Numerical simulation of boiling in a direct steam generation system in a parabolic solar collector using a homogeneous two-phase model

A milestone in linear parabolic solar power plants is the use of direct steam production systems. In these systems, due to the presence of water as a heat transfer fluid, we witness an increase in the working temperature. In a direct-production steam generator (DSG), the Sun's energy hits the tube where the water flows. Failure to control the flow of fluid in the boiling section leads to the arrival of the thermal flux of the fluid to the critical heat flux. The important point in designing these types of power plants is the critical point (with critical heat flux), which causes many problems, including thermal stresses in solar absorber. Therefore, the study of the boiling process in the absorber of these power plants is important. In this research, a homogeneous two-phase model is introduced for numerical simulation. In the first stage, an optical model for the reflector is simulated. In the next step, the heat transfer equations are simulated for radiation absorbent and heat transfer inside the pipe. Finally, the changes in the tube's wall and water temperature are investigated. The LUT method has been used to determine the location and amount of critical heat flux. In modeling, steam quality, wall temperature and fluid temperature and critical thermal flux point are obtained for different values of pressure and mass flow and the system efficiency is determined. The system's continuous function for different radiations (which is equivalent to different climatic conditions) has been examined.