DE102018209769B4 - Method for operating a refrigeration system of a vehicle having a refrigerant circuit - Google Patents

Abstract

Method for operating a refrigerant circuit (10) of a refrigeration system of a vehicle with a chiller branch (1.0), which has a chiller (1), a first expansion element (AE1) and a first pressure-temperature sensor (pT1 ) and is thermally coupled to a coolant circuit (1.1),- at least one interior evaporator branch (2.0) which has an interior evaporator (2) and a second expansion element (AE2) and is connected in parallel to the chiller branch (1.0). ,- a refrigerant compressor (3), and- a condenser or gas cooler (4), whereby- in a single chiller mode the operating point of the refrigerant circuit (10) is set at the refrigerant outlet of the chiller (1) close to the dew line of the refrigerant,- the low pressure and the associated temperature of the refrigerant is detected by means of the first pressure-temperature sensor (pT1) of the chiller (1), and- the low pressure by controlling the refrigerant compression chters (3) is limited to a maximum low-pressure value that depends on the ambient conditions and the required cooling capacity of the chiller (1) or is lowered with a reduction in the cooling capacity on the chiller (1) if there is a torque overload on the refrigerant compressor (3) or a specified temperature deviation from the dew line of the refrigerant is detected at the refrigerant outlet of the chiller (1).

Description

The invention relates to a method for operating a refrigerant circuit for a vehicle with at least two evaporators, namely at least one interior evaporator and an evaporator designed as a chiller.

The interior evaporator can be designed as a front evaporator and/or as a rear evaporator of the vehicle interior and is used to condition an inlet air flow entering the vehicle interior.

In addition to the interior or front evaporator, electrified vehicles require a separate coolant circuit for conditioning and temperature control of the energy store, which is usually implemented as a high-voltage battery. Such a coolant circuit is coupled to the coolant circuit by means of a heat exchanger, such a heat exchanger in turn also being designed as an evaporator for cooling an air flow or as a so-called chiller for cooling a coolant, as is the case, for example, in DE 10 2017 108 809 A1 , the DE 10 2016 108 468 A1 or the DE 10 2009 015 658 A1 is known.

the DE 10 2016 117 075 A1 describes a system in which a high-voltage battery of a hybrid or electric vehicle is cooled by means of a coolant circuit which has a coolant/coolant heat exchanger which is thermally coupled to a coolant circuit. To reduce the need for refrigerant-based evaporators, the refrigerant from the refrigerant circuit is also used for cooling a rear zone of the passenger compartment using a refrigerant-to-air heat exchanger. In addition, a passive cooling mode is also provided for the high-voltage battery by means of a passive cooler exposed to the vehicle's ambient air.

In a similar way also describes the DE 10 2014 001 022 A1 a coolant circuit for a high-voltage battery, which is thermally coupled to a refrigerant circuit via a heat exchanger. This coolant circuit has a cooler which is acted upon by the ambient air of the vehicle. This cooler can be bypassed using a bypass line.

From the DE 10 2009 021 530 A1 a coolant circuit for a high-voltage battery is known, in which both an air/coolant heat exchanger and a chiller thermally coupled to a coolant circuit are arranged. The coolant circuit is designed in such a way that the coolant can be routed either only through the air/coolant heat exchanger or only through the chiller or through both components.

the US2012/0125032 shows a refrigeration system with a refrigerant circuit and a method for parallel air and battery cooling. The refrigerant circuit includes an evaporator arrangement for parallel air and battery cooling, with a refrigerant compressor and a condenser being provided as an evaporator with an associated controllable expansion element for air cooling and an evaporator as a battery cooler with an associated controllable expansion element for battery cooling. A throttling device is located between the evaporator for battery cooling and the low-pressure inlet of the refrigerant compressor, with which the refrigerant is expanded to the evaporation pressure of the evaporator for air cooling.

From the DE 11 2016 003 000 T5 a refrigerant circuit of a refrigeration system for an electric vehicle with a heat pump function is known, with which a noise occurring when changing the operating mode is to be eliminated or reduced. For this purpose, when changing the operating mode, the pressure difference at a valve element should be reduced before this valve element is opened.

Finally, be on the DE 10 2011 118 162 B4 referred, from which a multiple evaporator having refrigerant circuit with a heat pump function is known. In addition to an interior evaporator, a first and second chiller is also provided for this refrigerant circuit, with an expansion element being connected upstream of each of these evaporators. In addition, a further expansion element is connected downstream of the interior evaporator, as a result of which this interior evaporator can be operated at an intermediate pressure level. Finally, a condenser provided for cooling operation is used to implement an air heat pump as a heat pump evaporator with an associated expansion element.

It is the object of the invention to specify a method for operating a refrigeration system of a vehicle having a refrigerant circuit with at least two evaporators, namely at least one interior evaporator and an evaporator designed as a chiller, with which in single chiller mode, i.e. with exclusive operation of the Chillers a functionally reliable and thus error-free operation of the refrigerant circuit is ensured.

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

• - einem Chiller-Zweig, welcher einen Chiller, ein erstes Expansionsorgan und einen stromabwärts des Chillers nachgeschalteten Druck-Temperatursensor aufweist und mit einem Kühlmittelkreislauf thermisch gekoppelt ist,
• - wenigstens einem Innenraum-Verdampferzweig; welcher einen Innenraum-Verdampfer und ein zweites Expansionsorgan aufweist und dem Chiller-Zweig parallel geschaltet ist,
• - einem Kältemittelverdichter, und
• - einem Kondensator oder Gaskühler, wird
• - in einem Single-Chiller-Modus der Betriebspunkt des Kältemittelkreislaufs am Kältemittelaustritt des Chillers nahe der Taulinie des Kältemittels eingestellt,
• - der Niederdruck und die zugehörige Temperatur des Kältemittels mittels des Druck-Temperatursensors des Chillers detektiert, und
• - der Niederdruck durch Steuerung des Kältemittelverdichters auf einen von Umgebungsbedingungen, und der benötigten Kälteleistung des Chillers abhängigen maximalen Niederdruckwert beschränkt oder unter Reduzierung der Kälteleistung an dem Chiller abgesenkt, wenn eine Drehmomentüberlastung am Kältemittelverdichter oder eine vorgegebene Abweichung der Temperatur von der Taulinie des Kältemittels am Kältemittelaustritt des Chillers detektiert wird.

