A vehicle comprising a driver's cabin and a heat pump for heating the cabin during de-icing.

Abstract

The invention relates to an apparatus (1) intended for outdoor use (1), comprising a control device (90) configured to control routing means and a compressor for circulating a refrigerant between a compressor (4), a condenser (23) and an external heat exchanger (3) of a heat pump in a first operating mode, and for heating the heating element (24) in another operating mode. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: Device comprising a driver's cabin and a heat pump for heating the cabin during defrosting

[0001] The invention relates to the field of climate control of the cockpit of a machine intended for outdoor use, and in particular the climate control of a cockpit of such a machine by means of a heat pump system.

[0002] To cope with the varying climatic conditions outside the passenger compartment of a vehicle, temperature control systems are almost always installed in passenger compartments, particularly in recreational and commercial vehicles. Heating the driver's compartment is sometimes achieved using resistive heaters, powered by the vehicle's electrical system. However, the energy efficiency of resistive systems makes them problematic for newer generations of vehicles or machines using electric motors powered by electrochemical batteries.

[0003] Thus, an increasing number of vehicles use a heat pump to produce either cold or heat, in order to adapt the temperature of the passenger compartment while minimizing energy consumption.

[0004] Such a heat pump system typically comprises an external heat exchanger through which an external airflow passes on one side, and a reversible refrigerant circuit on the other. A compressor drives the refrigerant through the circuit. The heat pump system also comprises an internal heat exchanger through which an airflow destined for the passenger compartment passes, and the refrigerant circuit passes. Depending on the operating mode, the external heat exchanger functions as an evaporator to absorb heat from the external airflow to warm the refrigerant, or as a condenser to release heat to the incoming airflow to cool the refrigerant.

[0005] One of the problems with a vehicle equipped with a heat pump arises from its use in cold and humid conditions, particularly when starting the vehicle and heating the passenger compartment. Since the external heat exchanger acts as an evaporator, it cools already cold external air. The humidity in this air condenses on the external heat exchanger and then forms frost upon contact. The available surface area for heat exchange with the outside air then decreases, reducing the heat extracted from the external air.

[0006] If we plan to interrupt the heating by the heat pump to proceed with defrosting, the passenger compartment may be subjected to rapid cooling which is not acceptable to the user.

[0007] The invention aims to resolve one or more of these drawbacks. The invention thus relates to a device intended for outdoor use, comprising: -a cockpit; -a heat pump comprising: -a heat exchanger configured to be traversed by an airflow from the outside; -an internal heat exchanger configured to be traversed by an airflow destined for the passenger compartment and including an air guide duct having an inlet and an outlet, a condenser and a heating element, the condenser and the heating element being positioned between the inlet and outlet of the guide duct; -a refrigerant fluid circuit passing through the external heat exchanger and the condenser; -a compressor configured to circulate refrigerant in the refrigerant circuit; -refrigerant routing methods; -a control device configured to control the routing means and the compressor to circulate the refrigerant between the compressor, the condenser and the external exchanger in a first mode of operation, and to heat the heating element in another mode of operation.

[0008] The invention also relates to the following variants. Those skilled in the art will understand that each of the features of the following variants can be combined independently with the above features, without thereby constituting an intermediate generalization.

[0009] According to one variant, the control device is further configured to control the routing means and the compressor to circulate the refrigerant between the external exchanger and the compressor by short-circuiting the condenser so as to heat the external exchanger in a third operating mode.

[0010] According to yet another variant, the device comprises an external temperature determination device Tair.i and a refrigerant temperature determination device Tflui.o at the outlet of the external heat exchanger, in which the control device switches from the first operating mode to the third operating mode when the following relationship is verified: Tair.i - Tflui.o > a * Tair.i + b = SMPinch = Cl* with Pinch an allowable temperature difference, a and b constants, Cl, a and [3 constants having been determined beforehand as avoiding frost.

[0011] According to another embodiment, the control device switches from the first operating mode to the third operating mode only if the following additional relationship is satisfied: Tmin < Tair.i < Tmax, where Tmin and Tmax are temperature thresholds for the temperature. external temperature.

[0012] According to yet another variant, Tmin is between -8°C and -3°C.

[0013] According to yet another variant, Tmax is between 9°C and 21°C.

[0014] According to one variant, a is between 0.07 and 0.4 and b is between 5 and 9.

