SE541792C2

SE541792C2 - A cooling system for a combustion engine and a further object

Info

Publication number: SE541792C2
Application number: SE1650676A
Authority: SE
Inventors: Mats Ekman; Ola Hall; Zoltan Kardos
Original assignee: Scania Cv Ab
Priority date: 2016-05-19
Filing date: 2016-05-19
Publication date: 2019-12-17
Also published as: SE1650676A1; DE102017004588B4; DE102017004588A1

Abstract

The present invention relates a cooling system configured to cool a combustion engine (2) and at least one further object (13) in a vehicle (1). The cooling system comprises a main radiator (8), a main radiator bypass line (9) directing coolant past the main radiator (8), a first valve device (6) receiving coolant from the combustion engine (2) and directing it to the main radiator (8) and the main radiator bypass line (9), an auxiliary circuit (14) directing coolant to the further object (13), and a second valve device (20) receiving coolant from the main radiator (8) and/or the main radiator bypass line (9) and directing it to the auxiliary circuit (14) and/or the combustion engine (2). The auxiliary circuit (14) comprises an auxiliary radiator (15) in which the coolant is cooled to a lower temperature than in the main radiator (8), a condenser (23) in an AC system and an auxiliary coolant pump (24) able to circulate coolant between the auxiliary radiator (15) and the condenser (23) in the auxiliary circuit (14) during operating conditions when the combustion engine (2) is not in operation.

Description

A cooling system for a combustion engine and a further object BACKGROUND OF HE INVENTT1ION AND PRIOR ART The present invention relates to a cooling system for a combustion engine and a further object according to the preamble of claim 1.

A cooling system in a heavy vehicle is many times used to cool a combustion engine and at least one further object demanding a lower operating temperature than the combustion engine. The further object may be the working medium of a WHR system cooled in a condenser, charge air cooled in a charge air cooler, power electronics of a hybrid vehicle etc. In this case, it is necessary to create at least two different coolant temperature levels in the cooling system. Such a cooling system can be equipped with a main radiator and an auxiliary radiator cooling the coolant to a lower temperature than the main radiator. The coolant of the higher temperature is directed to the combustion engine and the coolant of the lower temperature is directed to the further object. During certain operating conditions such as, for example, when the cooling demand of the further object or the combustion engine varies rapidly, it is difficult to direct coolant at required temperature and flow rate to the combustion engine as well as to the further object in order to maintain their efficient operating temperatures. In this case, it is, for example, a risk that coolant of a too low temperature is directed to the combustion engine.

It is often desired to use an AC system in a vehicle even at times when the combustion engine is not in operation. A known practice in this respect is to run the compressor on electrical energy. In order to provide an efficient operation of the AC system, the refrigerant has to be cold in the condenser. During operation of the vehicle, the refrigerant in the AC system is usually cooled by the cooling system cooling the combustion engine. Generally, the circulation of the coolant in the cooling system is provided by a coolant pump driven by the combustion engine. Thus, the cooling system has to have a specific design in order to provide an efficient cooling of the AC system when the combustion engine is not in operation.

US 8,132,547 shows a thermal energy management system for a vehicle. The system comprises a low temperature circuit and a high temperature circuit which a connectable to each other. The low temperature circuit comprises a radiator, an AC-condenser and a charge air cooler and an electrically driven pump.

SUMMARY OF THE INVENTION The object of the present invention is to provide a cooling system cooling a combustion engine and a further object to a lower temperature than the combustion engine where the cooling system has a design making it possible to use an AC system in the vehicle even at times when the combustion engine is not in operation.

The above mentioned object is achieved by the cooling system according to the characterized part of claim 1. The auxiliary circuit comprises an auxiliary coolant pump able to circulate coolant between the auxiliary radiator and the condenser in the auxiliary circuit during operating conditions when the combustion engine is not in operation. The auxiliary pump may be electrically driven by electric energy from a battery in the vehicle. Preferably, the auxiliary circuit comprises an auxiliary radiator fan forcing a cooling air stream through the auxiliary radiator. The auxiliary radiator fan may also be electrically driven by electric energy from a battery in the vehicle. Such a design makes it possible to use the AC system even at times when the combustion engine is not in operation.

