Piston compressor, especially for heat pump

Abstract

The invention relates to a piston compressor comprising a cylinder (1), a piston (2) mounted for linear movement along a cylinder longitudinal axis (L), and a working chamber (3) fluidly connected to a working medium inlet chamber (5) by a first valve portion (11) and to a working medium outlet chamber (6) by a second valve portion (12), the working chamber (3) being bounded by an inner side surface (7), a piston end face (8) and a working chamber head portion (9) which is formed by a geometric arrangement of the first and second valve portions (11, 12). To ensure improved efficiency, the first and second valve portions (11, 12) are arranged such that the working chamber (3) tapers towards the working chamber head portion (9).

Description

[Technical field]

[0001] The present invention relates to a piston compressor, in particular for a heat pump, comprising a cylinder, a piston mounted in the cylinder for linear movement along a longitudinal axis of the cylinder, and a working chamber formed in the cylinder, the volume of which is variable via piston movement and which is fluidly connected to a working medium inlet chamber by a first valve part of a valve device and to a working medium outlet chamber by a second valve part of the valve device, wherein the working chamber is bounded by an inner side surface of the cylinder, a piston end face formed at an end of the piston and a working chamber head portion arranged opposite the piston end face, the working chamber head portion being formed by a geometric arrangement of the first and second valve parts. [Background technology]

[0002] The piston compressor proposed by the invention can be used in thermodynamic heating systems, for example heat pumps, in particular high temperature heat pumps, although thermodynamic cooling systems, for example refrigerators, air conditioning systems, etc., are not excluded from the scope of the invention. The piston compressor proposed by the invention can also be used in other systems.

[0003] Heat pump technology is generally well known. For example, a heat pump uses a technical or mechanical mechanism to absorb thermal energy from a first external medium (for example the surrounding air or liquid) and transfer it to a second external medium as useful energy in addition to the driving energy used, or as useful heat. The second external medium is the medium to be heated. When such a system is implemented in a geothermal power plant, the first external medium can be the liquid contained in the soil, while in industrial processes the first external medium can be waste heat.

[0004] Currently, heat pumps are used primarily for heating buildings, but the use of heat pumps to generate heat for industrial processes is also becoming known, where high-temperature heat pumps with medium temperatures > 100°C are often used or required.

[0005] In DE 10 2011 086 476 A1 the basic heat pump principle is clearly explained on the example of a high-temperature heat pump, which has a fluid circuit which, by technical operation, absorbs thermal energy of a fluid (working medium) from at least one first storage tank and transfers the thermal energy via the fluid to at least one second storage tank for heating the latter.

[0006] Heat pumps (also high-temperature heat pumps) are equipped as standard with a compressor for compressing the working medium circulating in the fluid circuit, in addition to the evaporation unit, the condensation unit and the expansion unit. In the evaporation unit, the equipment transported from liquid to gas is sucked into the compressor, where it is compressed to the pressure level required for liquefying the working medium. The (e.g. electrically) driven compressor compresses the working medium in vapor form from a low outlet pressure level to a high final pressure level compressor, while the temperature of the working medium increases. From the prior art, various variants of compressors are known, e.g. reciprocating compressors, scroll compressors, screw compressors, rotary compressors, rotary piston compressors, etc. (This list is not exhaustive). Reciprocating compressors are based on the principle that the gaseous working medium is sucked by the moving piston from a suction chamber (working medium inlet chamber) in the direction of the working chamber through a suction valve, as the piston moves downwards along the cylinder longitudinal axis into the cylinder surrounding the piston. The working medium is compressed as the piston moves upwards along the cylinder longitudinal axis. In a reciprocating compressor, the suction valve is closed while the working medium is compressed. When the pressure in the cylinder or working chamber exceeds the pressure level of the high pressure side of the working chamber of the compressor, the working medium leaves the working chamber through the outlet valve (pressure valve) in the direction of the working medium outlet chamber. "Compressor" may be synonymous with "compressor". In the present invention, compressor generally refers to piston compressors. The actual compressor may directly interact with other components such as a drive (e.g., electric motor, etc.) that drives the compressor and a lubricant reservoir.