[0015] According to one variant, the internal heat exchanger includes an evaporator, the evaporator, the condenser and the heating element being positioned one after the other between the inlet and outlet of the guide duct; -the refrigerant circuit passing through the external exchanger, the evaporator and the condenser, the evaporator and the condenser being connected in parallel in the refrigerant circuit; -the control device being further configured to control the routing means and the compressor to circulate the refrigerant between the compressor, the external exchanger and the evaporator in a fourth mode of operation.

[0016] According to another variant, the device is a vehicle.

[0017] Other features and advantages of the invention will become clear from the following description, which is by way of example and not limitation, with reference to the accompanying drawings, in which:

[0018] [Fig-1] is a schematic representation of a vehicle equipped with a pump heat for the implementation of the invention;

[0019] [Fig.2] illustrates the implementation of an example of a heating cycle for the vehicle of the [Fig.l];

[0020] [Fig.3] illustrates the implementation of an example of a defrosting cycle for the heat exchanger external for the vehicle of the [Fig.l];

[0021] [Fig.4] illustrates the implementation of an example of an independent heating cycle the heat pump;

[0022] [Fig. 5] illustrates the implementation of an example of an air conditioning cycle for the vehicle of the [Fig.l];

[0023] [Fig.6] schematically illustrates an internal heat exchanger for the vehicle of [Fig.1], according to another aspect of the invention;

[0024] [Fig.7], [Fig.8], [Fig.9] and [Fig.10] are diagrams illustrating examples of selection of parameters for defining a defrosting limit.

[0025] Figure 1 is a schematic representation of an example of a vehicle 1 according to an embodiment of the invention. The vehicle 1 may be a utility vehicle, a construction vehicle, a passenger vehicle, or a recreational vehicle. The invention also applies to other types of vehicles, such as cranes. The vehicle 1 includes a driver's cab 10 in which the temperature must be controlled. The vehicle 1 includes a heat pump 9.

[0026] The heat pump 9 includes a refrigerant circuit 7 passing through The heat pump 9 comprises various components. It includes an internal heat exchanger 2, an external heat exchanger 3, and a compressor 4 configured to circulate refrigerant through the refrigerant circuit 7. The refrigerant circuit 7 passes through the external heat exchanger 3, the internal heat exchanger 2, and the compressor 4. A control unit 90 is configured to control the operating mode of the heat pump. The control unit 90 can be connected to various types of sensors or have a computer to determine environmental or cabin parameters 10. For example, the control unit 90 can be connected to an outdoor temperature sensor, an indoor temperature sensor, an outdoor humidity sensor, or an indoor humidity sensor. The control unit 90 can also receive environmental parameters via internet data streams.Advantageously, compressor 4 is a variable speed compressor to optimize consumption and / or power.

[0027] The internal heat exchanger 2 is designed to carry an airflow to one or more zones of the passenger compartment 10 in order to perform heat exchange with the refrigerant of the circuit 7. The internal heat exchanger 2 includes a fan 21, an evaporator 22, a condenser 23, and a heating element 24. The internal heat exchanger 2 includes an airflow channel passing through the fan 21 to promote airflow towards the passenger compartment, an evaporator 22 for heat exchange for air conditioning the passenger compartment 10, a condenser 23 for heat exchange for heating the passenger compartment 10, and a heating element 24 for heat exchange for heating the passenger compartment 10. The external heat exchanger 3 is designed to carry an airflow from the outside in order to perform heat exchange with the refrigerant. of circuit 7. Fan 21 is advantageously controlled at variable speed.

[0028] The refrigerant circuit 7 shown here includes a connection between the compressor 4 and an accumulator 4L. The circuit 7 includes a connection between an outlet of the compressor 4 and a connector 914. The circuit 7 includes a connection between the connector 914 and a 3-way valve 923. The circuit 7 includes a connection between the 3-way valve and an inlet of the condenser 23. The circuit 7 includes a connection between an outlet of the condenser 23 and a connector 913. The circuit 7 includes a connection between the 3-way valve 923 and the connector 913. The circuit 7 includes a connection between the connector 913 and a connector 912. A first branch includes a 2-way valve 922 and runs from this connector 912 to a connector 911. A second branch includes an expansion valve 52 and runs from the connector 912 to the connector 911. The circuit 7 includes a connection between the connector 911 and a 915 connector. Circuit 7 also includes a connection between connector 914 and connector 915, via a 2-way valve 924. Circuit 7 includes a connection between connector 915 and external exchanger 3. Circuit 7 includes a connection between exchanger 3 and a 3-way valve 921.

