Experimental study and the development of an improved correlation with consideration of Dryout region for R410A flow boiling heat transfer in micro-channels

In this study, a testing facility was established to measure the heat transfer coefficient and pressure gradient of R410A flow boiling in horizontally oriented micro-channel flat tubes with a hydraulic diameter of 0.778 mm. The experimental conditions covered mass flux from 150 to 250 kg/m²s, heat flux from 10 to 20 kW/m², and saturation temperatures of 5, 10, and 15 °C. The effects of mass flux, heat flux, and saturation temperature on the heat transfer coefficient and pressure gradient were discussed. The results indicated that mass flux, saturation temperature, and heat flux had significant impacts on the heat transfer coefficient; pressure gradient increases with increasing mass flux and decreasing saturation temperature. The tested data were compared with empirical correlations, and Zhang et al.'s correlation is recommended for predicting the frictional pressure gradient within the experimental range of this study, while Kim and Mudawar's correlation is recommended for predicting the heat transfer coefficient in the pre-dryout region. Additionally, to improve prediction accuracy and to ensure validity across both pre-dryout and dryout regions, Jige et al.'s method was employed to incorporate dryout effects into the Kim and Mudawar model, improving the mean relative percentage error in the dryout region from −81.49 % to −3.72 %.