EXPERIMENT NO.

09

HEAT TRANSFER THROUGH THICK SLAB

AIM: To find out thermal resistance and total conductivity of thick slab.

DESCRIPTION:
The apparatus consists of central heater sandwichced between two
slabs one is
Aluminum other side asbestos sheet.
Electronics Dimmer knob is
provided to vary heat input
of heaters and it is measurcd by a digital voltmeter and
ammeter. Thermocouple is embedded
between interfaces of slab & outside
surface. A Digital
temperature indicator is provided to
measure
temperature at various points

SPECIFICATION:
1. Electronics dimmer stat open
type, 230V, 0-2amp single
2.
phase.
Digital temperature indicator.
3. Slab diameter 150mm.
4. Thickness of M.S =
25mm.

PROCEDURE:
1. Start the main switch.

2. By adjusting the heat control knob

give heat input. (say 100v)
3. Take the readings of all (4) thermocouple at an interval
of 30mm until
state. the final steady
4. Note down the readings in observation table.
5. Repeat the procedure for different heat
input.
6. Make dimmer knob to 'zero position and then put main switch of,

Thermal Science and Engineering.UVCE

 Lab Manual(
Engineering
Thermal
Advanee

OBSERVATION TABLE: Ts
12
Ti oC
meter
SL No AC watt
readings in watts
C
(w)
63.2. 682 55-954:3
80
185
112-912 9 84.2
TEMPERATURE POINTS.
1,2: M.S. Slab inner surface
3,4: M.S. Slab outer surface.

PRECATUIONS:
1. Keep the heat control knob to, zero before starting the experiment
2. While removing plates do not disturb thermocouples.
3. Use the selector switch knob and heat control knob
gently.

CALCULATIONSS:
Read the heatsupplied Q (W/ 2 Watts (in S.I units) For calculating the thermal
=

conductivity of composite walls, it is assumed that due to large diameter of the

plates, Heat
flowing through central portion is unidirectional i.e., axial flow. Thus for
calculating central
half diameter area where unidirectional flow is assumed is considered.
Accordingly,
thermocouples are fixed at close to centre of the plates.

1. Heat input

Watts
R

2. TA- -
632t68.2 65-7 .°C
2
TB - 55.7t543
************ . °C

2
3. Area of slab

A E-_1 (or075) = y.41 78xia2

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Engineering.UVCE
 Manual(18TSILOI)

Iab
Advance Thermal Engine
eering

where d is diameter of slab (effective diameter =(150/2))mm

4. Thermal resistance of slab(RR)

R=TAg7Bang_657-+55: 3.02...C/W
. ***
Q

5. Thermal
condhcticity (K)

KAC
QxT O
235..W/mk
XO O25
A(TAavg+TBavg) 4198no 657-5s)*

where t is thickness of slab

et 80
185 W
We
RESULT
Thermal resistance of slab(R)..... 3.02 °C/W
iO5.75 'C/uw
..

Thermal conductivity (K).. .. . W/mk. 18.46 Wlmk

Justification is that higher the thermal conductivity of an insulation material means lower
thermal resistance.

185 wlattse

4, = 1 8 S 9.5 tWtfs
=u9.95
R aygTt2 1l?-1+137
-

2 2

TBwgtly =94t872 916 =

3, 2
2
=4.4178 xIs3?
4
, R TArst BwS
= 105.775 cI
425x00RS
18y6w/mk
.

6K xt .9/X6"L)}9.9s-91.
AT TAosns

UVCE
Engineering,
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Thermal
 EXPERIMENT NO, 07
EXCHANGER
COUNTER FLOY HEAT

and the:
main objective of this experiment is to study
compare
flow heat exchanger
Temperature distribution in the counter
Heat transfer rate in the flow heat exchanger.
counter
flow heat cxchanger.
Overall heat transfer coefficient of the counter
counter flow heat exchanger.
To obtain the effectiveness of the given

TION:
fluid to another. Common exampl
devices in which heat is transferred from
one
angers are
car, the condenser at the back
of a domestic refrigerator and the
angers are the radiator of a
thermal power plant.

classified in three categories:

angers are
Transfer type
Storage type
Direct contact type.

in whieh both fluids pass simultaneously through the device

=r tvpe of heat exchanger is one in practice most of the heat exchangers used are transfer
walls.
ansferred through separating

sfer type heat

classified according to flow arrangements as,
exchangers a e futher

both the fluids flow in the same direction.

