CHF prediction model research for flat and hypervapotron heating surface in subcooled flow nucleate boiling

Based on fundamental nucleation boiling theory, nucleation site distribution and hot spot model, a theoretical critical heat flux (CHF) prediction model in subcooled flow boiling is presented in this paper. With the increase of heat flux, nucleation site density will finally approach the limit of site population. When the critical number of nucleation sites is reached in an area, it will cut off the supply of liquid for the central site, and then CHF emerges. In this paper, an improved hot spot model is proposed, which uses statistical bubble departure diameter and standard square shape. CHF prediction can be reasonably achieved based on fully developed boiling heat transfer curve, nucleation site density and distribution. Some related experimental data are referred and R134a subcooled flow boiling data on flat and hypervapotron test section are reported. Comparison results showed a good prediction of CHF.