Method for controlling a thermal conditioning system

Abstract

The invention relates to a method for controlling a thermal conditioning system (100) comprising a refrigerant circuit (10) successively comprising: - a compressor (7) configured to discharge refrigerant at high pressure, - a first heat exchanger (1) coupled to an outside air flow (Fe), - an expansion valve (21), - a second heat exchanger (2), the method comprising: - determining a value (HP) representative of the high pressure, - determining a temperature (TS1) of the refrigerant at the outlet of the first heat exchanger (1), - determining a setpoint value (C_HP) of the high pressure, - controlling a passage cross-section of the expansion valve (21) so that the value (HP) representative of the high pressure is equal to the setpoint value (C_HP), in which the setpoint value (C_HP) of the high pressure depends on: - the temperature (TS1) of the refrigerant at the outlet of the first heat exchanger (1),and - a quantity representative of the cooling power produced by the thermal conditioning system (100). Figure from the abstract: Figure 1,

Description

Title of the invention: Method for controlling a thermal conditioning system. Technical field.

[0001] The present invention relates to the field of thermal conditioning systems. Such systems can, for example, be fitted to motor vehicles and allow for the thermal regulation of various vehicle components, such as the passenger compartment or an electrical energy storage battery, when the vehicle is electrically powered. Heat exchange is managed primarily by the compression and expansion of a refrigerant circulating in a circuit containing several heat exchangers. A compressor forces the refrigerant into a high-pressure state, allowing its circulation within the circuit. The refrigerant can absorb or release heat at the various heat exchangers arranged in the circuit, thus completing a thermodynamic cycle.During the cycle, the high-pressure refrigerant can thus provide heat at a heat exchanger known as a heating exchanger. The evaporation of the low-pressure refrigerant at another heat exchanger allows for the absorption of heat and ensures cooling, in other words, the production of cooling capacity. Previous technique

[0002] Carbon dioxide can be used as a refrigerant, which minimizes the global warming potential (GWP) of the refrigerant used. During the thermodynamic cycle, the high-pressure refrigerant may be in a supercritical state at the outlet of the heat exchanger. In such a state, controlling the system can be challenging.

[0003] It is known to use the high-pressure value of the thermodynamic cycle as a control parameter for the system. Thus, the operation of the heat conditioning system can be regulated so that the high pressure of the thermodynamic cycle is equal to a setpoint value. This setpoint value can, for example, depend on the temperature of the refrigerant at the outlet of the first heat exchanger.

[0004] This type of formula gives satisfactory results when the cooling capacity to be supplied is moderate, i.e., on the order of 3 to 5 kilowatts. However, this type of formula does not allow for optimized operation for high cooling capacities, on the order of 10 to 20 kilowatts.

[0005] It is therefore desirable to have a control method that allows for the optimization of the efficiency of the thermal conditioning system for high cooling capacities. Summary

[0006] To this end, a method is proposed for controlling a thermal conditioning system comprising a refrigerant circuit configured to circulate a refrigerant, the refrigerant circuit comprising a main loop including, successively according to a direction of refrigerant circulation: - a compressor configured to deliver a high-pressure flow of refrigerant, - a first heat exchanger thermally coupled with an outside airflow, the outside airflow having a relative velocity with respect to the first exchanger, - a first expansion valve, - a second heat exchanger thermally coupled with a first heat transfer fluid, the second heat exchanger being configured to produce cooling capacity, the method comprising: (i) determine a value for the high pressure, (ii) determine a refrigerant temperature at the outlet of the first heat exchanger, (iii) determine a high-pressure setpoint value, (iv) control a passage section of the first pressure regulator so that the high-pressure value is equal to the determined setpoint value, in which the high-pressure setpoint value depends on: - the temperature of the refrigerant at the outlet of the first exchanger, and - a quantity representative of a cooling power produced by the thermal conditioning system, the setpoint value of the high pressure being determined by the formula: [Math. 1] C_HP = A*TS1-B + 12*(1- C*eï^) with : C_HP: high pressure setpoint value, in bar, TS1: refrigerant temperature at the outlet of the first heat exchanger, in °K, Q: refrigerant flow rate discharged by the compressor, in kg / h, A: first constant coefficient, B: second constant coefficient, C: correction factor depending on the relative speed of the outside airflow with respect to the first exchanger.

[0007] Taking into account, in determining the setpoint of the high pressure value of the thermodynamic cycle, the temperature of the refrigerant at the outlet of the first exchanger as well as a quantity representative of the total cooling power supplied by the thermal conditioning system makes it possible to improve the coefficient of performance of the latter.

[0008] The features listed in the following paragraphs can be implemented independently of each other or in any technically possible combination:

[0009] When the thermal conditioning system includes a single heat exchanger configured to provide cooling capacity, the cooling capacity produced by the thermal conditioning system is the cooling capacity produced by that heat exchanger.

[0010] When the thermal conditioning system includes several heat exchangers configured to provide cooling capacity, the cooling capacity produced by the thermal conditioning system is the sum of the cooling capacity produced by each of these heat exchangers.

[0011] When the thermal conditioning system includes two heat exchangers configured to each provide a cooling capacity, these two exchangers are, for example, arranged in parallel.

[0012] When the thermal conditioning system includes more than two heat exchangers configured to each provide a cooling capacity, these exchangers are, for example, arranged in parallel.

[0013] According to one aspect of the proposed process, the high-pressure setpoint value depends on: - the temperature of the refrigerant at the outlet of the first heat exchanger, - the flow rate of refrigerant discharged by the compressor, and - the relative speed of the outside airflow with respect to the first exchanger.

[0014] In other words, the representative quantity of a cooling power produced by the second exchanger is a function of the flow rate of refrigerant discharged by the compressor and of the relative speed of the outside air flow with respect to the first exchanger. Taking these three parameters into account when calculating the high-pressure setpoint of the thermodynamic cycle improves the coefficient of performance of the heat recovery ventilation system, thus reducing the energy consumed to provide a given cooling capacity. For a given cooling capacity, the compressor speed can be lowered, thereby reducing its noise level.

