Patent Application
20240125312
The present invention relates to a piston compressor, more particularly, for a heat pump, comprising a cylinder, a piston, which is mounted in the cylinder for linear movement along a cylinder's longitudinal axis, a working chamber, which is formed in the cylinder with its volume capable of being changed via a piston movement and fluidically connected to a working-medium inlet chamber by means of a first valve portion of a valve device and to a working-medium outlet chamber by means of a second valve portion of the valve device, wherein the working chamber is delimited by an inner lateral surface of the cylinder, a piston end face formed on the piston's end and a working-chamber head portion arranged opposite from the piston end face, wherein the working-chamber head portion is formed from a geometric arrangement of the first and second valve portions.
The piston compressor proposed according to the invention can be used, for example, for thermodynamic heating systems, such as heat pumps, more particularly, for high-temperature heat pumps. However, an implementation of the present invention in a thermodynamic cooling system, for example, a refrigerator or an air-conditioning system, is also included. The piston compressor proposed according to the invention can also be used in other systems.
The technology of heat pumps is generally well known. For example, heat pumps are used to absorb thermal energy from a first external medium (e.g., ambient air or liquids) using technical or mechanical effort, thereby transferring it to a second external medium as useful energy or useful heat as a result of the drive energy used. The second external medium is a medium to be heated. When implementing such a system in a geothermal plant, the first external medium may be liquids contained in the earth's rock, but, in industrial processes, waste heat can also serve as the first external medium.
Currently, heat pumps are used, in particular, for heating buildings. However, applications have also become known in which heat pumps are used to generate heat required for industrial processes. For industrial processes, high-temperature heat pumps with media temperatures of >100° C. are often used or required.
In DE 10 2011 086 476 A1, the basic heat pump principle is clearly described using the example of a high-temperature heat pump. The heat pump there has a fluid circuit for absorbing thermal energy by the fluid (working medium) from at least one first reservoir using technical work and for delivering thermal energy through the fluid to at least a second reservoir for heating the at least one second reservoir.
In addition to an evaporation unit, a condensation unit, and an expansion unit, standard heat pumps (also high-temperature heat pumps) comprise a compressor for compressing a working medium circulating in a fluid circuit. In the evaporation unit, the working medium transformed from the liquid to the gaseous state is sucked in by the compressor and compressed to a pressure level required for liquefaction of the working medium. While the (for example, electrically) driven compressor compresses the vaporous working medium from a low outlet pressure level to a higher final pressure level, the temperature of the working medium increases. From prior art, different compressor variants are known, for example, reciprocating compressors, scroll compressors, screw compressors, rotary compressors, and rotary-piston compressors (this list is not exhaustive). Reciprocating compressors, for example, are based on the principle that a moving piston sucks in the gaseous working medium out of a suction chamber (working-medium inlet chamber) through a suction valve in the direction of a working chamber when the piston moves downwards along a cylinder's longitudinal axis into a cylinder surrounding the piston. The working medium is compressed when the piston experiences an upward movement along the cylinder's longitudinal axis. In reciprocating compressors, the suction valve is closed during compression of the working medium. The working medium leaves the working chamber via an outlet valve (pressure valve) in the direction of a working-medium outlet chamber if the pressure in the cylinder or in the working chamber exceeds a pressure level present on a high-pressure side of the compressor. In the context of the present invention, the compressor is commonly referred to as a piston compressor. The actual compressor can interact directly with other components, such as a drive unit driving the compressor (e.g., an electric motor) and a lubricant reservoir.
The invention can relate to different designs of compressor systems, including an open compressor system, a semi-hermetic compressor system or a hermetic compressor system. In open compressor systems, the drive unit (the motor) is structurally separated from the compressor. A drive shaft of the compressor is led out of the housing and connected to the drive unit. In semi-hermetic compressor systems, the drive unit and the compressor are arranged in a common housing. In a hermetic compressor system, the drive unit and compressor are also arranged in a common housing, but in contrast to a semi-hermetic compressor system, this is completely outwardly welded.
