Heat & Mass Transfer
Experiment # 1
Title: Radiant Heat Transfer
Submitted by:
Usama-Bin-Imran
Roll No. :
18 – MCE – 29
Semester:
7th
Submitted to:
Sir Faraz Shabbir
Department of Mechanical Engineering
NFC Institute of Engineering and Fertilizer Research,
Faisalabad
Experiment#1
Radiant Heat Transfer
Objective:
To show the energy radiant at any angle with a surface is equal to normal radiation multiplied
by the cosine of the angle between the direction of radiation and normal to the surface.
Apparatus:

Radiant Heat Transfer and exchange apparatus.
Main Parts

Heat Source

Radiation detector

Temperature Sensors

Radiometer output unit

Main digital Control panel (H111)
Introduction:
Thermal radiation is a mode of heat transfer, differs significantly from the other two modes,
namely conduction and convection. The fact that radiant energy transfer occurs across a
vacuum is often disturbing to students unless the theory relating to properties of
electromagnetic waves has been presented.
Theory:
Radiation Heat Transfer:
Thermal radiation is electromagnetic radiation generated by the thermal motion of charged
particles in matter. All matter with a temperature greater than absolute zero emits thermal
radiation. When the temperature of the body is greater than absolute zero, interatomic
collisions cause the kinetic energy of the atoms or molecules to change. All bodies radiate
energy in the form of photons moving in a random direction, with random phase and
frequency. When radiated photons reach another surface, they may be absorbed, reflected or
transmitted
Lux meter:
A lux meter is a device for measuring brightness. It specifically measures the intensity with
which the brightness appears to the human eye. This is different than measurements of the
actual light energy produced by or reflected from an object or light source.
Lux:
The lux is a unit of measurement of brightness, or more accurately, illuminance. It ultimately
derives from the candela, the standard unit of measurement for the power of light.
Given the Illuminance Formula (or Cosine Law of Illuminance) is:
1
E=𝑑2 cos θ
Where;
E= illuminance (or density of luminous flux) reaching a surface (1m/m2 or lux)
I= Luminous intensity or strength of a light source (candle power or candela, cd)
d = Distance between light source and surface (m).
Procedure:

First of all set the apparatus according to our requirements.

Then we place the light source and lux meter in front of each other i-e 0-degree.

We measure distance between lux meter and light meter equals to 200mm.

Increase the angular displacement by 10-drgree increment clockwise.

We repeat this process again and again till we reach 90-degree.

Now rotate lux meter in anticlockwise direction through 90-degree form center.
Observation:
Sr.#
Angle of
displacement(θ)
1
90
-10
2
80
-20
3
70
-30
4
60
-40
5
50
-50
6
40
-60
7
30
-70
8
20
-80
9
10
-90
10
0
Graph:
Lux Meter
Reading
Angle of
displacement(θ)
Lux Meter
Reading
Conclusion: