DE102019203293A1 - Method for operating a refrigeration system for a vehicle with a refrigerant circuit having a heat pump function - Google Patents

Abstract

The invention relates to a method for operating a refrigeration system (10) for a vehicle with a refrigerant circuit (1) having a heat pump function, in which the external heat exchanger (5) with a heating condenser (8) is used to defrost an external heat exchanger (5) after a heat pump operation. or hot gas cooler (8) is connected to the high pressure level generated by the refrigerant compressor (4) and the refrigerant emerging from the external heat exchanger (5) is expanded to a low pressure by means of a defrosting expansion device (AE, AE5) and fed to the refrigerant compressor (4) on the inlet side becomes.

Description

The invention relates to a method for operating a refrigeration system for a vehicle with a refrigerant circuit having a heat pump function.

Such refrigeration systems are known which can be operated both in a heat pump mode for heating a vehicle interior and in a refrigeration system mode for cooling the vehicle interior. In heat pump mode, the supply air that is supplied to the vehicle interior is conditioned and heated using the heat provided by the heat pump.

When using the ambient air as a heat source, an external heat exchanger of a refrigerant circuit is used together with a heat pump expansion element as a heat pump evaporator. On the one hand, heat is withdrawn from the ambient air and the refrigerant in the external heat exchanger evaporates and possibly also heated or overheated and on the other hand the external heat exchanger is cooled on its outside due to the evaporation temperature level in the refrigerant. As a result of this cooling of the external heat exchanger, the evaporation temperature, which is below the ambient temperature, can lead to frosting and ultimately icing of the heat exchanger, as moisture bound in the ambient air is deposited as condensate on the surface of the external heat exchanger. Depending on the weather situation, moisture can hit the surface of the external heat exchanger directly and freeze.

Due to increasing frost and icing on the surface of the external heat exchanger, the potential for evaporation of refrigerant decreases and thus the heating output also decreases, as the heat-transferring surface and thus the potential of the refrigerant to absorb heat decreases over the operating time of the heat pump operation.

A refrigeration system with a refrigerant circuit for performing a heat pump operation and a defrosting operation is from the FR 3 025 299 A1 known. In addition to a 2-part external heat exchanger, this refrigerant circuit includes a 2-stage refrigerant compressor with which an intermediate pressure level is generated in addition to a high pressure level. In a heat pump operation, the refrigerant, which is compressed to high pressure, is expanded into a series circuit of the two sections of the outer heat exchanger via a heating register and a heat pump expansion element.

To carry out a first defrosting operation, a first section of the external heat exchanger is connected to a first stage of the refrigerant compressor, so that this first section is subjected to the intermediate pressure level and thus heated, while the heat pump operation is continued by means of the second section of the external heat exchanger, and this second stage Section is connected to the high pressure outlet of the refrigerant compressor via an expansion element. In this mode of operation, the external heat exchanger is partially defrosted by means of the first section

To carry out a second defrosting operation, the second section of the external heat exchanger is connected to the high pressure outlet of the refrigerant compressor evaporator via the heat pump expansion element and a heating register, the heat pump expansion element being fully open. The refrigerant flowing out of the second section of the external heat exchanger is expanded into the first section of the external heat exchanger by means of a further expansion element and then fed to the inlet side of the refrigerant compressor. In this mode of operation, the second section of the external heat exchanger is defrosted.

From the DE 10 2007 028 252 A1 a refrigerant circuit with two evaporators and an ejector pump is known, which functions as a refrigerant decompression device and a refrigerant circulation device. If frost formation occurs in one of the two evaporators during operation of the refrigeration system, the ejector pump is shut down so that a high-temperature refrigerant discharged by the refrigerant compressor flows through a bypass duct section and a duct section branching off from the same, so that the hot-gas refrigerant is introduced into both evaporators and thereby the same defrosted.

The US 2014/0020415 A1 describes a method for operating a device for heat distribution in a hybrid vehicle. This device has an engine cooling circuit and a refrigerant circuit designed for combined operation in refrigeration system and heat pump mode as well as for a reheating mode with an evaporator, a compressor, a heat exchanger for supplying heat from the refrigerant to the air to be conditioned for a vehicle interior and with a heat exchanger for heat transfer between the refrigerant of the refrigerant circuit and the coolant of the engine cooling circuit. This heat exchanger is on the one hand as a heat pump evaporator for heat transfer from the coolant to the refrigerant and on the other hand as a condenser for heat transfer from the refrigerant to the Coolant operable. In heat pump mode, after flowing through a heat exchanger that absorbs the thermal energy of the internal combustion engine or the ambient air, the refrigerant is passed via a bypass line past the evaporator and an internal heat exchanger to the compressor of the refrigerant circuit. If the internal combustion engine is used as a heat source in heat pump mode, the heat exchanger of the coolant circuit that absorbs heat energy from the ambient air is bypassed by means of a bypass line so that no heat energy can be absorbed from the ambient air.

The object of the invention is to provide a method for operating a refrigeration system for a vehicle with a refrigerant circuit having a heat pump function, with which an improved and, in particular, more efficient operation can be implemented with regard to a defrosting operation.

This object is achieved by a method with the features of claim 1.

• - einem Kältemittelverdichter mit einem Hochdruckausgang und einer Eintrittsseite,
• - einem äußeren Wärmeübertrager, welcher entweder zur Durchführung eines Kälteanlagenbetriebs als Kondensator oder Gaskühler oder zur Durchführung eines Wärmepumpenbetriebs als Wärmepumpen-Verdampfer mittels eines Wärmepumpen-Expansionsorgans betreibbar ist und mit dem Hochdruckausgang des Kältemittelverdichters verbindbar ist,
• - einem Verdampferzweig mit einem Verdampfer und einem Verdampfer-Expansionsorgan, wobei der Verdampferzweig niederdruckseitig mit der Eintrittsseite des Kältemittelverdichters und hochdruckseitig mit dem äußeren Wärmeübertrager verbindbar ist, und
• - einem Heizzweig mit einem einen Zuluftstrom für den Fahrzeuginnenraum direkt oder indirekt erwärmenden Heizkondensator oder Heizgaskühler, wobei der Heizzweig zur Durchführung eines Wärmepumpenbetriebs stromaufwärts mit dem Hochdruckausgang des Kältemittelverdichters und stromabwärts mit dem Wärmepumpen-Expansionsorgan verbindbar ist, und wobei zum Abtauen des äußeren Wärmeübertragers nach einem Wärmepumpenbetrieb
• - der äußere Wärmeübertrager mit dem Heizkondensator oder Heizgaskühler auf dem von dem Kältemittelverdichter erzeugten Hochdruckniveau oder auf einem gegenüber dem Hochdruck niedrigeren Mitteldruck verbunden wird, und
• - das aus dem äußeren Wärmeübertrager austretende Kältemittel mittels eines Abtau-Expansionsorgans auf einen Niederdruck entspannt und dem Kältemittelverdichter eintrittsseitig zugeführt wird.

