Transient natural convection in a horizontal fluid layer, with a blackbody bottom; heated from above by radiation

摘要

Transient natural convection in a horizontal fluid layer, with a blackbody bottom, heated from above by radiation was studied experimentally and numerically. The heat flux which reaches to the bottom is absorbed by the black surface and reheats the fluid layer from thebottom, creating an adverse t4mperature gradient at the bottom of the fluid layer similar to the one observed in the classical Rayleigh-Benard problem. A mathematical model was developed and governing differential equations were numerically solved. The predictions of the model were found to be in an acceptable agreement with the experimental temperature distributions obtained in a laboratory scale pool by holographic interferometer techniques. Experimentally and numerically calculated heat convection coefficients were correlated in terms of Nusselt and Rayleigh numbers and compared with a literature correlation. It is concluded that this problem is very similar to the classical Rayleigh-Benard problem of a horizontal fluid layer heated from below.