DE102010042558A1 - Device for waste heat utilization - Google Patents

Abstract

A device (1) for using waste heat comprises a steam circuit (2) and a gas storage device (15). The gas accumulator (15) is connected to a high pressure area (11) of the steam circuit (2) via a connecting line (16) with a shutoff valve (17). By opening the shut-off valve (17), air from the high-pressure area (11) of the steam circuit (2) can be stored in the gas accumulator (15) during operation.

Description

State of the art

The invention relates to a device for waste heat recovery. Specifically, the invention relates to a device for waste heat recovery, which is used in an air-compressing, self-igniting internal combustion engine or a mixture-compression, spark-ignited internal combustion engine.

In a steam cycle for generating mechanical power, it is conceivable that this is not designed hermetically sealed, but has a differential pressure-dependent leakage. As a result, depending on the pressure gradient between the steam circuit and the environment, working fluid can be lost or air can enter the system. This has the disadvantage that escaping working fluid must be refilled regularly, which causes costs and makes a refill required. In addition, depending on the working fluid, emission regulations may also be legally affected or the lubricant of a bearing or other lubrication points, which may be provided at the sealing point, may be contaminated. Incoming air can significantly deteriorate a condenser performance, because it accumulates there and fills large parts of the condenser volume, which are then no longer available for condensation. Therefore, a vacuum pump is required, which pumps off the air before commissioning and also during operation. It is also conceivable that the air is displaced from the steam circuit by the steam circuit is completely filled with working fluid at a standstill. When heating the system, the liquid is partially displaced by the steam forming in a designated tank. However, this has the disadvantage that large amounts of fluid in the steam circuit are required, which slow down the warm-up and operating point change significantly, and that an additional volume of construction for the fluid tank is required and there is a corresponding additional weight. In addition, this concept also has the disadvantage that, when the system is turned off, there are no sufficient air cushions in the lines and components, so that damage is possible during freezing.

Disclosure of the invention

The inventive device for waste heat recovery with the features of claim 1 has the advantage that an improved structure and improved functionality are possible. Specifically, leakage of working fluid from the steam circuit can be reduced and, optionally, additional components can be saved. In particular, in a water-based working fluid damage can be avoided by freezing and it can also be a fast thawing possible when restarting the device for waste heat recovery.

By the gas storage can be stored in an advantageous manner air or another gas. As a result, vacuum pumps for pumping out the air from the system can be saved, so that there is a cost savings. In addition, part of the working fluid is lost when pumping out the air from the system, which is avoided by the absence of the vacuum pump from the outset. A leakage of the working fluid can be minimized thereby. In particular, water or a mixture of water and an additive can be used as the working fluid. This can be done at low ambient temperatures, an expansion of the freezing water. In this case, a gas cushion can be realized in a suitable manner by the gas stored in the gas storage in the components of the gas circuit, so that this expansion is possible without damaging the components of the steam circuit. In addition, a fast thawing can be made possible when restarting.

The measures listed in the dependent claims advantageous refinements of the device specified in claim 1 for the use of waste heat are possible.

Preferably, the steam circuit is not completely filled with the working fluid to displace all of the air therefrom, but only as much working fluid is charged as is required to operate the steam process and to compensate for leakage. The remaining volume of the steam circuit remains filled with air. Thus, at standstill there is almost ambient pressure in the steam circuit, whereby the leakage and the sealing effort are minimized.

In addition, the air in the condenser is promoted during commissioning in an advantageous manner by a pump, in particular a fluid pump in the high pressure region of the steam cycle. Here, the air is separated into the gas storage, where it remains during operation of the device. When the pressure drops again when the device is switched off, the air expands again, thus preventing a significant pressure gradient between the steam circuit and the environment. As a result, the leakage is minimized.

It is advantageous that the gas reservoir is connected via a connecting line to the high-pressure region and that a mean diameter of the connecting line is much smaller than a length of the connecting line. This can be achieved be that accumulates in operation as little air in the flowing past the reservoir working fluid and thus enters the condenser, from where the air would have to be pumped out again. By connecting the gas reservoir via the long in comparison to the average diameter connection line with the small inner cross section, the surface (interface) between the air and the liquid as small as possible. A further advantageous measure to keep the surface between the air and the liquid as small as possible, is that the gas storage has a mean diameter which is much smaller than a length of the gas reservoir.

