Device and method for the conversion of quasi-isothermal state changes in thermal power or working machine processes

Abstract

The invention relates to a device (1, 20, 25) for implementing quasi-isothermal changes of state in heat engine or machine processes, comprising a cylinder (2) providing a working chamber (3), a piston (4) movable in the working chamber (3) for limiting a gas volume variable in the working chamber (3), wherein the cylinder (2) has at least one access opening (5, 6, 21) for introducing and / or discharging working gas into and / or from the working chamber (3), at least one heat transfer fluid injection opening (7) for injecting a heat transfer fluid (9) into the working chamber (3) and at least one heat transfer fluid outlet opening (8) for discharging the heat transfer fluid (9) from the working chamber (3), wherein the at least one heat transfer fluid outlet opening (8) and the access opening (6, 21) for discharging the working gas are separate openings.The invention further relates to a corresponding method for implementing quasi-isothermal changes of state in heat power processes or working machine processes.

Description

[0001] The present invention relates to a device and a method for implementing quasi-isothermal changes of state, i.e., quasi-isothermal compression or expansion, in heat engine or working machine processes.

[0002] Isothermal compression represents the theoretically most energy-efficient method for compressing gases for all types of compressors. However, such isothermal compression is far from being achieved in practice, as this change of state requires a rapid dissipation of as much heat as is input during compression. To save energy and avoid high compressed air temperatures, current practices include using multiple compressor stages with intercooling between stages at high pressure ratios, or relying on passive air cooling via cooling fins in smaller units. The required technical work for all known designs and cooling methods is 15% to 30% higher than it would be for isothermal compression.

[0003] Analogous to compression processes, the same principle applies to isothermal expansion, albeit with the opposite sign. Examples include the theoretically best cycle, the Carnot cycle, and the well-known Stirling cycle, both of which, as ideal comparison processes, involve two isotherms, but which have so far been implemented very inadequately in practice. To realize isothermal expansion, heat must be supplied during expansion, analogous to the process in a compressor; specifically, the same amount of heat must be supplied during the expansion process as the work the gas performs.

[0004] So far, it has only been very difficult to extract heat from a gas quickly and efficiently (compression) or to add heat to it (expansion), because thermal resistances must be overcome for heat transfer. Heat transfer through cylinder walls, and especially the heat transfer of gases at walls, or the limited thermal conductivity of the gases themselves, prevent rapid and sufficiently high heat removal or input.

[0005] From US 8,479,502 B2, a device for implementing quasi-isothermal state changes is known (see Fig. 1 The device comprises a cylinder providing a working chamber and a piston movable within the working chamber to limit the gas volume. A working gas can be introduced into and discharged from the working chamber via an access port. Furthermore, a heat transfer fluid injection port is provided for injecting a heat transfer fluid into the working chamber, and a heat transfer fluid outlet port is provided for discharging the heat transfer fluid. The access port and heat transfer fluid outlet port are separate openings.

[0006] Against this background, the present invention aims to provide a device and a method for implementing quasi-isothermal changes of state in cyclic processes such as heat engine or machine processes. The goal is to improve heat transfer to a working gas to be compressed or expanded in such a way that the working gas is essentially maintained at its initial temperature level during the cyclic process, i.e., to compress or expand the gas (quasi-)isothermally. The isothermal compression or expansion should be energy-efficient and achieve a high degree of efficiency. Furthermore, the device should have a compact design and the method should be as easy to implement as possible.

[0007] This problem is solved by a device having the features of claim 1 and by a method having the features of claim 9. Further, particularly advantageous embodiments of the invention are disclosed in the respective dependent claims.

[0008] It should be noted that the features listed individually in the claims can be combined with one another in any technically meaningful way and demonstrate further embodiments of the invention. The description further characterizes and specifies the invention, particularly in conjunction with the figures.

[0009] It should also be noted that the conjunction "and / or" used below, which stands between two features and links them together, is always to be interpreted in such a way that in a first embodiment of the object according to the invention only the first feature may be present, in a second embodiment only the second feature may be present, and in a third embodiment both the first and the second feature may be present.

[0010] The term "approximately" used herein indicates a tolerance range that a person skilled in the art in this field would consider customary. In particular, the term "approximately" is to be understood as a tolerance range of the relative quantity of up to a maximum of + / -20%, preferably up to a maximum of + / -10%.

[0011] An inventive device for implementing quasi-isothermal changes of state in heat engine processes or machine processes, generally in a thermodynamic cycle, comprises a cylinder providing a working chamber, a piston (hereinafter also referred to as a working piston) movable within the working chamber for limiting a variable gas volume within the working chamber, at least one heat transfer fluid injection port for injecting a heat transfer fluid into the working chamber, and at least one heat transfer fluid outlet port for discharging the heat transfer fluid from the working chamber. The cylinder also has at least one access port for introducing and / or discharging working gas into and / or from the working chamber. It is possible to provide only one access port through which the working gas can be both introduced into and discharged from the working chamber.Separate access openings, at least one of which serves solely as an inlet opening for the working gas into the working space and at least one other access opening solely as an outlet opening for the working gas out of the working space, are also conceivable.

[0012] According to the invention, the at least one heat transfer fluid outlet opening and the at least one access opening for removing the working gas from the working chamber are separate openings. Furthermore, the piston is designed as a plunger.

[0013] A device that implements a heat power process can also be called a heat engine. A heat engine is a machine that converts heat into mechanical energy (work). It utilizes the tendency of heat to flow from areas of higher to those of lower temperatures.

[0014] A device that implements a combined heat and power process can be called a working machine, heat pump, or refrigeration machine. Such a device uses mechanical energy to transfer thermal energy from a lower temperature level to a higher one.

[0015] Heat engines utilize "clockwise" cycles, in which the closed curve, as seen in the Ts or pv diagram, is traversed in the direction "top to right, bottom to left". Heat pumps utilize "counterclockwise" cycles. Ideal cycles are used to assess the efficiency of these processes. The theoretical basis for these cycles is the thermal equation of state for ideal gases, which includes the three gas state variables: pressure, temperature, volume, and the universal gas constant.

[0016] When circular processes are generally referred to herein, both clockwise and counterclockwise circular processes are equally meant, unless expressly stated otherwise.

[0017] The device according to the invention achieves a significantly improved implementation of quasi-isothermal state changes in general, and in particular when used in cycles with isothermal state changes, in compressors, in expanders, and in the charging and discharging of compressed air storage tanks or storage tanks based on the same operating principle but with different gas types. Since compression and expansion have previously typically proceeded quasi-adiabatically or polytropically, possibly with intercooling, the efficiency of the cycles can be significantly increased by approaching the isotherm. In compressors, the input mechanical work is reduced, and in expanders, e.g., when discharging pressure storage tanks, the output work is increased.

[0018] The heat transfer medium absorbs heat from the working gas during compression and releases heat to the working gas during expansion.

