Transient heat transfer of deforming droplets at high Reynolds numbers

A numerical study of heat transfer enhancement due to the deformation of droplets at high Reynolds numbers is described. The two phase-flow has been computed with a 3D DNS program using the volume-of-fluid method. The droplets are deformed because of the surrounding gas stream especiady due to a sudden rise of flow velocity from zero to U-i. As the governing non-dimensional parameter the Weber number of the droplets has been varied between 1.3 and 10.8 by assuming different surface tensions at Reynolds numbers between 360 and 853. The dynamical behavior of the droplets as a function of the Weber and the Ohnsorge number are in good agreement with experimental results from the literature. At the highest Reynolds number Re = 853, a signifivant dependency of Nu on We has been found The comparison of a Nusselt number computed with'the real surface area with a Nusselt number computed with the spherical surface area shows that the heat transfer increases not only due to the droplet motion but also due to the larger surface area of the deformed droplet.