1. Water at a flow rate of = 0.25 kg/s is cooled from 70 C to 30c by passing it through a thick-walled tube of internal diameter ofDi =50 mm and an external diameter of D = 60 mm. Hot Water iscooled by blowing cold air at T? = 15 C in cross flow over thetube. Velocity of the air over the tube is 20 m/s. Evaluating thewater properties at 325 K from Table A.6 and evaluating airproperties at a film temperature of 300 K from Table A.4 foroutside flow, answer the following questions: Assume the pipe ismade out of stainless steel with thermal conductivity of15W/m/k
(a) What is the Reynolds number of the internal flow? [1]
(b) Using Dittus_Boetler correlation (Eqn 8.60), compute theconvective heat transfer coefficient for the internal flow [2]
(c) Using Churchill-Bernstein correlation, compute theconvective heat transfer coefficient for the external flow [2]
(c) By doing an energy balance, compute the length of the tube[3]
(d) What is the total heat loss? [1]
