Performance analyses on a novel evacuated U-tube solar collector powered direct contact membrane distillation hybrid system for seawater desalination

Abstract

Short lifespan and low thermal efficiency are two key hindering factors for the development of solar desalination system. Herein, a novel hybrid system model of a direct contact membrane distillation (DCMD) desalination system powered by a durable and efficient evacuated U-tube solar collector (EUSC) is proposed. The models of both EUSC and DCMD are mathematically formulated and validated. The permeate flux, energy efficiency and exergy efficiency of the proposed system are deduced as performance indicators. The performance of the proposed system is predicted under the weather conditions of Ningbo city, China. Under the typical weather condition, the maximum permeate flux, energy efficiency and exergy efficiency of the proposed system are 4.45kgm- 2h- 1, 25.47 % and 4.73 %, respectively. The freshwater yields of August and total year of 2021 in Ningbo city, China are presented. Additionally, the long-term performance with past 41 years is also studied. The effects of solar irradiance, environment temperature, feed flow velocity, feed water Reynold number, permeate liquid temperature, permeate flow velocity, porosity and average pore radius of DCMD membrane are investigated via parametric studies. The proposed EUSC/DCMD coupling system may provide a promising alternative to stand-alone, small-scale desalination systems for freshwater generation.