In this method for operating a refrigerant circuit of a refrigeration system of a vehicle

• - a chiller branch, which has a chiller, a first expansion element and a pressure-temperature sensor downstream of the chiller and is thermally coupled to a coolant circuit,
• - At least one interior evaporator branch; which has an interior evaporator and a second expansion element and is connected in parallel to the chiller branch,
• - a refrigerant compressor, and
• - a condenser or gas cooler
• - in a single chiller mode, the operating point of the refrigerant circuit is set at the refrigerant outlet of the chiller close to the dew line of the refrigerant,
• - detects the low pressure and the associated temperature of the refrigerant by means of the pressure-temperature sensor of the chiller, and
• - the low pressure is limited by controlling the refrigerant compressor to a maximum low pressure value that depends on the ambient conditions and the required cooling capacity of the chiller, or is lowered by reducing the cooling capacity at the chiller if there is a torque overload on the refrigerant compressor or a specified deviation of the temperature from the dew line of the refrigerant at the refrigerant outlet of the chiller is detected.

In order to avoid the potential disadvantages associated with a high low pressure in the single chiller mode and thus a high evaporation temperature of the refrigerant, the efficient operation of the refrigerant circuit associated with the operation of the refrigerant at the refrigerant outlet of the chiller close to the dew line, which is particularly important for systems with a refrigerant reservoir arranged on the high-pressure side, is only slightly worsened in that when a torque overload is detected on the refrigerant compressor or when there is a specified deviation of the temperature from the dew line of the refrigerant at the refrigerant outlet of the chiller, either the low pressure is limited to a maximum permissible low pressure value or the low pressure is at least constant Cooling capacity, but loss of system efficiency where the chiller is lowered.

With the increasing low pressure of the refrigerant, which is usually also linked to an increasing coolant inlet temperature in the chiller, its density also increases and thus leads to an increased refrigerant requirement in the low-pressure section of the refrigerant circuit, i.e. the risk of refrigerant underfilling increases, which ultimately results in a Refrigerant underfill can result. This means that in single chiller mode the refrigerant at the chiller's refrigerant outlet can no longer be operated close to the dew line, and the refrigerant increasingly overheats. Ideally, with a required cooling capacity, the low pressure is only increased until an increase in the value of the overheating of the refrigerant is detected for the first time, and from this point in time the low pressure tends to drop slightly. It must be taken into account that the desired refrigeration output is set from the interaction of low pressure via the refrigerant compressor and proximity to the dew line via the first expansion element.

With the reduction of the low pressure, the evaporation temperature is also reduced. Here, the low pressure is reduced by controlling the refrigerant compressor to a value at which the system operating point is again set close to the dew line for efficient system operation. Since there is now the option of providing more cooling capacity than is ultimately required by the system, (high-frequency) on-off operation or two-point control operation of the refrigeration system would be conceivable. In addition, the system could work with excess cooling capacity for a longer period of time before the cooling circuit is idle for a longer period of time in the sense of a low-frequency two-point control operation.

A third option is the setting of a typical maximum low pressure of the refrigerant circuit, e.g. 4.5 bar in an R1234yf system, with then increasing overheating due to the reduction of the refrigerant mass flow via the first expansion element.

The maximum low pressure value is determined depending on the ambient conditions and the current cooling capacity of the chiller. The ambient conditions relate, for example, to the ambient temperature, i.e. a value below the ambient temperature should be set as the evaporation temperature when the refrigerant circuit starts up, so that the efficiency-optimal operating point can be approached again over the duration of operation, taking into account the values at the first pressure-temperature sensor. The current refrigerating capacity of the chiller determines the maximum low-pressure value in such a way that with a decreasing refrigerating capacity requirement on the coolant side of the chiller, the value of the low-pressure level tends to keep increasing.

The detection of the torque overload on the refrigerant compressor is thus realized with an electrically driven refrigerant compressor ized that such a refrigerant compressor generates an error signal in the event of a torque overload, which is fed to a control unit of the refrigerant circuit, for example an air conditioning control unit. In the case of a refrigerant compressor which is driven mechanically, for example by an internal combustion engine, a torque overload is detected in that the non-positive connection of the magnetic coupling is caused to slip.

According to an advantageous further development of the invention, after the low pressure has been reduced, the refrigerating capacity at the chiller is adjusted again to the desired refrigerating capacity by means of a control of the first expansion element together with the refrigerant compressor. In this way, the chiller produces that cooling capacity again that was produced by the same before the low pressure was reduced, but at an operating point with lower efficiency compared to the operating point set before the low pressure was reduced. On the system side, the pressure difference between the low and high pressure sides and thus the pressure ratio is increased.

• - der Kältemittelkreislauf mit einem Niederdruck-Kältemittelsammler ausgebildet wird, mit welchem definierte Kältemitteldampfgehalte einstellbar sind, und
• - das Kältemittel zur Einstellung auf dessen Taulinie oder nahe der Taulinie im Zwei-Phasen-Gebiet des Kältemittels mittels des Niederdruck-Kältemittelsammlers auf einen Überhitzungsgrad von 0 K eingestellt wird.

Hierbei wird die Eigenschaft des niederdruckseitigen Akkumulators genutzt, dass dieser im Single-Chiller-Modus einen konstanten Dampfgehalt damit eine definierte Kältemittelgüte einstellt, sich also am Kältemittelaustritt des Chillers eine Überhitzung mit einem Wert Null einstellt, d. h. der Zustand des Kältemittels wird auf dessen Taulinie oder links von dieser im Zwei-Phasen-Gebiet des Kältemittels liegend, eingestellt. Mit dem ersten, dem Chiller zugehörigen Expansionsorgan erfolgt für den unterkritischen Betrieb der Kälteanlage eine Unterkühlungsregelung des Kältemittels am Austritt des Kondensators bzw. Gaskühler auf Basis der erfassten Werte für Druck und Temperatur oder für den überkritischen Betrieb der Kälteanlage eine Regelung auf einen optimalen Hochdruck auf Basis der gemessenen Kältemitteltemperatur am Austritt des Gaskühlers, die wiederum als Eingangsgröße für den Sollhochdruck zur Einstellung des Betriebspunkts zum Erzielen der optimalen Systemeffizienz dient.A further advantageous embodiment provides that

• - the refrigerant circuit is designed with a low-pressure refrigerant collector, with which defined refrigerant vapor contents can be adjusted, and
• - the refrigerant is adjusted to a degree of superheat of 0 K for adjustment on its dew line or near the dew line in the two-phase region of the refrigerant by means of the low-pressure refrigerant receiver.

Here, the property of the low-pressure side accumulator is used, that in single chiller mode it has a constant vapor content and thus a defined refrigerant quality, i.e. overheating with a value of zero occurs at the refrigerant outlet of the chiller, i.e. the state of the refrigerant is measured on its dew line or to the left of this lying in the two-phase region of the refrigerant. With the first expansion element associated with the chiller, sub-cooling control of the refrigerant at the outlet of the condenser or gas cooler is carried out for subcritical operation of the refrigeration system on the basis of the recorded values for pressure and temperature, or for supercritical operation of the refrigeration system control is based on an optimal high pressure the measured refrigerant temperature at the outlet of the gas cooler, which in turn serves as an input variable for the target high pressure for setting the operating point to achieve optimal system efficiency.

