The outlet temperature of the cold fluid in oC is

Question

In a counter flow heat exchanger, for the hot fluid the heat capacity = 2 kJ/kg K, mass flow rate=5kg/s, inlet temperature = 150⁰ C, outlet temperature = 100⁰ C. For the cold fluid heat capacity = 4kJ/kg K, mass flow rate = 10 Kg/s, inlet temperature = 20⁰ C. neglecting heat transfer to surroundings, the outlet temperature of the cold fluid in ⁰C is                                                 

      (a) 7.5                                                                 (b) 32.5

      (c) 45.5                                                               (d) 70.0