Indian Institute of Technology KharagpurDepartment of Chemical Engineering

Make-up Class Test, Spring 2015Subject: Heat Transfer (CH21004)

Feb, 2015Time: 40 MinsFull Marks: 40

No. Students: 5

Instructions: Answer all questions. Read the questions carefully before answering.Assume any missing data suitably. State all assumptions clearly and explicitly.

1. (5 marks) What do you mean by thermally fully developed flow?

2. (5 marks) Explain the construction and function of a ‘floating tube sheet’ for shell andtube heat exchanger.

3. (15 marks) Consider pressurized water, engine oil, and NaK (22%/78%) flowing in a 20mm diameter tube. Determine the mean velocity, the hydrodynamic entry length, thethermal entry length for each of the fluids when the fluid temperature is 366 K and theflow rate is 0.01 kg/s.

4. (15 marks) Water flowing at 2 kg/s through a 40 mm diameter tube is to be heatedfrom 25 to 75 oC by maintaining the tube surface temperature at 100 oC.

(a) What is the required tube length for these conditions?

(b) In order to design a water heating system, we wish to consider using tube diametersin the range from 30 -50 mm. What are the required tube lengths for water flowrates of 1, 2 and 3 kg/s? Represent the design information graphically.

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