Heat pump and method for operating same

Abstract

The invention relates to a heat pump (1) comprising a working-fluid circuit having an evaporator (2) which forms a liquid-receiving volume (13) in the bottom region and a vapour-receiving volume (14) in the top region, a compressor (3) adjoining the evaporator (2), a condenser (4) adjoining the compressor (3), and an expansion unit (6) adjoining the condenser (4), which expansion unit is connected to the evaporator (2), characterised in that a line (11, 12) connecting the expansion unit (6) to the evaporator (2) is routed through the vapour-receiving volume (14) of the evaporator before opening in the evaporator (2). The invention further relates to a method for operating a heat pump (1) of this kind.

Description

[0001] Description

[0002] Heat pump and method for operating such a heat pump

[0003] The invention relates to a heat pump comprising a working fluid circuit having an evaporator which forms a liquid absorption volume in the lower region and a vapor absorption volume in the upper region, a compressor connected to the evaporator, a condenser connected to the compressor, and an expansion tank connected to the condenser and connected to the evaporator, wherein throttle valves are provided in lines which connect the condenser to the expansion tank and the expansion tank to the evaporator. The invention further relates to a method for operating such a heat pump.

[0004] Heat pumps of the type mentioned above are known in the art in a wide variety of designs. They comprise a working fluid circuit which has an evaporator, a compressor, a condenser and an expansion unit as its main components. In the evaporator, the working fluid is heated by an external heat source and evaporated. It is then fed to the compressor where it is brought to a higher pressure level. The working fluid is then condensed in the condenser at a condensation temperature which is higher than the evaporation temperature. In order to return the working fluid to its original state at the end of the circuit, it is expanded in the expansion unit, which lowers its temperature again. Within the evaporator, small liquid droplets can be entrained with the vapor flow generated therein and fed to the compressor.If the droplets are too large, they can cause damage to the compressor. To prevent such damage, it has been proposed to install a demister in the vapor receiving volume of the evaporator. This demister separates the droplets from the vapor mass flow, whereupon they drip back into the liquid receiving volume of the evaporator.

[0005] Based on this prior art, it is an object of the present invention to provide a heat pump of the type mentioned at the outset with an alternative structure and an alternative method for operating such a heat pump.

[0006] To achieve this object, the present invention creates a heat pump comprising a working fluid circuit having an evaporator which forms a liquid absorption volume in the lower region and a vapor absorption volume in the upper region, a compressor connected to the evaporator, a condenser connected to the compressor and an expansion unit connected to the condenser and connected to the evaporator, characterized in that a line connecting the expansion unit to the evaporator is led through the vapor absorption volume of the evaporator before it opens into the evaporator. Thanks to such a structure, the working fluid led from the expansion unit to the evaporator can be used to superheat vapor contained in the vapor absorption volume of the evaporator, as a result of which droplets contained in the vapor are evaporated and cannot reach the compressor.The heat pump according to the invention is distinguished, on the one hand, by the fact that the installation of a demister in the evaporator can be completely dispensed with. On the other hand, the coefficient of performance (COP) of the heat pump can be improved by approximately 5 to 7%, since additional heat is extracted from the working fluid, which previously only expanded on its way from the expansion unit to the evaporator.

[0007] Preferably, the line which connects the expansion unit to the evaporator is designed as a bundle of lines or as a meandering line in the area which is guided through the vapor absorption volume of the evaporator in order to release heat to the vaporous working fluid as evenly and / or over a large area as possible.

[0008] According to one embodiment of the present invention, the expansion unit has a throttle valve, an expansion tank arranged downstream of the throttle valve, which forms a liquid receiving volume and a vapor receiving volume, and a further throttle valve arranged downstream of the expansion tank. Accordingly, the pressure of the condensed working fluid coming from the condenser can initially be reduced by means of the first throttle valve to a first pressure level, at which it is stored in the expansion tank in both liquid and gaseous form. Using the further throttle valve, the pressure can then be reduced to a second pressure level before the working fluid enters the evaporator.