[0007] The present invention may relate to different designs of compressor systems, including open, semi-hermetic and hermetic compressor systems. In an open compressor system, the drive (motor) is structurally separate from the compressor. The compressor drive shaft is led out of the housing and connected to the drive. In a semi-hermetic compressor system, the drive and compressor are located in a common housing. In a hermetic compressor system, the drive and compressor are also located in a common housing, but unlike the semi-hermetic compressor system, they are completely welded to the outside.

[0008] As a rule, the compressor or compressor system described above comprises a lubricant reservoir for holding a lubricant, which may also be understood as a lubricant mixture. The lubricant is used to lubricate the components of the compressor or compressor system, in particular the moving parts of the compressor (pistons, cylinders, bearings, valves, etc.). Known lubricant reservoirs are often called "Oil Sumps". Oil or lubricant is sucked from the oil or lubricant reservoir and sent to each point to be lubricated.

[0009] Known piston compressors have a working chamber with a flat working chamber head, i.e. (distinguishing the working chamber from the working medium inlet and outlet chambers) the valve plate is flat and perpendicular to the longitudinal axis of the cylinder and is mounted in a cylinder that moves along the longitudinal axis of the cylinder. The piston end face opposite the valve plate is also flat. Part of the valve plate surface is used for the suction valve and another part is used for the outlet valve. In the above mentioned arrangement the aspirated gas flows directly past the ejected gas, which can cause unnecessary energy and heat losses.

[0010] More specifically, when using piston compressors in high temperature heat pumps, the use of a denser working medium compared to conventional working media compensates for the associated higher pressure losses and poorer flow characteristics that would otherwise cause inherent losses in compressor efficiency and in the system including the compressor, which can be provided, for example, by a high temperature heat pump.

[0011] SUMMARY OF THE PRESENT EMBODIMENT It is therefore an object of the present invention to provide a more efficient and effective piston compressor and heat pump.

[0012] In order to solve the above problems, the present invention proposes a piston compressor having the features of claim 1 and a heat pump having the features of claim 13.

[0013] It should also be noted that the conjunction "and / or" as used herein, which is placed between two features and connects them to one another, is always interpreted such that in a first embodiment of an 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 second features may be present.

[0014] The features described in the present invention make it possible to provide preferred embodiments of both the piston compressor according to the invention and the heat pump according to the invention, so that all the features described here can be used beyond the boundaries of the claim categories. Summary of the Invention

[0015] The present invention relates to a piston compressor, in particular for a heat pump, comprising a cylinder, a piston mounted in the cylinder for linear movement along a longitudinal axis of the cylinder, and a working chamber formed in the cylinder, the volume of which is variable via piston movement and which is fluidly connected to a working medium inlet chamber by a first valve part of a valve device and to a working medium outlet chamber by a second valve part of the valve device, the working chamber being bounded by an inner side surface of the cylinder, a piston end face formed at an end of the piston and a working chamber head part arranged opposite the piston end face, the working chamber head part being formed by a geometric arrangement of the first and second valve parts.

[0016] In the piston compressor according to the invention, the first and second valve portions are arranged such that the working chamber tapers towards the working chamber head portion.

[0017] It is emphasized that the piston compressor according to the invention can consist of a single piston-cylinder section or multiple piston-cylinder sections. However, the invention is exemplified with a piston-cylinder section consisting of a piston and a cylinder. Each piston-cylinder section can thus have the following characteristics:

[0018] a cylinder;

[0019] a piston mounted within the cylinder for linear motion along a longitudinal axis of the cylinder;

[0020] a working chamber formed in a cylinder, the volume of which is variable via piston movement and which is fluidly connected to a working medium inlet chamber by a first valve part of a valve device and to a working medium outlet chamber by a second valve part of the valve device, the working chamber being bounded by an inner side of the cylinder, a piston end face formed at an end of the piston and a working chamber head part arranged opposite the piston end face, the working chamber head part being formed by a geometric arrangement of the first and second valve parts, the first and second valve parts being arranged such that the working chamber tapers towards the working chamber head part.

[0021] The volume of the working chamber increases or decreases depending on the position of the piston (which is driven by a corresponding drive) in the cylinder. The working chamber has the lowest dead volume when the piston is located near the working chamber head (i.e. closest to the working medium inlet and outlet chambers). A "linear movement" of the piston is understood to mean in particular the reciprocating movement of the piston inside the cylinder.

