DE102020115276A1 - Method for regulating a compression refrigeration system and a compression refrigeration system - Google Patents

Abstract

The present invention relates to a method for regulating a compression refrigeration system (200) and an associated compression refrigeration system (200). The method comprises the following steps: determining an oil sump temperature situation that is critical for the operation of the compressor as a function of an operating point of the compression refrigeration system and performing rapid oil sump heating by temporarily or permanently increasing a setpoint value for overheating (TÜE) of the refrigerant upon entry into the compressor (210) and / or a speed of the compressor in the event of a critical oil sump temperature situation.

Description

The invention relates to a method for operating a compression refrigeration system and an associated compression refrigeration system with a refrigerant, an evaporator, a compressor, a condenser, a throttle element and a control unit for detecting overheating of the refrigerant when it enters the compressor, the overheating being a difference of a Dew point temperature is defined for a temperature of the refrigerant, and for regulating the throttle element based on the overheating,

Such compression refrigeration systems, for example in the form of heat pumps, with a vapor compression system in which a gaseous refrigerant is compressed from a low pressure to a high pressure by a compressor controlled by means of the control unit, which for example has a regulator, are known.

The refrigerant is driven through the condenser, in which it gives off heat to a heating medium located in a heat sink system. Internal heat is transferred in an internal heat exchanger, for example in the form of a recuperator, between the refrigerant flowing under high pressure from the condenser to the expansion valve and the refrigerant flowing from the evaporator to the compressor under low pressure.

The refrigerant is guided further in a high-pressure flow direction to an expansion valve controlled by the regulator, in which the refrigerant is expanded from high pressure to low pressure as a function of a control value. The refrigerant at the low pressure evaporates in the evaporator when it absorbs source heat.

Out DE 101 59 892 A1 It is known to use a recuperator in a refrigeration machine, in particular in a heat pump, which is intended to increase the heating power in a structurally simple manner at low outside temperatures. For this purpose, the recuperator is dimensioned in such a way that at low evaporation temperatures it transfers at least around 15% of the heat output of the heat pump from the liquid refrigerant to the gaseous refrigerant. An injection valve injects liquid refrigerant into the compressor so that the compression end temperature remains below 120 ° C.

A heat pump system with a refrigerant circuit is off DE 10 2005 061 480 B3 known. It is equipped with a compressor, a first heat exchanger, a throttle element, an evaporator and a 4-2-way valve unit for switching between a first (heating) and a second operating mode (cooling). A direction of flow of the refrigerant in the refrigerant circuit can be switched so that the first heat exchanger is used to liquefy the refrigerant in the first operating mode and to evaporate the refrigerant in the second operating mode, and the second heat exchanger in the first operating mode to evaporate the refrigerant and in the second operating mode is used to liquefy the refrigerant, the first heat exchanger in the refrigerant circuit being connected in such a way that it works as a countercurrent heat exchanger in the two operating modes heating and cooling.

Oil, which is typically already contained in the compressor, is provided on site in the refrigerant circuit, also known as the refrigeration circuit. Usually an oil reservoir is located at a low position (gravity) of the compressor. The oil is conveyed to the compressor components to be lubricated, for example via a displacement or centrifugal pump, and lubricates the compression chambers, for example.

If the compression refrigeration system is not operated for a longer period of time, the temperature of the compressor drops to the ambient temperature. When the compressor is started, warmer refrigerant can hit the oil, which is also at ambient temperature, and condense.

If the oil becomes saturated with condensing refrigerant, it loses its technical lubricating properties. For this reason, when the compressor is started, it must be ensured that the amount of refrigerant that has condensed out is negligible or harmless.

It is known to have an electrical preheating, for example a heating tape, for preheating from the outside in order to wind the compressor. The significant electrical effort required to preheat the oil is costly and reduces the coefficient of performance of the compression refrigeration system.

Against this background, it was an object of the present invention to create an improved method for ensuring the lubricating properties of the oil when the compressor is started.

We solved the problem by the method features of claim 1 and the device features of claim 8.

In a first aspect, a method for regulating a compression refrigeration system with a refrigeration circuit is proposed. The refrigeration circuit contains a refrigerant, an evaporator, a compressor with an oil sump, a condenser, a throttle element and a control unit. The control unit is set up to detect overheating of the refrigerant when it enters the compressor, the overheating being defined as a difference between a dew point temperature and a temperature of the refrigerant, for regulating the throttle element based on the overheating, and for monitoring and controlling oil heating of the oil sump of the compressor . The method comprises the following steps: determining an oil sump temperature situation that is critical for the operation of the compressor as a function of an operating point of the compression refrigeration system and performing rapid oil sump heating by temporarily or permanently increasing a setpoint value for superheating of the refrigerant when entering the compressor and / or a speed of the compressor in the event of a critical oil sump temperature situation.

According to the invention, a method is therefore proposed that implements an additional regulator function for monitoring and controlling rapid oil heating in the event of changes in operating conditions.

The compressor can be either a suction gas-encapsulated compressor in which the compressor capsule and thus also the oil are at low pressure or compressor inlet pressure, or a compressed gas-encapsulated compressor in which the compressor capsule and the oil are at high pressure.

The rapid heating of the oil sump ensures that, for example, when the compressor starts, the amount of refrigerant that has condensed out is negligible or harmless. Instead of, for example, an electrical heating band for preheating, a more efficient oil heating system is accordingly proposed according to the invention.

To determine the critical oil sump temperature situation, a sensor arranged on the compressor pressure capsule (outside) can be provided, for example.

The rapid oil sump heating advantageously includes operating the compressor at a minimum speed.

The higher the speed of the compressor, the better the sliding on the oil film of the bearing is guaranteed. The higher speed therefore reduces the risk of an oil film tearing off. In addition, the heating-up time is reduced by a power greater than 1, depending on the speed. An increased speed accordingly ensures a disproportionately reduced heating-up time.

The compressor is preferably operated at at least the minimum speed until the oil in the compressor reaches a minimum temperature.

In addition or as an alternative, electrical preheating can also be provided. Compared to known solutions, this can be designed to be lower and therefore already lead to an increase in the coefficient of performance. It is particularly preferred that no electrical preheating at all is necessary.

According to this aspect, the compressor is operated at minimum speed until the temperature required for safe operation without excessive refrigerant entry into the oil is reached. In comparison with an (electrical) heating tape, a much more efficient expulsion of the refrigerant is made possible.

A speed of the compressor is preferably set as a function of the oil temperature during the rapid heating of the oil sump.

The speed of the compressor preferably increases as the oil temperature falls.

For example, a controller can regulate with a proportional component between the oil temperature and the compressor speed. The compressor output increases accordingly at lower oil temperatures

An oil sump temperature overheating is preferably defined as the difference between a temperature of the oil in the oil sump and a dew point temperature of the refrigerant, the critical oil sump temperature situation being determined on the basis of the oil sump temperature overheating.

The oil sump temperature overheating ensures that at most a certain proportion, for example 30%, of refrigerant are dissolved in the oil, so that the lubricating properties are guaranteed. The required oil sump temperature overheating increases in particular with a higher dew point level, so it can be represented as a function of the dew point level.

The critical oil sump temperature situation is preferably determined when the oil sump temperature overheating falls below a minimum value, in particular when it falls below 2 K.

The object is also achieved by a compression refrigeration system with a refrigerant, an evaporator, a compressor, a condenser, a throttle element and a control unit. The control unit is used to detect overheating of the refrigerant when it enters the compressor, the overheating being defined as a difference between a dew point temperature and a temperature of the refrigerant, for regulating the throttle element based on the overheating, and for monitoring and controlling oil heating of the oil sump of the compressor. The control is also designed to determine an oil sump temperature situation that is critical for the operation of the compressor as a function of an operating point of the compression refrigeration system and to carry out rapid oil sump heating by temporarily or permanently increasing a setpoint value for overheating of the refrigerant when entering the compressor and / or a speed of the compressor in In the event of a critical oil sump temperature situation.

