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Heat Transfer Handbook part 117. The Heat Transfer Handbook provides succinct hard data, formulas, and specifications for the critical aspects of heat transfer, offering a reliable, hands-on resource for solving day-to-day issues across a variety of applications. | INTERNAL NATURAL CONVECTION 1157 y q 0 L a 0 L b Th Partition 7777777777777777777777 c g Tc dN Insulated H 0 Th d T 777777777777777 d e f d1 Insulated Tc g h g i Figure 15.5 Natural convection heat transfer in confined porous media heated from the side a rectangular enclosure b rectangular enclosure with a horizontal partial partition c rectangular enclosure with a vertical full partition midway d rectangular enclosure made up of N vertical sublayers of different K and a e rectangular enclosure made up of N horizontal sublayers of diffeeent K and a f horizontal cylindrical enclosure g horizontal cylindrical annulus with axial heat flow h horizontal cylindrical or spherical annulus with radial heat flow i vertical cylindrical annulus with radial heat flow. 1158 POROUS MEDIA Conduction 102 H L 10 Tall system 102 Conduction 10-1 10-2 Shallow system Conduction Horizontal boundary layers Vertical boundary layers Figure 15.6 Four heat transfer regimes for natural convection in an enclosed porous layer heated from the side. From Bejan 1984. High RaH regime 104 106 RaH H Bejan 1984 that is four ways to calculate the overall heat transfer rate qf fH q dy. These are summarized in Fig. 15.6. Regime I the pure conduction regime defined by RaH 1. In this regime qf is approximately equal to the pure conduction estimate kmH Th Tc L. Regime II the conduction dominated regime in tall layers defined by H L 1 and L H Ra 2 1. In this regime the heat transfer rate scales as qf kmH Th Tc L. Regime III the convection-dominated regime or high-Rayleigh-number regime T o T f T Tti rtnc 7 o c It I I defined Dy RaH h l RaH . in this regime q scales as km Th Tc RaH . INTERNAL NATURAL CONVECTION 1159 Regime IV the convection-dominated regime in shallow layers defined by H L 1 and H L RaH 2 1. Here the heat transfer rate scales as q km Th Tc RaH 2. Considerable analytical numerical and experimental work has been done to estimate more accurately the overall heat transfer rate q or the overall .