[0015] The compressor is configured to draw in refrigerant at a first pressure called low pressure, and discharge a flow of refrigerant at a second pressure called high pressure, the high pressure being greater than the low pressure.

[0016] The first heat exchanger is configured to cool the high-pressure refrigerant fluid from the compressor.

[0017] The first expansion valve is configured to expand the refrigerant fluid coming from the first exchanger.

[0018] The second heat exchanger is configured to evaporate at least part of the refrigerant from the first expansion valve. In other words, the second heat exchanger is configured to operate as a refrigerant evaporator.

[0019] The low-pressure refrigerant fluid from the second heat exchanger is drawn in by the compressor.

[0020] According to one embodiment, the first heat exchanger is configured to exchange heat with an outside airflow.

[0021] According to one embodiment, the first heat exchanger is configured to exchange heat with a heat transfer fluid circulating in a closed heat transfer fluid circuit, the heat transfer fluid circuit comprising a heat exchanger configured to exchange heat with an outside airflow.

[0022] The first heat transfer fluid can be an airflow from inside the passenger compartment of the motor vehicle.

[0023] According to one embodiment, the second heat exchanger is configured to exchange heat with an internal airflow.

[0024] According to one aspect of the proposed process, the refrigerant fluid is in a supercritical state at the outlet of the first exchanger.

[0025] The refrigerant is of type R744.

[0026] According to an example of implementation of the proposed process, the main loop of the refrigerant circuit includes an internal exchanger configured to allow heat exchange between the high-pressure refrigerant circulating between the first exchanger and the first expansion valve and the low-pressure refrigerant circulating between the second exchanger and a compressor inlet.

[0027] The internal heat exchanger includes a first heat exchange section located on the main loop between the first exchanger and the first expansion valve. The internal heat exchanger includes a second heat exchange section located on the main loop between the second exchanger and a compressor inlet.

[0028] The main loop of the refrigerant circuit may include a refrigerant accumulation device located downstream of the second exchanger and upstream of the internal exchanger.

[0029] The refrigerant fluid accumulation device is arranged between an outlet of the second exchanger and the second heat exchange section of the internal heat exchanger.

[0030] According to an example of implementation of the control method, the refrigerant circuit includes a bypass branch arranged in parallel with the first expansion valve and the second exchanger, the bypass branch successively comprising a second expansion valve and a third heat exchanger thermally coupled with a second heat transfer fluid.

[0031] In other words, the refrigerant circuit includes a branch connecting a first connection point located on the main loop downstream of the first exchanger and upstream of the first expansion valve to a second connection point located on the main loop downstream of the second exchanger upstream of the compressor, the branch successively comprising a second expansion valve and a third heat exchanger thermally coupled with a second heat transfer fluid.

[0032] According to one embodiment, the second heat transfer fluid is a heat transfer fluid circulating in a heat transfer fluid circuit, and the third heat exchanger is thermally coupled with an element of an electric drivetrain of a motor vehicle, via the heat transfer fluid circulating in the heat transfer fluid circuit.

[0033] The third heat exchanger is configured to operate as a refrigerant fluid evaporator.

[0034] According to one embodiment, the element of the vehicle's electric powertrain includes an electrical energy storage battery.

[0035] Alternatively, or in addition, the element of the vehicle's electric drive chain includes an electric vehicle traction motor.

[0036] Alternatively, or in a complementary manner, the element of the vehicle's electric traction chain includes an electronic control unit for the vehicle's electric traction motor.

[0037] The refrigerant fluid accumulation device is located downstream of the second connection point and upstream of the second heat exchange section of the internal heat exchanger.

[0038] This formula makes it possible to improve the coefficient of performance of the thermal conditioning system during the operating phases in which a high cooling power is supplied, while being simple to calculate.

[0039] According to one aspect of the proposed control method, the first constant coefficient is between 2.3 and 2.7, preferably between 2.4 and 2.6, more preferably between 2.55 and 2.65.

[0040] The second constant coefficient is between 2 and 6, preferably between 3 and 5, more preferably between 3.5 and 4.5.

[0041] According to one aspect of the control process, the correction factor is determined by the formula: C = 1 - 0.1 * ^ avec: V1: relative velocity of the outside airflow Fe with respect to the first exchanger.

[0042] The control method comprises the substep: - determine the relative velocity of the outside airflow with respect to the first heat exchanger.

[0043] According to one embodiment of the proposed control method, the relative velocity of the outside airflow with respect to the first heat exchanger is determined from a forward speed of the vehicle.

[0044] According to an example of implementation of the control method, the thermal conditioning system includes a motor-fan unit configured to increase a relative speed of the outside airflow with respect to the first exchanger, and the relative speed of the outside airflow with respect to the first exchanger is determined from a forward speed of the vehicle and from a parameter representative of a rotational speed of the motor-fan unit.

[0045] According to an example of implementation of the proposed control method, the parameter representing a rotation speed of the motor-fan group is a duty cycle of control of an electric motor driving a fan of the motor-fan group.

[0046] The control process comprises the substep: - determine the temperature of the refrigerant fluid at the outlet of the first exchanger.

[0047] The control process comprises the substep: - determine the flow rate of refrigerant discharged by the compressor.

[0048] The refrigerant flow rate discharged by the compressor is determined from a density of the refrigerant at the compressor inlet, a compressor rotation speed and a compressor discharge model.

[0049] According to one embodiment, the density of the refrigerant at the compressor inlet is determined from a pressure of the refrigerant at the inlet of the accumulation device, from a temperature of the refrigerant at the compressor inlet and from an equation of state of the refrigerant.

[0050] According to one embodiment, the density of the refrigerant at the compressor inlet is determined from a refrigerant inlet pressure of the compressor, based on a temperature of the refrigerant fluid at the compressor inlet and based on an equation of state of the refrigerant fluid.

