Download AKTU B-Tech 3rd Sem 2016-2017 NME 302 Mechanics Of Solids Question Paper

VASAVI COLLEGE OF ENGINEERING (Autonomous), HYDERABAD

B.E. (Mech. Engg.) VI Semester

HEAT TRANSFER (Open Elective - II)

Time: 3 hours Max. Marks: 70

Note: Answer ALL questions in Part-A and any FIVE questions from Part-B

Part-A (10 x 2 = 20 Marks)

1. Define Thermal Conductivity and give its units.

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2. What are the different modes of heat transfer?
3. Define Fin efficiency and Fin effectiveness.
4. What is meant by lumped system analysis?
5. Define the Grashoff number and explain its physical significance.
6. Differentiate between Natural and Forced convection.

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7. What is meant by the LMTD correction factor?
8. State Stefan Boltzmann’s law of radiation.
9. Define Radiosity and Irradiation.
10. What is a gray body?

Part-B (5 x 10 = 50 Marks)

1. a) Derive the general heat conduction equation in Cartesian coordinates.

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   b) A furnace wall is made up of steel plate 10 mm thick (k = 62.8 kJ/m-hr-°C) lined on the inside with silica bricks 150 mm thick (k = 2.33 kJ/m-hr-°C) and on the outside with magnesia bricks 150 mm thick (k = 6.97 kJ/m-hr-°C). The inside and outside surface temperatures of the wall are 850°C and 150°C respectively. Evaluate the heat loss through the wall and the temperature at the steel and silica brick interface.

2. a) Explain the different types of fin profiles with neat sketches.

   b) A steel rod (k = 30 W/m-deg) 1 cm in diameter and 5 cm long protrudes from a wall which is maintained at 100°C. The rod is insulated at its tip and is exposed to an environment at 30°C. The heat transfer coefficient is 50 W/m²-deg. Calculate the fin efficiency, temperature at the tip of the fin, and the rate of heat dissipation.

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3. a) Explain the physical significance of dimensionless numbers used in convection.

   b) A horizontal heated plate measuring 1.5 m x 2 m is maintained at 300°C and exposed to still air at 20°C. Calculate the free convection heat loss from the top and bottom surfaces of the plate.

4. a) Differentiate between film-wise and drop-wise condensation.

   b) Saturated steam at 100°C condenses on the outer surface of a vertical tube 1 m long and 8 cm outer diameter. If the tube surface is maintained at a uniform temperature of 80°C, calculate the rate of heat transfer and the rate of condensation of steam.

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5. a) Derive an expression for the effectiveness of parallel flow heat exchanger.

   b) Hot oil with a capacity rate of 2500 W/K flows through a double pipe heat exchanger. It enters at 360°C and leaves at 300°C. Cold fluid enters at 30°C and leaves at 200°C. If the overall heat transfer coefficient is 800 W/m²K, determine the heat exchanger area required for (i) Parallel flow and (ii) Counter flow.

6. a) Explain the concept of a black body.

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   b) Two large parallel plates are at a temperature of 1000 K and 600 K. Find the net heat exchange per square meter area if the emissivities of the hot and cold plates are 0.8 and 0.5 respectively. If a polished aluminum shield with emissivity of 0.1 on both sides is placed between them, find the percentage reduction in heat transfer.

7. Write short notes on any two of the following:

   1. Transient Heat Conduction
   2. Boundary Layer Concepts

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   3. Heat Exchanger Fouling

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