A. A tubular heater of the counterflow type is used to heat 1.26 kg/s of fuel oil (cp = 3.14 kJ/kg K) from 10∞C to 26.7∞C. Heat is supplied by means of 1.51 kg/s of water which enters the heater at 82∞C.
(a) Derive an equation relating the temperatures of oil and water at any section of the heater.
(b) Determine the necessary surface area if the overall heat transfer coefficient is 1.135 kW/m2 K.
B. A one shell pass, two tube pass heat exchanger has a total surface area of 5 m2, and its overall heat transfer coefficient based on that area is found to be 1400 W/ m2 K. If 4500 kg/h of water enters the shell side at 315∞C while 9000 kg/h of water enters the tube side at 40∞C, find the outlet temperatures using (a) the F-LMTD method and (b) the e-NTU method. Take cp for both fluid streams as 4.187 kJ/kg K.
