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00000CH401121902

PART B

Answer any two full questions, each carries 15 marks.
Determine the heat loss from a rectangular fin of length of 60 mm, width 0.30m
and thickness 4mm to the ambient air having a temperature of 175°C. The heat
transfer coefficient between the air and the fin surface is 680 W/m?.K. The
surface temperature of air is 260 °C. The thermal conductivity of the fin is
103W/m.K. Derive the equations that you use to solve the problem.
Consider 2 concentric spherical shells of radii kR and R. The inner surface of the
outer one is at T=T, and the outer surface of the inner one is to be maintained at
a low temperature 11. Dry air at temperature T= T; is blown outward radially
from the inner shell into the intervening space and out through the outer shell.
Develop an expression for the required rate of heat removal from the inner
spheres as a function of the mass rate of flow of gas. Assume steady laminar
flow and low gas velocity.
Calculate the thermal conductivity of a gas mixture containing 20 mol% 002
and 80 mol% 11) at 1 atm and 300K. Given

Thermal Conductivity Viscosity(g/s.cm)
(Cal/s.cm.K)
CO, 3830 1495x10"

Derive an expression for temperature distribution T(x) in a viscous fluid in
steady laminar flow between large flat parallel plates kept 2B apart. Both plates
are maintained at constant temperature To. Take in to account explicitly the heat
generated by viscous heat dissipation. Neglect the temperature dependence of ப
and k.
PART ^
Answer any two full questions, each carries 15 marks.
Explain various types of fluxes in mass transport with their representations.

Explain kinetic theory of diffusion of gases at low density and explain its
temperature and pressure dependency.

An instantaneous dimerization reaction, 2A > B is taking place on a catalyst
surface. The effective gas film thickness on the catalyst surface may be taken as
‘6’. Using suitable assumptions, develop expressions for the concentration
profile of the component A and the molar flux of A through the gas film.
Calculate steady state mass flux of helium at 500°C. The partial pressure of
helium is latm at lower end and zero at the upper surface of the plate. Thickness
of the pyrex plate is 107 mm and its density is 2.6 g/cm*. The solubility and
diffusivity of helium in pyrex are reported as 0.0084 volume of gaseous helium
per volume of glass and 0.2x107 cm’/s respectively.

Derive equation of continuity for binary mixture in terms of mass units.

AK

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