Pressure fluctuation analysis for identifying the CHF approaching condition during subcooled flow boiling through a mini-channel

This study presents a new method for predicting the Critical Heat Flux (CHF) approaching condition in subcooled flow boiling based on pressure fluctuation analysis. Through experimental investigations, water flow in an upward direction was conducted within a mini-channel with one side heated to analyze the sequential boiling phenomena, including ONB (Onset of Nucleate Boiling), OFI (Onset of Flow Instability), and CHF. While ONB was determined using the slope of the wall temperature–heat flux, OFI was determined by considering the pressure drop through the channel and outlet pressure fluctuation. By analyzing the inlet pressure fluctuations, a new condition called “the CHF approaching condition” was introduced, which serves as a CHF precursor. The CHF approaching condition was found to be approximately 90% of the CHF value across all experimental scenarios. The proposed method provides an effective tool for predicting and preventing CHF, thereby reducing the potential risk of damage to the heating surface.