An ammonia flash break-up model based on bubble dynamics with force and energy analysis on droplet

Abstract

Ammonia flash break-up model was developed using bubble dynamics based on force analysis of surface tension and pressure forces in this study. The initial bubble radius was calculated by modifying bubble number density equation considering the superheat degree with assuming a single bubble in the droplet. The Rayleigh–Plesset equation with compressibility factor was employed to calculate bubble growth in the liquid ammonia droplet. Droplet disintegration was predicted by force analysis. The velocity change by flash break-up was assumed to be a product of the surplus energy between the surface-energy change and the pressure work, and the bubble growth rate. The simulation results were compared to results in a previous experimental study of ammonia spray behavior. The time constant of the thermodynamic breakup model was added to simulate the flash boiling condition that induces rapid spray changes. In this study, the time constant 12 is used through the verification process. Compared with previous experimental results of ammonia flash boiling spray, the proposed flash breakup model was superior in predicting radial spray development by the flash boiling compared to the conventional aerodynamic breakup model.