Patent Publication Number: US-10323889-B2

Title: Container for a waste heat utilization circuit

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to International Application No. PCT/EP2016/068072 filed on Jul. 28, 2016, and to German Application No. DE 10 2015 215 063.1 filed on Aug. 6, 2015, the contents of each of which are hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The invention relates to a container for a waste heat utilization circuit and a waste heat utilization circuit with such a container. The invention further relates to a waste heat utilization device with such a waste heat utilization circuit. 
     BACKGROUND 
     In internal combustion engines, in particular in piston engines, mechanical driving power is generated by burning a fuel. In so doing, a majority of the chemical energy contained in the fuel is released as heat, which frequently remains unused. Frequently, even a portion of the usable driving power must be used for cooling the internal combustion engine and its units. With a waste heat utilization device, the waste heat occurring in an internal combustion engine can be used, for example, in order to provide further driving power or electrical energy. Hereby, the overall energy efficiency of the internal combustion engine can be improved. 
     Such waste heat utilization devices are known for example from EP 2 573 335 A2 and from DD 136 280. 
     Waste heat utilization devices can be configured as a circuit process in the form of a so-called Carnot process. The so-called Clausius-Rankine process is a special Carnot process. In such a Clausius-Rankine process, a working medium circulates in a waste heat utilization circuit. In the waste heat utilization circuit there is situated an evaporator for evaporating the working medium, which extracts heat for this from the internal combustion engine. Downstream of the evaporator there is situated in the waste heat utilization circuit an expansion machine for the relieving of the working medium to a low pressure. Downstream of the expansion machine there is situated in the waste heat utilization circuit a condenser for the liquefying of the working medium. Downstream of the condenser, a compression machine is to be found in the waste heat utilization circuit for compressing the working medium to a high pressure. From the compression machine, the working medium arrives at the evaporator again. In relieving the pressure of the working medium in the expansion machine, thermal energy is converted into mechanical driving energy, which can be used directly as mechanical driving power, or can be converted into electrical energy by means of a generator. The heat for the evaporating of the working medium can be extracted for example from the waste gas of the internal combustion engine. A pump arranged downstream of the condenser in the waste heat utilization circuit serves for the conveying of the working medium. 
     It proves to be disadvantageous in such a conventional waste heat utilization circuit that undesired cavitation effects can be brought about through the working medium in the pump. These can lead to a damage to the components of the pump which are mechanically in contact with the working medium. In extreme cases, this can even result in a destruction of the pump. 
     It is therefore an object of the present invention to create a device for use in a waste heat utilization circuit, which counteracts the formation of undesired cavitation effects in the pump which is driving the working medium. 
     This problem is solved by the subject of the independent claim(s). Preferred embodiments are the subject of the dependent claims. 
     SUMMARY 
     Accordingly, a basic idea of the invention is to provide an equalization container for a waste heat utilization circuit—hereinafter designed as “container” for the sake of simplicity—which brings about a supercooling of the working medium, so that the latter flows as far as possible only in liquid phase through the pump. In this way, undesired cavitation effects can be prevented. 
     According to the invention, it is proposed to equip the container with a, preferably rigid, housing, which can be flowed through by a working medium of a waste heat utilization circuit. In the housing, in turn, a fluid-tight, heat-conductive and volume-variable sheath is arranged. This serves to vary the effective volume of the housing interior, delimited by the housing, which is of significant importance for the supercooling of the working medium which is aimed for. The working medium of the waste heat utilization circuit can be introduced directly into the housing. Whilst flowing through the housing, the working medium can enter into thermal interaction with the auxiliary medium via the heat-conductive sheath. Typically, the working medium on entry into the container has a higher temperature here than the auxiliary medium which is present, stationary, in the container. Owing to the heat-conductive characteristics of the sheath, heat is transferred from the warmer working medium to the colder auxiliary medium, until a temperature equilibrium occurs between working medium and auxiliary medium. When the temperature of the auxiliary medium reaches its boiling temperature here, the liquid phase of the auxiliary medium begins to evaporate at least partially. This leads to an enlargement of the sheath interior delimited by the sheath through expansion of the volume-variable sheath. This leads, in turn, to an increase in the pressure of the working medium, until an equilibrium has occurred in the auxiliary medium between liquid and gaseous phase. In this state of equilibrium, the fluid pressure of the working medium corresponds to the boiling pressure of the auxiliary medium. When the working medium and the now auxiliary medium are selected such that the boiling temperature of the auxiliary medium is less than that of the working medium, it can be permanently achieved that the working medium flows, as desired, in the liquid state of supercooling through the waste heat utilization circuit. In particular, it can be ensured that the desired supercooling level occurs without active assistance from outside. 