Furthermore, it is advantageous that at least one valve is arranged in the connection between the gas reservoir and the high-pressure region. A complete media separation can be achieved by a shut-off valve in the connection between the gas storage and the high pressure area. The shut-off valve is then opened only for intentional storage or discharge of the air in or out of the gas storage. For example, the shut-off valve can be opened during commissioning during the venting phase and closed in operation after complete venting. If, after a long period of operation, air collects again in front of the shut-off valve, this air can be stored in the gas storage tank by opening it briefly in an operating phase in which the operating pressure is higher than the injection pressure in the gas storage tank.

Furthermore, it is advantageous that the valve in the connection between the gas storage and the high-pressure region is designed as a media-separating valve. As a result, even better media separation can be achieved. For example, the media-separating valve can be designed as a float valve corresponding to an automatic ventilation valve for heating systems.

Furthermore, it is advantageous that at least one separating device is provided and that the gas reservoir is connected to the high-pressure region via the separating device. In this case, the separating device can be configured advantageously as a settling chamber. The separation of the air can be effected by gravity, wherein the calming chamber is configured for example by an upward funnel in an extended fluid line. It is also advantageous that the separating device is designed as a separating device. In this case, for example, a cyclone principle, a gas-permeable, but liquid-blocking membrane, a climate membrane or the like can be used. Thus, the deposition of air through the separator can be favored.

It is also advantageous that the steam circuit has an expansion device and that a displacement volume of the expansion device can be limited so that a predetermined injection pressure for the high-pressure region can be set. This can be generated without additional components required for storing the air in the gas storage Einspeicherdruck. It is also advantageous for this purpose that the steam circuit has an evaporator and a valve which is arranged in the high-pressure region, in particular in front of the evaporator, and via which a injection pressure for the high-pressure region can be set. A particular advantage of the valve disposed in front of the evaporator is that the evaporator has a relatively low pressure and can therefore outgas air enriched in the water. Advantageously, this can be used to limit a swallowing volume. The arrangement of the valve in front of the evaporator has the advantage that a relatively small valve can be used.

Moreover, it is advantageous that the steam circuit has a condenser, that a pump is provided, that a suction side of the pump is connected to the condenser, that a delivery side of the pump is connected to the gas accumulator and that the suction side of the pump is thus connected to the condenser is that gas from a forming in a condensation of a working gas cushion is sucked into the gas storage. As a result, gas forming in the condenser, in particular air, can be led directly into the gas reservoir. At the same time, the condensing capacity available for the condensation is optimized at the same time, since the gas cushion is reduced. At standstill of the device, the steam circuit is largely filled with air, with little collected water is provided. However, it is unfavorable at start of operation, if air is in the condenser, because then there is air on the walls of the condenser. Therefore, it is also advantageous that air is sucked out of the condenser during startup. The air can also be advantageously conveyed into the gas storage during commissioning of the device and also during operation by the fluid pump, which can also convey gases, or by an additional vacuum pump.

It is also advantageous that the steam circuit has a condenser and a suction device arranged downstream of the condenser, that a suction line of the suction device opens into the condenser and that an opening point of the suction line is arranged on the condenser such that gas emerges from a condensate of a working fluid forming gas cushion is sucked into the steam circuit. This can be done in a simple manner an extraction of the collecting air in the condenser. Here, for example, a Suction jet principle are exploited. Thus, the condensation performance of the capacitor is optimized.

It is advantageous that the device is at least substantially filled with a working fluid and a gas as a filling. For example, the gas may comprise air and / or nitrogen. The device then contains, in addition to the working fluid, a gas which limits the negative pressure during a system shutdown. The limitation is preferably based on the ambient pressure.

It is also advantageous that the working fluid can be collected in an exhaust gas heat exchanger and / or in a heatable reservoir. The working fluid then collects in the plant standstill in the exhaust gas heat exchanger or in the heatable reservoir. In the plant standstill, the working fluid, for example water, is collected in an area where it can be quickly warmed up or thawed. Particularly suitable for this purpose are the exhaust gas heat exchanger, which is made frost-proof, or the heatable reservoir.

