Flow boiling critical heat flux in MICRO-scale heat sinks and comparison with correlations

Abstract

The growing demand for high-performance miniature electronics is forcing the heat dissipation requirements to increasingly higher levels. Flow boiling in micro-scale heat exchangers is a good choice for cooling these high heat flux devices. In such systems, the prediction of critical heat flux (CHF) is a crucial aspect in thermal-fluid system design, as it defines the maximum limits of thermal management systems. Different CHF mechanisms were identified and studied in the literature, leading to the development of numerous correlations. However, significant discrepancies still exist among these studies. The present study investigated experimentally the critical heat flux of HFE-7100 in single and multi-channels heat sinks. Saturated flow boiling experiments were conducted at inlet pressure of 1, 1.5 and 2 bar, inlet subcooling of 5 K and 10 K and mass flux of 100–750 kg/m2 s. The wall heat flux was increased gradually until the CHF was reached at 435 kW/m2 and 308.6 kW/m2 for the single channel and the multi-channels, respectively. Events leading to the CHF occurrence were identified in the present study using a high-speed, high-resolution camera and thermocouple readings. The present results were also used to evaluate eight flow boiling CHF correlations, with some found to agree with the current experimental data. In the present study, both mass flux and inlet pressure had a noticeable effect on the CHF phenomenon. However, the effect of inlet pressure remains to be properly evaluated and included in these correlations.