FR3062715A1 - METHOD OF CONTROLLING THERMAL EXCHANGE - Google Patents

Abstract

A method for controlling a heat exchange between a cooling loop (4) of a motor (2) configured to allow the circulation of a first heat transfer fluid and a Rankine loop (5) called a Rankine loop ( 5) configured to allow the circulation of a refrigerant, via a first heat exchanger (6), characterized in that it comprises: • a control step in which a temperature (M_TFC1) of the first heat transfer fluid is compared to a temperature setpoint; A heat exchange revision step in which the flow rate of said first heat transfer fluid (C_QFC1) passing through said first heat exchanger (6) or at least one control parameter (C_NT, C_NP) of the Rankine loop is adjusted, as a function of the difference (E_TFC1) between said measured temperature (M_TFC1) and said temperature set point, for regulating the temperature of the first heat transfer fluid.

Description

TECHNICAL AREA

The invention relates to a method for controlling a heat exchange between an engine cooling loop and a Rankine thermodynamic cycle loop, via a heat exchanger.

STATE OF THE ART

A vehicle is for example powered by an internal combustion engine, this engine being cooled by a heat transfer fluid and generating exhaust gases discharged from the vehicle via an exhaust line.

To increase the energy efficiency of the engine, the vehicle may include an energy recovery system whose function is to transform the thermal power available at the engine, and more precisely at the heat transfer fluid and / or combustion gases, into mechanical power.

It has thus already been envisaged by the applicant an energy recovery system comprising in particular an engine cooling loop in which a heat transfer fluid circulates and a thermodynamic Rankine cycle loop called Rankine loop in which circulates a refrigerant.

More specifically, the cooling loop comprises an exchanger through which the heat transfer fluid exchanges heat with the refrigerant, the exchanger consisting of an evaporator configured to allow a phase change of the refrigerant.

The Rankine loop notably includes a turbine capable of producing the desired mechanical power under the effect of an expansion of the refrigerant.

It is known to control the Rankine loop, by a control device, so as to maximize the recovery of mechanical power at the level of the turbine.

However, the thermal power available at the heat transfer fluid depends on the driving conditions of the vehicle.

Indeed, when driving in an urban area, the available thermal power is generally low since the engine generates little power. Conversely, when driving on a fast track (or expressway), the available thermal power is important since the engine generates more power.

Traditionally, for the temperature of the heat transfer fluid, engine manufacturers define a temperature interval to be respected, delimited by a minimum temperature setpoint and a maximum temperature setpoint, in which the operation of the engine is optimized.

It has been noted by the applicant that, when the thermal power available at the evaporator level is low (for example when driving in an urban area), the application of the Rankine loop control strategy consisting of maximizing the mechanical power generated generates, beyond a certain time, a drop in the temperature of the heat transfer fluid below the minimum temperature setpoint, to the detriment of the proper functioning of the engine, and more generally of the longevity of the latter .

The object of the present invention is to propose a method for controlling a heat exchange between the engine cooling loop and the Rankine loop which makes it possible to remedy the aforementioned drawback.

STATEMENT OF THE INVENTION

The subject of the invention is therefore a method of controlling a heat exchange between a motor cooling loop configured to allow the circulation of a first heat transfer fluid and a Rankine thermodynamic cycle loop called Rankine loop configured for allow the circulation of a refrigerant, via a first heat exchanger, characterized in that it comprises:

• a control step in which a temperature of the first heat transfer fluid is compared with a temperature setpoint;

A step of revision of the heat exchange in which the flow of said first heat transfer fluid passing through said first heat exchanger or at least one control parameter of the Rankine loop is adjusted, as a function of the difference between said measured temperature and said temperature setpoint, for regulating the temperature of the first heat transfer fluid.

Such a heat exchange control method makes it possible to regulate the temperature of the first heat transfer fluid while optimizing the operation of the Rankine loop, and in other words to maximize the mechanical power recovered while not degrading the performance of the engine in operation.

