Answer Happy

QUESTION 1 20 MARKS A counter flow shell-and-tube heat exchanger is to be used to heat air from 4°C to 82°C, flowing at the rate of 21.8 tons per hour. Heating action is to be provided by the condensation of steam at 99°C in the shell. The internal diameter of the steel tubes is 2.5 inches. Find: a) The size of the heat exchanger (surface area and tube length), assuming a mass velocity of 39 tons/hr.m? b) The air-side pressure drop. You may assume that the area of the heater is twice the flow area of the tubes. Additional information At the mean air temperature, the air tables list: Pr = 0.71 Cp = 32.46J/kg. "C K = 3.214 J/m.hr. °C U= 0.0698 kg/m.hr Friction factor (t) is expressed as f = 0.046/(Re)".2 Density of air at 4°C = 1.23 kg/m and at 82°C = 0.96 kg/m3 ke = 0.21 and kc = 0.31