If the low pressure increases in single chiller mode and one of the adverse consequences is detected (torque overload on the refrigerant compressor or increasing overheating of the refrigerant at the refrigerant outlet of the chiller), the low pressure is either limited to the maximum low pressure value or lowered to a value below this maximum low pressure value. The refrigeration capacity of the chiller is then set back to the value reached before the low pressure was reduced by the corresponding interaction of the refrigerant compressor by increasing the stroke or speed and expansion element, usually by further throttling. It must be taken into account that situations can arise in which the refrigerant circuit can work as a system detached from subcooling control or control of the optimum high pressure. In this case, an operating point with lower efficiency is set compared to the operating point reached before the low pressure was reduced.

With increasing low pressure, the chiller output can be reduced at a fixed coolant flow temperature and at the same time by means of subcooling set by means of the first expansion element or optimal high pressure set, down to an operating point at which possible critical operating limits (overheating, torque) are reached. From this point on no further power reduction is possible, the system has reached a limit.

• - der Kältemittelkreislauf mit einem Hochdruck-Kältemittelsammler ausgebildet wird, und
• - das Kältemittel zur Einstellung auf oder nahe dessen Taulinie mittels des ersten erstes Expansionsorgans auf einen Überhitzungsgrad mit einem Wert zwischen 3 und 5K geregelt wird.

An alternative and advantageous embodiment provides that

• - the refrigerant circuit is designed with a high-pressure refrigerant collector, and
• - the refrigerant is regulated to a degree of overheating with a value between 3 and 5K for setting at or near its dew line by means of the first first expansion element.

In such a refrigerant circuit with a high-pressure-side refrigerant collector, the operating point of the refrigerant at the refrigerant inlet of the chiller is set at or near its dew line by using the first expansion element, ie the expansion element associated with the chiller, to regulate a degree of superheating to a value between 3 and 5K. The low-pressure position is set here with the refrigerant compressor. If the cooling capacity to be provided by the chiller decreases, in particular if the coolant flow temperature remains the same, the low pressure increases at the same time, and to be precise not insignificantly above the standard operating pressure values of a refrigeration system operation towards the inside room air conditioning until either a torque overload of the refrigerant compressor is detected, or due to the increasing density of the refrigerant and the associated. If there is no refrigerant charge, the degree of overheating increases, i.e. it can no longer be regulated to a value between 3 and 5 K and, as a result, the low pressure is either limited to the maximum low pressure value by appropriate control of the refrigerant compressor or is reduced by increasing the cooling capacity of the chiller, assuming the coolant flow temperature remains the same. The refrigeration capacity of the chiller is then increased again to the value reached before the low pressure was reduced by the corresponding interaction of the refrigerant compressor by increasing the stroke or speed and expansion element, usually by further throttling. It must be taken into account that situations can arise in which the system can work independently of the setting of the optimum degree of superheating or possibly provide more cooling capacity than is required. In this case, an operating point is set with lower efficiency than the operating point reached before the low pressure was reduced.

• - der Innenraum-Verdampfer auf einem Mitteldruckniveau-Niveau betrieben wird, und
• - der Chiller in Abhängigkeit der angeforderten Kühlleistung durch Regelung des Kältemittelverdichters und des ersten Expansionsorgans auf einem Niederdruck-Niveau betrieben wird.

According to a further preferred embodiment of the invention, in a chiller and evaporator operation, a third expansion element is connected downstream of the interior evaporator, wherein

• - the interior evaporator is operated at a medium-pressure level, and
• - The chiller is operated at a low-pressure level depending on the required cooling capacity by controlling the refrigerant compressor and the first expansion device.

With such a multiple evaporator operation, the interior evaporator becomes the reference variable of the refrigerant process and specifies the low pressure level and thus the required evaporation temperature. If the refrigerant circuit has a low-pressure refrigerant collector, ie an accumulator on the low-pressure side, such an accumulator regulates the vapor content of the refrigerant at the outlet of that evaporator which generates the highest cooling capacity and thus delivers the largest refrigerant mass flow. The vapor content, which is actively set by this accumulator on the low-pressure side, occurs in the steady state of the refrigerant circuit both at the outlet of the evaporator with the highest cooling capacity and at the refrigerant outlet of the accumulator.

In such a dual operation, the interior evaporator is followed by an electrically or mechanically controllable third expansion element, which ensures that the interior evaporator branch does not fall below a low pressure that leads to icing. With this third expansion element, a medium-pressure level is set in the interior evaporator branch, while any desired low-pressure level is set in the chiller by means of the compressor, depending on the required cooling capacity of the chiller. The degree of overheating is set with the first expansion element assigned to the chiller, with the cooling capacity of the chiller being able to be varied depending on the degree of overheating at the respective low pressure. The maximum cooling capacity of the chiller is achieved when the refrigerant at the refrigerant outlet of the chiller is operated close to the dew line by using the expansion element to regulate the degree of overheating to a value between 3 and 5 K. In fact, the maximum refrigeration capacity for a given low pressure is achieved when the refrigerant outlet condition at the chiller is rather just below the dew line, but due to the coupling of pressure and temperature, neither this point nor the dew line itself can be precisely adjusted and is therefore the system operation is geared towards the mentioned low superheat values.

• - der Kältemittelzustand am Kältemittelaustritt des Chillers nahe an dessen Taulinie eingestellt, und,
• - der Innenraum-Verdampfer mittels des dritten Expansionsorgans auf einem Mitteldruck-Niveau betrieben.

According to an advantageous development of the multi-evaporator operation according to the invention, when the low pressure of the chiller is lower than the low pressure of the interior evaporator, the cooling capacity of the chiller is increased

• - the refrigerant state at the chiller refrigerant outlet is adjusted close to its dew line, and,
• - The interior evaporator operated by means of the third expansion device at a medium-pressure level.

In this embodiment of the invention, the low pressure of the chiller is preferably increased to the low pressure of the evaporator in order to reduce the cooling capacity of the chiller by controlling the refrigerant compressor. This would give the same operating situation as without the third expansion device.

According to another preferred embodiment of the invention, when the low pressure of the chiller corresponds to the low pressure of the interior evaporator, a maximum cooling capacity is generated at the chiller if the state of the refrigerant at the refrigerant outlet of the chiller is set close to its dew line. The maximum performance of the chiller is therefore achieved with minimal overheating of the refrigerant at the refrigerant outlet of the chiller, tending to shift even more in the direction of the two-phase area of the refrigerant However, these points cannot be recorded by the system and therefore cannot be set stably

In this embodiment of the invention, the cooling capacity of the chiller is preferably reduced by increasing the overheating of the refrigerant by means of the first expansion element at a constant pressure in the interior evaporator when the low pressure of the chiller corresponds to the low pressure of the interior evaporator.