In this method for operating a refrigeration system for a vehicle with a refrigerant circuit having a heat pump function with the following components:

• - a refrigerant compressor with a high pressure outlet and an inlet side,
• - an external heat exchanger, which can be operated either as a condenser or gas cooler or to operate a heat pump as a heat pump evaporator by means of a heat pump expansion element and can be connected to the high pressure outlet of the refrigerant compressor,
• - An evaporator branch with an evaporator and an evaporator expansion element, wherein the evaporator branch can be connected on the low-pressure side to the inlet side of the refrigerant compressor and on the high-pressure side to the external heat exchanger, and
• - A heating branch with a supply air flow for the vehicle interior directly or indirectly heating heating condenser or heating gas cooler, the heating branch being connectable upstream to the high pressure outlet of the refrigerant compressor and downstream to the heat pump expansion element for performing a heat pump operation, and wherein for defrosting the external heat exchanger after a Heat pump operation
• - The external heat exchanger is connected to the heating condenser or heating gas cooler at the high pressure level generated by the refrigerant compressor or at a mean pressure lower than the high pressure, and
• - The refrigerant emerging from the external heat exchanger is expanded to a low pressure by means of a defrosting expansion device and is supplied to the refrigerant compressor on the inlet side.

With this method, the heating condenser or heating gas cooler remains active when switching from air / heat pump operation to defrosting operation, so that part of the heat flow continues to be transferred to the supply air flow directed into the vehicle interior. The external heat exchanger to be de-iced is exposed to moderately tempered waste heat from the refrigerant exiting the heating register, for example, and thus the continuation of the heating operation via the refrigerant circuit is ensured. In addition, there is no high temperature stress on the external heat exchanger in contrast to its direct exposure to hot gas from the refrigerant compressor, which can ultimately also result in a switchover of the refrigerant flow direction.

A defrosting operation is carried out when the heating power drops due to a falling evaporation potential at the external heat exchanger. This state can be detected on the basis of various variables, such as, for example, the absorbed compressor power and / or the high pressure at the outlet of the refrigerant compressor.

• - das Abtau-Expansionsorgan in einem Abtau-Zweig angeordnet, mit welchem der äußere Wärmeübertrager mit der Eintrittsseite des Kältemittelverdichters zur Durchführung des Abtaubetriebs verbunden wird,
• - zur Durchführung des Abtaubetriebs der äußere Wärmeübertrager mit dem Heizkondensator oder Heizgaskühler über das Wärmepumpen-Expansionsorgan verbunden, wobei das Wärmepumpen-Expansionsorgan entweder in einen geöffneten Zustand gesteuert oder derart gesteuert wird, dass der äußere Wärmeübertrager auf einem gegenüber dem Hochdruck niedrigeren Mitteldruck arbeitet, und
• - mittels des Abtau-Expansionsorgans das Kältemittel auf Niederdruck entspannt.

According to an advantageous development of the invention

• - The defrosting expansion element is arranged in a defrosting branch, with which the external heat exchanger is connected to the inlet side of the refrigerant compressor in order to carry out the defrosting operation,
• - To carry out the defrosting operation, the external heat exchanger is connected to the heating condenser or heating gas cooler via the heat pump expansion element, the heat pump expansion element being either controlled in an open state or controlled in such a way that the external heat exchanger operates at a mean pressure lower than the high pressure, and
• - The refrigerant is expanded to low pressure by means of the defrost expansion element.

In this method according to the invention, the defrosting process and the connected and continued indoor air conditioning work on the basis of a triangular process. There is no additional heat source, apart from the heat introduced by the compressor side, is used.

Furthermore, in this method according to the invention, when changing from heat pump operation to defrosting operation, the main flow path of the refrigerant remains unchanged, with only the opening cross-sections of expansion elements having to be changed. The heat pump expansion element is fully opened. It is also possible to throttle the refrigerant only slightly with this heat pump expansion element, so that the external heat exchanger is operated at a lower pressure level, a so-called medium pressure level, also called intermediate pressure level, and thus at a temperature level at which a temperature shock risk is greatly reduced and at which the refrigerant flows through the heat exchanger at a temperature level above the freezing point of water.

• - der Kältemittelkreislauf mit einem einen Chiller und ein Chiller-Expansionsorgan aufweisenden Chillerzweig ausgebildet wird, welcher parallel mit dem Verdampferzweig verbindbar ist,
• - zur Durchführung eines Reheat-Betriebs mittels eines ein Reheat-Expansionsorgan aufweisenden Reheat-Zweiges der Heizkondensator oder Heizgaskühler stromabwärts mit dem äußeren Wärmeübertrager verbunden wird,
• - zur Durchführung des Abtaubetriebs der Reheat-Betrieb durchgeführt wird, wobei das Reheat-Expansionsorgan entweder in einen geöffneten Zustand gesteuert oder derart gesteuert wird, dass der äußere Wärmeübertrager auf einem gegenüber dem Hochdruck niedrigeren Mitteldruck arbeitet, und
• - mittels des Chiller-Expansionsorgans als Abtau-Expansionsorgan das Kältemittel auf Niederdruck entspannt wird.

According to another advantageous embodiment of the invention it is provided that

• - The refrigerant circuit is designed with a chiller branch having a chiller and a chiller expansion element, which can be connected in parallel to the evaporator branch,
• - To carry out a reheat operation by means of a reheat branch having a reheat expansion element, the heating condenser or heating gas cooler is connected downstream to the external heat exchanger,
• - To carry out the defrost operation, the reheat operation is carried out, the reheat expansion element either being controlled into an open state or controlled in such a way that the external heat exchanger operates at a mean pressure lower than the high pressure, and
• - The refrigerant is expanded to low pressure by means of the chiller expansion device as a defrosting expansion device.

When the reheat expansion element is open, an identical pressure level is set in the external heat exchanger as in the heating condenser or hot gas cooler or, when the reheat expansion element is throttled, a third pressure level is set between the high pressure level in the heating condenser or hot gas cooler and the low pressure level in the chiller.

In this inventive development of the invention, the refrigerant from the heating condenser or heating gas cooler is fed to the external heat exchanger via a reheat branch with a reheat expansion element, and the refrigerant exiting the external heat exchanger is fed to the chiller branch before being returned to the inlet side of the refrigerant compressor. The chiller expansion device takes over the pressure reduction to low pressure when the coolant circuit of the chiller is stopped. It is also possible to carry out this defrosting operation as a cycle process with flowing coolant in the chiller, so that a further heat source is activated for defrosting, which means that additional electrical power may no longer be required or reduced.

Furthermore, this defrosting process and the associated and continued indoor air conditioning work either in a triangular process in which no additional heat source is used except for the heat introduced on the compressor side, or alternatively on the basis of a cycle process with a water heat pump process implemented by means of the chiller. In addition to the heat introduced on the compressor side, the heat bound in the cooling medium of the chiller is also used.

Since the external heat exchanger is flowed through in the same direction as in the refrigeration system operation, only slight flow and pressure losses occur.

