Numerical simulation of direct solar steam generation collectors with parabolic troughs

The direct steam generation (DSG) in parabolic trough collectors is a promising option, which provides many features superior to the conventional solar thermal electricity generation. In this study the stratified flow in DSG collectors is analyzed and numerically simulated based on the separated flow model to investigate the effects of main parameters on stratified flow, the flow properties and pressure drop. In the numerical calculation process, the receiver is divided into several segments and mass and energy balance are applied in each segment. The results indicate that the stratified flow appears in low mass flow rate, the void fraction and stratified angle have great changes in the initial of two phase flow regime. In two phase flow, the steam velocity is directly influence the heat transfer of the steam phase, and the increase of the difference between steam velocity and liquid velocity eventually lead to the temperature difference and the instability flow due to the phase interfacial forces.