| Conduction | Convection | Radiation |
| Consider a plane wall of thickness L and average thermal conductivity k. The two surfaces of the wall are maintained at constant temperatures of T1 and T2 | Consider convection heat transfer from a solid surface of area As and temperature Ts to a fluid whose temperature sufficiently far from the surface is T∞ with a convection heat transfer coefficient h. Newton’s law of cooling for convection heat transfer rate  can be rearranged as | When the wall is surrounded by a gas, the radiation effects, which we have ignored so far, can be significant and may need to be considered. The rate ofradiation heat transfer between a surface of emissivity ε and area As at temperature Tsand the surrounding surfaces at some average temperature Tsurrcan be expressed as |
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| Thermal resistance of the wall against heat conduction or simply the conduction resistance of the wall. | Thermal resistance of the surface against heat convection, or simply the convection resistance of the surface | thermal resistance of a surface against radiation, or the radiation resistance |
| Thermal resistance of a medium depends on the geometry and the thermal properties of the medium. | | is the radiation heat transfer coefficient. Note that both must be in K in the evaluation of |
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