If a system with a refrigerant collector on the high-pressure side is used, for the parallel operation of the at least two evaporators (interior evaporator, chiller), a pressure-temperature sensor must be connected downstream of the corresponding evaporator in order to be able to separately record and actively influence the respective refrigerant states in this way. If it is impossible for the respective evaporators to be operated in parallel, one of the two pressure-temperature sensors can be dispensed with and a remaining pressure-temperature sensor can be installed downstream in the area of the connection point of the two evaporator branches.

In the system with a refrigerant collector on the low-pressure side, in addition to the pressure-temperature sensor after the refrigerant collector for leak detection, another pressure-temperature sensor is provided after the at least two evaporators (interior evaporator, chiller), but at least as many pressure-temperature sensors as there are evaporators reduced by one counting unit, so at least one additional pressure-temperature sensor is used in a two-evaporator system. If it is also ruled out here that the at least two evaporators are operated in parallel, then preferably only the one pressure-temperature sensor downstream of the low-pressure-side refrigerant collector can be used. As a result, only one evaporator (chiller or interior evaporator) is active at a time.

• 1 eine Schaltungsanordnung eines Kältemittelkreislaufs zur Durchführung eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens unter Verwendung eines niederdruckseitig angeordneten Kältemittelsammlers,
• 2 eine zur Schaltungsanordnung nach 1 alternative Schal-, tungisanordnung zur Durchführung eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens unter Verwendung eines hochdruckseitig angeordneten Kältemittelsammlers, und
• 3 eine weitere zur Schaltungsanordnung nach 1 alternative Schaltungsanordnung zur Durchführung eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens ausgestattet mit einem dritten Expansionsorgan.

Further advantages, features and details of the invention result from the following description of preferred embodiments and from the drawings. show:

• 1 a circuit arrangement of a refrigerant circuit for carrying out an exemplary embodiment of the method according to the invention using a refrigerant collector arranged on the low-pressure side,
• 2 one for the circuit arrangement 1 alternative circuit arrangement for carrying out an exemplary embodiment of the method according to the invention using a refrigerant collector arranged on the high-pressure side, and
• 3 another for the circuit arrangement 1 alternative circuit arrangement for carrying out an embodiment of the method according to the invention equipped with a third expansion element.

the 1 until 3 For the sake of simplicity, FIG. The functional extension with regard to a Vllärmepumpebetrieb was dispensed with, since the basic idea for the description of the method can already be fully represented with the simple interconnection concept. These refrigerant circuits 10 have an identical basic structure and each differ in the arrangement of a refrigerant collector as a low-pressure or high-pressure refrigerant collector.

• - einem Kältemittelverdichter 3,
• - einem äußeren Kondensator 4 oder Gaskühler 4, welcher mit dem Hochdruckausgang des Kältemittelverdichters 3 fluidverbunden ist,
• - einem Chiller-Zweig 1.0 mit einem zur Kühlung einer elektrischen Komponente (bspw. eine Hochvoltbatterie, eine elektrische Antriebskomponente usw.) des Fahrzeugs vorgesehenen Chiller 1, einem dem Chiller 1 vorgeschalteten und als elektrisches Expansionsventil ausgebildeten ersten Expansionsorgan AE1 und einem dem Chiller 1 nachgeschalteten ersten Druck-Temperatursensor pT1, wobei der Chiller 1 mit einem Kühlmittelkreislauf 1.1 zur Kühlung der elektrischen Komponente thermisch gekoppelt ist,
• - einem Innenraum-Verdampferzweig 2.0 mit einem Innenraum-Verdampfer 2 und einem demselben vorgeschalteten und mit einer Absperrfunktion ausgeführten zweiten Expansionsorgan AE2 wobei der Innenraum-Verdampferzweig 2.0 dem Chiller-Zweig 1.0 parallel geschaltet ist,
• - einem Kältemittelsammler 6.1 bzw. 6.2, der gemäß den 1 und 3 als Niederdruck-Kältemittelsammler 6.1 mit einem nachgeschalteten zweiten Druck-Temperatursensor pT2 dem Chiller-Zweig 1.0 und dem Innenraum-Verdampferzweig 2.0 stromabwärts nachgeschaltet ist und der gemäß 2 als Hochdruck-Kältemittelsammler 6.2 dem äußeren Kondensator 4 oder Gaskühler 4 stromabwärts nachgeschaltet ist,
• - einem inneren Wärmeübertrager 5, dessen Hochdruckseite den Kondensator 4 oder Gaskühler 4 mit dem Chiller-Zweig 1.0 und dem Innenraum-Verdampferzweig 2.0 fluidverbindet, während dessen niederdruckseitiger Abschnitt gemäß den 1 und 3 zwischen dem Niederdruck-Kältemittelsammler 6.1 und dem Kältemittelverdichter 3 in den Kältemittelkreislauf 10 und gemäß 2 zwischen dem Chiller-Zweig 1.0 und dem Kältemittelverdichter 3 eingebunden ist,
• - einem dem Kondensator 4 oder Gaskühler 4 nachgeschalteten dritten Druck-Temperatursensor pT3,
• - einem dem Kältemittelverdichter 3 nachgeschalteten vierten Druck-Temperatursensor pT4,
• - einem gemäß den 2 und 3 dem Innenraum-Verdampfer 2 stromabwärts nachgeschalteten fünften Druck-Temperatursensor pT5, und
• - einem gemäß 2 der Parallelschaltung des Chiller-Zweiges 1.0 und des Innenraumverdampfers 2.0 stromabwärts optional in Abhängigkeit der Betriebsstrategie nachgeschalteten sechsten Druck-Temperatursensor pT6.

The refrigerant circuit 10 according to 1 until 3 consists of the following components:

• - a refrigerant compressor 3,
• - an external condenser 4 or gas cooler 4, which is fluidly connected to the high-pressure outlet of the refrigerant compressor 3,
• - a chiller branch 1.0 with a chiller 1 provided for cooling an electrical component (e.g. a high-voltage battery, an electric drive component, etc.) of the vehicle, a first expansion element AE1 connected upstream of the chiller 1 and designed as an electric expansion valve, and a first expansion element AE1 connected downstream of the chiller 1 first pressure-temperature sensor pT1, the chiller 1 being thermally coupled to a coolant circuit 1.1 for cooling the electrical component,
• - an interior evaporator branch 2.0 with an interior evaporator 2 and a second expansion element AE2 connected upstream of the same and designed with a shut-off function, the interior evaporator branch 2.0 being connected in parallel with the chiller branch 1.0,
• - A refrigerant collector 6.1 or 6.2, which according to the 1 and 3 as a low-pressure refrigerant collector 6.1 with a downstream second pressure-temperature sensor pT2 downstream of the chiller branch 1.0 and the interior evaporator branch 2.0 and according to 2 is connected downstream of the outer condenser 4 or gas cooler 4 as a high-pressure refrigerant collector 6.2,
• - An internal heat exchanger 5, the high-pressure side of which fluidly connects the condenser 4 or gas cooler 4 to the chiller branch 1.0 and the interior evaporator branch 2.0, while the low-pressure-side section according to the 1 and 3 between the low-pressure refrigerant collector 6.1 and the refrigerant compressor 3 in the refrigerant circuit 10 and according to 2 is integrated between the chiller branch 1.0 and the refrigerant compressor 3,
• - a third pressure-temperature sensor pT3 downstream of the condenser 4 or gas cooler 4,
• - a fourth pressure-temperature sensor pT4 downstream of the refrigerant compressor 3,
• - one according to the 2 and 3 fifth pressure-temperature sensor pT5 downstream of interior evaporator 2, and
• - according to one 2 the parallel connection of the chiller branch 1.0 and the interior evaporator 2.0 downstream, optionally depending on the operating strategy, sixth pressure-temperature sensor pT6.

