Vehicle with a heat pump circuit

Abstract

Vehicle with a heat pump circuit (1) which, viewed in one direction of flow of a refrigerant flowing therein, has the following components: • a refrigerant compressor (2), • a capacitor (5), • an expansive organ (9), • an external heat exchanger (10), and • an internal heat exchanger (8) which ◯ has a high-pressure side (7) which is arranged between the condenser (5) and the expansion element (9) and ◯ a low-pressure side (11) arranged between the external heat exchanger (10) and the refrigerant compressor (2), wherein • the high-pressure side (7) of the internal heat exchanger (8) is arranged between a collector (6) arranged after the condenser (5) and the expansion element (9), and • the expansion element (9) is an electrically controlled valve, characterized in that • the expansion device (9) is controlled in such a way that the refrigerant from the external heat exchanger (10) is only partially evaporated and • a subcooler (16) which can be switched on by means of a switching valve (15) is provided, by which the refrigerant can be subcooled in cooling operation.

Description

[0001] The present invention relates to a vehicle with a heat pump circuit according to the features of claim 1.

[0002] From DE 101 51 480 A1 a vehicle with a heat pump circuit with a refrigerant flowing therein is known, wherein the heat pump circuit has various components, such as an outdoor heat exchanger and an electrically controlled expansion valve.

[0003] The technical background of the invention includes DE 101 23 830 A1, US 2008 / 0229770 A1 and DE 199 25 744 A1.

[0004] Heat pump systems are being considered for heating the passenger compartment of electric vehicles because, unlike conventional vehicles with combustion engines, electric vehicles do not produce sufficient waste heat that can be used for heating the passenger compartment. A problem with heat pumps is that the output of the required heat source, outside air, is limited at temperatures below 0°C due to frost buildup or icing of the heat exchanger. As a result, the required heating output often cannot be achieved.

[0005] For heat pump applications, circuits have been proposed that feature a low-pressure collector and therefore do not guarantee a defined subcooling at the condenser. This means that the refrigerant's inlet enthalpy to an expansion valve cannot be controlled in such a way that a defined heat output from the ambient air heat source is sufficient for a given refrigerant mass flow rate. Consequently, depending on the available heat output, the refrigerant mass flow rate at the refrigerant compressor must be reduced, which results in a reduction of the heating capacity.

[0006] The object of the invention is therefore to create a vehicle with a suitable heat pump circuit that is suitable for heating a passenger compartment of the vehicle and provides sufficient heat output without absorbing so much heat from the environment that it leads to heavy frost buildup on the external heat exchanger.

[0007] This problem is solved by the features of claim 1. Advantageous embodiments and further developments of the invention can be found in the dependent claims.

[0008] The invention is based on a vehicle with a heat pump circuit which, viewed in the direction of flow of the refrigerant flowing therein, has a refrigerant compressor that draws in refrigerant, compresses it, and pumps the compressed refrigerant through a condenser. The vehicle can be a vehicle powered exclusively by one or more electric motors (electric vehicle) or a hybrid vehicle, i.e., a vehicle that has both an internal combustion engine and an electric motor.

[0009] In the condenser, heat contained in the refrigerant is released, for example, to the air flowing into the vehicle's passenger compartment. A (high-pressure) receiver is located after the condenser. This prevents the refrigerant from becoming supercooled in the condenser. The liquid refrigerant from the (high-pressure) receiver then flows through a high-pressure side of an internal heat exchanger and is subsequently expanded in an expansion chamber. The expanded refrigerant flows through an evaporator, where it absorbs heat from the surroundings. The refrigerant, now at a low pressure, then flows from the evaporator through a low-pressure side of the internal heat exchanger. From the low-pressure side of the internal heat exchanger, the refrigerant flows back to the suction side of the compressor.

[0010] The low-pressure heat exchanger allows heat to be transferred from the high-pressure side of the inner heat exchanger to the low-pressure side. This "subcools" the refrigerant before it expands. As a result, a higher enthalpy difference can be utilized during evaporation on the low-pressure side.

[0011] This allows the expansion valve to be controlled in such a way that, with the same heat absorption in the evaporator, the refrigerant is not completely evaporated at the evaporator outlet, meaning it still contains liquid. If this refrigerant were fed directly to the refrigerant compressor, it could be damaged by the liquid components. However, the internal heat exchanger evaporates the liquid component sufficiently to prevent this damage. This operating mode requires a higher refrigerant mass flow rate, allowing more refrigerant to be supplied to the compressor. This, in turn, enables the generation of greater heating capacity.

[0012] The (heat pump) cycle described above can also be operated as a cooling cycle. Even in cooling mode, the internal heat exchanger can be used to subcool the refrigerant after the condenser.

