Thermal efficiency of solar volumetric receivers using constant and variable fluid properties

Resumo

© 2021 by Begell House, Inc.This work investigates the use of variable fluid properties when simulating the behavior of solar volumetric receivers (SVR) via the thermal nonequilibrium approach. Energy balances for both air and porous ceramic materials are numerically solved using the SIMPLE method. The system of algebraic equations is relaxed by the SIP procedure. Thermal efficiency increases for lower inlet velocities and higher solid-to-fluid thermal conductivity ratios. For variable properties cases, a further increase in thermal efficiency is higher for lower solid-to-fluid thermal conductivity ratios and less noticeable for higher solid-to-fluid thermal conductivity values and lower velocities. Thermal efficiency is reduced for more permeable structures and higher porosities and for variable properties cases higher values are calculated due to increase in equilibrium temperatures. No appreciable dependence on Darcy number was detected when efficiencies were calculated with either constant or variable properties.

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