Subcooled flow boiling in multiple parallel rectangular micro-channel heat sink: Development of heat transfer correlation

This study experimentally evaluated and presented the heat transfer performance of FC-72 flow boiling in a rectangular micro-channel heat sink under subcooled conditions. The hydraulic diameter of the rectangular micro-channel under investigation is 666 µm, and the heat sink has twenty-four parallel mico-channels machined on an oxygen-free copper block. The width and height of the rectangular micro-channel are 400 µm and 2000 µm, respectively. The experimented mass flux and fluid inlet temperature to the heat sink range between 103–1026 kg/m²s and 20–50℃, respectively. Furthermore, a consolidated subcooled flow boiling database is developed by using the FC-72 flow boiling data of the present experimental study and the subcooled flow boiling database with four different micro-channel heat sinks with HFE-7100 as the coolant by Lee and Mudawar (2008). Nine prominent predictive heat transfer correlations for subcooled flow boiling are methodically assessed and contrasted against the combined database comprising 631 data points. The evaluation resulted in significant variations in the predictions by the correlations with the current consolidated database. The conventional correlations in the literature for flow boiling under subcooled conditions are inadequate for foreseeing the heat transfer during subcooled flow boiling in the micro-channel heat sink as they are developed based on conventional tubes and annuli with channel hydraulic diameters greater than 3 mm. A new subcooled flow boiling heat transfer correlation rooted in dimensionless group terms is then developed from the consolidated database. Compared to prior correlations, better predictive performance is observed for the new subcooled flow boiling correlation against the consolidated database. The newly developed correlation has a mean absolute error of 21.9%, with 74.9% of data points forecasted within ±30%.