Abstract:
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.