Highly accurate solutions of the bifurcation structure of mixed‐convection heat transfer using spectral method

Abstract

SUMMARYThis paper is concerned with producing highly accurate solution and bifurcation structure using the pseudo-spectral method for the two-dimensional pressure-driven ow through a horizontal duct of a square cross-section that is heated by a uniform ux in the axial direction with a uniform temperature on the periphery. Two approaches are presented. In one approach, the streamwise vorticity, streamwise momentum and energy equations are solved for the stream function, axial velocity, and temperature. In the second approach, the streamwise vorticity and a combination of the energy and momentum equations are solved for stream function and temperature only. While the second approach solves less number of equations than the ÿrst approach, a grid sensitivity analysis has shown no distinct advantage of one method over the other. The overall solution structure composed of two symmetric and four asymmetric branches in the range of Grashof number (Gr) of 0-2 × 10 6 for a Prandtl number (Pr) of 0.73 has been computed using the ÿrst approach. The computed structure is comparable to that found by Nandakumar and Weinitschke (1991) using a ÿnite di erence scheme for Grashof numbers in the range of 0 -1 × 10 6 . The stability properties of some solution branches; however, are di erent. In particular, the two-cell structure of the isolated symmetric branch that has been found to be unstable by the study of Nandakumar and Weinitschke is found to be stable by the current study.

Enhancement of Heat Transfer in Laminar Flows Using a Toroidal Helical Pipe

“…The simplification is on purpose to avoid the complexity introduced by the Rayleigh number and various alignments with the gravity vector and is valid for flows under the critical Rayleigh number. We will explore the effect of natural or mixed convection in the future, as has been done for torus. , …”

“…We will explore the effect of natural or mixed convection in the future, as has been done for torus. 42,43 The inlet always has the fully developed Hagen−Poiseuille profile. Using the pipe radius as the length scale, we can define a polar coordinate (ρ,θ) on the inlet face where 0 ≤ ρ ≤ 1 and 0 ≤ θ ≤ 2π.…”