FR3053005A1 - METHOD FOR OPERATING A REFRIGERANT FLUID CIRCUIT - Google Patents

Abstract

The invention relates to a method for implementing a refrigerant circuit (1) in which: - a first step of determining a first temperature (T1) of the refrigerant at the outlet of a first exchanger is carried out of heat (3), - a second step of calculating a target temperature (T1cible) of the refrigerant at the outlet of the first heat exchanger (3) image of a minimum total power consumed by a compressor (2) and by a first fan (5), - a third step of comparing the first temperature (T1) and the target temperature (T 1cible) of the refrigerant at the outlet of the first heat exchanger (3), - a fourth step of actuating a first actuator (A1) of the first fan (5) according to the result of the comparison made in the third step. Application to motor vehicles.

Description

Method of implementing a refrigerant circuit

The field of the present invention is that of refrigerant circuits for a heating, ventilation and / or air conditioning system, especially for a passenger compartment of a motor vehicle. It relates to a method for the optimal implementation of a refrigerant circuit which comprises at least one fan actuator for a flow of air outside the passenger compartment which is associated with a compressor.

A motor vehicle is commonly equipped with a refrigerant circuit for modifying a temperature of an air contained inside a passenger compartment of the motor vehicle. The refrigerant circuit commonly includes a compressor for carrying the refrigerant fluid at high pressure. The refrigerant circuit also comprises a first heat exchanger associated with at least a first fan, the first heat exchanger being arranged to allow a heat exchange between the refrigerant and a first air flow, such as a flow. of air outside the motor vehicle. The refrigerant circuit also comprises a second heat exchanger associated with at least one second fan, the second heat exchanger being arranged to allow a heat exchange between the refrigerant and a second air flow, such as a flow. of air circulating inside a housing of a ventilation, heating and / or air conditioning installation, designed to modify the temperature of the air inside the passenger compartment of the motor vehicle. The refrigerant circuit also comprises an expansion device to allow expansion of the refrigerant and a control unit capable of controlling a first actuator of the first fan and a second actuator of the expansion device. The control unit controls each of the actuators of the refrigerant circuit by aiming for each an optimum. Despite this objective, it can be seen that the refrigerant circuit is not operated efficiently. Indeed, the optimum of each actuator is not necessarily the optimum of the entire refrigerant circuit.

An object of the present invention is to propose a method for implementing such a refrigerant circuit which offers an optimized coefficient of performance for a minimized consumption of constituent subassemblies of the refrigerant circuit, while reaching the temperature requested in the passenger compartment of the vehicle in an acceptable time. The invention thus counteracts a conventional reflection that aims to optimize the use of each component, seeking instead to reduce the consumption of subsets of the refrigerant circuit, including the subset constituted by the compressor and the front-end fan of the vehicle.

An object of the present invention is a method of implementing a refrigerant circuit comprising a compressor, a first heat exchanger associated with at least a first fan, the first heat exchanger being arranged to allow an exchange of calories. between the refrigerant and a first air flow, especially outside a vehicle cabin, a second heat exchanger associated with at least a second fan, the second heat exchanger being arranged to allow a heat exchange between the refrigerant fluid and a second air flow, in particular delivered in a vehicle cabin, an expansion device and a control unit able to control at least a first actuator of the first fan.

According to the present invention, the method comprises at least: a first step of determining a first temperature of the refrigerant at the outlet of the first heat exchanger, a second step of calculating a target temperature of the output refrigerant. the first heat exchanger image of a minimum total power consumed by the compressor and the first fan, - a third step of comparing the first temperature and the target temperature of the refrigerant at the outlet of the first heat exchanger, - a fourth step of actuating the first actuator of the first fan according to the result of the comparison made in the third step.

