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B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2013
Fifth Semete!
Mech"#ic"$ E#%i#ee!i#%
&ME11'01 ( )EAT AND MASS TRANSFER
Time* Th!ee h+! M"-imm* 100M"!
)e"t "# m" t!"#fe! t"$e, te"m t"$e "!e e!mitte f+! e
A#4e! A55 6eti+#
7ART A ( 10 82 9 20 M"!
1. State Fourier law of heat conduction
2. Define fin efficiency and effectiveness.
3. Distinguish between free and forced convection.
4. Define Reynolds number (Re and !randtl number (!r.
". #ndicate the difference between boiling and condensation.
$. Discuss the advantage of %&' method over the )&D
method.
*. State the Stefan+,olt-mann and ien/s dis0lacement laws of
radiation.
. Discuss the radiation characteristics of carbon dioide and
water va0our.
. State Fic/s law of diffusion. 5ive its e0ression.
16. Define e7uimolar counter diffusion.
7ART B ( ' 81: 9 ;0 M"!
11. (a (i 8btain an e0ression for the general heat conduction
e7uation in 9artesian
coordinates. (12
(ii :0lain briefly the conce0t of critical thicness of
insulation and state any two
a00lications of the same. (4
O!
(b (i ith neat setches; e0lain the different fin 0rofiles (4
(ii m? 2 cm in diameter and 26 cm long 0rotrudes from
a wall which is maintained at 366@9. &he end of the rod is
insulated and the surface of the rod is
e0osed to air at 36@9. &he heat transfer coefficient between
the rodAs surface and air is 16
w>m2?. 9alculate the heat lost by the rod and the tem0erature
of the rod at a distance of 16 cm
from the wall. (12
12. (a (i s .if the 0late
is 1m wide and the tem0erature &w = *"6c .calculate the
following at a location of 1m from the
leading edge.(i Bydrodynamic boundary layer thicness;(ii ocal
friction coefficient;(iii
&hermal boundary layer thicness;(iv ocal heat transfer
coefficient. (
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(b (i < large vertical 0late " m high is maintained at 166@9
and e0osed to air at 36@9
9alculate the convection heat transfer coefficient. (
(ii 9ylindrical cans of 1"6 mm length and $" mm diameter are to
be cooled from an
initial tem0erature of 26@9 by 0lacing them in a cooler
containing air at a tem0erature of 1@9 and
a 0ressure of 1 bar. Determine the cooling rates when the cans
are e0t in hori-ontal and vertical
0ositions. (
13. (a ater is to be boiled at atmos0heric 0ressure in a
mechanically 0olished stainless steel
0an 0laced on to0 of a heating unit. &he inner surface of
the bottom of the 0an is maintained at
l6@9. &he diameter of the bottom of the 0an is 36 cm. m2?
for an echanger surface area of 2"m2; 9alculate the
eit tem0erature of air and water. ($
14. (a Determine the view factor (F1+4 for the figure shown
below.
O!
(b < 0i0e of diameter 36cm; carrying steam runs in a large
room and is e0osed to air at a
tem0erature of 2"6c.the surface tem0erature of the 0i0e is 366
6c.calculate the loss of heat to a
surrounding 0er meter length of 0i0e due to thermal radiation.
&he emissivity of the 0i0e surface
is 6..what would be the loss of heat due to radiation of the
0i0e is enclosed in a ""cm diameter
bric of emissivity 6.1.
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1". (a (i Define the Schmidt ;Sherwood and ewis numbers. hat is
the 0hysical significance
of eachC ($
(ii < vessel contains binary miture of 82and %2with 0artial
0ressures in the ratio 6.21
and 6.* at 1"@9. &he total 0ressure of the miture is 1.1
bar. 9alculate the following
(1 )olar concentrations;
(2 )ass densities;
(3 )ass fractions and
(4 )olar fractions of each s0ecies. (16
O!
(b (i Dry air at 26@9 (= 1.2 g>m3; v = 1" l6+$m2>s; D =
4.2 l6+"m2>s flows over a flat
0late of length "6 cm which is covered with a thin layer of
water at a velocity of 1 m>s. :stimate
the local mass transfer coefficient at a distance of 16 cm from
the leading edge and the average
mass transfer coefficient. (16
(ii Discuss the analogy between heat and mass transfer. ($