The working fluid, in particular the water, can be pumped out by a suitable arrangement of the components of the device into the evaporator, in particular into an exhaust gas heat exchanger, by a pump, in particular the fluid pump, or by the gas, in particular the air, in the gas reservoir in the Evaporator be blown, which is possible by opening the associated valve. It is therefore advantageous that the working fluid flows in an installed position by gravity in an exhaust gas heat exchanger and / or that the working fluid is at least partially conveyed by means of a fluid pump in the exhaust gas heat exchanger and / or the gas from the gas storage is used to the working fluid from at least a component, in particular a condenser and / or a fluid pump to blow out. When blowing out gas flows from the gas storage in the steam circuit due to the pressure difference. Here, the gas can flow in the two possible directions through the steam circuit. As a result, particularly remaining fluid residues which collect, for example, in the form of small puddles in the steam circuit, can be transported away. Specifically, sensitive components that are disturbed or damaged in function by freezing water or the like may be blown out. For example, it is advantageous to blow free the fluid pump or the condenser. The outflow of gas ends when the pressures in the steam circuit and in the gas storage have become equal to each other.

Brief description of the drawings

Preferred embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawings, in which corresponding elements are provided with corresponding reference numerals. It shows:

1 a device for waste heat recovery in a schematic representation according to a first embodiment of the invention;

2 a device for waste heat recovery in a schematic representation according to a second embodiment of the invention and

3 a gas storage and a connecting line of a device for the use of waste heat in an excerpt, schematic representation according to a possible embodiment.

Embodiments of the invention

1 shows a device 1 for waste heat utilization in a schematic representation according to a first embodiment of the invention. The device 1 for waste heat utilization can be used in particular for an internal combustion engine. In this case, for example, the exhaust gases emitted by the internal combustion engine can be deprived of energy. Specifically, the device is suitable 1 for waste heat utilization for automotive applications. The internal combustion engine can in this case be configured in particular as an air-compressing, self-igniting or mixture-compressing, spark-ignited internal combustion engine. The device 1 for waste heat utilization of the invention, however, is also suitable for other applications.

The device 1 has a steam circuit 2 with an evaporator 3 , an expansion device 4 and a capacitor 5 on. The evaporator 3 can be configured for example as an exhaust gas heat exchanger. In the evaporator 3 a liquid working fluid is evaporated. In this case, for example, the waste heat of the internal combustion engine, in particular the energy of the hot exhaust gases, used for vaporizing the working fluid. The expansion device 4 is the evaporator 3 downstream. About a line 6 the vaporized working fluid becomes the expansion device 4 guided. As a result, the expansion device 4 driven. For example, the expansion device 4 a turbine that drives an electric generator for generating electrical energy. The capacitor 5 is the expansion device 4 downstream. The relaxed over the expansion device, gaseous working fluid is via a line 7 in the condenser 5 guided. In the condenser condenses the working fluid. Behind the capacitor 5 is a pump 8th of the steam circuit 2 arranged. This is done via a suction line 9 the liquid working fluid from the condenser 5 by the pump 8th sucked. The pump 8th promotes in a direction 10 that return the working fluid to the evaporator 3 leads. This is the steam cycle 2 closed.

The steam circle 2 may have one or more leaks. An example of such a leakage point is a shaft seal of the expansion device 4 , By such leaks is usually air in the steam circuit 2 , This will be at a standstill of the device 1 limited forming vacuum. In extreme cases, it is within the steam circle 2 here the same pressure as outside. As a result, fluid leakage to the outside is minimized. During commissioning of the device 1 First, the air is pumped through 8th , which can also promote gaseous media in addition to the working fluid, from the condenser 5 in a high pressure area 11 the line 10 of the steam circuit 2 promoted. This is in the high pressure area 11 set a Einspeicherdruck.

The injection pressure in the high pressure area 11 can be set in different ways. One possibility is that a displacement of the expansion device 4 is limited. Another possibility is that in the line 10 a valve 12 in front of the evaporator 3 is arranged. About the valve 12 then the desired Einspeicherdruck can be generated and adjusted. An advantage of the valve 12 in front of the evaporator 3 is that in the evaporator 3 a lower pressure prevails and thus can outgas enriched air in the working fluid.