The method advantageously comprises at least one of the following characteristics: the fourth step consists in adapting the actuation of the first actuator of the first fan so that the first temperature corresponds to the target temperature of the refrigerant fluid; the target temperature of the refrigerant is determined as a function of at least a second refrigerant temperature measured or determined at the outlet of the compressor, a temperature of the air outside the vehicle and a third temperature of the second flow; of air taken downstream of the second heat exchanger, according to the direction of flow of the air flow through the second exchanger. In a complementary manner, this target temperature is also a function of the characterization of the compressor and the characterization of the first fan and / or its actuator; - There is provided a step of actuating a second actuator constituting the expansion device. This second actuator acts on the opening rate of the expansion device and thus controls the flow and the pressure of the refrigerant in the low pressure part of the circuit; the first step of determining the first temperature of the refrigerant at the outlet of the first heat exchanger is an estimate of this first temperature; alternatively, the first step of determining the first temperature of the refrigerant at the outlet of the first heat exchanger is a measurement of the first temperature. Such a measurement is carried out in particular by means of a sensor immersed in the refrigerant immediately at the outlet of the first heat exchanger; the fourth actuation step comprises a step of calculating a first implementation instruction of the first ventilator to minimize the difference between the first temperature and the target temperature; a step of calculating a target pressure of the refrigerant fluid at the outlet of the compressor which is a function of the target temperature of the coolant is provided; - A comparison step between a first refrigerant fluid pressure at the outlet of the compressor and the target pressure of the refrigerant is provided. The first pressure of the refrigerant at the outlet of the compressor can be estimated or measured by means of a sensor in contact with the refrigerant immediately at the outlet of the compressor; a step of calculating a second implementation instruction of the expansion device to minimize the difference between the first pressure and the target pressure of the refrigerant at the outlet of the compressor is provided. The invention also relates to a control unit for implementing such a method, characterized in that the control unit comprises a first controller which is able to generate the first implementation instruction of the first fan from a comparison between the first temperature and the target temperature of the refrigerant at the outlet of the first heat exchanger. The control unit advantageously comprises at least one of the following characteristics: the control unit comprises a second controller which is able to generate a second set-up for implementing the expansion device from a comparison between the first pressure and a target pressure of the refrigerant at the outlet of the compressor. the control unit comprises a third controller which is able to generate a third implementation instruction of the compressor from a comparison between the third temperature of the second air flow and a third target temperature of the second flow. of air having passed through the second heat exchanger. Finally, the invention relates to a refrigerant circuit for heat treating a passenger compartment of a motor vehicle, comprising a refrigerant circulated by a compressor constituting the circuit, the circuit comprising a first heat exchanger associated with at least a first fan , the first heat exchanger being arranged to allow a heat exchange between the refrigerant and a first air flow outside the passenger compartment, and a second heat exchanger associated with at least a second fan, the second heat exchanger being arranged to allow a heat exchange between the refrigerant and a second air flow delivered into the passenger compartment, the circuit comprising a coolant expansion device and a control unit as presented herein. The invention also relates to a refrigerant circuit as described above, wherein the expansion device comprises an ejector and an expansion member. Other characteristics, details and advantages of the invention will emerge more clearly on reading the description given below as an indication in relation to drawings in which:

Figure 1 is a schematic illustration of a first embodiment of a refrigerant circuit controlled according to the present invention.

Figure 2 is a schematic illustration of a second alternative embodiment of the refrigerant circuit controlled according to the present invention.

Figure 3 is a schematic illustration of the refrigerant circuit shown in Figure 1 and equipped with a control unit.

Figure 4 is a schematic illustration of a method according to the present invention for implementing the refrigerant circuit illustrated in the preceding figures.

In FIGS. 1 and 2, a motor vehicle is equipped with a refrigerant circuit 1 for modifying a temperature of an air contained inside a passenger compartment of the motor vehicle. The refrigerant circuit 1 is a closed circuit inside which a refrigerant circulates. The cooling fluid is for example a supercritical fluid such as carbon dioxide referenced R-744. The method which is the subject of the invention finds a particularly advantageous application when the refrigerant fluid is a supercritical fluid, but it does not exclude the use of a subcritical fluid, such as a fluorinated refrigerant fluid referenced R-134a. or non-fluorinated referenced 1234yf.

