A GENERAL CORRELATION FOR SATURATED AND SUBCOOLED FLOW BOILING IN TUBES AND ANNULI, BASED ON A NUCLEATE POOL BOILING EQUATION

Recent accurate correlations for predicting the heat transfer coefficient in saturated flow boiling all contain an empirical boiling number correction. The original idea behind the boiling number correction was to allow for the enhancement of the forced convective heat transfer mechanisms arising from the generation of vapour in the boundary layer next to the wall. However, the presence of the boiling number term appears to prevent application to subcooled boiling, throwing doubt on the physical basis of the correlation. This paper shows that the convective term in the correlation should have a Prandtl number dependence. In this way an accurate predictive method covering a very wide range of parameters is constructed with an explicit nucleate boiling term and without boiling number dependence.