If the high-pressure cold collector 6.2 is integrated into the condenser 4 or gas cooler 4, then the third pressure-temperature sensor pT3 is to be provided downstream of the condenser 4 or gas cooler 4. However, since such systems are generally systems that are intended exclusively for subcritical system operation, the third pressure-temperature sensor pT3 can be omitted.

Finally, for the refrigerant circuit 10 according to 1 until 3 a climate control device is provided as a control unit (not shown in the figures), to which input signals to be processed, such as actual values from pressure-temperature sensors, are fed in order to generate control signals or setpoint values from them as output signals for controlling the individual components of the refrigerant circuit 10.

The interior evaporator branch 2.0 has according to the 1 and 2 a check valve 7 on. At this position, the interior evaporator branch 2.0 is in accordance with 3 formed with a third expansion element AE3.

First, the single chiller operation of the refrigerant circuit 10 according to the 1 until 3 described, in which only the chiller 1 is operated for exclusive component cooling (e.g. the high-voltage battery) and for this purpose the interior evaporator branch 2.0 is blocked by means of the second expansion element AE2.

In such a single chiller operation of the refrigerant circuit 10 according to 1 and 3 the refrigerant compressed to high pressure flows from the refrigerant compressor 3 into the outer condenser 4 or gas cooler 4, then into the high-pressure section of the inner heat exchanger 5 and is then expanded into the chiller branch 1.0 by means of the first expansion element AE1. The refrigerant flows from the chiller branch 1.0 via the low-pressure refrigerant collector 6.1 and the low-pressure section of the internal heat exchanger 5 back to the refrigerant compressor 3. Here, the heat transferred from the refrigerant circuit 1.1 to the refrigerant is transferred to the condenser 4 or the gas cooler 4 transferred to the ambient air of the vehicle.

The low-pressure refrigerant collector 6.1 of the refrigerant circuit 10 has the task of separating the gaseous and liquid phases of the incoming refrigerant and storing or circulating the liquid refrigerant in the sense of a volume buffer, depending on the amount of refrigerant required by the system. The refrigerant sucked out of the low-pressure refrigerant collector 6.1 into the downstream low-pressure-side section of the internal heat exchanger 5 to the refrigerant compressor 3 should have as high and defined a vapor content as possible. Practical values range between 80-95%. Values below mean that the refrigerant is too wet and there is a risk of the oil being washed out on the refrigerant compressor 3; values above this can impair the oil return transport to the refrigerant compressor 3.

Furthermore, the lubricating oil introduced by the refrigerant compressor 3 into the refrigerant circuit 10 and stored, among other things, in the low-pressure refrigerant collector 6.1 is to be returned to the refrigerant compressor 3 by means of the low-pressure refrigerant collector 6.1. For this purpose, for example, a U-shaped (outlet) pipe is integrated in the low-pressure refrigerant collector 6.1, which has an oil hole (also called a snifting hole) at the lowest point. An open end of the U-tube extends into the vapor space of the low-pressure refrigerant collector 6.1 above the liquid refrigerant, the other (inlet) tube leads upstream into the suction line to the chiller 1 Suction of oil or oil-refrigerant liquid mixture from the lower area of the low-pressure refrigerant collector 6.1. Depending on the size of the inner bore, a vapor content of, for example, 90% occurs at the outlet of the low-pressure refrigerant collector 6.1. If the oil hole is too small, the vapor content increases, remaining increases oil and oil collects in the lower area of the low-pressure refrigerant collector 6.1, while if the oil bore is too large, the vapor content decreases and the ejected liquid fraction increases.

Such a low-pressure refrigerant collector 6.1 regulates the vapor content at the refrigerant outlet of the chiller 1 when the refrigerant circuit 10 is started up or when there is a load change from dual operation of the evaporators (i.e. chiller 1 and interior evaporator 2) to single chiller operation a constant value. The vapor content set by the low-pressure refrigerant collector 6.1 occurs here in the steady state of the refrigerant circuit 10 both at the outlet of the chiller 1 and at the refrigerant outlet of the low-pressure refrigerant collector 6.1. The refrigerant state at the refrigerant outlet of the chiller 1 is thus operated close to the dew line due to the explained property of the low-pressure refrigerant collector 6.1 on the curve of the constant vapor content (e.g. 90%). At the same time, this means that the overheating value is zero during regular system operation. The first expansion element AE1 is therefore used either for supercooling control using the third pressure/temperature sensor pT3 or for control to an optimum high pressure, depending on subcritical or supercritical system operation.

Supercooling is controlled in such a way that the pressure and temperature at the outlet of the condenser 4 or gas cooler 4 are recorded via the third pressure, temperature sensor pT3 and the amount of supercooling is determined from the values. If the actual value moves above the target value, the first expansion element AE1 opens until the target value has been reached. If the actual value is less than the setpoint, the first expansion element AE1 is closed until the setpoint is set.

Controlling for an optimum high pressure means that the pressure and temperature at the outlet of the condenser 4 or gas cooler 4 are recorded via the third pressure-temperature sensor pT3 and the amount of the desired high pressure is determined from the values. If the actual value moves above the setpoint, the first expansion element AE1 opens until the setpoint is reached. If the actual value is less than the setpoint, the first expansion element AE1 is closed until the setpoint is set.

Is in the refrigerant circuit 10 according to 1 the function of underfilling detection is implemented by means of the second pressure-temperature sensor pT2, the first pressure-temperature sensor pT1 is not required in single-chiller mode because, as explained above, the pressure at the outlet of the low-pressure refrigerant collector 6.1 and at the refrigerant outlet of the chiller 1 is almost the same temperature conditions are present. If, in addition, the operation of the chiller 1 is always strictly separated from the operation of another evaporator, ie the interior evaporator 2, a refrigerant circuit 10 according to FIG 1 the first pressure-temperature sensor pT1 can be dispensed with. The use of this first pressure-temperature sensor pT1 is absolutely necessary if parallel operation of at least two evaporators, ie the chiller 1 and the interior evaporator 2, is provided. The minimum number of required pressure-temperature sensors downstream of the evaporators used corresponds to the number of evaporators reduced by the counter value 1.

