Thermal Convection

Convection heat transfer occurs between a surface and a moving fluid (liquid or gas) when they are at different temperatures. The figure below introduces convection heat transfer, and the local heat flux is expressed as

Both convection heat transfer coefficient and local heat flux changes over the surface because flow conditions vary from point to point, The total heat transfer rate may be obtained as :

where

Factors affecting the thermal convection coefficient include:
Flow conditions, flow rate and direction, etc.
Types of fluids and the properties
Solid surface shape and surface state
The following table shows typical convection coefficient range for reference :