[0019] Preferred heat transfer fluids within the meaning of the invention are, in particular, liquids that have a high heat capacity, are non-corrosive or only slightly corrosive, have poor solubility in gases and / or in which the gas dissolves poorly in the liquid heat transfer fluid, whose viscosity is suitable for injection within the meaning of the invention, and which are thermally stable up to a temperature of approximately 220 °C. Water, oils, especially low-viscosity oils, and ionic liquids with the desired properties are particularly preferred as heat transfer fluids. Furthermore, liquids with a vapor pressure that is low compared to the minimum pressure in the working space (i.e., compression or expansion space) can advantageously be selected.Furthermore, such heat transfer fluids have a large density difference compared to the working gas, which, due to the influence of gravity, naturally ensures easy separation from the working gas, so that the heat transfer fluid can be collected in a targeted manner at a predetermined point in the working space or cylinder (e.g. in a heat transfer fluid sump), especially near or at the heat transfer fluid outlet opening (e.g. at the bottom).

[0020] It is understood that, to achieve the described effect according to the invention, the heat transfer fluid is injected into the working chamber essentially simultaneously during a compression or expansion stroke of the piston via at least one heat transfer fluid injection port. The quantity and droplet size of the heat transfer fluid can be suitably pre-determined or controlled during operation. The pressure conditions in the working chamber and the material properties of the heat transfer fluid are selected such that the heat transfer fluid does not evaporate in the working chamber, as explained.

[0021] In particular, the heat transfer fluid, which is distributed in one or more spray jets—i.e., essentially in the form of individual, precisely directed spray cones or in a shower-like manner, where the heat transfer fluid is injected into the working chamber through a multitude of small openings directed downwards towards the piston, essentially as a solid jet and sprayed through the working chamber—is distributed throughout the entire gas volume. Due to the high heat capacity of the droplets compared to the lower heat capacity of the working gas, and due to the large transfer surface area of ​​the droplets, the temperature of the working gas is maintained at or near the temperature level of the heat transfer fluid. It should be understood that the term Temperaturniveau This includes a certain temperature difference between the working gas and the heat transfer medium, since such a difference - even if only a very small one - is always physically / technically present.

[0022] The heat transfer fluid injection port can be nozzle-shaped to inject the heat transfer fluid into the working chamber in the form of a suitable spray cone. Advantageously, such a nozzle-shaped port can be recessed into a cylinder wall, e.g., in a cylinder head, to minimize dead space in the cylinder (for example, in the area of ​​the cylinder head).

[0023] After compression or expansion, the working gas is expelled from the working chamber through at least one access port (e.g., Stirling engine). Once the heat transfer medium has transferred heat to the working gas, heat is added to or removed from the heat transfer medium via a heat exchanger. This heat transfer takes place outside the cylinder.

[0024] A particular advantage of injecting the liquid heat transfer fluid lies in the efficient heat transfer from the droplets to the working gas being compressed / expanded. This means that the working gas can be kept cold (compressor) or, conversely, heated (expansion, e.g., Stirling engine) by injecting a cold heat transfer fluid in a very short time (e.g., approximately 0.2 s or faster). When the device according to the invention is combined with a Stirling engine, practical, and in particular significantly higher, rotational speeds can now be achieved.

[0025] According to the invention, the heat transfer fluid outlet opening is clearly separated from at least the access opening for discharging the working gas. Likewise, the heat transfer fluid outlet opening can be provided separately from both the access opening for discharging and the access opening for introducing the working gas, wherein the access opening can be a single opening for introducing and discharging the working gas or several dedicated access openings can be provided.

[0026] According to the invention, the heat transfer fluid outlet opening is provided separately from at least the access opening for discharging the working gas from the working chamber. The separation of the working gas from the heat transfer fluid preferably takes place essentially within the cylinder / working chamber. Since, according to the invention, the working gas and the heat transfer fluid do not exit the cylinder through the same opening, a heat transfer fluid separation system outside the cylinder, which is otherwise conventional, can be omitted or made significantly smaller to separate the residual liquid, should an external heat transfer fluid separation system be required. This results in a simplified, compact design and reduces manufacturing costs.

[0027] Furthermore, the heat transfer fluid outlet opening can also be located at a specified minimum distance from the access opening for dispensing and, if necessary, introducing the working gas into the working chamber; that is, it cannot be located in the (immediate) vicinity of / adjacent to the access opening. The possible spacing of the respective outlet openings also ensures the most complete possible separation of the heat transfer fluid from the working gas.

[0028] According to an advantageous embodiment of the invention, the at least one heat transfer fluid outlet opening, relative to the cylinder's operating position in the direction of gravity (i.e., in the direction of gravitational acceleration or gravity), is arranged below the at least one heat transfer fluid injection opening. Due to gravity, the injected heat transfer fluid, i.e., the liquid droplets, collects in the area of ​​the heat transfer fluid outlet opening, allowing the heat transfer fluid to be extracted or pumped out of the working chamber in a controlled manner, cooled or heated outside the working chamber, and then made available for re-injection. This ensures an efficient heat transfer fluid cycle.Furthermore, the heat transfer fluid injection port located above the heat transfer fluid outlet allows for targeted injection of the heat transfer fluid into the entire working space in order to efficiently transfer heat to the working gas within the entire gas volume, thus ensuring that the working gas remains as constant as possible at its initial temperature level.

[0029] A further advantageous embodiment of the invention provides that the at least one heat transfer fluid injection port is arranged in an upper end section of the working chamber, relative to the cylinder's operating position in the direction of gravity (i.e., in the direction of gravitational acceleration or gravity). The cylinder may have a cylinder head that delimits this end section of the working chamber. The upper end section of the working chamber may be arranged near or adjacent to a cylinder head. The heat transfer fluid injection port may be located in the cylinder head. In other words, the heat transfer fluid is injected into the working chamber from above, strikes the piston and / or a cylinder wall, and is then directed towards the heat transfer fluid outlet port by gravity.This arrangement of the heat transfer fluid injection port makes it possible to minimize dead space in the cylinder by arranging the heat transfer fluid injection port above the top dead center of the piston in the cylinder, thus ensuring continuous, efficient heat transfer from the heat transfer fluid to the working gas for optimal isothermal compression or expansion.

[0030] According to a further preferred embodiment of the invention, the piston head surface is inclined with respect to a longitudinal axis of the piston and is conical or domed, preferably domed in a convex shape. The piston head surface is the piston surface that limits the gas volume in the working chamber on the piston side. A domed surface can, for example, be understood as a flattened hemispherical shape.

[0031] Given an outer diameter of the piston head surface and a given radius of curvature of the piston head surface in the center of the piston, the knocker shape has a particularly strongly curved edge, the radius of curvature of which can only be about 10% of the outer diameter.

[0032] The angled, conical, or domed piston shape effectively prevents unwanted accumulation of the heat transfer fluid on the piston crown and, upon impact, promotes deflection towards the heat transfer fluid outlet or a liquid sump optionally located upstream of the outlet. The angled shape of the piston crown also allows for optimal injection lengths of the heat transfer fluid, even near top dead center, ensuring effective heat transfer from the heat transfer fluid to the working gas in this position as well. The heat transfer fluid can be injected into the combustion chamber essentially parallel to the angled piston crown surface.

