Mass Transfer
Operations
Submitted to:
Prof. Madhu Agarwal
Name: Yogita
ID:2023uch1286
Batch: CH-2
Index
S.No Name of Experiment Date Signature
.
HEAT TRANSFER THROUGH FORCED
CONVECTION
Objective: To study forced convection heat transfer and determine the heat transfer coefficient
for air flowing over a heated surface.
Aim: To experimentally analyze forced convection heat transfer and compare the results with
theoretical correlations.
Introduction: Heat transfer can be defined as the transmission of energy from one region to another as a
result of temperature difference between them. There are three different modes of heat transfer; namely,
HEAT CONDUCTION : The property which allows the passage for heat energy, even though its parts
are not in motion relative to one another.
HEAT CONVECTION : The capacity of moving matter to carry heat energy by actual movement.
HEAT RADIATION : The property of matter to emit or to absorb different kinds of radiation by
electromagnetic waves. Out of these types of heat transfer the convective heat transfer which of our
present concern, divides into two catagories
NATURAL CONVECTION: If the motion of fluid is caused only due to difference in density resulting
from temperature gradients without the use of pump or fan, then the mechanism of heat transfer is known
as Natural or Free Convection.
FORCED CONVECTION:If the motion of fluid is induced by some external means such as a pump or
blower, then the heat transfer process is known as “Forced Convection”. The newtons law of cooling in
convective heat transfer is given by,
q = h A ΔT
Where, q = Heat transfer rate, in watts
A = Surface area of heat flow, in m2
ΔT = Overall temperature difference between the wall and fluid, in oC
h = Convection heat transfer co-efficient, in watts/m2 oC .( Heat Transfer: Principles and Applications by
Binay K. Dutta)
Description of Experimental Setup:
• A forced convection apparatus with a heated plate or tube.
• A fan to provide controlled airflow.
• Thermocouples to measure surface and air temperatures.
• An anemometer to measure air velocity.
• A voltage regulator and ammeter to control heating.
Utilities Required:
• 230V AC power supply
• Digital thermometer
• Blower/fan
• Variac (to regulate voltage)
Experimental Procedure:
1.Turned on the blower and set airflow to the desired velocity.
2. Adjusted the heating element to maintain a steady surface temperature.
3. Measured the inlet and outlet air temperatures using thermocouples.
4. Recorded the air velocity using an anemometer.
5. Measured the surface temperature of the heated object.
6. Computed the heat transfer coefficient using empirical correlations.
Observations and Calculations:
Air velocity (V) = ___ m/s
Length of test section=500mm
I.D. of test section=38mm
I.D. of test section=40mm
Orfice diameter=17mm
No of temperature sensors=6
Heat input (Q) =V*I
Convective heat transfer coefficient (h) = 0.045507W/m²K
Heat Transfer Area= πdL=59.690m2
q
Heat transfer coefficient=
A ( Ts−Ta )
Observation table:
V=90
(i) R=L-H=25mm
(ii) V=90V
time(min) T1(oC) T2(oC) T3(oC) T4(oC) T5(oC) T6(oC) Tavg(oC)
5 28.2 59 72.3 81.2 75.8 32.3 58.1333
10 27.1 57.6 77.6 76.7 77.1 31.4 57.9167
15 24 59.2 69.3 77 76 30.3 55.9667
20 34.2 56.9 80.1 78 75.7 31.3 59.3667
25 28.5 60.2 67.8 87.1 76.3 30.1 58.3333
30 23.4 57 74 81.3 75.1 32.1 57.15
35 28.4 57.4 68.8 74.6 74.7 29.5 55.5667
(iii) R=L-H=65mm
(iv) V=90V
time(min) T1(oC) T2(oC) T3(oC) T4(oC) T5(oC) T6(oC) Tavg(oC)
5 21.6 47.2 55.1 64.5 63.2 26.4 46.33333
10 20.9 46.4 54.5 60.4 62.2 26.8 45.2
15 26.4 45.6 54.3 64.2 61.9 25.5 46.31667
20 21.6 47.8 54.2 61.9 61.3 25.5 45.38333
25 22.7 44.7 54.1 70.6 62.1 25.2 46.56667
Nomenclature
h: Convective heat transfer coefficient (W/m²K)
q: Heat transfer rate (W)
Nu: Nusselt number
Re: Reynolds number
Precautions and Maintenance:
• Ensure proper insulation to minimize heat loss.
• Calibrate thermocouples before use.
• Avoid overheating the setup to prevent damage.
• Maintain a steady airflow for accurate results.
References:
( Heat Transfer: Principles and Applications by Binay K. Dutta)
Descussion: The experiment demonstrated forced convection heat transfer, where airflow
enhanced heat transfer from a heated surface. Higher airflow velocity increased heat transfer,
confirming the role of forced convection in practical applications like heat exchangers and
cooling systems. The results validated Newton’s law of cooling, and the experiment highlighted
the importance of maintaining steady airflow for accurate measurements. Future improvements
could include better insulation and more precise temperature measurement.
