Effect of Heat-Flux Ratio on Two-Dimensional Horizontal Channel Flow

Numerical analysis is performed to investigate thermal fluid-flow transport phenomena in channel under asymmetrical heat flux from both side walls. Emphasis is placed on an effect of heat-flux ratio from both sides on the velocity and thermal fields. The low-Reynolds-number k-ε turbulence model and the two-equation heat-transfer model are employed to determine turbulent viscosity and thermal eddy diffusivity, respectively. It is found that 1) under strong heating from both walls, laminarization, that is, a substantial deterioration in heat-transfer performance, occurs as in the circular tube flow case; 2) during the laminarization process, both the velocity and temperature gradients in the vicinity of the heated walls decrease along the flow, resulting in a substantial attenuation in both the turbulent kinetic energy and the temperature variance over the entire channel cross section; and 3) in contrast, laminarization is suppressed in the presence of one-side heating because turbulent kinetic energy is produced in the vicinity of the other insulated wall. Therefore, an occurrence of laminarization in the channel is affected by the ratio of heat flux from both side walls.