[0051] According to an example of implementation of the proposed process, the second exchanger provides cooling power and the third exchanger is thermally inactive.

[0052] According to another example of implementation of the proposed process, the second exchanger is thermally inactive and the third exchanger provides cooling power.

[0053] According to yet another example of implementation of the proposed process, the second exchanger provides a first cooling power and the third exchanger provides a second cooling power.

[0054] The invention also relates to a computer program stored in memory and configured to implement the process described above.

[0055] The invention also relates to a thermal conditioning system for a motor vehicle, comprising a refrigerant circuit having a main loop comprising successively, according to a direction of refrigerant flow: - a compressor configured to deliver a high-pressure flow of refrigerant, - a first heat exchanger thermally coupled with an outside airflow, the outside airflow having a relative velocity with respect to the first exchanger, - a first expansion valve, - a second heat exchanger thermally coupled with a first heat transfer fluid, - an electronic control unit configured to implement the process described above.

[0056] According to one embodiment of the thermal conditioning system, the main loop of the refrigerant circuit comprises: - an internal heat exchanger configured to allow heat exchange between the high-pressure refrigerant circulating between the first heat exchanger and the first expansion valve, and the low-pressure refrigerant circulating between the second heat exchanger and a compressor inlet, - a refrigerant fluid accumulation device located downstream of the second heat exchanger and upstream of the internal heat exchanger, and wherein the refrigerant circuit comprises a branch connecting a first connection point located on the main loop downstream of the first heat exchanger and upstream of the first expansion valve to a second connection point located on the main loop downstream of the second heat exchanger upstream of the compressor, the branch successively comprising a a second expansion valve and a third heat exchanger thermally coupled with a second heat transfer fluid. Brief description of the drawings

[0057] Other features, details and advantages will become apparent upon reading the detailed description below, and upon analysis of the accompanying drawings, on which:

[0058] [Fig-1] is a schematic view of a thermal conditioning system according to a first example of the implementation of the invention,

[0059] [Fig.2] is a schematic view of a thermal conditioning system according to a second example of an implementation of the invention,

[0060] [Fig.3] is a schematic view of an embodiment of the system of thermal conditioning of the [Fig.2],

[0061] [Fig.4] is a schematic view of a variant of the conditioning system thermal of the [Fig.3],

[0062] [Fig.5] is a schematic view illustrating the installation of the system of thermal conditioning in a motor vehicle,

[0063] [Fig.6] is a diagram illustrating the operation of the system of thermal conditioning of [Fig.2] during the implementation of the proposed process,

[0064] [Fig.7] illustrates the acquisition of the main parameters used by the process propose,

[0065] [Fig.8] is a block diagram of the proposed process. Description of the implementation methods

[0066] To facilitate reading the figures, the various elements are not necessarily drawn to scale. In these figures, identical elements bear the same reference numerals. Certain elements or parameters may be indexed, that is, designated, for example, as first element or second element, or first parameter and second parameter, etc. This indexing aims to differentiate similar, but not identical, elements or parameters. This indexing does not imply a priority of one element or parameter over another, and the designations may be interchanged.

[0067] In the following description, the expression "a first element upstream of a second element" means that the first element is placed before the second element with respect to the direction of flow, or path, of a fluid. Similarly, the term "a first element downstream of a second element" means that the first element is placed after the second element with respect to the direction of flow, or path, of the fluid in question. In the case of the refrigerant circuit, the term "a first element is upstream of a second element" means that the refrigerant flows successively through the first element, then the second element, without passing through the compression device. In other words, the refrigerant leaves the compression device, possibly passes through one or more elements, then passes through the first element, then the second element, then returns to the compression device, possibly after passing through other elements.

[0068] The expression "a second element is placed between a first element and a third element" means that the shortest path to go from the first element to the third element passes through the second element.

[0069] When it is specified that a subsystem includes or comprises a given element, this does not exclude the presence of other elements in that subsystem. Thus, the term "includes an element" means, in the context of the request, "includes at least one element".

[0070] The thermal conditioning system 100 that will be described can be implemented on a motor vehicle 50. The thermal conditioning system 100 includes an electronic control unit 60 that receives information from various sensors, notably those measuring the characteristics of the refrigerant at various points in the circuit. The electronic control unit 60 also receives instructions from the occupants of the vehicle 50, such as the desired temperature inside the passenger compartment. The electronic control unit can also receive instructions from other electronic subsystems, such as the battery management system for electrical energy storage. The electronic control unit 60 implements control laws to operate the various actuators, in order to control the thermal conditioning system 100 and ensure compliance with the received instructions.

[0071] A compression device 7 allows a refrigerant to circulate in a refrigerant circulation circuit 10. The refrigerant circuit 10 forms a closed loop in which the refrigerant can circulate. The refrigerant circuit 10 is leak-proof when it is in its nominal operating condition, that is, without any faults or leaks. Each connection point of the circuit 10 allows the refrigerant to flow into one or the other of the circuit sections that converge at that connection point. The distribution of the refrigerant between the circuit sections that converge at a connection point is achieved by opening or closing the shut-off valves, check valves, or expansion devices included on each of these sections. In other words, each connection point is a means of redirecting the refrigerant arriving at that connection point.Various shut-off valves and check valves thus allow the refrigerant to be selectively directed into the different branches of the refrigerant circuit, in order to ensure different operating modes, as will be described later.

[0072] Each refrigerant expansion device, also called an expansion valve, can be an electronic expansion valve. In an electronic expansion valve, the passage area through which the refrigerant passes can be continuously adjusted between a closed position and a maximum open position. To achieve this, an electronic control module for the expansion valve drives an electric motor that moves a movable shutter, thus controlling the passage area available to the refrigerant.

