The required heat exchange area is

Question

Cold water flowing at 0.1 kg/s is heated from 20⁰C to 70⁰C in a counter-flow type heat exchanger by a hot water stream flowing at 0.1 kg/s and entering at 90⁰C. The specific heat of water is 4200 J(kg K) and density is 1000 kg/m³. If the overall heat transfer coefficient U for the heat exchanger is 2000 W/ (m² K), the required heat exchange area (in m²) is    

      (a) 0.052                                                             (b) 0.525

      (c) 0.151                                                             (d) 0.202