[0033] It goes without saying that the cylinder or cylinder head is adapted to the respective piston shape (i.e., slanted, conical, domed, and the like) in order to keep the dead volume as small as possible.

[0034] According to the invention, the piston is designed as a plunger cylinder. Plunger cylinders, also known as reciprocating pistons or displacement pistons, do not have an actual piston; instead, the piston rod itself serves as the piston. The plunger slides within a seal and sliding guide that are fixed to the cylinder. While plungers require axial guidance, they offer a more favorable mechanical efficiency. A discontinuous piston control can also be implemented using a hydraulic drive with the plunger cylinder.

[0035] As an alternative to the hydraulic drive of a plunger cylinder, another piston can have a mechanical drive with connecting rod and crank mechanism.

[0036] The seal fixed to the cylinder (instead of a piston seal that moves along the cylinder wall with the piston in a conventional piston) has the advantage, among others, that the device is sealed to the outside in every plunger position, and furthermore, that a fluid-conducting connection between the heat transfer fluid injection port and the heat transfer fluid outlet port is maintained at all times. This ensures continuous, efficient heat transfer between the heat transfer fluid and the working gas to achieve optimal isothermal compression or expansion. In addition, the simultaneous and continuous injection and extraction of the heat transfer fluid allows for precise adjustment of the amount of heat transfer fluid in the cylinder or working chamber, thus reducing dead volumes compared to conventional piston engines.Furthermore, harmful pressure peaks in the working chamber during the expulsion of the heat transfer fluid-working gas mixture can be reliably avoided by the permanent fluid-conducting connection between the heat transfer fluid injection opening and the heat transfer fluid outlet opening.

[0037] Furthermore, the surface temperature of the cylinder's inner wall can be reduced due to improved heat transfer and exchange through constant contact with the flowing heat transfer fluid. Additionally, the absence of a piston seal eliminates frictional heat on the cylinder's inner wall. Consequently, the use of a plunger results in lower demands and reduced thermal and mechanical stress on the cylinder's inner wall, as the plunger is not in frictional contact with it.

[0038] Furthermore, an optimal distance (i.e., annular gap) between the plunger and the cylinder inner wall can be freely selected to increase the efficiency of the device or to adapt the geometry of the annular gap to the viscosity of the heat transfer fluid. For example, the plunger and the cylinder inner wall do not necessarily have to be concentrically aligned. The plunger shape can also allow for the free design of a sump for collecting the heat transfer fluid upstream of the heat transfer fluid outlet opening, with respect to both volume and geometry. For example, the sump can have a larger diameter or a different geometry than the rest of the cylinder wall. In this way, the dead space can be positively influenced, for example, by adjusting the sump height or the fill level of the heat transfer fluid in the sump, thus minimizing it.

[0039] The use of the plunger also makes it possible to use ordinary check valves in the access openings for the introduction and exhaust of the working gas.

[0040] According to another advantageous embodiment of the invention, an annular gap is provided upstream of the heat transfer fluid outlet opening between the piston and an inner cylinder wall for collecting the heat transfer fluid before it is discharged from the cylinder. As explained herein, a natural, gravity-assisted separation of the injected heat transfer fluid from the working gas already takes place within the working chamber. In the present embodiment, the sprayed liquid droplets flow downwards in the annular gap, for example by flowing laminarly along the walls of the annular gap, and collect in front of the heat transfer fluid outlet opening to form a liquid sump, which can be pumped / suctioned out of the working chamber in a controlled manner.The annular gap is preferably dimensioned so that, on the one hand, a sufficient quantity of heat transfer fluid can flow through it and reach the heat transfer fluid outlet, while on the other hand, the dead volume formed by the annular gap remains as small as possible. Particularly preferably, such an annular gap can have a ring diameter (i.e., radial diameter) of approximately 0.1 mm to approximately 2 mm, more preferably between 0.15 mm and 1.5 mm, and further preferably between approximately 0.2 mm and 1.5 mm. Smaller ring diameters from the specified ranges can be selected when using less viscous heat transfer fluids, and larger ring diameters within the specified ranges can be selected when using more viscous heat transfer fluids. The height of the annular gap can be dimensioned such that a reservoir of the fluid sump can form, which can temporarily absorb at least a portion of the heat transfer fluid injected per unit of time.The total volume of the annular gap is preferably always kept to a minimum. The annular gap enables both a compact device design and a continuous, uninterrupted exchange of heat transfer fluid into and out of the working chamber.

[0041] Advantageously, in a further embodiment, a demister is arranged in the annular gap to separate even the smallest amounts of the heat transfer fluid from the working gas, which may remain in the working gas after the gravity-assisted separation of the majority of the heat transfer fluid. A trickle section can be implemented within the annular gap using the demister. It can be advantageous to reduce the flow rate of the heat transfer fluid by trickling it in the annular gap, since, due to pressure fluctuations in the working chamber, some gas absorption into the heat transfer fluid cannot be completely ruled out. To separate heat transfer fluid droplets at the gas outlet openings of the cylinder, an insert in the form of an orifice, a metal grid, or similar can be installed inside the cylinder / cylinder head.

[0042] The demister can be designed, for example, using a porous material or as a wire mesh filter, possibly in combination with one or more externally attached or woven-in metal grids.

[0043] In addition to the annular gap, a sump for collecting the incoming heat transfer fluid can be provided at the lower end of the annular gap, relative to the cylinder's operating position in the direction of gravity (i.e., in the direction of gravitational acceleration or gravity). The sump can differ from the annular gap by having a larger radial width (i.e., radial diameter). The sump provides a free space or basin in which the introduced heat transfer fluid can collect and settle, thereby separating gas bubbles, among other things. Furthermore, the level of the sump can be constantly controlled so that working gas can never escape from the cylinder through the at least one heat transfer fluid outlet. For this purpose, the heat transfer fluid outlet can, for example, be located and connected at the lower edge of the sump, meaning that the heat transfer fluid can be discharged directly from the sump through the heat transfer fluid outlet.

[0044] To further optimize the controlled heat transfer fluid exchange into and out of the working chamber, a further embodiment of the invention provides a double-acting pump piston configured to simultaneously inject the heat transfer fluid into the working chamber via at least one heat transfer fluid injection port and simultaneously discharge or extract it from the working chamber via at least one heat transfer fluid outlet port. In other words, when the heat transfer fluid is injected, the same quantity is simultaneously discharged or extracted from the working chamber, thereby maintaining a constant gas volume of the working gas in the cylinder / working chamber with respect to the heat transfer fluid exchange.This prevents unwanted compression of the working gas during injection of the heat transfer fluid and unwanted expansion of the working gas during discharge / removal of the heat transfer fluid, thereby increasing the energy efficiency of the cycle. The liquid volume of the heat transfer fluid in the cylinder remains constant, as the same amount of liquid is removed simultaneously with injection.