The refrigerant circuit 1 comprises a compressor 2 for bringing the refrigerant fluid to a high pressure HP. The refrigerant circuit 1 also comprises a first heat exchanger 3 which is arranged to perform a heat exchange between the refrigerant and a first air flow 4. The first heat exchanger 2 is preferably housed in a front face of the motor vehicle and it is associated with a first fan 5 for heat exchange between the refrigerant and the first air flow 4.

The first air flow 4 is advantageously a flow of air outside the passenger compartment of the motor vehicle. The refrigerant circuit 1 also comprises an internal heat exchanger 6 which comprises a first pass 6a and a second pass 6b arranged to allow a heat exchange between the refrigerant situated inside the first pass 6a and the refrigerant located inside the second pass 6b.

The refrigerant circuit 1 also comprises a second heat exchanger 7 which is preferably housed inside a housing of a heating, ventilation and / or air conditioning system 8 which equips the motor vehicle. The second heat exchanger 7 is arranged to exchange calories with a second air flow 9 which circulates inside the housing of the heating, ventilation and / or air conditioning system 8 prior to its delivery to the interior of the passenger compartment of the motor vehicle. The second air flow 9 is intended to be delivered inside the passenger compartment to change the temperature of the air contained inside the passenger compartment. The second heat exchanger 7 is for example associated with a second fan 10 for exchanging heat between the refrigerant and the second air stream 9.

The refrigerant circuit 1 also comprises an accumulator 11 provided for storing a liquid refrigerant residue in the liquid state. Finally, the refrigerant circuit 1 comprises an expansion device 12 which is likely to be of a different nature, according to various embodiments of the present invention.

According to a first variant embodiment of the refrigerant circuit 1 of the present invention illustrated in FIG. 1, the expansion device 12 is preferably an electronically controlled expansion valve inside which the refrigerant passes from the high pressure HP to a low BP pressure. Thus, according to this first embodiment, the refrigerant circulates inside the refrigerant circuit 1 at the high pressure HP from the compressor 2 to the expansion device 12, successively borrowing the first heat exchanger 3, then the first pass 6a of the internal heat exchanger 6 and the expansion device 12. The refrigerant then circulates inside the refrigerant circuit 1 at the low pressure BP from the electronic expansion valve 12 to the compressor 2 by successively borrowing the second heat exchanger 7, the accumulator 11 and the second pass 6b of the internal heat exchanger 6.

According to a second variant embodiment of the refrigerant circuit 1 of the present invention illustrated in FIG. 2, the expansion device 12 preferably comprises an ejector 13 inside which the refrigerant passes from the high pressure HP to an intermediate pressure. PI and an expansion member 14 inside which the coolant changes from the intermediate pressure PI to a low BP pressure. The expansion member 14 is indifferently a thermostatic valve, a fixed or variable section orifice or a similar expansion member.

In other words, the ejector 13 is able to relax the refrigerant fluid from the high pressure HP to the intermediate pressure P1, lower than the high pressure HP, and the expansion member 14 is able to relax the refrigerant from the intermediate pressure PI to the low pressure BP, lower than the intermediate pressure PI. Thus, according to this second embodiment, the refrigerant circulates inside the refrigerant circuit 1 at the high pressure HP from the compressor 2 to the ejector 13 by successively borrowing the first heat exchanger 3, then the first pass 6a of the internal heat exchanger 6. Then, the refrigerant circulates inside the refrigerant circuit 1 at the intermediate pressure PI from the ejector 13 to the accumulator 11, a fraction of the refrigerant fluid always circulating at the intermediate pressure P1 to the expansion element 14 or to the compressor 2. Then, the refrigerant circulates inside the refrigerant circuit 1 at the low pressure BP since the expansion member 14 to the ejector 13 by taking the second heat exchanger 7.

In FIG. 3, the refrigerant circuit shown in FIG. 1 is equipped with a control unit 15 which is able to control a first actuator Ai for rotating the first fan 5, a second actuator A2 for implementation of the expansion device 12, a third actuator A3 for the implementation of the compressor 2 and a fourth actuator A4 for the implementation of the second fan 10. The refrigerant circuit 1 illustrated in Figure 2 is capable of be equipped with a control unit similar to that fitted to the refrigerant circuit 1 illustrated in Figure 1, the ejector 13 and the expansion member 14 of Figure 2 substituting for the expansion device 12 of the figure 1.

