Influence of orifice in entropy generation and exergy analysis under transient condition for large diameter natural circulation loops

Stable power generation is of concern due to instability in NCL. The entropy generation analysis in a 38.89 mm diameter loop identified the flow reversals by a drop in its value after a peak. Orifice plates and operating procedures lead to a change in threshold value. During unsteady state, the least entropy generation was observed with β = 0.77. At higher power, constant power generation is possible with low orifice as it exhibits better exergy efficiency. The entropy generated due to friction was negligible compared to that by heat transfer.