Heat and Mass Transfer
According of Kirchhoff's law

Ratio of emissive power to absorptive power for all bodies is same and is equal to the emissive power of a perfectly black body
Radiant heat is proportional to fourth power of absolute temperature
Emissive power and absorptivity are constant for all bodies
Emissive power depends on temperature

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Heat and Mass Transfer
Film coefficient is defined as Inside diameter of tube

Thermal conductivity Equivalent thickness of film Specific heat × Viscosity
Equivalent thickness of film
Thermal conductivity Molecular diffusivity of momentum Thermal diffusivity
Film coefficient × Inside diameter Thermal conductivity

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