Hot water (Cp = 4180 J/kgK) at a rate of 2 kg/s enters a parallel-flow double-pipe heat exchanger used in thermal therapy of treating cancers at 80 C and leaves at 60 C. Blood enters at 37 C and leaves at 41.2 C. The overall heat transfer coefficient of the heat exchanger is 300 W/m2 K.

Assume that:

(1) steady operating conditions exit,

(2) the heat exchanger is well-insulated,

(3) changes in the kinetic and potential energies of fluid stream are negligible,

(4) the overall heat transfer coefficient is constant and uniform, and

(5) fluid properties are constant.

Determine the heat-transfer area required.