What is the Difference Between Thermal Conductivity and Diffusivity?

Thermal conductivity and thermal diffusivity are two terms that describe heat transfer through a material, but they represent different aspects of the process. The key difference between them is:

• Thermal Conductivity: This refers to the ability of a material to conduct heat, or how quickly heat flows through the material from the hot side to the cold side under steady-state conditions. It is calculated as the ratio of heat flow to the product of the temperature gradient and the cross-sectional area. A material with high thermal conductivity can propagate heat faster within it.
• Thermal Diffusivity: This describes how well a material can spread heat, taking into account both how quickly the heat can be conducted through the material (thermal conductivity) and how quickly the material's own temperature can change when heated. Thermal diffusivity is the thermophysical property that defines the speed of heat propagation by conduction during changes of temperature. It is calculated as the ratio of thermal conductivity to heat capacity.

While thermal conductivity is a contributing factor to thermal diffusivity, it is not the whole story. A material with high thermal diffusivity requires both high thermal conductivity and low heat capacity. In summary:

• Thermal conductivity describes the speed at which heat flows through a material under steady-state conditions.
• Thermal diffusivity describes how well a material can spread heat, considering its thermal conductivity and heat capacity.

Comparative Table: Thermal Conductivity vs Diffusivity

Thermal conductivity and thermal diffusivity are both related to the heat transfer properties of materials, but they describe different aspects of this process. Here is a table summarizing the differences between the two:

In summary, thermal conductivity refers to a material's ability to conduct heat, while thermal diffusivity measures the rate at which heat is transferred within the material. Both properties are important for understanding the heat transfer behavior of materials in various applications, but they describe different aspects of this process.