The refrigerant preferably has a temperature glide, the refrigerant being in particular a mixture of essentially R32 and R1234yf, particularly preferably R454C, is used. In this context, essentially means that it contains at most 10% other components, preferably at most 5% other components and particularly preferably less than 1% other constituents.

The compression refrigeration system preferably has an internal heat exchanger for transferring thermal energy of the refrigerant before it enters the throttle element to the refrigerant before it enters the compressor.

Furthermore, the object is achieved by a heat pump, in particular a heat pump inside a building, with a compression refrigeration system according to the invention.

• 1 Wärmepumpe 100 mit einem Dampfkompressionskreislauf 200
• 2 log p / h - Diagramm des Dampfkompressionsprozesses mit Rekuperator 250
• 3 zeigt schematisch und exemplarisch ein Flussdiagramm eines Verfahrens.

The figures show an exemplary embodiment:

• 1 Heat pump 100 with a vapor compression circuit 200
• 2 log p / h - diagram of the vapor compression process with recuperator 250
• 3 shows schematically and by way of example a flow diagram of a method.

• • Einen Verdichter 210 zum Verdichten des überhitzten Kältemittels,
• • einen Verflüssiger 220, mit einem kältemittelseitigem Verflüssigereintritt 221 und einem Verflüssigeraustritt 222 zur Übertragung von Wärmeenergie Q_H aus dem Dampfkompressionssystem 200 an ein Heizmedium eines Heizsystems 400, mit einem Heizmediumeintritt 401, einem Heizmediumaustritt 402 und einer Heizmediumpumpe 410, zu einer Gebäudeheizung oder ein System zur Warmwassererhitzung,
• • vorteilhaft einen Kältemittelsammler 260, welcher als Kältemittelreservoir zum Ausgleich von betriebsbedingungsabhängig unterschiedlich hohen Kältemittelmengenbedarfen verwendet wird,
• • ein als Expansionsventil ausgebildetes Drosselorgan 230 zum Expandieren des Kältemittels,
• • einen Verdampfer 240, mit einem Verdampfereinlass 241, zur Übertragung von Quellenenergie Q_Q aus einem Wärmequellensystem 300, mit einem Wärmequelleinlass 320 und einem Wärmequellauslass 310, wobei das Wärmequellsystem 300 insbesondere ein Solesystem sein kann, welches Wärmeenergie Q_Q aus dem Erdreich aufnimmt oder ein Luftsystem, welches Wärmeenergie Q_Q aus der Umgebungsluft aufnimmt und an das Dampfkompressionssystem 200 abgibt oder eine beliebige andere Wärmequelle,
• • einen Rekuperator als Beispiel eines internen Wärmeübertragers 250, welcher dazu bestimmt ist, innere Wärmeenergie Q_i zwischen dem vom Verflüssiger 220 zum Expansionsventil 230 strömenden Kältemittel auf das vom Verdampfer 240 zum Verdichter 210 strömende Kältemittel zu übertragen und
• • ein Kältemittel, insbesondere ein Kältemittelgemisch aus wenigsten zwei Stoffen oder zwei Kältemitteln welches in einer Strömungsrichtung S_HD und SND durch den Dampfkompressionskreis 200 strömt, wobei im Dampfkompressionskreislauf 200 Kältemitteldampf durch den Verdichter 210 auf einen Hochdruck HD gebracht wird und zu einem Verflüssiger 220 geführt ist, wobei ein Hochdruckpfad mit der Hochdruckströmungsrichtung S_HD vom Verdichter 210 bis zum Expansionsventil 230 gebildet ist. Nach dem Expansionsventil 230 bis zum Verdichter 210 ist ein Niederdruckpfad mit einer Niederdruckströmungsrichtung SND des Kältemittels gebildet, in dem der Verdampfer 240 liegt.

1 shows schematically and as an example a heat pump 100 . The heat pump 100 consists essentially of a vapor compression system forming a compression refrigeration system 200 , which contains the following components:

• • A compressor 210 to compress the superheated refrigerant,
• • a condenser 220 , with a refrigerant-side condenser inlet 221 and a condenser outlet 222 for the transfer of thermal energy Q _H from the vapor compression system 200 to a heating medium of a heating system 400 , with a heating medium inlet 401 , a heating medium outlet 402 and a heating medium pump 410 , to a building heating system or a system for hot water heating,
• • advantageously a refrigerant collector 260 , which is used as a refrigerant reservoir to compensate for different refrigerant quantities depending on the operating conditions,
• • a throttle device designed as an expansion valve 230 to expand the refrigerant,
• • an evaporator 240 , with an evaporator inlet 241 , for the transmission of source energy Q _Q from a heat source system 300 , with a heat source inlet 320 and a heat source outlet 310 , being the heat source system 300 in particular can be a brine system, which heat energy Q _Q from the ground or an air system that absorbs heat energy Q _Q from the ambient air and to the vapor compression system 200 emits or any other heat source,
• • a recuperator as an example of an internal heat exchanger 250 which is intended to be internal heat energy Q _i between that of the condenser 220 to the expansion valve 230 flowing refrigerant to that from the evaporator 240 to the compressor 210 transferring flowing refrigerant and
• • a refrigerant, in particular a refrigerant mixture of at least two substances or two refrigerants which in a flow direction S _HD and SND through the vapor compression circuit 200 flows, being in the vapor compression cycle 200 Refrigerant vapor through the compressor 210 is brought to a high pressure HD and to a condenser 220 is guided, wherein a high pressure path with the high pressure flow direction S _HD from the compressor 210 to the expansion valve 230 is formed. After the expansion valve 230 to the compressor 210 a low-pressure path is formed with a low-pressure flow direction SND of the refrigerant in which the evaporator 240 located.

The actuators listed below are advantageously at least partially connected to the controller via a data connection 510 that can be done by cable, radio or other technologies: compressor 210 , Heating medium pump 410 , Brine pump 330 , Expansion valve 230 , Compressor inlet temperature sensor 501 , Low pressure sensor 502 , High pressure sensor 503 Hot gas temperature sensor 504 , Recuperator inlet temperature sensor, 505 Recuperator outlet temperature sensor 506 and / or evaporator outlet temperature sensor 508 . Additionally or alternatively, an in the 1 evaporator inlet temperature sensor, not shown, the temperature at the evaporator inlet 241 determine.

In the in 1 The example shown is the heat pump 100 shown as a brine heat pump. Of course, analogous considerations and advantages can be achieved with air / water heat pumps. Especially with air heat pumps, a brine pump is used instead of the brine circuit 330 a fan / fan arranged as a heat source.

The compressor 210 serves to compress the superheated refrigerant from an inlet connection 211 to a compressor discharge pressure P _Va at a compressor outlet temperature corresponding to the hot gas temperature at the compressor outlet 212 . The compressor 210 usually contains a drive unit with an electric motor, a compression unit and advantageously the electric motor can be operated at variable speed. The compression unit can be designed as a rolling piston unit, scrolling unit or otherwise. At the compressor outlet 212 is the compressed, superheated refrigerant at the compressor discharge pressure P _Va at a higher pressure level, in particular a high pressure HD, than at the inlet connection 211 with a compressor inlet pressure P _Ve , in particular a low pressure LP, at a compressed inlet temperature T _VE what the state of the refrigerant temperature at the inlet connection 211 describes when entering a compression chamber.

In the condenser 220 the transfer of thermal energy takes place Q _H from the refrigerant of the vapor compression system 200 to a heating medium of the heat sink system 400 . First takes place in the liquefied 220 the desuperheating of the refrigerant takes place, whereby superheated refrigerant vapor, by reducing the temperature, transfers part of its thermal energy to the heating medium of the heat sink system 400 transmits.

After the refrigerant vapor has been de-heated, it is advantageous to do so in the condenser 220 another heat transfer Q _H by condensation of the refrigerant during the phase transition from the gas phase of the refrigerant to the liquid phase of the refrigerant. This will add more heat Q _H from the refrigerant from the vapor compression system 200 to the heating medium of the heat sink system 400 transfer.

Which is in the liquefier 220 The setting high pressure HD of the refrigerant corresponds to the operation of the compressor 210 approximately with a condensation pressure of the refrigerant at a heating medium temperature Tws in the heat sink system.