The device 1 has a gas storage 15 on, which serves for storing a gas, in particular of air. The gas storage 15 is sized so that all the air in the device 1 For example, the given at a pressure of about 100 kPa (1 bar) air capacity, can be added at the selected injection pressure. The pressure level for storage should be chosen to be slightly lower than the operating pressure at the frequently approached operating points, so that even during operation still residual air can be stored.

The design of the device 1 takes place so that it can be achieved during operation that as little air as possible in the gas storage 15 Enriching passing working fluid. If in fact air in the through the pipe 10 accumulates flowing working fluid, then this air passes back into the condenser, from where it would have to be pumped out again. In order to avoid the accumulation of the working fluid, the interface between the air and the working fluid is kept as small as possible. The gas storage 15 is over a line 16 to the high pressure area 11 connected. Here, the inner diameter of the line 16 much smaller than the length of the pipe 16 to choose. Here, the gas storage 15 over the line 16 directly to the line 10 be connected.

Besides, it is possible that in the line 16 a shut-off valve 17 is arranged. This can be done a substantial separation of the media air and working fluid. The shut-off valve 17 is then only for intentional storage or discharge of air in or out of the gas storage 15 open. During operation, the shut-off valve remains 17 After completion of venting usually closed. However, after a longer period of operation, air collects again in front of the shut-off valve 17 , then this air can be opened by briefly opening in an operating phase in which the operating pressure is higher than the Einspeicherdruck in the gas storage 15 is, in addition to the gas storage 15 be stored.

Another possibility for media separation is that the gas storage 15 additionally or alternatively via a media-separating valve 18 with the high pressure area 11 connected is. As a valve 18 For example, a float valve can be used.

The steam circle 2 may also have a separator 19 exhibit. The separator 19 can use gravity to separate the media. For example, the separator 19 an upward funnel 20 include, in the flow direction of the working fluid behind the pump 8th is arranged. Through the funnel 20 an extended fluid line is formed, which acts as a calming chamber. The entrained air can then be up from the working fluid to the line 16 reach.

Additionally or alternatively, the separation device 19 also exploit another principle, in particular a cyclone principle. Furthermore, a gas-permeable, but liquid-blocking membrane or the like in the separation device 19 be integrated.

In this embodiment, the device 1 also a suction device 21 on. The suction device 21 is in the steam circle 2 arranged. This leads a suction line 22 the suction device 21 to the capacitor 5 , The suction line 22 leads to a suitable confluence point 23 in the condenser 5 , There is also an end 24 the suction line 22 in front of the pump 8th in the suction line 9 arranged. About the suction lines 9 . 22 a suction pump is realized. The suction device 21 works according to the suction jet principle. About the suction line 9 is through the pump 8th liquid working fluid from the condenser 5 sucked. The estuary 23 the suction line 22 is at one point of the capacitor 5 arranged on which preferably accumulates air. This may be, for example, the area above the liquid level of the working fluid. By that at the end 24 the suction line 22 By-passing working fluid is a negative pressure in the suction line 22 generated. Thus, the air from the condenser 5 at the confluence 23 the suction line 22 sucked and into the suction line 9 guided. The pump 8th thus allows that in addition to the working fluid and the air is sucked with.

In this embodiment, the suction line is used 9 at least essentially as a suction line 9 for liquid working fluid, while the suction line 22 at least essentially as air suction 22 serves. The pump 8th This is suitable both for conveying liquid working fluid and for gas production.

When parking the device 1 becomes the working fluid of the steam circuit 2 preferably collected at a point where it can be reheated or thawed as quickly as possible when restarting. For this purpose, the evaporator is particularly suitable 3 , Therefore, the evaporator 3 structurally preferably designed so that it is not damaged by the freezing working fluid. This can be achieved by turning off the device 1 Air from the gas storage 15 is omitted, at least partially in the evaporator 3 arrives. Accordingly, in other components in which it can be damaged by freezing working fluid, a gas cushion can be created, which allows expansion of the freezing working fluid.