[0029] Circuit 7 includes a connection between the 3-way valve 921 and an expansion valve 51. The expansion valve 51 is positioned at the inlet of the evaporator 22. Circuit 7 includes a connection between the outlet of the evaporator 22 and a connector 910. Circuit 7 includes a connection between the connector 910 and the 3-way valve 921. Circuit 7 includes a connection between the connector 910 and the accumulator 4L. Circuit 7 also includes a connection between the accumulator 41 and the compressor 4.

[0030] The compressor 4 and the valves 921, 922, 923 and 924 are controlled by the control device 90. The valves 921, 922, 923 and 924 thus form means of routing the refrigerant, according to different operations detailed later.

[0031] A fan 31 forces air from outside the vehicle 1 through the external heat exchanger 3. The air passing through the external heat exchanger 3 can be directed to the outside. The fan 31 is advantageously controlled at variable speed, for example by pulse-width modulation. Such variable speed makes it possible to optimize the power or consumption of the heat pump 9.

[0032] A first mode of operation is illustrated by reference to [Fig. 2]. In this first mode of operation, the control device 90 is configured to control the routing means and the compressor 4 to circulate the refrigerant between the compressor 4, the condenser 23, and the external heat exchanger 3. In the illustrated example, the control device 90 controls: -closing valve 924, -opening of valve 922, -the closing of the connection between valve 923 and connector 913 and the opening of the connection between connector 914 and condenser 23 by valve 923; -closing the connection between valve 921 and regulator 51 and opening the connection between connector 910 and exchanger 3 by valve 921.

[0033] The refrigerant in circuit 7 follows the following cycle: from compressor 4 to connector 914, from connector 914 to the inlet of condenser 23, from the outlet of condenser 23 to valve 922, from valve 922 to external heat exchanger 3, from external heat exchanger 3 to valve 921, and then from valve 921 back to the inlet of compressor 4. This flow circuit 7 thus bypasses the evaporator 22. Heat is supplied by the refrigerant to the air intended for the passenger compartment 10 in the condenser 23. Heat is absorbed by the refrigerant from the outside air in the external heat exchanger 3.

[0034] The first mode of operation can, for example, be implemented when the The outside temperature is above -7 C. For temperatures above this threshold, the first operating mode can be considered to allow significant energy consumption gains to obtain the same temperature value in the passenger compartment 10.

[0035] In cold and humid conditions, the first operating mode can present problems. Indeed, the cooling of the outside air at the external heat exchanger 3 can lead to condensation and frost on this external heat exchanger 3. The heat exchange between the refrigerant and the outside air can then rapidly deteriorate, potentially causing a significant drop in the energy efficiency of the heat pump 9.

[0036] A second operating mode is illustrated by reference to [Fig. 3]. In this second operating mode, the heat pump 9 is controlled to preheat the heat exchanger 3 to prevent frost formation during the heating of the passenger compartment 10. In the second operating mode, the control device 90 is configured to control the routing means and the compressor 4 to circulate the refrigerant between the compressor 4 and the external heat exchanger 3, bypassing the condenser 23. By bypassing the condenser 23, the refrigerant is prevented from being cooled before reaching the heat exchanger 3, thus enabling optimal heating of the heat exchanger 3. In the illustrated example, the control device 90 controls: -opening of valve 924, -closing valve 922, -closing the connection between valve 923 and connector 913 and closing the connection between connector 914 and condenser 23 by valve 923; -closing the connection between valve 921 and regulator 51 and opening the connection between connector 910 and exchanger 3 by valve 921.

[0037] The refrigerant in circuit 7 follows the following cycle: from compressor 4 to connector 914, from connector 914 to heat exchanger 3, from heat exchanger 3 to valve 921, and from valve 921 to the inlet of compressor 4 via connector 910. This flow circuit 7 thus bypasses the condenser 23. Heat is supplied by the refrigerant to the external heat exchanger 3. The fan 31 is advantageously stopped during an initial phase of the defrosting mode. The second operating mode can be maintained for a period of, for example, 2 to 3 minutes. After determining that the defrosting conditions have been met, the fan 31 is restarted to evacuate any remaining droplets at the end of the defrosting process. The system can then switch back to the first operating mode.

[0038] It can be anticipated that the control device 90 regularly switches between the first and second modes of operation or according to other rules, in order to proceed with the defrosting of the exchanger 3 before resuming a mode of heating the passenger compartment by the condenser 23.

