A Numerical Study of the Effect of Aspect Ratio on Heat Transfer in an Annular Flow Through a 270-Degree Curved Pipe.

In the present paper, a three dimensional annular developing incompressible laminar flow through 270- degree curved pipe is numerically simulated. The dimensionless governing equations of continuity, momentums and energy are driven in toroidal coordinates. The governing equations are discretized by projection algorithm using forward difference in time and central difference in space. A three-dimensional computer code together with a grid generation program are developed in toroidal coordinates by which the present results were obtained. There is a non-uniform heat source q˝=BeAθ in the solid core and the outer wall is assumed to be adiabatic. Considering the effect of Reynolds number on thermo-hydraulic properties such as formation of secondary flow and axial velocity, it is possible to increase heat transfer using a non-uniform heat flux instead of the uniform one. The numerical results indicated that the average Nusselt number is increased by non- uniform heat flux compared with the uniform one assuming that both have the same average flux values. Also, the results indicate heat transfer increases as the aspect ratio is reduced.