Performance modeling of quartz tube for gravity-driven solid particle solar receiver

Abstract

The interest in high-temperature solar receivers is increasing due to more and more applications in industrial fields. The solid particle is a promising heat transfer fluid for high-temperature receivers owing to the advantages of direct absorption, low cost, and high allowable temperature (∼1300 °C). The re-radiation losses of solid particles inevitably increase with the higher operating temperature. The quartz tube with a spectral selective transmissivity may be used for reducing re-radiation losses. This paper proposed a mathematical model to describe the heat transfer behaviors of the gravity-driven solid particle solar receiver with a quartz tube covered. The wavelength-dependent radiative properties of the quartz tube and particles were approximated by a gray band method. On-sun tests based on a linear-focused solar furnace were conducted, and test results verified the proposed model. Analysis results show that a reduction in β from 3676m−1 to 1000m−1 can boost the volume absorption effect and increase the solar-to-thermal efficiency from 0.54 to 0.64. A double-layered quartz tube design provides the best thermal performance by increasing the greenhouse effect of the quartz tube from −0.02∼0.08 to 0.41. The analysis results could be used for the optimal design and operation of the gravity-driven solid particle solar receiver.