Heat and Mass Transfer
When heat is transferred from one particle of hot body to another by actual motion of the heated particles, it is referred to as heat transfer by

Convection
Radiation
Conduction
Conduction and convection

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Heat and Mass Transfer
Fourier's law of heat conduction is (where Q = Amount of heat flow through the body in unit time, A = Surface area of heat flow, taken at right angles to the direction of heat flow, dT = Temperature difference on the two faces of the body, dx = Thickness of the body, through which the heat flows, taken along the direction of heat flow, and k = Thermal conductivity of the body)

k. A. (dx/dT)
k. A. (dT/dx)
k. (dx/dT)
k. (dT/dx)

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Heat and Mass Transfer
The heat transfer by conduction through a thick cylinder (Q) is given by (where T₁ = Higher temperature, T₂ = Lower temperature, r₁ = Inside radius, r₂ = Outside radius, l = Length of cylinder, and k = Thermal conductivity)

Q = 2.3 log (r₂/r₁)/[2πlk (T₁ - T₂)]
Q = = 2πlk/2.3 (T₁ - T₂) log (r₂/r₁)
Q = [2πlk (T₁ - T₂)]/2.3 log (r₂/r₁)
Q = [2π (T₁ - T₂)]/2.3 lk log (r₂/r₁)

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