Heat recovery capacity and water desalination performance of passive solar vacuum tube distiller

Abstract

The direct thermal distillation utilized the solar vacuum tube was a seawater desalination technology with quite a development potentiality. Therefore, an efficient passive solar vacuum tube distiller (P-SVTD) with a heat recovery function was developed in this paper, which realized the integration operation of raw water vaporization and high-temperature steam self-pressurization. It also had the character of simultaneously carrying out boiling vaporization and interfacial vaporization. The mechanisms of photo-thermal conversion and heat-mass transfer in the whole operation process of P-SVTD were analyzed. The theoretical calculation models of water yield (msh) and heat recovery rate (HRR) were presented. The water desalination performance, temperature level of recovered heat, and HRR of P-SVTD were measured to obtain the comprehensive photo-thermal conversion efficiency (HE) of P-SVTD. The results showed that the optimal depth ratio of the vapor–liquid interface to the vaporized-pressurized cavity was 0.9718. The water yield of P-SVTD was positively correlated with the total solar irradiance on the inclined plane by the trend of an exponential function. The average temperature level of recovered heat, HRR, and HE of P-SVTD were 74.30 °C, 28.68 %, and 87.43 %, respectively. And the rejection capacity (REJ), the decreased degree of conductivity, and the pH of P-SVTD were close to 100.00 %, 100.00 %, and 7.00, respectively, which showed excellent desalination capacity. The research provided solid technical and theoretical support for promoting the large-scale application of passive solar distillation technology.