Pressure Drop Analysis of Steam Generation Parabolic Trough Plants

Direct steam generation (DSG) in parabolic trough plants has the potential to be more cost-effective than oil based systems. The produced steam can directly be used for process heat applications. Within the P3 project such a DSG plant of 108 m2 of Solitem’s PTC1800 has been installed on the roof of the building of the company Alanod. In the present paper, a two-phase pressure drop analysis of typical steam generation plants with different layouts is presented. A static model has been developed for this purpose. Parametric studies have shown that, due to the elevated pressure drops, the length of a collector loop within a DSG plant is limited. Consequently, in bigger plants collector loops need to be installed in parallel. In each collector loop so-called Ledinegg instabilities occur. When collector loops are installed in parallel, there are additional flow instabilities. Those parallel flow instabilities occure due to shading of one or several collector loops. Changing pressure drops lead to an unfavourable reallocation of mass flows. In the worst case, steam is superheated and the collectors get damaged due to high temperatures. Ledinegg and parallel flow instabilities can both be reduced by installing an additional flow resistor at the collector loop’s inlet.