The Numerical Analysis of Low Prandtl Number Laminar Flow and Heat Transfer in Oval Tubes with a Small Twisted Ratio

Laminar fluid flow and heat transfer in twisted oval tubes are simulated by numerical analysis method.Numerical results show that when other parameters remain constant,the Nusselt number increases with increasing Reynolds number,and decreases with the increasing ratio of short axis to long axis b/a and twisted parameter Tr;the friction factor decreases with increasing Reynolds number,Tr and b/a.Besides,considering the coupling between the velocity and temperature fields,the reason for heat transfer enhancement is that the fluid rotates in the twisted oval tube and a secondary flow is induced.Small amplitude of secondary flow compared with the amplitude of the main flow will enforce heat transfer enhancement greatly,then the fluid heat transfer in the twisted oval tube is enhanced.