[0045] Accordingly, a collection tank and a high-pressure tank for the heat transfer fluid can be omitted. Only the piping or connecting lines for conveying the heat transfer fluid and the double-acting pump piston need to be filled, which significantly reduces the total amount of heat transfer fluid required in the device.

[0046] The work required to inject the heat transfer fluid can be reduced to an optimal value, and the heat transfer fluid can be efficiently brought to an injection pressure at which the thermal resistance of the heat transfer fluid to the working gas during the injection process is minimized. The heat transfer fluid is not unnecessarily depressurized, e.g., to ambient pressure and later compressed again to a high injection pressure; instead, only the differential pressure between the heat transfer fluid outlet and the injection pressure is applied, which represents the most energy-efficient injection method.

[0047] The simultaneous exchange of heat transfer fluid in the cylinder ensures a constant level of heat transfer fluid, for example in a heat transfer fluid sump and / or in an annular gap.

[0048] In addition to the double-acting pump piston, two check valves can be connected to it for direction-dependent flow of the heat transfer fluid. This prevents unintentional backflow of heat transfer fluid into the cylinder via the heat transfer fluid outlet during injection into the working chamber and simultaneous discharge / extraction from the working chamber. The two check valves reliably ensure this function. Furthermore, the check valve arrangement allows the piston to operate without load outside of the active injection phase.

[0049] Furthermore, the double-acting pump piston allows for the simultaneous transport of the heat transfer fluid into and out of the working chamber, enabling the simple control of a non-linear (e.g., non-sinusoidal) injection / extraction rate of the heat transfer fluid over a complete cycle of the implemented thermodynamic process, thus further increasing the energy efficiency of the cycle. For this purpose, the pump piston can be controlled with a non-linear or non-sinusoidal piston displacement. For example, less heat transfer fluid can be injected into the working chamber at the beginning of a compression stroke of the working piston than towards the end, before the piston reaches its top dead center (the opposite applies during expansion).

[0050] The control of the double-acting pump piston can be achieved in such a way that a constant pressure differential exists between the working pressure in the cylinder or working chamber and the injection pressure of the heat transfer fluid throughout the entire operating cycle. This ensures uniform spray formation of the heat transfer fluid in the working chamber and minimizes the injection effort. In contrast, this pressure differential varies considerably in conventional injection systems with a constant heat transfer fluid pressure, resulting in uneven and unfavorable spray formation.

[0051] As an alternative to the double-acting pump piston, the heat transfer fluid can be transported using one or more conventional pump(s).

[0052] Furthermore, the piston (i.e., working piston) can be designed to be hollow inside the piston.

[0053] If, after a completed cycle of the implemented process, the working gas still contains an excessively high proportion of liquid heat transfer fluid for the intended application, an additional component, such as a separator or similar device, can be provided to separate the excess liquid heat transfer fluid from the working gas. The separated heat transfer fluid can then be returned to the heat transfer fluid circuit, if desired, or alternatively, removed from the circuit.

[0054] According to a further aspect of the invention, in a method for implementing quasi-isothermal state changes in heat engine processes or machine processes, in which a working chamber is provided within a cylinder and a variable gas volume in the working chamber is limited by a piston movable within the working chamber (hereinafter also referred to as a working piston), a working gas is introduced into and / or discharged from the working chamber via at least one access opening in the cylinder. A heat transfer medium is injected into the working chamber via at least one heat transfer medium injection opening, and the heat transfer medium is discharged from the working chamber via at least one heat transfer medium outlet opening at a different location than the working gas, i.e., separately from the working gas. The piston is designed as a plunger.

[0055] It should be noted that, with regard to process-related definitions as well as the effects and advantages of process features, reference can be made in full to the explanations of analogous definitions, effects and advantages of the device according to the invention, and vice versa. Therefore, a repetition of explanations of analogous features, their effects and advantages with regard to the device and method disclosed herein can be largely omitted in favor of a more concise description.

[0056] Dispensing the heat transfer fluid via at least one heat transfer fluid outlet opening, separate from the working gas, takes advantage of the natural separation of the heat transfer fluid from the working gas that already occurs within the working chamber, e.g., due to a density difference between the heat transfer fluid and the working gas, as well as the influence of gravity. The otherwise conventional heat transfer fluid separation outside the cylinder can be dispensed with by dispensing the two media separately, which significantly simplifies the implementation of the process according to the invention and successfully reduces implementation costs.

[0057] An advantageous embodiment of the method according to the invention provides that the heat transfer medium, relative to an operational position of the cylinder in the direction of gravity (i.e. in the direction of the acceleration due to gravity), is injected into the working chamber in an upper end section of the working chamber and discharged below the at least one heat injection opening, which further improves a natural, gravity-assisted separation of the heat transfer medium from the working gas within the working chamber between the heat transfer medium injection opening and the heat transfer medium outlet opening.

[0058] In a further embodiment of the invention, the injected heat transfer fluid is directed towards the heat transfer fluid outlet opening via a correspondingly shaped piston head surface. For this purpose, the piston head surface can, for example, be inclined with respect to a longitudinal axis of the piston, or be conical or domed. A domed piston head surface can particularly preferably be shaped like a dished end.

[0059] In another advantageous embodiment of the process, the heat transfer fluid is collected upstream of the heat transfer fluid outlet opening in an annular gap between the piston and an inner cylinder wall before being discharged from the working chamber. After passing through the gas volume in the working chamber, the heat transfer fluid flows downwards in the annular gap and can collect in a liquid sump in front of the heat transfer fluid outlet opening.

[0060] According to a further embodiment of the invention, the ring diameter (i.e., radial diameter) of the annular gap is selected in a range of 0.1 mm to 2 mm, preferably between 0.15 mm and 1.5 mm, and even more preferably between 0.2 mm and 1.5 mm. Smaller ring diameters from the specified ranges can be selected when using less viscous heat transfer fluids, and larger ring diameters within the specified ranges can be selected when using more viscous heat transfer fluids. In this way, the heat transfer fluid can, for example, flow laminarly along the walls of the annular gap to achieve an efficient, gravity-assisted separation of the heat transfer fluid from the working gas within the cylinder.The height of the annular gap is preferably chosen so that, on the one hand, a sufficient reservoir of the liquid sump can form, which can temporarily absorb at least part of the heat transfer fluid injected per unit of time, and on the other hand, the total volume of the annular gap is reduced to a minimum.

[0061] Alternatively or additionally, the rate of descent of the heat transfer fluid can be reduced by trickling it into the annular gap. For example, a demister can be used for this purpose. Along the trickling section, further working gas can separate from the heat transfer fluid.

[0062] Alternatively or additionally, heat transfer droplets can be deposited on an aperture, a metal grid or similar within the cylinder, e.g. at the gas outlet openings of the cylinder and / or in the annular gap.

