangers of the arrangement has the lowest pressure and/or temperature level of the working fluid, and the discharge of the working fluid occurs out of the working fluid chamber of the heat exchanger, which among the heat exchangers of the arrangement has the highest pressure and/or temperature level of the working fluid, and wherein the timespan of the introduction phase and the timespan of the discharge phase are essentially the same length, and the switchover of the introduction and discharge phases occurs between the heat exchangers of the arrangement in a synchronous and sequential manner. If the arrangement preferably has at least three heat exchangers, it is also designed in such a manner that the heat exchanger(s), which does/do not have the highest or the lowest pressure or temperature level of the working fluid, the working fluid remains enclosed in the working fluid chamber during the introduction and discharge phases of the other heat exchanger. For n evaporators or heat exchangers, there will basically be n different circuit situations of the valves when operating the arrangement according to these phases.

[0039] Hereinafter, a switch cycle of the arrangement of the heat exchangers will be described for example purposes using an arrangement with 3 heat exchangers and in reference to FIGS. 4A-4C. The typical three switch situations required to do so are depicted in FIGS. 4A to 4C.

[0040] In switch situation 1 (FIG. 4A), the evaporated working fluid is conducted at high pressure from heat exchanger 10.1 (corresponding for example to phase 3 of the heat exchanger operating mode using the system known from DE 102013009351) into the work engine and heat exchanger 10.3 is just being filled with a liquid working fluid by a pump. To supply heat exchanger 10.1 with the hottest heat source medium flow and heat exchanger 10.3 the heat source medium flow partially already cooled due to passing through other heat exchangers, valves 11.1, 12.2, 12.3 as well as 13.1 are opened. The remaining valves are closed. Through open valve 11.1, the heat source medium flow upstream from heat exchanger 10.1 is fed into “ring line” 16 and cools upon passing through the three heat exchangers (opened valves 12.2 and 12.3). Lastly, the cooled heat source medium is removed through open valve 13.1 (since valve 12.1 is closed) from the “ring line” and fed into the heat source medium return.

[0041] In switch situation 2 (FIG. 4B), heat exchanger 10.2 is to be fed with the hot heat source medium flow and heat exchanger 10.1 is to be fed with the cooled heat source medium flow. To do so, valves 11.2 and 13.2 as well as 12.3 and 12.1 are opened. The remaining valves are in turn closed.

[0042] In switch situation 3 (FIG. 4C), the hot heat source medium flow is to be conducted through heat exchanger 10.3 and the cooled heat source medium flow is to be conducted through heat exchanger 10.2. To do so, valves 11.3 and 13.3 as well as 12.1 and 12.2 are opened. The remaining valves are in turn closed. The cycle then ends and it re-starts with switch situation 1.

[0043] FIG. 5 depicts a second embodiment of the arrangement, in which the supply and discharge of the hot and the cooled heat source medium flow are each executed as a star-connected circuit 17 and 18 respectively.

[0044] In a (not depicted) preferred embodiment of the arrangement with multiple heat exchangers according to the invention, the heat exchangers of the arrangement are arranged or designed in such a manner that the inlet of the heat source medium through-passage of each heat exchanger is located at a lower position level than the outlet of the respective heat exchanger. In this preferred embodiment, the heat source medium flows through the heat source medium through-passages of the heat exchanger in a vertical manner from bottom to top and thus against the influence of gravity. Even if the heat source medium through-passage in the heat exchanger has a zig-zag shape for example, it is ensured that the heat source medium is conducted through the heat source medium through-passages of the heat exchanger in such a manner that it flows through the heat source medium through-passages at least partially against the influence of gravity.

[0045] The schematic illustrations of embodiments of the invention serve only to explain the invention. For that reason, the distances of the connection lines between the individual components and the arrangement, [as well as] the number and design of valves are only for example purposes and serve to explain the operating principle. Furthermore, it shall be pointed out in particular that the schematically depicted arrangements of heat exchangers or heat transfer devices each have three heat exchanging units, wherein according to the invention one heat exchanger arrangement with at least two heat exchanger units independent of each other may be sufficient and more than the three heat exchanger units may also be used.

[0046] In addition, the invention is not limited to a certain construction of the heat exchangers, wherein in particular the illustration of the heat exchangers in FIGS. 4A-C and 5 is only schematic and is only to clarify the circuit of the heat source medium through-passage within the arrangement and is not to specify any certain construction of the heat exchanger.

[0047] As work media for the arrangement according to the invention, all media usable in conventional cycles, such as the ORC cycles and the “Misselhorn” process, are considered, in particular organic or synthetic materials, for example R245fa, ethanol or R134a.

[0048] The term “heat source medium” also comprises both the medium supplied directly by a heat source and usable directly in the heat exchangers, such as hot wastewater, cooling water, etc., and also a heat transport medium such as thermal oil and similar, which circulates in a closed intermediate circuit and serves to transport the heat from a distant heat source or a heat source not suited for direct use to the heat exchangers of the cycle.

[0049] As a heat source for the arrangement according to the invention, ultimately one can consider all heat sources in the form of useful heat or waste heat from the sources described in the introduction, which supply a sufficiently high temperature level of at least 600 Celsius, preferably 60-100° Celsius and a sufficiently large volume or mass flow. However, the arrangement according to the invention can also be used with heat sources having higher temperature levels.

[0050] Even though FIGS. 3-5 depict an embodiment with single valves [sic], all valves or groups of valves may be designed as rotary valves for example with correspondingly multiple inlets and outlets. The term “valve means” chosen in the claims is therefore to comprise various designs of a means for opening/closing a fluid connection.