     When a working medium with reduced temperature arrives into the housing interior from a condenser of the waste heat utilization circuit upstream of the container, then the temperature of the auxiliary medium also decreases within a short time through heat transmission, and a portion of the gaseous phase contained therein condenses to the liquid phase, whereby the volume of the sheath interior is reduced. In so doing, a displacement of the working medium from the condenser into the container is brought about, whereby the supercooling is reduced. This takes place until the supercooling has again reached the desired extent. 
     When, on the other hand, working medium arrives in vapour form out from the condenser into the housing interior, then the fluid pressure increases immediately through the additional vapour volume, whereby the complete condensing is re-established at the condenser outlet automatically without the assistance of an external regulation, therefore without the assistance of an external regulation. 
     In operation of the waste heat utilization device, a vapour- and a liquid phase of the working medium can occur in the equalization container, integrated into the waste heat utilization circuit, such that a condensation pressure results, at which the supercooling of the working medium remains substantially constant. When a supercooled, liquid working medium arrives out from the condenser into the equalization container, a portion of the vapour contained therein condenses out, and the fluid pressure of the working medium in the equalization container decreases. When, on the other hand, vapour from the condenser arrives into the equalization container, the fluid pressure in the equalization container increases owing to the additional vapour volume. As a result, a complete condensing of the working medium is ensured on exit from the condenser, without an additional, external regulating mechanism being necessary for this. Through an arrangement of the pump immediately downstream of the equalization container, it can therefore be guaranteed that the working medium of the waste heat utilization circuit always enters into the pump in liquid form. This leads to no undesired cavitation being able to occur within the pump. 
     A container according to the invention for a waste heat utilization circuit comprises a housing which delimits a housing interior, and namely such that the housing interior can be flowed through by a working medium. For this, a fluid inlet and a fluid outlet can be provided at a suitable position on the housing. In the housing interior a sheath is arranged, in which an auxiliary medium is accommodated. Here, the sheath is fluid-tight and is designed at least in certain areas in a heat-conductive manner. The sheath delimits a sheath interior of variable volume. Any materials which permit heat transport between the two hosing interiors, necessary for the temperature equalization, within a few minutes, preferably within a few seconds, are understood here as being “heat-conductive”. 
     In a preferred embodiment, the housing interior is at least partly filled by the working medium and/or is flowed through by the latter. Accordingly, the sheath is filled with an auxiliary medium, in a manner fluidically separated from the working medium, which auxiliary medium is present in the sheath interior in a gaseous and/or liquid state. In other words, the auxiliary medium can have in the sheath—depending on the current operating state of the container in the waste heat utilization circuit—a gaseous phase of a liquid phase, or both phases. Here, the boiling temperature of the auxiliary medium is preferably less by at least 10K, most preferably by at least 14K, than a boiling temperature of the working medium. The provision of an auxiliary medium with reduced boiling temperature compared to the working medium enables in a simple manner the supercooling of the working medium which is aimed for in operation in the waste heat utilization circuit. 
     To realize the volume-variability of the sheath interior, which is essential to the invention, it is proposed to provide the sheath with a membrane which is deformable in a fluid-tight and resilient manner. For this, preferably an elastomer, particularly preferably of a plastic, comes into consideration. 
     Particularly preferably, the sheath can be arranged so as to be freely movable in the, typically liquid, working medium present in the outer housing. This enables a particularly quick enlargement or respectively reduction of the volume of the sheath in the course of the heat transport between working medium and auxiliary medium. 
     According to a further preferred embodiment, the sheath is configured as a (first) bellows. Such a bellows permits a targeted expansion of the sheath along a predetermined direction, along which the material of the bellows, formed in a bellow-like manner, extends. This leads to a reduced installation space requirement for the container. 
