Fourth year, Department of Mechanical Sandwich
Engineering
First and second Units Questions.
Answer ALL Questions
Part-A (2 Marks)
1. State Fourier’s law of heat
conduction.
2. State newton’s law of cooling
3. What is meant by heat transfer?
4. What do you understand by conduction?
5. What are the modes of heat transfer?
6. What do you understand by forced and free
convection?
7. What is meant by convection?
8. What is meant by Nuselt number?
9. What is meant by laminar flow?
10. What is meant by turbulent flow?
PART
B
11) A furnace wall is made up of three
layers of thickness 25 cm, 10 cm and 15 cm with thermal conductivities of 1.65
k and 9.2 W/mK respectively. The inside is exposed to gass at 1250oC
with a convective coefficient of 25 W/m2K and the inside surface is
at 1100oC, the outside surface is exposed to air at 25oC
with convective coefficient of 12 W/m2K. Determine i) the
unknown thermal conductivity. ii) The overall heat transfer coefficient. iii)
All the surface temperature.
12) Derive the heat conduction equation
for Cartesian coordinates
13) Derive the heat conduction equation
for Cylindrical coordinates
14) A thick wall tube of stainless steel
[k= 77.85 KJ/hr moC) 25 mm ID and 50 mm OD is covered with a 25 mm
layer of asbestos [k= 0.88 KJ/hr moC). If the inside wall
temperature of the pipe is maintained at 550oC and the outside of
the insulator at 45oC. Calculate the heat loss per meter length of
pipe.
15) Air at 20oC at atmospheric
pressure flows over a flat plate at a velocity of 3 m/s. If the plate is 1 m
wide and 80oC, Calculate the following at x=300mm.
1. Hydrodynamic boundary layer thickness
2. Thermal boundary layer thickness
3. Local friction coefficient
4. Average friction coefficient
5. Local heat transfer coefficient
6. Average heat transfer coefficient
7. Heat Transfer
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