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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 8 2 9 20 M"!

1. What is Poisson's equation and Laplace equation for heat flow?

2. What do you understand by lumped capacity analysis?

3. What is overall heat transfer coefficient?

!. "ow does laminar flow differ from turbulent flow?

#. $efine %ilm wise condensation and $rop wise condensation.

&. What are the types of heat echan(er?

). *tate Planc+,s distribution law and Wien's distribution law.

-. What is radiosity /0 and irradiation?

. $efine the followin( i0 ass concentration ii0 olar concentration

14. $efine %ourier number 5 6iot number for mass transfer.

7ART B ( ' 81: 9 ;0 M"!

11. a0 7 furnace wall consists of three layers. 8he inner layer of 14 cm thic+ness is made of

firebric+ (k 91.4! W:m;0. 8he intermediate layer of 2# cm thic+ness is made of masonry bric+

+ 9 4.& W:m;0 followed by a # cm thic+ concrete wall + 9 1.3) W:m;0. When the furnace is

in continuous operation the inner surface of the furnace is at -44=p94.--+:+(

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12. a0 i0 7ir at !44c flows over a tube with a velocity of 34m:s. the tube surface temperature is

1244c> calculate the heat transfer coefficient for the followin( thic+ness.1.8ube could be square

with a side of &cm.2.8ube is circular cylinder of diameter &cm. -0

ii0 7ir at 244 +Pa and 244 estimate the dra( force actin( on the plate. 140

ii0 $efine Beynolds> Cusselt and Prandtl numbers. &0

13. a0 i0 $ry saturated steam at a pressure of 2.!# bar condenses on the surface of a vertical

tube of hei(ht 1 m. 8he tube surface temperature is +ept at 11)

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1!. a0 i0 =alculate the net radiant heat echan(e per m 2area for two lar(e parallel plates at

temperature of !2)4c and 2)4c respectively. H hot plate0 9 4. and H cold plate0 9 4.&.if a polished

aluminium shield is placed between them> find the percenta(e of reduction in the heat transfer

H shield09 4.!. 140

ii0 *tate and prove the followin( laws

&0 10 ;irchhoff,s law of radiation

20 *tefan 6oltFmann law.

O!

b0 8wo parallel plates of siFe 1m I 1m are spaced 4.#m apart are located in a very lar(e

room> the walls of which are maintained at a temperature of 2)4c.one plate is maintained at 444c

and the other at !444c their emissivities are 4.2 and 4.# respectively. Af the plates echan(e heat

between themselves and surroundin(s> find the neat heat transfer to each plate and to the room.

=onsider only the plate surfaces facin( each other. 1&01#. a0 $iscuss briefly the followin(

i0 %ic+,s law of diffusion #0

ii0 Dquimolar counter diffusion #0

iii0 Dvaporation process in the atmosphere &0

O!

b0 i0 Ey(en at 2#4c and pressure of 2 bar is flowin( throu(h the rubber pipe of inside

diameter 2#mm and wall thic+ness 2.#mm .the diffusivity of o 2 throu(h rubber is 4.2114 m2:s

and the solubility of o2 in rubber is 3.12143+( mole:m3bar.find the loss of o2by diffusion per

metre len(th of pipe. -0

ii0 $ry air at 2)4c and 1 atm flows over a wet flat plate #4 cm lon( at a velocity of #4

m:s. =alculate the mass transfer coefficient of water vapour in air at the end of the plate. 8a+e

the diffusion coefficient of water vapour in air is $769 4.2& I 14!m2:s. -0