More precisely, such a method makes it possible in particular to maintain the temperature of the first heat transfer fluid between the minimum temperature setpoint and the maximum temperature setpoint, under the different driving conditions (urban area, expressway, etc.).

The control method according to the invention may include one or more of the following characteristics, taken individually or in combination with one another:

îo - said method comprises a step of measuring the temperature of the heat transfer fluid;

- Said temperature measurement of the heat transfer fluid is carried out downstream of said engine and upstream of the first heat exchanger;

the method comprises a step of optimizing at least one parameter for controlling the Ftankin loop;

- Said step of revision of the heat exchange is carried out by means of adjusting the flow rate of the first heat transfer fluid, in particular of a flow rate instruction of the first heat transfer fluid, controlled by a control device;

- the Ftankine loop includes a pump and a turbine capable of producing mechanical power under the effect of an expansion of the refrigerant,

said control parameter of the Ftankine loop is the speed of rotation of the pump and / or the speed of rotation of the turbine, in particular a speed setting of the pump and / or a speed setting of the turbine;

- the speed of the turbine is determined from a measurement of the pressure upstream of the turbine, according to the direction of circulation of the refrigerant, and a high pressure setpoint determined according to an algorithm for optimizing the operation of the loop of Rankine;

- the speed of the pump is determined from a pressure measurement in

0 downstream of the turbine and a low pressure setpoint determined according to said algorithm;

- during the heat exchange revision step, the pump speed is revised by assigning a correction to said optimized low pressure setpoint, said correction being determined as a function of said temperature difference;

- said Rankine loop dissipates heat via a second heat exchanger of a low temperature loop configured to circulate a second heat transfer fluid, said second exchanger being placed on the front face of a vehicle and traversed by an air flow ,

- said high pressure setpoint and / or said low pressure setpoint are determined according to said algorithm from a measurement of at least one, and preferably all, of the following parameters:

• the speed of the air flow;

• the ambient temperature of the air outside the vehicle;

• the flow rate of the second heat transfer fluid;

• the flow of said first heat transfer fluid intended to exchange heat with the refrigerant;

• the temperature of the first heat transfer fluid, preferably expressed downstream of said engine and upstream of the first heat exchanger;

- said parameters come from measurement.

DESCRIPTION OF THE FIGURES

Other characteristics, details and advantages of the invention will emerge more clearly on reading the description given below by way of indication in relation to the drawings in which:

- Figure 1 is a schematic view of an example of an energy recovery system, comprising in particular a motor cooling loop and a thermodynamic Rankine cycle loop, to which the method according to the invention applies ;

- Figure 2 is a block diagram of a first example of a device for controlling the energy recovery system, allowing the implementation of the method according to the invention;

- Figure 3 is a block diagram of a second example of a device for controlling the energy recovery system, allowing the implementation of the method according to the invention;

- Figure 4 is a block diagram of a third example of a device for controlling the energy recovery system, allowing the implementation of the method according to the invention.

DETAILED DESCRIPTION

Figures 1 illustrates an energy recovery system 1 of a vehicle powered by an engine 2. The engine 2 is for example an internal combustion engine. The energy recovery system 1 is controlled by a control device 3. In FIG. 1, the actuators controlled by the control device 3 are crossed by an arrow in solid line.

The energy recovery system 1 comprises a cooling loop 4 of the engine 2 in which a first heat transfer fluid circulates and a thermodynamic Rankine cycle loop 5 called Rankine loop 5 in which a refrigerant circulates.

The term “thermodynamic Rankine cycle” is intended to mean a thermodynamic cycle in which the refrigerant will successively undergo compression (in particular adiabatic), vaporization (in particular isobaric), expansion (in particular adiabatic) and liquefaction (in particular isobaric).

In the following description, the terms “upstream” and “downstream” are defined as a function of the direction of circulation of the fluid in the corresponding loop 4, 5, 12.