It should be noted that the first actuator A1 is for example an electric motor which rotates an axial or radial helix, these components starting from the first fan 5.

It will also be noted that compressor 2 may be an electric compressor, that is to say a compressor whose compression mechanism is driven by an electric motor. The electric motor and the compression device may advantageously be assembled in the same housing. The control unit 15 is equipped with a first sensor Ci for measuring a first temperature Ti of the refrigerant at the outlet of the first heat exchanger 3, in the direction of circulation of the refrigerant fluid therethrough, of a second sensor C2 for measuring a second temperature T2 of the refrigerant at the outlet of the compressor 2, according to the direction of circulation of the refrigerant fluid therethrough, of a third sensor C3 for measuring a third temperature T3 of the second air stream 9 taken downstream of the second heat exchanger 7, in the direction of circulation of the second air flow 9 through it, and a fourth sensor C4 for measuring a first pressure Pi of the refrigerant at the outlet of the compressor 2, according to the direction of flow of the refrigerant fluid through it.

In general, the present invention advantageously proposes to optimize an operation of the refrigerant circuit 1 from an appropriate implementation of the compressor 2, the expansion device 12 and the first fan 5, so as to aim at a power minimal mechanical response to the heat treatment demand of the passenger compartment of the vehicle, such mechanical power resulting from a sum of the mechanical power consumed by the compressor 2 and the first fan 5.

More particularly, a method of implementing the refrigerant circuit 1 according to the present invention comprises: - a first step of determining a first temperature Ti of the refrigerant at the outlet of the first heat exchanger 3, - simultaneously or subsequently with the first step, a second step of calculating a target temperature Tîdbie refrigerant at the outlet of the first heat exchanger 3 which corresponds to a minimum mechanical power consumed by a torque formed of the compressor 2 and the first fan 5, - a third step of comparing the first temperature Ti of the refrigerant and the target temperature T iCibie refrigerant, - a fourth step of actuating an electric actuator constituting the first fan 5.

In other words, during the first step, the first temperature T i of the refrigerant is determined, ie it is measured or estimated, when it leaves the first heat exchanger 3, after being cooled. by the first air flow 4. In parallel, the control unit 15 assesses what should be the temperature of the refrigerant at the outlet of the first exchanger 3, called target temperature TiCibie, so that it is an image of the power total consumption of the compressor 2 and the first fan 5, so as to achieve an optimum HP high pressure corresponding to an optimal coefficient of performance. The control unit 15 then compares these two temperatures and controls the first electrical actuator Ai constituting the first fan 5 to stretch and reach this target temperature, and thus obtain the optimal coefficient of performance.

Advantageously, the control unit 15 can also control an opening ratio of the expansion device 12, so as to modify the first temperature Ti in order to make it tend towards the target temperature T

The method for implementing the refrigerant circuit 1 according to the present invention is illustrated in FIG. 4. Such a method is carried out by the control unit 15. The ultimate goal of this method implemented for example by the control unit is to control the third temperature T3 of the second air flow 9 measured or estimated at the outlet of the second heat exchanger 7, to change the temperature of the air contained inside the passenger compartment and reach a temperature requested by the user of the vehicle, while maximizing a coefficient of performance COP of the refrigerant circuit. This coefficient of performance COP represents the energy performance of the refrigerant circuit. The control unit 15 comprises a first controller 15a which is able to generate a first setpoint Xi for implementing the first fan 5 from a comparison between the first temperature T 1 of the refrigerant measured or evaluated at the output of the first In other words, the first controller 15a determines the first setpoint Xi, so that the total power consumed by the first actuator Ai and the third actuator A3 is minimal. Π is advantageously taken into account a total consumption by the first actuator Ai and by the third actuator A3 to finally optimize the coefficient of performance COP of the refrigerant circuit. For this, the target temperature TiCibie is calculated as a function of the second temperature T2 of the refrigerant at the outlet of the compressor 2, a temperature outside the vehicle Text and the third temperature T3 of the second airstream 9 taken downstream of the second heat exchanger 7, according to characterizations of the actuators Al and A3.

