Effect of heat conduction on droplet life time and evaporation rate under forced convection at low temperatures

Abstract

Fuel droplet vaporization process involving heat and mass transfer holds key interest due to its application in wide range of energy systems. This manuscript presents the experimental and computational investigation of an isolated fuel droplet evaporation conducted in wind tunnel by suspending the droplet using supports of different sizes and materials. Different sizes of initial droplet diameter 1565–2775μm, ambient temperature 303–403K and varying ambient air velocity 0.4–2.7m/s allowed the investigated Reynolds number to be varying between 30 and 275. K-type thermocouples (df=76–812μm) and glass fibers (df=200–800μm) are used for fuel droplet suspension. Use of thermocouples allowed acquiring the temporal variation of droplet temperature. Both experimental and computational investigations were carried out to quantify the heat conduction to fuel droplet through droplet support and its effects on the droplet evaporation rates. Gradients of droplet evaporation rates are found to be changing for very small support sizes while extrapolated to obtain values for pure convection cases. MATLAB code based on mathematical model is developed to see the outcome of varying support size, support material, ambient temperature, ambient velocity and droplet size on the droplet evaporation process. The average over estimation of mean droplet evaporation rates in the absence of heat conduction for linear extrapolation are found to be 30% and 8% for thermocouples and glass fibers respectively at U∞=1.4m/s and varying ambient temperatures while using 0.008≤df2/do2≤0.035 for linear extrapolation.