     In an advantageous further development of the invention, a separating device is arranged in the housing interior, which divides the housing interior into a first partial space able to be flowed through by the working medium, and a second partial space which is fluidically separated from the first partial space. When the second partial space is fluidically connected to the external environment of the container by means of a pressure equalization opening provided in the housing, the effective volume of the container can be reduced for flowing through by the working medium on cold shutdown of the waste heat utilization circuit. Therefore, a sufficient fluid volume is always available for the flooding of the components of the waste heat utilization circuit, which can be filled with vapour in operation. On cold shutdown or on lowering of the condensation pressure below the ambient pressure, a portion of the working fluid present in the container can therefore be used for said flooding. By means of the second partial space, separated from the first partial space, an underpressure can be achieved here in the equalization container through pressure equalization. As a result, in this way, on cold shutdown an undesired contamination of the working medium with air, owing to leakage into the seals present in the waste heat utilization circuit, is prevented. 
     The separating device can be realized technically in a particularly simple manner by it being equipped with a separating element made of a fluid-tight and resiliently deformable material for varying the volume ratio of the two partial spaces with respect to one another. 
     In an alternative variant thereto, the separating device is configured as a (second) bellows or as part of such a (second) bellows. The simultaneous use of a first and a second bellows requires particularly little installation space. 
     A further preferred embodiment is to be produced with a particularly small number of components and consequently with particularly low manufacturing costs, in which the separating device, formed as second bellows, and a resilient membrane arranged in the second partial space are [part] of the sheath. 
     According to an advantageous further development, the second bellows is completed to the sheath by means of a resilient membrane. In this way, a particularly great variability of the volume of the sheath can be realized. 
     A further advantageous further development requires particularly little installation space, according to which the separating device comprises a separating element made of a fluid-tight and resiliently deformable material for varying the volume ratio of the two partial spaces relative to one another. Said separating element is fastened to the housing together with a further resilient and heat-conductive membrane, and divides the housing interior into three partial spaces. In this scenario, the separating element and the membrane are part of the sheath, and namely such that the third partial space is the sheath interior delimited by the sheath. 
     Another advantageous further development of the invention is particularly simple to produce, according to which the two membranes are fastened internally to a shared housing wall of the housing. In this variant, the fastening preferably takes place such that the shared housing wall forms both a part of the housing and also of the sheath. 
     In another preferred embodiment, the sheath is delimited by the first bellows. The separating device has a separating element of a resilient and fluid-tight material, wherein the first bellows is arranged in the first partial space. 
     Particularly expediently, the working medium can be ethanol and the auxiliary medium can be methanol. As their boiling temperature differs by approximately 14K, these two media are particularly suitable for ensuring the desired supercooling of the working medium. 
     In another preferred embodiment, the housing has a fluid inlet for introducing the working medium into the first partial space, and a fluid outlet present at the housing for directing the working medium out from the first partial space. Preferably here at least the fluid outlet is arranged in a lower region of the housing, particularly preferably in a housing base of the housing. The term “lower region” refers here to the position of use of the container in the waste heat utilization circuit. These provisions, in isolation or in combination, are intended to ensure that the working medium is only present in liquid phase when it is removed from the container via the fluid outlet. 
     Further important features and advantages of the invention will emerge from the subclaims, from the drawings and from the associated figure description with the aid of the drawings. 
     It shall be understood that the features mentioned above and to be explained further below are able to be used not only in the respectively indicated combination, but also in other combinations or in isolation, without departing from the scope of the present invention. 
     Preferred example embodiments of the invention are illustrated in the drawings and are explained further in the following description, wherein the same reference numbers refer to identical or similar or functionally identical components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       There are shown, respectively diagrammatically: 
         FIGS. 1 to 7  illustrate various examples for a container according to the invention, 
         FIG. 8  in diagrammatic representation the structure of a waste heat utilization circuit of a waste heat utilization device, into which the container according to the invention is integrated. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a first example of a container  1  according to the invention, as it can be operated in a waste heat utilization circuit  50  of a waste heat utilization device of a motor vehicle. The container  1  has a mechanically rigid housing  2 , which delimits a housing interior  3  with a predetermined volume. The housing interior  3  is flowed through by a working medium  6 . The latter can be introduced into the housing interior  3  via a fluid inlet  12  provided on the housing  2 , and can be directed out from the housing interior  3  again via a fluid outlet  13 , likewise provided on the housing  2 . 