According to the invention, the auxiliary circuit comprises a return line directing coolant from a position downstream of the auxiliary radiator and the condenser in the auxiliary circuit to a position upstream of the auxiliary radiator and the condenser in the auxiliary circuit. Such a return line makes it possible to circulate the coolant in a closed loop in the auxiliary circuit. The circulation of the coolant through such a closed loop may be performed by a significantly smaller auxiliary pump than the ordinary coolant pump in the cooling system. Thus, the auxiliary pump requires a relatively small energy supply from the battery.

According to the invention, the return line comprises the auxiliary pump and a one way valve. In this position, the auxiliary pump does not disturb the ordinary coolant flow through the auxiliary circuit. The one way valve allows a coolant flow in the return line in the direction defined by the auxiliary pump and it prevents a coolant flow through the return line in the opposite direction provided by the ordinary pump in the cooling system when the combustion engine is in operation.

According to an embodiment of the invention, the condenser is arranged in series with the further object in the auxiliary circuit. Preferably, the condenser is arranged upstream of the further object. In this case, an inlet of the return line may be located between the condenser and the further object. As a consequence, the coolant flow provided by the auxiliary pump does not need to flow through the further object.

According to an embodiment of the invention, the condenser and the further object is arranged in parallel lines in the auxiliary circuit. In this case, coolant of the same low temperature may be directed to the further object as well as the condenser when the ordinary pump circulates coolant through the auxiliary circuit. The parallel line comprising the further object may comprise a one way valve. In this case, it is possible to prevent a coolant flow through the further object when the auxiliary pump circulates coolant through the auxiliary circuit when the combustion engine is not in operation.

According to an embodiment of the invention, the cooling system comprises a manually activated member configured to initiate activation of the auxiliary pump. Such a member may be a button or the like which may be arranged in a driver cab of the vehicle. The valve devices may be configured to be set in positions such they restricts the coolant flow provided by the auxiliary pump to the auxiliary circuit when the auxiliary pump has been activated. Thus, the valve members prevents a coolant flow to remaining parts of the cooling system than the auxiliary circuit.

According to an embodiment of the invention, the first valve device is a three way valve. The three way valve may comprises one inlet opening and two outlet openings. The three way valve receives, via the inlet opening, a coolant flow from a line of the cooling system and directs a first part of it, via a first outlet opening, to the radiator line and a second part of it, via the second outlet opening, to the radiator bypass line. In this case, the first valve device is designed as a single valve. Preferably, the first valve device is adjustable in a stepless manner. In this case, it is possible to vary the coolant flow rate to the radiator line and the radiator bypass line with a high accuracy. Alternatively, the first valve device is designed as two two way valves wherein a first two way valve is arranged in the radiator inlet line and a second two way valve is arranged in the radiator bypass line.

According to an embodiment of the invention, the second valve device is a three way valve. The three way valve receives a coolant flow from the radiator bypass line and directs a part of it to the auxiliary circuit and a remaining part of it to the engine inlet line. It may also direct coolant from the main radiator to the engine inlet line. In this case, the second valve device is designed as a single valve. Preferably, the second valve device is adjustable in a stepless manner. In this case, it is possible to adjust the coolant flow rate to the auxiliary circuit and the engine inlet line with a high accuracy. Alternatively, the second valve device is designed as two two way valves wherein a first two way valve is arranged in a main radiator outlet line and a second two way valve is arranged in the engine inlet line.

