Stability Improvement in Natural Circulation Loop using Tesla Valve – An Experimental Investigation

Abstract

Natural circulation loop works on the basic principle of thermosiphon effect, which doesn't require any external force to drive the fluid in a loop. Hence they are highly applicable in power industries where there are a source and a sink. However, the flow pattern in a single-phase natural circulation loop is quite unstable especially the horizontal heater horizontal cooler configuration which results in lower loop effectiveness. A lot of research has been carried out to study these instabilities and find a way to curb them. Techniques such as tilting of loop, use of nanofluids, adding flow resistances etc. have shown promising results. But they have their own practical constraints. Hence in the present experimental study, a Tesla-type passive valve is incorporated in natural circulation loop. Due to its presence, not only stability period is reduced (at least 90 s compared to non-Tesla loop) but also unidirectional flow is achieved. The Tesla valve performed better for a broad range of heater power (90-170W) and was also able to provide noticeable resistance to the flow when the loop was inclined by 2.5° in the opposite direction.