The Ticibie target temperature is thus determined according to the form [1] below:

[1] Where kl, k2 and k3 are coefficients,

Zc is an equivalent impedance of the actuator A1, "a" is a slope of the compressor power as a function of a compression ratio. The control unit 15 comprises a second controller 15b which is able to generate a second reference X2 for implementing the expansion device 12 from a comparison between the first pressure Pi of the refrigerant at the outlet of the compressor 2 and a Picibie target pressure of the refrigerant at the outlet of the compressor 2. Such a second setpoint X2 is adapted taking into account a first estimate Ei of the rate of an opening of the expansion device 12 to generate a second adapted setpoint X2 '. This second adapted setpoint X2 'is then applied to the expansion device 12, in order to control it.

If the coolant is a supercritical fluid, the second controller 15b determines the second setpoint X2 so that the HP high pressure is optimized. To obtain an optimized performance, the first estimate Ei takes into account the first pressure Pi of the refrigerant at the outlet of the compressor 2. It should be noted that the Picibie target pressure of the refrigerant at the outlet of the compressor 2 depends on the target temperature Ticible of refrigerant to be reached at the outlet of the first heat exchanger 3.

If the refrigerant fluid is a subcritical fluid, the second controller 15b also considers by convention that the Picibie target pressure of the refrigerant at the outlet of the compressor 2 depends on the target temperature Ticibie- The control unit 15 comprises a third controller 15c which is able to generate a third instruction X3 implementation of the compressor 2 from a comparison between the third temperature T3 of the second air flow 9 and a third target temperature T3Cibie of the second air flow 9, chosen by a user of the motor vehicle for his comfort. In other words, the third controller 15c delivers to the compressor 2 the third setpoint X3, so that the compressor 2 allows the third temperature T3 of the second air flow 9 to coincide at best with the third target temperature T3cibie of the second flow 9. This is how the process reaches its final goal by providing the required temperature in the passenger compartment, with an optimal coefficient of performance and by adapting the energy consumed by the subset formed by the first fan and the compressor. The control unit 15 comprises in particular a first computer 15 'which is able to determine the target pressure PiCibie of the refrigerant at the outlet of the compressor 2 from the first temperature Ti of the refrigerant at the outlet of the first heat exchanger 3 , measured or estimated. The control unit 15 comprises a second computer 15 "which is able to determine the first estimate Ei of the opening ratio of the expansion device 12 from the first pressure Pi of the refrigerant at the outlet of the compressor 2, measured or estimated. In other words, the expansion device 12 is controlled by the second computer 15 "and from the first estimate Ei of the opening rate of the expansion device 12. The first estimate Ei makes it possible to place the opening of the expansion device 12 depending on the pressure Pi at the outlet of the compressor, while the second computer 15 "corrects this first estimate Ei, if necessary depending on the HP optimum high pressure.

According to an exemplary implementation, the second computer 15 "performs two steps, of which a first step determines the rate of opening of the expansion device 12 as a function of the first pressure Pi of the refrigerant at the outlet of the compressor 2 and a second step of calculating the second adapted setpoint X2 ', as explained above. The control unit 15 comprises a third computer 15 '' which is able to determine the target temperature T iCibie refrigerant output of the first heat exchanger 3 from an optimization of the high pressure HP of the circuit of refrigerant 1 and a minimization of the total power consumed by the first fan 5 and the compressor 2.

Claims (15)