[0039] A third operating mode is illustrated by reference to [Fig. 4]. In this third operating mode, the passenger compartment is heated using resistor 24. Resistor 24 is, for example, of the positive temperature coefficient type. In this third operating mode, an electric current flows through resistor 24. The airflow passing through this resistor 24 is heated, which in turn heats the passenger compartment 10. Resistor 24 can, for example, be powered by the vehicle's electrical system. This heating can thus be independent of the use of condenser 23. Therefore, this heating by resistor 24 can be used in addition to heating by condenser 23 (to increase the heating speed) or as a replacement for heating by condenser 23. The third operating mode can, for example, be adopted when the outside temperature falls below -7°C.The heating via resistance 24 can also be activated simultaneously with the second operating mode, to ensure heating of the passenger compartment 10 even during a defrosting cycle of the heat exchanger 3. The occupants of the passenger compartment 10 will therefore not experience a loss of comfort due to the implementation of a defrosting cycle.

[0040] The control of the first and third operating modes by the control device 90 constitutes an independent aspect of the invention.

[0041] A fourth operating mode is illustrated by reference to [Fig. 5]. In this fourth operating mode, the heat pump 9 is controlled to provide air conditioning for the passenger compartment 10 of the vehicle 1. In this fourth operating mode, the control device 90 is configured to control the routing means and the compressor 4 to circulate the refrigerant between the compressor 4, the condenser 23, and the external heat exchanger 3. In the illustrated example, the control device 90 controls: -closing valve 924, -closing valve 922, -opening the connection between valve 923 and connector 913 and closing the connection between connector 914 and condenser 23 by valve 923; -opening the connection between valve 921 and regulator 51 and closing the connection between connector 910 and exchanger 3 by valve 921.

[0042] The refrigerant in circuit 7 follows the following cycle: from compressor 4 to connector 914, from connector 914 to valve 923, from valve 923 to connector 913, from connector 913 to connector 911 via expansion valve 52, from connector 911 to external heat exchanger 3, from external heat exchanger 3 to valve 921, from valve 921 to expansion valve 51, from expansion valve 51 to the inlet of evaporator 22, and then from the outlet of evaporator 22 to the inlet of compressor 4. This flow circuit 7 thus bypasses the condenser 23. Heat is absorbed by the refrigerant from the air destined for the passenger compartment 10 in the evaporator 22, thus providing cooling. Heat is released by the refrigerant to outside air in the external heat exchanger 3.

[0043] Figure 6 schematically illustrates an internal heat exchanger 2 for the application implementing another aspect of the invention. The internal heat exchanger 2 includes a duct 25 for the passage of air to the passenger compartment. The duct 25 has an air inlet, supplied, for example, either by outside air or by air already present in the passenger compartment 10. The duct 25 has an air outlet opening into the passenger compartment 10 in a manner known per se. The evaporator 22, the condenser 23, and the heating element 24 are positioned one after the other between the inlet and outlet of the guide duct 25. The fan 21 is also positioned between the inlet and outlet of the guide duct 25 to promote airflow through the duct 25. Thus, the heat pump 9 can implement different types of heat exchange with the passenger compartment 10 according to different operating modes from the same duct 25.Thus, the heat pump 9 can either air-condition the passenger compartment 10 by means of the evaporator 22, or heat the passenger compartment 10 by means of the condenser 23, or heat the passenger compartment 10 by means of the heating element 24. Thus, at low temperatures, the control device 90 can command heating of the passenger compartment 10 via the heating element 24 rather than via the condenser 23, in order to maintain better thermal efficiency or avoid having to perform an excessive number of defrosting cycles or to be able to ensure heating of the passenger compartment 10 at very low temperatures.

[0044] According to another variant, it is also possible to consider dehumidifying the passenger compartment 10. In this mode of operation, the control device 90 operates the external exchanger 3 as a condenser and uses both the evaporator 22 and the condenser 23.

[0045] For this purpose, the refrigerant from the compressor 4 passes through the valve 923 to the inlet of the condenser 23, passes through the condenser 23, passes through the open valve 922, passes through the external heat exchanger 3, passes through the valve 921 to the expansion valve 51 then the inlet of the evaporator 22, passes through the evaporator to its outlet, then returns to the compressor 4.

[0046] Thus, the refrigerant transfers thermal energy to the air at the exchanger 3, cools the air in the evaporator 22 to ensure condensation of the humidity present in the air of the passenger compartment, the air being further heated by the condenser 23.

