空げき率の高い水平多孔質層内の自然対流熱伝達(熱工学,内燃機関,動力など)  [in Japanese] Natural Convection Heat Transfer in a Horizontal Porous Enclosure with High Porosity(Thermal Engineering)  [in Japanese]

Heat transfer characteristics near the critical Rayleigh number for the onset of natural convection of horizontal anisotropic porous fluid layer heated from below with thin cylindrical rods inserted with high porosity above 0.822 to unity were studied by an analysis and an experiment. The critical Rayleight number Ra_c and dependence of Nusselt number on the Rayleight number were analysed by linear stability theory and series expansion method on the basis of Darcy flow assumption. Critical Rayleight number, increased with decrease in the porosity, was higher for the experiment than for the analysis but the difference was decreased with decrease in Darcy number. Experimental Nusselt number was considerably decreased with decrease in the porosity near unity although Ra_c is rather same as the case of Benard convection without cylindrical rods. The experimental Nusselt number can be expressed by one correlation curve when Nusselt number is plotted against Ra/Ra_c Darcy number of the present experiment was rather large to satisfy Darcy flow assumption. Experiment shows that Darcy flow assumption will be satisfied for Darcy number ⪇2×10^<-3>.