Flow boiling experiments for CHF evaluation under downward-facing heating including flow visualization: Effects of pressure, orientation, mass flux, and local quality

•Systematic CHF experiments were conducted on orientation angle, pressure, local quality, and mass flux.•The higher orientation, the higher pressure, and the faster mass flux condition made the higher CHF.•The CHF tendency by local quality was shown to vary with orientation angle.•Through flow visualization, the vapor behavior that depends on the parameter change was observed, and it was confirmed that the vapor behavior was directly related to CHF.