The first heat transfer fluid of the cooling loop 4 of the engine 2

0 in particular allows the calories generated by the operation of the engine to be removed. The temperature of the first heat transfer fluid is a major parameter for allowing the calories to be removed correctly, and in general to obtain proper operation of the engine 2.

Thus, for the temperature of the first heat transfer fluid, in operation, the engine manufacturers define a temperature interval to be respected, delimited by a minimum temperature setpoint and a maximum temperature setpoint, in which the operation of the engine 2 is optimized. The minimum and maximum temperature setpoints are for example expressed at the output of the engine 2, and in other words downstream of the engine 2 according to the direction of circulation of the

0 first heat transfer fluid in the cooling loop 4 of the engine 2. For example, the minimum temperature setpoint is 90 ° C and the maximum temperature setpoint is 110 ° C.

The cooling loop 4 of the engine 2 further comprises, in general, a heat exchanger 6, here an evaporator 6, a first radiator 7 and a first pump 8.

More specifically, the evaporator 6 is configured to carry out a heat exchange between the first heat transfer fluid and the refrigerant of the loop.

Rankine 5, and in other words configured to allow a change of phase of the refrigerant. The first radiator 7 can be placed on the front face of the vehicle, so as to exchange heat with a flow F of air outside the vehicle. The first pump 8 drives the first heat transfer fluid in the cooling loop 4 of the engine 2.

îo The Rankine loop 5 makes it possible in particular to transform part of the excess thermal power available at the level of the first heat transfer fluid into mechanical power.

In addition to the evaporator 6, the Rankine loop 5 includes a turbine 9, a second pump 10 and a condenser 11.

More precisely, the second pump 10 makes it possible to entrain the refrigerant in the Rankine loop 5. The condenser 11 makes it possible to evacuate heat, for example outside the vehicle. The turbine 9 is capable of producing mechanical power under the effect of an expansion of the refrigerant.

In the Rankine loop 5, the refrigerant successively crosses the

0 second pump 10, the evaporator 6, the turbine 9 and the condenser 11 before crossing again the second pump 10. Thus, in the thermodynamic cycle of Rankine, the refrigerant undergoes successive compression in the second pump 10, a vaporization in the evaporator 6, expansion in the turbine 9 and liquefaction in the condenser 11.

The mechanical power generated by the turbine 9 can be transmitted, by a mechanical link, to at least one mechanical receiver requiring the supply of mechanical power to operate and / or be converted into electrical energy, for example by an electrical generator.

The condenser 11 dissipates heat outside the vehicle, by

0 example, via a low temperature loop 12 in which a second heat transfer fluid circulates.

The condenser 11 is thus configured to carry out a heat exchange between the refrigerant and the second heat transfer fluid of the low temperature loop 12. In addition to the condenser 11, the low temperature loop 12 comprises a third pump 13 and a second radiator 14. The second radiator 14 is for example placed on the front face of the vehicle, so as to exchange heat with a flow F of air outside the vehicle.

According to the embodiment illustrated in FIG. 1, the first and second radiators 7, 14 are placed one behind the other so that the flow F of outside air successively passes through the second radiator 14 then the first radiator 7.

In the low temperature loop 12, the second heat transfer fluid Io successively passes through the third pump 13, the condenser 11 then the second radiator 14 before passing again through the third pump 13.

The control device 3 comprises an automated data processing unit 15, such as an industrial programmable controller (microprocessor, memory, clock, input interface, output interface, etc.), configured to implement a control method a heat exchange between the cooling loop 12 of the engine 2 and the Rankine loop 5, via the evaporator 6.

According to the invention, said process comprises the following stages:

• a control step in which a temperature of the first heat transfer fluid is compared with a temperature setpoint (for example

0 minimum temperature setpoint of 90 ° C);

• a step of revision of the heat exchange in which the flow rate of the first heat transfer fluid passing through the evaporator 6 or at least one control parameter of the Rankine loop is adjusted, according to the difference between the measured temperature of the first heat transfer fluid and the temperature setpoint, to regulate the temperature of the first heat transfer fluid.

