Heat and Mass Transfer
Thermal diffusivity of a substance is given by (where h = Thermal diffusivity, ρ = Density of substance, S = Specific heat, and k = Thermal conductivity)

h = S/ρk
h = k/ ρS
h = kρ/S
h = ρS/k

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

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

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