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Question Bank
Department :Mechanical
Subject code : ME6502
Subject Name : Heat and Mass Transfer
Regulation :2013
PART-A (2 marks)
1.State Fourier’s law of heat conduction.
2.Write down the three dimensional steady state equation for Cartesian and Polar coordinates.
3. What do you understand by critical radius of insulation and give it's expression.
4.What is meant by natural and forced convection?
5. In which mode of heat transfer is the convection heat transfer coefficient usually higher. Why?
6. Define overall heat transfer coefficient.
7.What is lumped heat analysis? When is it used?
8. What are Heisler’s charts?
9.What is hydro dynamic and thermal boundary layer thickness?
10.Draw the velocity and temperature profiles for free convection on a hot vertical plate.What is meant by Film wise and Drop wise condensation?
11. What is meant by LMTD & NTU ?
12.What is black body and gray body?.
13. State Kirchoff’s law of radiation.
14. What is meant by shape factor?
15. What is meant by Pool boiling?
16. Define the terms dropwise and filmwise condensation.
17. What is LMTD?
18. What is meant by shape factor and mention it’s significance.
19. Distinguish between irradiation and radiosity.
20. State Fick’s law of diffusion and give it’s expression.
21. How mass transfer takes through diffusion and convection?
22. Define mass concentration and molar concentration.
23. What is meant by mass transfer coefficient and types of mass transfer?
24. Define shape factor and mention it’s significance.
25. Define convective mass transfer and give any two examples.
26. What is meant by molecular diffusion
27. Define Scherwood and Schmidt number.
28. What is meant by free and forced convective mass transfer?
29. Discuss the radiation characteristics of carbon dioxide and water vapor.
Part - B (16 Marks)
1. A furnace walls made up of three layers , one of fire brick, one of insulating brick and one of red brick. The inner and outer surfaces are at 870 C and 40 C respectively. The respective co- efficient of thermal conduciveness of the layer are 1.0, 0.12 and 0.75 W/mK and thicknesses are 22 cm, 7.5, and 11 cm. assuming close bonding of the layer at their interfaces, find the rate of heat loss per sq.meter per hour and the interface temperatures.
2. When 0.6 kg of water per minute is passed through a tube of 2 cm diameter, it is found to be heated from 20 C to 60 C. the heating is achieved by condensing steam on the surface of the tube and subsequently the surface temperature of the tube is maintained at 90 C. Determine the length of the tube required for fully developed flow.
3. A steel tube with 5 cm ID, 7.6 cm OD and k=15W/m C is covered with an insulative covering of thickness 2 cm and k 0.2 W/m C. A hot gas at 330 C with h = 400 W/m2 C flows inside the tube. The outer surface of the insulation is exposed to cooler air at 30° C with h = 60 W/m2 C. Calculate the heat loss from the tube to the air for 10 m of the tube and the temperature drops resulting from the thermal resistances of the hot gas flow, the steel tube, the insulation layer and the outside air.
4. Write short notes on fins.
5. A long carbon steel rod of length 40 cm and diameter 10 mm (k = 40 w/mK) is placed in such that one of its end is 400 C and the ambient temperature is 30 C. the film co-efficient is 10 w/m2K. Determine
(i) Temperature at the mid length of the fin.
(ii) Fin efficiency
(iii) Heat transfer rate from the fin
(iv) Fin effectiveness
6.A 12 cm diameter long bar initially at a uniform temperature of 40 C is placed in a medium at 650 C with a convective co efficient of 22 W/m2K calculate the time required for the bar to reach 255 C. Take k = 20W/mK, ρ = 580 kg/m3 and c = 1050 J/kg K.
7. Air at 25 C flows past a flat plate at 2.5 m/s. the plate measures 600 mm X 300 mm and is maintained at a uniform temperature at 95 C. Calculate the heat loss from the plate, if the air flows parallel to the 600 mm side. How would this heat loss be affected if the flow of air is made parallel to the 300 mm side.
8. Write short notes on dimensionless parameters used in forced convection.
9. A vertical pipe 80 mm diameter and 2 m height is maintained at a constant temperature of 120 C. the pipe is surrounded by still atmospheric air at 30 C . Find heat loss by natural convection.
10. Sketch the boundary layer development of a flow over a flat plate and explain the significance of the boundary layer.
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