[0063] Degassing the heat transfer fluid in the annular gap, e.g. with the help of the demister, additionally prevents the heat transfer fluid from being moved along with the rising and falling piston in the annular gap and from coming to rest, which, among other things, makes reliable discharge (e.g. suction) of the heat transfer fluid more difficult.

[0064] According to another embodiment, it is further advantageous that the heat transfer fluid is collected in a sump at the lower end of the annular gap, relative to the cylinder's operating position in the direction of gravity, before being discharged. In this free sump, where the incoming heat transfer fluid can collect and settle, further gas bubbles can be effectively separated. Furthermore, the fill level of the heat transfer fluid sump can be controlled such that working gas can never flow from the cylinder through the heat transfer fluid outlet. In other words, the fill level of the heat transfer fluid sump can always cover the outlet, thus reliably sealing it against the working gas.

[0065] Furthermore, according to a preferred embodiment of the invention, the heat transfer fluid is injected into the working chamber via at least one heat transfer fluid injection port and simultaneously discharged or extracted from the working chamber via at least one heat transfer fluid outlet port using a double-acting pump piston. In other words, the same quantity of heat transfer fluid is simultaneously discharged or extracted from the working chamber during injection, thereby maintaining a constant gas volume of the working gas in the cylinder / working chamber with respect to the heat transfer fluid exchange.

[0066] In a further advantageous embodiment, the injection and / or extraction of a quantity of the heat transfer fluid during the isothermal change of state, i.e., within a cycle, in the heat engine process or the machine process, occurs non-linearly (e.g., non-sinusoidally). From a thermodynamic perspective, during isothermal expansion and isothermal compression, the work required for compression increases with increasing pressure in the working chamber. This means that, on the path from the bottom dead center to the top dead center of the piston, increasingly more compression work must be expended for the same distance, and therefore more heat must be dissipated. During a cycle of the thermodynamic process, the heat transfer fluid is not injected at a constant pressure or with a constant volume flow rate, but rather at a lower pressure at the beginning and a higher pressure towards the end; in other words, less heat transfer fluid is injected into the working chamber at the beginning and more at the end. The opposite is true for expansion.Here, the most heat is supplied to the working gas at the beginning, and less heat towards the end, resulting in a smaller amount of heat transfer fluid and / or a lower injection pressure. This minimizes the work required for injecting the heat transfer fluid and increases the efficiency of the cycle.

[0067] Furthermore, the working piston, designed as a plunger cylinder, can be controlled discontinuously with a hydraulic drive.

[0068] Further features and advantages of the invention will become apparent from the following description of a non-limiting embodiment of the invention, which is explained in more detail below with reference to the drawing. This drawing schematically shows: Fig. 1 a longitudinal sectional view of an embodiment of a device according to the invention, Fig. 2 a longitudinal sectional view of a further embodiment of a device according to the invention, Fig. 3 a longitudinal sectional view of yet another embodiment of a device according to the invention, Fig. 4 a flow diagram of an embodiment of a method according to the invention using the device made of Fig. 1 Fig. 5 shows a flow diagram of a further embodiment of a method according to the invention using the device made of Fig. 2 and Fig. 6 shows an exemplary pressure profile of a working gas in relation to a pressure profile of a heat transfer medium of an exemplary device according to the invention.

[0069] In the different figures, parts that are equivalent in function are always provided with the same reference symbols, so that they are usually only described once.

[0070] Fig. 1 Figure 1 schematically depicts a longitudinal sectional view of an embodiment of a device 1 for implementing quasi-isothermal state changes in heat engine processes or machine processes according to the invention. The device 1 comprises a cylinder 2, which provides a working chamber 3, and a piston 4, which is displaceable within the working chamber 3, in particular longitudinally displaceable (i.e., along its longitudinal axis 19), for limiting a gas volume that can be varied within the working chamber 3. The piston 4 (hereinafter also referred to as the working piston) can be hollow. The gas volume present in the working chamber 3 can be expanded or compressed by the piston 4.

[0071] As in Fig. 1 As can be further seen, the cylinder 2 of the present device 1 has two access openings 5 ​​and 6, one of which, 5, serves to introduce working gas into the working chamber 3 and the other, 6, to expel the working gas from the working chamber 3. Fig. 1 The access opening 5 is additionally, and without being strictly limited to this, equipped with a suction valve, and the access opening 6 with a pressure valve, such as those that may be provided, for example, in a compressor. The valves in the access openings 5 ​​and 6 may advantageously be designed as ordinary check valves, as shown in Fig. 1 is indicated. Furthermore, the in Fig. 1 The device 1 shown has at least one heat transfer fluid injection opening 7 (two are shown here) for injecting a heat transfer fluid 9 into the working chamber 3 and at least one heat transfer fluid outlet opening 8 for discharging the heat transfer fluid 9 from the working chamber 3. It is in Fig. 1 It is clearly evident that the heat transfer fluid outlet opening 8 and at least the access opening 6 for the discharge of the working gas from the working chamber 3 are separate openings.

[0072] In particular, in Fig. 1 It is clearly evident that in the exemplary device 1, the at least one heat transfer fluid outlet opening 8 is arranged below the at least one heat transfer fluid injection opening 7 with reference to an operational position of the cylinder 2 in the direction of gravity G (i.e. in the direction of the acceleration due to gravity).

[0073] Furthermore, it shows Fig. 1 that at least one heat transfer fluid injection port 7 is arranged in an upper end section of the working chamber 3 with respect to the operating position of the cylinder 2 in the direction of gravity G. In the present case, the heat transfer fluid injection port 7 is arranged in a cylinder head 10 of the cylinder 2, wherein the cylinder head 10 can be flat, domed, or strongly chamfered towards its outer edges. In the present example, the heat transfer fluid injection ports 7 are located as shown in Fig. 1 recognizable in an upper end section of cylinder 2.

[0074] The cylinder head 10 is adapted in its shape to a piston head surface 11. The head surface 11 of the piston 4 limits the gas volume in the working chamber 3 on the piston side. In the example shown here, the head surface 11 of the piston 4 is convex, preferably domed. Fig. 1 The head surface 11 is essentially represented as a flattened hemispherical shape which may have the dimensions (i.e. outer diameter and radii) of a dished head already mentioned in the general part of the description, but is not necessarily limited to this.

[0075] The exemplary device 1 in Fig. 1 It also provides an annular gap 12 upstream of the heat transfer fluid outlet opening 8 between the piston 4 and a cylinder inner wall of the cylinder 2 for collecting the heat transfer fluid 9 before it is discharged from the working space 3.

[0076] At the lower end, i.e., with respect to the operational position of the cylinder 2 in the direction of gravity G, of the annular gap 12, the Fig. 1 The device 1 shown additionally includes a sump chamber 13 for collecting the incoming heat transfer fluid 9. The sump chamber 13 is located in a lower end section of the cylinder 2 with respect to the direction of gravity G, which is diametrically opposite the upper end section.