According to an embodiment of the invention, the first valve device and/or the second valve device are designed to conduct small coolant flow rates with a higher accuracy than larger coolant flow rates. During operating conditions when the coolant has a relatively low temperature, the first valve device directs a small coolant flow rate to the main radiator. This small coolant flow rate may be mixed with a small warm coolant flow rate from the radiator bypass line by the second valve device before the mixture is directed to the further object. In order to obtain a required coolant temperature of the mixture with a high accuracy, it is suitable to use a first valve device and a second valve device with the above mentioned design. The first valve devices may comprise a valve member movably arranged within a movement range having an extent between a first end position in which it directs no coolant flow to the main radiator and a second end position in which it directs the entire coolant flow to the main radiator. The movement range for the valve member at which it directs small coolant flows to the radiator line is greater than the movement range for the valve member at which it directs larger coolant flows to the radiator. The second valve device may have a corresponding design as the first valve device.

According to an embodiment of the invention, that the bypass valve is a two way valve arranged in the auxiliary radiator bypass line. The flow resistance through the auxiliary radiator bypass line is considerably lower than the flow resistance through the auxiliary radiator. Thus, when the two way valve is open, the main part of the coolant will be directed through the auxiliary radiator bypass line and a smaller part of the coolant through the auxiliary radiator. The bypass valve may a stop-flow valve (e.g. solenoid valve) or a throttle valve by which it is possible to regulate the coolant flow rate through the auxiliary radiator bypass line. Alternatively, the bypass valve may be a three way valve arranged at a branched portion between a line directing coolant to the auxiliary radiator and the auxiliary radiator bypass line.

According to an embodiment of the invention, the further object is a working medium cooled in a condenser in a WHR-system. In order to achieve a high thermal efficiency in a WHR-system, the working medium in the condenser is to be cooled to a condensation temperature as low as possible and substantially without subcooling. Consequently, in order to achieve a high thermal efficiency in a WHR-system, the working medium is to be cooled with a suitable cooling effect. However, the suitable cooling effect of the working medium in the condenser varies during different operating conditions such as with the heat effect supplied from, for example, the exhaust gases to the evaporator. Since the supplied heat from exhaust gases can vary rapidly, it is difficult to continuously provide a cooling effect of the working medium in the condenser resulting in a high thermal efficiency of a WHR-system. According to the invention, the first valve device, the second valve device and the bypass valve are controlled in a manner such that working medium is condensed in the condenser at a desired condensation temperature. Alternatively, the further object is charge air cooled in a charge air cooler or another object demanding cooling to a lower temperature than the combustion engine.

According to an embodiment of the invention, the auxiliary radiator is arranged in a position in the vehicle in which it is cooled by an air stream of a lower temperature than the temperature of the air stream through the main radiator. The main radiator is usually arranged behind a charge air cooler or another cooler at a front portion of a vehicle. Thus, the air stream through the main radiator usually has a higher temperature than the surrounding air temperature. The auxiliary may be provided below, above or at one side of the main radiator where it is cooled by an air stream of surrounding air temperature.

According to an embodiment of the invention, the air stream through the auxiliary radiator is generated by a separate radiator fan. Such an auxiliary radiator fan may be independently controlled in relation to a main radiator fan forcing air through the main radiator. The auxiliary radiator fan may be driven by an electric motor. In this case, it is possible to control the cooling effect of the coolant in the auxiliary radiator in order to cool the further object to an efficient operating temperature. In order to reduce the consumption of electric energy, the auxiliary radiator is arranged in a position of the vehicle where it receives a cooling air stream by the ram air and the auxiliary radiator fan.