Such a heat exchange control method makes it possible to regulate the temperature of the first heat transfer fluid while optimizing the operation of the Rankine loop 5, and in other words maximizing the mechanical power recovered while not degrading the performance of the engine 2 in operation .

More precisely, such a method makes it possible in particular to maintain the temperature of the first heat transfer fluid between the minimum temperature setpoint and the maximum temperature setpoint, under the different driving conditions (urban area, expressway, etc.).

The temperature of the first heat transfer fluid preferably comes from a measurement step.

Advantageously, the method according to the invention comprises a step of optimizing the control parameter of the Rankine loop 5, in particular intervening at the same frequency or at a frequency faster than the step of revision of the heat exchange.

In order to control the various actuators (pumps 8, 10, 13, turbine 9, valve 30, etc.) of the energy recovery system 1, the control device 3 (and more precisely the automated data processing unit 15) receives information on the evolution of the different loops 4, 5, 12 via in particular measurement means 16, 17, 18, 19, 20, 21, 22.

More precisely, as illustrated in FIG. 1 by the dotted arrows, the control device 3 receives in real time, via different measurement means 16, 17, 18, 19, 20, 21, 22, information on the following parameters:

• the temperature of the first heat transfer fluid M_Tfci, measured downstream of the engine 2 and upstream of the evaporator 6, by means of temperature measurement means 16 such as a temperature probe.

• the flow of the first heat transfer fluid M_Q _F ci passing through the evaporator 6, measured upstream of the evaporator 6, by means of flow measurement means 17 such as a flow meter.

• the pressure of the refrigerant upstream of the turbine 9 (high pressure) M_HP, measured upstream of the turbine 9 and downstream of the evaporator 6, by means of pressure measurement means such as a pressure gauge.

• the pressure of the refrigerant downstream of the turbine 9 (low pressure) M_BP, measured downstream of the turbine 9 and upstream of the condenser 11, by means of pressure measurement means such as a pressure gauge.

• the speed of the flow of outside air M_V _F , measured by means of speed measurement means 20 such as an anemometer.

• the flow rate of the second heat transfer fluid M_Q _F C2, measured upstream of the second radiator 14 and downstream of the condenser 11, by means of flow measurement means 21 such as a flow meter.

• the ambient temperature of the air outside the vehicle M_Text, measured by means of temperature measurement means 22 such as a temperature probe.

As a variant, the speed of the outside air flow can be estimated from the speed of the vehicle. The flow rate of the first fluid in the evaporator 6 can be estimated on the basis of operating information from the first pump 8, in particular information on the electric current which it consumes, as well as information on the mode of circulation. of the first fluid in the engine cooling loop, in particular the open or closed state of valves making it possible to direct the first fluid into different branches of said engine cooling loop and / or to modify the flow rate thereof through said branches.

Similarly, the flow rate of the second heat transfer fluid can be estimated from operating information from the second pump 10 and from the pressures measured upstream and downstream of the turbine 9.

To optimize the operation of the Rankine loop 5, and in other words to maximize the mechanical power recovered via the turbine 9, the automated unit

0 15 is configured to control (for example by periodic cycles) the

Rankine 5 from the different information received from the measurement means 16, 17, 18, 19, 20, 21, 22 via in particular the unfolding of an algorithm for optimizing operation 23 of the Rankine loop 5 then a law 24 of the Rankine loop 5.

According to the embodiment illustrated in the block diagram of FIG. 2, the automated unit 15 optimizes, by periodic cycles, the operation of the Rankine loop 5 by controlling the speed of rotation C_N _T of the turbine 9 and the speed of rotation C_Np of the second pump 10, from information retranscribed via the different measurement means 16, 17, 18, 19, 20, 21,22.