• - der äußere Wärmeübertrager zur Durchströmung mit Außenluft mit einer steuerbaren Anordnung ausgebildet, wobei mittels dieser Anordnung zumindest ein Teil der Oberfläche des äußeren Wärmeübertragers für die Luftdurchströmung verschließbar ist, und
• - zur Durchführung des Abtaubetriebs die Anordnung vollständig verschlossen.

According to a particularly advantageous development of the invention

• the external heat exchanger is designed with a controllable arrangement for the flow of outside air, with at least part of the surface of the external heat exchanger being closable for the air flow by means of this arrangement, and
• - To carry out the defrosting operation, the arrangement is completely closed.

With such an arrangement, for example an air flap arrangement or a louvre arrangement, it is prevented that the defrosting process actually takes place in the event of a cold air flow at a correspondingly required and high or medium pressure situation, the icing does not start again immediately or the defrosting process is prolonged. Particularly for the start of the defrosting process, it must be ensured that a condensation pressure is established in the external heat exchanger, the corresponding condensation temperature of which is at least 1 ° C and is thus just above the freezing point of water at 0 ° C, in order to actually cover the layer of frost and ice to dissolve b.

According to a further preferred development of the invention, the defrosting operation is ended when the outlet temperature of the refrigerant emerging from the external heat exchanger has reached a predetermined positive temperature threshold value reached, which is, for example. 3 ° C. This outlet temperature should be set to a value of 3 ° C, for example, in a stable manner over the long term.

It is also particularly advantageous if, according to a further development, in order to carry out the defrosting operation, the pressure value in the external heat exchanger by means of the air heat pump or reheat expansion element in cooperation with the defrosting expansion element or the chiller expansion element is set to a condensation pressure which has a condensation temperature greater than 0 ° C corresponds to.

Furthermore, it is particularly advantageous if a pressure / temperature sensor is used to set and monitor the mean pressure for the AC and heat pump branch with the external heat exchanger and the defrosting expansion element in order to maintain a condensation pressure level in the refrigerant above the freezing point of water at 0 ° C to obtain. Here, instead of a combination sensor consisting of a pressure and temperature sensor, individual sensors can also be used.

In a corresponding manner, it is also particularly advantageous if a pressure / temperature sensor is used to monitor the setting of the mean pressure for the reheat branch with the external heat exchanger up to the chiller expansion element as a defrosting expansion element in order to establish a condensation pressure level in the refrigerant above the freezing point of water to be achieved with 0 ° C. Here, instead of a combination sensor consisting of a pressure and temperature sensor, individual sensors can also be used.

If during the defrosting process, despite the active heat pump system, there is a loss of comfort in the interior air conditioning, an electrical heating element can be used to cover a heating deficit.

Finally, according to a particularly preferred development, it is advantageous if, after the end of the defrosting operation, the liquid condensate generated on the outer heat exchanger is expelled by means of a fan arrangement assigned to the outer heat exchanger.

• 1 ein Schaltbild einer Kälteanlage zur Erläuterung eines ersten Ausführungsbeispiels des erfindungsgemäßen Verfahrens, und
• 2 ein Schaltbild einer Kälteanlage zur Erläuterung eines zweiten Ausführungsbeispiels des erfindungsgemäßen Verfahrens.

Further advantages and details of the invention emerge from the following description of preferred embodiments and with reference to the drawings. Show:

• 1 a circuit diagram of a refrigeration system to explain a first embodiment of the method according to the invention, and
• 2 a circuit diagram of a refrigeration system to explain a second embodiment of the method according to the invention.

Before explaining the exemplary embodiments of the method according to the invention with reference to the refrigeration systems 10 according to the 1 and 2 these are initially described together due to their same basic structure.

The refrigerant circuit 1 the refrigeration system 10 according to 1 and 2 can be operated both in a refrigeration system or cooling operation (called AC operation for short) and in a heat pump mode and has two evaporators, namely one evaporator 2 and a chiller 3 , which with a coolant circuit 3.0 is thermally coupled for cooling, e.g. a high-voltage battery.

• - einem Kältemittelverdichter 4,
• - einem als Kondensator oder Gaskühler ausgebildeten äußeren Wärmeübertrager 5 mit einem demselben in seiner Funktion als Wärmepumpenverdampfer für den Heizbetrieb zugeordneten Wärmepumpen-Expansionsorgan AE3,
• - einem inneren Wärmeübertrager 6,
• - einem niederdruckseitigen Akkumulator 7,
• - einem Innenraum-Verdampferzweig 2.1 mit dem als Frontverdampfer ausgebildeten Verdampfer 2 und einem vorgeschalteten Verdampfer-Expansionsorgan AE2,
• - einem dem Verdampfer 2 nachgeschalteten Rückschlagventil R1, welches über den Akkumulator 7 und den niederdruckseitigen Abschnitt des inneren Wärmeübertragers 6 mit der Eintrittsseite des Kältemittelverdichters 4 fluidverbunden ist,
• - einem Chiller-Zweig 3.1 mit dem Chiller 3, einem diesem vorgeschalteten Chiller-Expansionsorgan AE1, wobei der Chiller 3 neben der Kühlung bspw. einer elektrischen Komponente des Fahrzeugs auch zur Realisierung einer Wasser-Wärmepumpenfunktion unter Nutzung der Abwärme mindestens einer elektrischen Komponente eingesetzt wird,
• - einem AC- und Wärmepumpenzweig 5.1 mit dem äußeren Wärmeübertrager 5 und dem Wärmepumpen-Expansionsorgan AE3, wobei im Heizbetrieb der AC- und Wärmepumpenzweig 5.1 stromaufwärts über das Wärmepumpen-Expansionsorgan AE3 mit dem Innenraum-Verdampferzweig 2.1 unter Bildung eines ersten Abzweigpunktes Ab1 fluidverbindbar ist und stromabwärts über ein Abtau-Expansionsorgan AE5 gemäß 1 oder über ein Absperrorgan A2 gemäß 2 mit der Eintrittsseite des Kältemittelverdichters 4 fluidverbindbar ist, während im AC-Betrieb der AC- und Wärmepumpenzweig 5.1 stromaufwärts über ein Absperrorgan A4 mit dem Hochdruckausgang des Kältemittelverdichters 4 fluidverbindbar ist,
• - einem Heizzweig 8.1 mit einem einen Zuluftstrom L für den Fahrzeuginnenraum direkt oder indirekt erwärmenden Heizkondensator 8 oder Heizgaskühler 8, wobei der Heizzweig 8.1 stromaufwärts über ein Absperrorgan A3 mit dem Hochdruckausgang des Kältemittelverdichters 4 fluidverbindbar ist und stromabwärts über ein Absperrorgan A1 mit dem ersten Abzweigpunkt Ab1 und damit mit dem Innenraum-Verdampferzweig 2.1 fluidverbindbar ist,
• - einem Reheat-Zweig 5.2 mit einem als Expansionsventil ausgebildeten Reheat-Expansionsorgan AE4, wobei der Reheat-Zweig 5.2 stromabwärts mit dem äußeren Wärmeübertrager 5 unter Bildung eines zweiten Abzweigpunktes Ab2 und stromaufwärts mit dem Heizkondensator 8 oder Heizgaskühler 8 fluidverbunden ist,
• - einem Abtau-Zweig 5.4 mit einem absperrbaren Abtau-Expansionsorgan AE5 und einem Rückschlagventil R2 gemäß 1, wobei der Abtau-Zweig 5.4 stromaufwärts über den zweiten Abzweigpunkt Ab2 mit dem äußeren Wärmeübertrager 5 und stromabwärts mit dem Akkumulator 7 fluidverbindbar ist,
• - einem Wärmepumpenrückführzweig 5.4 mit einem Absperrorgan A2 und einem Rückschlagventil R2 gemäß 2, wobei der Wärmepumpenrückführzweig 5.4 stromaufwärts über den zweiten Abzweigpunkt Ab2 mit dem äußeren Wärmeübertrager 5 und stromabwärts mit dem Akkumulator 7 fluidverbindbar ist,
• - einem Absaugzweig 5.5 mit einem Absperrorgan A5, wobei der Absaugzweig 5.5 stromaufwärts mit dem Heizkondensator 8 oder Heizgaskühler 8 und stromabwärts über einen dritten Abzweigpunkt Ab3 mit dem Abtau-Expansionsorgan AE5 (vgl. 1) bzw. mit dem Absperrorgan A2 (vgl. 2) und dem Rückschlagventil R2 des Abtau-Zweiges 5.3 (vgl. 1) bzw. des Wärmepumpenrückführzweiges 5.4 (vgl. 2) fluidverbunden ist, und
• - einem bspw. als Hochvolt-PTC-Heizelement ausgeführten elektrischen Heizelement 9 als Zuheizer für einen in den Fahrzeuginnenraum geführten Zuluftstrom L, welches sich zusammen mit dem Heizkondensators 8 oder Heizgaskühler 8 und dem Verdampfer 2 in einem Klimagerät 1.1 befindet und dem Heizkondensators 8 oder Heizgaskühler 8 und damit auch dem Verdampfer 2 luftseitig nachgeschaltet ist.

