ADVANCED CONTROLS OF ORGANIC RANKINE CYCLE FOR HIGHLY TRANSIENT FLUCTUATIONS DURING INITIAL STARTUP

asme-orc2015 Tracking Number 66

Organic Rankine Cycles are typically utilized where steady heat source and condensing conditions prevail. In highly transient cases, the working fluid often undergoes violent phase transition within the evaporator. The resulting forces are experienced by the heat exchanger, expander, and associated piping. This ultimately results in premature and catastrophic component failure. This paper discusses pressure and flow instability which occurs during initial startup of an ORC. The instability is a result of a nonlinear pressure field within the evaporator interacting with the pressure source (centrifugal pump.) The phenomenon is characterized by a rapid oscillation in pressure and flow and resembles similar effects observed in low pressure boilers; the so called Ledinegg instability. Experimental data is examined and various methods for reducing or eliminating this effect are presented.