More precisely, as illustrated in FIG. 2, the operating optimization algorithm 23 of the Rankine loop 5 determines, for each cycle, an optimized pressure setpoint upstream of the turbine 9 called the high pressure setpoint C_HP and an optimized pressure setpoint downstream of the turbine 9 called ίο low pressure setpoint C_BP from the following information (or measurements):

• the speed of the flow F of outside air M_V _F ;

• the ambient temperature of the air outside the vehicle M_T _ext ;

• the flow rate of the second heat transfer fluid M_Q _F C2;

• the temperature of the first heat transfer fluid M_T _F ci;

• the flow rate of the first heat transfer fluid M_Q _FC1 .

As illustrated in FIG. 2, the control law 24 of the Rankine loop 5 determines, for each cycle, an optimized setpoint of rotation speed C_Nt of the turbine 9 and an optimized setpoint of rotational speed C_Np of the second pump 10 from the high pressure C_HP and low pressure C_BP setpoints expressed above.

More specifically, for each cycle, the speed setpoint C_Nt of the turbine 9 is determined from the difference E_HP (symbolized by a comparator 25) between the high pressure setpoint C_HP and the measurement of the refrigerant pressure M_HP upstream of the turbine 9, and a function F1, the variable of which corresponds to the difference E_HP and the image corresponds to the speed setpoint C_Nt of the turbine 9.

Similarly, for each cycle, the rotation speed setpoint C_Np of the second pump 10 is determined from the difference E_BP (symbolized by a comparator 26) between the low pressure setpoint C_BP and the pressure measurement of the refrigerant M_BP downstream of the turbine 9, and a function F2, the variable of which corresponds to the difference E_BP and the image corresponds to the speed reference C_Np of the second pump 10.

Alternatively, the rotation speed setpoint C_N _P of the second pump 10 could be determined from the difference between a refrigerant flow rate setpoint downstream of the turbine 9 and a refrigerant flow rate measurement downstream of the turbine 9.

As illustrated in the block diagram of FIG. 3, according to a first alternative of the invention, for regulating the temperature of the first heat transfer fluid (for example keeping the temperature of the first heat transfer fluid above the minimum temperature setpoint) , an optimized control parameter of the Rankine loop 5 is revised as a function of the difference E_T _FC1 between the temperature setpoint of the first heat transfer fluid C_Tfci (corresponding for example to the minimum temperature setpoint) and the measured temperature of the first fluid coolant M_Tfci- The flow rate of the first coolant through the evaporator 6 is kept constant in this first alternative.

More specifically, a correction Δ_ΒΡ is added (symbolized by an adder 27) to the low pressure setpoint C_BP. The correction Δ_ΒΡ is determined from the difference E_Tfci (symbolized by a comparator 28) between the temperature setpoint of the first heat transfer fluid C_T _F ci and the temperature measurement of the first heat transfer fluid M_Tfci, and a function F3 including the îo variable corresponds to the difference E_Tfci and the image corresponds to the correction Δ_ΒΡ.

According to a first variant, a correction Δ_ΗΡ could be added to the high pressure setpoint C_HP.

According to a second variant, corrections Δ_ΒΡ and Δ_ΗΡ could be added respectively to the low pressure setpoints C_BP and high pressure

C_HP.

As illustrated in the block diagram of FIG. 4, according to a second alternative of the invention, for regulating the temperature of the first heat transfer fluid (for example keeping the temperature of the first heat transfer fluid above the minimum temperature setpoint) , the flow of the first heat transfer fluid

0 passing through the evaporator 6 is revised as a function of the difference E_T _F ci between the temperature set point of the first heat transfer fluid C_Tfci (corresponding for example to the minimum temperature set point) and the measured temperature of the first heat transfer fluid M_Tfci- In parallel , for each cycle, the rotation speed setpoints C_N _P and C_N _T are determined according to the control law

24 of the Rankine loop 5 presented in FIG. 2.

