Numerical study of flow and heat transfer in 3D serpentine channels using colocated grids

Abstract

channels, which have applications in heat-exchangers, were studied. A finite-volume code in FORTRAN was developed to solve this problem. Modules were made for generating rids in the domain, for valving the flow velocities and pressure, for solving temperature field and for post-processing the results. For solving the flow field, colocated grid formulation was used as opposed to the staggered-grid formulation, and the SIMPLE algorithm was used to link the velocity and pressure. The line-by-line method was used to solve the algebraic equations. The geometry of the problem facilitated the application of periodic inverted symmetry boundary condition. Since this is a forced convection problem, the flow field was solved first and the converged velocity field was input to the temperature solver module. The temperature field was solved for the uniform-wall-heat-flux boundary condition. The post-processing module obtained the overall friction-factor, which is representative of the pressure drop, the local and average Nusselt number. The numerical code developed was validated by solving for fully developed flow and heat transfer in a square straight channel. Grid-independent solution was established for a reference case of serpentine channel with the highest Reynolds number (Re=200). Periodically fully developed flow and heat transfer in serpentine channels were salved for different geometry parameters, for different Reynolds numbers and for two different Prandtl numbers ( 0.7 and 7.0 for air and water respectively). The results were plotted to study the effect of the independent parameters on the pressure drop and the heat transfer performance. The friction factor increased as the amplitude of the serpentine channel and the Reynolds number were increased. Similar trend was observed for the heat transfer coefficients. High heat transfer coefficients are observed at certain regions in the serpentine channels which are explained by the impingement phenomena. High Prandtl number (=7.0) gives higher heat transfer coefficients than the low Pr (=0.7) because of the thinner thermal boundary layer. The enhancement of heat transfer mechanism was explained by studying the plotted flow-field velocity vectors in different planes.