BRIEF DESCRIPTION OF THE DRAWINGS In the following preferred embodiments of the invention are described, as examples, with reference to the attached drawings, in which: Fig. 1 shows a cooling system according to a first embodiment of the invention, and Fig. 2 shows a cooling system according to a second embodiment of the invention and Fig. 3 shows a front view of the main radiator and the auxiliary radiator.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION Fig. 1 shows a schematically disclosed vehicle 1 powered by a combustion engine 2. The vehicle 1 may be a heavy vehicle and the combustion engine 2 may be a diesel engine. The vehicle 1 comprises a cooling system comprising an engine inlet line 3 provided with a pump 4 circulating a coolant in the cooling system. The coolant is initially circulated through the combustion engine 2. The coolant leaving the combustion engine 2 is received in an engine outlet line 5. A first valve device in the form of a first three way valve 6 is arranged at an end of the engine outlet line 5. The first three way valve 6 has one inlet opening and two outlet openings. The cooling system comprises a main radiator line 7 directing coolant through a main radiator 8. The main radiator line 7 comprises a main radiator inlet line 7a, and a main radiator outlet line 7b. The cooling system comprises a main radiator bypass line 9 directing coolant past the main radiator 8. The first three way valve 6 is controlled by a control unit 10. The first three way valve 6 is adjustable in a stepless manner. Thus, it is possible for the first three way valve 6 to receive coolant from the engine outlet line 5 via the inlet opening and distribute a first part of it to the radiator line 7 via a first outlet opening and a second remaining part of it to the radiator bypass line 9 via a second outlet opening. A charge air cooler 11 is arranged in a position upstream of the main radiator 8. A radiator fan 12 and the ram air provide a cooling air stream through the charge air cooler 12 and the main radiator 8 during operation of the vehicle 1.

The cooling system is configured to cool at least one further object 13 than the combustion engine 2. The further object 13 is arranged in an auxiliary circuit 14 of the cooling system. The further object 13 is in this case exemplified as a working medium in a WHR system which is cooled in a condenser 13. Alternatively, the further object may be charge air cooler in a charge air cooler, power electronics for a hybrid vehicle or another object to be cooled to a lower temperature than the combustion engine. The auxiliary circuit 14 comprises an auxiliary radiator 15 arranged upstream of the condenser 13 in view of the ordinary flow direction through the auxiliary circuit 14. The ram air and the at least one auxiliary radiator fan 16 provides a cooling air stream through the auxiliary radiator 15. An auxiliary radiator bypass line 17 directing coolant past the auxiliary radiator 15. A bypass valve 18 controls the coolant flow through the bypass line 17. The bypass valve 18 is controlled by the control unit 10.

A second valve device in the form of a second three way valve 20 receives coolant from the radiator bypass line 9. The second three way valve 20 is controlled by the control unit 10. The second three way valve 20 is adjustable in a stepless manner. The second three way 20 valve has an inlet opening receiving coolant from the main radiator bypass line 9, an outlet opening directing coolant to the engine inlet line 3 and a third opening which may be an inlet opening or an outlet opening. The third opening may work as an inlet opening and receives coolant from the main radiator 8 and direct it to the engine inlet line 3. Alternatively, the third opening works as an outlet opening and directs coolant from the main radiator bypass line 9 to the auxiliary circuit 14. A first temperature sensor 21 senses the temperature of the coolant in the engine outlet line 5. Thus, the first temperature sensor 21 senses a temperature related to the temperature of the combustion engine 2. A second temperature sensor 22a senses the temperature of the coolant in the auxiliary circuit 14 in an upstream position of the condenser 13. A third temperature sensor 22b senses the temperature of the coolant in the auxiliary circuit 14 in a downstream position of the condenser 13. The third temperature sensor 22b senses a temperature related to the temperature of the working medium in the condenser 13. The auxiliary circuit 14 comprises a condenser 23 in an AC system arranged in a position upstream of the condenser 13 in the WHR system. The AC system is used to cool the air in a driving cab of the vehicle 1.

During operation, the control unit 10 receives substantially continuously information from said temperature sensors 21, 22a, 22b about the actual coolant temperatures of the combustion engine 2 and the working medium in the condenser 13. The control unit 10 may also receive information about operating parameters of the WHR system. The control unit 10 may, for example, receive information about the actual condensation temperature in the condenser 13. The control unit 10 may also receive information about operating parameters of the AC system.The control unit 10 estimates a desired condensation temperature of the working medium in the condenser 13. When ethanol is used as working medium, a condensation temperature of about 80°C is desirable during most operating conditions. The control unit 10 estimates a required flow rate and a required temperature of the coolant flow to be directed to the condensers 13, 23 in order to provide the desired condensation temperature in the WHR condenser 13.

