NUMERICAL ANALYSIS OF LAMINAR FLOW AND HEAT TRANSFER IN TWISTED ELLIPTIC TUBES

Laminar fluid flow and heat transfer in twisted elliptic tubes is simulated by the dual-velocity algorithm. Numerical results show that when the other parameters maintain constant, the Nusselt number increases with increasing Reynolds number and Prandtl number, and decreases with the increasing ratio of short axis to long axis B/A and twist parameter S/B. When Reynolds number is less than 500 and Prandtl number is less than 200, η is always larger than 3. And, the larger the Prandtl number is, the larger η will be. The twisted elliptic tube is an excellent enhancement device for laminar convection heat transfer, especially for large Prandtl numbers. The reason of heat transfer enhancement is that the fluid rotates in the twisted tube and a secondary flow is derived. There is a velocity component perpendicular to the wall surface, which results in a larger temperature gradient near the tube wall.