聚光集热苦咸水蒸馏装置中含吸光颗粒水体的光吸收特性

传统太阳能蒸馏装置存在传热热阻大,传热换热环节多等缺陷,导致太阳能蒸馏装置热能利用效率低和淡水产量小,鉴于此,该文设计一种新型基于聚光集热的苦咸水蒸馏装置,利用抛物碟式聚光器将入射太阳光汇聚并直接在含有大量黑色多孔颗粒苦咸水体内完成光热转化,克服了传统太阳能蒸馏器光传输方向与热传输方向相反的缺点,减少了装置传热换热环节,使得聚光直接加热苦咸水蒸馏产水得以实现,该文对于装置中实现光热直接转化的水体光吸收特性展开试验测试和理论分析,借助光学积分箱对影响水体模拟受热温升阶段和沸腾蒸发阶段光吸收特性的吸光颗粒粒径、颗粒丰度及光程等因素展开研究。结果表明,含较小粒径吸光颗粒的水体光吸收特性较好,在模拟受热温升过程中,含粒径为0.5 mm颗粒的水体最大光吸收比比含有粒径为1.0 mm颗粒的水体增加9.0%,模拟受热沸腾过程中,丰度为6.7 g/L水体光吸收比是丰度为0.75 g/L水体的4.94倍,且水体光吸收比随沸腾程度呈指数函数变化规律。该研究结果为太阳能苦咸水蒸馏技术的热能高效利用提供参考。

Light absorption properties of water body filled with light absorption particles in solar-concentrating brackish water distillation device

Abstract: The earth is covered by approximately 70% water, while only 1% of existing earth''s water can be regarded as suitable for both human and agriculture needs. Unfortunately, with the world''s population growth, industrialization and climate change, the situation of the freshwater shortage will become even more serious. To seek solution for this problem, one of the valuable solutions is the desalination technology, which converts to pure and safe water from the current non-drinkable water supplies like seawater, brackish water and other dissipated water. Recently, the number of desalination plants has been growing, but industrialization desalination system consuming fossil fuel will provoke the crisis of environment. The water shortage regions are always blessed with abundant solar energy, so it is attractive alternative to utilize solar energy for the desalination of saline water to meet freshwater need. Among solar desalination technologies, solar distillation technology is used to provide pure water from non-drinkable water by solar energy directly and is suitable to supply water in remote area for small-scale application due to simple structure, easy material getting and less cost. However, solar distillation technology has some obstacles, such as low efficiency, little profitability rate of clean water and larger heat transfer resistance. In case of desalination process, to improve water production, the solar concentration is coupled with solar distillation. The thermal conversion of solar energy by means of solar concentrator makes it possible to reach high temperatures able to boil the salted water with higher pressures. However, there exists the structural mismatch between low efficiency of the solar collector system at high temperature and low efficiency of the brackish water desalination system at low temperature. In order to solve the problem mentioned above, a novel solar brackish water distillation desalination device based on dish type concentrating is proposed in present work. Compared with conventional solar brackish water distillation, it has some advantages, such as compact structure, multi-effect operation and heat recovery operation. During the operation, the concentrating solar energy is utilized to directly shine into the brackish water body filled with great amount of black porous particles to produce steam for repeated usage. It results in the decreasing heat and mass transfer resistance and heat exchange. The operation principle of the device was introduced. The light absorption properties of the brackish water body in the device were measured and investigated in optical darkroom. The objective of this work was to determine the influence of abundance, material of light absorption particles, optical path and diameter of particles on the light absorption properties of the water body under simulated non-boiling condition and simulated boiling condition. The results indicate that the water added with smaller light absorption particles has better light absorption performance. Under non-boiling condition, the light absorption rate of the water body filled with particles of 0.5 mm diameter increases by about 9.0% compared to that with particles of 1.0 mm. The light absorption rate of the water body with particle abundance of 6.7 g/L is 4.94 times that of the water body with particle abundance of 0.75 g/L under boiling condition. In addition, the light absorption rate of the water increases exponentially with the water boiling extent. It will provide a solution for the efficient utilization of energy with the solar brackish water distillation technology.