Experimental Investigation of the Filling and Draining processes of drainback systems (part 3)

摘要

An experimental setup was constructed for the investigation of the filling and draining processes of a drainback system. Corrugated stainless steel (CSS) pipes in combination with transparent plastic hydraulic components (collector, heat storage) were applied in this study. CSS pipes are flexible, economically feasible and easy to install. However, sagging and the corrugated shape might be obstacles for a complete filling and proper draining. Therefore, several experiments with different diameters of CSS pipes (DN 12, DN 16, DN 20, DN 32) were performed. The recommended lower threshold of the flow rate for siphon establishment in hydraulics with CSS pipes has been experimentally obtained. Regarding the draining process a typical profile comprising of the emptying time and maximal draining flow rate is summarized. It is showed that the draining proceeds always in the same way (profile, emptying time) for the same hydraulics regardless of the adjusted flow rate during operation. The impact of the pumps on the draining process is also demonstrated. Finally a burst test was conducted, that proved a safe operation even by phase change of the remaining water. Conclusions are presented in details in this paper.