Problem 9: Heat exchangers The objective of the engine radiator is to cool the water coming from the engine by the outside air, i.e. to exchange heat from the hot water to the outside air. Upper Hose Thermostat Radiator Pressure Cap Fan Water Pump Lower Hose Transmission cooling lines © 2000 How Stuff Works How much will be the temperature of the exit air from the above radiator? knowing that: The water mass flow rate is 0.5 1/min, The air mass flow rate is 300 l/min, The inlet temperature of air is 25 °C The water inlet and exit temperatures are 60 °C and 55 °C, respectively.