Research on Multiple-effect diffusion solar still

• Main Authors: Tze-Ling Chong, 張仕林
• Other Authors: Yeong-Chuan Kao
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/89595132579718678410

博士 === 國立臺灣大學 === 物理研究所 === 102 === A distiller (still) is mainly used for desalination and water purification, by heating water with impurities evaporating to vapor, and condensing the vapor to get clean water (distillation). A multiple-effect diffusion still (MDU) is a still with particular structure, the evaporated surface is close to condensed surface in each still cell, then the resistance of thermal mass transfer (diffusion) is low, furthermore, the incoming heat is reused repeatedly (multiple-effect) to increase the efficiency. Research on multiple-effect diffusion solar still (MEDS) and MDU are the topics of this thesis. The first content of the research is the design and manufacturing technique of MDU. Two types of MDU were developed, the first ameliorated traditional MDU by bending partition plate design (MDU-b), the second was an innovation design with spiral shape partition plate (MDU-s). The design of MDU-s has high potential to be commercialized with advantages of less heat loss, reliable structure, surmount manufacturing problems of MDU, and significantly reduce the production cost and difficulty. The second content of the research is system integration, test and analysis of MEDS. The systems of MEDS-b and MEDS-s were completed by using heat pipe to combine MDU-b and MDU-s with high efficiency vacuum tube solar collector respectively. Long term test and analysis of the systems were carried out, and the results were compared with the literatures. The highest measured dairy pure water production per unit area of collector of MEDS-b and MEDS-s are 25 kg and 39 kg respectively, with 25 MJ of daily-total solar irradiation per unit area of collector, higher than the record in literatures (about 20 kg). The third content of the research is the design and economic analysis of MDU. Theoretical model and empirical formula of flat-plate MDU (MDU-f) and MDU-s were established. Numerical methods were used to solve the heat balance equations. The performance and economic assessment with difference design parameter were analyzed to decide the optimal design. It’s show that narrowing the gap, increasing heating temperature, increasing heat dissipation capacity and decreasing heat loss of outlet water, can improve the economic of MDU. For a given cost composition of MDU, there is optimal number of effect which minimize the production cost of water. If solar energy is utilized, some optimal design will make MDU-s more benefit than traditional MDU. Cost analysis show that, if MDU-s and MEDS-s are utilized for sea water desalination, the freshwater production costs are comparable with other mainstream desalination technology.