Evaluation of Unity Lewis Number Assumption in Modeling of Water and Fuel Droplets Evaporation

Over the recent decades, spray systems have been widely utilized in a variety of applications within the areas of engineering. In this regard, studying the evaporative behavior of droplets in spray can give us a good view point. One of the most common assumptions in droplets’ evaporation is to consider the Lewis number to be unity. In this paper the correctness of this assumption has been evaluated for water and n-Heptane single droplets. The results for droplets’ evaporation trend have been compared with some relevant experimental and numerical data. Evaporation time and droplets’ temperature have been investigated in both conditions. According to obtained results, although the unit Lewis number is not a good assumption for studying n-Heptane droplet evaporation, this assumption gives acceptable results for predicting the water droplets evaporation. Moreover, by assuming the unity Lewis number for water droplet, the calculated temperature of the droplet is close to wet bulb temperature of air.