The refrigerant circuit 1 according to 1 and 2 consists of the following components:

• - a refrigerant compressor 4th ,
• - an external heat exchanger designed as a condenser or gas cooler 5 with a heat pump expansion element assigned to the same in its function as a heat pump evaporator for heating operation AE3 ,
• - an internal heat exchanger 6th ,
• - an accumulator on the low pressure side 7th ,
• - an interior evaporator branch 2.1 with the evaporator designed as a front evaporator 2 and an upstream evaporator expansion device AE2 ,
• - one of the vaporizers 2 downstream check valve R1 , which is about the accumulator 7th and the section of the internal heat exchanger on the low-pressure side 6th with the inlet side of the refrigerant compressor 4th is fluid-connected,
• - a chiller branch 3.1 with the chiller 3 , an upstream chiller expansion device AE1 , with the chiller 3 in addition to cooling, for example, an electrical component of the vehicle, it is also used to implement a water heat pump function using the waste heat of at least one electrical component,
• - an AC and heat pump branch 5.1 with the external heat exchanger 5 and the heat pump expansion device AE3 , with the AC and heat pump branch in heating mode 5.1 upstream via the heat pump expansion device AE3 with the interior Evaporator branch 2.1 forming a first branch point Ab1 is fluid connectable and downstream through a defrost expansion member AE5 according to 1 or via a shut-off device A2 according to 2 with the inlet side of the refrigerant compressor 4th Can be fluidly connected, while in AC operation the AC and heat pump branch 5.1 upstream via a shut-off device A4 with the high pressure outlet of the refrigerant compressor 4th is fluid connectable,
• - a heating branch 8.1 with a supply air flow L. for the vehicle interior that directly or indirectly heats the heating condenser 8th or hot gas cooler 8th , the heating branch 8.1 upstream via a shut-off device A3 with the high pressure outlet of the refrigerant compressor 4th is fluid connectable and downstream via a shut-off device A1 with the first branch point Ab1 and thus with the interior evaporator branch 2.1 is fluid connectable,
• - a reheat branch 5.2 with a reheat expansion device designed as an expansion valve AE4 , being the reheat branch 5.2 downstream with the external heat exchanger 5 forming a second branch point Starting at 2 and upstream with the heating condenser 8th or hot gas cooler 8th is fluid-connected,
• - a defrost branch 5.4 with a lockable defrost expansion device AE5 and a check valve R2 according to 1 , being the defrost branch 5.4 upstream via the second branch point Starting at 2 with the external heat exchanger 5 and downstream with the accumulator 7th is fluid connectable,
• - a heat pump return branch 5.4 with a shut-off device A2 and a check valve R2 according to 2 , the heat pump return branch 5.4 upstream via the second branch point Starting at 2 with the external heat exchanger 5 and downstream with the accumulator 7th is fluid connectable,
• - a suction branch 5.5 with a shut-off device A5 , the suction branch 5.5 upstream with the heating condenser 8th or hot gas cooler 8th and downstream via a third branch point From 3 with the defrost expansion device AE5 (see. 1 ) or with the shut-off device A2 (see. 2 ) and the check valve R2 of the defrost branch 5.3 (see. 1 ) or the heat pump return branch 5.4 (see. 2 ) is fluidly connected, and
• - An electrical heating element designed, for example, as a high-voltage PTC heating element 9 as an auxiliary heater for a supply air flow directed into the vehicle interior L. which is located together with the heating condenser 8th or hot gas cooler 8th and the evaporator 2 in an air conditioner 1.1 and the heating condenser 8th or hot gas cooler 8th and thus also the evaporator 2 is downstream on the air side.

As sensors are in the refrigerant circuit 1 according to 1 and 2 several pressure-temperature sensors are provided to control and regulate the system.

So is the refrigerant compressor 4th a first pressure-temperature sensor pT1 assigned to the high pressure outlet, furthermore a second pressure-temperature sensor pT2 at the output of the accumulator 7th , a third pressure-temperature sensor pT3 at the outlet of the external heat exchanger 5 , a fourth pressure-temperature sensor pT4 at the output of the heating condenser 8th or hot gas cooler 8th and finally a fifth pressure-temperature sensor pT5 at the low-pressure side outlet of the chiller 3 arranged.

With the two shut-off devices A3 and A4 according to the 1 and 2 the refrigerant flow is based on the high pressure side of the refrigerant compressor 4th depending on the state of these two shut-off devices, either with the shut-off device open A4 and locked shut-off device A3 for the AC mode in the external heat exchanger 5 directed or flows for the heating or reheat mode with the shut-off element open A3 and closed shut-off device A4 in the heating branch 8.1 .

The following describes the heating operation of the refrigerant circuit 1 to 1 to be discribed.

In heating mode of the refrigerant circuit 1 is made using the external heat exchanger 5 as a heat pump evaporator to implement an air heat pump or using the chiller 3 the shut-off device to implement a water heat pump A4 closed and the shut-off device A3 opened so that hot refrigerant such as R744 enters the heating branch 8.1 can flow. In addition, a combined operation between water and air heat pumps is possible.

