Utility vehicle with a fuel cell cooling system

Abstract

The invention relates to a utility vehicle (11) comprising a chassis (14), a fuel cell (26) and a fuel cell cooling system (12), wherein the fuel cell cooling system (12) comprises: a coolant circuit (30) connected to the fuel cell (26) for guiding a coolant; a pump (32) for circulating the coolant; a heat exchanger (36) that is thermally connected to the chassis (14); a bypass line (38) that can be switched via a multi-port bypass valve (38) for bypassing the heat exchanger (36); and a control unit for switching the multi-port bypass valve (38).

Description

[0001] Commercial vehicle with fuel cell cooling system

[0002] The present invention relates to a commercial vehicle with a chassis, a fuel cell and a fuel cell cooling system and a method for operating a fuel cell cooling system.

[0003] The present invention is based on known fuel cell cooling systems in commercial vehicles. Fuel cells are increasingly being used in commercial vehicles to convert the chemical energy of the fuel into electrical energy with low emissions and high efficiency. However, this energy conversion also generates heat energy, which must be dissipated to prevent damage to heat-sensitive parts of the fuel cell, such as the electrolyte membrane. Proton exchange membrane fuel cells (PEMFCs) are frequently used in vehicles. The optimal operating temperature for this type of low-temperature fuel cell is approximately 60 °C.

[0004] To dissipate excess heat energy, a coolant flows through the fuel cell and the temperature of the coolant is reduced by a refrigeration machine. The coolant can also be cooled by a radiator, possibly in combination with a fan, for example in the front of the vehicle. However, the cooling capacity of such radiators depends on the ambient temperature. Large radiator surfaces are necessary, especially in commercial vehicles, due to the typical drive power and the resulting heat that needs to be dissipated. In order to dissipate the heat energy even at slow driving speeds or when stationary, powerful fans are also required to ensure the necessary airflow through the radiators. This is due in particular to the smaller temperature differences between the ambient temperature and the fuel cell compared to those between the ambient temperature and the combustion engine.Furthermore, in vehicles with combustion engines, a significant portion of the heat energy is dissipated via the exhaust system, which does not occur in fuel cell vehicles and therefore results in significantly lower cooling performance.

[0005] A disadvantage of the existing solutions is that the operation of a refrigeration unit or the cooling fan itself requires a considerable amount of power, which must also initially be provided by the fuel cell. Such a refrigeration unit or cooling fan therefore reduces the total power available for propulsion of the fuel cell.

[0006] A further disadvantage is that the cooling surfaces required for cooling pose challenges to the vehicle package and also have a negative impact on the drag coefficient.

[0007] Another disadvantage is that there are situations where large amounts of heat energy must be dissipated when the vehicle is stationary. This can occur when charging batteries in an existing battery system while the vehicle is stationary or moving slowly. Any radiator, if present, is usually designed in such a way that airflow is essential. Thus, in these situations, a radiator fan often has to be activated, which not only consumes energy but also generates noise.

[0008] In view of this state of the art, there is a need to provide a fuel cell cooling system for commercial vehicles with higher efficiency.

[0009] The object of the present invention is to at least partially remedy the disadvantages described above in a cost-effective and simple manner. In particular, the object of the present invention is to cool fuel cells in commercial vehicles with greater efficiency in a cost-effective and simple manner.

[0010] The above object is achieved by a commercial vehicle having the features of claim 1 and a method having the features of claim 16. Further features and details of the invention emerge from the subclaims, the description, and the drawings. Features and details described in connection with the commercial vehicle according to the invention naturally also apply in connection with the method according to the invention, and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made to each other.

[0011] According to a first aspect, the invention provides a commercial vehicle having a chassis, a fuel cell, and a fuel cell cooling system, wherein the fuel cell cooling system comprises: a cooling circuit connected to the fuel cell for conducting a cooling medium; a pump for circulating the cooling medium; a heat exchanger in thermal communication with the chassis; a bypass line switchable via a multi-way bypass valve for bypassing the heat exchanger; and a control device for switching the multi-way bypass valve.

