A heat transfer correlation of Poiseuille-Rayleigh-Bénard convection in the thermal entrance region of a horizontal rectangular channel

Abstract

In order to understand heat transfer characteristics and obtain a heat transfer correlation of Poiseuille-Rayleigh-Bénard (P-R-B) convection in the thermal entrance region of a horizontal rectangular channel, we performed a series of the direct numerical simulations. The working fluid is water, and the spanwise aspect ratio of the rectangular channel ranges from 2 to 10. The results show that the thermal entrance length for the onset of buoyancy-driven convection extends with the decreasing Rayleigh number and the increasing Reynolds number. The average Nusselt number in the thermal entrance region increases with the increase of Rayleigh number and Reynolds number. Furthermore, a smaller aspect ratio and a shorter length of the channel contributes to enhanced heat transfer in the thermal entrance region. Based on the simulation results, the heat transfer correlation in the thermal entrance region is established, which can be used as a reference for the engineering design on P-R-B convection.