[0073] The term "interior airflow Fi" refers to an airflow directed towards the passenger compartment of the motor vehicle. This interior airflow Fi may circulate within a heating, ventilation, and / or air conditioning (HVAC) system. This system is not shown in the various figures. A first motor-fan unit, not shown, is located within the HVAC system to increase the flow rate of the interior airflow Fi if necessary.

[0074] The term "external airflow Fe" refers to an airflow that is not directed towards the vehicle's passenger compartment. In other words, this airflow Fe remains outside the vehicle's passenger compartment. A second motor-fan unit, also not shown, can be activated to increase the flow rate of the external airflow Fe if necessary. The airflow provided by both the first and second motor-fan units can be adjusted in real time according to heat exchange requirements, for example, by the electronic control unit of the climate control system 100.

[0075] The term "first exchanger" is equivalent to the term "first heat exchanger". Similarly, the term "internal exchanger" is equivalent to the term "internal heat exchanger". The term "storage device" is equivalent to the term "refrigerant storage device".

[0076] The heat transfer fluid circuit(s) also form one or more closed and sealed circuits in which a heat transfer fluid can circulate.

[0077] A first example of a thermal conditioning system 100 for a motor vehicle 50 is shown schematically in [Fig.1]. The thermal conditioning system 100 comprises a refrigerant circuit 10 having a main loop A comprising successively, according to a direction of refrigerant flow: - a compressor 7 configured to deliver a flow rate Q of refrigerant at high pressure, - a first heat exchanger 1 thermally coupled with an outside air flow Fe, the outside air flow Fe having a relative velocity VI with respect to the first heat exchanger 1, - a first regulator 21, - a second heat exchanger 2 thermally coupled with a first heat transfer fluid Fl, - an electronic control unit 60 configured to implement a process which will be described in detail below.

[0078] The compressor 7 is configured to draw in refrigerant fluid at a first pressure called low pressure BP, and discharge a flow Q of refrigerant fluid at a second pressure called high pressure HP, the high pressure HP being greater than the low pressure BP.

[0079] The first exchanger 1 can receive refrigerant fluid discharged by the compressor 7 in a state of high pressure HP and high temperature. The first heat exchanger 1 is configured to cool the high-pressure refrigerant HP from the compressor 7. The first exchanger 1 is thus configured to operate as a refrigerant fluid cooler. The heat from the refrigerant fluid coming from the compressor 7 is dissipated via the first exchanger 1 into the outside airflow Fe.

[0080] The first expansion valve 21 is configured to expand the refrigerant fluid coming from the first exchanger 1. The first expansion valve 21 is, for example, an electronic expansion valve. In an electronic expansion valve, the passage area allowing the refrigerant to pass through can be continuously adjusted between a minimum and a maximum opening position. To achieve this, an electronic control module drives an electric motor that moves a movable shutter, thus controlling the passage area available to the refrigerant. The passage section of an electronic regulator can thus be controlled in real time.

[0081] The second heat exchanger 2 can receive refrigerant fluid expanded by the first expansion valve 21 after being cooled by the first heat exchanger 1. The second heat exchanger 2 can therefore receive refrigerant flow in a low-pressure state. The second heat exchanger 2 is configured to evaporate at least part of the refrigerant fluid from the first expansion valve 21. In other words, the second heat exchanger 2 is configured to operate as a refrigerant evaporator. The second heat exchanger 2 can thus produce a cooling capacity, corresponding to the thermal power taken from the first heat transfer fluid Fl during the evaporation of the refrigerant fluid.

[0082] The low-pressure refrigerant fluid from the second heat exchanger 2 is drawn in by the compressor 7.

[0083] In this first embodiment, the thermal conditioning system 100 includes a single exchanger capable of providing cooling power, which is the second exchanger 2.

[0084] Fig. 2 schematically represents a second example of a thermal conditioning system 100. In this second embodiment, the refrigerant circuit 10 includes a branch B arranged in parallel with the first expansion valve 21 and the second heat exchanger 2. The branch B includes successively a second expansion valve 22 and a third heat exchanger 3 thermally coupled with a second heat transfer fluid F2.

[0085] In other words, the refrigerant circuit 10 includes a branch B connecting a first connection point 11 located on the main loop A downstream of the first heat exchanger 1 and upstream of the first expansion valve 21 to a second connection point 12 located on the main loop A downstream of the second heat exchanger 2 upstream of the compressor 7. The branch branch B includes successively a second expansion valve 22 and a third heat exchanger 3 thermally coupled with a second heat transfer fluid F2.

[0086] Like the second exchanger 2, the third exchanger 3 can receive refrigerant fluid expanded by a second expansion valve 22 after having been cooled by the first exchanger 1. The third exchanger 3 can therefore receive refrigerant flow in a low-pressure state. The third heat exchanger 3 is thus configured to operate as a refrigerant fluid evaporator. The third heat exchanger 3 can thus produce a cooling capacity, corresponding to the thermal power taken from the second heat transfer fluid F2 during the evaporation of the refrigerant.

[0087] According to examples of embodiments not shown, the refrigerant fluid circuit 10 may include other heat exchangers configured to operate as evaporators and thus be able to produce cooling power.

[0088] The thermal coupling between the first heat exchanger 1 and the outside airflow Fe can be ensured in different ways.

[0089] According to the first and second examples, illustrated in Figures 1 and 2, the first heat exchanger 1 is configured to exchange heat with an outside airflow Fe. The outside airflow Fe is in contact with fins attached to the refrigerant circulation channels in the first exchanger 1. The thermal coupling between the outside airflow Fe and the first exchanger 1 is then said to be direct.

[0090] According to one embodiment, illustrated in [Fig. 4], the first heat exchanger 1 is configured to exchange heat with a heat transfer fluid circulating in a closed heat transfer fluid circuit 20. The heat transfer fluid circuit 20 includes a heat exchanger IA configured to exchange heat with an outside air flow Fe. The heat transfer fluid circulating in circuit 20 is, for example, a mixture of water and glycol. A circulation pump, not shown, allows the heat transfer fluid to circulate in circuit 20.

