What is Heat Flux?

So, what is heat flux? If you really want to understand your thermal process and how it impacts your product then you need to be measuring Heat Flux. In simple terms Heat Flux is the rate at which thermal energy is transferred from one area to another.

In the case of an oven, where we are generally looking to bake products, heat energy must be transferred to the product in a very controlled and consistent fashion.  Consistency and repeatability are absolutely key. In many thermal processes it is not just the amount of energy that is transferred that is important but also the rate of transfer as this determines the product characteristics.

It is important to note that measuring air temperature within a thermal process is important but on its own does not provide sufficient information to characterise the process. This is where Heat Flux comes into its own.

Units of Heat Flux: W/m² or Btu/h.ft²

One of the fundamental advantages of measuring Heat Flux is that it takes all contributory factors into account, and does allow the thermal characteristics to be defined.

• Air temperature

• Air movement

• Mode of heat transfer (convection and radiation)

• Direction of heat transfer (top or bottom)

• Oven design

In slightly more detail, Heat Flux is defined as the amount of energy passing through an imaginary surface of unit cross-sectional area in unit time.