More specifically, means for adjusting the flow rate 29 of the first heat transfer fluid passing through the evaporator 6 controlled by the control device 3 revise the flow rate of the first heat transfer fluid passing through the evaporator 6 according to a setpoint C_Qfci determined from the difference E_Tfci between the setpoint of

0 temperature of the first heat transfer fluid C_T _F ci and the measured temperature of the first heat transfer fluid M_ Tfci, and a function F4 whose variable corresponds to the difference E_T _F ci and the image corresponds to the setpoint C_Qfci According to the recovery system energy 1 shown in FIG. 1, the fluid supply to the evaporator 6 and to the first radiator 7 is respectively controlled by a variable flow valve 30 and a thermostat 31.

More specifically, as illustrated in FIG. 1, the cooling loop 4 of the engine 2 comprises a first branch branch 32 on which the evaporator 6 is mounted, this first branch branch 32 being supplied with the first heat transfer fluid via a valve 30 comprising means 29 for adjusting the flow rate commonly called a variable flow valve 30, controlled by the control device 3.

The cooling loop 4 of the engine 2 further comprises a second branch branch 33 (downstream of the first branch branch 32) on which is mounted is the first radiator 7, this second branch branch 33 being supplied with the first fluid. coolant via a thermostat 31.

The thermostat 31 makes it possible in particular to maintain the temperature of the first heat transfer fluid below the maximum temperature setpoint.

The thermostat 31 is preferably electronic and includes a valve controlled by the temperature measurement means 16 measuring the temperature of the first heat transfer fluid.

According to the energy recovery system 1 represented in FIG. 1, the control device 3 controls the first pump 8 (for example the speed

0 of rotation), the flow of the variable flow valve 30 according to the setpoint C_Qfci, the speed of rotation of the second pump 10 according to the setpoint C_Np, the speed of rotation of the turbine 9 according to the setpoint C_N _T , the third pump 13 (for example the speed of rotation). As a reminder, the actuators controlled by the control device 3 are crossed by an arrow in solid line.

The energy recovery system 1 of FIG. 1 can be controlled by the control device 3 either according to the first alternative shown in FIG. 3 and explained above, that is to say by varying the speed of the second pump 10 according to the setpoint C_N _P and / or the speed of rotation of the turbine 9 according to the setpoint C_Nt, taking into account the possible temperature difference E_TFci

0 either according to the second alternative shown in FIG. 4 and explained above, that is to say, by varying the flow of the first pump 8 and / or of the variable flow valve 30, according to the setpoint C_Qfci, θη taking into account the possible temperature difference E_Tfci3062715

Thus, in this case, the temperature setpoint of the first heat transfer fluid C_T _F ci corresponds to the minimum temperature setpoint predetermined by the engine manufacturers, for example 90 ° C in the above example. The control device 3 thus makes it possible to maximize the mechanical power recovered (via the turbine 9) while maintaining the temperature of the first heat transfer fluid above the predetermined minimum temperature setpoint.

In addition, the thermostat 31 in particular makes it possible to maintain the temperature of the first heat transfer fluid below the predetermined maximum temperature, for example 110 ° C. in the above example.

îo In addition, the control device 3 controls the Rankine loop 5 so as to optimize energy recovery while avoiding large variations in temperature of the first heat transfer fluid, and in other words avoiding intermittent operation of the Rankine loop 5, for the benefit of the life of the actuators.

The engine cooling loop may have different configurations and include actuators, controlled by the control device 3 and acting on the circulation and / or the flow rate of the first heat transfer fluid, different from those exposed in FIG. 1.

The energy recovery system 1 may include an exhaust heat recovery system better known by the English designation "Exhaust Heat Recovery System" or "EH R System". The exhaust heat recovery system takes the thermal power available from the engine exhaust line. The EHR system is not detailed here. It comprises for example a heat exchanger allowing a heat exchange between the first heat transfer fluid and the exhaust gases from the engine 2. The EHR system is preferably mounted in series on the cooling loop 4 of the engine 2.