In the single chiller mode, in particular also depending on the flow temperature of the coolant in the chiller 1, when controlling for subcooling or for an optimal high pressure, there are significantly higher low pressures in the refrigerant circuit 10 compared to multiple evaporator operation using the chiller 1 and the interior -evaporator 2 on. Especially at high flow temperatures in the cooling water of the coolant circuit 1.1 of the chiller 1, high values are achieved in the low pressure, which decrease with falling flow temperature or with an increase in the desire for cooling (differential temperature between the water flow and the return). The low pressure in the refrigerant circuit 10 increases, in particular, when the flow temperature of the coolant at the chiller 1 increases.

With the increasing low pressure of the refrigerant, its density also increases and thus leads to an increased requirement for refrigerant in the low-pressure section of the refrigerant circuit 10, i. H. there is a refrigerant undercharge. In the single chiller mode, the refrigerant at the refrigerant outlet of the chiller 1 can no longer be operated in the two-phase region of the refrigerant and thus close to the dew line when the low-pressure refrigerant collector 6.1 is empty, i.e. can no longer supply refrigerant and its reservoir is exhausted . The low-pressure refrigerant collector 6.1 empties, the refrigerant at the refrigerant outlet of the chiller 1 is increasingly overheated, and thus also at the outlet of the low-pressure refrigerant collector 6.1.

With the increasing density of the refrigerant and thus the mass flow, a torque overload on the refrigerant compressor 3 can also occur.

As soon as such a torque overload of the refrigerant compressor 3 and/or increasing overheating of the refrigerant at the refrigerant outlet of the chiller 1 is detected by means of the first pressure-temperature sensor pT1 (or possibly by means of the second th pressure-temperature sensor pT2) is detected, a control intervention on the refrigerant compressor 3, which is designed as an electric compressor, lowers the low pressure by adjusting the speed of the refrigerant compressor 3 and thus the cooling capacity. The lowering of the low pressure takes place as a function of the ambient conditions and the load case on chiller 1, ie the low pressure in the system is reduced until the overheating or torque problem is no longer detected. With this upper limit of the maximum permissible low pressure, the degree of freedom of the low pressure, namely to increase in any way, is restricted.

The torque overload of the refrigerant compressor 3 is detected by self-diagnosis if the refrigerant compressor 3 is designed as an electric refrigerant compressor. For this purpose, a corresponding diagnostic signal is made available by such an electric refrigerant compressor, which is evaluated by a control unit, for example an air conditioning control unit.

Another negative property that can occur in connection with increasing overheating is expressed in the worsening of the oil return transport to the refrigerant compressor 3, since the oil is now increasingly stored in the low-pressure refrigerant collector 6.1 and due to the lack of a liquid refrigerant phase with which the oil a mixture is received, the transport medium to the refrigerant compressor 3 is no longer available

Alternatively, the low pressure is limited to a maximum low pressure value by controlling the refrigerant compressor 3 so that a further increase in the low pressure at the refrigerant outlet of the chiller 1 is prevented. The maximum low pressure value is determined depending on the ambient conditions and the cooling capacity of chiller 1, i. H. When the refrigerant circuit 10 starts up, the evaporation temperature should be set to a value below the ambient temperature or should initially be based on this and, over the course of the operation, the efficiency-optimal operating point should be approached again, taking into account the values at the first pressure-temperature sensor pT1.

With the reduction of the low pressure, the evaporation temperature of the refrigerant in the chiller 1 is also reduced. In order to restore the refrigeration capacity of the chiller 1 generated before the low pressure was reduced, this refrigeration capacity is restored by the interaction of the refrigerant compressor 3 and the first expansion element AE1 by increasing the stroke or speed and moving the first expansion element AE1, i. H. usually responds to the new boundary conditions by further throttling. It must be taken into account that situations can arise in which the system can work independently of subcooling control or control of the optimum high pressure. and must, otherwise an excess of cooling capacity cannot be avoided. The efficient control of the refrigerant circuit 10 by means of the supercooling control or the control to the optimum high pressure, which was carried out before the low pressure was reduced, is therefore suspended until new low pressure levels are set, in particular due to changed, but specifically lower, coolant flow temperatures at the chiller 1, thereby enabling a return to efficient system operation i.e. the refrigerant compressor 3 ensures the stroke or the amount of cooling of the refrigerant, the first expansion element AE1 sets the supercooling or the optimum high pressure.

In a single chiller operation of the refrigerant circuit, 10 according to 2 the refrigerant compressed to high pressure flows from the refrigerant compressor 3 into the outer condenser 4 or gas cooler 4, then into the high-pressure refrigerant collector 6.2 and then into the high-pressure section of the inner heat exchanger 5, and then by means of the first expansion element AE1 into the chiller branch 1.0 to be relaxed. From the chiller branch 1.0, the refrigerant flows back to the refrigerant compressor 3 via the low-pressure section of the internal heat exchanger,5 transferred to the ambient air of the vehicle.

The condenser 4 can also be designed with an integrated high-pressure refrigerant collector 6.2; as a rule, the high-pressure refrigerant collector 6.2 is followed downstream by a sub-cooling section consisting of a few flat tubes and integrated into the ambient heat exchanger, at the outlet of which the high-pressure-side section of the internal heat exchanger 5 is connected downstream.

In this single chiller mode, the overheating at the refrigerant outlet of the chiller 1 in a refrigerant circuit 10 is shown in FIG 2 also operated close to the dew line of the refrigerant by controlling the overheating to a value between 3 and 5 K by means of the first expansion element AE1, the degree of overheating being detected by means of the first pressure-temperature sensor pT1. At a maximum cooling capacity requirement for the chiller 1, the first expansion element AE1, designed as an electric expansion valve set to a minimum but still reliably detectable overheating value.

In the single chiller mode, significantly higher low pressures occur in the refrigerant circuit 10 with such a regulation in comparison to multiple evaporator operation using the chiller 1 and the interior evaporator 2 . The low pressure in the refrigerant circuit 10 rises in particular with an increasing coolant flow temperature at the inlet of the chiller 1 .

With the increasing low pressure of the refrigerant, its density also increases and thus leads to an increased demand for refrigerant in the low-pressure section of the refrigerant circuit, i.e. there is insufficient refrigerant. Thus, in the single chiller mode, the refrigerant at the refrigerant outlet of the chiller 1 can no longer be operated close to the dew line, since the refrigerant at the refrigerant outlet of the chiller 1 is increasingly overheated due to the refrigerant underfill.

A torque overload on the refrigerant compressor 3 can also occur with the increasing density of the refrigerant.

