Reg No.:

03000ME3220520032"°:
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

Sixth semester B.Tech degree examinations (S), September 2020

Course Code: ME322
Course Name: Heat transfer

Max. Marks: 100 Duration: 3 Hours

1 2)
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2 9)
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Answers should be brief and to the point
Use of Standard Heat Transfer Data book is permitted

PARTA

Answer any three full questions, each question carries 10 marks. Marks
Steady state temperature distribution in a large slab of 50 mm thickness is given (5)

by T(x) = 200 + 2000 x”. The thermal conductivity k of the slab is 50 W/m/K.

Find the heat generation rate in the slab as well as the heat fluxes at both the wall

faces. Using these values, show that the energy balance occurs across the
thickness of the slab.

A long 20 mm dia copper tube carries heated water and the steady wall (5)
temperature of the tube is 80 deg C. The heat transfer coefficient by free
convection ‏مط‎ equals 6 W / व / K and the surrounding ambient temperature is 0

deg C. Find the heat loss by convection and radiation from the external surface of

the pipe per unit length of the pipe.

An orange, whose shape can be approximated as a 10 cm diameter sphere, is (4)
initially at a uniform temperature of 30 deg C. It is placed then inside a
refrigerator in which air is at a temperature of 2 deg C and the convective heat
transfer coefficient is 50 W / पा? / 18. Find the time taken by the orange when its

center temperature reaches 10 deg C. Assume that the thermal diffusivity of the
orange 0 = 1.4 ‏ع‎ 10 ` 1 m’/s and its conductivity k is 0.59 W/m/K.

An electrical cable 5 mm diameter is made from stainless steel wire and has an (6)

electrical resistance of 6 x 101 ohms / meter. It carries a current of 700 amperes

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