IMPACT COLLEGE OF ENGINEERING AND APPLIED SCIENCES
SAHAKARA NAGAR SOUTH, BENGALURU - 560092
DEPARTMENT OF MECHANICAL ENGINEERING
HEAT TRANSFER LAB
THERMAL CONDUCTIVITY OF METAL BAR
OBJECTIVE: To determine the thermal conductivity of metal rod at different
section for given heat input.
THEORY:
From Fourier’s law of heat conduction
Q = - k A dT
dx
where, Q = Rate of heat conducted, W
A = Area of heat transfer, m²
k = Thermal conductivity of the material, W/m-K
dT/dx = Temperature gradient
dT = Temperature difference
dx = distance between the thermocouple
Thermal conductivity is a property of the material and may be defined as the
amount of heat conducted per unit time through unit area when a temperature
difference of unit degree is maintained across unit thickness.
DESCRIPTION OF THE APPARATUS:
Saleha Nadeem B.E., M. Tech (Thermal) Asst. prof., Dept. of ME, ICEAS.
IMPACT COLLEGE OF ENGINEERING AND APPLIED SCIENCES
SAHAKARA NAGAR SOUTH, BENGALURU - 560092
DEPARTMENT OF MECHANICAL ENGINEERING
The apparatus consists of a Brass rod, one end of which is heated by an electric
heating coil while the other end projects into the cooling water jacket. The rod is
insulated to minimize the radiation and convection loss from the surface of the rod and
thus ensure nearly constant temperature gradient throughout the length of the rod. The
temperature of the rod is measured at four different locations. The heater is provided
with a variance for controlling the heat input. Water is circulated through the jacket and
its flow rate and temperature rise can be measured.
DESCRIPTION:
1-Heater Coil 400W.
2-Specimen (________) ____ mm long and ____ mm diameter.
3-Insulator
4-water.
THERMOCOUPLE DETAILS:
T1, T2, T3, T4, temp along the length of test specimen
T5-water inlet temperature
T6-water outlet temperature
PROCEDURE:
1. Bring the selector switch to zero gently.
2. Bring the variance to zero position, open the valve at inlet of cooling water jacket
and maintain constant water flow rate.
3. Allow sufficient time for the apparatus to reach steady state.
4. Take readings of voltmeter and ammeter.
5. Note the temperatures along the length of the specimen rod at 4 different
locations.
6. Note down the inlet & outlet temperatures of cooling water and measure the
flow rate of water.
7. Repeat the experiment for different heat inputs by slowly rotating the knob of
variance in clockwise direction.
Saleha Nadeem B.E., M. Tech (Thermal) Asst. prof., Dept. of ME, ICEAS.
IMPACT COLLEGE OF ENGINEERING AND APPLIED SCIENCES
SAHAKARA NAGAR SOUTH, BENGALURU - 560092
DEPARTMENT OF MECHANICAL ENGINEERING
TABULAR COLUMN:
Voltmeter Ammet Heat Water temp Volume
Reading er input (0C) flow rate of
‘V’ Reading Q=V Metal rod thermocouple water,
(volt) I xI reading Inlet Outle V cc/sec
(Amps) (W) (0C) t
T1 T2 T3 T4 T5 T6
DATA SHEET
SPECIFICATIONS:
Specimen material : Brass rod
Size of the Specimen : ____ mm, ____mm long
Voltmeter : Digital type, 0-300volt, AC
Ammeter : Digital type, 0-5amp, AC
Dimmer : 0-230v, 0-2 A
Thermocouple used : 6 nos.
Temperature indicator : Digital type, 0-900° C.
SPECIMEN CALCULATIONS:
Plot the variation of temperature along the length of the rod. From the graph,
obtain dT/dx, which is the slope of the straight line passing through/near to the points
in the graph. Assuming no heat loss, heat conducted through the rod = heat carried
away by the cooling water
-k x A x dT/dx = mf Cp (T6 – T5)
Saleha Nadeem B.E., M. Tech (Thermal) Asst. prof., Dept. of ME, ICEAS.
IMPACT COLLEGE OF ENGINEERING AND APPLIED SCIENCES
SAHAKARA NAGAR SOUTH, BENGALURU - 560092
DEPARTMENT OF MECHANICAL ENGINEERING
Where, ‘k’ = Thermal conductivity of metal rod, (W/m-K)
‘A’ = Cross sectional area of metal rod = πd²/4 (m²)
‘d’ = Diameter of the specimen = 20 mm
‘Cp’ = Specific heat of water = 4187 J/kg-K
‘𝑚𝑓 ’= Mass flow rate of water in kg/sec.=v×10−3
dT
=slope of T-x graph 0c/m.
dx
Thus, the thermal conductivity ‘k’ of metal rod can be evaluated.
𝑚𝑓 𝐶𝑝 (𝑇6 −𝑇5 )
-k = 𝑑𝑇 =……………W/m-K
𝐴
𝑑𝑋
RESULT:
Thermal conductivity of given metal rod is found to be …………… W/m-K.
Saleha Nadeem B.E., M. Tech (Thermal) Asst. prof., Dept. of ME, ICEAS.