[0022] The working medium inlet chamber provides the low pressure side of the system, and the working medium outlet chamber provides the high pressure side of the system. The flow path connection between the working medium inlet chamber and the working chamber means that the working medium from the working medium inlet chamber flows into the working chamber at the corresponding piston position. The working medium is compressed in the working chamber and leaves the working chamber towards the working medium outlet chamber (urged by the movement of the piston). The first and second valve portions may have valve openings (e.g., grooves, holes, openings) to provide a flow path connection between the working chamber and the aforementioned inlet or outlet chambers.

[0023] The first and second valve parts may be designed in a well-known manner, for example in the form of a valve plate. The working chamber head part may be exclusively bounded by the first and second valve parts. The tapered shape of the working chamber towards the working chamber head part ensures a large contact surface between the working chamber and the respective chamber. This increases the area available for the valve part (e.g. valve plate). The increased area of ​​the valve part reduces the pressure losses. Due to the proposed shape, the working medium flowing into and out of the working chamber does not pass directly through each other. Flow separation is improved and unwanted heat transfer is avoided.

[0024] In the following, preferred embodiments of the present invention will be described, which may also be preferred embodiments of a piston compressor according to the present invention, or a heat pump, more particularly a high-temperature heat pump, according to the present invention.

[0025] In a first preferred embodiment of the piston compressor proposed by the invention, the first and second valve sections are each arranged at an angle other than 90° to the longitudinal axis L of the cylinder. This means that the valve device is not arranged at right angles to the longitudinal axis L of the cylinder, but is provided with a roof in cross section, such that the working chamber tapers in the direction of the working chamber head. One of the valve sections is in fluid communication with the working medium inlet chamber and one of the valve sections is in fluid communication with the working medium outlet chamber. Such an arrangement makes it possible to avoid a direct flow of the working medium into the working chamber through the working medium exiting the working chamber. It also makes it possible to increase the area of ​​the valve device compared to the arrangements known in the prior art.

[0026] In a first preferred embodiment of the piston compressor proposed by the present invention, the first and second valve parts are respectively arranged at an offset angle relative to the longitudinal axis L of the cylinder. It can be seen from this that the first and second valve parts cannot be arranged symmetrically to each other. An asymmetric arrangement is also possible.

[0027] In another preferred embodiment of the piston compressor proposed by the present invention, the first and second valve sections are each arranged at the same angle relative to the longitudinal axis L of the cylinder. In such an embodiment, the valve sections are arranged symmetrically and preferably have the same shape, the same dimensions (length, width, diameter), i.e. provide the same area.

[0028] In a further preferred embodiment of the piston compressor proposed by the invention, the working chamber head section terminates at an acute or obtuse angle relative to its cross section, the acute or obtuse angle spanning the first and second valve sections. The angle spanning the first and second valve sections is selected according to the installation space requirements or the structural conditions of the piston compressor. In a further preferred embodiment of the piston compressor proposed by the invention, the working chamber head section terminates at a right angle relative to its cross section, the right angle spanning the first and second valve sections.

[0029] In another preferred embodiment of the piston compressor proposed by the invention, the working chamber head has a cross-sectional shape that is concave in the direction towards the working chamber. In this case, the concave shape may be understood as a curved cross-section where the working chamber tapers towards the working chamber head. In this case, the concave shape may also mean an arrangement related to one of the above-mentioned angles between the first and second valve parts.

[0030] In another preferred embodiment of the piston compressor proposed by the invention, the first and second valve sections are each arranged to provide a hemispherical working chamber head, which allows a further increase in the area of ​​the valve device or valve sections compared to systems known from the prior art, it being noted that the increase in area compared to the prior art is relative to the respective size of the piston compressor used.

[0031] In another preferred embodiment of the piston compressor proposed by the present invention, the piston end face corresponds externally to the working chamber head, i.e., when the piston compresses the working medium, the working medium can be discharged as completely as possible from the working chamber, and this also minimizes the dead volume. For example, if the working chamber head has a concave shape in the direction towards the working chamber, the piston end face preferably has a convex shape in the direction towards the working chamber head. The geometric design of the working chamber head and the piston end face can be designed according to the key-lock principle.

