A review of turbulence promoters used in solar thermal systems

In order to enhance rate of heat transfer to flowing air in the duct of solar air heater and in heat exchanger or in cooling of turbine blade various turbulence generators viz. ribs, baffles and delta winglets are considered as an effective technique. Investigators reported various turbulence generators in literature for studying heat transfer, friction characteristics and flow pattern in heat exchanger and in solar air heater. In the present article an attempt has been made to categorize and review the reported turbulence generators used for heat transfer enhancement in heat exchanger and solar air heater and gives an approach for further research for forced convection from the surfaces with large scale roughness.