JP6313855B2 - Evaporative heat exchanger - Google Patents

Description

  The present invention relates to an evaporating heat exchanger for evaporating a liquid working medium according to the premise of claim 1.

  Attempts have been made to recover some of the exhaust gas energy to further reduce fuel consumption in commercial and passenger vehicles. This can be done thermally, ie the exhaust gas energy is used, for example, to warm the passenger compartment or to heat the internal combustion engine or transmission. In a variation that has been discussed for some time, heat energy is removed from the exhaust gas, which is returned to the internal combustion engine in mechanical form. This method is based on a steam power process, in which the working medium evaporates and superheats in the evaporator and expands in an adjacent expander, for example a turbine, resulting in the production of mechanical energy. Here, the evaporation occurs by heating through the exhaust gas. In this case, the working medium to be evaporated is first heated to the boiling point in the evaporator and then evaporated and subsequently superheated. This can basically happen at two different places in the car. First, in an evaporator used instead of an exhaust gas cooler, heat can be removed from the exhaust gas to evaporate the working medium. In this case, the exhaust gas is cooled by evaporation of the fluid to be evaporated and is supplied again to the engine together with the outside air. The main exhaust gas stream is then intended to be used to vaporize the working medium as well as as a heat source in what is here known as the main exhaust gas evaporator. Such main exhaust gas evaporators are usually provided by automobile manufacturers after the silencer or after all exhaust aftertreatment devices in the exhaust gas system. Instead, the charge air in the supercharged engine is used as a heat source.

  Patent Document 1 discloses a conventional evaporating heat exchanger for evaporating a liquid working medium and utilizing waste heat from an internal combustion engine. In known systems, the introduction of a working medium into the combustion air supplied to the internal combustion engine is intended to be substantially excluded due to sealing problems and leaks in the evaporative heat exchanger. For this purpose, at least one first boundary element forms at least one first flow path and at least one second boundary element forms at least one second flow path, If there is a fluid guiding connection from at least one to the periphery or the containment chamber so that a leak occurs at the boundary element, the working medium can be introduced into the periphery or the containment chamber.

  The concept of gas-operated evaporative heat exchangers described in the prior art provides that the risk of mixing gas and working medium is reduced. For example, when a fluorinated refrigerant flows into the exhaust gas and is supplied to the internal combustion engine and combusted there, hydrofluoric acid is produced, which can flow through the exhaust pipe and cause damage there. If, for example, alcohol is used instead of this refrigerant, if a leak occurs, the alcohol will be co-fired in the internal combustion engine, which will be easily noticeable due to a sudden increase in the output of the internal combustion engine. Under certain circumstances, this may be tricky, especially for inexperienced drivers.

International Patent Publication No. 2012/010349

  The present invention thus addresses the problem of defining an improved embodiment for a conventional evaporative heat exchanger, in which an undesirable mixing of working medium and gas, in particular exhaust gas or charge air, is performed. Can be excluded.

  This problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

  The present invention provides a leakage flow path and / or a leakage space between a first flow path for guiding a working medium and a second flow path for transporting gas, particularly exhaust gas or supply air, and in the process two sheets The cover plate and the wavy fluid plate provided between them have a particularly simple structure and are based on the general concept of constituting both the first flow path and the leakage flow path and / or the leakage space. . In this case, the evaporation heat exchanger according to the present invention for evaporating the liquid working medium is provided with the first flow path for guiding the working medium and the second flow path for guiding the gas. Provided with a housing. The transfer of heat from the gas, for example supply or exhaust gas, to the working medium evaporates, which results in subsequent expansion of the working medium in an expansion machine, for example a turbine, resulting in mechanical work. As stated, according to the present invention, the first flow path and the at least one leakage flow path and / or the leakage space include two relatively thick cover plates and a wave-like fluid plate provided therebetween. The plate bundle formed by the two cover plates and the fluid plate disposed therebetween is thus at least one fluidicly separated from the first flow path and the first flow path. A leakage flow path and / or a leakage space. The connection between the two cover plates and the fluid plate provided between them is made by a cohesive manner, for example a solder connection. In this case, what is provided between two adjacent plate bundles is in each case a second flow path through which a heat transfer gas such as exhaust gas or supply air flows. When the fluid plate breaks and / or the soldering seam between the fluid plate and the cover plate breaks, the working medium flows from the first flow path into the leakage flow path and / or the leakage space, and the second flow It can be discharged from the leak flow path and / or the leak space without being directly mixed with the gas flowing through the path, for example, exhaust gas. Similarly, the leakage flow path and / or the leakage space can also be separated from the leakage flow path and the second by, for example, disconnecting a solder connection between the fluid plate and the cover plate or by breaking the fluid plate wall. It can be used to vent gases that undesirably flow out of the second flow path when a fluid connection occurs with the flow path. As a result of this, the gas flowing into the leak channel and / or the leak space can also be discharged, so that direct mixing with the working medium in the first channel can be avoided. The leakage flow path and / or the leakage space thus forms a natural safety barrier arranged between the two flow paths. The leakage flow path and / or the leakage space is usually filled with air.