[0032] In another preferred embodiment of the piston compressor proposed by the invention, the working medium inlet chamber and the working medium outlet chamber are separated from each other via a separator adjacent to the working chamber head. On the one hand, the separator prevents direct mass transfer between the working medium contained in the working medium inlet chamber and the working medium outlet chamber (which takes place 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, the separator may comprise an insulating layer, more particularly an air gap, arranged between the wall of the working medium inlet chamber and the wall of the working medium outlet chamber. If the insulating layer is an air gap, air is the insulating medium. This reduces the construction effort and also simplifies the replacement of the insulating layer. The air can be released or fed via a suitable valve. The separator may be formed of another insulating material and may be arranged in a cavity between the working medium inlet chamber and the working medium outlet chamber. The separator may also be formed by providing a plurality of hollow chambers or channels. The insulating material may also be ceramic material, plastic, composite material, fiber material, glass, oil or any other suitable insulating agent with insulating properties.

[0033] As mentioned above, the present invention further relates to a heat pump, and more particularly to a high temperature heat pump comprising one or more piston compressors designed according to the present invention.

[0034] The heat pump in which the piston compressor according to the invention is used is preferably a high temperature heat pump. This may be a high temperature heat pump in which the temperature of the heat absorbing external medium is above 100° C. There may be provided one or more piston compressors as described above, each of which may consist of one or more piston-cylinder parts as described above. For this purpose, reciprocating compressors are particularly suitable.

[0035] Further features and advantages of the invention emerge from the following description of a non-limiting embodiment of the invention which is explained in more detail with reference to the schematic drawings in which: FIG. [Brief description of the drawings]

[0036] [Figure 1] FIG. 1 shows a part of a piston cylinder section of a piston compressor known from the prior art.

[0037] [Diagram 2] FIG. 2 shows a portion of a piston cylinder section of a piston compressor designed in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] 1 shows a part of the piston-cylinder section of a piston compressor known from the prior art, showing a cylinder 1 (also called a cylinder housing) and a piston 2 mounted within the cylinder 1 for linear motion along the cylinder longitudinal axis. A working chamber 3 is formed within the cylinder 1, the volume of which varies with the movement of the piston 2.

[0039] The working chamber 3 is fluidly connected to the working medium inlet chamber 5 via a first valve section 11 of the valve device 4 and to the working medium outlet chamber 6 via a second valve section 12 of the valve device 4. The working chamber 3 is divided by an inner side surface 7 of the cylinder 1, a piston end face 8 formed at one piston end of the piston 2 and a working chamber head section 9 opposite the piston end face 8, the working chamber head section 9 being formed by a geometric arrangement of the first and second valve sections 11, 12. In the case of the arrangement shown in FIG. 1 and known from the prior art, the first valve section 11 is arranged at the same height as the (centrally arranged) second valve section 12. The valve sections 11, 12 are arranged at an angle of 90° to the longitudinal axis L of the cylinder. The piston 2 has an outside diameter corresponding to the inner diameter of the cylinder 1. The piston end face 8 has an outer shape corresponding to the working chamber head section 9. In this embodiment too, the piston end face 8 is arranged at right angles to the longitudinal axis L of the cylinder and has a flat shape.

[0040] In such a piston compressor, the working chamber 3 is constituted by the working chamber head 9, as mentioned above. It is flat, perpendicular to the longitudinal cylinder axis L of the cylinder 1 and mounted to move along the longitudinal cylinder axis L of the piston 2. The piston end face 8 opposite the valve sections 11, 12 is also flat. Part of the first valve section 11 (in this embodiment there are two first valve sections 11 on the outside) is used as an intake valve. The same applies to the area of ​​the second valve section (centre), which is partly used as an outlet valve. In the above-mentioned arrangement, the aspirated gas flows directly past the ejected gas, which can be a source of unnecessary energy and heat losses.

[0041] 2 shows a part of the piston-cylinder part of a piston compressor designed according to the invention. The first and second valve parts 11, 12 are arranged in such a way that the working chamber 3 tapers towards the working chamber head part 9, which is designed in a roof-shaped manner. The first and second valve parts 11, 12 are each arranged at an angle other than 90° to the cylinder longitudinal axis L. The piston end face 8 has a corresponding contour to the working chamber head part 9. In this case, the dotted lines indicate that the piston end face 8 is also roof-shaped, in particular with a triangular cross section.

