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Max. Marks: 100

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F192005 Pages:3

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
SIXTH SEMESTER B.TECH DEGREE EXAMINATION(S), DECEMBER 2019

Course Code: ME302
Course Name: Heat and Mass Transfer

PARTA

Answer any three full questions, each carries 10 marks.
Write down the general heat conduction equation in Cartesian coordinates.
Reduce the equation for steady state one dimensional heat conduction across a
plane wall with internal heat generation
With proper figures, derive an equation for steady state temperature distribution
across a plane wall with internal heat generation. Both the surfaces have unequal
temperatures (T,and 72) and subjected to convection heat transfer. The surface
heat transfer coefficient 15 h and fluid temperature is T,,.
Derive an equation for the thermal resistance across a hollow sphere
A hollow sphere of inside radius 3 cm and outside radius 5 cm is electrically
heated at the inner surface at constant rate of 10° W/m’. At the outer surface it
dissipates heat by convection into a fluid at temperature 100 C with heat transfer
coefficient 400W/m’K. The thermal conductivity of the material of sphere is
15W/mK. Determine inner and outer surface temperatures.
Explain Hydrodynamic Boundary Layer for flow over a flat plate
Air at pressure of | atm and temperature 60 C flows over a flat plate which
maintains a surface temperature of 100 ©. The plate has a length of 0.2m (in the
flow direction) and width of 0.1m. The Reynolds number based on the plate
length is 40000. What is the rate of heat transfer from plate to air? If the free
stream velocity of air is doubled and the pressure is increased to 2.5 atm, what is
the rate of heat transfer?
Explain the physical significance of Prandtl No. and Nusselt No.
Atmospheric air at 25 © and velocity of 0.5m/s flows over a SOW incandescent
bulb whose surface temperature is maintained at 140 0. The bulb may be
approximated as a sphere of 50 mm diameter. What is the rate of heat loss by

convection to air?

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Duration: 3 Hours

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