Method for controlling a cooling system delivering coolant to heat exchanger in a vehicle

A method for controlling a cooling system delivering coolant to a heat exchanger in a vehicle, wherein

• the cooling system comprises:
• a radiator line configured to direct coolant to a radiator in which the coolant is cooled to a first temperature;
• a radiator bypass line directing coolant past the radiator;
• a heat exchanger line receiving coolant from the radiator line and from the radiator bypass line and directing the coolant to a heat exchanger;
• a heat exchanger bypass line receiving coolant from the radiator line and the radiator bypass line and directing the coolant past the heat exchanger;
• a thermostat receiving a coolant flow range ({dot over (m)}) at a second temperature, wherein the thermostat in a closed position directs the entire coolant flow range ({dot over (m)}) to the radiator bypass line, in a partly open position directs a first coolant flow range ({dot over (m)}1) to the radiator line and a second coolant flow range ({dot over (m)}2) to the radiator bypass line, and in a fully open position directs the entire coolant flow rate ({dot over (m)}) to the radiator line;
• and
• a flow regulating mechanism directing coolant from the radiator line and the radiator bypass line to the heat exchanger line and/or the heat exchanger bypass line, wherein;
• during operating conditions when the thermostat is in the partly open position, the method comprises the steps of:
• estimating a desired cooling temperature of a medium in the heat exchanger,
• estimating a cooling effect of the coolant in the radiator from information about the cooling air flow through the radiator and from performance data of the radiator at varying air flows,
• calculating the coolant flow rate ({dot over (m)}1) through the radiator line from information of the cooling effect of the coolant in the radiator, temperature drop (t1-t2) of the coolant in the radiator and the specific heat capacity (cp) of the coolant,
• calculating the coolant flow rate ({dot over (m)}2) through the radiator bypass line;
• calculating a coolant flow rate ({dot over (m)}3) and coolant temperature combination at which the medium in the heat exchanger is cooled to the desired temperature;
• and
• adjusting the flow regulating mechanism such that coolant at the selected flow rate ({dot over (m)}b) and temperature combination is directed to the heat exchanger line and the heat exchanger.