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03000ME322052002

What is meant by a grey surface and a diffuse surface?
Two large plates that are at temperatures T; and 2 and having an emissivity of
0.5, exchange heat by radiation. Find the emissivity of a plate that is to be placed
in between these plates which acts as a shield, so that the heat flux reduces to one
fourth.
The temperature of an electrical incandescent filament bulb is 2500 deg K.
Assuming that its emission is close to black body radiation, estimate the fraction
of its total radiation heat energy emitted that is in the visible spectrum. What is
the wave length at which the emitted energy is maximum? Comment on your
answer.
In a heat exchanger hot fluid enters at 60 deg C and leaves at 48 deg C. The cold
fluid enters at 35 deg C and leaves at 44 deg C. Find the mean temperature
difference for (a) parallel flow (b) counter flow and (c) single pass cross flow
(unmixed) configurations.
What are the two major approaches to heat exchanger design? Discuss their
relative advantages and limitations.
What is fouling of heat exchangers? Explain how this is taken care of in heat
exchanger design.
A one-shell pass two tube-pass heat exchanger is to be designed to heat 0.5 Kg/s
of water entering the shell side at 10 deg C, The hot fluid oil enters the tube at 80
deg C with a mass flow rate of 0.3 Kg/s and leaves at 30 deg C. the overall heat
transfer coefficient U 250 W/m7/K. Assume the specific heat of oil Cp is 2
KJ/kg/K calculate the surface area of the heat exchanger required.
PART C

Answer any four full questions, each carries 10 marks.
Air free saturated steam at 65 °C condenses on the surface of a vertical tube of
outer diameter 2.5 cm. The tube surface is maintained at a uniform temperature
of 35 °C. Calculate the length of the tube required to have a condensate flow rate

of 6x 10 *kg/s.

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