The heating medium, in particular water, is by means of a heating medium pump 410 through the heat sink system 400 in a SW direction through the condenser 220 promoted, thereby the thermal energy Q _H transferred from the refrigerant to the heating medium.

In the following collector 260 becomes from the condenser 220 escaping refrigerant stored, which depends on the operating point of the vapor compression circuit 200 should not be fed into the circulating refrigerant. Becomes from the condenser 220 more refrigerant fed in than through the expansion valve 230 is forwarded, the collector fills up 260 , otherwise it becomes emptied or emptied.

In the following recuperator 250 , which can also be referred to as an internal heat exchanger, becomes internal heat energy Q _i from the refrigerant under high pressure HD, which is from the condenser 220 to the expansion valve 230 flows in a high-pressure flow direction S _HD , transferred to the refrigerant flowing under the low pressure ND, which flows from the evaporator to the compressor in a low-pressure _{flow direction S ND} . This changes from the condenser to the expansion valve 230 flowing refrigerant is advantageously supercooled.

First, the refrigerant flows through an expansion valve inlet 231 into the expansion valve. In the expansion valve 230 the refrigerant pressure is throttled from high pressure HP to low pressure LP by the refrigerant advantageously passing through a nozzle arrangement or throttle with an advantageously variable opening cross section, the low pressure advantageously being approximately the suction pressure of the compressor 210 is equivalent to. Instead of an expansion valve 230 any other pressure reducing device can also be used. Pressure reducing pipes, turbines or other expansion devices are advantageous.

An opening degree of the expansion valve 230 is set by an electric motor, which is usually designed as a stepper motor, which is controlled by the control unit or regulation 500 is controlled. The low pressure is LP at the expansion valve outlet 232 of the refrigerant from the expansion valve 230 controlled in such a way that the low pressure ND of the refrigerant that is established when the compressor is in operation 210 corresponds _{roughly to the evaporation pressure of} the refrigerant with the heat source medium temperature T WQ. The evaporation temperature of the refrigerant will advantageously be a few Kelvin below the heat source _medium temperature T WQ so that the temperature difference drives heat transfer.

In the evaporator there is a transfer of evaporation heat energy Qv from the heat source fluid of the heat source system 300 , which is a brine system, a geothermal system for the use of Thermal energy Q _Q from the ground, an air system for the use of energy Q _Q from the ambient air or another heat source that is the source energy Q _Q to the vapor compression system 200 gives away.

That in the vaporizer 240 Incoming refrigerant is reduced when flowing through the evaporator 240 through heat absorption Q _Q its wet steam content and leaves the evaporator 240 advantageously with a low proportion of wet steam or advantageously also as a superheated gaseous refrigerant. The heat source medium is supplied by means of a brine pump 330 in the case of brine - water heat pumps or an outside air fan in the case of air / water heat pumps through the heat source media path of the evaporator 240 promoted, with the heat source medium the heat energy as it flows through the evaporator Q _Q is withdrawn.

In the recuperator 250 becomes thermal energy Q _i between that of the condenser 220 to the expansion valve 230 flowing refrigerant to that from the evaporator 240 to the compressor 210 Transferring flowing refrigerant, taking that from the evaporator 240 to the compressor 210 flowing refrigerant in particular continues to overheat.

This superheated refrigerant, which with an overheating temperature T _Ke from the recuperator 250 becomes the refrigerant inlet connection 211 of the compressor 210 directed.

The recuperator 250 is in the vapor compression circuit 200 used to calculate the overall efficiency as the quotient of the heat output Q _H and to increase the electrical power P _{e consumed} to drive the compressor motor.

For this purpose, the refrigerant in the condenser 220 Thermal energy Q _H at a heat sink side temperature level to the heating medium, in the high pressure path of the recuperator 250 further thermal energy through subcooling Q _i withdrawn.

The internal energy state of the refrigerant when it enters the evaporator 240 is through this deprivation of heat Q _i reduced so that the refrigerant has more heat energy at the same evaporation temperature level Q _Q from the heat source 300 can accommodate.

Then the refrigerant, after the evaporator outlet 242 from the vaporizer 240 , in the low pressure path at low pressure LP and at a low pressure temperature corresponding to an evaporator outlet temperature T _Va in the recuperator 250 the thermal energy extracted in the high pressure path Q _i fed back. The supply of energy has the advantageous effect of reducing the proportion of wet steam to a state without a proportion of wet steam and then overheating occurs through further supply of energy.

Furthermore, to record the operating status of the vapor compression system 200 advantageously arranged the following sensors, with which in particular to safeguard and optimize the operating conditions of the vapor compression system 200 A model-based pre-control is implemented, especially in the event of changes in the operating status.

• • Ein Hochdrucksensor 503 vorteilhaft zur Erfassung des Hochdrucks HD des Kältemittels am Verdichteraustritt 212 oder zwischen dem Verdichteraustritt 212 und dem Expansionsventileintritt 231,
• • ein Heißgastemperatursensor 504 vorteilhaft zur Erfassung einer Heißgastemperatur T_HG des Kältemittels am Verdichteraustritt 212, oder im Kältekreisabschnitt zwischen dem Verdichteraustritt 212 und dem Verflüssigereintritt 221,
• • ein Innentemperatursensor 506 vorteilhaft zur Erfassung der Innentemperatur T_le des Kältemittels zwischen dem hochdruckseitigem internen Rekuperatorauslass 252 des Kältemittels aus dem Rekuperator 250 und dem Expansionsventileitritt 231. Die Innentemperatur ist vorteilhaft auch als „Rekuperatoraustrittstemperatur Hochdruckpfad“ benannt und
• • vorteilhaft ein Rekuperatorinnentemperatursensor 505. Der Rekuperatorinnentemperatursensor 505 erfasst vorteilhaft Verflüssigeraustrittstemperatur T_FA des Kältemittel in der Strömungsrichtung am Verflüssigeraustritt oder dem hochdruckseitigen Rekuperatoreintritt und daher wird vorteilhaft die Verflüssigeraustrittstemperatur T_FA vom Rekuperatorinnentemperatursensor 505 gemessen.

On the one hand, with the aid of the process values recorded by sensors, safeguards are advantageously made with regard to permissible working areas of the components, such as the compressor in particular 210 On the other hand, based on the sensor data, model-based precontrols, in particular a speed of the compressor, take place 210 and / or a valve opening degree of the expansion valve, so that the controller only needs to make minor corrections to compensate for a control deviation that is nevertheless smaller due to the precontrol:

• • A high pressure sensor 503 advantageous for recording the high pressure HD of the refrigerant at the compressor outlet 212 or between the compressor outlet 212 and the expansion valve inlet 231 ,
• • a hot gas temperature sensor 504 advantageous for detecting a hot gas temperature T _{HG of} the refrigerant at the compressor outlet 212 , or in the refrigeration circuit section between the compressor outlet 212 and the condenser inlet 221 ,
• • an indoor temperature sensor 506 advantageous for recording the internal temperature T _{le of} the refrigerant between the internal recuperator outlet on the high-pressure side 252 of the refrigerant from the recuperator 250 and the expansion valve entry 231 . The internal temperature is advantageously also known as the "recuperator outlet temperature high-pressure path" and
• • Advantageously, a recuperator internal temperature sensor 505 . The internal recuperator temperature sensor 505 advantageously detects the condenser outlet temperature T _FA of the refrigerant in the flow direction at the condenser outlet or the high-pressure side recuperator inlet and therefore the condenser outlet temperature is advantageous T _FA from the internal recuperator temperature sensor 505 measured.