During operation, the control unit 10 receives substantially continuously information from the first temperature sensor 21 about the coolant temperature in the engine outlet line 5. In case the coolant temperature in the engine outlet line 5 indicates that the combustion engine 2 has a lower temperature than an efficient operating temperature, the combustion engine 2 does not need to be cooled. The control unit 10 adjusts the first three way valve 6 such that it directs a large part of the coolant flow to the main radiator bypass line 9 and a remaining small part of the coolant flow to the radiator line 7. The second valve device 20 directs the coolant from the main radiator bypass line 9 to the combustion engine 2 without cooling. The smaller part of the coolant flow is usually cooled in the main radiator 8 to temperature low enough to cool the refrigerant in the AC condenser 23 and the working medium in the WHR condenser 13 to a suitable condensation temperature. In this case, it is not necessary to use the auxiliary radiator 15. Thus, the control unit 10 sets the bypass valve 18 in an open position such that the coolant is directed from the main radiator 8 to the condensers 13, 23 via the auxiliary radiator bypass line 17.

In case, the coolant has been cooled to a too low temperature in the main radiator 8, the second three way valve 20 is controlled such that it directs a suitable quantity of uncooled coolant from the main radiator bypass line 9 to the auxiliary circuit 14 where it is mixed with coolant from the main radiator 8. With a suitable mixture of said coolants of different temperatures it is possible to direct coolant of a suitable temperature to the condensers 13, 23, via the auxiliary radiator bypass line 17, at which the working medium in the condenser 13 is cooled to the desired condensation temperature. The coolant leaving the condensers 13, 23 is directed, via the engine outlet line 5, to the combustion engine 2. Thus, the coolant directed from the auxiliary circuit to the combustion engine 2 will during substantially all operating conditions have a sufficient high temperature for rising the temperature of the combustion engine 2 rapidly to its efficient operating temperature.

In case the coolant temperature in the engine outlet line 5 indicates that the combustion engine 2 has a temperature within an efficient operating temperature range, the combustion engine 2 need to be cooled in order to maintain this temperature. The control unit 10 adjusts the first three way valve 6 such that it directs a suitable part of the coolant flow to the radiator bypass line 9 and a remaining part of the coolant flow to the radiator line 7. The second valve device 20 directs a suitable mixture of coolant from the main radiator bypass line 9 and coolant from the main radiator 8 to the combustion engine 2. On one hand, the coolant flow in the main radiator 8 is cooled to a temperature low enough to cool the refrigerant in the AC condenser 23 and the working medium in the condenser 13 to a suitable condensation temperature. In this case, it is not necessary to use the auxiliary radiator 15. Thus, the control unit 10 sets the bypass valve 18 in an open position such that the coolant is directed from the main radiator 8 to the condensers 13, 23 via the auxiliary radiator bypass line 17. On the other hand, the coolant flow in the main radiator 8 is not cooled to a temperature low enough to cool the refrigerant in the AC condenser 23 and the working medium in the condenser 13 to a suitable condensation temperature. In this case, it is necessary to use the auxiliary radiator 15. Thus, the control unit 10 sets the bypass valve 18 in a closed position such that the coolant is directed from the main radiator 8 to the condensers 13, 23 via the auxiliary radiator 15.