[0013] The arrangement of an internal heat exchanger in the heat pump circuit, as described above, can somewhat alleviate the critical (in the sense of "confined") installation space situation in or in front of the cooling module. In a hybrid vehicle, the so-called cooling module comprises an engine radiator for the combustion engine, possibly a turbocharger cooler, possibly a low-temperature cooler (e.g., for electrical components), and an external heat exchanger (in cooling mode, this is the condenser of the refrigeration circuit; in heat pump (heating) operation, it is the evaporator).

[0014] The additional heat required due to subcooling is not absorbed in the outer heat exchanger, but afterwards in the inner heat exchanger.

[0015] The invention will now be explained in more detail with reference to the drawing. The drawing shows: Fig. 1 a heat pump circuit for a vehicle according to the invention. Fig. 2 a heat pump circuit for a vehicle according to the invention with a switching function for air conditioning operation.

[0016] Fig. Figure 1 shows a heat pump circuit 1 with a compressor 2, which has a suction side 3 and a high-pressure side 4. Refrigerant compressed by the refrigerant compressor 2 is pumped through a condenser 5, where it releases heat, e.g., to an airflow blown into a passenger compartment of the vehicle. The heat transfer to the passenger compartment can occur, e.g., via another fluid circuit (e.g., a water-glycol circuit).

[0017] A high-pressure receiver 6 is located downstream of the condenser 5. Liquid refrigerant from the high-pressure receiver 6 is pumped through a high-pressure side 7 of an internal heat exchanger 8. After passing through the high-pressure side 7 of the internal heat exchanger 8, the refrigerant is expanded to a lower pressure in an expansion element 9, causing it to cool. Refrigerant from the expansion element 9 absorbs heat from the ambient air in an evaporator 10. Refrigerant from the evaporator 10 then flows through a low-pressure side 11 of the internal heat exchanger. Finally, refrigerant from the internal heat exchanger 8 is drawn in by the refrigerant compressor 2.

[0018] In the inner heat exchanger 8, heat is transferred from the high-pressure side 7 to the refrigerant flowing through the low-pressure side 11 of the inner heat exchanger 8. This causes the refrigerant to be supercooled on the high-pressure side before it expands in the expansion element 9. On the low-pressure side, the refrigerant, which may only be partially evaporated, is completely evaporated and then superheated.

[0019] Fig.Figure 2 shows a heat pump circuit for a vehicle according to the invention with a switching function for air conditioning operation. In air conditioning mode, the expansion valve 9 is completely closed. Refrigerant is expanded via the regulating expansion valve 12 and fed into the evaporator in the air conditioning unit, where it evaporates and cools the air flowing into the passenger compartment. The evaporated refrigerant is superheated in the internal heat exchanger 8 and fed to the compressor 2, where it is compressed. The compressed refrigerant condenses in the condenser 5, which releases its heat to a water-glycol circuit, where the heat is transferred to the outside air via a heat exchanger. In air conditioning mode, a (switching) valve 15 is configured so that the refrigerant can be subcooled in a water / glycol-cooled heat exchanger 16. The refrigerant is then fed to the expansion valve 12 via the internal heat exchanger 8.

Claims

[1] Vehicle with a heat pump circuit (1) which, viewed in one direction of flow of a refrigerant flowing therein, comprises the following components: • a refrigerant compressor (2), • a capacitor (5), • an expansive organ (9), • an external heat exchanger (10), and • an internal heat exchanger (8) which ◯ has a high-pressure side (7) which is arranged between the condenser (5) and the expansion element (9) and ◯ a low-pressure side (11) arranged between the external heat exchanger (10) and the refrigerant compressor (2), wherein • the high-pressure side (7) of the internal heat exchanger (8) is arranged between a collector (6) arranged after the condenser (5) and the expansion element (9), and • the expansion element (9) is an electrically controlled valve, characterized by , that • the expansion device (9) is controlled in such a way that the refrigerant from the external heat exchanger (10) is only partially evaporated and • a subcooler (16) which can be switched on by means of a switching valve (15) is provided, by which the refrigerant can be subcooled in cooling operation. [2] Vehicle according to claim 1, characterized by , that the condenser (5) is intended to transfer heat to air flowing into a passenger compartment of the vehicle. [3] Vehicle according to one of claims 1 or 2, characterized by , that the condenser (5) is thermally coupled to a fluid circuit, in particular a water-glycol circuit, through which heat is released. [4] Vehicle according to any one of claims 1 to 3, characterized by that the fluid circuit, in particular a water-glycol circuit, is designed to transfer heat to air flowing into a passenger compartment of the vehicle by means of a heat exchanger. [5] Vehicle according to any of the preceding claims, characterized by , that the internal heat exchanger (8) is designed such that the superheat at the compressor inlet does not exceed a certain value. [6] Vehicle according to any of the preceding claims, characterized by , that the expansion valve (9) is regulated in such a way that a certain superheat of the refrigerant is achieved at the inlet (3) of the refrigerant compressor (2). [7] Vehicle according to any of the preceding claims, characterized by that the vehicle is a vehicle powered exclusively by one or more electric motors or a hybrid vehicle.

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