[0091] Fig. 3 and Fig. 4 respectively illustrate a first embodiment and a second embodiment of the example in Fig. 2.

[0092] According to these embodiments, the first heat transfer fluid Fl is an interior airflow Fi to the passenger compartment of the motor vehicle. The second heat exchanger 2 thus allows the vehicle's passenger compartment to be cooled.

[0093] According to these embodiments, the second heat exchanger 2 is configured to exchange heat with an internal airflow Fi. In other words, the thermal coupling between the second heat exchanger 2 and the internal airflow Fi is direct.

[0094] According to these embodiments, the second heat transfer fluid F2 is a heat transfer fluid circulating in a heat transfer fluid circuit 40. The third heat exchanger 3 is thermally coupled with an element 25 of an electric drive chain of the motor vehicle 50, via the heat transfer fluid circulating in the heat transfer fluid circuit 40.

[0095] The third exchanger 3 thus allows the element 25 of the electric traction chain to be cooled. The heat dissipated during the operation of element 25 of the vehicle's electric drive chain is transferred to the heat transfer fluid of circuit 40. The heat transfer fluid is cooled by the evaporation of the refrigerant in the third heat exchanger 3. The third exchanger 3 allows heat exchange between the heat transfer fluid and the refrigerant fluid.

[0096] According to one embodiment, element 25 of the vehicle's electric drive chain includes an electrical energy storage battery. Alternatively, or additionally, element 25 of the vehicle's electric powertrain may include a vehicle electric traction motor. Alternatively, or additionally, element 25 of the vehicle's electric powertrain may include an electronic control unit for the vehicle's electric traction motor.

[0097] According to the first embodiment, illustrated in [Fig. 1], the main loop A of the refrigerant circuit 10 includes an internal heat exchanger 5 configured to allow heat exchange between: - the high-pressure refrigerant circulating between the first heat exchanger 1 and the first expansion valve 21, and - the low-pressure refrigerant fluid circulating between the second heat exchanger 2 and an inlet 7A of the compressor 7.

[0098] The internal heat exchanger 5 includes a first heat exchange section 5A arranged on the main loop A between the first exchanger 1 and the first expansion valve 21. The internal heat exchanger 5 has a second heat exchange section 5B arranged on the main loop A between the second exchanger 2 and an inlet 7A of the compressor 7.

[0099] The first heat exchange section 5A thus receives high-pressure refrigerant fluid from the first heat exchanger 1. The second heat exchange section 5B receives low-pressure refrigerant fluid from the second heat exchanger 2.

[0100] The main loop A of the refrigerant circuit 10 includes a refrigerant accumulation device 9 located downstream of the second exchanger 2 and upstream of the internal exchanger 5.

[0101] The refrigerant accumulation device 9 is a refrigerant accumulator. It compensates, depending on the operating conditions, for variations in the quantity of refrigerant circulating in the refrigerant circuit.

[0102] The refrigerant fluid accumulation device 9 is disposed between an outlet 2b of the second exchanger 2 and the second heat exchange section 5B of the internal heat exchanger 5.

[0103] As illustrated in [Fig.2], when the thermal conditioning system includes a bypass branch B, the refrigerant fluid accumulation device 9 is disposed downstream of the second connection point 12 and upstream of the second heat exchange section 5B of the internal heat exchanger 5.

[0104] According to the second example of the thermal conditioning system 100, illustrated in [Fig. 2], the main loop A of the refrigerant circuit 10 comprises: - an internal heat exchanger 5 configured to allow heat exchange between the high-pressure refrigerant circulating between the first heat exchanger 1 and the first expansion valve 21 and the low-pressure refrigerant circulating between the second heat exchanger 2 and an inlet 7A of the compressor 7, - a refrigerant accumulation device 9 disposed downstream of the second heat exchanger 2 and upstream of the internal heat exchanger 5, and the refrigerant circuit 10 includes a branch B connecting a first connection point 11 located on the main loop A downstream of the first heat exchanger 1 and upstream of the first expansion valve 21 to a second connection point 12 located on the main loop A downstream of the second heat exchanger 2 upstream of the compressor 7. The branch B includes successively a second expansion valve 22 and a third heat exchanger 3 thermally coupled with a second heat transfer fluid F2.

[0105] Fig. 5 schematically illustrates the arrangement of the main elements of the thermal conditioning system 100 in a vehicle 50. The first interchange 1 is located in the front of the vehicle, just behind the grille. The first exchanger 1 thus directly receives the outside air flow Fe.

[0106] We will now describe a method for optimizing the operation of the thermal conditioning system 100 described.

[0107] A method for controlling a thermal conditioning system 100 comprising a refrigerant circuit 10 configured to circulate a refrigerant is thus proposed, the refrigerant circuit 10 comprising a main loop A comprising successively, according to a direction of refrigerant circulation: - a compressor 7 configured to deliver a flow rate Q of refrigerant at high pressure, - a first heat exchanger 1 thermally coupled with an outside air flow Fe, the outside air flow Fe having a relative velocity VI with respect to the first heat exchanger 1, - a first regulator 21, - a second heat exchanger 2 thermally coupled with a first heat transfer fluid Fl, the second heat exchanger 2 being configured to produce cooling capacity, the process comprising: (i) determine a high-pressure (HP) value, (ii) determine a temperature TS1 of the refrigerant fluid at the outlet of the first heat exchanger 1, (iii) determine a high-pressure setpoint value C_HP, (iv) control a passage section of the first pressure regulator 21 such that the high-pressure value HP is equal to the determined setpoint value C_HP, where the high-pressure setpoint value C_HP depends on: - of the temperature TS1 of the refrigerant at the outlet of the first heat exchanger 1, and - of a quantity representative of a cooling power produced by the thermal conditioning system 100.

[0108] Taking into account, in determining the setpoint of the high pressure value of the thermodynamic cycle, the temperature of the refrigerant fluid at the outlet of the first exchanger 1 as well as a quantity representative of the total cooling power supplied by the thermal conditioning system makes it possible to improve the coefficient of performance of the latter.

