greenTEG is the world market leader in heat flux sensor technologies and heat flux measurement. We offer a wide range of sensors for measuring heat flux in many applications from building insulation evaluation, wearable technologies to battery calorimetry measurement. 

What is heat flux? 

Heat Flux is the rate of heat energy that passes through a surface. Depending on the exact definition of heat flux, its unit can be expressed as either W/m2 or W. Practically speaking, heat flux originates from temperature differences. For heat flux to exist, it requires, not only a temperature difference, but also a medium through which heat is flowing. Heat can flow through solid materials (in which case it is called conduction), through gases and liquids (which is called convection) and through electromagnetic waves (which is called radiation).

Temperature differences in a given system induce a heat flux. The induced heat flux always flows from the hot to the cold side. The following situations imply the presence of heat flux: 

✔️ Getting cold feet from standing on a cold floor: since the floor has a lower temperature than the feet, heat flows from the feet to the floor.

✔️ Standing close to a fire feels hot: the temperature of a fire is much higher than the surrounding air. Therefore, heat radiates from the fire to the surroundings.

✔️ Feeling hot in a sauna: since the air temperature in a sauna is higher than the body’s temperature, heat flows from the air into the body.

More documents related to heat flux are available here.