Numerical characterisation of the convective heat transfer and fluid flow for inline woven wire meshes in solar volumetric receivers

Abstract

In solar tower systems, metallic woven wire meshes following an inline arrangement are a promising geometry for commercial application in open volumetric receivers (OVRs). To assess their potential, two main parameters, with two different methodologies, need to be analysed in depth: the convective heat transfer coefficient (HTC) and the pressure drop per unit length (ΔP/L). In this study, three wire diameters, 0.7, 0.4 and 0.1 mm, with a fixed porosity of 80 %, have been selected to establish a baseline for the HTC and the ΔP/L sensitivity studies. In the HTC methodology, six air inlet velocities between 0.5 and 5 m/s, and constant solid matrix temperatures of 700, 1100 and 1500 K, have been evaluated. For the ΔP/L methodology, six air inlet velocities between 0.5 and 5 m/s and a constant solid matrix temperature of 300 K was used.

For each thermo-fluid-dynamic attribute, HTC and ΔP/L, and each wire diameter (0.7, 0.4 and 0.1 mm) with 80 % porosity, an individual correlation is presented resulting in a total of six individual correlations. In addition, two generalised correlations, one of each thermo-fluid-dynamic attribute, for 80 % porosity and wire diameter ranging from 0.1 to 0.7 mm are shown, taking into account the specific geometrical parameters of the wire mesh lattices. The generalised correlations obtained in the study present deviations under 7 % from the CFD results in both thermo-fluid-dynamic attributes, showing results as good as the ones obtained with the individual correlations. As a result, it is demonstrated that the geometrical parameters must be included in the correlations used to predict the thermo-fluid-dynamic attributes in wire mesh lattices. All the correlations have been validated through porous models with good agreement and they would work for future optimisation studies.