(4) The employment of porous media leads to a great increase
in heat transfer rate; however, due to the structural features
of the porous media, its employment also enlarges
the contact area between the porous media and the fluid
flow at the same time, thus increases the flow resistance
significantly. As a result, the effect of enhanced heat transfer
is relatively poor for turbulent flow. Nonetheless,
according to the concept of heat transfer enhancement in
the core flow, it is possible to develop inserts for enhancing
heat transfer in tube flow with better integrated performance
in large flow rates.