The device 1 can be constructively designed so that the evaporator 3 is arranged at the lowest point and the working fluid at a corresponding routing by gravity in the evaporator 3 expires. If this is structurally not possible, then the working fluid can be used as a fluid pump 8th serving pump 8th in the evaporator 3 be pumped. Remaining fluid residues in the pipes or components of the steam circuit 2 can by opening the shut-off valve 17 after the vapor pressure has dropped in the steam circuit 2 be blown out.

To complete a shutdown as quickly as possible, the condenser cooling through the capacitor 5 be maintained until the residual heat from the device 1 is largely dissipated and no working fluid condenses more, by the pump 8th would have to be pumped out.

2 shows a device 1 for waste heat utilization in a schematic representation according to a second embodiment. In this embodiment, a pump 30 provided over the air from the condenser 5 is pumpable. This is a suction side 31 the pump 30 over the suction line 22 at the confluence 23 with the capacitor 5 connected. A sponsorship page 32 the pump 30 is over a gas pipe 33 , which in particular serves for the passage of air, with the line 16 connected. The gas line 33 is hereby preferably between the shut-off valve 17 and the gas storage 15 with the line 16 connected. The gas line 33 but also between the high pressure area 11 and the shut-off valve 17 with the line 16 be connected. In an embodiment in which no shut-off valve 17 is provided, is the gas line 33 in a suitable way with the line 16 connected.

In operation of the device 1 can air out of oneself in the condenser 5 forming air cushion are sucked and directly into the gas storage 15 be pumped. The pump 30 can be used as a vacuum pump 30 be designed.

It is advantageous that the gas storage 15 over the connecting line 16 with the high pressure area 11 is connected and that a mean diameter of the connecting line 16 much smaller than a length of the connecting line 16 , Additionally or alternatively, it is advantageous if the gas storage 15 has a mean diameter that is much smaller than a length of the gas reservoir 15 ,

It is also advantageous that the gas storage 15 is designed so that for a volume of gas storage 15 and a length of the gas storage 15 the following relation (1) is fulfilled: Volume <(x / 2) ^ 2 · length ^ 3 · Pi, (1) where the positive factor x is much smaller than 1: 0 <x << 1, (2) and where Pi is the Ludolfian number (3.1415 ...).

Here, both the volume and the length can be determined relatively easily, so that a suitable embodiment can be selected and checked in a simple manner. The condition (1) with the auxiliary control (2) can both for a suitable selection of the volume of the gas storage 15 and the length of the gas storage 15 as well as for a suitable selection of the volume of the connecting line 16 and the length of the connection line 16 serve. Thus, the gas storage 15 and / or the connection line 16 be configured advantageously, if each of the operation (1) with the auxiliary control (2) suffice.

For the special case of a cylindrical volume, the diameter is then smaller than x times the length, where x furthermore satisfies the condition (2): Diameter <x · length. (3)

On the other hand, it is also possible to determine a mean diameter from any volume: Volume = length · Pi · (average diameter / 2) ^ 2. (4)

3 shows a gas storage 15 and a connection line 16 a device 1 for waste heat utilization in an excerpt, schematic, not to scale representation according to a possible embodiment. Here is the gas storage 15 as a cylindrical gas storage 15 designed. The connection line 16 is as a cylindrical connecting line 16 designed.

The gas storage 15 has a mean diameter 40 due to the cylindrical configuration equal to the diameter (inner diameter) 40 of the gas storage 15 is. Corresponding is also a mean diameter 41 the connection line 16 equal to the diameter (inner diameter) 41 the connection line 16 ,

The gas storage 15 also has a length 42 on. Furthermore, the connection line shown in sections 16 a length 43 on. Due to gravity is located in an upper part 44 of the gas storage 15 Air, while in a lower part 45 of the gas storage 15 a liquid is located. Also the connection line 16 is filled with the liquid. Preferably, the gas storage 15 to 2/3 filled with air. There is an interface between the air and the liquid 46 , The air can be at the interface 15 go into solution in the liquid. However, gravity acts to diffuse the dissolved air to and through the connecting pipe 16 opposite.

In the case of the cylindrical configuration, the size of the interface 46 regardless of the size of the liquid-filled part 45 constant. The gas storage 15 is dimensioned for this so that it is never completely full of air during operation. At standstill, the liquid, however, from the gas storage 15 pressed.

