Study on Pressure Decompression Type Seawater Desalination System Driven by Solar Focusing Heating

• Main Authors: linsasu, 林聖書
• Other Authors: 陳合進
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/07096538669865827334

碩士 === 樹德科技大學 === 應用設計研究所 === 95 === In this article, the research is primarily focused on the solar energy seawater desalination system. Seawater is characterized by low boiling temperature when it is under a pressure lower than one atmospheric pressure. By using solar energy as a heat source for heating and extracting air from the seawater desalination system manually so as to reduce pressure in the system, it is possible to boil and evaporate seawater with lower heat energy. The solar radiation can help boil and evaporate seawater once it is heated through the heat-collecting effect of the solar collector, and then the motor will circulate the seawater to make the cooled and evaporated vapor condense into potable pure water. The said system is expected to solve the crisis of lacking fresh water in the future, reduce the harm to the earth due to consumption of energy, slow down the green house effect and further reach the goal of sustainable development. Combining the seawater desalination with the application of solar energy is able to reduce the utilization and consumption of heat energy in the process of seawater desalination. In the course of producing fresh water, the researcher applied the principle of parabolic focusing to calculate the optimal concentration ratio with reference to relevant literature, to produce the heat collecting and evaporation equipment, and to modify the cylinder into manual vacuum air-extracting equipment, closed vacuum chamber, etc. The experimental results showed that the temperature of seawater of 350 ml raised from 26.2℃ to 86.4℃ within 15 minutes in the initial stage. The heat-collecting efficiency of the heat-collecting device was as high as 55.3%. Within 15 minutes., the circulation cooling water could reduce the water temperature of water of 7500 ml reduce from 42.1℃ to 25.4℃ and produced heat of 125.25 kcal. If the system structure was enhanced, the air-extracting equipment could reduce the system pressure to 25 cm-Hg under an optimal condition. This would be in line with the heating temperature of the solar heating system and could produce a sudden boiling phenomenon of seawater, meeting the economic effect. The best fresh water production capacity of the system is to produce 38ml of fresh water with salinity of 220 ppm from 200ml of seawater within 30 minutes. The fresh water so produced will also meet the national potable water standard. This system can be used to produce fresh water for fishing vessels and provide domestic water to offshore islands. Producing fresh water by utilizing solar energy and supplying domestic water to fishing vessels and offshore islands will not need to consume extra energy. Moreover, the manual pressure reducing equipment will allow the water so desalinated to meet the national potable water standard. To sum up, the system will be one of the methods to solve the problem of water deficiency on the sea and offshore islands.