Numerical model of bubble shape and departure in nucleate pool boiling

In this work, we have developed an improved numerical model to simulate the dynamics of bubble shape and departure in nucleate pool boiling at a heated surface at low and high superheats. The numerical model computes the bubble shape solving Young-Laplace equation directly and considering the effect of radial variation of film pressure in our numerical model of microlayer evaporation. The numerical results of bubble shape and departure have also been compared with the CFD-results in literature and with the results of our experiments. For a spherical bubble, the direct numerical integration of Young Laplace works very well in computing the bubble shape. For a non-spherical bubble, an approximate analytical solution for bubble shape proposed in literature works better than the numerical solution of Young-Laplace equation. The shape of a bubble has been found to be influenced by superheat and Bond number Bo. We have also analyzed the forces acting on the bubble surface while departing the heated surface. The Young-Laplace equation seems to include the growth force to produce the hemispherical shape of non-spherical bubbles. A very low Bo results in a train of small bubbles that coalesce to a big bubble with increase in Bo. (c) 2021 Elsevier Ltd. All rights reserved.