To carry out the heating function using the external heat exchanger 5 as a heat pump evaporator, it flows by means of the refrigerant compressor 4th compressed refrigerant through the open shut-off device A3 for the transfer of heat to the supply air flow into the passenger compartment L. in the heating condenser 8th or hot gas cooler 8th and is then over the open shut-off device A1 by means of the heat pump expansion device AE3 in the external heat exchanger 5 relaxes to absorb heat from the ambient air and then flows through the defrost branch 5.4 with the defrosting expansion device fully open AE5 back to the refrigerant compressor 4th . The organs of expansion AE1 , AE2 and AE4 remain closed, as does the shut-off element A5 .

In this air heat pump operation by means of the external heat exchanger 5 this is done via this external heat exchanger 5 guided airflow L1 Heat is extracted and transferred to the refrigerant, thereby cooling the surface of the external heat exchanger. As a result of this cooling of the external heat exchanger, the heat exchanger can become frosted and iced up due to an evaporation temperature which is below the ambient temperature 5 come by condensate from the environment on the surface of the external heat exchanger 5 separates.

If the surface of the external heat exchanger has tires that are relevant for comfort in the vehicle interior 5 with decreasing potential for evaporation of refrigerant and thus decreasing heating power, detectable via a decreasing compressor delivery volume flow, ie reduced power consumption of the refrigerant compressor 4th and / or via the falling high pressure of the refrigerant at the outlet of the refrigerant compressor 4th , the air / heat pump operation is interrupted and defrosting is initiated.

To prevent icing on the external heat exchanger 5 and excessive cooling of the external heat exchanger 5 To prevent refrigerant flowing through, is during the defrosting operation by means of a controllable arrangement 5.6 an air supply to the external heat exchanger 5 prevented. Such an arrangement 5.6 is designed as a controllable air flap arrangement or as a controllable blind arrangement and can be completely closed. The air flap arrangement or louvre arrangement is thus completely closed during the defrosting operation.

In order to carry out such a defrosting operation, the arrangement is therefore first of all - if the boundary conditions on the vehicle allow it 5.6 the airflow L1 to the external heat exchanger 5 interrupted as part of the cooler package and the heat pump expansion element AE3 fully open, eliminating both the heating condenser 8th or hot gas cooler 8th as well as the external heat exchanger 5 on the same from the refrigerant compressor 4th generated high pressure level are operated, the refrigerant compressor 4th is used as the only heat source for this defrost operation. Here are the heating condenser 8th or hot gas cooler 8th and the external heat exchanger 5 connected in series with respect to the refrigerant and operated as heat sinks, so that by means of the refrigerant compressor 4th warmed up refrigerant first on the heating condenser 8th or hot gas cooler 8th is pre-cooled and then the residual heat remaining in the refrigerant in the external heat exchanger 5 in order to defrost the frost or ice on the surface of the external heat exchanger 5 to effect.

That from the external heat exchanger 5 Escaping refrigerant passes through the branch point Starting at 2 in the defrost branch 5.4 one, in which the refrigerant by means of the defrosting expansion element AE5 is relaxed to low pressure. Then the refrigerant is released through the check valve R2 , the accumulator 7th and the low pressure section of the internal heat exchanger 6th to the inlet side of the refrigerant compressor 4th returned.

If the heating condenser is used during this defrosting operation 8th or hot gas cooler 8th does not give off any heat or its high pressure level and thus its temperature level is reduced too much, ie for example depending on the refrigerant used by a minimum amount of greater than 5 bar (chemical refrigerant) or 10 bar (R744), the heat pump expansion element AE3 can also be gradually throttled, reducing the external heat exchanger 5 at a low pressure level, namely at a medium pressure level compared to the pressure level of the heating condenser 8th or hot gas cooler 8th and is thus operated at a temperature level at which a temperature shock does not occur, as would otherwise be the case if the refrigerant compressor 4th generated heat completely and directly via the open shut-off valve A4 on the external heat exchanger 5 would hit.

To carry out the defrosting operation, the high pressure or the medium pressure is used in the external heat exchanger 5 by means of the defrost expansion device AE5 set to a condensation pressure which corresponds to a condensation temperature of greater than 0 ° C, for example 5 ° C. This ensures that a sufficient temperature difference is achieved between the refrigerant and the frosted surface, so that rapid defrosting and defrosting is possible.

During this defrosting operation, the refrigerant compressor 5 can be controlled to a maximum refrigerant volume flow in order to provide a maximum amount of heat for defrosting. Here is the refrigerant compressor 4th designed as a mechanical or electrical compressor.

During the defrosting operation, a heating deficit for the vehicle interior can occur, for example when the electrical heating element is switched on 9 be balanced, thereby reducing the supply air flow L. is additionally heated.

The defrosting operation is ended when the with a temperature sensor T recorded outlet temperature at the outlet of the external heat exchanger 5 reaches a positive temperature threshold value permanently and stably, e.g. 3 ° C.

The third pressure / temperature sensor can also be used pT3 measured pressure value as a reference value for that at the external heat exchanger 5 detected and applied condensation pressure level can be used. If both values are directly related to each other in a further step, it can be ensured that this is the external heat exchanger 5 The refrigerant flowing through either has no overheating in the entire component or, in the case of overheating, that the refrigerant is continuous and over the entire surface in the external heat exchanger 5 to ensure full-surface defrosting has a higher temperature level than the freezing point of water with a temperature of 0 ° C.

After the end of the defrosting operation, activation of a fan arrangement assigned to the external heat exchanger (in 1 not shown) that on the external heat exchanger 5 generated liquid condensate are expelled. With this process of drying by expelling the condensate, there is a short-term and renewed icing on the external heat exchanger 5 prevented.

With the end of the defrosting operation, after opening the arrangement beforehand 5.6 , again to the air heat pump operation using the external heat exchanger 5 be returned by setting the corresponding operating points again, ie the defrost expansion device AE5 is fully opened and the heat pump expansion element AE3 is set again to the corresponding expansion function. Optionally, the electrical heating element is also used 9 switched off or its heating output reduced.

When there is waste heat in the coolant circuit 3.0 is available, defrosting can be done via the AC and heat pump branch 5.1 and the defrost branch 5.4 can also be carried out in such a way that the refrigerant flow after flowing through the heating condenser 8th or hot gas cooler 8th and the open shut-off device A1 into one via the heat pump expansion element AE3 and the external heat exchanger 5 flowing partial flow and one in the chiller branch 3.1 flowing partial flow is divided, with this last-mentioned partial flow a water heat pump operation is carried out by the refrigerant of this partial flow by means of the chiller expansion device AE1 into the chiller 3 is relaxed. This also heats the supply air flow L. and defrosting the external heat exchanger 5 supported. During this defrosting operation, the external heat exchanger 5 and the chiller 3 parallel flows through with refrigerant.

The following is a heating mode using the chiller 3 described as a heat source.

