Page 81 - Modelling in Transport Phenomena A Conceptual Approach

62 CHAPTER 3. INTERPHASE TRANSPORT

SUGGESTED REFERENCES FOR FURTHER
STUDY

Bird, R.B., W.E. Stewart and E.N. Lightfoot, 1960, Transport Phenomena, Wiley,
New York.

Cussler, E.L., 1984, How we make mass transfer seem difficult, Chem. Eng. Ed.
18 (3), 124.

Fahien, R.W., 1983, Fundamentals of Transport Phenomena, McGraw-Hill, New
York.

PROBLEMS

3.1 Your friend claims that humid air causes an increase in the gas consumption
of cars. Do you agree?

3.2 Air at 20 "C flows over a flat plate of dimensions 50 cm x 25 cm. If the average
heat transfer coefficient is 250 W/ m2. K, determine the steady rate of heat transfer
from one side of the plate to air when the plate is maintained at 40°C.
(Answer: 625 W)
3.3 Air at 15°C flows over a spherical LPG tank of radius 4m. The outside
surface temperature of the tank is 4 "C. If the steady rate of heat transfer from the
air to the storage tank is 62,000 W, determine the average heat transfer coefficient.
(Answer: 28 W/ m2. K)

3.4 The volumetric heat generation in a hollow aluminum sphere of inner and
outer radii of 20cm and 50cm, respectively, is given by
R = 4.5 x io4 (I + 0.6 r2)

in which 9 is in W/m3 and r is the radial coordinate measured in meters. The
inner surface of the sphere is subjected to a uniform heat flux of 15,000 W/ m2,
while heat is dissipated by convection to an ambient air at 25 "C through the outer
surface with an average heat transfer coefficient of 150W/m2.K. Determine the
temperature of the outer surface under steady conditions.
(Answer: 92.3 "C)