Study On Heat Transfer Of Double Layer Skeleton Structure For Solar Desalination

The system for solar steam generation can make use of solar energy to desalinate seawater.It has great application potential in the fields of seawater desalination and sewage treatment.At present,efficient solar steam generation systems mainly include nano-fluids solar steam generation system and thermal localization solar steam generation system.The thermal localization solar steam generation system is mainly carried out on double-layer structure.Due to its simple structure,low cost,high evaporation efficiency under low concentration,double-layer structure has attracted wide attentions.From the viewpoint of energy conservation,the heat loss in the evaporation process of the solar steam generation system with double-layer structure can be decomposed into four parts:the light reflection loss caused by the incident light irradiation on the light absorption layer,the heat radiation loss from the surface of the light absorption layer to the environment,the heat convection loss between the surface of the light absorption layer and the surrounding air and the heat transfer loss from the adiabatic water supply layer to the water body.In this paper,materials selection and structure optimizations are carried out to reduce the energy losses.For the light absorbing layer,the wood was carbonized at a high temperature to produce biomass carbon particles.Meanwhile,the influence of the particle size distributions was studied.The calculation by Mie’s scattering theory proves that the carbon particles could have good light absorption ability under proper particle-size distribution,which confirms the excellent experimental performance of self-made carbon particles as top light absorbing materials.In order to reduce the heat loss caused by surface radiation,the copper nanoparticles have been also used our work.Considering that the copper nanoparticles have high absorption in the ultraviolet-visible region,but low absorption rate in the far infrared band,they can effectively absorb solar energy and only lead to a low thermal radiation losses.For adiabatic water supply layer,this paper explores a skeleton double-layer structure,which uses air to hinder heat dissipation.By exploring the height of skeleton layer above water surface and the area of air layer in cross-section,the optimal value is obtained,and the heat conduction losses from the bulk water is reduced as much as possible under the premise of ensuring adequate water supply.To reduce the heat losses,100nm copper nanoparticles were prepared as the optical absorption layer material,and the optimized skeleton structure was used as the skeleton double-layer structure of the adiabatic water supply layer.The actual evaporation rate could reach 2.11 kg·m^-2·h^-1.By optimizing the system from the view point of energy losses,this work is devoted to improving the performance of the solar steam generation system,and also providing a route with high efficiency,stability,low cost and more operability.