1355. A composite wall consists of two plates A and B placed in series normal to the flow of heat. The thermal conductivities are kA and kB and the specific heat capacities are CPA and CPB for plates A and B respectively. Plate B has twice the thickness of plate A. At steady state, the temperature difference across plate A is greater than that across plate B, when

CPA > CPB
CPA < CPB
KA < 0.5kB
KA>2 kB
✅ The correct answer is option C.

1357. The overall heat transfer co-efficient for a shell and tube heat exchanger for clean surfaces is U0 = 400 W/m².K. The fouling factor after one year of operation is found to be hd0 = 2000 W/m².K. The overall heat transfer co-efficient at this time is

1200W/m².K
894W/m².K
333W/m².K
287 W/m².K
✅ The correct answer is option C.