The geometry of the gas storage 15 is chosen so that the condition (3) is satisfied with the constraint (2) and thus the interface 46 is small. As a result, the solution of air in the liquid is reduced as much as possible.

The invention is not limited to the described embodiments. In particular, the basis of the 1 and 2 described embodiments of the device 1 be modified by a waiver, an exchange, a supplement or a combination of components. As a result, an adaptation to the particular application is possible.

Claims (14)

Contraption ( 1 ) for waste heat use with a steam cycle ( 2 ) and a gas storage ( 15 ), the gas storage ( 15 ) with a high pressure area ( 11 ) of the steam circuit ( 2 ) connected is. Apparatus according to claim 1, characterized in that the gas storage ( 15 ) via a connecting line ( 16 ) with the high pressure area ( 11 ) and that a mean diameter ( 41 ) of the connecting line ( 16 ) is much smaller than a length ( 43 ) of the connecting line ( 16 ). Apparatus according to claim 1 or 2, characterized in that in the connection between the gas storage ( 15 ) and the high pressure area ( 11 ) at least one valve ( 17 . 18 ) is arranged. Apparatus according to claim 3, characterized in that the valve as a shut-off valve ( 17 ) or as a media-separating valve ( 18 ) is configured. Device according to one of claims 1 to 4, characterized in that the gas storage ( 15 ) an average diameter ( 40 ) which is much smaller than a length ( 42 ) of the gas storage ( 15 ). Device according to one of claims 1 to 5, characterized in that at least one separating device ( 19 ) is provided and that the gas storage ( 15 ) via the separating device ( 19 ) with the high pressure area ( 11 ) connected is. Apparatus according to claim 6, characterized in that the separating device ( 19 ) is designed as a calming chamber or as a separator. Device according to one of claims 1 to 7, characterized that the steam cycle ( 2 ) an expansion device ( 4 ) and that a displacement volume of the expansion device ( 4 ) is limited so that a predetermined Einspeicherdruck for the high pressure area ( 11 ), and / or that the steam cycle ( 2 ) an evaporator ( 3 ) and a valve ( 12 ), which in the high pressure area ( 11 ), in particular in front of the evaporator ( 3 ), and via which a Einspeicherdruck for the high pressure area ( 11 ) is adjustable. Device according to one of claims 1 to 8, characterized in that the steam cycle ( 2 ) a capacitor ( 5 ) has a pump ( 30 ) is provided that a suction side ( 31 ) of the pump ( 30 ) with the capacitor ( 5 ), that a production site ( 32 ) of the pump ( 30 ) at least indirectly with the gas storage ( 15 ) and that the suction side ( 31 ) of the pump ( 30 ) so with the capacitor ( 5 ), that gas from a forming in a condensation of a working gas cushion in the gas storage ( 15 ) is sucked. Device according to claim 9, characterized in that the pump ( 30 ) at a commissioning of the steam cycle ( 2 ) a suction of air from the condenser ( 5 ). Device according to one of claims 1 to 10, characterized in that the steam circuit is a capacitor ( 5 ) and a capacitor ( 5 ) downstream suction device ( 21 ), that a suction line ( 22 ) of the suction device ( 21 ) in the condenser ( 5 ) and that an estuary ( 23 ) of the suction line ( 22 ) so on the capacitor ( 5 ) is arranged, that gas from a forming in a condensation of a working gas cushion in the steam cycle ( 2 ) is absorbable. Device according to one of claims 1 to 11, characterized, that the device is at least substantially filled with a working fluid and a gas and or the gas has air and / or nitrogen. Apparatus according to claim 12, characterized in that the working fluid in an evaporator ( 3 ) and / or in a heatable reservoir ( 3 ) is collectable. Apparatus according to claim 12 or 13, characterized in that the working fluid in a mounting position by gravity in an evaporator ( 3 ) and / or that the working fluid at least partially by means of a fluid pump ( 8th ) in the evaporator ( 3 ) and / or that the gas from the gas storage ( 15 ) is usable to the working fluid from at least one component, in particular a capacitor ( 5 ) and / or a fluid pump ( 8th ), blow out.

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