[0012] The core concept of a fuel cell cooling system according to the invention is that, in a commercial vehicle with a chassis, a fuel cell, and a fuel cell cooling system, at least parts of the chassis can be used as a heat sink. A heat exchanger, through which the cooling medium flows, is thermally connected to the chassis, enabling the transfer of thermal energy between the cooling medium and the chassis. The chassis of commercial vehicles is generally larger than that of passenger cars. With the size, the heat capacity of the chassis also increases, and thus the ability to both absorb large amounts of excess heat and, thanks to its large surface area, dissipate it to the environment.In commercial vehicles, areas such as the passenger compartment, which often require a different temperature control than the fuel cell, are generally smaller and located further away from the chassis than in passenger cars. The passenger compartment of commercial vehicles is therefore less disruptive to the operation of the fuel cell cooling system than in passenger cars. The chassis of commercial vehicles consists largely of solid metallic and thus thermally conductive elements that are in thermal contact with one another. The surface of chassis components can easily be several meters thick. 2 Furthermore, the chassis of commercial vehicles is fundamentally insensitive to temperature changes, making it well-suited to providing a thermal buffer that can dissipate heat to the environment without the need for any adjustments.

[0013] A cooling system is a system designed to cool a self-heating or externally heated device to an appropriate level. This system generally consists of piping, pumps, and a heat sink. A cooling medium circulating in the cooling system is guided past the heat source, heats up, and releases the absorbed heat to the heat sink. However, the cooling system is not exclusively suitable for cooling; it can also provide heating or temperature stabilization. The cooling system is therefore a general temperature control system.

[0014] A commercial vehicle is a motor vehicle that, by its design and equipment, is intended for the transport of people or goods, or for towing trailers, but is not a passenger car or motorcycle, but rather, for example, a bus, a truck, a tractor unit, or a crane truck. In particular, a commercial vehicle according to the invention can be a tractor unit or a truck.

[0015] The chassis includes in particular a frame, for example a ladder frame.

[0016] The fuel cell is a galvanic cell that converts the chemical reaction energy of a continuously supplied fuel and an oxidizing agent into electrical energy. The term "fuel cell" preferably refers to a hydrogen-oxygen fuel cell. The fuel cell is preferably a low-temperature fuel cell, particularly preferably a proton exchange membrane fuel cell.

[0017] A thermal connection is a connection designed for the transfer of thermal energy. While thermal energy can in principle be transferred by conduction, radiation, and convection, the transfer of thermal energy by radiation is so inefficient without special precautions that it is not suitable for the transfer of thermal energy. The suitability of different materials for heat conduction is described by their thermal conduction coefficient. This is low for gases, liquids, and certain solids, but significantly higher for metals. A connection designed for the transfer of thermal energy must therefore include a thermal bridge made of a material with a high thermal conduction coefficient.

[0018] The heat exchanger is a device used to transfer heat between a source and a working medium. The heat exchanger is suitable for both cooling and heating the fuel cell. The multi-way bypass valve and the switchable bypass line, which bypasses the heat exchanger, make the system switchable and controllable. This prevents heat energy from being introduced into the cooling system when ambient temperatures are too high, and prevents excessive amounts of heat energy from being removed from the system when outside temperatures are too low. It is also possible to regulate the fuel cell to a desired temperature level. This ensures that the fuel cell always operates at its optimal operating temperature. The multi-way bypass valve can also be designed as a proportional valve, with which the flow through the bypass line can be switched into more than two discrete states.In particular, it is also possible to switch the multi-way bypass valve to one of several states with continuous gradation. The term "switching" should therefore be interpreted broadly and also includes "control."

[0019] Further advantages are achieved if the fuel cell cooling system further comprises a refrigeration machine for cooling the cooling medium.

[0020] A refrigeration machine is a machine that extracts heat from a liquid refrigerant through a vapor-compression refrigeration cycle, an adsorption refrigeration cycle, or an absorption refrigeration cycle. It allows the refrigerant to be cooled to a temperature below ambient.

[0021] This enables reliable operation of the fuel cell cooling system even at high ambient temperatures.

[0022] A fuel cell cooling system according to any one of the preceding claims, wherein the chassis comprises a ladder frame and the heat exchanger is in thermal communication with the ladder frame.

