Research Of Water Harvesting Performance Of Water Harvesting Device Based On Condensation Surface With Microstructures

With the gradual depletion of water resources and the further expansion of human activities,how to obtain fresh water in arid and semi-arid areas with difficult water resources is being paid more and more attention.In such places,fresh water would be crucial for field investigation,field troops,emergency rescue and other applications.As a large container of clean water resources,the atmosphere has gradually become an important source of fresh water.In recent years,water harvesting technology based on air cooling,adsorption desorption and water droplet extraction has increased.Among these technologies,adsorption-desorption technology shows the most research value because of its portability.However,the main focus of the present study is to improve the adsorption properties of the adsorbents,while ignoring the removal efficiency of the condensed water,which has a vital effect on the efficiency of the water output of the water harvesting devices.Inspired by the surface morphology of the animal and plants with the ability of water harvesting in nature and based on the principle of bionics,this paper proposes the condensation surface of the water harvesting device based on the PDMS material commonly used in the microfluidic industry,and promotes the combination and removal of water droplets by changing the surface microstructure of its surface,thus improving the water output of water harvesting device.Based on the theoretical deduction of the force balance and thermal conductivity of the droplets on a plane,the optimum size model of the droplet on the condensing surface is proposed.The self-removal of the water droplets under this size can ensure that the condensation surface has the best heat transfer efficiency,which is beneficial to the continuous production of condensate water and also prevents the droplets from growing.Smaller size droplets would reduce the overall efficiency of the water intake device.In this paper,the design and preparation of the PDMS condensing surface were completed,and an experimental platform for constant temperature and constant humidity control was built.The effect of condensation and removal of water droplets from PDMS condensing surface with different surface microstructures under various conditions of different relative humidity and supercooling was experimentally investigated.Using image processing technology,the number of droplets,the area covered by droplets and the average diameter of droplets on PDMS condensate film were quantitatively analyzed.The whole design and manufacture of portable water harvesting device based on PDMS condensate membrane has been completed in this paper.The optimum adsorption time of the discolourant silica gel adsorbent was determined.The experimental platform was set up to measure the temperature and humidity of the water vapor during the desorption process.The working state and performance of the device were analyzed,and the optimum desorption time was determined.The stability of the continuous operation of the device is verified by repeated experiments.The necessity of passive air cooling is proved by comparative experiments.