Heat flux

An introduction to heat flux: definition & equation

This short note aims to give the reader an introduction to the concept of heat flux with its definition and working principle, equation and research and industrial applications.

Heat Flux: The definition

heat flux sensor explanation

It describes the rate of heat energy that passes through a surface. Depending on its exact definition, its unit can be expressed as either W/m2 or W. Practically speaking, it is originates from a temperature differences in a given system. The induced heat always flows from the hot to the cold side. This mechanism requires, not only a temperature difference, but also a medium through which to flow.

Heat flux: Three types

Heat can flow through:

  • Solid materials in which case, the phenomenon is called “conduction”.
  • Gases and liquids in which case, the phenomenon is described as “convection”.
  • Electromagnetic waves in which case, the mechanism is named “radiation”.

Those three different mechanisms are well represented by the following illustrations:

three types of heat transfer
three types of heat transfer

three types of heat transfer

This phenomenon is dependent upon the temperature difference and the thermal transfer coefficient.

Heat Flux: The equation

With respect to the temperature difference and the thermal transfer coefficient:

HF = ∆T x HTC

with HF, the Heat Flux, in W/m2, ∆T, the temperature difference [K], and HTC, the heat transfer coefficient, in W/(m2K).


Heat flux sensors are the tools employed to perform heat flux measurement. greenTEG offers a broad range of sensors suited to the following applications.

For Industrials

For more technical information, check our the full product line available here!

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  • Discover all the Use Cases related to our technology, here.
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