Advance Heat Transfer(Department Elective - I) — Winter 2018

Give some examples of conduction with internal heat generation.

Explain the terms: Fin efficiency and Fin effectiveness.

Discuss various regimes of pool boiling with neat sketch.

Define Biot number. State its importance in transient heat conduction analysis.

What is lumped system analysis and when is it applicable?

Show that maximum temperature in a plane wall with heat generation whose one face is insulated and other face kept at is given by

Derive an expression for temperature distribution during steady state heat conduction with internal heat generation and exposed to convection environment in hollow cylinder.

Explain heat transfer from the human body.

What is irregular body? How the heat transfer analysis carried out for irregular bodies.

Explain radial fins of rectangular and parabolic profiles.

Give difference between free convection and forced convection with suitable examples.

Explain heat transfer in high velocity flow with neat sketch.

Astainless steel wire (k = 19 W/mk) 3 mm in diameter and one metre long has current flowing, I = 200 A Resistivity, ρ = 70 µ ohm/cm The wire is submerged in liquid at 110 0C and the surface heat transfer coefficient h is 4 kW/m2K. Calculate the central temperature of wire.

The filament of a 60 Wlight bulb may be considered as black body radiating into a black enclosure at 60 0C. The filament diameter is 0.1 mm and length 50 mm. Considering radiation determine the filament temperature.

Explain difference between filmwise and dropwise condenastaion.1

Acopper bus bar 25 mm diameter is cooled by air at 30 0C and flowing past the bus bar with a velocity of 3 m/s. If the surface temperature of bar is not to exceed 80 0C and the resistivity of copper is 0.0175 x 10-6 ohm.m3/m, calculate the following:

The heat transfer coefficient from the surface of bus bar to air

The permissible current intensity for the bus bar. Assume N = 0.44 R 0.5 for 10 < R < 103 u e e = 0.22 R 0.6 for 103 < R < 2 x 105 e e Take thermo physical properties of air at 30 0C are: k = 0.02673 W/mk, ν = 16 x 10-6 m2/s

Differentiate boiling and condensation.

Discuss radiation effects on temperature measurements.

Define shape factor. Discuss salient features of shape factor.

Asolid steel ball 5 cm in diameter and initially at 450 0C is quenched in a controlled environment at 90 0C with convection coefficient of 115 W/m2K. Determine the time taken by centre to reach a temperature of 150 0C. Take thermophysical properties as: C = 420 J/kgK, ρ = 8000 kg/m3, k = 46 W/mK

Discuss radiation properties of a participating medium.

Explain in brief emmisivity and absorptivity of gases and gas mixtures.

What is Beer’s law? Why do surfaces absorb differently for solar or earthbound radiation?