Evaporation characteristics of single free-falling liquefied natural gas droplet under different ambient conditions based on the VOF method

The evaporation characteristics of droplets is a fundamental issue for accurate depictions of moving liquefied natural gas (LNG) droplets and constantly changing ambient environment owing to intense heat, mass transfer, and momentum exchanges. In this study, a modified droplet evaporation model is developed to investigate the evaporation behavior of a single free-falling LNG droplet under various ambient conditions. The proposed model captures the droplet interface and calculates the mass transfer rate through the vapor concentration gradient using the volume of fluid method integrated with a smooth function. Evaporation experiments were conducted on a single free-falling LNG droplet to capture the evaporation process. The results indicate that it is acceptable to ignore the effect of the Stefan flow of a single free-falling LNG droplet. This study also examined the impact of different ambient conditions on evaporation characteristics. The results indicate that the evolution of the droplet diameter is mainly influenced by the ambient temperature because it affects the thermal properties of the surrounding gas and the distribution of the boundary layer. The temporal characteristics of the Nu and Sh numbers generally stabilize after a period of rapid decline. This study provides a theoretical basis for understanding the evaporation mechanisms of LNG droplets.