To determine the Emissivity of a surface in a closed radioactive heat transfer environment.
S. No. | Heat Input (Q) WattsV/1/Q = V * I | Temperature of test plate (°C)/T1/T2/T3 | Temperature of black Body (°C)/T5//T6/T7 | Chamber temperature (°C) Ta = T4 | Emissivity |
1 | |||||
2 | |||||
3 | |||||
4 | |||||
5 |
Stefan's Boltzmann's Law
Heat transfer through `radiation i.e
Emissive Power (E) = £ A σ(T_{1}^{4} - T_{2}^{4})
Heat Input (q) = V* I Watts
Average of Test Plate Surface temperature (T_{tp}) = (T1+T2+T3) /3°C _______ _ K
Average of Black Plate Surface temperature (T_{bp}) = ( T5+T6+T7) /3°C _____ _______ K
Surface Area (A) = π D ^{2}/ 4 in m ^{4}
Emissive Power of the black Plate (E_{bp}) = £ σ (T_{bp}^{4}- T^{4})
Emissive Power of the test Plate (E_{tp})= = £ T_{tp atp} σ (T_{tp}^{4}-T_{a}^{4})
Equating the emissive power of a both Plates as it reaches a steady State.
Ebp = Etp
£_{bp abp} σ (T_{bp}^{4}-T_{a}^{4})= £ σ(T_{tp}^{4}-T_{a}^{4})
Since Abp = Atp
£_{tp} = £_{bp}(T_{bp}^{4}-T_{a}^{4})/(T_{bp}^{4}-T_{a}^{4})
Where
A - Area of the Plate in m ^{2}
T_{tp}- Teat Plate surface temperature in K
T_{bp}- Black Plate surface temperature in K
T_{a}- Chamber temperature in K
£_{bp}-Emissivity of Block Plate Surface - 1
£_{tp}-Emissivity of Test Plate Surface
σ - Stefan Boltzmann's Constant = 5.67x10 ^{-8} m ^{2} k ^{4}
The emissivity of the test Plate is determined as (£_{tp}) ______ _ _ _
In radiation, internal energy of an object decreases.
It is defined as the total amount of radiation emitted by the body per unit time and unit area.
The energy emitted by the surface at a given length per unit time per unit area in all dimensions is known as monochromatic emissive power.
The heat transfer from one body to another without any transmitting medium is known as radiation
It is defined as the ability of the surface of a body to radiate the heat.
If a body absorbs a definite percentage of incident radiation irrespective of their wavelength, the body is known as Gray body.
It is defined as the rate of energy having a surface in a given direction per unit solid angle per unit area of the emitting surface normal to the mean direction in space.
A combination of Planck's law & Wien's displacement law yields the condition for the max monochromatic emissive power of a black body.
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