• • Ein Niederdrucksensor 502 zur Erfassung des Niederdrucks ND des Kältemittels am Verdichtereintritt 211, oder zwischen dem Expansionsventil 230 und dem Verdichtereintritt 211,
• • ein Verdampferaustrittstemperatursensor 508 zur Erfassung der Verdampferaustrittstemperatur T_Va des Kältemittels am Verdampferaustritt 242 oder zwischen dem Verdampferaustritt 242 und dem niederdruckseitigen Eintritt des Kältemittels in den Rekuperatoreinlass 251 des Rekuperators 250 und
• • ein Niederdrucktemperatursensor 501 misst vorteilhaft eine Verdichtereintrittstemperatur oder dient vorteilhaft zur Erfassung der Kältemittelniederdrucktemperatur T_ND oder vorteilhaft einer Verdichtereintrittstemperatur T_KE am Verdichtereintritt 211, oder zwischen dem niederdruckseitigem Rekuperatorauslass 252 des Kältemittels aus dem Rekuperator 250 und dem Verdichtereintritt 211.

The following sensors are particularly advantageous for carrying out the method according to the invention:

• • A low pressure sensor 502 for recording the low pressure LP of the refrigerant at the compressor inlet 211 , or between the expansion valve 230 and the compressor inlet 211 ,
• • an evaporator outlet temperature sensor 508 for recording the evaporator outlet temperature T _{Va of} the refrigerant at the evaporator outlet 242 or between the evaporator outlet 242 and the low-pressure side entry of the refrigerant into the recuperator inlet 251 of the recuperator 250 and
• • a low pressure temperature sensor 501 _{advantageously measures a compressor inlet temperature} or advantageously serves to detect the low-pressure refrigerant temperature T ND or advantageously a compressor inlet _temperature T KE at the compressor inlet 211 , or between the recuperator outlet on the low pressure side 252 of the refrigerant from the recuperator 250 and the compressor inlet 211 .

The process variable, which has a significant influence on the overall efficiency of the vapor compression cycle 200 as the quotient between that of the vapor compression circuit 200 transferred heating power Q _H to one from the compressor 210 The electrical power P _e consumed is the overheating of the refrigerant at the compressor inlet 211 . In order to comply with permissible compressor operating conditions, however, it is advantageous to comply with restrictions with regard to the permissible overheating range of the refrigerant at the compressor inlet. Overheating that is too low endangers the lubricating properties of the machine oil in particular, while overheating that is too high particularly results in a hot gas temperature that is too high.

The overheating describes the temperature difference between the recorded compressor _{inlet temperature T KE of} the refrigerant and the evaporation temperature of the refrigerant in the case of saturated steam.

According to the invention, the superheating of the compressor inlet is preferably regulated in such a way that no condensate due to the water vapor content in the ambient air falling below the dew point in components of the refrigeration circuit, particularly in the section between the refrigerant outlet of the recuperator 252 and compressor inlet 211 fails. The refrigeration circuit section between the evaporator outlet 242 and recuperator inlet 251 is usually colder because this is typically only a short pipe section, there is better insulation compared to the section between the refrigerant outlet of the recuperator 252 and compressor inlet 211 possible. For example, sits at the point of the compressor inlet 211 the refrigerant separator on the compressor that is to be protected. This is difficult to enclose, so that here the temperature should be kept so high that nothing condenses. The problem of condensation does not usually occur on the high pressure side. Also the passage between the recuperator outlet on the high pressure side 252 and entry into the expansion valve 231 cools regularly depending on the operating point with ideal heat transfer conditions in the recuperator 250 on the temperature level of the refrigerant at the evaporator outlet 242 away. However, since this passage is typically short and can be isolated very well, this section is usually not problematic either. It should be noted, however, that the method according to the invention can in principle prevent a condensate drop over the entire circuit of the heat pump.

If - for the purpose of a numerical example - an evaporation temperature level of approx. -10 ° C is assumed and the temperature at the brine inlet 330 at about -10 ° C, at the brine outlet 310 is around -13 ° C and 5 ° C at the compressor inlet, this means overheating 15K .

In many systems, room temperature sensors and room humidity sensors, which enable precise determination of the condensation conditions of the air, are advantageous, for example at 21 ° C and 60% rel. Moisture the condensation temperature in the range of 13 ° C. Under these conditions, no condensation takes place as long as the pipe temperature is above 13 ° C plus, if necessary, a buffer, e.g. 1K.

The numerical example, which is of course non-restrictive, is now used to achieve overheating of 15K at a compressor inlet temperature of 5 ° C. This temperature is below 13 ° C, which is determined for the current ambient conditions as the condensation temperature of the water vapor in the ambient air. Accordingly, condensation takes place. If the compressor inlet temperature is to be at least 14 ° C, i.e. the condensation temperature plus buffer, the overheating must be 9K greater, i.e. an overheating of 24K must be maintained.

Limit values, especially for overheating, determine the permissible overheating range of the components at the compressor inlet depending on the operating point 211 fixed. Furthermore, there are also dependencies between the compressor _{inlet superheating} dT ÜE and the overall efficiency of the vapor compression circuit 200 or between the compressor _{inlet overheating} dT ÜE and a stability S of a control value R, which is advantageous when regulating the compressor inlet overheating.

In order to take into account all these requirements, it is advantageous to depend on the operating point of the vapor compression circuit 200 , the heat source medium temperature, the heating medium temperature, the compressor _{output P e} and target values Z or the target value Z are used to calculate the compressor _{inlet superheat} dT ÜE. Alternatively or additionally, a calculation of the target value Z as a default value for the compressor _{inlet superheat} dT ÜE can be carried out from the refrigerant circuit parameters dependent on the operating point, such as heat source medium temperature, heating medium temperature, compressor power P _{e and parameterizable coefficients that are adapted to the behavior of the respective refrigerant circuit components.} In the simplest case, the target value for the compressor _{inlet superheat dT ÜE is constant} regardless of all operating conditions, eg 10 Kelvin. In the case of a more complex adaptation it is varied as a function of an operating point variable, for example the compressor power P _e , or in the case of an even more complex adaptation it varies as a function of several operating point variables.

• • Regelabweichung der Verdichtereintrittsüberhitzung dT_ÜE = Messwert Verdichtereintrittsüberhitzung - Zielwert Verdichtereintrittsüberhitzung Z_TÜE
• • Regelabweichung der Verdampferaustrittsüberhitzung dT_ÜA = Messwert Verdampferaustrittsüberhitzung - Zielwert Verdampferaustrittsüberhitzung Z_TÜA

A control deviation of the compressor _{inlet superheat} dT ÜE and a control deviation of the evaporator _{outlet superheat dT ÜA} are combined with each other, weighted, resulting in the controller 500 a total control deviation is calculated, which is used to control the vapor compression circuit 200 is fed in. The control deviations from the compressor _{inlet superheat} dT ÜE and evaporator _{outlet superheat dT ÜA} are advantageously formed more precisely by forming the differences between the respective measured values and target values.

• • Control deviation of the compressor _{inlet superheat} dT ÜE = measured value compressor _{inlet superheat - target value compressor inlet superheat Z TÜE}
• • Control deviation of the evaporator _{outlet superheat dT ÜA} = measured value evaporator outlet superheat - target value evaporator outlet superheat Z TÜA

The weighted influence of the control deviation of the compressor _{inlet superheating} dT ÜE and the weighted influence of the control deviation of the evaporator _{outlet superheating dT ÜA} in the controller are then advantageous 500 the total control deviation is calculated, which is used to regulate the vapor compression circuit 200 is fed in.

With the vapor compression circuit 200 the refrigerant passes through the expansion valve after the expansion 230 two sequentially arranged heat exchangers, the evaporator 240 and the recuperator 250 in which the refrigerant heat energy Q _Q and Q _i is fed.

In the evaporator 250 is the source of heat energy for the refrigerant Q _Q from the heat source system 300 fed. The temperature level of the supplied source heat Q _Q is at the same temperature level as the heat source, in particular that of the ground or the outside air.

In the recuperator following in the refrigerant high pressure flow direction S _HD 250 heat energy is added to the refrigerant Q _i after leaving the condenser 220 withdrawn. The temperature level of the refrigerant at the outlet of the condenser is approximately at the level of the return temperature of the heating medium.

This interconnection of the evaporator 240 with the recuperator 250 in series has a decisive influence on the transfer function of the controlled system for controlling the compressor _{inlet superheat} dT ÜE.

The control value R is advantageously the weighted link between the control deviation of the compressor _{inlet superheat} dT ÜE and the control deviation of the evaporator outlet superheat.