. PARALLEL FLOW in which
which both the fluids flow in the opposite direction.
COUNTER FLOWin other.
which they flow at right angles to each
3.CROSS FLOW in
 MuE O.7SX0.colxlos= 5.2xIOsS
5
Mc= I222 Xo-00lx1e 8.1466 xo
I5
ABULAR COLUMN:

arameters to be noted down Counter flow

Quantity of hot water collected, M, (kgs)
5xio
Quantity of cold water collected, M. (kg/s) 8.1166xl0
nlet temperature of heat water, Thi °C
33.6
nlet temperature of cold water, Te °C 23
Outlet temperature of hot water, Tho °C
30
Outlet temperature of cold water, Tco °C
4-5
P h P e 4 8 2 123/kaC
CALCULATIONS:
Mh.Cph. CThg-The
-5.2Iy.182 336-30)
1. The Heat transfer rate(q):
4 0. 7828 J/

qh = heat transfer rate from the hot

MGe:(Teo- Ter)
water. qh Ma Cph ( Thi-Tho) = B.HC6 xloX4182)(245-23
h 782.8 _watts , 5 o 3 Js]
qe= heat transfer rate to the cold abs oneiS

water q= Mc Cpccor lai)se 9,vtvc r0 t828+ 0.5Ilo3 io varyh e

Stlh03 watts
qc
0616918 ET/ o u p l ei s e r

ator is pro

e ga646- ulatts
T=
Th-Teo=tyE-22=10-6c
4555
2. LMTD (Logarithmic mean temperature difference): AT= ho phase.

AT ThrTo
LMTD : AT-AT
AT
OC
AT2 Tm
AO-AD2
temperature difference (LMTD)
T0.65S-
=

mean
Logarithmic
In)
A-2
nput. (sayy 10

C
T 33 6-24-5
LMTDF an interval o
T 30- ?3

1Tm8.O7c
ble.

i n p u t .

down
the
i diftei
then
put
m
for
Note and
4. p r o c e d u r e

position
Ncneat t h e 'zero
t p
 AR- TIx10 xIo2- 0 62Sm2
Ap TX12xI02 = 0-075m2
3. Overall heat transfer
coefficient (U:
q-UA ATm
U=q/A
Where
ATm
A= area based on inner tube (A) or outer tube
A
TmLogarithmic mean temperature difference(A.). (m)
(LMTD) (°C)
qheat transfer rate (Watts or kJ/s)
6T
Uy? A ATm Oe0623)X8-04

Us 276-6 1 w
U based
m
on AF TDL=
O 0628 m Ur 647
O-075xS.0+
Uro 1070J3r
m
Ui- 276 64 W/m°C
Uro based on A,= rDot= O»Ot5
81466xtox-182

e 0340 6

heat exchanger can be calculated by using the

4. The effectiveness (E) of the
expression Ch M, *Ph
TE
E = S2moX4.182
bla
xe
Cmn C=02/4464
E En
2h5- 230.3406 = 22.16
33-6-23
0 217 6
WE
Counter flow

Calculated parameters 647

Watts)
transfer rate, q( 8 0F
Heat difference (°C)
AP
Logarithmic
mean
temperature

Ai
.Ui(W/m*°C) 12766
based o n regu
transfer
coefficient

(W/m°C) 1O70 3
heat Uo
Overall based o n A,
2216
c o e f f i c i e n t

transfer
heat
Overall

Effectiveness, E
 EXPERIMENT NO. 06
PARALLEL FLOW HEAT EXCHANGER
ive of this experiment is to
re distribution in a study and compare the:
parallel flow heat
er rate in a parallel flow heat exchanger.
at transfer coefficient of the exchanger.
parallel flow heat
exchanger.
he effectiveness of the given
parallel flow heat exchanger.

evices in which heat is transferred from one fluid

e radiator of a
to another. Common ex
car, the condenser at the back of
wer plant.
a
domestic refrigerator ar
an
.

lassified in three categories:

pe *

e **.*

tact type.
t exchanger is one in which both fluids pass simultaneously through the de
ugh separating walls. In practice most of the heat exchangers used are teoan
 the flow rate on hot water side, betwcen the ranges of 1.5 to 4 LMin
Adjust
Adjust the Now rate on cold water side, between the ranges of 3 to 8 LMin.

