If applicable:
Rate of Heat energy Input Q̇ (KJ/s) =1100,
Temperature (K) Heat transfer coefficient (U) (Wm-2K-1) Cold =323, Hot =700,
Heat transfer coefficient (U)(Wm-2K-1)=330,
A hot water circular cross-section pipe of length 5 metres, outer radius of 4 cm and negligible
thermal resistance acts as an open system heat exchanger allowing the transfer of heat from the hot
water inside the pipe to the atmosphere. Given (in the table below) the initial temperatures of the
hot water and cold air, heat transfer coefficient of the air/steam film, 0.5U and U respectively,
Calculate:
a) The thermal resistance of the steam film (inside)
b) The thermal resistance of the air film (outside)
c) The heat transfer (loss) per unit length of the pipe
d) The efficiency of the heat exchanger, (given the heat input in the table below)