As a rule, the mentioned compressors or compressor systems comprise a lubricant reservoir for holding a lubricant. A lubricant can also be understood as a lubricant mixture. The lubricant is used to lubricate components of the compressor or compressor system, in particular, the moving components of the compressor (e.g., pistons, cylinders, bearings, valves, etcetera). Well-known lubricant reservoirs are often referred to as “oil sumps”. The oil or lubricant is sucked in from the oil sump or lubricant reservoir and transported to the respective points to be lubricated.
Well-known piston compressors comprise a working chamber with a flat working-chamber head portion; i.e., the valve plates used there (these separate the working chamber from a working-medium inlet chamber and a working-medium outlet chamber) are flat and perpendicular to the longitudinal axis of a cylinder mounted in the cylinder for movement along the cylinder's longitudinal axis. The end face of the piston, which is opposite the valve plates, is also flat. A part of the valve plate surfaces is used for suction valves, the other part of them is used for outlet valves. Such an arrangement causes the suction gas to flow directly past the ejected gas, which can cause unwanted energy or heat losses.
More particularly, when using piston compressors in a high-temperature heat pump, due to the working medium used there, which has a higher density compared to classic working media, the associated higher pressure losses and poorer flow properties are compensated. Otherwise, this would lead to inherent losses in the efficiency of the compressor and, ultimately, in the efficiency of the system containing the compressor, which can be provided, for example, by a high-temperature heat pump.
Accordingly, the object of the present invention is to provide a piston compressor and a heat pump with improved efficiency and effectiveness.
The present invention relates to a piston compressor, more particularly, for a heat pump, comprising a cylinder, a piston, which is mounted in the cylinder for linear movement along a cylinder's longitudinal axis, a working chamber, which is formed in the cylinder with its volume capable of being changed via a piston movement and fluidically connected to a working-medium inlet chamber by means of a first valve portion of a valve device and to a working-medium outlet chamber by means of a second valve portion of the valve device, wherein the working chamber is delimited by an inner lateral surface of the cylinder, a piston end face formed on the piston's end and a working-chamber head portion arranged opposite from the piston end face, wherein the working-chamber head portion is formed from a geometric arrangement of the first and second valve portions.
The piston compressor according to the invention is characterized in that the first and second valve portions are arranged in such a way that the working chamber is tapered toward the working-chamber head portion.
It should be emphasized that a piston compressor according to the invention can comprise individual piston-cylinder units or a plurality thereof. However, the invention is exemplified by a piston-cylinder unit composed of a piston and a cylinder. Accordingly, each of the piston-cylinder units can have the following features:
Depending on the position of the piston in the cylinder (the piston is driven by a corresponding drive unit), the volume of the working chamber decreases or increases. It is desirable that the working chamber has the lowest possible dead volume when the piston is positioned close to the working-chamber head portion (i.e., near the working-medium inlet chamber and the working-medium outlet chamber). A “linear movement” of the piston is understood to mean, in particular, a back-and-forth movement of the piston in the interior of the cylinder.
The working-medium inlet chamber provides a low-pressure side of the system, while the working-medium outlet chamber provides a high-pressure side. A flow connection between the working-medium inlet chamber and the working chamber is to be understood that working medium from the working-medium inlet chamber can flow into the working chamber at a corresponding piston position. In the working chamber, the working medium is then compressed and can flow out of the working chamber (induced by the piston movement) in the direction of the working-medium outlet chamber. To provide the flow connections between the working chamber and the aforementioned inlet or outlet chambers, the first and second valve portions can have valve openings (e.g., slots, hole openings).
The first and second valve portions can be designed in a known manner, for example, in the form of valve plates. The working-chamber head portion can be exclusively delimited by the first and second valve portions. The tapered geometry of the working chamber in the direction of the working-chamber head portion ensures that the contact surface between the working chamber and the respective chambers is increased. This increases the area available for valve portions (e.g., valve plates). With the increased area of the valve portions, the pressure loss is reduced. With the proposed geometry, the working medium flowing into and out of the working chamber no longer flows directly past each other. Flow separation is improved, which avoids unwanted heat transfers.