1. Method for implementing a refrigerant circuit (1) comprising a compressor (2), a first heat exchanger (3) associated with at least a first fan (5), the first heat exchanger (3) ) being arranged to allow a heat exchange between the refrigerant and a first air flow (4), a second heat exchanger (7) associated with at least a second fan (10), the second heat exchanger (7). ) being arranged to allow a heat exchange between the refrigerant and a second air flow (9), an expansion device (12) and a control unit (15) adapted to control at least a first actuator (Ai) of the first fan (5), characterized in that the method comprises at least: - a first step of determining a first temperature (Ti) of the refrigerant at the outlet of the first heat exchanger (3), - a second step of calculating a temperature-cib the (Ticibie) refrigerant at the outlet of the first heat exchanger (3) image of a minimum total power consumed by the compressor (2) and by the first fan (5), - a third step of comparing the first temperature (Ti) and the target temperature (TiCibie) of the refrigerant at the outlet of the first heat exchanger (3), - a fourth step of actuating the first actuator (Ai) of the first fan (5) according to the result of the comparison made in the third step. 2. The method of claim 1, wherein the fourth step is to adapt the actuation of the first actuator (Ai) of the first fan (5) so that the first temperature (Ti) corresponds to the target temperature (Ticibie) of the fluid. refrigerant. 3. The method of claim 1 or 2, wherein the target temperature (Ticibie) of the refrigerant is determined according to at least a second temperature (T2) of the refrigerant at the outlet of the compressor (2), a outside air temperature of the vehicle (Text) and a third temperature (T3) of the second air flow (9) taken downstream of the second heat exchanger (7). 4. Method according to any one of the preceding claims, during which there is provided a step of actuating a second actuator (A2) constituting the expansion device (12). 5. Method according to any one of the preceding claims, wherein the first step of determining the first temperature (T 1) of the refrigerant at the outlet of the first heat exchanger (3) is an estimate of this first temperature (T 1 ). 6. Method according to any one of the preceding claims, wherein the first step of determining the first temperature (T 1) of the refrigerant at the outlet of the first heat exchanger (3) is a measurement of the first temperature (T 1 ). 7. Method according to any one of the preceding claims, wherein the fourth actuating step comprises a step of calculating a first instruction (Xi) implementation of the first fan (5) to minimize the difference between the first temperature (T 1) and the target temperature (T iCjbie). 8. Method according to any one of the preceding claims, comprising a step of calculating a target pressure (Pidbie) of the refrigerant at the outlet of the compressor (2) which is a function of the target temperature (Ticibie) of the refrigerant . 9. The method of claim 8, comprising a step of comparing a first pressure (Pi) of the refrigerant at the outlet of the compressor (2) and the target pressure (P icibie) of the refrigerant. 10. The method of claim 9, comprising a step of calculating a second instruction (X2) implementation of the expansion device (12) to minimize the difference between the first pressure (Pi) and the target pressure (Picibie ) of the refrigerant at the outlet of the compressor (2). 11. Control unit (15) for implementing a method according to any one of the preceding claims, characterized in that the control unit (15) comprises a first controller (15a) which is able to generating a first instruction (Xi) for implementing the first fan (5) from a comparison between the first temperature (T 1) and the target temperature (T icibie) of the refrigerant at the outlet of the first heat exchanger (3). 12. Control unit (15) according to claim 11, wherein the control unit (15) comprises a second controller (15b) which is able to generate a second instruction (X2) implementation of the expansion device (12) from a comparison between a first pressure (Pi) of the refrigerant at the outlet of the compressor (2) and a target pressure (Pidbie) of the refrigerant at the outlet of the compressor (2). 13. Control unit (15) according to any one of claims 11 or 12, wherein the control unit (15) comprises a third controller (15c) which is able to generate a third setting (X3) setting implementation of the compressor (2) from a comparison between a third temperature (T3) of the second air flow (9) and a third target temperature (T3Cibie) of the second air flow (9). 14. Refrigerant circuit (1) for heat treating a passenger compartment of a motor vehicle, comprising a refrigerant circulated by a compressor (2), the circuit (1) comprising a first heat exchanger (3) associated with at least a first fan (5), the first heat exchanger (3) being arranged to allow a heat exchange between the refrigerant and a first air flow (4) outside the passenger compartment, and a second heat exchanger heat (7) associated with at least one second fan (10), the second heat exchanger (7) being arranged to allow a heat exchange between the refrigerant and a second air flow (9) delivered into the passenger compartment , the circuit (1) comprising an expansion device (12) of the refrigerant and a control unit (15) according to any one of claims 11 to 13. 15. Refrigerant circuit (1) according to claim 14, characterized in that the expansion device (12) comprises an ejector (13) and an expansion member (14).