  Preferably, the material strength of the fluid plate is lower than the strength of the cover plate provided on the fluid plate. This results in a kind of predetermined break point in the fluid plate, so that if the evaporative heat exchanger is overloaded in the region of the first flow path, the working medium flowing through the first flow path will enter the leakage flow path. Inflow. For example, when the fluid plate breaks, the cover plate that defines the first flow path expands under a specific situation, and for example, compresses the rib structure provided in the second flow path. During expansion of the cover plate, the soldered seam connecting the fluid plate to the cover plate can be dislodged, resulting in a fluid connection between the first flow path and the leak flow path. From the leakage channel, the working medium can be discharged without mixing with the gas flowing through the second channel. Similarly, such a predetermined break point may also be formed by a thinner wall thickness or material thickness of the fluid plate as compared to a cover plate connected to the fluid plate. What is important here is that, first and foremost, the fluid plate, rather than the cover plate, breaks or ruptures when overloaded. This ensures that the leakage flow path and / or the leakage space arranged between the first and second flow paths is utilized for exhausting the working medium or gas, regardless of the type of failure. Is always possible. The leakage flow path and the leakage space are preferably embossed in a manner surrounding the fluid plate, the larger area being called the leakage space and the smaller area being called the leakage flow path.

  In a further advantageous embodiment of the solution according to the invention, the evaporative heat exchangers comprise plate bundles stacked on top of each other, in each case provided with a second flow path therebetween, The leakage flow path and / or the leakage space in FIG. 2 have a first opening, and a plurality of cover plates provided opposite to each other in two adjacent plate bundles each have a second opening, ) A leakage bush for forming the discharge duct is provided between the second openings. Thereby, the leaked fluid or gas can be reliably discharged from the second flow path, or the working medium can be reliably discharged from the first flow path.

  In an advantageous development of the solution according to the invention, the housing has a housing opening connected via a housing leakage bush to the first or second opening in the cover plate of the plate bundle provided adjacent to the housing. ing. In this case, the housing leakage bush and all other leakage bushes form a discharge duct for guiding leakage fluid, also known as a leakage discharge duct, and a conduit leading to the periphery or periphery is attached to the housing leakage bush Sensors capable of measuring the pressure and / or flow rate and / or chemical composition of the fluid in the pipeline are provided in the region of the pipeline. Normally, atmospheric pressure is applied to the discharge duct. At the same time, air with normal properties is present. If the fluid plate breaks or ruptures due to overloading, so that the working medium flows out of the first flow path into the leakage flow path, or the gas flows out of the second flow path into the leakage flow path, Regardless of whether it is an exhaust gas or a working medium, it has different physical and / or chemical properties than air, thus changing the temperature and / or chemical composition in the leakage flow path. If a corresponding change indicative of a leak is detected by the sensor, the latter may control, for example, a pump or exhaust gas recirculation valve that pumps the working medium in response to a signal detected by the sensor. It is also conceivable to output a warning signal that visually and / or audibly informs the motor vehicle user that the evaporative heat exchanger is malfunctioning. As mentioned above, an atmospheric pressure of about 1 bar is usually applied to the sensor. When the evaporative heat exchanger is activated, the pressure in the leak path and / or leak space rises to about 1-1.5 bar due to temperature related expansion, which is normal. However, if the pressure does not increase, there is a sealing problem that may cause the sensor to be defective or cause a pressure drop in the leakage flow path and / or leakage space. If the pressure rises significantly during the operation of the evaporative heat exchanger, this usually indicates a leak in the first flow path or the second flow path. The operation of the leak path is thus tested at each point of restarting the vehicle, especially in the case of a cold start.

  Further important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the description of the associated figures with reference to the drawings.

  It goes without saying that the features mentioned above or below can be used not only in the combinations given in each case, but also in other combinations or alone without departing from the scope of the invention.

