A shell-and-tube heat exchanger is used for the heating of oil from 20 C to 30 C; the oil flow rate is 12 kg/s (Cpo 2.2 kJ/ kg K). The heat exchanger has one shell pass and two tube passes. Hot water (Cpw 4.18 kJ/kg K) enters the shell at 75 C and leaves the shell at 55 C. The overall heat-transfer coefficient based on the outside surface of the tubes is estimated to be 1080 W/m2 K. Determine

a. the corrected logarithmic-mean temperature difference b. the required surface area in the exchanger