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Experiment 2
Determination of the
Thermal conductivity of th
Gown Liquid
AIM : To determine thermal conductivity of a liquid(glycerol).
APPARATUS REQUIRED : Water supply,5 Lt/ min (approx.), drain ,
Electricity supply : 1 phase , 220 V AC, 2 Amp.
DESCRIPTION : The apparatus is based on well - established "guarded hot plate "method. It is a steady
state absolute method suitable for materials, which can be fixed between two parallel plates .
For thermal conductivity of liquids using Fourier's law, the heat flow through the liquid from'hot fluid to
cold fluid is the heat transfer through conductive fluid medium .
Fourier equation:
Q = -KA(T2-T1)/Ax
Fourier law for the case of liquid .
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At steady state, the average face temperature are recorded (T* and Tc) along with the rate o teat
transfer(Q). Knowing heat transfer and thickness of sample (Ax) across which the heat trail, er takes
place , the thermal conductivity of the sample can be calculated using fourier s law of heat conduction.
C* = KA* AT/Ax
^KAUK-TJ/Ax
Heat transfer area = A* (area perpendicular to direction of heat flow’)
FORMULAE:
1-
Q=KA(TJ-T1)
2.
K = QAx/A(Th-TJ
PROCEDURE:
l.Fill liquid cell withthesample liquid (glycerol).Liquid filling should be continued till there is complete
removal of air and also liquid^lycerol comes out of the outlet port.Close the outlet port followed by
inlet port.
2-Allow' cold waterto flowthroughthecold - water inlet.
3.Start the electric heater.to heatthe hot plate .
4 .Adjust the cold-water flow rate such that there is no appreciable change the outlet temperature of
cold water.
5.Go on recording the sensor readings on the hot side as well as on cold side , and once steady state is
achieved , record three sensor readings (TM , Th2, Th3) on hot side and three sensor readings on cold side
(Li, Td, Tc3) on cold side.
OBSREVATION AND CALCULATIONS:
S.NO.
V
1
W
THl
Thi
Th3
T“
1 T«
Tea
Cold
Water
flow rate
I
IK
I sr
1
J_____ )
Recod the following at steady state
Sample liquid:
Voltmeter reading
Ammeter reading
=
=
V
A
Hot face average temperature(TH) =(THi+Th2+TH3)/3
Cold face temperature(Tc) =(Tcl+TC2+TC3)/3
1. Use the stabilize A.C single phase supply only.
2. Voltage to heater starts and increases slowly.
3. Keep all assembly undisturbed .
4. Never run the apparatus if power supply is less than 180 volts and above 240 volts.
S.Operate the selector switch of temperature indicator gently .
7,Testing liquid should be fully filled .