About Radiation and its basic Concept And Stefan- Boltzmann Law

1. TITLE : RADIATIONS, BASIC CONCEPT OF
RADIATION , STEFAN BOLTZMANN LAW.
 SHIVAM PATEL 150110105031
 VATSAL PATEL 150110105032
 VYOM PATODIYA 150110105033
 KRISHNA PESHIVADIYA 150110105034
DEPARTMENT OF CHEMICAL ENGINEERING
G H PATEL COLLEGE OF ENGINEERING AND TECHNOLOGY
VALLABHVIDYA NAGAR- 388120
SUBJECT : PROCESS HEAT TRANSFER

2. OVERVIEW :-
 WHAT IS RADIATION
 CHARECTERISTIC OF RADIATION
 BASIC CONCEPT OF RADIATION
 THE STEFAN-BOLTZMANN LAW

3. WHAT IS RADIATION??
 RADIATION is the emission or transmission of
energy in the form of waves or particles through
space or through a material medium.
 Heat transfer through an evacuated can occur
only by radiation.

4. Characteristic of radiation:
 The electromagnetic waves are emitted as a result of vibrational
and rotational movement of molecular of the matter.
 The general phenomenon of radiation covers all wavelength from
shorter to longer.
 The frequency of wavelength is related by
C=λϝ

5.  Radiation can be reflected an absorption when the pass
through a media.
 All matter emits radiant energy and body at high
temperature emits at greater rate than low temperature.
 Heat exchange by radiation gets enhanced at elevated
temperature of the source and the surrounding.

6. BASIC CONCEPTS OF RADIATION FROM A
SURFACE
 Thermal radiation incident on a body tends to increase its temperature. Its
depend on the nature of material and its surface characteristic.
 The light falling on a body the small part of light is reflecting and mostly
absorbed.
 Absorption, reflection and transmission of incident radiation.

7.  Another important property of the surface of the
substance is its ability to emit radiation .
 Emission of radiation should not be confused with
reflection.
 Reflection may occur only when a surface receives
radiation, emission of radiation always occurs if the
temperature of the surface is above absolute zero.
 Reflection and emission of radiation depend upon the
surface characteristics.
 Emissivity of a surface is a measure of how good it is an
emitter.

8.  BLACK BODY:
 Its effective absorbers of radiation in the wavelength that are
encountered in heat transfer
 According to name black body is perfect absorber of radiation.
 α =1 , ρ=τ=0
 GREAY BODY:
 When a body absorbed a certain fixed percentages of radiations surface is called the
gray body.
 WHITE BODY:
 A body which is reflect all the accident thermal radiation is called white
body.
 It is known a specular body.
 Ρ=1 , α=τ=0.

9. THE STEFAN BOLTZMANN LAW
 Stefan–Boltzmann law, statement that the total radiant
heat energy emitted from a surface is proportional to the
fourth power of its absolute temperature.
 Determine the total emissive power of a black body by
Stefan Boltzmann law.

11.  Above equation is known as Stefan Boltzmann equation.
 Which allow us to calculate the total amount of wavelength
emitted in all possible directions by a black body.
 The value of Stefan Boltzmann constant 𝝈 has been determined
experimentally by a number of researchers.
 The accepted experimentally value is
𝝈=5.67*10
 The unit of Stefan Boltzmann constant is W/𝒎 𝟐 𝑲 𝟒.
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13. ENERGY VS WAVELENGTH GRAPH