1. Water at a flow rate of = 0.25 kg/s is cooled from 70 C to...

1. Water at a flow rate of = 0.25 kg/s is cooled from 70 C to 30 c by passing it through a thick-walled tube of internal diameter of Di =50 mm and an external diameter of D = 60 mm. Hot Water is cooled by blowing cold air at T? = 15 C in cross flow over the tube. Velocity of the air over the tube is 20 m/s. Evaluating the water properties at 325 K from Table A.6 and evaluating air properties at a film temperature of 300 K from Table A.4 for outside flow, answer the following questions: Assume the pipe is made out of stainless steel with thermal conductivity of 15W/m/k

(a) What is the Reynolds number of the internal flow? [1]

(b) Using Dittus_Boetler correlation (Eqn 8.60), compute the convective heat transfer coefficient for the internal flow [2]

(c) Using Churchill-Bernstein correlation, compute the convective 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]

Expert Solution

samet mamat answered 2 years ago

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