| The shortage of drinking water is one of the most severe global challenges that currently plague human society.Solar-driven freshwater production is expected to solve this problem,which has attracted widespread attention in recent years.In particular,the rapid-developing interfacical solar desalination technology has shown great potential in freshwater production due to its various advantages,such as high evaporation efficiency,low installation and operating costs,no traditional fossil energy consumption and environmental friendliness.However,some current solar desalination technologies based on interfacial heating still have major problems,such as poor thermal management,easy salt accumulation and difficult to synchronously achieve high-efficient and continuous salt-rejecting operation.In response to these problems,different interfacial solar desalination systems were prepared and designed in this thesis.From the perspective of heat and mass transfer,the factors that affect the thermal management and salt rejection capacity were analyzed.The effects of the porosity and the materials thermal conductivity of the water-absorbing layer on the thermal insulation and evaporation performance,and the influences of the porosity and pore size of the water-absorbing layer on the salt-rejecting capacity are systematically explored.Besides,a reasonable thermal insulation design for water supply is proposed.Finally,these problems on high heat loss,low thermal efficiency,salt accumulation,and poor structural stability are solved.The details are as follows:(1)From the perspective of reducing the heat transfer loss,by optimizing the porosity and the materials thermal conductivity of the water-absorbing layer,the thermal insulation performance of the system is improved,thereby the thermal efficiency increases.A bi-layer solar evaporator with good thermal insulation and high structural strength is prepared by spraying carbon black particles on the lignocellulose/polystyrene composite obtained by cold pressing and sintering.The influence of porosity and polystyrene content of the water-absorbing layer on thermal insulation and evaporation performance of the system was explored by experiment,and the optimal porosity and polystyrene content for improving evaporation efficiency were obtained.Combining the optimized evaporator and a one-dimensional water supply design,evaporation efficiency of the system can reach about 80.4%under a 1-sun illumination.This work provides some ideas for the design of some highly efficient evaporators.(2)From the perspective of simultaneously increasing the mass transfer rate and reducing the heat transfer loss,porous structure of evaporator,such as porosity and pore size,is optimized to enhance salt-rejecting capacity of the system.At the same time,a new heat-insulating water supply device was designed to achieve the system continuously high-efficiency and salt-rejecting operation under a high brine environment.A porous skeleton evaporator was prepared by using a pore-forming agent to control porous structure.A super-hydrophilic and heat-insulating water supply device was designed by drilling.The influence of porous and pore size of the evaporator were analyzed by experiments on salt-rejecting capacity of the system,and the optimized porosity and pore size for resisting high-salinity brine were obtained.Combining the evaporator with optimized porous structure and the super-hydrophilic heat-insulating water supply device,under a1.5-sun illumination,the system achieves continuously high-efficiency salt-rejecting working for more than 12 hours in a 15%high salinity environment.In which,the evaporation rate can reach about 1.90 kg·m-2·h-1,and the evaporation efficiency is as high as 85.5%.This system is expected to be an ideal choice for practical application of interfacial solar desalination techonology.There are 29 figures,6 tables and 141 references in this paper. |
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