[0042] The tapered shape of the working chamber 3 towards the working chamber head 9 ensures a large contact surface between the working chamber 3 and the respective chamber (working medium inlet chamber 5, working medium outlet chamber 6). This increases the area available for the valve sections 11, 12. The increased area of ​​the valve sections 11, 12 reduces the pressure losses. Due to the proposed shape, the working medium flowing into and out of the working chamber 3 does not pass directly through each other, as in the prior art. Flow separation is improved and unwanted heat transfer is avoided.

[0043] The working medium inlet chamber 5 and the working medium outlet chamber 6 are separated from each other by a separator 10 (shown in dotted lines) adjacent to the working chamber head 9. The separator 10 comprises an insulating layer, more particularly designed in the form of an air gap, arranged between the wall of the working medium inlet chamber 5 and the wall of the working medium outlet chamber 6, which also reduces heat losses. [Explanation of symbols]

[0044] 1 cylinder 2 Pistons 3 Working chamber 4 Valve gear 5. Working medium inlet chamber 6 Working medium outlet chamber 7 Medial side 8 Piston end face 9. Working chamber head 10 Separator 11 First valve section 12 Second valve section L Cylinder Longitudinal Axis

Claims

1. A piston compressor, more particularly a piston compressor for a heat pump, comprising a cylinder (1), a piston (2) mounted in said cylinder (1) for linear movement along a cylinder longitudinal axis (L), and a working chamber (3) formed in said cylinder (1), the volume of which is variable via piston movement, said working chamber (3) being fluidly connected to a working medium inlet chamber (5) by a first valve part (11) of a valve device (4) and to a working medium outlet chamber (6) by a second valve part (12) of said valve device (4), said working chamber (3) being fluidly connected to a working medium inlet chamber (5) by a first valve part (11) of a valve device (4) and to a working medium outlet chamber (6) by a second valve part (12) of said valve device (4), 1. A piston compressor, comprising: a chamber (3) bounded by an inner side (7) of the cylinder (1), a piston end face (8) formed at an end of the piston (2), and a working chamber head portion (9) arranged on the opposite side of the piston end face (8), the working chamber head portion (9) being formed by a geometric arrangement of first and second valve portions (11, 12), the first and second valve portions (11, 12) being arranged such that the working chamber (3) tapers towards the working chamber head portion (9).

2. 2. The piston compressor according to claim 1, wherein the first and second valve portions (11, 12) are each arranged at an angle other than 90° to the cylinder longitudinal axis (L).

3. 3. The piston compressor according to claim 1, wherein the first and second valve portions (11, 12) are arranged at angles offset relative to the cylinder longitudinal axis (L).

4. 3. The piston compressor according to claim 1, wherein the first and second valve portions (11, 12) are respectively arranged at the same angle with respect to the cylinder longitudinal axis (L).

5. 5. A piston compressor according to claim 1 or 4, characterized in that the working chamber head portion (9) terminates at an acute or obtuse angle relative to its cross section, said acute or obtuse angle straddling the first and second valve portions (11, 12).

6. 5. A piston compressor as claimed in claim 1 or 4, characterized in that the working chamber head portion (9) terminates at a right angle to its cross section, said right angle being straddled by the first and second valve portions (11, 12).

7. 7. The piston compressor according to claim 1, wherein the working chamber head portion (9) has a cross-sectional shape that is concave in a direction towards the working chamber (3).

8. 2. A piston compressor as claimed in claim 1, characterized in that the first and second valve portions (11, 12) are each arranged to provide a hemispherical shaped working chamber head portion (9).

9. A piston compressor according to any one of the preceding claims, characterized in that the piston end face (8) contours to the working chamber head portion (9).

10. 2. A piston compressor according to claim 1, characterized in that the working medium inlet chamber (5) and the working medium outlet chamber (6) are separated from each other by a separator (10) adjacent the working chamber head (9).

11. 11. A piston compressor according to claim 10, characterized in that the separator (10) comprises a thermal insulation layer designed in such a manner that it is arranged between the wall of the working medium inlet chamber (5) and the wall of the working medium outlet chamber (6).

12. A high temperature heat pump comprising a piston compressor designed according to any one of claims 1 to 11.