[0109] When the thermal conditioning system 100 includes a single heat exchanger configured to provide cooling capacity, the cooling capacity produced by the thermal conditioning system 100 is the cooling capacity produced by that single heat exchanger.

[0110] In this case, the heat exchanger configured to provide cooling power is the second exchanger 2.

[0111] When the thermal conditioning system 100 includes several heat exchangers configured to provide cooling capacity, the cooling capacity produced by the thermal conditioning system 100 is the sum of the cooling capacity produced by each of these heat exchangers.

[0112] When the thermal conditioning system 100 includes two heat exchangers configured to each provide a cooling capacity, these two exchangers are, for example, arranged in parallel, as is the case in the second embodiment, illustrated in [Fig.2], and in the corresponding embodiments, illustrated in [Fig.3] and [Fig.4]. The total cooling capacity produced by the thermal conditioning system 100 is the sum of the cooling capacity produced by the second exchanger 2 and the cooling capacity produced by the third exchanger 3.

[0113] When the thermal conditioning system 100 includes more than two heat exchangers configured to each provide a cooling capacity, these exchangers are, for example, arranged in parallel.

[0114] According to one aspect of the proposed process, the setpoint value C_HP of the high pressure depends on: - the temperature TS1 of the refrigerant at the outlet of the first heat exchanger 1, - the flow rate Q of refrigerant discharged by the compressor 7, and - of the relative speed VI of the outside air flow Fe with respect to the first exchanger 1.

[0115] In other words, the quantity representing a cooling capacity produced by the second heat exchanger 2 is a function of several variables, these variables being: - the temperature TS1 of the refrigerant at the outlet of the first heat exchanger 1, - the flow rate Q of refrigerant discharged by the compressor 7, and - the relative velocity VI of the outside airflow Fe with respect to the first heat exchanger 1. Taking these three parameters into account in the calculation of the setpoint value C_HP for the high pressure of the thermodynamic cycle improves the coefficient of performance of the heat conditioning system, and therefore reduces the energy consumed by the heat conditioning system to provide a given cooling capacity. Furthermore, for a given cooling capacity, the compressor speed 7 can be lowered, thus reducing its noise level.

[0116] The refrigerant flow rate Q is a mass of refrigerant per unit time. The flow rate is expressed in kilograms per hour.

[0117] The relative velocity VI of the outside air flow Fe with respect to the first exchanger 1 corresponds to the velocity of the outside air flow Fe with respect to the first exchanger 1. This relative velocity V1 is expressed in meters per second.

[0118] The high pressure setpoint value C_HP is expressed in bar.

[0119] The temperature TS1 of the refrigerant at the outlet of the first heat exchanger 1 is expressed in degrees Kelvin. (°K)

[0120] The setpoint value C_HP of the high pressure is thus a function of: - of the temperature TS1 of the refrigerant fluid coming from the first exchanger 1, - of the total flow rate Q of refrigerant discharged by compressor 7, and - of the velocity VI of the outside air flow Fe relative to the first exchanger 1.

[0121] According to one aspect of the proposed process, the refrigerant fluid is in a supercritical state at the outlet of the first exchanger 1.

[0122] The refrigerant here is of type R744. The refrigerant designated by the term R744 can also be referred to as CO2, or carbon dioxide.

[0123] Fig. 6 illustrates the thermodynamic cycle carried out, in the case where the proposed process is implemented on a thermal conditioning system according to the first example. The diagram represents the pressure P of the refrigerant fluid as a function of its enthalpy H. The s curve is the characteristic saturation curve of the refrigerant used, here R744.

[0124] On [Fig.6], point A_7A corresponds to the state of the refrigerant fluid drawn in at low pressure BP at the inlet of compressor 7. Point A_7B corresponds to the state of the refrigerant fluid discharged at high pressure HP at the outlet of compressor 7. Point A_1B corresponds to the state of the refrigerant at the outlet of the first heat exchanger 1. At this point, the refrigerant is at high pressure and has been cooled by the airflow. external Fe. The enthalpy variation during this cooling is illustrated by the length of the line designated by Cl. Point A_21B corresponds to the state of the refrigerant fluid at the inlet of the second exchanger 2, i.e. after expansion by the first expansion valve 21. Point A_21B corresponds to the state of the refrigerant fluid at the outlet of the second exchanger 2, that is to say after heat exchange in the second exchanger 2 and before being compressed again by the compressor 7. At this point, the refrigerant has provided cooling power at the level of the second exchanger 2. The enthalpy change in the second exchanger 2 is illustrated by the length of the line designated by C2. The HP value of the high pressure is equal to the desired C_HP setpoint.

[0125] According to one implementation of the proposed control method, the setpoint value C_HP of the high pressure HP is determined by the formula: [Math. 1] C_HP = A*TS1-B + 12^1- C*ew) with : C_HP: setpoint value C_HP of the high pressure, in bar, TS1: temperature TS1 of the refrigerant at the outlet of the first heat exchanger 1, in °K, Q: flow rate Q of refrigerant discharged by compressor 7, in kg / h, and where: A is a first constant coefficient, B is a second constant coefficient, C is a correction factor dependent on the relative velocity VI of the outside air flow Fe with respect to the first exchanger 1.

[0126] This formula makes it possible to improve the coefficient of performance of the thermal conditioning system, particularly during operating phases in which a high cooling capacity is supplied, for example, a cooling capacity on the order of 10 to 20 kilowatts (kW). This formula also has the advantage of remaining reasonably simple to calculate, which avoids requiring excessive computing resources from the electronic unit 60 implementing the process.

[0127] In the above formula, the sign 'e' denotes the exponential function, that is to say the inverse function of the natural logarithm function.