[0009] Advantageously, a demister is positioned in the vapor holding volume of the expansion tank, and above the demister, a line connecting the expansion tank to the compressor leads out of the expansion tank. Accordingly, the vaporous working fluid contained in the expansion tank can be directed directly to the compressor without having to pass through the evaporator, thereby improving the heat pump's coefficient of performance.

[0010] Preferably, the vapor storage volume of the evaporator and the condenser are connected via a bypass line equipped with a bypass valve. Accordingly, the compressor can be bypassed if necessary.

[0011] Furthermore, to achieve the object mentioned at the outset, the present invention provides a method for operating a heat pump, in particular a heat pump according to the invention in which a working fluid circulates, characterized in that working fluid vapor present within a vapor absorption volume of an evaporator of the heat pump is superheated by heat exchange with working fluid condensate conducted from an expansion unit of the heat pump to the evaporator, before it is conducted to a compressor of the heat pump.

[0012] Further features and advantages of the present invention will become clear from the following description with reference to the accompanying Figure 1, which shows a schematic view of a heat pump according to an embodiment of the present invention.

[0013] : The same reference numbers designate the same or similar components below. The heat pump 1 shown in the drawing comprises a working fluid circuit having an evaporator 2, a compressor 3, a condenser 4, a subcooler 5 (which is basically optional) and an expansion unit 6, which are connected to one another by corresponding lines 7, 8, 9, 10, 11 and 12. The evaporator 2 forms a liquid holding volume 13 in the lower area, into which the line 12 opens, and a vapor holding volume 14 in the upper area, at the upper end of which the line 7 leads out of the evaporator 2. Pipes 15 are positioned in the liquid holding volume 13, through which a warm medium from an external heat source is conducted, the medium being supplied via a line 16 and discharged via a line 17.In the vapor absorption volume 14 of the evaporator 2 there is in this case a pipe bundle 18 positioned which connects the pipes 11 and 12 to one another and through which the working fluid circulating in the working fluid circuit is conducted during operation of the heat pump 1, as will be explained in more detail below. The pipes 11 and 12 as well as the pipe bundle 18 can, for example, also be replaced by a single pipe which extends meandering through the vapor absorption volume 14 of the evaporator 2, even if this is not shown here. The compressor 3, which in the embodiment shown is driven by an electric motor 19, has in the embodiment shown two compressor stages 20 and 21 which the working fluid passes through one after the other.However, it should be clear that in principle the use of a single-stage compressor is also possible, as is the use of a compressor having more than two compressor stages. In the present case, pipes 22 extend through the condenser 4 and the subcooler 5, through which pipes a medium to be heated via the heat pump 1 is passed, wherein the medium in this case is first fed to the subcooler 5 via a line 23, then out of the subcooler 5 via a line 24 and fed to the condenser 4 and finally discharged from the condenser 4 via a line 25. In the embodiment shown, the expansion unit 6 comprises a throttle valve 26, an expansion tank 27 arranged downstream of the throttle valve 26, which forms a liquid holding volume 28 and a vapor holding volume 29, and a further throttle valve 30 arranged downstream of the expansion tank 27.The throttle valve 26 is present in line 10 and the throttle valve.

[0014] 30 in the line 12. The line 10 opens into the steam receiving volume 29 and the line 11 is connected to the liquid receiving volume 28. A demister 31 is positioned in the steam receiving volume 29 of the expansion tank 27 and above the demister

[0015] 31 leads a line 32 connecting the expansion tank 27 to the compressor 3 out of the expansion tank 27. Furthermore, in the illustrated embodiment, the vapor receiving volume 14 of the evaporator 2 and the condenser 4 are connected to one another via a bypass line 34 provided with a bypass valve 33.