In case the coolant temperature in the engine outlet line 5 indicates that the combustion engine 2 has a higher temperature than an efficient operating temperature range, the combustion engine 2 need to be cooled in an optimal manner. The control unit 10 adjusts the first three way valve 6 such that it directs the entire coolant flow to the radiator line 7 and the main radiator 8. The second valve device 20 directs a suitable part of coolant from the main radiator 8 to the combustion engine 2. A remaining part of coolant from the main radiator 8 is directed to the auxiliary circuit 14. In case the coolant flow in the main radiator 8 has been cooled to a temperature low enough to cool the refrigerant in the AC condenser 23 and the working medium in the condenser 13 to a suitable condensation temperature, the control unit 10 sets the bypass valve 18 in an open position such that the coolant is directed from the main radiator 8 to the condenser 13 via the auxiliary radiator bypass line 17. In case the coolant flow in the main radiator 8 is not cooled to a temperature low enough to cool the refrigerant in the AC condenser 23 and the working medium in the condenser 13 to a suitable condensation temperature, the control unit 10 sets the bypass valve 18 in a closed position such that the coolant is directed from the main radiator 8 to the condensers 13, 23 via the auxiliary radiator 15. Consequently, the cooling system is able to maintain an efficient operating temperature of a combustion engine 2 as well as a desired condensation temperatures of the refrigerant in the AC condenser and the working medium in the condenser 13 during substantially all operating conditions.

It is possible to operate the AC system and to cool the air in the driving cab even at times when the combustion engine is not in operation. The vehicle comprises electrical equipment (not shown) for operation of a compressor in the AC system when the combustion engine is not in operation. The cooling system comprises cooling equipment for cooling of the refrigerant in the condenser 23 in the AC system when the combustion engine is not in operation. The cooling equipment comprises an auxiliary coolant pump 24 which is arranged in a return line 25 in the auxiliary circuit 14. The auxiliary pump is electrically driven by electric energy from a battery in the vehicle 1. The return line 25 is provided with an inlet opening 25 a arranged in a position downstream of the condenser 23 in the AC system and in a position upstream of the condenser 13 in the WHR system. The return line 25 is provided with an outlet opening 25b in a position downstream of the auxiliary radiator 15. The return line 25 comprises a one way valve 26. The one way valve 26 allows a flow in the return line 25 defined by the auxiliary pump 24. The one way valve 26 blocks the flow in the return line 25 in the opposite direction. Thus, there is no coolant flow through the return line 25 during the ordinary operation of the cooling system. The cooling system comprises a manual activation member 27, which many be a button or the like, by which it is possible for a person to activate and deactivate the AC system when the combustion engine 2 is not in operation.

The control unit 10 receives information when the AC system has been activated by the manual activation member 27. The control unit 10 sets the first three way valve 6 and the second three way valve 20 in positions in which they block the coolant flow in all parts of the cooling system except in the auxiliary circuit 14. Furthermore, it may set the bypass valve 18 in a closed position such that the coolant flow through the auxiliary radiator bypass line 17 is blocked. Consequently, the auxiliary pump 24 pumps coolant in a closed loop. The coolant absorbs heat in the AC condenser 23. The coolant is directed from the AC condenser 23, via the return line 25, to the auxiliary radiator 15 where it is cooled. The coolant leaving the auxiliary radiator 15 is directed back to the AC condenser 23. Consequently, the auxiliary pump circulates the coolant in a relatively small part of the cooling system. Thus, the auxiliary coolant pump 24 may have a significantly smaller capacity than the ordinary coolant pump 4.

Fig. 2 shows an alternative embodiment of said cooling equipment. In this case, the AC condenser 23 and WHR condenser 13 is arranged in parallel lines 28a, 28b in the auxiliary circuit 14. As a consequence, coolant of the same temperature is directed to the condensers 13, 23. The parallel line 28a comprising the WHR condenser 13 also comprises a one way valve. The one way valve 29 prevent a coolant flow through the WHR condenser 13 when the auxiliary pump 24 is activated. Beyond this difference, the cooling equipment in Fig. 2 corresponds to the cooling equipment in Fig. 1.

