What is the term for the measure of a material's ability to transfer heat per unit time, given a unit area and a gradient through its thickness?

What is the term for the measure of a material's ability to transfer heat per unit time, given a unit area and a gradient through its thickness?

• A. Thermal conductance
• B. Thermal resistance
• C. Thermal emissivity
• D. Thermal capacity

Answer: (A)

Heat transfer through a solid with a temperature difference across its thickness follows Fourier’s law: Q = k A (ΔT / Δx). Here the factor that links the heat flow rate to the driving temperature difference, for a given area and thickness, is kA/Δx. This quantity expresses how readily heat moves per unit time for that setup and is defined as thermal conductance. It’s the measure of a material’s ability to transfer heat under those conditions and has units of W/(m^2 K) when you consider conductance per area. The reciprocal of this is thermal resistance, which tells you how much temperature difference is needed for a given heat flow. Emissivity relates to radiative heat transfer, and thermal capacity concerns energy storage, not the rate of conduction. So the term describing heat transfer per unit time for a unit area and a thickness-driven gradient is thermal conductance.

Heat transfer through a solid with a temperature difference across its thickness follows Fourier’s law: Q = k A (ΔT / Δx). Here the factor that links the heat flow rate to the driving temperature difference, for a given area and thickness, is kA/Δx. This quantity expresses how readily heat moves per unit time for that setup and is defined as thermal conductance. It’s the measure of a material’s ability to transfer heat under those conditions and has units of W/(m^2 K) when you consider conductance per area. The reciprocal of this is thermal resistance, which tells you how much temperature difference is needed for a given heat flow. Emissivity relates to radiative heat transfer, and thermal capacity concerns energy storage, not the rate of conduction. So the term describing heat transfer per unit time for a unit area and a thickness-driven gradient is thermal conductance.