A composite model for nucleate boiling heat transfer in a slush nitrogen pool

The pool boiling of slush nitrogen (SlN(2)) with various solid volume fractions at subatmospheric pressures is studied to establish a semi-empirical model considering the effects of phase-change solid nitrogen (SN2) particles on convective heat flux and boiling heat flux. The convective heat flux is studied with the modified correlation based on Sindt's fitting, while an improved correlation based on Rohsenow correlation with the dimensionless form of wall superheat in the range of 0<Ja(& lowast;)rho(& lowast;0.14)<0.04 is obtained for the boiling heat flux. With the increasing wall superheat, the enhancement weakens till vanishes at the transition point. This point marks the separation between low- and high-heat-flux regions, where the probability of SN2 invading to thermal boundary layer diminishes to 0 %. The low-heat-flux boiling correlation considers the heat transfer enhancement due to SN2 concentration while the high-heat-flux one ignores the impact of SN2. As the components of SlN(2) nucleate boiling model, the convective and boiling heat flux both show the accuracy of +/- 20 % with experiments. Upon analyzing the boiling curves of SlN(2) with various solid volume fractions, SlN(2) outperforms LN2 in coolant efficiency at moderate heat load.