     A separating device  8  is arranged in the housing interior  3 . The separating device  8  divides the housing interior  3  into a first partial space  10   a , which is able to be filled with the working medium  6 , and a second partial space  10   b , which is fluidically separated from the first partial space  10   a . The fluid inlet  12  and the fluid outlet  13  are fluidically connected here to the first partial space  10   a . The separating device  8  comprises a separating element  9  made of a fluid-tight and resilient material for varying the volume ratio of the two partial spaces  10   a ,  10   b  with respect to one another. The separating element  9  can be realized as a membrane and can comprise, for example, an elastomer. The separating element  9  can be fastened directly, therefore without further fastening means, by means of an adhesive connection on the inner side to the housing  2 . Instead of a direct fastening by means of an adhesive connection, alternatively also the use of another fastening method, for example a clamping- or screwed connection, is conceivable. In this case, it is necessary to equip the separating device  8  with suitable fastening elements, by means of which said clamping- or respectively screwed connection of the separating element  9  to the housing  2  can be realized. 
     As can be seen in  FIG. 1 , in the housing  2  of the container  1  an opening  15  is present for pressure equalization, which opening connects the second partial space  10   b  fluidically to the external environment  14  of the container  1 , so that the fluid pressure in the second partial space  10   b  always corresponds to the fluid pressure in the external environment  14 . In addition, a filling- and venting opening  16  is provided in the housing  2 , with a filling- and venting connecting piece  17  protruding outwards from the housing  2  away from the housing interior  3 . The filling- and venting opening  16  connects the first partial space  10   a  of the housing interior  3  fluidically to the external environment  14  of the container  1 . The filling- and venting connecting piece  17  can be closed by means of a suitably constructed sealing cap  18 . In the first partial space  10   a  of the housing interior  3  in addition a sheath  4  is arranged, which is fluid-tight and designed at least in certain areas in a heat-conductive manner. The sheath  4  delimits a sheath interior  5  of variable volume, in which an auxiliary medium  7  is arranged. The sheath  4  can be configured as a fluid-tight and resilient membrane  11 , as indicated diagrammatically in  FIG. 1 . For this purpose, the membrane  11  has a resilient material, which comprises a heat-conductive material for the temperature equalization between the working medium  6  and the auxiliary medium  7 . An elastomer also comes into consideration in an analogous manner to the separating element. 
     As  FIG. 1  shows, the auxiliary medium  7  is present in the sheath interior  5  both in a gaseous phase  7   a  and also in a liquid phase  7   b . The boiling temperature of the auxiliary medium  7  has a value lower by 10K, preferably by at least 14K, than the boiling temperature of the working medium  6 . The working medium is therefore preferably ethanol, the auxiliary medium ethanol. 
     In the state shown in  FIG. 1 , the working medium  6  and the auxiliary medium  7  have an approximately identical temperature. This state can be brought about through heat transport through the heat-transferring membrane  11  from the originally hotter working medium  6  to the originally cooler auxiliary medium. Through said heat absorption through the auxiliary medium  7 , the latter forms the partially liquid phase  7   b  shown in  FIG. 1 . This, in turn, is accompanied by an increase in the fluid pressure of the working medium  6 , until an equilibrium between liquid phase  7   a  and gaseous phase  7   b  occurs in the sheath interior  5  delimited by the membrane  11 . The fluid pressure of the working medium  6  in the housing interior  3  corresponds then to the boiling temperature of the auxiliary medium  7  in the sheath interior  5 . In this way, it is ensured that in the working medium  6 —in particular without active assistance from the exterior—the desired supercooling level always occurs for the operation in a waste heat utilization circuit  50 : When a working medium  6  with reduced temperature arrives into the housing interior  3  out from a condenser of the waste heat utilization circuit, upstream of the container  1 , then through heat transmission the temperature of the auxiliary medium  7  also decreases within a short time, and a portion of the gaseous phase  7   a  contained therein condenses out to the liquid phase  7   b . Accompanying this, the fluid pressure of the auxiliary medium  7  reduces, and therefore also that of the working medium  6 . This takes place until the supercooling of the working medium  6  has reached the desired extent again. When, on the other hand, the working medium  6  arrives with a high temperature and therefore in gaseous form, therefore in the form of vapour, out from the condenser into the housing interior  3 , then the fluid pressure of working medium  6  and auxiliary medium  7  increases, so that the complete condensing is brought about automatically at the condenser outlet, therefore without the assistance of an external regulation. 