[0128] According to one aspect of the proposed control method, the first constant coefficient A is between 2.3 and 2.7. The first constant coefficient A is preferably between 2.4 and 2.6. The first constant coefficient A is more preferably between 2.55 and 2.65.

[0129] The second constant coefficient B is between 2 and 6. The second constant coefficient B is preferably between 3 and 5. The second constant coefficient B is more preferentially between 3.5 and 4.5.

[0130] According to one aspect of the control process, the correction factor C is determined by the formula: C = 1 - 0.1 * ^ avec: V1: relative velocity of the outside airflow Fe with respect to the first exchanger 1. V1 is expressed in meters per second, (m / s)

[0131] The speed V1 is for example ensured by a motor-fan unit which makes it possible to maintain the value of the speed VI above 0.5m / s.

[0132] The control process thus comprises the following substep: - determine the relative velocity VI of the outside air flow Fe with respect to the first exchanger 1.

[0133] According to one embodiment of the proposed control method, the relative velocity V1 of the outside airflow Fe with respect to the first exchanger 1 is determined from a forward speed V of the vehicle.

[0134] The forward speed V of the vehicle is the speed of movement of the vehicle structure 50 relative to the road, symbolized by the sign R on the [Fig.5]. The forward speed V of the vehicle is, for example, determined from the rotational speed of the vehicle's wheels. The vehicle's forward speed V is, for example, determined by the electronic unit managing the vehicle's braking. The vehicle's forward speed V is communicated to the electronic unit 60 of the thermal conditioning system 100 via a multiplexed communication network within the vehicle.

[0135] According to an example of implementation of the control method, the thermal conditioning system 100 includes a motor-fan unit 15 configured to increase a relative velocity of the outside airflow Fe with respect to the first exchanger 1. The relative velocity VI of the outside airflow Fe with respect to the first exchanger 1 is determined from a forward speed V of the vehicle and from a parameter representative of a rotation speed of the motor-fan unit 15.

[0136] The motor-fan unit 15 makes it possible to generate an outside air flow Fe, directed towards the first exchanger 1. A sufficient air flow Fe is thus obtained even when the vehicle is stopped or moving at low speed. When the thermal coupling between the first exchanger 1 and the outside airflow Fe is of the indirect type, the motor-fan unit 15 is arranged opposite the exchanger IA of the heat transfer fluid circuit 20.

[0137] According to an example of implementation of the proposed control method, the parameter representing a rotation speed of the motor-fan group 15 is a duty cycle of control of an electric motor driving a fan of the motor-fan group 15.

[0138] The motor-fan group 15 is for example axial flow.

[0139] The relative speed VI of the outside airflow Fe with respect to the first exchanger 1 is a function of the two variables: forward speed V of the vehicle and a parameter representing a rotation speed of the motor-fan unit 15. The relative velocity VI of the outside airflow Fe with respect to the first heat exchanger 1 can, for example, be obtained by reading a two-dimensional table. The first dimension of the table corresponds to the forward velocity V, and the second dimension corresponds to the rotational speed of the motor-fan unit 15.

[0140] The control process comprises the substep: - determine the temperature TS1 of the refrigerant at the outlet of the first heat exchanger 1.

[0141] A temperature sensor, not shown in the figures, can be placed on The first heat exchanger 1, at the refrigerant outlet. The temperature sensor can also be placed near the second heat exchanger 2, on a section of the circuit downstream of the second heat exchanger 2. The temperature sensor includes a sensitive element whose electrical output signal depends on the temperature.

[0142] The control process comprises the substep: - determine the flow rate Q of refrigerant discharged by compressor 7.

[0143] The flow rate Q of refrigerant discharged by the compressor 7 is determined from a density d of the refrigerant at the inlet 7A of the compressor 7, a rotational speed of the compressor 7 and a discharge model of the compressor 7.

[0144] According to an example embodiment, the density d of the refrigerant fluid at the inlet 7A of the compressor 7 is determined from a pressure P9 of the refrigerant fluid at the inlet of the accumulation device 9, from a temperature T7A of the refrigerant fluid at the inlet of the compressor 7 and from an equation of state of the refrigerant fluid.

[0145] The equation of state can, for example, be the ideal gas law. A real gas type equation of state can also be used.

[0146] In this embodiment, the refrigerant circuit 10 is equipped with a pressure sensor located on the portion of the circuit situated near the device accumulation 9, and a temperature sensor disposed on a portion of circuit located near the inlet 7A of compressor 7.

[0147] According to one embodiment, the density d of the refrigerant fluid at the inlet 7A of the compressor 7 is determined from: - of a pressure P7A of the refrigerant fluid at the inlet of compressor 7, - of a temperature T7A of the refrigerant fluid at the inlet of compressor 7, and from - an equation of state of the refrigerant fluid.

[0148] According to this variant, the refrigerant circuit 10 is equipped with a pressure sensor disposed on the portion of the circuit located near the inlet of the compressor 7. The pressure sensor may, for example, be a combined sensor jointly measuring the pressure and temperature of the refrigerant.

[0149] The pressure P7A of the refrigerant fluid at the inlet of the compressor 7 corresponds to the value BP of the low pressure of the thermodynamic cycle.

[0150] On [Fig.7], the dashed reference signs schematically indicate where in the refrigerant circuit 10 the various physical parameters listed above are determined.

[0151] According to an example of implementation of the proposed process, the second exchanger 2 provides cooling power and the third exchanger 3 is thermally inactive. This operating case corresponds to cooling only the passenger compartment of the vehicle.

[0152] According to another example of implementation of the proposed process, the second exchanger 2 is thermally inactive and the third exchanger 3 provides cooling power. This operating case corresponds to cooling only of element 25 of the vehicle's electric drive chain.

[0153] According to yet another example of implementation of the proposed process, the second exchanger 2 provides a first cooling power and the third exchanger 3 provides a second cooling power. This operating case corresponds to a joint cooling of the vehicle's passenger compartment and of element 25 of the vehicle's electric powertrain.