_{Actuator operating state variables} with an influence on the control value R, in particular the compressor inlet overheating dT ÜE, are in the relevant vapor compression circuit 200 the compressor speed and / or the degree of opening of the expansion valve 230 , which also advantageously determines the low pressure LP and the evaporation temperature level.

Actuators have a particularly advantageous influence on the control value R, in particular on the weighted linkage of the control deviation of the compressor inlet overheating with the control deviation of the evaporator outlet overheating. In the relevant vapor compression circuit 200 are especially the compressor 210 by varying the compressor speed and the expansion valve 230 by influencing the degree of opening such actuators. These two actuators influence the low pressure LP and the evaporation temperature level.

Not all influences are desired here. For example, a change in the compressor speed to regulate the desired heating output without further compensatory changes in the degree of opening of the expansion valve advantageously changes the control value R into undesired ranges, so that a model-based, supported change in the degree of opening of the expansion valve to regulate R, which accompanies the change in the compressor speed, is advantageous and may even be necessary.

It is advantageous in the steam compression cycle 200 the compressor speed is set so that the from the vapor compression circuit 200 heat output transferred to the heating medium QH corresponds to the requested target value Z. To comply with this requirement, influencing the compressor _{speed to control the compressor inlet superheating} dT ÜE is advantageously subordinate or not appropriate.

• Das Expansionsventil 230 agiert als Düse mit elektromotorisch verstellbarem Düsenquerschnitt, bei welchem üblicherweise mittels eines Schrittmotor eine nadelförmige Düsennadel per Gewinde in einen Düsensitz gefahren wird.

The degree of opening of the expansion valve is advantageous 230 used as the control value for the regulation of the compressor _{inlet superheat} dT ÜE. The influence of the degree of opening of the expansion valve 230 on the compressor _{inlet overheating} dT ÜE takes place as follows:

• The expansion valve 230 acts as a nozzle with an electrically adjustable nozzle cross-section, in which a needle-shaped nozzle needle is usually threaded into a nozzle seat by means of a stepper motor.

The refrigerant throughput through the expansion valve is when operating with liquid refrigerant at the expansion valve inlet 231 roughly proportional to the square root of the pressure difference between the expansion valve inlet 231 and outlet 232 multiplied by a current relative value of the nozzle cross-section or degree of opening and advantageously one of the refrigerant and a geometry of the expansion valve 230 dependent constant.

Since at an operating point with a compressor speed assumed to be constant and a heating medium temperature Tws assumed to be constant, the corresponding high pressure HD of the refrigerant when entering the expansion valve 230 can be assumed to be constant, affects the degree of opening of the expansion valve 230 relevant only the low pressure LP, i.e. the outlet pressure from the expansion valve 230 .

Becomes the opening degree of the expansion valve 230 reduced, less refrigerant passes through the expansion valve at constant high pressure HP and initially still constant low pressure LP 230 . Because the compressor 210 but continues to initially convey the same refrigerant mass flow, S _HD is in high pressure flow direction through the expansion valve 230 less refrigerant supplied than from the compressor 210 is sucked off.

Since refrigerant vapor is a compressible medium, the low pressure LP then drops on the low pressure side of the vapor compression circuit 200 . When the low pressure LP drops, the mass flow of refrigerant through the compressor drops roughly proportionally 210 , since its delivery rate can be roughly described as volume / time, due in particular to the piston strokes, and a correspondingly reduced low pressure value ND is set at which the pressure generated by the expansion valve 230 supplied refrigerant mass flow equal to that from the compressor 210 discharged refrigerant mass flow is.

Becomes the opening degree of the expansion valve 230 increased, more refrigerant passes through the expansion valve at constant high pressure HP and initially still constant low pressure LP 230 . Because the compressor 210 but continues to deliver the same refrigerant mass flow initially, the low-pressure side LP of the refrigeration circuit is passed through the expansion valve 230 more refrigerant supplied than from the compressor 210 is sucked off. Since refrigerant vapor is a compressible medium, the low pressure LP increases on the low pressure side of the vapor compression circuit 200 . With increasing low pressure LP, the mass flow rate of the compressor increases 210 roughly proportional, since its delivery rate can be roughly described as volume / time, and a correspondingly increased low pressure LP is set at which the pressure caused by the expansion valve 230 supplied refrigerant mass flow equal to that from the compressor 210 discharged refrigerant mass flow is.

The low pressure LP in turn significantly influences the heat transfer between the heat source medium and the refrigerant in the evaporator 240 . The heat flow Q _Q from the heat source system 300 is transferred between the heat source medium and the refrigerant at different temperatures, with the heat flow Q _Q depending on the temperature difference between the heat source medium and the refrigerant and the heat transfer resistance of a heat transfer layer of the evaporator 240 is.

The heat transfer resistance between the heat source media path of the evaporator and the refrigerant path of the evaporator is in a respective vapor compression circuit 200 to be assumed to be roughly constant. Hence the size of the heat transfer capacity in the evaporator 240 largely dependent on the integral of the temperature differences of all surface elements of the heat transfer layer.

To get a sufficient amount of thermal energy Q _Q from the heat source system 300 To be able to transfer to the refrigerant, it must be ensured that the temperature of the heat source medium in as many surface elements as possible of the transfer layer of the heat exchanger, here the evaporator 240 , is greater than the temperature of the refrigerant on the respective surface element.

Is the physical state of the refrigerant as it flows through the evaporator 240 saturated vapor, a refrigerant temperature is established which, as a material property of the refrigerant, is a function of the low pressure ND of the refrigerant as a result of the saturation vapor characteristic. So lets By controlling the low pressure LP or an evaporation pressure, the evaporation temperature of the refrigerant as it flows through the recuperator is indirectly controlled 250 steer.

The thermal energy Q _Q , which from the heat source system to the evaporator 240 The refrigerant flowing through is transferred, affects the physical state of the refrigerant.

• • Nassdampfanteil bei Eintritt in den Verdampfer 240,
• • Kältemittelmassenstrom,
• • Übertragener Wärmeleistung Q_Q , und von einer
• • Enthalpiedifferenz im Nassdampfgebiet beim jeweiligen Niederdruck ND, welche das Kältemittel als eine zugeordnete Funktion Drucks aufweist.

The proportion of wet steam in saturated refrigerant vapor decreases at constant low pressure when heat is transferred to the refrigerant. In the event of incomplete evaporation, the proportion of wet steam and thus also the internal energy state of the refrigerant when it exits the heat exchanger is a function of:

• • Wet steam content when entering the evaporator 240 ,
• • refrigerant mass flow,
• • Transferred heat output Q _Q , and from one
• • Enthalpy difference in the wet steam area at the respective low pressure LP, which the refrigerant has as an assigned function of pressure.

Additional energy is supplied to the recuperator for complete evaporation 250 to superheat the refrigerant beyond the saturated vapor state.

With the method, the vapor compression cycle is created under given operating conditions 200 Depending on the manipulated variable "degree of opening expansion valve 230", a corresponding refrigerant condition when exiting the evaporator 240 set.

In the steady state, a controlled system behavior with moderate steepness results with regard to a control path steepness of the "isolated" controlled system "Evaporator 240". The control system behavior is characterized in particular by the control system output value of the evaporator outlet overheating as a function of the control system input value of the expansion valve opening degree.

A refrigerant is advantageously used, in particular a refrigerant mixture as the refrigerant, which has a “temperature glide”, in particular R454C is advantageously used. In the case of a refrigerant mixture with a temperature glide, it is advantageous if the relative degree of opening of the actuator expansion valve changes by 1% rel. a change in superheating of approximately less than 1 K is usually set at the outlet of the refrigerant from the evaporator.

