Saturated/subcooled flow boiling heat transfer inside micro/mini-channels: A new prediction correlation and experiment evaluation

In this study, a new general heat transfer correlation was developed for predicting the saturated/subcooled flow boiling heat transfer coefficient in micro/mini-channels. The collected database included 4250 data points, which covered eleven different working fluids. These included deionized water, new electronic fluorinated solutions, and refrigerants, among others. The temperature range of the experimental operation was from 0 to 100 °C with a saturated pressure of 101 to 775 kPa. The hydraulic diameter of micro/mini-channels varied from 0.1 to 3 mm, and the liquid sub-cooling was between 0 and 80 K. The database included various operation conditions, such as mass flux, heat flux, vapor quality, and reduced pressure. The liquid and vapor Reynolds numbers were calculated based on the hydraulic diameter. Six existing flow boiling heat transfer correlations were employed to evaluate the present data points in micro/mini-channels. However, it was observed that these correlations were unable to predict the present data points accurately due to high liquid sub-cooling and heat flux. Therefore, a new prediction correlation based on the present database was developed by dividing flow boiling into three stages, including subcooled boiling, developed nucleate boiling and nucleate boiling deterioration. This new prediction model can predict more than 80% of data points within ±30% error band.