R134a in Microchannel Heat Sink Flow Boiling Instability Experimental Study

This paper presents experimental investigations on the unstable boiling of low-boiling point refrigerant R134a in microchannel heat sinks. The pressure drop fluctuations and instability are analyzed quantitatively by varying the heat flux density, mass flow rate, and saturation temperature. The results show that higher heat flux densities result in more significant pressure drop oscillation instability. However, an increase in mass flow rate can mitigate the instability. The saturation temperature exerts a substantial influence on the flow instability. Increasing the saturation temperature delays the onset of flow instability, but the subsequent instability becomes more severe. The instability coefficient R, as a predictive indicator of flow instability, is defined as R=1, marking the boundary of instability. The study also explores the influence of subcooling and phase change on instability, offering theoretical insights into the thermal management of microchannel heat exchangers.