Mapping the amplitude and frequency of pressure drop oscillations via a transient numerical model to assess their severity during microchannel flow boiling

Flow boiling in microchannel heat sinks offers effective cooling for high-power electronics devices and compact heat exchangers in many other industrial applications. However, flow boiling instabilities, in particular pressure drop oscillations, can occur in these heat sinks and may reduce their performance by causing premature initiation of critical heat flux (CHF) or deterioration of the heat transfer coefficient. Predicting the occurrence and severity of pressure drop oscillations is hence important to ensure reliable operation. We perform stability analysis using bifurcation theory to determine the effect of various operating and geometric parameters on these oscillations in microchannel heat sinks. The analysis identifies the unstable (where pressure drop oscillations occur) and stable regions of operation based on the mass flux, heat input, and amount of inlet restriction. As the stability map does not yield information regarding the severity of oscillations in the unstable region, the effects of these parameters on the amplitude and period of pressure drop oscillations are also assessed via a transient numerical model. Surveying these parameters over the unstable region allows assessment of potential performance reductions of the heat sink due to pressure drop oscillations.