Claims (10)

1. Method for controlling a heat exchange between a cooling loop (4) of an engine (2) configured to allow the circulation of a 5 first heat transfer fluid and a Rankine thermodynamic cycle loop (5) called Rankine loop (5) configured to allow the circulation of a refrigerant, via a first heat exchanger (6), characterized in that it comprises : • a control step in which a temperature (M_T _F ci) of the first heat transfer fluid is compared with a temperature setpoint; • a step of revision of the heat exchange in which the flow of said first heat transfer fluid (C_Q _F ci) through said first heat exchanger (6) or at least one control parameter (C_Nt, C_N _P ) of the loop is adapted of Rankine, as a function of the difference (E_T _FC1 ) between said 15 measured temperature (M_T _F ci) and said temperature setpoint, for regulating the temperature of the first heat transfer fluid. 2. Method according to claim 1 comprising a step of measuring the temperature of the first heat transfer fluid (M_T _F ci). 3. Control method according to the preceding claim, characterized in that said temperature measurement of the first heat transfer fluid is performed downstream of said engine (2) and upstream of the first heat exchanger (6). 25 4. Method according to any one of the preceding claims, comprising a step of optimizing said control parameter (C_N _T , C_Np) of the Rankine loop (5). 5. Control method according to any one of the claims 3 0 above, characterized in that said step of reviewing the heat exchange (C_Q _F ci) is carried out by means of adjusting the flow rate of the first heat transfer fluid (29) controlled by a control device (3). 6. Control method according to any one of the preceding claims, characterized in that the Rankine loop (5) comprises a pump (10) and a turbine (9) capable of producing mechanical power under the effect of a expansion of the refrigerant, and in that said control parameter of the Rankine loop is the speed of rotation (C_Np) of the pump (10) and / or the speed of rotation (C_N _T ) of the turbine (9). 7. Control method according to claim 6, characterized in that the speed (C_Nt) of the turbine (9) is determined from a measurement of the pressure (M_HP) upstream of the turbine (9), according to the direction of flow of the refrigerant, and a high pressure setpoint (C_HP) determined according to an algorithm for optimizing operation (23) of the Rankine loop (5). 8. Control method according to claim 7, characterized in that the speed of the pump (10) is determined from a pressure measurement (M_BP) downstream of the turbine (9) and a low pressure setpoint (C_HP) determined according to said algorithm (23). 9. Control method according to claim 8, characterized in that, during the heat exchange revision step, the speed (C_N _P ) of the pump (10) is revised by assigning a correction (Δ_ΒΡ) to said optimized low pressure setpoint (C_BP), said correction (Δ_ΒΡ) being determined as a function of said temperature difference (E_Tfci) · 10. Control method according to one of claims 7 to 9, characterized in that said Rankine loop (5) removes heat via a second heat exchanger (14) of a low temperature loop (12) configured for circulating a second heat transfer fluid, said second exchanger (14) being placed on the front face of a vehicle and traversed by a flow (F) of air, and in that said high pressure setpoint (C_HP) and / or said low pressure setpoint (C_BP) are determined according to said algorithm (23) from a measurement of at least one, and preferably all, of the following parameters: • the speed of the air flow (F) (M_Vf); • the ambient temperature of the air outside the vehicle (M_T _ext ); • the flow rate of the second heat transfer fluid (M_Q _F C2); • the flow rate of said first heat transfer fluid (M_Q _F ci) intended to exchange heat with the refrigerant; 5 · the temperature of the heat transfer fluid (M_T _F ci), preferably expressed downstream of said engine (2) and upstream of the first heat exchanger (6). 2/2 M_V _f M_T ext M_Q fc2 M_T _FC1 M_Q fci ^C _ ^T FC1 23 3.15