Numerical Analysis of Turbulent Fluid Flow and Heat Transfer in a Rectangular Elbow

Abstract

The numerical analysis of turbulent fluid flow and heat transfer through a rectangular elbow has been done by   model with standard wall function. Different inlet uniform velocities of 5m/s, 10m/s, 15 m/s, 20 m/s and 25 m/s corresponding to Reynolds numbers of Re1= 4.09× 104, Re2= 8.17 × 104, Re3= 12.25× 104, Re4= 16.34× 104 and Re5 =20.43 × 104 have been considered for the numerical experimentations. The fluid considered was incompressible, Newtonian non-reacting and the flow was fully turbulent. The heat transfer analysis has been carried out by considering the fluid having at a higher temperature while the wall kept at lower temperature. A detailed study of the turbulent fluid flow shows that presence of recirculation is inevitable at every corner position or at every bend indicating presence of secondary flow incurring energy losses. The velocity distributions at different stations along the downstream path of the elbow have been plotted. The presence of this adverse pressure gradient is confirmed by the reverse velocity or the negative velocity in the vicinity of the vertical wall. In the upper corner there is a vortex extending from the upper wall of the upper limb almost touching the end point of the left wall of the vertical portion of the elbow. The heat transfer also shows the similar tendency as the fluid flow field influences the convective heat transfer process. The detail temperature distributions across any cross section basically explain the dependence of the convective heat transfer on the fluid flow field.