In the following, favorable embodiments of the invention are explained, which can serve as a piston compressor according to the invention as well as a heat pump according to the invention, more particularly, a high-temperature heat pump.
In accordance with a first favorable embodiment of a piston compressor proposed by the invention, it can be provided that the first and second valve portions are each arranged at an angle not equal to 90° to the cylinder's longitudinal axis L. This means that the valve device is not arranged perpendicular to the cylinder's longitudinal axis but provides a roof-like cross-section so that the working chamber tapers in the direction of the working-chamber head portion. Since one of the valve portions is flow-connected to the working-medium inlet chamber and one of the valve portions is flow-connected to the working-medium outlet chamber, such an arrangement avoids direct flow of the working medium flowing into the working chamber past the working medium flowing out of the working chamber. This also increases the surface area of the valve device—compared to the arrangements known from prior art.
In accordance with the first favorable embodiment of a piston compressor proposed by the invention, it can be provided that the first and second valve portions are each arranged at an angle deviating from one another relative to the cylinder's longitudinal axis L. By this, it is understood that the first and second valve portions cannot be arranged symmetrically to each other. An asymmetrical arrangement is also possible.
In accordance with another favorable embodiment of a piston compressor proposed by the invention, it can be provided that the first and second valve portions are each arranged at the same angle relative to the cylinder's longitudinal axis L. In such an embodiment, the valve portions are arranged symmetrically and preferably have the same shape and dimensions (length, width, diameter), i.e., thereby providing the same surface area.
In accordance with a further favorable embodiment of a piston compressor proposed by the invention, it can be provided that the working-chamber head portion terminates at an acute or obtuse angle with respect to its cross-section, wherein the acute or obtuse angle is spanned by the first and second valve portions. The angle spanned by the first and second valve portions can be selected depending on the installation space requirements or the structural conditions of the piston compressor. In accordance with a further favorable embodiment of a piston compressor proposed by the invention, it can be provided that the working-chamber head portion terminates at a right angle with respect to its cross-section, wherein the right angle is spanned by the first and second valve portions.
In accordance with another favorable embodiment of a piston compressor proposed by the invention, it can be provided that the working-chamber head portion comprises a concave cross-sectional shape in the direction of the working chamber. In this context, concave can be understood as a curved cross-section in which the working chamber tapers toward the working-chamber head portion. In this context, concave can also mean an arrangement of one of the aforementioned angles between the first and second valve portions.
In accordance with another favorable embodiment of a piston compressor proposed by the invention, it can be provided that the first and second valve portions are each arranged in such a way that they provide a working-chamber head portion shaped like a hemisphere. This leads to a further increase in the surface area of the valve device or the valve portions when compared to the known systems from the prior art. It should be noted that the surface area enlargement compared to prior art always means a relative increase in surface area in relation to the respective size of the piston compressor used.
In accordance with another favorable embodiment of a piston compressor proposed by the invention, it can be provided that the piston end face geometrically corresponds to the working-chamber head portion. This means that the piston can displace the working medium as fully as possible from the working chamber when compressing it. It also minimizes dead volume. If, for example, the working-chamber head portion is concave in the direction of the working chamber, the piston end face preferably has a convex shape in the direction of the working-chamber head portion. The geometric design of the working-chamber head portion and the piston end face can be designed in accordance with a key-lock principle.
In accordance with another favorable embodiment of a piston compressor proposed by the invention, it can be provided that the working-medium inlet chamber and the working-medium outlet chamber are separated from another via a separator adjacent to the working-chamber head portion. On the one hand, the separator prevents direct mass transfer between working medium contained in the working-medium inlet chamber and the working-medium outlet chamber (this is done via the working chamber), and on the other hand, the separator reduces or prevents heat transfer between the working-medium inlet chamber and the working-medium outlet chamber. For this purpose, it may be provided that the separator comprises an insulation layer arranged between a wall of the working-medium inlet chamber and a wall working-medium outlet chamber, more particularly, an air gap. If the insulation layer is an air gap, then air provides the thermal insulating medium. This reduces the construction effort and simplifies the replacement of the insulation layer. The air can be released or supplied via a suitable valve. Another thermally insulating material may also form the separator or be arranged in a cavity between the working-medium inlet chamber and the working-medium outlet chamber. Also, a plurality of cavity chambers or channels can be provided to form the separator. The thermally insulating material may also be a ceramic material, a plastic, a composite material, a textile material, a glass, an oil, or any other suitable insulating agent with thermally insulating properties.
