Abstract
The enhancement mechanism of forced convective flow on dropwise condensation over a cold spot is numerically investigated by two-dimensional hybrid thermal lattice Boltzmann (LB) model based on the Shan-Chen pseudopotential LB model. After validating the present LB model, dropwise condensation over a cold spot as the nucleation region is simulated. The well-known power law for the growth of a single condensing droplet is demonstrated. Finally, the simulation of dropwise condensation considering the convection flow or not is carried out in the constant contact radius (CCR) mode. Using the CCR model, the effect of contact angle can be also investigated. The result of streamline field indicates that the forced convectional flow complicates the internal flow of droplet and main flow. The dragging force from main flow changes the size of two symmetric vortices inside the droplet. And the channel flow is also strongly influenced by the suction effect caused by condensation at the three phase contact line. By comparison, the heat transfer enhancement of the superimposed flow is not worth mentioning. The present study illustrates the mechanisms of dropwise condensation under forced convectional flow.
Highlights
Because of the complicated dynamic behavior of droplets, dropwise condensation becomes to be a typical case of multiphase flow involving vapor-liquid phase change, free surface flow, coupled heat and mass transfer, multi-scale feature, and interfacial behaviors
The enhancement mechanism of forced convective flow on dropwise condensation over a cold spot is numerically investigated by two-dimensional hybrid thermal lattice Boltzmann (LB) model based on the Shan-Chen pseudopotential LB model
The fluid flow and temperature field is solved by the pseudopotential LB model and finite difference scheme, respectively
Summary
Because of the complicated dynamic behavior of droplets, dropwise condensation becomes to be a typical case of multiphase flow involving vapor-liquid phase change, free surface flow, coupled heat and mass transfer, multi-scale feature, and interfacial behaviors. A popular model used in LB model is the pseudopotential LB method proposed by Shan and Chen [4, 5] because of its computational efficiency and straightforward algorithm. In this model, the phase separation is realized spontaneously by the introduced short-range intermolecular interaction based on a potential function. For phase-change heat transfer, the thermal pseudopotential LB model is developed by devising the temperature distribution function [12,13,14,15,16]. The main objective is to understand the mechanism of dropwise condensation in the forced convective laminar flow
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