[0077] In Fig. 1 It can be seen that the liquid heat transfer fluid 9 is injected / jetted into the working chamber 3 from above, whereby, depending on the dimensions of the cylinder 2 or the working chamber 3, a single spray cone or several (as shown here) can be used. The heat transfer fluid 9 is injected through the cylinder head 10 and directed by the piston 4, in particular its head surface 11, such that the liquid heat transfer fluid 9, after passing through the gas volume present in the working chamber 3, flows downwards in the annular gap 12 and collects at the bottom in the sump 13. After compression or expansion of the working gas, it can be expelled through the access opening 6.

[0078] The heat transfer fluid 9 has the function of absorbing heat from the working gas during compression and releasing heat to the working gas during expansion. The injected heat transfer fluid 9 impinges on the piston 4 or the cylinder wall and can flow from there through the annular gap 12 into the sump 13. The annular gap 12 is selected to be large enough to allow sufficient liquid heat transfer fluid 9 to enter the sump 13 while keeping the dead volume small. The sump 13 can provide a free space in which the introduced heat transfer fluid 9 can settle and collect, among other things to separate gas bubbles. One or more heat transfer fluid outlet openings 8 are located in the lower region of the cylinder 2. The fill level of the sump 13 is preferably selected such that it is ensured at all times that no working gas from the cylinder 2 or the working chamber 3 can flow into the outlet opening 8.

[0079] The liquid heat transfer fluid 9 is preferably selected with a high heat capacity, is non-corrosive or at least only slightly corrosive, has poor solubility in gases (i.e., the working gas dissolves poorly in the heat transfer fluid), and has a viscosity suitable for injection. Furthermore, the heat transfer fluid 9 is preferably thermally stable up to approximately 220 °C. Suitable heat transfer fluids include, among others, water, oils, and ionic liquids with the desired properties.

[0080] For injecting the heat transfer fluid 9, the at least one heat transfer fluid injection port 7 is preferably nozzle-shaped. The number, type, arrangement, and orientation of the injection nozzles are selected such that the thermal resistance of the liquid heat transfer fluid to the working gas in the working chamber 3 is minimized during the injection process, while simultaneously keeping the injection effort low. The nozzles are preferably recessed in the cylinder head 10 to minimize dead space.

[0081] How Fig. 1 As can be clearly seen, the harmful space (i.e. dead space) formed by the annular gap 12 of the device 1, which includes the annular space not filled with the heat transfer medium 9, is very small due to the relatively small dimensionable annular gap 12.

[0082] In contrast to previously known devices, which only achieve very slow individual strokes of, for example, only 4 s for a piston stroke from top to bottom dead center, the device 1 according to the invention achieves heat transfer from the injected heat transfer medium 9 to the working gas to be compressed / expanded so efficiently that the gas can be cooled (compressor) or, conversely, heated (expansion) by injecting cold heat transfer medium 9 in a very short time (e.g., about 0.2 s or faster).

[0083] It was recognized that this works better (i.e., the thermal resistance between the liquid heat transfer fluid and the working gas decreases) the higher the differential pressure (injection pressure minus chamber pressure in the working chamber). The device according to the invention, e.g., the one described in Fig. 1 The device 1 shown can be operated in an optimal operating state depending on the energy required for the injection of the heat transfer medium and the desired cooling or heating effect on the working gas, as well as the achievable shortening of the compression phase or expansion phase and thus the attainment of practical rotational speeds.

[0084] The piston 4 is a plunger cylinder (displacement piston) with, for example, a hydraulic drive 14 or a mechanical drive 15 with connecting rod and crankshaft (see below). Fig. 4 and 5 ) executed.

[0085] Fig. 1 It can further be seen that a suitable seal 16 and a sliding guide 17 can be provided at the bottom of the piston 4, which can be supplied and mounted as a single assembly within a seal package 18. In the illustrated embodiment, the seal 16 and the sliding guide 17 are fixedly attached to the lower section of the cylinder 2. The piston 4 is designed as a plunger that slides within the fixed seal 16 and sliding guide 17, i.e., the seal package 18. This has, among other advantages, that the device 1 is sealed to the outside in every plunger position, and furthermore, that a fluid-conducting connection is maintained at all times between the heat transfer fluid injection port 7 and the heat transfer fluid outlet port 8. This ensures continuous, efficient heat transfer between the heat transfer fluid 9 and the working gas to achieve optimal isothermal compression or expansion.

[0086] Fig. 2 Figure 20 shows a longitudinal section view of a further embodiment of a device 20 for implementing quasi-isothermal changes of state in heat power processes or working machine processes according to the invention.

[0087] The essential difference between device 20 and device 1 is... Fig. 1 The feature consists in the fact that only a single access opening 21 is provided for introducing and extracting working gas into and out of the working chamber 3, as is the case, for example, when the device 20 is used as part of a Stirling engine. After compression or expansion of the working gas in the working chamber 3, it can be expelled through the opening 21.

[0088] Furthermore, device 20 differs from device 1 in that Fig. 1 The heat transfer medium 9 is injected in a shower-like solid jet into the working chamber 3 from above, essentially in the direction of the piston head surface 11. For this purpose, the cylinder head 10 has a multitude of small openings for the heat transfer medium.

[0089] Furthermore, device 20 differs from device 1 in that Fig. 1 A demister 22 is positioned in the annular gap 12. The intended pressure fluctuations in the working chamber 3 can lead to a slight, albeit fluctuating, gas uptake of the liquid heat transfer fluid 9. Therefore, it can be advantageous to reduce the settling velocity of the heat transfer fluid 9 by allowing it to trickle in the annular gap 12 and to effect degassing by means of the demister 22 directly in the working chamber 3. At the same time, this prevents the heat transfer fluid from being carried along with the rising and falling piston 4 across the annular gap 12, thus preventing it from coming to rest and making extraction / discharge and, if necessary, reinjection of the heat transfer fluid 9 more difficult.

[0090] It should be noted that the provision of a demister 22 does not necessarily refer to the embodiment described in Fig. 2 The device shown in 20 is limited, but can optionally also be equipped with a device of the type of device 1. Fig. 1 can be combined. Conversely, another exemplary device according to the invention (not shown) can be constructed according to the type of device 20. Fig. 2 , i.e., with only one access opening 21, and can also be implemented without a demister 22. Similarly, the specific method of heat transfer fluid injection, e.g., in the form of individual spray cones as in Fig. 1 shown or effervescent as in Fig. 2 The illustrations can be combined arbitrarily with any of the embodiments disclosed herein.

[0091] Furthermore, if the working gas contains too high a proportion of liquid heat transfer fluid after compression / expansion, the excess liquid can be separated from the working gas by means of a separate separator, separator, or similar device. Such a separator can be located, in particular, outside of cylinder 2. The heat transfer fluid separated in this way can, if desired, be returned to the heat transfer fluid circuit or, alternatively, be discharged from the circuit. To separate large droplets, an insert in the form of an orifice / metal grid or similar can optionally be installed at the heat transfer fluid outlet opening 8 inside cylinder 2.

