Numerical Prediction of Dropwise Condensation Performances Over Hybrid Surfaces, Under the Action of Gravity and Vapor Shear

Abstract

A Lagrangian model following the history of every droplet belonging to an evolving droplets population, originally developed to simulate pattern evolution in the framework of in-flight icing phenomenon, is used in order to simulate dropwise condensation over different shaped micro-structured surfaces. Both the mechanical and the thermal energy balances are solved for every droplet, allowing to predict droplet velocity and condensing flow rate. Coalescence phenomenon is also implemented. The model in the present form is an evolution of the code presented at ICNMM 2019, introducing the effect of vapor shear, a physical model of the evolution of the dynamic contact angle during droplet growth and a prediction of condensing flow rate through the solution of thermal energy balance, thus taking into account the influence of the droplet size. Shared memory parallelization is also carried out decomposing the computational domain into different subdomains, allowing the efficient simulation of a larger number of droplets. Here, the model is validated and used to predict the heat transfer performance of hybrid condensation surfaces, both plane and curved, under the action of both gravity and vapor shear. Starting from literature proposals, several patterns, each characterized by a complex composition of patches with different wettabilities, are numerically investigated and the configuration ensuring the best heat transfer performance and liquid drainage is identified. The sensitivity of the solution with respect to the uncertainty on the estimate of some parameters, such as nucleation density, is also discussed.