• • Eine erste Zeitkonstante bewirkt vorteilhaft eine Verzögerung der mechanischen Öffnungsgradänderung des Expansionsventils 230 durch die Begrenzung der Verfahrgeschwindigkeit durch den Regler 500, der Regelwert R wird in dieser ersten Zeitkonstante Z in der Verfahrgeschwindigkeit durch einen Bremswert reduziert. Der Bremswert kann beispielsweise die reglertechnische Zykluszeit, in welcher ein Verfahrensschritt des Expansionsventils 230 gesteuert wird, umfassen.
• • Eine zweite Zeitkonstante wirkt durch den Regler 500 vorgegeben vorteilhaft auf eine verzögerte Einstellung eines korrespondierenden Niederdruckes bei Öffnungsgradänderungen des Expansionsventils 230 aufgrund der Kompressibilität des Kältemitteldampfes bei Niederdruck ND im Niederdruckpfad.
• • Eine dritte Zeitkonstante ist vorteilhaft eine thermische Zeitkonstante der Wärmeübertragungsschicht des Verdampfers 240, wobei eine Änderung des Verdampfungsdruckes und damit der Verdampfungstemperatur eine verzögerte Temperaturänderung der Wärmeübertragungsschicht des Verdampfers, welcher oft mehrere Kilogramm Metall hat und des Wärmequellenmediums.
• • Eine vierte Zeitkonstante ergibt sich vorteilhaft aus verzögerten Aggregatzustandsänderungen des Kältemittels bei Verdampfungstemperaturänderungen.
• • Eine fünfte Zeitkonstante ergibt sich vorteilhaft aus dem Transport des Kältemittels durch den Verdampfer 240 mit einer endlichen Strömungsgeschwindigkeit.

This state is advantageously also set by influencing at least one or more of the various subsequent time constants in terms of control technology; which is ultimately the process variable refrigerant overheating at the evaporator outlet 242 influence:

• A first time constant advantageously causes a delay in the mechanical change in the degree of opening of the expansion valve 230 by limiting the travel speed by the controller 500 , the control value R is reduced in the travel speed in this first time constant Z by a braking value. The braking value can, for example, be the controller cycle time in which a method step of the expansion valve 230 is controlled, include.
• • A second time constant acts through the controller 500 predetermined advantageously to a delayed setting of a corresponding low pressure in the case of changes in the degree of opening of the expansion valve 230 due to the compressibility of the refrigerant vapor at low pressure LP in the low pressure path.
• A third time constant is advantageously a thermal time constant of the heat transfer layer of the evaporator 240 , whereby a change in the evaporation pressure and thus the evaporation temperature is a delayed change in temperature of the heat transfer layer of the evaporator, which often has several kilograms of metal, and of the heat source medium.
• • A fourth time constant results advantageously from delayed changes in the physical state of the refrigerant in the event of changes in the evaporation temperature.
• • A fifth time constant results advantageously from the transport of the refrigerant through the evaporator 240 with a finite flow velocity.

Thus, after changing the manipulated variable “degree of opening of expansion valve 230”, there is advantageously a delay in the corresponding change in refrigerant state when it exits the evaporator outlet 242 one and one total time constant Ztot, depending on the operating point, is advantageously in the range from 30 seconds to about 5 minutes.

After flowing through the evaporator 240 the refrigerant enters the low pressure path of the recuperator at low pressure LP 250 one.

The physical state of the refrigerant as it flows into the recuperator 250 is in a normal operating case, that is, advantageously either saturated steam with a low steam content between 0 to 20% or, in particular, advantageously also already superheated refrigerant.

In the case of advantageously saturated steam, a refrigerant temperature is established which, due to the saturation vapor characteristic curve of the refrigerant, is a function of the refrigerant pressure. When superheated refrigerant enters, the refrigerant temperature will at most assume a size which corresponds to the entry temperature of the heat source medium. In this case, the size preferably corresponds to the inlet temperature of the refrigerant in the high-pressure path of the recuperator 250 , i.e. the temperature of the refrigerant after it leaves the condenser 220 .

To get a sufficient amount of thermal energy from the refrigerant of the high-pressure side refrigerant path to the refrigerant of the low-pressure side refrigerant path in the recuperator 250 To be able to transmit, it must be ensured that the temperature of the refrigerant of the high-pressure side refrigerant path is at high pressure HD in as many surface elements as possible of the transfer layer of the recuperator 250 is greater than the temperature of the refrigerant of the low-pressure side refrigerant path at low pressure LP on the respective surface element.

The corresponding temperatures of the heating system 400 of the vapor compression system 200 are higher than the corresponding temperatures of the heat source such as the ground or the outside air when heating.

The thermal energy Q _i , which is from the refrigerant at high pressure HD of the high pressure side refrigerant path to the refrigerant at low pressure in the low pressure side refrigerant path of the recuperator 250 is transmitted, affects the physical state of the refrigerant on the low-pressure side. The wet steam content of the recuperator 250 On the low-pressure side, the refrigerant flowing through at low pressure LP decreases when heat is transferred to the refrigerant and, after complete evaporation, the refrigerant is advantageously overheated.

• • Nassdampfanteil bei Eintritt in den Rekuperator 250,
• • Kältemittelmassenstrom,
• • übertragene Wärmeleistung Q_i , womit vorteilhaft abhängig von der Temperaturdifferenz zwischen der Temperatur des Kältemittels bei Hochdruck HD im hochdruckseitigen Kältemittelpfad und der Temperatur des Kältemittels des niederdruckseitigen Kältemittelpfades bei Niederdruck ND geregelt wird, und/oder
• • eine Enthalpiedifferenz im Nassdampfgebiet beim jeweiligen Niederdruck ND.

The internal energy state of the refrigerant when it emerges from the low-pressure side path of the recuperator is advantageously influenced as a function of one or more of the following factors. It should be noted that the change in energy state is based exclusively on physical dependencies, with the controller influencing the control of the actuators, which of course also influences the physical variables such as the refrigerant mass flow:

• • Wet steam content when entering the recuperator 250 ,
• • refrigerant mass flow,
• • transferred heat output Q _i , which is advantageously regulated depending on the temperature difference between the temperature of the refrigerant at high pressure HD in the high-pressure side refrigerant path and the temperature of the refrigerant of the low-pressure side refrigerant path at low pressure LP, and / or
• • an enthalpy difference in the wet steam area at the respective low pressure LP.

This advantageously has the effect that, depending on the given operating conditions, the vapor compression circuit 200 as well as depending on the manipulated variable "degree of opening expansion valve 230 “A corresponding refrigerant condition at the outlet 252 from the recuperator 250 sets at low pressure LP.

In the steady state, the steepness of the control path results in the "isolated" control path at low pressure LP of the refrigerant in the low-pressure side path of the recuperator 250 a control system behavior with a high slope, with an approximately constant internal energy state of the refrigerant at the inlet 251 in the low pressure side LP path of the recuperator 250 . With a particularly relative change in the degree of opening of the expansion valve of 1%, there is a change in superheating at the outlet of the refrigerant from the evaporator 230 set of advantageously about 10 K or above 10 K.

Compared to the recuperator 250 there is advantageously a significantly higher heat transfer in the evaporator 240 between the source medium and the refrigerant in the evaporator 240 .

This is what happens in the vaporizer 240 a much higher heat transfer than in the recuperator 250 set as the environment by means of evaporator 240 a much greater amount of energy is to be withdrawn than it is only in the recuperator 250 to be transferred within the refrigeration circuit. The driving temperature difference in the recuperator is between 20 K and 60 K, for example, while it is only between 3 K and 10 K in the evaporator. In order to be able to transfer the desired energies in spite of different driving temperature differences, the exchanger surface of the evaporator, for example, is designed to be approx. 5 to 20 times larger than that of the recuperator 250 .

