Study On Performance Of Water Recovery By Using Air-Water Multi-Effect Recovery Device For Wet Cooling Towers

With the rapid development of our economy,fresh water shortage is getting worse,and it has become an important factor restricting national sustainable development.Industrial water accounts for a large proportion in the total water consumption and industrial water saving has become a growing concern.The wet cooling tower,one of the important cooling equitment in industrial enterprises,consumes a huge amount of water which not only causes a great waste of water resources but also harms the environment and human health.At present,most of drift loss from wet cooling towers can be recovered effectively.However,there is still no effective way to recover evaporation loss which accounts for a larger proportion.In order to minimize the water loss in wet cooling tower,it was designed a novel water recovery device which consisted of a gas-liquid separation unit and a condensing unit based on cyclone separating,fiber coalescence and condensing technology and studied the water recovery efficiency.Firstly,in order to reduce the resistance fluid through the fibrous coalescer,a superhydrophobic coating of glass microfibers surface was prepared by dipping the fibrous coalescer into the mixtures of polydimethylsiloxane?PDMS?and silicon dioxide?SiO₂?nanoparticles.Then,based on the structure parameters of the cyclone separator and the fibrous coalescer,the condensing unit was designed properly.Finally,the influences of operating conditions and warm-wet air parameters on water recovery performance were studied in this work.The results showed that the pressure drops of the fibrous coalescer and the device no longer increased with the increasing of time when the glass fiber in the fibrous coalescer was modified with the PDMS emulsion mixed nanoparticles of SiO₂,and the droplet water recovery and total water recovery efficiency were 5.3%⁶.6%higher than those without modification of the fibrous coalescer.The center coil inserted in the cyclone separator could strengthen the fluid flow field and improve the water recovery efficiency of the device.After setting the center coil,the droplet water recovery efficiency was 4.1%⁵.0%higher than that without the coil pipes.Without cool water condensing the warm-wet air,the total water recovery efficiency of the device increased first and then decreased later with the increasing of the inlet flow rate.While when the warm-wet air was condensed by cool water,the variation tendency of the efficiency was complex.When the inlet flow rate was 50m³/h,the total water recovery efficiencies reached their maximum values 31.92%and 80.5%without and with cool water,respectively.As the liquid droplets concentration was increased,the total water recovery efficiency of the device with and without cool water increased steadily,and reached typically 87.41%and 35.78%when the liquid droplets concentration was 12.5g/m³.The droplet water recovery efficiency and total water recovery efficiency both increased gradually with the increasing of the warm-wet air temperature,and reached their maximum values 75.9%and 60.43%at the liquid droplets concentration of 8.5g/m³ and the warm-wet air temperature of 10?.This thesis is valuable for guiding application of the novel device in practice and developing new technologies of evaporation and drift loss recovery from wet cooling towers.