[0023] A ladder frame is a type of vehicle frame in automotive construction that accommodates, among other things, the axles, engine, transmission, and body. Several cross braces are inserted between two strong longitudinal members, giving it the shape of a ladder. To improve torsional rigidity, ladder frames can be made from closed profiles and are then also referred to as box frames. However, ladder frames for commercial vehicles are often made from C-profile beams. Their use in commercial vehicles, especially trucks with ladder frames, is particularly advantageous because the solid metal longitudinal beams of the ladder frame, with a wall thickness of several millimeters and a significant surface area, are particularly well suited to conducting and dissipating heat energy and also have a high heat capacity.The large dimensions of truck ladder frames require a large surface area for the ladder frame heat sink, enabling particularly efficient transfer of heat energy to the environment. Especially when charging the battery system, the ladder frame serves as a large-surface heat sink, making controlling the cooling fan less necessary or even unnecessary.

[0024] In this embodiment, it is particularly advantageous if a surface of the lead frame is at least 7.5 m 2 , in particular at least 10 m 2 Particularly preferably, it can also be provided that the surface of the lead frame is at least 15 m 2 amounts.

[0025] The large surface area enables more efficient transfer of heat energy to the environment and thus greater cooling performance.

[0026] Further advantages are achieved if the commercial vehicle also comprises a front cooler which is thermally connected to the cooling circuit and which is designed to release thermal energy from the cooling medium to the ambient air.

[0027] The front cooler is a device designed for exchange with ambient air, preferably with a fan. In this case, the use of a front cooler can further increase the efficiency of the fuel cell cooling system due to its additional cooling capacity during low-energy operation.

[0028] This is especially the case if the front cooler includes a fan.

[0029] Further advantages are achieved when the cooling circuit is in thermal connection with high-voltage components of the commercial vehicle.

[0030] Hydrogen-powered commercial vehicles have high-voltage components that typically operate at around 800 volts and are specially protected. These can include, for example, drive inverters or auxiliary devices such as a power steering pump or an air compressor. In many commercial vehicles, additional superstructures are added to the commercial vehicle that also operate at high voltage and are connected to the commercial vehicle's high-voltage grid via an interface. High-voltage components also generate waste heat during operation. The cooling circuit can also have thermal connections to each of these high-voltage components, which can increase the service life of the high-voltage components and ensure increased reliability of the individual components and the overall system.

[0031] Further advantages are achieved when the cooling circuit is in thermal connection with a component of the vehicle frame.

[0032] In some commercial vehicles, in addition to the chassis, components of the vehicle frame are also capable of absorbing, storing, and releasing thermal energy. In these cases, the cooling circuit can be thermally connected to the vehicle frame, for example, via a second heat exchanger or, if necessary, via the existing heat exchanger. This particular embodiment of the invention can lead to increased cooling performance and a higher thermal capacity of the cooling circuit.

[0033] Further advantages can be achieved if the cooling circuit is thermally connected to a high-voltage battery.

[0034] This embodiment relates to a commercial vehicle that is electrically powered, wherein the electrical energy generated by the fuel cell can be used directly and / or stored in the high-voltage battery. Such a drive is also referred to as a hydrogen hybrid drive. Depending on the battery type, the upper value of the cooling medium inlet temperature is in the range of around 40 °C and is therefore lower than for fuel cells. The cooling system can nevertheless be used for both devices to be cooled if, for example, either a low cooling temperature is used or the high-voltage battery is arranged upstream of the fuel cell in the direction of flow or a refrigeration machine for cooling the cooling medium is provided upstream of the high-voltage battery or a bypass line with a three-way valve is switchably connected to the cooling circuit as a section for cooling the high-voltage battery.A combination of several of these options is of course also possible.

[0035] Further advantages can be achieved if the cooling medium comprises a mixture of deionized water and glycol. Deionized coolant is used to cool the fuel cell because it is hardly electrically conductive and does not cause unwanted current flow. Consequently, the components of the fuel cell cooling system that come into contact with the coolant must be resistant to ionized water. However, the use of deionized water with glycol enables more efficient fuel cell operation.

[0036] Further advantages are achieved if the control device is designed to switch the multi-way bypass valve depending on a temperature of the cooling medium and / or an ambient temperature.

[0037] For this purpose, temperature measuring devices are arranged at one or preferably several points in the cooling circuit and the environment, or at a vehicle part in thermal contact with the environment. Such a circuit enables more precise use of the heat exchanger connected to the chassis, thus further increasing cooling efficiency.

[0038] Further preferably, it can be provided that the control device is designed to switch the multi-way bypass valve depending on an operating mode of the commercial vehicle.

