A new predictive tool for saturated critical heat flux in micro/mini-channels: Effect of the heated length-to-diameter ratio

This paper verified the macro-to-mini-scale criterion BoRe10.5=200 because data points where BoRe10.5⩽200 and BoRe10.5>200 show very different trends for the entire database (1672 data points). Boiling number at critical heat flux (Blchf) decreases greatly with heated length-to-diameter ratio (Lh/dhe) when Lh/dhe is small while a relatively smooth trend occurs with large Lh/dhe values. The paper proposed a threshold value of Lh/dhe = 150, beyond which Lh/dhe presents negligible effect on saturated critical heat flux. The combined dimensionless number WemCa10.8 was introduced to analyze saturated critical heat flux, which represents the significance of inertia, surface tension, and viscous force, without considering gravitational force for the region where Lh/dhe > 150 and BoRe10.5⩽200. In addition, a new predictive tool for saturated critical heat flux in micro/mini-channels was obtained, predicting almost 95.5% of the non-aqueous data and 93.5% of the water data within a ±30% error band.