[0154] When the second exchanger 2 and the third exchanger 3 each generate a cooling capacity, the respective degree of opening of the first expansion valve 21 and the second expansion valve 22 allows control of the distribution of the total cooling capacity between the two exchangers 2,3.

[0155] The degree of opening of the first expansion valve 21 allows control of the high-pressure value of the thermodynamic cycle, and the degree of opening of the second expansion valve 22 allows control of the temperature value of the heat transfer fluid at the outlet of the third exchanger 3.

[0156] The value of the so-called high pressure is for example between 45 bar and 130 bar. The value of the so-called low pressure is, for example, between 33 bar and 65 bar.

[0157] The described method can be coded in the form of a computer program. The computer program is stored in memory and is configured to implement the described process.

Claims

Demands

1. A method for controlling a thermal conditioning system (100) comprising a refrigerant circuit (10) configured to circulate a refrigerant, the refrigerant circuit (10) comprising a main loop (A) comprising successively, in a direction of refrigerant flow: - a compressor (7) configured to deliver a flow rate (Q) of refrigerant at high pressure, - a first heat exchanger (1) thermally coupled with an outside air flow (Fe), the outside air flow (Fe) having a relative velocity (VI) with respect to the first exchanger (1), - a first expansion valve (21), - a second heat exchanger (2) thermally coupled with a first heat transfer fluid (Fl), the second heat exchanger (2) being configured to produce cooling capacity, the process comprising: (i) determine a value (HP) for the high pressure, (ii) determine a temperature (TS1) of the refrigerant fluid at the outlet of the first heat exchanger (1), (iii) determine a setpoint value (C_HP) for the high pressure, (iv) control a passage section of the first pressure regulator (21) such that the value (HP) of the high pressure is equal to the determined setpoint value (C_HP), in which the setpoint value (C_HP) of the high pressure depends on: - the temperature (TS1) of the refrigerant at the outlet of the first heat exchanger (1), and - of a quantity representative of a cooling power produced by the thermal conditioning system (100), characterized in that the setpoint value (C_HP) of the high pressure is determined by the formula: [Math. 1] C_HP = A*TS1-B + 12*(1- C*e^) with : C_HP: setpoint value (C_HP) of the high pressure, TS1: temperature of the refrigerant at the outlet of the first heat exchanger (1), Q: flow rate (Q) of refrigerant discharged by the compressor (7), A: first constant coefficient, B: second constant coefficient, C: correction factor depending on a relative velocity (VI) of the outside air flow (Fe) with respect to the first exchanger (1).

2. A method according to claim 1, wherein the setpoint value (C_HP) of the high pressure depends on: - the temperature (TS1) of the refrigerant at the outlet of the first heat exchanger (1), - the flow rate (Q) of refrigerant discharged by the compressor (7), and - the relative velocity (VI) of the outside air flow (Fe) with respect to the first heat exchanger (1).

3. A method according to claim 1 or 2, wherein the refrigerant is in a supercritical state at the outlet of the first exchanger (1).

4. A method according to any one of the preceding claims, wherein the refrigerant is of the type R744.

5. A method according to any one of the preceding claims, wherein the main loop (A) of the refrigerant circuit (10) includes an internal exchanger (5) configured to permit heat exchange between the high-pressure refrigerant flowing between the first exchanger (1) and the first expansion valve (21) and the low-pressure refrigerant flowing between the second exchanger (2) and an inlet (7A) of the compressor (7).

6. A method according to any one of the preceding claims, wherein the main loop (A) of the refrigerant circuit (10) includes a refrigerant accumulation device (9) disposed downstream of the second exchanger (2) and upstream of the internal exchanger (5).

7. A control method according to any one of the preceding claims, wherein the refrigerant circuit (10) comprises a bypass branch (B) arranged in parallel with the first expansion valve (21) and the second heat exchanger (2), the bypass branch (B) comprising successively a second expansion valve (22) and a third heat exchanger (3) thermally coupled with a second heat transfer fluid (F2), wherein the second heat transfer fluid (F2) is a heat transfer liquid circulating in a heat transfer liquid circuit (40), and in which the third heat exchanger (3) is thermally coupled with an element (25) of an electric drive chain of a motor vehicle (50), via the heat transfer fluid circulating in the heat transfer fluid circuit (40).

8. A control method according to any one of the preceding claims, wherein the first constant coefficient (A) is between 2.3 and 2.7, preferably between 2.4 and 2.6, more preferably between 2.55 and 2.

65.

9. A method for controlling any one of the preceding claims, wherein the second constant coefficient (B) is between 2 and 6, preferably between 3 and 5, more preferably between 3.5 and 4.

5.

10. A control method according to any one of the preceding claims, wherein the correction factor (C) is determined by the formula: C= 1-0.1*-^with: V1: relative velocity of the outside airflow Fe with respect to the first exchanger (1).

11. A control method according to any one of the preceding claims, wherein the thermal conditioning system (100) comprises a motor-fan unit (15) configured to increase a relative velocity of the outside airflow (Fe) with respect to the first exchanger (1), and wherein the relative velocity (VI) of the outside airflow (Fe) with respect to the first exchanger (1) is determined from a forward speed (V) of a vehicle comprising the thermal conditioning system (100) and from a parameter representative of a rotational speed of the motor-fan unit (15).

12. Thermal conditioning system (100) for a motor vehicle, comprising a refrigerant circuit (10) having a main loop (A) comprising successively, according to a direction of refrigerant flow: - a compressor (7) configured to deliver a flow rate (Q) of refrigerant at high pressure, - a first heat exchanger (1) thermally coupled with an outside air flow (Fe), the outside air flow (Fe) having a relative velocity (VI) with respect to the first exchanger (1), - a first expansion valve (21), - a second heat exchanger (2) thermally coupled with a first heat transfer fluid (Fl), characterized in that the thermal conditioning system (100) includes an electronic control unit (60) configured to implement the process according to one of the preceding claims.

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