[0092] Fig. 3 Figure 1 shows a longitudinal sectional view of a further embodiment of a device 25 for implementing quasi-isothermal state changes in heat engine processes or machine processes according to the invention. In this embodiment, the piston 4 of the device 25, or rather the head surface 11 of the piston 4, is inclined with respect to its longitudinal axis 19. The cylinder head 10 is shaped according to the piston shape. The spray cone of the heat transfer medium 9 to be injected is aligned approximately parallel to the piston head surface 11, so that a spray length of the spray cone of the injected heat transfer medium 9 is maintained even when the Fig. 3 The piston position shown is still sufficiently large near top dead center to optimally achieve the effect described here (e.g., heat transfer to the working gas).

[0093] Fig. 4 presents a flow diagram of an embodiment of a method for implementing quasi-isothermal changes of state in heat power processes or working machine processes according to the invention, using the device 1 as an example. Fig. 1 The device 1 is shown in Fig. 4 The cylinder 2 is operated as a compressor, for example. The air or working gas enters the cylinder 2 via the intake valve / inlet opening 5 and, after compression, is expelled via the pressure valve / outlet opening 6. In this example, the delivery of the liquid heat transfer fluid 9 is achieved with a hydraulic pump 26, a pressure accumulator 28, and a pressureless tank 27. The pressurization of the heat transfer fluid injection nozzles 7 and the discharge of a sump from the heat transfer fluid outlet opening 8 are controlled by valves 29 and 30. The pump 26 delivers the heat transfer fluid from the pressureless tank 27 to the pressure accumulator 28. The pump 26 is preferably pressure-controlled. A heat exchanger 34 adds or removes heat from the heat transfer fluid, depending on the application. In this embodiment, any remaining heat transfer fluid droplets and the compressed working gas are additionally separated from each other in a separator 31 located outside the cylinder 2.The separated heat transfer fluid can flow back into the unpressurized tank 27 via a valve 32. The compressed, dried working gas exits the separator 31 (33). In this example, the piston 4 is driven by a crank drive 15, i.e., by means of a connecting rod and crank mechanism, and a sealing assembly 18.

[0094] Fig. 5 presents a flow diagram of a further embodiment of a method for implementing quasi-isothermal changes of state in heat power processes or working machine processes according to the invention using the device 20. Fig. 2 In the illustrated application, cylinder 2 represents an exemplary cylinder of a Stirling engine (not shown). Cylinder 2 has only one access port 21 for the working gas to a regenerator. In this embodiment, a double-acting pump piston 38 delivers the heat transfer fluid from the heat transfer fluid outlet port 8 to at least one heat transfer fluid injection port 7. The double-acting pump piston 36 is configured to simultaneously inject the heat transfer fluid 9 into the working chamber 3 via the at least one heat transfer fluid injection port 7 and to discharge or extract it from the working chamber 3 via the at least one heat transfer fluid outlet port 8.

[0095] A piston control 39 of the pump piston 38 can be, for example, hydraulically, electromechanically, or via a crank mechanism and is synchronized with the movement of the working piston 4 in the cylinder 2, so that, depending on the application, the latter injects / injects heat transfer fluid 9 during expansion or compression. The stroke volume, stroke start time, and duration must be selected accordingly. Three check valves 35, 36, 37 prevent backflow of the heat transfer fluid 9 into the cylinder 2, e.g., into the heat transfer fluid sump within the cylinder 2, and ensure that the gas volume is not altered by the injection of the heat transfer fluid 9 into the working chamber 3.

[0096] In the present example, the working piston 4 is hydraulically driven by a plunger cylinder (14). Stroke duration and stroke speed can be controlled via a hydraulic connection 40. The hydraulic drive 14 enables discontinuous piston control of the working piston 4. A heat exchanger 34 transfers heat to or from the heat transfer medium, depending on the application.

[0097] The hydraulic connection 40 can be used to establish a hydraulic coupling between the working piston 4 and the double-acting pump piston 38, although it is not necessarily limited to a hydraulic coupling. A mechanical coupling between the working piston 4 and the pump piston 38 is also conceivable. In any case, a direct coupling between the working piston 4 and the pump piston 38 enables the functionality of the injection system to be independent of absolute pressures and pressure ratios. With conventional injection systems, the injection duration, timing, and injection pressures must be programmed in a complex manner depending on the operating parameters. Furthermore, the valves with their corresponding switching times are only usable for certain operating ranges.The invention enables a significantly wider operating range to be covered by a simple drive device with a hydraulic / mechanical coupling, without the need for complex programming and parameterization of the valves and switching times. Furthermore, the direct hydraulic / mechanical coupling eliminates the need for additional auxiliary energy sources such as power supplies and conversion efficiencies for pumps and actuators (in valves).

[0098] In both flowcharts shown, the Fig. 4 and 5 The working gas is introduced into and / or discharged from the working chamber 3 via the at least one access opening 5, 6 or 21 in the cylinder 2, wherein the heat transfer medium 9 is injected into the working chamber 3 via the at least one heat transfer medium injection opening 7 and the heat transfer medium 9 is discharged from the working chamber 3 at a different location than the working gas via the at least one heat transfer medium outlet opening 8.

[0099] The injection and / or extraction of a quantity of the heat transfer medium 9 during a cycle of the quasi-isothermal change of state in the heat engine process or the machine process can advantageously be carried out non-linearly. For this purpose, for example, the piston control 39 can displace the pump piston 38 accordingly in a non-linear manner.

[0100] It should be noted that the provision of the double-acting pump piston 38 and / or the hydraulic drive 14 does not necessarily have to be limited to the embodiment shown in the figure. Fig. 5 is limited, but also includes an exemplary embodiment according to Fig. 4 can be combined, that is, the double-acting pump piston 38 can, for example, be combined with an embodiment with a mechanical drive 15 of the working piston 4. Conversely, the hydraulic pump 26 can, of course, be combined according to Fig. 4 also with the hydraulic drive 14 of the working piston 4 according to an embodiment according to Fig. 5 can be combined.

[0101] Fig. 6 This represents an exemplary pressure profile of a working gas in relation to a pressure profile of a heat transfer medium in an exemplary device according to the invention. The device can, for example, be similar to device 1. Fig. 1 or device 20 from Fig. 2 be designed. In any case, the device has a double-acting pump piston similar to the one in Fig. 5 illustrated pump piston 38.

[0102] In Fig. 6 The pressure profile of the working gas in the cylinder is shown as an example of compression by solid line 41. The pressure profile of the heat transfer fluid to be injected into the cylinder is shown by a dashed line 42. For comparison, the pressure profile of a heat transfer fluid with a conventional heat transfer fluid reservoir at constant pressure and valve control is shown by a dashed line 43 (not part of the invention). Fig. 6 It is clearly evident that the pressure profile 41 of the working gas increases non-linearly over time t during the exemplary compression. This is achieved by means of a non-linear control of the double-acting pump piston 38 (see...). Fig. 5 With this system, it is possible to keep the pressure difference Δp of the heat transfer fluid injected into the working chamber constant throughout the entire cycle. This results in a uniform spray pattern of the heat transfer fluid in the working chamber throughout the entire work cycle and also minimizes the injection effort. In contrast, the pressure difference between the pressure 43 of the heat transfer fluid to be injected and the pressure 41 of the working gas in the cylinder changes considerably during the work cycle in a conventional injection system with a reservoir and valve control, causing an uneven spray pattern of the heat transfer fluid.