[0039] There are operating states of the commercial vehicle in which heat energy must be dissipated from the fuel cell without the vehicle being in motion. For example, when charging batteries in a battery system or during AC charging via an on-board charger or when the fuel cell system is charging the batteries. In this case, the heat capacity of the chassis can be used as an intermediate storage device via the multi-way bypass valve without the need to operate any existing refrigeration unit or cooler. The cooler is normally designed in such a way that airflow through it is essential. In these situations, the fan and / or refrigeration unit must therefore be activated regularly, which not only consumes energy but also creates noise pollution. These disadvantages can be avoided by switching the multi-way bypass valve depending on the operating mode of the commercial vehicle.

[0040] Further advantages are achieved if the control unit is configured to switch the multi-way bypass valve depending on the commercial vehicle's planned route. A planned route can be transmitted to the control unit via the commercial vehicle's navigation system. Manual route entry is also conceivable. Especially for planned journeys through predictably warmer or colder sections, for example, journeys with significant elevation changes or tunnel journeys, the chassis can be used particularly efficiently as a heat buffer, enabling additional efficiency gains.

[0041] In particular, it can be provided that the fuel cell is a polymer electrolyte fuel cell.

[0042] In a polymer electrolyte fuel cell, chemical energy is converted into electrical energy. Depending on the operating point, the electrical efficiency is approximately 60 percent. The electrolyte is typically a solid polymer membrane, such as one made of nitrate. The operating temperature ranges from 60°C to 120°C, although temperatures between 60°C and 85°C are preferred for continuous operation. The membrane is coated on both sides with a catalytically active electrode, a mixture of carbon and a catalyst, often platinum or a mixture of platinum and ruthenium, platinum and nickel, or platinum and cobalt. H2 molecules dissociate on the anode side and are oxidized to two protons each, releasing two electrons. These protons diffuse through the membrane. On the cathode side, oxygen is reduced by the electrons, which previously performed electrical work in an external circuit.Together with the protons transported through the electrolyte, water is produced. To utilize the electrical work, the anode and cathode are connected to the electrical load.

[0043] Compared to other fuel cells, polymer electrolyte fuel cells are particularly compact, allowing them to be used in commercial vehicles with limited space. Depending on the vehicle type, the space saved by the fuel cell compared to other designs can also be used to install larger hydrogen tanks, thus increasing the range of the commercial vehicle.

[0044] Further advantages are achieved if the commercial vehicle has more than 2 axles.

[0045] According to a third aspect, the invention relates to a method for operating a fuel cell cooling system, comprising the steps: a) providing a commercial vehicle according to one of the preceding claims; b) operating the pump for circulating the cooling medium; c) measuring a temperature of the cooling medium; d) measuring an ambient temperature; e) switching the multi-way bypass valve depending on the measured temperature of the cooling medium and the ambient temperature.

[0046] In the method according to the invention, it is preferably provided that step e) is further carried out as a function of an operating mode of the commercial vehicle.

[0047] Further advantages can be achieved if step e) is also carried out depending on a planned route of the commercial vehicle.

[0048] Further advantages, features, and details of the invention will become apparent from the following description, which describes embodiments of the invention in detail with reference to the drawings. It shows schematically:

[0049] Fig. 1 is a sectional view of a truck with a fuel cell cooling system according to a particular embodiment of the invention; and

[0050] Fig. 2 is a flowchart of a method for operating a fuel cell cooling system.

[0051] The sectional view shown in Figure 1 of a truck 10 with a cutting plane at the level of its fuel cell cooling system 12.

[0052] The chassis 14 of the truck 10, as a special form of commercial vehicle 11, comprises a ladder frame 16 with longitudinal members 18 and cross members 20 as well as a passenger cell 15. The truck 10 has three axles 22 with drive wheels 24 extending over the ladder frame 16. The fuel cell cooling system 12 is designed to cool a fuel cell 26. The cooling circuit 30 connected to the fuel cell 26 carries a cooling medium which is circulated by a pump 32 in a flow direction indicated by the arrow 34. Part of the fuel cell cooling system 12 is a heat exchanger 36 which is in thermal connection with the ladder frame 16. Steel girders with a C-profile are usually used as the longitudinal members 18 in the truck 10. For good heat transfer, the heat exchanger 36 is arranged flat on this C-profile.For even better heat transfer, thermally conductive foils, thermally conductive pads, thermally conductive films or thermally conductive pastes are arranged between the heat exchanger 36 and the longitudinal member 18, thus creating a particularly good thermal coupling.

