Conceptual design of porous volumetric solar receiver using molten salt as heat transfer fluid

Abstract

Thermal radiation loss hinders the high-efficient operation of solar receiver at high temperature. Porous volumetric solar receiver using molten salt instead of air as heat transfer fluid is proposed. A comprehensive literature review is done to investigate the optical and radiative properties of molten in solar and infrared spectra. Direct pore-scale numerical simulation method based on X-ray computed tomography technique is applied to compare the fluid flow and heat transfer performance of molten salt and air porous volumetric solar receiver. The results present that some types of molten salts behave to be transparent in solar spectrum and opaque in infrared spectrum, which allow the penetration of solar radiation while strongly absorb the infrared emission in the receiver. The thermal efficiency of Hitec porous volumetric solar receiver is higher than traditional air porous receiver especially at higher working temperature, and it is improved by 9.6% at receiver’s outlet temperature of 1000 K. Due to its large heat storage capability and efficient convective heat transfer, small mass flow rate is required in the molten salt receiver to absorb solar radiation, which leads to orders-magnitude smaller pressure drop for the Hitec porous receiver. Further research related to this type of porous volumetric solar receiver is outlined with respect to experiment verification and application of high temperature molten salt.