Thermo-hydraulic modelling for Direct Steam Generation

Abstract

Parabolic trough solar collectors (PTCs) are one of the most mature and prominent available solar technologies for electricity generation and heat process applications. Most of the commercial PTC plants are currently based on synthetic oil as heat transfer fluid. In order to reduce the electricity cost and improve the overall efficiency, Direct Steam generation (DSG) emerged as promising option for PTC technology with lower environmental impacts. However, the use of water/steam as heat transfer fluid may lead to a more complex thermo-hydraulic process. Moreover, the realistic non uniform solar flux applied on the absorber tubes may provoke a thermal stress on these tubes and cause the damage of the heat collector element. The focus of this work is to develop a comprehensive optical and thermo-hydraulic model to determine the temperature and pressure drop in the DSG process taking in consideration the effect of the non-uniform heat flux distribution due to the concentration of the sunlight. A numerical-geometrical method is used to determine the solar flux distribution around the absorber tube with high accuracy. A heat transfer model is developed to predict the heat transfer characteristics of the different flow regimes in the DSG loop. The numerical model is validated with experimental data from DISS test facility and other available models in the literature.