       FIG. 1  shows the container  1  in the desired state of supercooling of the working medium. By comparison,  FIG. 2  shows the container of  FIG. 1  in the so-called cold shutdown of the waste heat utilization device  50  using the container  1 . In order to prevent a contamination of the working fluid  6  with air owing to leakages in seals on the cold shutdown of the waste heat utilization device  50 , the occurrence of an underpressure in the housing interior  3  must be prevented as far as possible. This occurs by means of the second partial space  10   b , which is fluidically connected to the external environment  14  of the container  1 , so that the volume of the first partial space  10   a  in the course of any drop in pressure which occurs in the first partial space  10   a  can be immediately reduced. In this way, the components of the waste heat utilization circuit  51  of the waste heat utilization device  50  which are filled with the working medium  6  in gaseous phase in operation, can be flooded with the working medium  6  in liquid phase. 
     Therefore, when the fluid pressure in the first partial space  10   a  falls below a minimum permissible swelling pressure, then the first partial volume  10   a  contracts by means of the flexible separating device  8 , so that the underpressure which has occurred can reduce again. In order to prevent said underpressure in the container  1 , the second partial space  10   b  is in contact with the external environment  14  via the opening  15 , so that a pressure equalization is possible. As a comparison of  FIG. 2  with the illustration of  FIG. 1  shows, by movement of the separating element  9  away from the housing wall of the housing  2 , the volume of the second partial space  10   b  is increased compared to the state of  FIG. 1 , and that of the first partial space  10   a  is reduced. It can be seen, furthermore, from  FIG. 2  that owing to the pressure reduction of the fluid pressure in the first partial space  10   a , the volume of the sheath interior  5  delimited by the sheath  4  also decreases, so that the gas phase  7   a  of the auxiliary medium  7 , still present in the state of  FIG. 1 , condenses out completely. 
       FIG. 3  shows a variant of the container  1  of  FIGS. 1 and 2 . In the example of  FIG. 3  the sheath  4  is configured in the manner of a (first) bellows  19 . Furthermore, in the container of  FIG. 3  the separating device  8  for the formation of two partial spaces  10   a ,  10   b  is dispensed with, so that also no opening  15  for pressure equalization is provided on the housing  2 . As  FIG. 3  clearly shows, the bellows  19  has a first bellows end wall  20   a  and a second bellows end wall  20   b  lying opposite the first bellows end wall  20   a . The two bellows end walls  20   a ,  20   b  delimit on the face side the bellows  19  which is configured substantially in the manner of a cylinder. The two bellows end walls  20   a ,  20   b  are connected by means of the resilient and heat-conductive membrane  11  already known from  FIG. 1 . The membrane  11  forms a circumferential wall  21  of the substantially cylindrical bellows  19 . Said circumferential wall  21  can be fastened by means of a fluid-tight adhesive connection to the two bellows end walls  20   a ,  20   b . Alternatively thereto, other suitable fastening methods come in consideration, in particular a screwed or clamping connection. 
     The container  1  according to  FIG. 4  is a further development of the example of  FIG. 3 . In the container of  FIG. 4 , in addition to the sheath  4  configured as a first bellows  19 , the separating device  8  is also configured as a second bellows  22 . The volume delimited by the second bellows  22  forms the first partial space  10   a , the region of the housing interior  3  complementary thereto forms the second partial space  10   b . In the example of  FIG. 4 , the first bellows  19  is arranged in the second partial space  10   b.    
     In accordance with  FIG. 4 , the second bellows  21  also forms a first bellows end wall  23   a , and a second bellows end wall  23   b  lying opposite thereto. The two bellows end walls  23   a ,  23   b  delimit on the face side the second bellows  22  configured substantially in the manner of a cylinder. The two bellows end walls  23   a ,  23   b  are connected to one another by means of the separating element  9  of the separating device  8 , therefore of the second bellows  22 , in the form of a fluid-tight membrane  24 . For this, the separating element  9  is configured as a resilient circumferential wall  25  delimiting the second bellows  22  on the circumferential side. The circumferential wall  25  can be fastened to the two end walls  23   a ,  23   b  by means of a fluid-tight adhesive connection. Alternatively thereto, the fastening methods for the first bellows  19 , named in connection with the example of  FIG. 3 , also come into consideration, therefore in particular a screwed or clamping connection. 