To carry out the heating function using the chiller 3 this flows through the refrigerant compressor 4th compressed refrigerant through the open shut-off device A3 for the transfer of heat to a supply air flow directed into the vehicle interior L. in the heating condenser 8th or hot gas cooler 8th and is then over the open shut-off device A1 and the first branch point Ab1 by means of the chiller expansion device AE1 into the chiller 3 for absorbing waste heat in the coolant circuit 3.0 arranged electrical and / or electronic components relaxed. In this heating function, the expansion organs are AE3 and AE4 as well as the shut-off device A5 closed and the shut-off device A2 fully opened, with refrigerant swapped out in water heat pump operation via the shut-off device A2 from the AC and heat pump branch 5.1 sucked off and through the check valve R2 the accumulator 7th is fed.

An indirect delta connection is realized when the shut-off element is open A1 that from the refrigerant compressor 4th compressed refrigerant by means of the chiller expansion device AE1 into the chiller 3 is relaxed, at the same time the coolant side, so in the coolant circuit 3.0 no mass flow is generated, for example the water used as coolant on the coolant side of the chiller 3 stops or the chiller 3 is not actively flowed through by coolant. The organs of expansion AE2 , AE3 and AE4 remain closed with this switching variant.

During reheat operation, the supply air flow supplied into the vehicle interior is L. by means of the evaporator 2 initially cooled and thus dehumidified, and then with the supply air flow L. heat extracted and that of the refrigerant via the refrigerant compressor 4th supplied heat by means of the heating condenser 8th or the hot gas cooler 8th the supply air flow L. at least partially reheat.

A reheat operation of the refrigerant circuit 1.1 is carried out in different ways depending on the heat balance.

If there is sufficient heating power in the refrigerant circuit 1 only the vaporizer 2 with refrigerant flowing through it by the heating condenser 8th or hot gas cooler 8th downstream by means of the open shut-off device A1 via the evaporator expansion device AE2 with the vaporizer 2 fluid is connected, the chiller expansion element AE1 Is blocked. From the vaporizer 2 the refrigerant flows over the check valve R1 , the accumulator 7th and the internal heat exchanger 6th back to the refrigerant compressor 4th , being the one in the evaporator 2 Heat absorbed together with that via the refrigerant compressor 4th heat flow entered via the heating condenser 8th or hot gas cooler 8th back to the supply air flow into the vehicle interior L. is delivered. The organs of expansion AE1 , at AE3 and AE4 are completely closed.

If there is a lack of heat in the refrigerant circuit 1.1 becomes an evaporator for increased heat absorption 2 also the chiller 3 through targeted and needs-based opening of the chiller expansion element AE1 and / or the external heat exchanger 5 by opening the heat pump expansion element in a targeted and needs-based manner AE3 involved in the post-heating process.

In the event of excess heat in reheat mode, the heat transfer to the supply air flow L. of the passenger compartment via the heating condenser 8th or hot gas cooler 8th additionally via the external heat exchanger 5 Heat is given off to the surroundings of the vehicle before the refrigerant passes through the evaporator 2 back to the refrigerant compressor 4th flows. For this purpose, the reheat expansion organ AE4 of the reheat branch 5.2 the refrigerant for condensation is expanded to an intermediate pressure above the evaporation pressure and then by means of the evaporator expansion element AE2 into the evaporator 2 expanded to low pressure.

Using this reheat branch 5.2 a defrosting operation is carried out if during an air heat pump operation by means of the external heat exchanger 5 tires in the outer heat exchanger that are relevant for comfort in the vehicle interior 5 with decreasing potential for evaporation of refrigerant and thus decreasing heating capacity is detected. This detection takes place on the basis of a falling compressor delivery volume flow, ie the power consumed by the refrigerant compressor 4th and / or over the course, ie the falling high pressure of the refrigerant at the outlet of the refrigerant compressor 4th .

In this case, the air / heat pump operation is interrupted and then defrosting is initiated.

This defrost operation using the reheat branch 5.2 is based on the refrigeration system 10 with the refrigerant circuit 1 according to 2 explained.

During this defrosting operation, this is done by the refrigerant compressor 4th generated refrigerant via the open shut-off device A3 the heating condenser 8th or hot gas cooler 8th and then with the shut-off valve closed A1 and fully open reheat expansion organ AE4 to the external heat exchanger 5 directed, the shut-off device A2 of the heat pump return branch 5.4 as well as the shut-off device A4 are closed.

This will be both the heating condenser 8th or hot gas cooler 8th as well as the external heat exchanger 5 on the same from the refrigerant compressor 4th generated high pressure level operated, wherein the refrigerant compressor 4th is used as the only heat source for this defrost operation. Here are the heating condenser 8th or hot gas cooler 8th and the external heat exchanger 5 connected in series with respect to the refrigerant and operated as heat sinks, so that by means of the refrigerant compressor 4th warmed up refrigerant first on the heating condenser 8th or hot gas cooler 8th is pre-cooled and then the residual heat remaining in the refrigerant in the external heat exchanger 5 in order to defrost the frost or ice on the surface of the external heat exchanger 5 to effect.

That from the external heat exchanger 5 Leaving refrigerant is via the AC and heat pump branch 5.1 when the heat pump expansion element is fully open AE3 the chiller branch 3.1 fed. In this chiller branch 3.1 is made by means of the chiller expansion device AE1 as a defrost expansion device AE relaxed to low pressure before it is over the accumulator 7th and the internal heat exchanger 6th to the refrigerant compressor 4th is returned. By means of the chiller expansion device AE1 is relaxed from high pressure level to low pressure. The high pressure level is to be set at least to a value greater than 0 ° C., for example 5 ° C., in order to continue to have an additional heating effect for the cabin supply air flow L. to achieve this value should be significantly higher. This ensures that a sufficient temperature difference is achieved between the refrigerant and the frosted surface, which in turn enables rapid de-icing and defrosting.

This defrosting operation can be implemented as an indirect delta connection, in which the coolant side is simultaneously via the chiller 3 , so in the coolant circuit 3.0 no volume flow is generated, for example the water-glycol mixture used as coolant on the coolant side of the chiller 3 stops or the chiller 3 is not actively flowed through by coolant. Alternatively, the defrost mode can also be used as a cycle with an active chiller 3 be carried out in which the coolant in the coolant circuit 3.0 and at the same time the refrigerant flowing through it evaporates becomes. Here, additional heat can be absorbed from the coolant circuit in order to heat the supply air flow L. and defrosting the external heat exchanger 5 to support.

In this defrost mode using the AC and heat pump branches 5.1 and the chiller branch 3.1 the refrigerant compressor can 4th can be controlled to a maximum refrigerant volume flow at the maximum possible pressure ratio in order to provide a maximum amount of heat for defrosting. Here is the refrigerant compressor 4th designed as a mechanical or electrical compressor.

