1 How do you define the heat transfer coefficient? What is the range of
h
in free convection for gases?
2 A thin disk is being welded at a point located at
r
and è with 0
r
D/2 and 0 è ð and
D
is the disk radius. Is temperature distribution in this disk 1-D? What coordinate system do you use to find temperature distribution in the disk?
3 What is the difference between heat transfer coefficient and the overall heat transfer coefficient?
4 Temperature difference across a fuel pellet, operating at
q′ = 10 kW/ft is 700 F. Maintaining the same
q′ , what is the change in temperature gradient across the pellet if the pellet diameter was 10% smaller?
Q35:
1 What is the advantage of an annular fuel as compared with a solid fuel pellet?
2 A cylinder has Fo = 0.05. Is the Heisler solution applicable to this cylinder?
3 What is the advantage of analytical solution compared with numerical solutions or experimental correlations?
4 What does
k
in Biot number and in Nusselt number stand for? State the interpretation of each number.
5 What is the difference between
V
x
and (V
x)f?. Similarly, identify the difference between
T
and
T
f.
Q36:
1 Which scientist first identified the boundary layer? What is the significance of the Prandtl number?
2 In the analytical derivation of external and internal temperature profiles, we assumed thermal properties to be independent of temperature. Is it then correct to say that in such circumstance the temperature and the velocity fields are independent?
3 What is the von Karman method for the development of the energy equation in the boundary layer?
4 How accurate is the thickness of boundary layer obtained from a force balance in the boundary layer?
Q37:
1 What are the key assumptions, which were made to obtain an analytical solution for the thickness of the thermal boundary layer?
2 Consider heat convection for laminar flow of water in a pipe. What is the effect of doubling the flow rate on the Nusselt number? What is the effect of using motor oil instead of water on
h?
3 What is the difference between the Dittus-Boelter and the Seider-Tate correlations? What is the range of applicability for the Pr number? Are these correlations applicable to liquid metals?
4 What was the role of ether in classical mechanics and electromagnetism?