As soon as such a torque overload of the refrigerant compressor 3 and/or increasing overheating of the refrigerant at the refrigerant outlet of the chiller 1 is detected by the first pressure-temperature sensor pT1, a control intervention on the refrigerant compressor 3, which is designed as an electric compressor, lowers the low pressure by reducing the speed of the refrigerant compressor 3 and thus the cooling capacity is reduced. The low pressure is reduced depending on the ambient conditions and the load case on chiller 1, i.e. the low pressure in the system is reduced until the overheating phenomenon and/or the torque overload are no longer detected. With the upper limit of the maximum permissible low pressure, the degree of freedom of the low pressure to increase in any way is restricted.

At the outlet of the interior evaporator 2, the pressure-temperature sensor pT5 is responsible for monitoring the overheating control of the refrigerant at the outlet of the interior evaporator 2.

The torque overload of the refrigerant compressor 3 is detected by self-diagnosis if the refrigerant compressor 3 is designed as an electric refrigerant compressor. For this purpose, a corresponding diagnostic signal is made available by such an electric refrigerant compressor, which is evaluated by a control unit, for example an air conditioning control unit.

Alternatively, the low pressure is limited to a maximum low pressure value by controlling the refrigerant compressor 3 so that a further increase in the low pressure at the refrigerant outlet of the chiller 1 is prevented. The maximum low pressure value is determined depending on the ambient conditions and the cooling capacity of the chiller 1, i. H. When the refrigerant circuit 10 starts up, the evaporation temperature should be set to a value below the ambient temperature or should initially be based on this and, over the course of the operation, the efficiency-optimal operating point should be approached again, taking into account the values at the first pressure-temperature sensor pT1.

With the reduction of the low pressure, the evaporation temperature of the refrigerant in the chiller 1 is also reduced. In order to restore the refrigeration capacity of the chiller 1 generated before the low pressure was reduced, this refrigeration capacity is restored by the interaction of the refrigerant compressor 3 and the first expansion element AE1 by increasing the stroke or speed and moving the first expansion element AE1, i. H. usually responds to the new boundary conditions by further throttling. It must be taken into account that there can be situations in which the system can and must work independently of subcooling control or control of the optimum high pressure, as otherwise an excess of cooling capacity cannot be avoided. The efficient control of the refrigerant circuit 10 by means of the supercooling control or the control to the optimum high pressure, which was carried out before the low pressure was reduced, is therefore suspended until new low pressure levels are set, in particular due to changed, but specifically lower, coolant flow temperatures at the chiller 1, thereby enabling a return to efficient system operation i.e. the refrigerant compressor 3 ensures the lift or the amount of cooling of the refrigerant, the first expansion element AE1 sets the subcooling or the optimum high pressure.

It should be added that if chiller 1 and interior evaporator 2 are always operated separately, i.e. both heat exchangers are never operated simultaneously, the two pressure-temperature sensors pT1 and pT5 are omitted and replaced by a pressure-temperature sensor pT6 downstream of the chiller node branch 1.0 and the interior evaporator branch 2.0 can be replaced.

A further advantage of the method according to the invention for reducing the low pressure upon detection of a torque overload on the refrigerant compressor 3 and/or an increasing Overheating of the refrigerant at the refrigerant outlet of the chiller 1 is not only to avoid switching off the refrigerant compressor 3 in the event of a torque overload, but also to ensure the oil transport and sufficient lubrication of the refrigerant compressor 3 and thus also an increased component service life of the refrigerant compressor 3.

Finally, with the method according to the invention, operation of the refrigerant circuit 10 in the area of a critical filling quantity in the sense of a potential underfilling of refrigerant is avoided.

That in the 1 and 2 The check valve 7 downstream of the interior evaporator 2 prevents refrigerant from moving into the interior evaporator 2 in the single chiller mode. In the refrigerant circuit 10 according to FIG 3 this function is taken over by the third expansion element AE3.

In the following, a multiple evaporator operation, ie a parallel operation of the chiller 1 and the interior evaporator 2 of the refrigerant circuits 10 according to 1 until 3 described.

With such a multiple evaporator operation, the interior evaporator 2 becomes the reference variable of the refrigeration process and specifies the level of the low pressure and thus the required evaporation temperature. In a refrigerant circuit 10 according to 1 This means that a certain constant vapor content at the outlet of the low-pressure refrigerant collector 6.1 and thus also at the refrigerant outlet of the interior evaporator 2 is set by means of the low-pressure refrigerant collector 6.1. Using the first expansion element AE1, an overheating dependent on the power requirement or a minimum minimum overheating for maximum power at the refrigerant outlet of the chiller 1 is always set to set a specific refrigerant mass flow flowing through the chiller 1, in order to achieve a defined cooling of the water temperature of the coolant circuit 1.1.

Also in the refrigerant circuit 10 with the high-pressure refrigerant collector 6.2, a defined cooling of the water temperature is regulated via the first expansion element AE1 of the chiller 1, which is set via the refrigerant mass flow flowing through the chiller 1.

Alternatively, the refrigerant circuit 10 according to 1 can also be operated with a third expansion device AE3, like this the 3 indicates. This third expansion element AE3 belongs to the interior evaporator branch 2.0 and is connected downstream of the interior evaporator 2 . The refrigerant state within the interior evaporator branch 2.0 can be detected via a pressure-temperature sensor pT5 provided downstream of the interior evaporator 2; alternatively, an air temperature sensor T _{air_} downstream of the interior evaporator 2 on the air outlet side can also be used for this purpose.

This third expansion element AE3, which is designed as an electrically or mechanically controllable expansion valve, ensures that the low pressure in the interior evaporator branch 2.0 does not fall below a level that would lead to icing.

A medium-pressure level can thus be set in the interior evaporator branch 2.0, while any desired low-pressure level below the low-pressure level in the evaporator branch 2.0 is set on the chiller 1 by means of the refrigerant compressor 3 depending on the required cooling capacity of the chiller 1 . For this purpose, the overheating at the refrigerant outlet of the chiller 1 is adjusted by means of the first expansion element AE1, whereby the cooling capacity at the chiller 1 can be varied depending on the degree of overheating at the refrigerant outlet of the chiller 1 at the respective prevailing low pressure. In this case, the maximum cooling capacity of the chiller 1 is achieved when the refrigerant is set close to the dew line of the refrigerant at its refrigerant outlet.

When the low pressure of the chiller 1 is lower than the low pressure of the interior evaporator 2, to increase the cooling capacity of the chiller 1, the refrigerant at the refrigerant outlet of the chiller 1 is close to its dew line, i. H. operated with low overheating and the interior evaporator 2 operated by means of the third expansion element AE3 at a medium-pressure level. To reduce the cooling capacity of the chiller 1, the low pressure of the chiller 1 is raised to the low pressure of the interior evaporator 2 by controlling the refrigerant compressor 3. By further throttling the first expansion element AE1, the refrigerating capacity at the chiller 1 can also be reduced.

