Abstract
Packed beds are widely used in catalytic reactors or nuclear reactors. Reducing the pressure drop and improving the heat transfer performance of a packed bed is a common research aim. The dimpled structure has a complex influence on the flow and heat transfer characteristics. In the present study, the flow and heat transfer characteristics in structured packed beds with smooth or dimpled spheres are numerically investigated, where two different low channel to particle diameter ratios (N = 1.00 and N = 1.15) are considered. The pressure drop and the Nusselt number are obtained. The results show that, for N = 1.00, compared with the structured packed bed with smooth spheres, the structured packed bed with dimpled spheres has a lower pressure drop and little higher Nusselt number at 1500 < ReH < 14,000, exhibiting an improved overall heat transfer performance. However, for N = 1.15, the structured packed bed with dimpled spheres shows a much higher pressure drop, which dominantly affects the overall heat transfer performance, causing it to be weaker. Comparing the different channel to particle diameter ratios, we find that different configurations can result in: (i) completely different drag reduction effect; and (ii) relatively less influence on heat transfer enhancement.
Highlights
Packed beds are widely used in industrial applications, such as catalytic reactors or nuclear reactors
The results showed that the grille-sphere composite structured packed bed (GSCSPB) can lower the pressure drop of the randomly packed bed and improve the heat transfer coefficient of the structured packed bed
Since the dimpled surface can be approximately treated as roughness surface, we find an experimentally study about the influence of surface roughness on resistance to flow through randomly packed beds by Crawford and Plumb [16]
Summary
Packed beds are widely used in industrial applications, such as catalytic reactors or nuclear reactors. A novel type of structured catalytic reactor packing with a very low channel to particle diameter ratio 1.0 and 2.0) called composite structured packing (CSP) is reported by Strangio et al [2]. Their results showed that the pressure drop of these structured packed beds was lower than that of randomly packed beds. They fitted a two-parameter pressure drop correlation for different N by using the CFD results. Rokmes et al [4] numerically and experimentally investigated the heat transfer performance of these structured packed beds and gave correlations of Nusselt numbers by fitting the CFD results
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