FIG. 1 is a schematic view showing an evaporative heat exchanger according to the present invention. FIG. 2 is a schematic sectional view of the evaporative heat exchanger in the region of the first and second flow paths in an intact state. FIG. 3 is a view similar to FIG. 2, but the fluid plate is broken and the working medium is moved to the leakage flow path. FIG. 4 is a view similar to FIG. 3, but with the gas moving from the second flow path to the leakage flow path. FIG. 5 is a schematic diagram illustrating a suitable embodiment of a fluid plate according to the present invention. FIG. 6 is an exploded view of the evaporative heat exchanger. FIG. 7 is a schematic cross-sectional view of the evaporative heat exchanger in the region of the fluid inlet or outlet. FIG. 8 is a view similar to FIG. 7, but in the area of the discharge duct for leaking fluid. FIG. 9 is a pressure / time diagram showing different curves representing different operating states or leaks of the evaporative heat exchanger according to the invention.

  In the following, preferred exemplary embodiments of the invention are illustrated and described in more detail. The same reference signs indicate the same, similar or functionally identical components.

  According to FIG. 1, the evaporative heat exchanger 1 according to the present invention for evaporating a liquid working medium 2 (see FIGS. 2 to 4) comprises a first flow path 4 for guiding the working medium 2 and a gas. 6 is provided with a housing 3 in which a second flow path 5 for guiding 6 is provided. In this case, the working medium 2 is heated by heat transfer from the gas 6, for example from exhaust gas or supply air. According to the present invention, the first flow path 4 is formed by two cover plates 7 and 8 and a wave-like fluid plate 9 provided therebetween, and the fluid plate 9 includes two covers. Together with the plates 7 and 8, at least one leakage channel 10 and / or the leakage space 11 separated from the two channels 4 and 5 are simultaneously defined. The two cover plates 7 and 8 together with the fluid plate 9 provided therebetween form a plate bundle 12 as shown in FIGS. In this case, as can be seen from FIG. 5 in particular, each leakage channel 10 and the leakage space 11 are provided adjacent to the side of the first channel 5 or at the periphery thereof.

  The leakage flow path 10 according to the present invention creates a barrier between the two flow paths 4, 5, so that the working medium 2 cannot be directly mixed with the gas 6 and therefore cannot damage the internal combustion engine. It is. In the case of evaporative heat exchangers known from the prior art, the working medium to be evaporated flows into the exhaust gas in the event of a leak, for example combustion in an internal combustion engine when a fluorinated refrigerant, for example R245fa, is used Can thereby produce toxic hydrofluoric acid. This hydrofluoric acid will flow through the exhaust pipe and cause damage there. If an alcohol, such as ethanol or methanol, is used instead of such a refrigerant, if a leak occurs, the alcohol will be co-fired in the internal combustion engine, which will be reflected in a sudden increase in the output of the internal combustion engine. . Inexperienced drivers will be at increased risk of accidents as a result. However, as a result of the barrier according to the invention of the type of the leak channel 10 and the leak space 11, the mixing of the gas 6 and the working medium 2 is ensured if the fluid plate 9 breaks in virtually any manner. Can be prevented.

  In addition to providing a leakage channel 10 and / or a leakage space 11 (see FIG. 5), the strength of the material for the fluid plate 9 is greater than the strength of the cover plates 7, 8 connected to the fluid plate 9. Thus, the fluid plate 9 generally represents a kind of predetermined break point in the system of plate bundles 12. In a similar manner, such a predetermined break point may also be achieved by a wall thickness or material thickness of the fluid plate 9 that is smaller compared to the wall thickness or material thickness of the cover plates 7, 8.

  In this case, in FIG. 2, the evaporative heat exchanger 1 is shown in a normal operation state in which gas, in particular exhaust gas, flows through the second flow path 5 and transfers heat to the working medium 2 in the first flow path 4. Yes. In this case, a rib structure 13 may be provided in the second flow path 5, that is, between the two plate bundles 12, for better heat transfer. The connection of the fluid plate 9 to the two cover plates 7, 8 or the connection of the rib structure 13 to each cover plate 7, 8 is in this case preferably in a cohesive manner, for example by soldering Made by connection 14.

  FIG. 3 shows the case where the fluid plate 9 is broken, the central fluid plate 9 being broken, resulting in a more rigidly sized cover plate 7 deformation or upward bending. Also, the deformation of the cover plate 7 results in the separation of the solder connection 14, so that the working medium 2 in the first flow path 4 can flow into the leak flow path 10. There is no fluid connection with the second flow path 5 and thus with the gas 6.

  FIG. 4 shows the case where the fluid plate 9 is similarly damaged due to overload, in which a fluid connection between the second flow path 5 and the leak flow path 10 is created in the process. In this case, the gas 6 flowing out from the second flow path 5 can be discharged through the leak flow path 10 without being mixed with the working medium 2 in the first flow path 4. In the case of both failures shown in FIGS. 3 and 4, undesired mixing of the working medium 2 and the gas 6 and the resulting problems are reliably avoided.

