A counter flow heat exchanger is used to col 2000 kg/hr of oil (c p = 2.5 k J/kg K) from 105 degree Celsius to 30 degree Celsius by the use of water entering at 15 degree Celsius. If the overall heat transfer coefficient is expected to be 1.5 k W/m2 K, find out the water flow rate. Presume that the exit temperature of the water is not to exceed 80 degree Celsius

Correct Answer: 1380.2 kg/hr
Mass flow rate of coolant = 2000 (2.5) (105-30)/4.18 (80-15) = 1380.2 kg/hr.