[0053] The heat exchanger 36 has a flow channel (not shown in detail) through which the cooling medium flows during operation. A meandering shape of the flow channel is provided in some embodiments, but in addition to better heat distribution, this also results in a higher pressure loss and must be compensated for with appropriate pumping power. It is also possible to design the heat exchanger as a line along the longitudinal member 18, whereby the cooling medium flows along the ladder frame 16 in the longitudinal direction of the vehicle and, thanks to the large contact area between the heat exchanger 36 and the longitudinal member 18, enables a large amount of thermal energy to be transferred into the ladder frame 16 with little pressure loss. This embodiment also has the advantage that the heat input is distributed over a large frame length, and less heat conduction within the frame is required to achieve a similar heat capacity.In this embodiment, it is preferably provided that the heat exchanger extends over at least 50%, particularly preferably over at least 75% of the length of the lead frame 16.

[0054] A multi-way bypass valve 38 is arranged upstream of the heat exchanger 36 in the direction of flow. The multi-way bypass valve 38 is configured as a three-way valve to open a bypass line 40, which can be switched to bypass the heat exchanger 36, as an alternative to flow through the heat exchanger 36. In this way, heat dissipation to the lead frame 16 can be switched on or off. The multi-way bypass valve 38 can also be configured as a proportional valve. A proportional valve is a continuous valve that, with the aid of a proportional solenoid, allows not only discrete switching positions but also a continuous transition of the valve opening.

[0055] In the flow direction after the heat exchanger 36 and the bypass line 40, a refrigeration machine 42 is arranged in the cooling circuit 30.

[0056] The multi-way bypass valve 38 is controlled by a control device (not shown in detail). The control device receives measurement data of the temperature of the cooling medium measured at various positions (before the radiator, before the heat exchanger, before the battery / fuel cell). The lead frame temperature is measured in the area of ​​the heat exchanger 36, preferably before and after the heat exchanger. Additionally, the lead frame temperature can be measured at other locations in order to estimate the total amount of energy stored in the lead frame 16.

[0057] A front cooler 44 with a fan 46 is arranged in the cooling circuit at the front of the vehicle. The fan can also be controlled by the control unit.

[0058] Figure 2 shows a flow diagram of a method for operating a fuel cell cooling system 12. The method can be used to cool or heat the fuel cell of a commercial vehicle 11 according to the invention.

[0059] The procedure includes the following steps:

[0060] A first step 101 relates to providing a commercial vehicle 11 according to one of claims 1 to 15.

[0061] A second step 102 relates to operating the pump 32 to circulate the cooling medium.

[0062] A cooling medium is circulated in the cooling circuit 30 by pumps.

[0063] A third step 103 concerns measuring a temperature of the cooling medium.

[0064] The temperature of the cooling medium is measured at different positions, for example, upstream of the front cooler 44, upstream of the heat exchanger 36, downstream of the heat exchanger 36, and / or upstream of the fuel cell 26. A fourth step 104 involves measuring an ambient temperature.

[0065] The ambient temperature can be measured directly using an outside thermometer mounted at a suitable location or indirectly as a frame temperature on the ladder frame 16.

[0066] A fifth step 105 relates to switching the multi-way bypass valve 38 depending on the measured temperature of the cooling medium and the ambient temperature.

[0067] The control device switches the position of the multi-way bypass valve 38 based on the temperatures and the optimal temperature ranges of the fuel cell.

[0068] All components of the fuel cell cooling system, especially the fuel cell 38, typically have a comfort zone from Tunten, soll to Toben, son, which lies within a maximum range Tmin to Tmax. In the comfort zone, limits for hysteresis THyst, lower and THyst, upper must be defined, which lie within the comfort zone.

[0069] Depending on the temperature of the component to be tempered and the direction of heat transfer, the states 'heating', 'cooling' or 'no tempering' are set.

[0070] Within the comfort zone, between the narrower hysteresis limits THyst, lower and THyst, upper, a temperature control with the lowest possible energy consumption is selected. This can preferably be achieved with frame heat exchanger 36, if the measured temperatures allow it, but without operating fan 46 on front cooler 44.

[0071] Only when this type of temperature control is not sufficient are additional cooling components such as the fan 46 or the refrigeration machine 42 activated.