  In view of the fluid plate 9 according to FIG. 5, the first flow path 4, the leakage flow path 10 extending at the periphery and the leakage space 11 arranged therebetween can be seen very clearly. A fluid inlet 15 and a fluid outlet 16 are seen in the same way, through which the working medium 2 can be supplied to and discharged from the fluid plate 9 again. The fluid plate 9 also has a first opening 17 through which the leakage channel 10 and the leakage space 11 are connected to a (leakage) discharge duct 18 (see FIG. 1). A plurality of cover plates 7 and 8 provided opposite to each other in two adjacent plate bundles 12 additionally have a second opening 19 to form a discharge duct 18, in particular a leak discharge duct 18. A leakage bush 20 is provided between the two second openings 19. In the assembled plate bundle 12, the first opening 17 is aligned with the second opening 19 and the leakage bush 20, resulting in the formation of the discharge duct 18.

  Further considering FIG. 6, it can be seen that the cover plates 7 and 8 each have a third opening 21 for guiding the working medium 2 through the first flow path 4. Between adjacent cover plates 7 and 8 of two adjacent plate bundles 12, each is integrally connected by a fluid bush 22, and the fluid bush 22 is separated from the first flow path 4. The fluid bush annular passage 23 is at least partially extending in the circumferential direction, and the fluid bush annular passage 23 is connected to the leakage flow path 10 and / or the leakage space 11 in the fluid plate 9 of the plate bundle 12. Yes. As a result, it is also possible to create a protective means against the working medium 2 undesirably flowing out of the fluid bushing 22. In this case, the third opening 21 has a corresponding fluid supply duct 24 and fluid discharge duct 25 disposed between them in the fluid plate 9, and a fluid inlet 15 and a fluid outlet 16 provided in a side-by-side manner. Form.

  FIG. 7 shows a cross-sectional view of the evaporative heat exchanger 1 according to the invention in the region of the fluid supply duct 24 and the fluid discharge duct 25. In this case, the uppermost fluid bush 22 is welded to the housing 3 in a liquid tight manner via a weld connection 26. In each case, a plate bundle 12 with two cover plates 7 and 8 and a fluid plate 9 provided or soldered between them is seen between two adjacent fluid bushings 22.

  FIG. 8 shows a cross-sectional view of the evaporative heat exchanger 1 according to the invention in the region of the discharge duct 18, the uppermost leakage bush 20 being also welded to the housing 3 in a liquid-tight manner via a weld connection 26. Has been. In this case, individual plate bundles 12 composed of two cover plates 7 and 8 and a fluid plate 9 provided between them are soldered together and are liquid-tightly connected via respective soldering connections 14. And soldered to each leakage bush 20. In this case, the uppermost leakage bush 20 is also referred to as a housing leakage bush 27. The housing leakage bush 27 is connected to the periphery or the periphery by a pipe line 28 (see FIG. 1), and the pipe line 28 extends to the outside of the evaporative heat exchanger 1. The conduit 28 or the exhaust duct 18 is configured to measure the pressure and / or flow rate and / or chemical composition of the fluid in the conduit 28, i.e., in particular in the leak passage 10 or in the exhaust duct 18. A sensor 29 may be provided.

  A working medium configured to determine a value of the pressure, flow rate and / or chemical composition of a signal detected by the sensor 29, in particular a fluid in the conduit 28, in particular a leaking fluid, and based on the detected signal An open loop and / or closed loop controller 30 is also provided for open loop / closed loop control of a pump (not shown) and / or an exhaust gas recirculation valve (also not shown). It may be.

  As long as the evaporative heat exchanger 1 is turned off and is the same as the ambient temperature, an atmospheric pressure of approximately 1 bar is normally applied to the sensor 29. This is illustrated by curve A in FIG. When the evaporative heat exchanger 1 is activated, the pressure in the conduit 28 and in the leakage channel 10 rises to about 1 to 1.5 bar due to temperature-related air expansion, which is the curve in FIG. Indicated by B. If the pressure does not increase with the evaporative heat exchanger 1 in operation, this is also indicated by curve A in FIG. 9 and the sensor 29 is defective or there is a leak in the conduit 28 and the leak passage 10. is there. If a leak occurs in the fluid plate 9, the pressure rises significantly when the working medium 2 flows into the leak channel 10, which is indicated by curve C in FIG. When the gas 6 ruptures towards the two flow paths 5 and therefore the gas 6 flows into the leak flow path 10, it is somewhat lower, which is indicated by the curve D in FIG. In general, the operation of the leakage flow path 10 is tested at each point when the internal combustion engine or system is restarted, so that high operational reliability can also be ensured. In addition, it is immediately possible to clarify the conclusion about the type of failure from the shape of the curve.