If the heating condenser is used during this defrosting operation 8th or hot gas cooler 8th does not give off any heat, or the pressure level in the heating register and thus its temperature level is reduced too much, e.g. depending on the refrigerant used by a minimum of more than 5 bar (chemical refrigerant) or 10 bar (R744), the reheat expansion unit AE4 can also be throttled so far that the external heat exchanger 5 at a lower pressure level, namely a medium pressure compared to the pressure level of the heating condenser 8th or hot gas cooler 8th and is thus operated at a temperature level at which a temperature shock does not occur, as would otherwise be the case if the refrigerant compressor 4th generated heat completely and directly via the open shut-off valve A4 on the external heat exchanger 5 would hit. In the case of medium pressure, the requirement also applies that the intermediate condensation pressure level and thus the condensation temperature are above the 0 ° C line by means of the defrosting expansion device AE (i.e. the chiller expansion element AE1 ) and the reheat expansion organ AE4 is to be set. The pressure position can be monitored via one in the reheat branch 5.2 provided pressure or pressure-temperature sensor can be realized.

About the progress of icing on the external heat exchanger 5 and excessive cooling of the external heat exchanger 5 To prevent the refrigerant flowing through and an associated drop in the pressure level, during the defrosting operation by means of a controllable arrangement 5.6 an air supply to the external heat exchanger 5 prevented.

Such an arrangement 5.6 is designed as a controllable air flap arrangement or as a controllable blind arrangement and can be completely closed. The air flap arrangement or louvre arrangement is thus completely closed during the defrosting operation.

With this by means of the AC and heat pump branch 5.1 as well as the chiller branch 3.1 performed defrosting operation can advantageously the chiller 3 can be used as an additional heat source in order to reduce the duration of the defrosting operation. Another advantage is that the direction of flow of the refrigerant during this defrosting operation corresponds to the direction of flow of the refrigerant in AC operation, as a result of which flow and pressure losses are low. Thereby a pre-cooling of the refrigerant by means of the heating condenser 8th or hot gas cooler 8th occurs, caused by the external heat exchanger 5 residual heat released so that no temperature shock can occur.

During the defrosting operation, a heating deficit for the vehicle interior can occur, for example when the electrical heating element is switched on 9 the supply air flow L. be heated.

The defrosting operation is ended when the pressure / temperature sensor pT3 recorded outlet temperature at the outlet of the external heat exchanger 5 permanently and stable a positive temperature threshold value, reached, e.g. 3 ° C.

The third pressure-temperature sensor can also be used pT3 measured pressure value as a reference value for that at the external heat exchanger 5 detected and applied condensation pressure level can be used. If both values are directly related to each other in a further step, it can be ensured that this is the external heat exchanger 5 The refrigerant flowing through either has no overheating in the entire component or, in the case of overheating, that the refrigerant is continuous and over the entire surface in the external heat exchanger 5 to ensure full-surface defrosting has a higher temperature level than the freezing point of water with a temperature of 0 ° C.

After the end of the defrosting operation, one of the external heat exchangers can be activated 5 assigned fan arrangement (in 2 not shown) that on the external heat exchanger 5 accumulated liquid condensate is expelled. With this process of drying by expelling the condensate, a short-term and renewed icing on the external heat exchanger is intended 5 be prevented.

With the end of the defrosting operation, the air heat pump can be operated again using the external heat exchanger 5 be returned by having previously opened the arrangement 5.6 the corresponding working points are set again, ie the shut-off device A2 opens fully and when open Shut-off device A1 and closed reheat expansion device AE4 the heat pump expansion device AE3 is set again to the corresponding expansion function. Optionally, the electrical heating element is also used 9 switched off or its heating output reduced.

Used when executing the refrigerant circuit 1 the refrigeration system 10 a shut-off valve A2 in the heat pump return branch 5.4 used, the defrosting process can continue with the heating condenser still active 8th or hot gas cooler 8th fully only via the reheat branch 5.2 and the reheat expander AE4 respectively. Comes instead of the shut-off valve A2 a defrost expansion device AE5 for use (cf. 1 ), a defrosting process of the external heat exchanger can take place 5 either through the reheat branch 5.2 and the reheat expander AE4 or alternatively via the AC and heat pump branch 5.1 and the heat pump expansion element assigned to it AE3 according to the embodiment 1 .

It is also possible that when there is sufficient waste heat in the fluid of the coolant circuit 3.0 after the end of the defrosting operation, the system does not switch back to air-heat pump operation, but instead switches from the direct or indirect triangular process to water-heat pump operation during defrosting. After the defrosting and drying process has taken place, the interior heating is continued using a pure water heat pump operation.

For the sake of completeness, the AC operation of the refrigerant circuit is shown 1 the refrigeration system 10 according to the 1 and 2 explained.

The heating branch is in AC operation 8.1 by means of the shut-off device A3 blocked so that hot refrigerant, such as R744, cannot pass through the heating condenser 8th or hot gas cooler 8th can flow. To retrieve refrigerant from the inactive heating branch 8.1 however, the shut-off device A5 of the suction branch 5.5 opened and the refrigerant can through the shut-off device A5 and the check valve R2 , with the defrosting expansion device closed at the same time AE5 (see. 1 ) or with the shut-off element closed at the same time A2 (see. 2 ) in the direction of the accumulator 7th stream.

In AC operation of the refrigerant circuit 1 according to 1 and 2 the refrigerant, which has been compressed to high pressure, flows from the refrigerant compressor 4th with the shut-off element open A4 in the external heat exchanger 5 , the high pressure section of the internal heat exchanger 6th , via the fully open heat pump expansion element AE3 as well as the first branch point Ab1 in the evaporator branch 2.1 and / or in the chiller branch 3.1 . From the chiller branch 3.1 the refrigerant flows over the accumulator 7th and the low pressure section of the internal heat exchanger 6th back to the refrigerant compressor 4th , while the refrigerant from the evaporator branch 2.1 via the check valve R1 flows and then over the accumulator 7th and the low pressure section of the internal heat exchanger 6th also back to the refrigerant compressor 4th can flow.

The first pressure-temperature sensor pT1 of the refrigerant circuit 1 is used to determine the refrigerant temperature and the high pressure of the compressed medium at the outlet of the refrigerant compressor 4th . The purpose of monitoring these two variables is to determine the maximum permissible mechanical and thermal loads on the refrigeration system, especially at the outlet from the refrigerant compressor 4th to monitor and, if necessary, to limit the system operation by means of curtailment measures, requested by a control device, for example an air conditioning control device, in order not to exceed the maximum permissible values.

The second pressure-temperature sensor pT2 of the refrigerant circuit 1 is used, in particular in refrigeration systems with a refrigerant reservoir arranged on the low pressure side, for underfilling detection, but also for setting and monitoring a required low pressure.

The one on the outlet side of the external heat exchanger 5 provided third pressure-temperature sensor pT3 of the refrigerant circuit 1 serves primarily to set or monitor the system operating parameters “optimal high pressure” in supercritical system operation or “subcooling after the external heat exchanger 5 " with subcritical system operation.

This third pressure-temperature sensor monitors in a further function pT3 that during defrosting in the external heat exchanger 5 set medium pressure level. Depending on the position of the pressure sensor component p3 before or after the external heat exchanger 5 on the resulting pressure position after or in front of the external heat exchanger 5 getting closed.