[0016] During operation of the heat pump 1, the working fluid circulating in the working fluid circuit of the heat pump 1, which is normally a refrigerant, is first heated in the evaporator 2 by heat exchange with a warm medium coming from an external heat source, which is fed to the evaporator 2 via the line 16, then passed through the pipes 15 arranged in the liquid holding volume 13 of the evaporator 2 and then discharged from the evaporator 2 again through the line 17. The working fluid evaporates and rises into the vapor holding volume 14 of the evaporator 2, where it is superheated by liquid working fluid which is passed through the pipe bundle 18 positioned in the vapor holding volume 14. This superheating removes all liquid particles contained in the vaporous working fluid.The pure steam is then passed through line 7 to the compressor 3, where it is compressed in two stages and then, still in a vapor state, is fed via line 8 to the condenser 4. Inside the condenser 4, the steam is condensed by heat exchange with a medium to be heated, which is passed through the tubes 22 arranged in the condenser 4. The working fluid leaves the condenser 4 via line 9 in the liquid state and is fed to the subcooler 5, where the temperature of the working fluid is further reduced by heat exchange with the medium to be heated. The working fluid leaves the subcooler 5 via line 10, is throttled via the throttle valve 26 and then fed to the expansion tank 27 in a two-phase state. The liquid phase collects in the liquid holding volume 28 of the expansion tank 27 and the vapor phase collects in the vapor holding volume 29 of the expansion tank 27.The vaporous working fluid passes through the demister 31 and is fed directly back to the compressor 3 via line 32. The liquid working fluid is fed via line 11 into the tube bundle 18 arranged in the vapor receiving volume 14 of the evaporator 2, leaves the evaporator 2 in the liquid state via line 12, whereupon it is throttled again using the throttle valve 30 and finally fed to the liquid receiving volume 13 of the evaporator 2. Optionally, the vaporous working fluid from the vapor receiving volume 14 of the evaporator 2 can also be fed directly to the condenser 4 via the bypass line 34. Although the invention has been illustrated and described in detail by means of the preferred embodiment, the invention is not limited by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention.

[0017] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identity are included.

Claims

Patent claims 1. Heat pump (1) comprising a working fluid circuit having an evaporator (2) which forms a liquid absorption volume (13) in the lower region and a vapor absorption volume (14) in the upper region, a compressor (3) connected to the evaporator (2), a condenser (4) connected to the compressor (3) and an expansion unit (6) connected to the condenser (4) and connected to the evaporator (2), characterized in that a line (11, 12) connecting the expansion unit (6) to the evaporator (2) is guided through the vapor absorption volume (14) of the evaporator (2) before it opens into the evaporator (2).

2. Heat pump (1) according to claim 1, characterized in that a line (11, 12) connecting the expansion unit (6) to the evaporator (2) is designed as a bundle of lines (18) or as a meandering line in the area which is guided through the steam absorption volume (14) of the evaporator (2).

3. Heat pump (1) according to claim 1 or 2, characterized in that the expansion unit (6) has a throttle valve (26), an expansion tank (27) arranged downstream of the throttle valve (26), which forms a liquid receiving volume (28) and a vapor receiving volume (29), and a further throttle valve (30) arranged downstream of the expansion tank (6).

4. Heat pump (1) according to claim 3, characterized in that a demister (31) is positioned in the steam receiving volume (29) of the expansion tank (27) and above the demister (31) a line (32) connecting the expansion tank (27) to the compressor (3) leads out of the expansion tank (27).

5. Heat pump (1) according to one of the preceding claims, characterized in that the vapor absorption volume (14) of the evaporator (2) and the condenser (4) are connected to one another via a bypass line (34) provided with a bypass valve (33).

6. Method for operating a heat pump (1), in particular a heat pump according to one of the preceding claims, in which a working fluid circulates, characterized in that working fluid vapor present within a vapor receiving volume (14) of an evaporator (2) of the heat pump (1) is superheated by heat exchange with working fluid condensate conducted from an expansion unit (6) of the heat pump to the evaporator (2) before it is conducted to a compressor (3) of the heat pump (1).

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