[0047] The refrigerant in circuit 7 is known per se. The refrigerant can be R1234yf, R290, R744, or R134a. The compressor 4 will be defined in the operating parameters of the vehicle's air handling system 1.

[0048] According to an independent aspect of the invention, the efficiency of the heat pump 9 can be optimized in the cabin heating mode 1. For this purpose, a control mode of the control device 90 is provided to allow switching between the first and second operating modes.

[0049] In order to optimize the energy performance coefficient of a heat pump, it is recommended to follow this rule:

[0050] Tair.i - Tflui.o = Pinch <SMpinch

[0051] With Tair.i the temperature of the air entering at the external exchanger 3, Tflui.o the temperature of the refrigerant leaving the external exchanger 3, Pinch the pinch value of the heat pump 9 and SMPinch a limit value guaranteeing the performance of the heat pump 9.

[0052] The SMPinch value can be reduced by optimizing heat exchange at the external heat exchanger 3, in particular by limiting frost and the associated heat exchange surface losses. The SMPinch value is generally between 3 and 10 K in the absence of frost on the external heat exchanger. The SMPinch value can be adjusted according to the operating conditions.

[0053] According to the invention, the criterion implemented to control the switch from the first operating mode to the second operating mode will be when the following condition is met:

[0054] Tair.i - Tflui.o > a * Tair.i + b =SMPinch with a and b constants defined such that a * Tair.i + b = SMPinch

[0055] Advantageously, this switching command will only be implemented when the condition is met for more than a predetermined duration, for example, more than 10 seconds, advantageously more than 15 seconds, and preferably more than 20 seconds. Advantageously, this switching command will only be implemented when Tair.i is between a lower threshold value and an upper threshold value. The lower threshold value is, for example, between -7 and -5°C. The upper threshold value is, for example, between 10 and 20°C.

[0056] In a first example illustrated in [Fig. 7], SMPinch = a * Tair.i + b between the lower threshold value and the upper threshold value (respectively -7°C and 20°C). SMPinch is not limited for low temperatures. SMPinch is large enough to be evaluated correctly and avoids triggering unnecessary defrost cycles. The variation of SMPinch as a function of Tair.i is relatively small. In this example, a = 0.07 and b = 6.52.

[0057] In a second example illustrated in [Fig. 8], SMPinch = a * Tair.i + b between the The lower and upper threshold values ​​are -3°C and 10°C, respectively. SMPinch is limited for low temperatures between -7°C and -3°C, and for high temperatures between 10°C and 20°C. SMPinch remains constant at these lower temperatures, with a value high enough to prevent unnecessary defrosting. SMPinch is also constant at these higher temperatures because a higher value would significantly reduce the heat pump's efficiency without providing any benefit. The variation of SMPinch as a function of Tair.i is high. In this example, a = 0.38 and b = 6.15.

[0058] In a third example illustrated in [Fig. 9], SMPinch = a * Tair.i + b between the lower threshold value and the upper threshold value (respectively -7°C and 10°C). SMPinch is not limited at low temperatures, and limited at high temperatures between 10 and 20°C. SMPinch is sufficiently large at low temperatures to be evaluated correctly and avoids triggering unnecessary defrost cycles. SMPinch is constant at these high temperatures because a higher value would significantly reduce the efficiency of the heat pump without any benefit. The variation of SMPinch as a function of Tair.i is relatively high. In this example, a = 0.18 and b = 8.24.

[0059] In a fourth example illustrated in [Fig. 10], SMPinch = a * Tair.i + b between the lower threshold value and the upper threshold value (respectively -3°C and 20°C). SMPinch is capped for low temperatures between -7 and -3°C, and is not capped for high temperatures up to 20°C. SMPinch is kept constant at low temperatures to ensure proper evaluation and avoid triggering unnecessary defrost cycles. SMPinch increases at these high temperatures because the SMPinch value guarantees a good level of performance without the risk of frost. The variation of SMPinch as a function of Tair.i is relatively small. In this example, a = 0.13 and b = 5.39.