[0072] If the temperature of the ladder frame 16 no longer helps with the temperature control because it is above the value of Toben, son in the 'cooling' state or below the value of Tunten, son in the cooling state, the multi-way bypass valve 38 is switched so that the heat exchanger 36 is not flowed through or only to a reduced extent in order to at least partially decouple the chassis 14 thermally from the rest of the fuel cell cooling system 12.

[0073] The above explanations of the embodiments describe the present invention exclusively by way of examples.

[0074] List of reference symbols

[0075] 10 trucks

[0076] 11 commercial vehicle

[0077] 12 Fuel cell cooling system

[0078] 14 Chassis

[0079] 15 Passenger compartment

[0080] 16 ladder frames

[0081] 18 longitudinal members

[0082] 20 cross members

[0083] 22 Axis

[0084] 24 drive wheels

[0085] 26 fuel cells

[0086] 30 Cooling circuit

[0087] 32 Pump

[0088] 34 Arrow

[0089] 36 heat exchangers

[0090] 38 Multi-way bypass valve

[0091] 40 Bypass line

[0092] 42 Refrigeration machine

[0093] 44 front cooler

[0094] 46 fans

[0095] 101 first step

[0096] 102 second step

[0097] 103 third step

[0098] 104 fourth step

[0099] 105 fifth step

Claims

A commercial vehicle (11) comprising a chassis (14), a fuel cell (26), and a fuel cell cooling system (12), the fuel cell cooling system (12) comprising: a cooling circuit (30) connected to the fuel cell (26) for conveying a cooling medium; a pump (32) for circulating the cooling medium; a heat exchanger (36) in thermal communication with the chassis (14); a bypass line (40) switchable via a multi-way bypass valve (38) for bypassing the heat exchanger (36); and a control device for switching the multi-way bypass valve (38). The commercial vehicle (11) according to claim 1, the fuel cell cooling system (12) further comprising a refrigeration machine (42) for cooling the cooling medium. Commercial vehicle (11) according to one of the preceding claims, wherein the chassis (14) comprises a ladder frame (16) and the heat exchanger (36) is in thermal communication with the ladder frame (16).Commercial vehicle (11) according to claim 3, wherein a surface of the ladder frame (16) is at least 7.5 m. 2 , in particular at least 10 m 2 A commercial vehicle (11) according to any one of the preceding claims, further comprising a front cooler (44) thermally connected to the cooling circuit (30) and configured to release thermal energy from the cooling medium to the ambient air. A commercial vehicle (11) according to claim 5, wherein the front cooler (44) comprises a fan (46). Commercial vehicle (11) according to one of the preceding claims, wherein the cooling circuit (30) is in thermal communication with high-voltage components of the commercial vehicle (11). Commercial vehicle (11) according to one of the preceding claims, wherein the heat exchanger (36) is further in thermal communication with a component of the vehicle frame. Commercial vehicle (11) according to one of the preceding claims, further comprising a high-voltage battery, wherein the cooling circuit (30) is in thermal communication with the high-voltage battery. Commercial vehicle (11) according to one of the preceding claims, wherein the cooling medium comprises a mixture of deionized water and glycol. Commercial vehicle (11) according to one of the preceding claims, wherein the control device is configured to switch the multi-way bypass valve (38) depending on a temperature of the cooling medium and / or an ambient temperature.Commercial vehicle (11) according to one of the preceding claims, wherein the control device is configured to switch the multi-way bypass valve (38) depending on an operating mode of the commercial vehicle (11). Commercial vehicle (11) according to one of the preceding claims, wherein the control device is configured to switch the multi-way bypass valve (38) depending on a planned route of the commercial vehicle (11). Commercial vehicle (11) according to one of the preceding claims, wherein the fuel cell (26) is a polymer electrolyte fuel cell. Commercial vehicle (11) according to one of the preceding claims, wherein the commercial vehicle (11) has more than 2 axles (22). Method for operating a fuel cell cooling system (12), comprising the steps:. a) Providing a commercial vehicle (11) according to one of the preceding claims; b) Operating the pump (32) to circulate the cooling medium; c) Measuring a temperature of the cooling medium; d) Measuring an ambient temperature; e) Switching the multi-way bypass valve (38) depending on the measured temperature of the cooling medium and the ambient temperature. Method according to claim 16, wherein step e) is further carried out depending on an operating mode of the commercial vehicle (11). Method according to claim 16 or 17, wherein step e) is further carried out depending on a planned route of the commercial vehicle (11).

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