     In the example of  FIG. 4 , in an analogous manner to the container of  FIGS. 1 and 2 , a fluid inlet  12  and a fluid outlet  13  are provided on the housing  2 , which are both in fluid connection with the volume delimited by the second bellows  22 , therefore the first partial space  10   a . As can be seen from  FIG. 4 , the end walls  20   a  and  23   b  of the two bellows  19 ,  22  can lie opposite one another. The end wall  23   a , as shown in  FIG. 4 , can be formed by a housing wall  26  of the housing  2 , or the end wall  23   a  can be fastened, for instance by means of an adhesive connection, flat against this housing wall  26 . 
     Furthermore, on the housing  2  of  FIG. 4 , in an analogous manner to the container of  FIGS. 1 and 2 , a filling- and venting opening  16  is provided, having a filling- and venting connecting piece  17  protruding outwards from the housing  2 , away from the housing interior  3 . The filling- and venting opening  16  fluidically connects the first partial space  10   a  of the housing interior  3  to the external environment  14  of the container  1 . The filling- and venting connecting piece  17  can be closed in a sealing manner by means of a sealing cap  18 . The container  1  according to  FIG. 4  has an opening  15 , which fluidically connects the second partial space  10   b  to the external environment  14  of the container for the purpose of pressure equalization. A pressure relief valve  28  can be constructed on the filling- and venting connecting piece  17 . 
       FIG. 5  shows a further technical realization possibility for the container  1 . In this variant, the separating device  8 , configured as a (second) bellows  22 , is part of the sheath  4 . A resilient membrane  29 , which is arranged in the second partial space  10   b , and a housing wall  26  of the housing  2  complete the part of the (second) bellows  22 , which is part of the sheath  4 , to the sheath  4 . 
     In a further variant, which is illustrated in  FIG. 6 , the separating device  8  comprises a separating element  9  made of a fluid-tight and resiliently deformable material for varying the volume ratio of the two partial spaces  10   a ,  10   b  relative to one another. The separating element  9  is fastened to the housing  2  together with a further resilient and heat-conductive membrane  11 , and divides the housing interior  3  into three partial spaces  10   a ,  10   b ,  10   c . The separating element  9  and the membrane  11  are part of the sheath  4 . The third partial space  10   c  forms the sheath interior  5  delimited by the sheath  4 . The fastening of separating element  9  and membrane  11  can take place such that the shared housing wall  26 , as illustrated in  FIG. 6 , forms both a part of the housing  2  and also of the sheath  4 . 
     In the variant according to  FIG. 7 , the membrane  11  is replaced by a first bellows  19 , which with regard to its structure corresponds substantially or exactly to the bellows  19  of  FIG. 3 . The sheath  4  is formed by the bellows  19 , as in the example of  FIG. 3 . The separating device  8  is configured in an analogous manner to  FIG. 6  and is realized as membrane  29  from a resilient and fluid-tight material. As  FIG. 7  shows, the first bellows  19  is arranged in the first partial space  10   a . The bellows end wall  20   a  of the bellows  19  can be formed by the housing wall  26  of the housing  2 . Alternatively, said bellows end wall  20   a  can, however, also be fastened internally on the housing wall  26 , for example by means of a flat adhesive connection. 
     In the example of  FIGS. 5 to 7 , the housing  2  is configured in a pot-like manner with a housing pot  27 , which is closed by the housing wall  26 , so that the housing wall  26  acts in the manner of a cover. 
       FIG. 8  shows diagrammatically the structure of a waste heat utilization device with a waste heat utilization circuit  51 , in which the previously presented container  1  is arranged, and in which the working medium  6  circulates. In the waste heat utilization circuit  51 , a conveying device  52  in the form of a conveyor pump for conveying the working medium  6  is arranged downstream of the container  1 . Downstream of the conveying device  52 , two evaporators  53  are arranged, in which the working medium  6  is evaporated. Downstream of the evaporators  53 , an expansion machine  54  is arranged. Downstream of the expansion machine  54 , a condenser  55  is provided, which is followed by the container  1 , so that the waste heat utilization circuit  51  forms a closed circuit. Between the condenser  55  and the container  1 , a filter device  56  can be optionally provided for filtering the working medium  6 .