[0060] Several methods can be used to obtain the values ​​a and b. A first method consists of finding the values ​​a and b starting from the following relationship:

[0061] SMPinch = a * Tair.i + b = Cl* (a * Tair.i + |3)

[0062] Cl is a margin coefficient. The values ​​of Cl, a, and [3] are typically determined during a calculation of the nominal value of Pinch and by testing. The value of Cl is notably dependent on the geometry of the heat exchange surface of the external heat exchanger 3 or on the humidity level in the environment. The value of Cl is typically between 1 and 5. The value of Cl can be adjusted according to the location of the equipment, which may result in it being in a more or less humid environment.

[0063] Simulations can be performed in which frost growth over time is calculated. This allows the Cl value to be optimized: High Cl value: we prefer to run the heat pump for a long time, but we accept having to defrost for a long time too (more ice has formed). Preferable in dry environments. A low Cl value means defrosting is activated quickly, as soon as frost has formed. This option is suitable if the heat exchanger frosts easily, because the air is very humid and therefore frost will form rapidly.

[0064] Since frost formation is dependent on air humidity, this parameter can be taken into account when setting the SMPinch value. SMPinch values ​​can, for example, be recorded in the presence of dry air. For low relative humidity values ​​(for example, below 20 or 30%), frost formation at low temperatures is considered impossible. Consequently, triggering a defrost cycle in this situation is not particularly beneficial. In very humid environments, the SMPinch values ​​will be lowered to facilitate the initiation of defrosting operations.

[0065] Simulations can be performed to determine the values ​​of a and [3] that do not result in frost formation, for an optimized SMPinch value. A simulation can then be performed to determine the value of Cl that allows for nominal or acceptable frost formation with a realistic Pinch value. The determination of the values ​​of Cl, a, and [3] can also be carried out based on experimental measurements of frost formation on the external heat exchanger 3.

Claims

Demands

1. Device (1) intended for outdoor use (1), characterized in that it comprises: - a pilot's cabin (10); - a heat pump (9) comprising: - a heat exchanger (3) configured to be traversed by an airflow from the outside; - an internal heat exchanger (2) configured to be traversed by an airflow destined for the cabin (10) and including an air guide duct (25) having an inlet and an outlet, a condenser (23) and a heating element (24), the condenser (23) and the heating element (24) being positioned between the inlet and outlet of the guide duct (25); - a refrigerant circuit (7) passing through the external heat exchanger (3) and the condenser (23); - a compressor (4) configured to circulate refrigerant in the refrigerant circuit (7); -refrigerant routing methods;-a control device (90) configured to control the routing means and the compressor to circulate the refrigerant between the compressor (4), the condenser (23) and the external heat exchanger (3) in a first operating mode, and to heat the heating element (24) in another operating mode.;

2. Device according to claim 1, wherein the control device (90) is further configured to control the routing means and the compressor to circulate the refrigerant between the external exchanger (3) and the compressor (4) by short-circuiting the condenser (23) so as to heat the external exchanger (3) in a third mode of operation.

3. A device (1) according to claim 2, comprising a device for determining the external temperature Tair.i and a device for determining the temperature of the refrigerant Tflui.o at the outlet of the external heat exchanger (3), wherein the control device (90) switches from the first operating mode to the third operating mode when the following relationship is satisfied: Tair.i - Tflui.o > a * Tair.i + b = SMPinch = Cl* (a * Tair.i + |3) with Pinch an permissible temperature difference, a and b the constants, Cl, a and [3 of the constants having been determined beforehand as avoiding frost.

4. Device (1) according to claim 3, wherein the control device (90) switches from the first operating mode to the third operating mode only if the following additional relationship is satisfied: Tmin< Tair.i < Tmax with Tmin and Tmax temperature thresholds for the external temperature.

5. Device (1) according to claim 4, in which Tmin is between -8°C and -3°C.

6. Device of claim 3 or 4, wherein Tmax is between 9°C and 21°C.

7. Device according to any one of the preceding claims, wherein a is between 0.07 and 0.4 and b is between 5 and 9.

8. A device according to any one of the preceding claims, wherein the internal heat exchanger (2) includes an evaporator (22), the evaporator (22), the condenser (23) and the heating element (24) being positioned one after the other between the inlet and outlet of the guide duct; - the refrigerant circuit (7) passing through the external heat exchanger (3), the evaporator (22) and the condenser (23), the evaporator (22) and the condenser (23) being connected in parallel in the refrigerant circuit (7); - the control device (90) being further configured to control the routing means and the compressor (4) to circulate the refrigerant between the compressor (4), the external heat exchanger (3) and the evaporator (22) in a fourth mode of operation.

9. Device according to any one of the preceding claims, wherein the device is a vehicle.

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