As mentioned, the invention furthermore relates to a heat pump, more particularly, a high-temperature heat pump comprising one or a plurality of piston compressor(s) designed according to the invention.
A piston compressor according to the invention is preferably used in a high-temperature heat pump. This can be a high-temperature heat pump with temperatures of the heat-absorbing external medium with a temperature of >100° C. One or a plurality of the piston compressors described above can be provided, wherein each of the piston compressors can comprise one or a plurality of piston-cylinder units of the aforementioned type. Reciprocating compressors are particularly suitable for this purpose.
It should also be noted that the conjunction “and/or” used herein, placed between two features and linking them with each other 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 can be present, in a second embodiment, only the second feature can be present, and, in a third embodiment, both the first as well as the second feature can be present.
The features described in the context of the present invention may provide both favorable embodiments of a piston compressor according to the invention as well as a heat pump according to the invention. All of the features described here can therefore be used across claim category boundaries.
Further features and advantages of the invention result from the following description of a non-restrictive exemplary embodiment of the invention, which is explained in more detail below with reference to the drawings. The drawings schematically show:
The working chamber 3 is flow-connected via a first valve portion 11 of a valve device 4 to a working-medium inlet chamber 5 and flow-connected to a working-medium outlet chamber 6 via a second valve portion 12 of the valve device 4. The working chamber 3 is delimited by an inner lateral surface 7 of cylinder 1, a piston end face 8 formed at one end of the piston 2 and a working-chamber head portion 9 opposite to the piston end face 8, wherein the working-chamber head portion 9 is formed from a geometric arrangement of the first and second valve portions 11, 12. In the case of the arrangement known from the prior art and shown in
In the case of such piston compressors, the working chamber 3—as mentioned comprises a working-chamber head portion 9. This is flat and perpendicular to the cylinder's longitudinal axis L of cylinder 1, which is mounted for movement along the cylinder's longitudinal axis L of piston 2. The piston end faces 8 lying opposite valve portions 11, 12 are also flat. Part of the surfaces of the first valve portions 11 (in the present case, there are two first valve portions 11 on the outer sides) are used for suction valves. The same applies to the area of the second valve portion (centered), which is used in part for the arrangement of outlet valves. Such an arrangement causes the suction gas to flow directly past the ejected gas, which can cause unwanted energy or heat losses.
The tapered geometry of the working chamber 3 in the direction of the working-chamber head portion 9 ensures that the contact surface between the working chamber 3 and the respective chambers (working-medium inlet chamber 5, working-medium outlet chamber 6) is increased. This increases the area available for valve portions 11, 12. With the increased area of the valve portions 11, 12, the pressure loss is reduced. With the proposed geometry, the working medium flowing into and out of the working chamber 3 does not flow directly past each other—as is the case in the prior art. Flow separation is improved, which avoids unwanted heat transfers.
The working-medium inlet chamber 5 and the working-medium outlet chamber 6 are separated from each other by a separator 10 (shown by the dotted line) adjacent to the working-chamber head portion 9. The separator 10 comprises an insulation layer arranged between a wall of the working-medium inlet chamber 5 and a wall of the working-medium outlet chamber 6, which can be designed, in particular, in the form of an air gap. This also reduces heat loss.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 102 648.2 | Feb 2021 | DE | national |
This application is a U.S. National phase of PCT/EP2022/051951 filed Jan. 27, 2021, which published as PCT Publication WO2022/167326, which claims priority to German Application No. DE 10 2021 102 648.2 filed Feb. 4, 2021, both of which are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/051951 | 1/27/2022 | WO |