Fig 3 shows a front view of the main radiator 8 and the auxiliary radiator 15. In this case, the auxiliary radiator 15 is arranged below the main radiator 8. Two auxiliary radiator fans 16 provides a cooling air stream through the auxiliary radiator 15. The auxiliary radiator fans 16 may be driven independently of the main radiator fan 12. Alternatively, the auxiliary radiator 15 may be arranged above or on a side of the main radiator 11. Preferably, the auxiliary radiator 15 is arranged in a position such that receives a cooling air stream by the ram air and the auxiliary fan radiator fans 16 at the surrounding temperature. In this case, it is possible to cool the coolant to considerably lower temperature than in the main radiator 8.

The invention is not restricted to the described embodiment but may be varied freely within the scope of the claims.

Claims

1. A cooling system configured to cool a combustion engine (2) and at least one further object (13) in a vehicle (1), wherein the cooling system comprises a coolant pump (4) circulating coolant in the cooling system, a main radiator line (7) directing coolant through a main radiator (8), a main radiator bypass line (9) directing coolant past the main radiator (8), a first valve device (6) receiving coolant from an engine outlet line (5) and directing it to the main radiator line (7) and the main radiator bypass line (9), an auxiliary circuit (14) comprising the further object (13), an engine inlet line (3) directing coolant to the combustion engine (2), a main radiator outlet line (7b) directing at least a part of the coolant leaving the main radiator (8) to the auxiliary circuit (14), and a second valve device (20) receiving coolant from the main radiator (8) or the main radiator bypass line (9) and directing it to the auxiliary circuit (14) or the engine inlet line (3), and wherein the auxiliary circuit (14) comprises an auxiliary radiator (15) in which the coolant during the most operating conditions is cooled to a lower temperature than in the main radiator (8), a condenser (23) in an AC system and an auxiliary coolant pump (24) able to circulate coolant between the auxiliary radiator (15) and the condenser (23) in the auxiliary circuit (14) during operating conditions when the combustion engine (2) is not in operation, wherein the auxiliary circuit (14) comprises a return line (25) directing coolant from a position downstream of the auxiliary radiator (15) and the condenser (23) in the auxiliary circuit (14) to a position upstream of the auxiliary radiator (15) and the condenser (23) in the auxiliary circuit (14), characterized in that the return line (25) comprises the auxiliary coolant pump (24) and a one way valve (26).

2. A cooling system according to claim 1, characterized in that the condenser (23) is arranged in series with the further object (13) in the auxiliary circuit (14).

3. A cooling system according to claim 1, characterized in that the condenser (23) and the further object (13) are arranged in parallel lines in the auxiliary circuit (14).

4. A cooling system according to claim 3, characterized in that the line comprising the further object (13) also comprises a one way valve (29).

5. A cooling system according to any one of the preceding claims, characterized in that it comprises a manually activated member (27) configured to initiate activation of the auxiliary coolant pump (24).

6. A cooling system according to any one of the preceding claims, characterized in that the valve devices (6, 20) are configured to be set in positions such they restrict the coolant flow provided by the auxiliary coolant pump (24) to the auxiliary circuit (14).

7. A cooling system according to any one of the preceding claims, characterized in that the first valve device is a three way valve (6).

8. A cooling system according to any one of the preceding claims, characterized in that the second valve device is a three way valve (20).

9. A cooling system according to any one of the preceding claims, characterized in that the first valve device (6) and/or the second valve device (20) are designed to conduct small coolant flow rates with a higher accuracy than larger coolant flow rates.

10. A cooling system according to any one of the preceding claims, characterized in that the auxiliary circuit (14) comprises an auxiliary radiator bypass line (17) and a bypass valve (18) in the form of a two way valve.

11. 1 1. A cooling system according to any one of the preceding claims, characterized in that the further object is a working medium cooled in a condenser (13) in a WHR-system.

12. A cooling system according to any one of the preceding claims, characterized in that the auxiliary radiator (15) is arranged in a position in the vehicle (1) in which it is cooled by an air stream of a lower temperature than the temperature of the air stream through the main radiator (8).

13. A cooling system according to any one of the preceding claims, characterized in that the air stream through the auxiliary radiator (15) is generated by a separate radiator fan (16).