The one according to the refrigerant circuit 1 to 1 and 2 downstream of the heating condenser 8th or hot gas cooler 8th arranged fourth pressure-temperature sensor pT4 is used to control, but also to monitor the different operating modes of the refrigerant circuit 1 , especially in heat pump mode with actively flowing heating condenser 8th or hot gas cooler 8th by a control device, for example an air conditioning control device.

The fifth pressure-temperature sensor pT5 of the refrigerant circuit 1 is used to monitor and control the degree of overheating at the outlet of the chiller 3 .

In addition, it should be mentioned that all sensors can be designed both as combination sensors or as individual sensors for detecting the state variables of the refrigerant circuit.

List of reference symbols

1

Refrigerant circuit of the refrigeration system 10

1.1

Air conditioner

2

Evaporator

2.1

Indoor evaporator branch

3

Chiller

3.0

Coolant circuit of the chiller 3

3.1

Chiller branch

4th

Refrigerant compressor

5

external heat exchanger

5.1

AC and heat pump branch

5.2

Reheat branch

5.4

Defrost branch or heat pump return branch

5.5

Suction branch

5.6

Arrangement of the external heat exchanger 5

6th

internal heat exchanger

7th

accumulator

8th

internal heating condenser or heating gas cooler

8.1

Heating branch

9

electric heating element

10

Refrigeration system

A1

Shut-off device

A2

Shut-off device

A3

Shut-off device

A4

Shut-off device

A5

Shut-off device

Ab1

Branch point

Starting at 2

Branch point

From 3

Branch point

AE

Defrost expansion device

AE1

Chiller expansion device

AE2

Evaporator expansion device

AE3

Heat pump expansion device

AE4

Reheat expansion device

AE5

Defrost expansion device

L.

Supply air flow

L1

Airflow

pT1

first pressure-temperature sensor

pT2

second pressure-temperature sensor

pT3

third pressure-temperature sensor

pT4

fourth pressure-temperature sensor

pT5

fifth pressure-temperature sensor

R1

check valve

R2

check valve

T

Temperature sensor

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• FR 3025299 A1 [0005]
• DE 102007028252 A1 [0008]
• US 2014/0020415 A1 [0009]

Claims (9)

A method for operating a refrigeration system (10) for a vehicle with a refrigerant circuit (1) having a heat pump function, the refrigerant circuit (1) having the following components: - a refrigerant compressor (4) with a high pressure outlet and an inlet side, - an external heat exchanger (5), which can be operated either to carry out a refrigeration system operation as a condenser or gas cooler or to carry out a heat pump operation as a heat pump evaporator by means of a heat pump expansion element (AE3) and which can be connected to the high pressure outlet of the refrigerant compressor (4), - An evaporator branch (2.1) with an evaporator (2) and an evaporator expansion element (AE2), the evaporator branch (2.1) being connectable on the low-pressure side to the inlet side of the refrigerant compressor (4) and on the high-pressure side to the external heat exchanger (5), and - A heating branch (8.1) with a heating condenser (8) or heating gas cooler (8) which directly or indirectly heats a supply air flow (L) for the vehicle interior, the heating branch (8.1) for carrying out a heat pump operation upstream with the high pressure outlet of the refrigerant compressor (4) and downstream with the heat pump expansion element (AE3) can be connected, and wherein for defrosting the external heat exchanger (5) after a heat pump operation - The external heat exchanger (5) is connected to the heating condenser (8) or heating gas cooler (8) at the high pressure generated by the refrigerant compressor (4) or at a medium pressure which is lower than the high pressure, and - The refrigerant emerging from the external heat exchanger (5) is expanded to a low pressure by means of a defrosting expansion device (AE, AE5) and is supplied to the refrigerant compressor (4) on the inlet side. Procedure according to Claim 1 , in which - the defrosting expansion element (AE5) is arranged in a defrosting branch (5.4), with which the external heat exchanger (5) is connected to the inlet side of the refrigerant compressor (4) to carry out the defrosting operation, - to carry out the defrosting operation the external heat exchanger (5) is connected to the heating condenser (8) or heating gas cooler (8) via the heat pump expansion element (AE3), the heat pump expansion element (AE3) either being controlled in an open state or being controlled in such a way that the The outer heat exchanger (5) operates at a mean pressure that is lower than the high pressure, and - the refrigerant is expanded to low pressure by means of the defrosting expansion device (AE5). Procedure according to Claim 1 , in which - the refrigerant circuit (1) is formed with a chiller branch (3.1) which has a chiller (3) and a chiller expansion element (AE1) and which can be connected in parallel to the evaporator branch (2.1), - to carry out a reheat operation the inner heating condenser (8) or hot gas cooler (8) is connected downstream to the outer heat exchanger (5) by means of a reheat branch (5.2) having a reheat expansion element (AE4), - reheat operation is carried out to carry out the defrosting operation, wherein the reheat expansion element (AE4) is either controlled into an open state or controlled in such a way that the external heat exchanger (5) works at a lower mean pressure compared to the high pressure, and - by means of the chiller expansion element (AE1) as a defrosting expansion element ( AE) the refrigerant is expanded to low pressure. Method according to one of the preceding claims, in which - The external heat exchanger (5) is designed with a controllable arrangement (5.6) for the flow of outside air, with at least part of the surface of the external heat exchanger (5) being closable for the air flow by means of this arrangement (5.6), and - The arrangement (5.6) is closed to carry out the defrosting operation. Method according to one of the preceding claims, in which the defrosting operation is ended when the outlet temperature of the refrigerant emerging from the external heat exchanger (5) reaches a predetermined positive temperature threshold value. Method according to one of the preceding claims, in which, to carry out the defrosting operation, the pressure value in the external heat exchanger (5) by means of the defrosting expansion device (AE, AE5) or by means of the defrosting expansion device (AE, AE5) and the heat pump expansion device (AE3 ) or by means of the defrost expansion device (AE, AE5) and the reheat expansion device (AE4) is set to a condensation pressure which corresponds to a condensation temperature of greater than 0 ° C. Method according to one of the preceding claims, without Claim 3 , in which a pressure-temperature sensor (pT3) for setting and monitoring the mean pressure for the AC and heat pump branch (5.1) with the external heat exchanger (5) and the defrosting expansion element (AE5) to Achieving a condensation pressure level in the refrigerant above the freezing point of water at 0 ° C is used. Method according to one of the preceding claims, without Claim 2 , in which a pressure-temperature sensor (pT3) for monitoring and setting the mean pressure for the reheat branch (5.2) with the external heat exchanger (5) up to the chiller expansion element (AE1) as a defrosting expansion element (AE) to achieve a condensation pressure level is used in the refrigerant above the freezing point of water at 0 ° C. Method according to one of the preceding claims, in which, after the end of the defrosting operation, the liquid condensate generated on the outer heat exchanger (5) is expelled by means of a fan arrangement assigned to the outer heat exchanger (5).

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