The rate at which heat is transferred or conducted through a substance is directly proportional to the
1. Area of the surface (A) perpendicular to the flow of heat and
2. The temperature gradient ΔT/ x along the path of heat transfer.
For a one dimensional steady state heat transfer Rate of Heat Transfer is expressed by Fourier equation:
Q = kA ΔT/ Δx.
where,
K = Thermal Conductivity depends on the material
A = Area of the surface
ΔT/ Δx = Temperature gradient for small change in temperature with respect to distance.