Hydrodynamic Analysis Of DSG Solar Trough Collectors

Compared with the parabolic solar thermal power generation technology based on synthetic oil, direct steam generation(DSG) solar thermal power technology with water as working fluid is one of the most commercial prospects of solar energy thermoelectric technology. DSG simplifies the structure of the system, improves the steam temperature at collector outlet, which has high power generation efficiency and low initial investment. DSG solar collector is a typical two-phase system, which is prone to hydrodynamic instability phenomenon and does harm to the normal operation of the system. Therefore, the study on hydrodynamic instability of DSG solar thermal power system can provide theoretical guidance for the design and operation of this kind of solar thermal power system. It also has great significance for promoting the development of DSG solar thermal power technology in China.The mathematical model of DSG solar collector is established in this paper. As for the flow and heat transfer process in steam-water system, a numerical simulation model for particle tracking method based on Lagrange is established. The numerical simulation results are in good conformity with the experimental results, which prove the reliability of the established mathematical model.Based on the numerical simulation model, the water dynamic characteristic curve of DSG solar collector system can be acquired. Then the influences of input temperature, pressure, solar radiation intensity and heat collector diameter on the water dynamic multi value of system are analyzed. The results show that, increasing the working fluid temperature and system pressure of imports is helpful to improve the water dynamic characteristics of DSG solar collector system. The hydrodynamic instability flow range of the system is becoming larger while the solar radiation intensity is increasing higher. While the heat collecting pipe diameter is reducing, the pressure drop of the system is becoming bigger and the dynamic characteristics of water tends to be stable with the basically unchanged unstable range.Based on the analysis of the hydrodynamic characteristics of a single collector tube, and the flow distribution characteristics of parallel arrangement DSG collector system are further studied. The results show that, due to the impact of the hydrodynamic instability, when the parallel collectors tube receive the same solar radiation, the flow rate distribution of the collectors may appear significant difference. When there is a deviation of solar radiation intensity between the parallel tubes, the flow distribution between the parallel tubes is very complex: in the solar radiation intensity deviation, if the collector tube bears larger solar radiation intensity, then the flow of the collector tube is larger; with the solar radiation intensity deviation gradually become larger, and the flow range of the system corresponding to the flow distribution characteristics smaller; when the solar radiation intensity deviation reaches to a certain degree, parallel heat collecting system possibly appear the opposite distribution characteristics, namely if the collector tube bears larger solar radiation intensity, then the flow of the collector tube is smaller.All the works above provide the basic for the future study of DSG trough solar thermal power generation system, and provide theoretical guidance for the safety operation of DSG trough solar thermal power system.