HEAT TRANSFER PAPER 2

DOWNLOAD MECHANICAL ENGINEERING PREVIOUS YEARS QUESTION PAPERS B.TECH PTU THIRD YEAR

HEAT TRANSFER ME 303 5th Semester (JUNE 2005) (NEW)

Note: Question No. 1 carrying 20 marks is compulsory. Attempt any four questions from Section B and any two from Section C

Section A 2 marks each

I

1. What is meant by thermal resistance?
2. What is the critical radius of insulation of cylinder?
3. What is the importance of neglecting radial heat flow in fins?
4. Define Thermal Diffusivity.
5. What is the limiting value of Biot number to assume that the body is at uniform temperature?
6. Why aluminium is used as a fin material?
7. What is Wein’s displacement law?
8. How is the convection heat transfer coefficient defined?
9. Define pool boiling.
10. What is critical heat flux?

Section B 5 marks each

II Establish general heat conduction equation in cylindrical co-ordinates.

III If both the surfaces of a long plate with uniform heat generation are maintained at the same constant temperature, which point of the plate will attain maximum temperature and why?

IV Two parallel plates (black) 1 m x 2 m are kept 1 m apart. One plate is maintained at 800 oC while the second plate is held at 200 oC. Calculate the net radiant heat exchange between the two plates.

V A vertical plate of length 1 m and width 0.5 m at 92 oC is exposed to saturated steam at 100 oC. Calculate the average heat transfer coefficient.

VI How does one determine the rate of heat transfer in a heat exchanger if its effectiveness is known?

Section C 10 marks each

VII It is desired to use a shell and tube heat exchanger with one shell pass and two tube passes to cool oil from 120 oC to 50 oC. The oil flows through the tubes while the cooling water flows through the shell. The cooling water enters the heat exchanger at 20 oC and leaves it at 40 oC. Determine the correction factor to LMTD.

VIII (a) An electrically heated platinum wire is submerged in saturated liquid water at 100 oC. Determine the heat flux if the excess temperature is 6 oC.
(b) Give a detailed note on radiation exchange between Black bodies.

IX (a) Consider an infinitely long fin of rectangular cross section and derive the relation to determine the temperature distribution in the fin.
(b) It is desired to use 1 metre long tungsten steel rod (k= 54 W/mK) as a heating element to dissipate 100 kW in a fluid at 10 oC. If the maximum allowed temperature in the rod is 750 oC, determine the diameter of the heating element, assuming that the film coefficient between the heating element and the fluid is 200 W/m2K.