  In general, the evaporative heat exchanger 1 according to the present invention has the following advantages. That is, undesirable mixing of the working medium 2 and the gas 6, such as exhaust gas or supply air, is avoided, there is no health risk when the refrigerant is used, and the alcohol-based working medium 2 is used. There is no safety risk in the process and the continuous testability of the leak concept function.

Claims (11)

An evaporation heat exchanger (1) for evaporating the liquid working medium (2),
A housing (3) having a first channel (4) for guiding the working medium (2) and a second channel (5) for guiding the gas (6) provided therein;
Heat transfer from the gas (6) to the working medium (2) is possible,
The first flow path (4) is formed by two cover plates (7, 8) and a wave-like fluid plate (9) provided between the two cover plates,
The fluid plate (9), together with the two cover plates (7, 8), at least one leakage channel (10) separated from the first and second channels (4, 5) and / or An evaporative heat exchanger characterized in that the leakage space (11) is partitioned at the same time. In claim 1,
The at least one leak channel (10) and / or the leak space (11) is provided adjacent to the side of the first channel (4) or at the periphery of the first channel (4). An evaporative heat exchanger. In claim 1 or 2,
The material strength of the fluid plate (9) is lower than the strength of the cover plates (7, 8) provided on the fluid plate (9),
And / or
The evaporative heat exchanger characterized in that the fluid plate (9) has a thinner wall thickness or material thickness than the cover plates (7, 8) respectively provided on the fluid plate (9). . In any one of Claims 1-3,
Two cover plates (7, 8) in each case form a plate bundle (12) with a fluid plate (9) provided between the two cover plates;
The plate bundle (12), evaporation heat exchanger, characterized in that it comprises at least one leakage channel (10) at least partially surrounds the peripheral region. In claim 4,
The evaporative heat exchanger (1) comprises a plurality of plate bundles (12) stacked on top of each other and in each case provided with a second flow path (5),
The leakage flow path (10) and / or the leakage space (11) in the fluid plate (9) has a first opening (17);
A plurality of cover plates (7, 8) provided opposite to each other in two adjacent plate bundles (12) each have a second opening (19),
An evaporative heat exchanger characterized in that a discharge bush (20) for forming a discharge duct (18), in particular a leak discharge duct (18), is provided between the second openings (19). In claim 5,
It said first opening (17), evaporation heat exchanger, characterized in that it is directly connected to the upper Symbol leakage bushing (20). In any one of Claims 4-6,
A plurality of cover plates (7, 8) each having a third opening (21) for guiding the working medium (2) through the first flow path (4);
The third opening (21) is integrally connected by a fluid bush (22) between the cover plates (7, 8) facing each other of two plate bundles (12) provided adjacent to each other. And
The fluid bush (22) has a fluid bush annular path (23) separated from the first flow path (4) and extending at least partially in the circumferential direction;
The fluid bush annular path (23) is connected to the leak channel (10) and / or the leak space (11) in the fluid plate (9) of the plate bundle (12). Evaporative heat exchanger. In claim 5 or 6 ,
The housing (3) is in the first and / or second opening (17, 19) in the cover plate (7, 8) of the plate bundle (12) provided adjacent to the housing (3). Evaporative heat exchanger, characterized in that it has a housing opening connected via a housing leak bush (20, 27). In claim 8,
The housing leakage bush (27) and all other leakage bushes (20) form the discharge duct (18) for guiding the fluid,
A pipe line (28) connected to the periphery or periphery can be attached to the housing leakage bush (27),
The conduit (28) has a sensor (29) configured to measure the pressure and / or flow rate and / or chemical composition of the fluid in the conduit (28). Evaporative heat exchanger. In any one of Claims 4-9,
In each case, a rib structure (13) is provided in the second flow path (5) between the two plate bundles (12) ,
An evaporative heat exchanger, wherein the fluid plate (9) is soldered and / or welded between two cover plates (7, 8). Oite to claim 9,
The signal detected by the sensor (29), in particular configured to determine the value of the pressure, flow rate and / or chemical composition of the fluid in the conduit (28) and based on the detected signal Characterized in that an open-loop and / or closed-loop control device (30) is provided for the open-loop / close-loop control of the pump for delivering the working medium (2) and / or the exhaust gas recirculation valve. Evaporative heat exchanger.