• • Mit einer elften Zeitkonstante Z₁₁ wird vorteilhaft eine Verzögerung der mechanischen Öffnungsgradänderung des Expansionsventils 230 durch die Begrenzung einer Verfahrgeschwindigkeit vorgegeben.
• • Eine zwölfte Zeitkonstante Z₁₂ wirkt vorteilhaft auf die verzögerte Einstellung eines korrespondierenden Niederdruckes ND bei Öffnungsgradänderungen des Expansionsventils 230 aufgrund der Kompressibilität des Kältemitteldampfes im Niederdruckpfad ND.
• • Eine 13. Zeitkonstante Z₁₃ ist eine thermische Zeitkonstante der Wärmeübertragungsschicht des Verdampfers. Somit bewirkt eine Änderung des Verdampfungsdruckes und damit der Verdampfungstemperatur eine verzögerte Temperaturänderung der Wärmeübertrageschicht, welche oft mehrere Kilogramm Metall beinhaltet, und des Kältemittels im Niederdruckpfad des Verdampfers 240.
• • Eine 14. Zeitkonstante Z₁₄ wird vorteilhaft aus verzögerten Aggregatzustandsänderungen des Kältemittels bei Verdampfungstemperaturänderungen ermittelt oder vorgegeben.
• • Eine 15. Zeitkonstante Z₁₅ ergibt sich vorteilhaft aus dem Transport des Kältemittels durch den Verdampfer 240 mit einer endlichen Strömungsgeschwindigkeit und wird berücksichtigt.

This state is advantageously set using at least one of the following time constants Z:

• • With an eleventh time constant Z ₁₁ , a delay in the mechanical change in the degree of opening of the expansion valve is advantageous 230 specified by the limitation of a travel speed.
• • A twelfth time constant Z ₁₂ has an advantageous effect on the delayed setting of a corresponding low pressure ND when the opening degree of the expansion valve changes 230 due to the compressibility of the refrigerant vapor in the low pressure path LP.
• • One 13th . Time constant Z ₁₃ is a thermal time constant of the heat transfer layer of the evaporator. A change in the evaporation pressure and thus the evaporation temperature thus causes a delayed change in temperature of the heat transfer layer, which often contains several kilograms of metal, and of the refrigerant in the low-pressure path of the evaporator 240 .
• • One 14th . Time constant Z ₁₄ is advantageously determined or specified from delayed changes in the physical state of the refrigerant in the event of changes in the evaporation temperature.
• • One 15th . Time constant Z ₁₅ results advantageously from the transport of the refrigerant through the evaporator 240 with a finite flow velocity and is taken into account.

The low-pressure side refrigerant path of the recuperator 250 is from the evaporator outlet 242 of the evaporator 240 fed. The internal energy state of the refrigerant is already _{delayed by at least two time constants Z, Z 11} , Z ₁₂ , Z ₁₃ , Z ₁₄ , Z ₁₅ , Ztot after changing the manipulated variable "Expansion valve opening degree".

After changing the manipulated variable "degree of opening expansion valve 230", there is a further delay in the corresponding change in the refrigerant state due to the time behavior of the recuperator 250 when exiting the low-pressure side refrigerant path of the recuperator 250 one.

The time behavior of the recuperator 250 can advantageously be taken into account as the total recuperator time constant Ztot depending on the respective working point of the steam compression circuit in the range between about 1 minute and 30 minutes.

A weighted combination of compressor _{inlet superheating} dT ÜE and that of evaporator outlet superheating _{dT U ̈ A} is advantageously carried out, in that the overall control deviation is calculated in particular by means of a weighted combination of the control deviation of the compressor _{overheating and the control deviation of the evaporator outlet superheating dT ÜA, which is calculated in the controller} 500 to regulate the steam compression circuit 200 is fed in.

The compressor _{inlet overheating} dT ÜE is advantageously used as the main control variable and the corresponding signal flows and signal processing takes place in particular in the following process steps:

Step 1

First, the process variables compressor _{inlet superheating} dT ÜE at the evaporator outlet 242 advantageously as the main control _{variable and the evaporator outlet overheating} dT ÜA advantageously recorded as an auxiliary variable in a first process step.

• • direkt messtechnisch ermittelt, mit einem Temperatursensor, welcher so positioniert ist, dass er eine der Kältemitteltemperatur im Nassdampfgebiet entsprechende Temperatur erfasst oder
• • indirekt messtechnisch ermittelt, mit einem Drucksensor, welcher einen Kältemitteldruck des im Nassdampfgebiet verdampfenden Kältemittels erfasst und aus der kältemittelspezifischen Abhängigkeit zwischen Druck und Temperatur im Nassdampfgebiet dann die Verdampfungstemperatur berechnet wird.

For this purpose, an evaporation temperature of the refrigerant at the respective detection point is either

• • determined directly by measurement, with a temperature sensor which is positioned in such a way that it detects a temperature corresponding to the refrigerant temperature in the wet steam area or
• • Determined indirectly by measurement, with a pressure sensor which detects the refrigerant pressure of the refrigerant evaporating in the wet steam area and then calculates the evaporation temperature from the refrigerant-specific dependency between pressure and temperature in the wet steam area.

Furthermore, at the respective overheating measuring point, in particular at the evaporator outlet 242 and / or at the compressor inlet 211 assigned temperatures of the refrigerant temperature by means of temperature sensors 501 , 508 recorded. The temperature difference between the refrigerant at the respective measuring point and the evaporation temperature is then calculated and this temperature difference value then corresponds to the respective overheating of the refrigerant at the measuring point.

Output variables of the calculation in step 1 are then the compressor _{inlet superheat} dT ÜE and the evaporator _{outlet superheat dT ÜA} .

step 2

• Der Sollwert für die Verdichtereintrittsüberhitzung dT_ÜE wird vorteilhaft zur Sicherstellung des zulässigen Verdichtersbetriebsbereiches und eines möglichst hohen Wirkungsgrades des Kältekreises im Bereich zwischen ca. 5 K bis 20 K variiert.

The process variables compressor _{inlet superheating} dT ÜE and evaporator _{outlet superheating dT ÜA} are advantageously offset in a second step to form assigned control deviations with the respectively assigned setpoints:

• The setpoint value for the compressor _{inlet superheat} dT ÜE is advantageously varied in the range between approx. 5 K to 20 K in order to ensure the permissible compressor operating range and the highest possible efficiency of the refrigeration circuit.

The setpoint for the evaporator outlet _superheat dT ÜA at the evaporator outlet 242 is then varied depending on the refrigeration circuit operating mode and the refrigeration circuit operating point so that the evaporator overheating in the steady normal case roughly corresponds to the process value of _{the evaporator outlet overheating dT ÜA.} This setpoint for the evaporator outlet _superheating dT ÜA can be model-based depending on an operating mode or an operating point depending on the evaporation temperature, the condensation temperature, the compressor _{output, a setpoint for the compressor inlet superheating} dT ÜE at the evaporator outlet 242 and / or are precalculated from component properties and corrected adaptively.

The control deviation of the compressor _{inlet superheat dT ÜE is then calculated by subtracting} the setpoint of the compressor _{inlet superheat} dT ÜE from the process value of the compressor inlet superheat dT ÜE.

It will then calculate the difference of the evaporator outlet overheat dT _UA by the target value of the evaporator outlet overheat dT _UA is subtracted from the process value of the evaporator outlet overheat dT _UA.

step 3

In a third method step, the control deviation of the compressor _{inlet superheating} dT ÜE and the control deviation of the evaporator _{outlet superheating dT ÜA are} advantageously combined to form an overall control deviation - superheating.

The combination takes place in particular by means of a weighted addition of the individual control deviations.

The weighting influence is a measure of the proportional combination of the individual system deviations and, in extreme cases, can result in the exclusive inclusion of only one individual system deviation, but usually the weighted inclusion of both individual system deviations.

