Conduction
Energy transfer from the high-temperature region to the low-temperature region due to thermal diffusion process. It can take place in solids, liquids and gases. The Fourier's law states that the rate at which heat is conducted through a body per unit cross-sectional area is proportional negatively to the temperature gradient existing in the body.
where k is the thermal conductivity (W m/ ºC) and dT/dx is the local temperature gradient, dQ/dt is the rate of heat transfer (W), A is the cross-sectional area (m2).
Minus sign indicates that the energy flow in the direction of decreasing temperature.