An analysis of the d-law departure during droplet evaporation in microgravity

The d²-law validity during n-decane droplet vaporization in microgravity environment is examined experimentally. Two sets of experiments are performed, under normal and microgravity, in stagnant hot atmospheric environment. The environment temperature is varied in the range up to 967 K. The droplet is suspended onto the cross point of two micro-fibers of 14 μm in diameter. This technique enables to greatly minimize the effect of fiber on droplet heat and mass transfer. The results show that, for ambient temperatures below approximately 950 K, departure from the d²-law is observed during droplet vaporization in microgravity environment. In addition, the droplet lifetime is longer in microgravity than in normal gravity under the same ambient test conditions. However, for temperatures exceeding approximately 950 K, the experimental results demonstrate that the d²-law holds throughout the entire droplet lifetime, and the mass transfer rate is identical in both microgravity and normal gravity environments.