Recent trend in research of critical heat flux (CHF) in boiling has been reviewed for pool boiling and simpler boiling systems from macro-and microscopic points of view in order to grasp fundamentals and to enhance better understanding of the CHF. A CHF model based on heat balance in macrolayer can provide a good clue for analyzing and deriving CHF correlation but does not include any information on surface conditions. In addition, a way to improve the CHF can be thougth to be progressing steadily in light of understanding of macrolayer. Another model related to microlayer has been developing and may be expected to bridge between nucleate and transition pool boilings. There seems for this model to show no way how liquid is supplied into heated surface and generated vapor escapes from the microlayer.
