Heat Transfer Problems Solved - Part 1

0:32 -- 1. In a counter-flow heat exchanger, the hot fluid is cooled from 110° C
to 80° C by a cold fluid which, gets heated from 30° C to 60° C.
LMTD for the heat exchanger is

2:45 -- 2. In a counter-flow heat exchanger, the product of specific heat and
mass flow rate is same for the hot and cold fluids. If NTU is equal to
0.5, then the effectiveness of the heat exchanger is

6:02 -- 3. A body at 500 K cools by radiating heat to ambient atmosphere
maintained at 300 K.When the body has cooled to 400 K, the cooling
rate as a percentage of original cooling rate is about.

7:45 -- 4. 40% of incident radiant energy on the surface of a thermally
transparent body is reflected back. If the transmissivity of the body
be 0.15, then the emissivity of surface is

9:13 -- 5. Two insulating materials of thermal conductivity K and 2K are
available for lagging a pipe carrying a hot fluid. If the radial
thickness of each material is the same

10:47 -- 6. A fluid of thermal conductivity 1.0 W/m-K flows in fully developed
flow with Reynolds number of 1500 through a pipe of diameter 10
cm. The heat transfer coefficient for uniform heat flux and uniform
wall temperature boundary conditions are, respectively,

13:38 -- 7. The plane wall has a thermal conductivity of 1.15 w/mk. If the inner
surface is at1100 oC and the outer surface is at 350 oC, then the
design thickness (in meter) of the wall to maintain a steady heat flux
of 2500 W/m2 should be

15:01 -- 8. Assume a natural convection heat transfer on a vertical flat plate
surrounded by a fluid. Where will be the fully developed turbulent
layer of fluid established, if the plate is hotter than the fluid?

16:01 -- 9. For Prandtl number less than unity, which is correct?

18:00 -- 10. The shape factor of a hemispherical body placed on a flat surface
with respect to itself is