Keeping the flow rates same, wait till the steady state conditions are reached.

Record the temperatures on hot water and cold water side and also the flow raies accurately

SPECIFICATIONS:
Toking dinuity 1 C uC
. Material of the inner tube
ft000k
Brass. D, = diameter of inner tube elor= O.cclm m3

D, mm vd. PenJ nak :o-0ol m

Sec
mas fard nate =
tmalen x Vet. Hes
2. rote
Material of the outer tube Cast
M 0 001x0 5 x lo
iron. D, diameter of the outer
=
tube.
Do mm
Mh 3-333 x10 kyls
Parameters to be noted down
3. Length of Parallel flow
heat exchanger L= m

Quantity of hot water collected, M» (kg/s)

TABULAR cOLUMN: 2
3.333Xoa/
Quantity of cold water collected, M. (kg/s)
8.333 xIo sls
Inlet temperature of heat water, Th °C
34-1
Inlet temperature of cold water, T, °C

8
Outlet temperature of hot water, Tho °C

30.4
Outlet temperature of cold water, T°C
24.5
M 0 o0l xl:25 x 10
15
8 - 3 33 X10 e
 Cph 4.182 kJ/C

CALCULATIONS:.
M,ph. Ty-Ta.)
I. Heat transfer rate
3.333x1o4.82)C3He1-304)
h heat ransfer rate from the hot water.
qh M, Cph( TrTho)
0.SI7 Watts
(pe: CE-T:
q heat uransfer rate to the cold water 8.933 Xiö4.1822Y5-228)
4 M,C(Tu-To)
4 05121 Watts
Where Mh= the mass flow rate of hot water ,th o.5157+05924
(kg/s)
M the mass flow rate of water cold (kg/s)
2
Cphspecific heat of hot water (kJ/kg°C) =
9 , 0.55yo6Asls
Cpe specific heat of cold water (kJ/kg°C)=
The mean heat transfer rate, q (qh t q)/2=
=

kJ/s or Watts

2. The LMTD (Logarithmic mean temperature difference)

ATThrTa
AT T,= Th-Te; 34.1 -238= l1:3 c
AT= ThorTco
AT2 C 6 Tae Tco 30.4 -24.5 5.1c
=

LMTD T- A
Ai-A
Logarithmic mean temperature difference (LMTD)

In InT)
DTm5.
1 S. 320
0-619

LMTD 8.320 _C At TirDrxl 3

3. The Overall heat transfer coeflicient (U): = 3.11x10XIO 2
q-UAAT
U= q/A ATm
Where A = area based on inner tube (A,)or outer tube (A,). (m*)
A 0 0628
A Tm Logarithmic mean temperature difference (°C)
q= heat transfer rate (watts or KJ/s)

U,, based on A, nDL

O.0628 _m
 ed
0.55406 Xi03
U Ap XDTm O.0628xg.3209
Uv 106o 359 w
MC
Un
Ap 7 xxL
2 075 m2
1060.359 W/mC 3-14x 12xiox = 0.

Uro based on A = TDL=

Uro
Uro 0:55 4o6r1
AoDlm 01537 Ao1
Uro 88y,3 36 W
Oo153_m
Uro

C 2
88.336 _w/m2c
C 8 3 3 3KiO x4182
0:34S4
W&O3 93
Ch* mhx P
1. The effectiveness (e) of the heat exchanger
2
43933 10X4-82
E To-T
T-T
To-Te x Ce
TAT Cnen
E
c 4.5-228 O0:3484 0 376
LTS: The calculated results áre tabulated as shown below:
341-22.8 O39 3 37-6
ulated parameters Parallel flow
transfer rate, q( Watts)
O.55 ho 6xro
ithmic mean temperature difference (C)
8.32 0
ll heat transfer coefficient based on Aj .Ui (W/m*°C)
l heat transfer coefficient based on A, Uo (W/m*°C)
l060.351
884.336
veness, E
37.6