Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 5th Semester (Fifth Semester) 2015-2016 Heat Mass Transfer Eme 504 Question Paper
EME-504
(Following Paper 1]) and Roll No. to be filled-in your
Answer Book)
Roll No.
? Iinch.
(SEM. V) THEORY EXAM. 2015-16
HEAT & MASS TRANSFER (EME-504)
[Time:3 hours] [MaximumMarksleO]
SECTION?A
Q.1 Attempt all parts. All part carry equal marks. Write
answer of each part in short.
(2x10=20)
(a) How do thermal conductivities 0f gases and non-
metals vary with temperature?
(b) Derive the expressiOn for logarithmic mean area
for the hollow cylinder.
(0) Discuss the physical signi?cance of effectiveness.
((1) What do you understand by lumped system, explain
it with suitable example?
(6) Thermal time constant and response of
temperature measuring instrument.
23500 (1) ,
P.T.O.
Q3 What is thermometer well, describe it with neat sketch
? ( 0 Explain one-seventh power law over a ?at plate. and prove that the temperatue measured by a thermomter
(g) Write down the assumptions which are made for well ls not a true temperature 0f ?u?d'
the analysis of heat ?ow through the ?n. Q4 What do you mean by radiation shield? Derive the
(h) Discuss the follwing. ? ' expression of net heat transfer rate for a systetn-oftwo
~ parallel plates separated by n-shlelds of exmisswlty?s
(i) Nusseltnumber and its physical signi?cance. 6 31,6 s2,e s3 ........... 6 Sn.
(1?) . Grasho?"s number and its physical signi?cance Q.5 Give the detail classi?cation of heat exchanger. Write
down the governing paranieters for analysis of heat
(i) Write short note on fouling or scaling. ,
exchanger. Also explain the compact heat exchanger with
(j) A gray diffuse opaque surface ( a #08) is at 100 neat sketch.
OC andteceives an radiation 1000 W/mz'. If the . _ . . .
surface area is 0.1 m1. Calculate: . # Q.6 Explam the followmg 1n detalls.
(i) Radiosity ofthe surface. (i.) Intensity of radiation.
(ii) Net radiation heat transfer rate from the (ii') Shap e factor algebra, facts and p rop eraties.
surface. Q.7 Steam in the condenser of .a power plant is to be
(iii) Calculate above quantities if the surface is I condensed atatemperature 0f30 QC With cooling water
? black. ' from a nearby lake, which enters the tubes of the
condenser at 14 OC and leaves at 22 ?C. The surface'area
SECTION'B of the tubes is 45 m2 an the overall heat transfer
coef?cient is 2100 W/m2 ?C. Determine the mass ?ow
Note: Attempt any ?ve questions from this section. . -
rate of the cooling water needed and the rate of
(10x5=50) , , .
? condensatlon of the steam 1n the condenser. Heat of
Q2. What do you mean by modes of heat transfer? Describe vaporization of water at 30?C 243 1 kJ/kg. and Cp=4184 '
its governing laws in detail. Also describe the case of J/kg 0C. 7
combined heat transfer by required expression.
23500 (3) P.T.O.
23500 (2) EME-504
Q.8 Determine the coef?cient of heat transfer by free
convection and maximum current density for a nichrom
wire 0.5 mm in diameter. The surface of th ewire is
maintained at 300 ?C. The wire is exposed to still air at
20 0C and resistance per meter length of the wire is 6? Q/
m Use relation: Nu=l .1 8 (Gr Pr)?.
Use properaties of air at 160 ?C-
Kf= 0.0361 W/m K, u=30.35x 10" m2 /s, Pr=0.68?1
Consider a diffuse circular disk of 3diameter D and area
Ar and a plane diffuse surafaces of area AJ<
the center of AI
Q9
Obtaiq the following expression for the view factor ,
DZ
F: , .
? D?+L?
SECTION -C
Attempt any two questions from this section. (15x2=30)
,Q.10 (a) Derive the general heat conduction equation in
C artesian co-ordinate for homogenesous and
isotropic material.
23500 (4) EME-504
0.11 (a)
(b) A wall is constructed of servral layers. The ?rst
layer consists of bricks (k=0.66 w/m k), 25 cm
thick, the second layer is 2.5 cm thick mortar
(k=0.7 w/m k), the third layer 10 cm thick
limestone (k=0.66 w/m k)and outer layer of 1.25
cm thick p1aster(k=0.7 w/mk). The heat transfer
co-ef?cient on interior and exterior of the wall
?uid layers are 5.8 w/mzk and 11.6 w/mzk,
respectively. Find:
(i) Overall heat transfer co-ef?cient. (ii) Overall
thermal resistance per m2 . (iii) Rate of heat transfr
per m2. if the interior of the room at 26 0C while
outer air is at 7 0C, (iv) Temperature at thejunction
between mortar and limestone.
Write down the name of some common types of
?n with neat sketch. Also derive the expression for
heat dissipation through rectangular ?n which is
in?nitely long.
(b) A Copper pipe carrying refrigerant at -20 ?C is 10
23500
mm in outer diameter and is exposed to ambient at
25 ?C with convective coef?cient of 50 W/m2.k. It
is proposed to apply the insulation of material
having thermal conductivity of 0.5 W/ mk.
Determine the thickness beyond which the heat gain
will be reduced. Calculate the heat losses for 2.5
mm, 7.5 mm, and 15 mm thick layer of insulation
' overI m length.
(5) P.T.O.
Q-12(a)
(b)
23500
Describe the boundary layer thickness and derive
, the expression for energy thickness.
An iron sphere of diameter 5 cm is initially at a
unifrom temprature of 225?C. It is suddely
exposed to an ambient at 25 ?C with convection
coef?cient of 500 W/mzk.
(i) Calculate the centre temperature 2 minute
after the start of exposure.
(ii) Calculate thetemperature'at the depth of 1
cm from .ther-rs-urface after 2 minute of
exposure. '
"(iii) Calculate the enegry removed from the
sphere during this period. Take thermo-
physical properties of iron plate:
k=60 W/mK, p=7850kg/m3 ,C=460 J/Kg,
a = 1.63:10'5 mz/s
?x??
(6) EME-504
This post was last modified on 29 January 2020