[0103] The device and method disclosed herein for implementing quasi-isothermal changes of state in heat engine processes or machine processes with quasi-isothermal compression or expansion are not limited to the specific embodiments disclosed herein, but also include further embodiments with the same effect, resulting from technically useful combinations of the features of both the device and the method described herein. In particular, the features and combinations of features mentioned above in the general description and the description of the figures and / or shown in the figures alone are not only usable in the combinations explicitly specified herein, but also in other combinations or on their own, without departing from the scope of the claimed invention.

[0104] The device disclosed herein for implementing quasi-isothermal state changes in heat engine processes or machine processes with quasi-isothermal compression or expansion is particularly advantageous for converting available energy from renewable energy sources, e.g., solar thermal energy, into electrical energy, although its use is not necessarily limited to such applications. The converted electrical energy can be made available for direct use by the device according to the invention, for example, in households or industrial plants and the like. Bezugszeichenliste

[0105] 1 Device 2 Cylinder 3 Working chamber 4 Piston 5 First access opening 6 Second access opening 7 Heat transfer fluid injection opening 8 Heat transfer fluid outlet opening 9 Heat transfer fluid 10 Cylinder head 11 Piston head surface 12 Annular gap 13 Sump 14 Hydraulic drive 15 Mechanical drive 16 Seal 17 Sliding guide 18 Sealing package 19 Piston longitudinal axis 20 Device 21 Access opening 22 Demister 25 Device 26 Hydraulic pump 27 Unpressurized tank 28 Pressure accumulator 29 Valve 30 Valve 31 Separator 32 Valve 33 Outlet 34 Heat exchanger 35 Check valve 36 Check valve 37 Check valve 38 Double-acting pump piston 39 Piston actuation 40 Hydraulic connection 41 Pressure profile of working gas 42 Pressure profile of a heat transfer fluid according to the invention 43 Pressure profile of a heat transfer fluid in a conventional storage tank G Gravity direction pPressure ΔpConstant pressure difference tTime

Claims

1. Device (1, 20, 25) for realizing quasi-isothermal changes of state in thermal power processes or work machine processes, having a cylinder (2) which provides a working space (3), having a piston (4) which is displaceable in the working space (3) and serves for delimiting a gas volume which is able to be changed in the working space (3), wherein the cylinder (2) has at least one access opening (5, 6, 21) for introducing working gas into and / or discharging it from the working space (3), has at least one heat carrier injection opening (7) for injecting a heat carrier (9) into the working space (3), and has at least one heat carrier outlet opening (8) for discharging the heat carrier (9) from the working space (3), wherein the at least one heat carrier outlet opening (8) and the access opening (6, 21) for discharging the working gas are separate openings, characterized in that the piston (4) is designed as a plunger.

2. Device according to the preceding claim, characterized in that the at least one heat carrier outlet opening (8) is arranged below the at least one heat carrier injection opening (7) in the direction of gravitational force (G) with respect to an operating position of the cylinder (2).

3. Device according to either of the preceding claims, characterized in that the at least one heat carrier injection opening (7) is arranged in an upper end portion of the working space (3) in the direction of gravitational force (G) with respect to an operating position of the cylinder (2).

4. Device according to either of the preceding claims, characterized in that a head surface (11) of the piston (4) is formed so as to be inclined in relation to a piston longitudinal axis (19), conical or domed, preferably dish-shaped.

5. Device according to either of the preceding claims, characterized in that a ring-shaped gap (12) is provided upstream of the heat carrier outlet opening (8) between the piston (4) and a cylinder inner wall of the cylinder (2) for collecting the heat carrier (9) prior to the discharge thereof.

6. Device according to the preceding claim, characterized in that a demister (22) is arranged in the ring-shaped gap (12).

7. Device according to either of the two preceding claims, characterized in that a sump space (13) for collecting the inflowing heat carrier (9) is provided at the lower end of the ring-shaped gap (12) in the direction of gravitational force (G) with respect to an operating position of the cylinder (2).

8. Device according to either of the preceding claims, characterized by a double-acting pump piston (38) which is configured to simultaneously both inject the heat carrier (9) into the working space (3) via the at least one heat carrier injection opening (7) and discharge said heat carrier from the working space (3) via the at least one heat carrier outlet opening (8).

9. Method for realizing quasi-isothermal changes of state in thermal power processes or work machine processes in which a working space (3) is provided within a cylinder (2) and a changeable gas volume is delimited in the working space (3) by a piston (4) which is displaceable in the working space (3), wherein a working gas is introduced into and / or discharged from the working space (3) via at least one access opening (5, 6, 21) in the cylinder (2), wherein a heat carrier (9) is injected into the working space (3) via at least one heat carrier injection opening (7) and the heat carrier (9) is discharged from the working space (3), at a different location than the working gas, via at least one heat carrier outlet opening (8), characterized in that the piston (4) is designed as a plunger.

10. Method according to Claim 9, characterized in that the heat carrier (9) is injected into the working space (3) in an upper end portion of the working space (3), and is discharged below the at least one heat injection opening (7), in the direction of gravitational force (G) with respect to an operating position of the cylinder (2).

11. Method according to either of Claims 9 and 10, characterized in that the injected heat carrier (9) is diverted into the direction of the heat carrier outlet opening (8) via a correspondingly formed head surface (11) of the piston (4).

12. Method according to either of Claims 9 and 11, characterized in that the heat carrier (9) is collected upstream of the heat carrier outlet opening (8) in a ring-shaped gap (12) between the piston (4) and a cylinder inner wall of the cylinder (2) prior to being discharged from the working space (3).

13. Method according to the preceding claim, characterized in that a ring diameter of the ring-shaped gap (12) is selected in a range of 0.1 mm to 2 mm, preferably between 0.15 mm and 1.5 mm, and more preferably between 0.2 mm and 1.5 mm.

14. Method according to either of the two preceding claims, characterized in that the heat carrier (9) is collected in a sump space (13) at the lower end of the ring-shaped gap (12) in the direction of gravitational force (G) with respect to an operating position of the cylinder (2) prior to being discharged.

15. Method according to either of Claims 9 and 14, characterized in that the heat carrier (9) is simultaneously both injected into the working space (3) via the at least one heat carrier injection opening (7) and extracted by suction from the working space (3) via the at least one heat carrier outlet opening (8) through the use of a double-acting pump piston (38).

16. Method according to either of Claims 9 and 15, characterized in that the injection and / or extraction by suction of a quantity of the heat carrier (9) during the quasi-isothermal change of state is realized in a nonlinear manner.

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