When the low pressure of the chiller 1 corresponds to the low pressure of the interior evaporator 2, a maximum cooling capacity is generated at the chiller 1 if the refrigerant in the refrigerant outlet of the chiller 1 is operated close to its dew line, ie with minimal overheating. The cooling capacity of the chiller 1 is reduced by increasing the overheating of the refrigerant by means of the first expansion element AE1 at a constant pressure in the interior evaporator 2 .

In a refrigerant circuit 10 according to 1 until 3 can at least one other inside room evaporator, e.g. However, it is particularly advantageous to connect this further expansion element to the second expansion element AE2 of the interior evaporator 2 upstream.

In the refrigerant circuit 10 according to the 1 until 3 Instead of the first expansion element AE1 designed as an electric expansion valve, in single chiller mode this can also be designed as a thermal expansion element that can be switched off or as an orifice tube with a defined opening cross section that can be switched off. The exact setting of the coolant temperature of the coolant circuit 1.1 of the chiller 1 must therefore be set by means of a clocked operation of the expansion element around the target value of the coolant discharge temperature at the chiller.

In connection with the high-pressure refrigerant collector 6.2, it should be noted that the collector bottle can also be integrated into the condenser 4 before it flows through the sub-cooling section integrated into the condenser 4 downstream. In this constellation, which cannot be used in this design for the design as an air heat pump, the third pressure-temperature sensor pT3 can be omitted, since the condenser 4, in which the high-pressure refrigerant collector 6.2 and the sub-cooling section are integrated, already automatically sub-cools the refrigerant .

Furthermore, the methods described can also be implemented in a refrigerant circuit 10 with a heat pump function.

Finally, the methods described can be used for all known refrigerants, such as R744, R134a, R1234yf, etc., whereby only the low-pressure refrigerant collector 6.1 is taken into account specifically for the R744 system.

Reference List

1

Refrigerant circuit chiller 10

1.0

chiller branch

1.1

Chiller coolant circuit 1

2

interior evaporator

2.0

Interior evaporator branch

3

refrigerant compressor

4

condenser or gas cooler

5

internal heat exchanger

6.1

Low pressure refrigerant collector

6.2

High-pressure refrigerant collector

7

check valve

10

Refrigerant circulation

AE1

first expansion organ

AE2

second expansion organ

AE3

third expansion organ

pT1

pressure-temperature sensor

pT2

pressure-temperature sensor

pT3

pressure-temperature sensor

pT4

pressure-temperature sensor

pT5

pressure-temperature sensor

pT6

pressure-temperature sensor

Tair

air temperature sensor

Claims (10)

Method for operating a refrigerant circuit (10) of a refrigeration system of a vehicle - a chiller branch (1.0), which has a chiller (1), a first expansion element (AE1) and a first pressure-temperature sensor (pT1) downstream of the chiller (1) and is thermally coupled to a coolant circuit (1.1), - at least one interior evaporator branch (2.0), which has an interior evaporator (2) and a second expansion element (AE2) and is connected in parallel to the chiller branch (1.0), - a refrigerant compressor (3), and - A condenser or gas cooler (4), wherein - in a single chiller mode, the operating point of the refrigerant circuit (10) is set at the refrigerant outlet of the chiller (1) close to the dew line of the refrigerant, - the low pressure and the associated temperature of the refrigerant is detected by means of the first pressure-temperature sensor (pT1) of the chiller (1), and - the low pressure is limited by controlling the refrigerant compressor (3) to a maximum low pressure value that depends on the ambient conditions and the required cooling capacity of the chiller (1) or is lowered with a reduction in the cooling capacity on the chiller (1) if there is a torque overload on the refrigerant compressor (3) or a specified deviation of the temperature from the dew line of the refrigerant is detected at the refrigerant outlet of the chiller (1). procedure after claim 1 , in which following the lowering of the low pressure, the cooling capacity at the chiller (1) by means of a control of the first expansion element (AE1) together with the refrigerant compressor (3) is adjusted back to the target cooling capacity. procedure after claim 1 or 2 , in which - the refrigerant circuit (10) is designed with a low-pressure refrigerant collector (6.1) with which defined refrigerant vapor contents can be adjusted, and - the refrigerant for adjustment to its dew line or near the dew line in the two-phase area of the refrigerant by means of the low-pressure refrigerant collector (6.1) is set to an overheating level of 0 K. procedure after claim 1 , in which - the refrigerant circuit (10) is designed with a high-pressure refrigerant collector (6.2), and - the refrigerant is adjusted to or near its dew line by means of the first first expansion element (AE1) to a degree of overheating with a value between 3 and 5 K is regulated. Method according to one of the preceding claims, in which, in a chiller and evaporator operation, a third expansion element (AE3) is connected downstream of the interior evaporator (2), wherein - the interior evaporator (2) is operated at a medium-pressure level, and - The chiller (1) is operated at a low-pressure level depending on the required cooling capacity by controlling the refrigerant compressor (3) and the first expansion device (AE1). procedure after claim 5 , in which, when the low pressure of the chiller (1) is lower than the low pressure of the interior evaporator (2), in order to increase the cooling capacity of the chiller (1), - the refrigerant state at the refrigerant outlet of the chiller (1) is set close to its dew line, and - the interior evaporator (2) is operated at a medium-pressure level by means of the third expansion element (AE3). procedure after claim 5 or 6 , in which to reduce the cooling capacity of the chiller (1) by controlling the refrigerant compressor (3), the low pressure of the chiller (1) is raised to the low pressure of the interior evaporator (2). Procedure according to one of Claims 5 until 7 , at which at a low pressure of the chiller (1) corresponding to the low pressure of the interior evaporator (2) a maximum cooling capacity is generated at the chiller (1) if the state of the refrigerant at the refrigerant outlet of the chiller (1) is set close to its dew line . procedure one of Claims 5 until 8th , in which, when the low pressure of the chiller (1) corresponds to the low pressure of the interior evaporator (2), the cooling capacity of the chiller (1) is increased by increasing the overheating of the refrigerant by means of the first expansion element (AE1) at a constant pressure in the interior evaporator ( 2) is reduced. Procedure according to one of claims 3 until 9 , in which, when the interior evaporator (2) or the chiller (1) is operated exclusively - in a refrigerant circuit (10) with a low-pressure refrigerant collector (6.1) instead of the first low-pressure sensor (pT1), a pressure-temperature sensor (pT2) is installed on the downstream side of the chiller branch (1.0), the interior evaporator branch (2.0) and downstream of the low-pressure cold collector (6.1), and - in a refrigerant circuit (10) with a high-pressure refrigerant collector (6.2) instead of the first low-pressure sensor ( pT1) a pressure-temperature sensor (pT6) is arranged downstream of the chiller branch (1.0) and the interior evaporator branch (2.0).

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