• Gesamt - Regelabweichung Überhitzung =
• (Gewichtungseinfluss * Regelabweichung Verdichtereintrittsüberhitzung) +
• ((1 - Gewichtungseinfluss) * Regelabweichung Verdampferaustrittsüberhitzung)

The weighting influence is advantageously estimated as a value between 0 to 1, i.e. 0 to 100%, and this value is included in the degree of inclusion of the control deviation of the compressor _{inlet overheating} dT ÜE in the total control deviation, which means that the following dependency is available for the calculation of the total control deviation results in:

• Overall control deviation overheating =
• (Weighting influence * system deviation, compressor inlet overheating) +
• ((1 - weighting influence) * control deviation evaporator outlet overheating)

• • Beim Betriebsartübergang zwischen Betriebsart = Betrieb mit ausgeschaltetem Verdichter 210 und Betriebsart = Betrieb mit eingeschaltetem Verdichter 210 im Heizbetrieb wird aufgrund der dynamischen Prozesswerteänderungen beim Anfahren des Dampfkompressionssystems 200 vorteilhaft ausschließlich zunächst die Regelabweichung Verdampferaustrittsüberhitzung dT_ÜA in die Gesamt - Regelabweichung einbezogen, insbesondere ist der Wert eines Gewichtungseinflusses dann zunächst = 0 oder ein Wert vorteilhaft unter 20 %.
• • Nach einer Stabilisierungsphase des Dampfkompressionssystems 200 ist es vorteilhaft, nicht spontan auf den für den Regelbetrieb ausgelegten Wert des Gewichtungseinflusses umzuschalten, sondern den Übergang rampenförmig zu gestalten. In diesem Fall ist es vorteilhaft, dass der Wert vom Gewichtungseinfluss vom Startwert = 0, oder einem Wert insbesondere unter 20%, vorteilhaft rampenförmig auf den vorgesehenen Zielwert angehoben werden. Hiermit wird insbesondere eine Werteunstetigkeit bei einem spontanen Umschalten vermieden und somit Regelschwingungen vermieden.
• • Der Zielwert des Gewichtungseinflusses wird vorteilhaft an die jeweilige Betriebsart und den Arbeitspunkt angepasst. Betriebspunkte, welche sich durch erhöhte Schwingneigung auszeichnen bedürfen vorteilhaft einer geringeren Gewichtung der Regelabweichung der Verdichtereintrittsüberhitzung DT_ÜE, insbesondere wird hiermit ein regeltechnisch kritisches Signalverhalten der Verdichtereintrittsüberhitzung dT_ÜE aufgrund der gegenüber der Verdampferaustrittsüberhitzung dT_ÜA größeren Signalverzögerung und größeren Streckensteilheit eine Schwingneigung vermieden.

The value of the weighting influence can advantageously depend on the operating mode and / or the operating point of the heat pump 100 can be varied depending on:

• • When the operating mode is changed between operating mode = operation with the compressor switched off 210 and operating mode = operation with the compressor switched on 210 in heating mode, due to the dynamic process value changes when starting up the vapor compression system 200 Advantageously, initially only the control deviation evaporator outlet _{overheating dT ÜA is included} in the total control deviation, in particular the value of a weighting influence is then initially = 0 or a value advantageously below 20%.
• • After a stabilization phase of the vapor compression system 200 it is advantageous not to switch over spontaneously to the value of the weighting influence designed for regular operation, but to design the transition in a ramp-shaped manner. In this case it is advantageous that the value of the weighting influence from the starting value = 0, or a value in particular below 20%, is advantageously increased in a ramp-shaped manner to the intended target value. This in particular avoids a value discontinuity in the event of a spontaneous switchover and thus avoids control fluctuations.
• • The target value of the weighting influence is advantageously adapted to the respective operating mode and the operating point. Operating points, which are characterized by an increased tendency to oscillate, advantageously require a lower weighting of the control deviation of the compressor _{inlet overheating} DT ÜE, in particular a control-technically critical signal _{behavior of} the compressor inlet overheating dT ÜE due to the higher signal delay compared to the evaporator _{outlet overheating dT ÜA, a} higher signal delay and greater route steepness is avoided.

step 4th :

In a fourth process step, the calculated total control deviation of the overheating is then entered in the controller 500 processes which the corresponding actuators of the refrigeration circuit, especially the expansion valve 230 with the adjustable degree of opening and / or the compressor 210 with adjustable compressor speed, controls in such a way that in the regulated case a control deviation of the overheating is set as close as possible to about 0 Kelvin.

A P, I, PI, PID controller can be used, the control components being advantageously dynamically adapted to the respective operating mode and the operating point.

To determine the oil sump temperature, a suitable sensor is preferably provided, for example arranged on the compressor pressure capsule.

3 shows schematically and by way of example a flow diagram of a method 1000 for controlling a compression refrigeration system 200 .

In one step 1010 an oil sump temperature situation that is critical for the operation of the compressor is determined as a function of an operating point of the compression refrigeration system.

The step 1010 preferably comprises one step 1012 , in which the critical oil sump temperature situation is determined on the basis of the oil sump temperature overheating, the oil sump temperature overheating being defined as the difference between a temperature of the oil in the oil sump and a dew point temperature of the refrigerant.

The step 1010 preferably further comprises a step 1014 , in which the critical oil sump temperature situation is determined when the oil sump temperature overheat falls below a minimum value, in particular when it falls below 2 K.

In one step 1020 _{rapid heating of} the oil sump is achieved by temporarily or permanently increasing a setpoint value for overheating T ÜE of the refrigerant when it enters the compressor 210 , Step 1022 , and / or a speed of the compressor, step 1024 , carried out in the event of a critical oil sump temperature situation.

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

• DE 10159892 A1 [0005]
• DE 102005061480 B3 [0006]

Claims (10)

Method (1000) for regulating a compression refrigeration system (200) with - a refrigeration circuit, - a refrigerant, - an evaporator (240), - a compressor (210) with an oil sump, - a condenser (220), - a throttle element (230 ) and - a control unit (500) a) for detecting overheating (T _ÜE ) of the refrigerant upon entry into the compressor, the superheating (T _ÜE ) being defined as a difference between a dew point temperature and a temperature of the refrigerant, b) for regulation of the throttle element (230) based on the overheating (T _ÜE ), and c) for monitoring and controlling oil heating of the oil sump of the compressor (210), the method comprising the following steps: determining (1010) one for the operation of the compressor critical oil sump temperature situation as a function of an operating point of the compression refrigeration system (200) and - implementation (1020) of rapid oil sump heating by temporarily or permanently increasing a setpoint the overheating (T _ÜE ) of the refrigerant when entering the compressor (210) and / or a speed of the compressor in the event of a critical oil sump temperature situation. Procedure according to Claim 1 wherein the rapid oil sump heating comprises operating the compressor (210) at a minimum speed. Procedure according to Claim 2 wherein the compressor (210) is operated with at least the minimum speed until a minimum temperature of the oil of the compressor (210) is reached. Method according to one of the preceding claims, wherein a speed of the compressor (210) is set as a function of the oil temperature during the rapid heating of the oil sump. Procedure according to Claim 4 , wherein the speed of the compressor (210) increases with falling oil temperature. The method according to any one of the preceding claims, wherein an oil sump temperature superheat is defined as the difference between a temperature of the oil in the oil sump and a dew point temperature of the refrigerant, the critical oil sump temperature situation being determined on the basis of the oil sump temperature superheat. Procedure according to Claim 6 , whereby the critical oil sump temperature situation is determined when the oil sump temperature overheating falls below a minimum value, in particular when it falls below 2 K. Compression refrigeration system (200) with - a refrigerant, - an evaporator (240), - a compressor (210), - a condenser (220), - a throttle element (230) and - a control unit (500) a) for detecting overheating ( T _ÜE ) of the refrigerant on entry into the compressor, the superheating (T _ÜE ) being defined as a difference between a dew point temperature and a temperature of the refrigerant, b) for regulating the throttle element (230) based on the superheating (T _ÜE ), and c) for monitoring and controlling oil heating of the oil sump of the compressor (210), characterized in that the control unit (500) is designed to: - determine an oil sump temperature situation that is critical for the operation of the compressor as a function of an operating point of the compression refrigeration system and - carry out rapid oil sump heating by temporarily or permanently increasing a setpoint for superheating (T _ÜE ) of the refrigerant when entering the compressor (210) and / or a speed of the compressor in the event of a critical oil sump temperature situation. Compression refrigeration system according to Claim 8 , the refrigerant having a temperature glide, the refrigerant used being in particular a mixture of essentially R32 and R1234yf, particularly preferably R454C, and the compression refrigeration system in particular having an internal heat exchanger (250) for transferring thermal energy of the refrigerant before it enters the throttle element (230 ) to the refrigerant before entering the compressor (210). Heat pump (100), in particular heat pump (100) installed inside, with a compression refrigeration system (200) according to FIG Claim 8 or 9 .

Images