Hybrid Phase-Change Lattice Boltzmann Simulation of Vapor Condensation on Vertical Subcooled Walls

Abstract

Saturated vapor condensation on the homogenous and heterogeneous subcooled wall under gravity was numerically simulated by the improved pseudopotential phase-change multiple-relaxation-time (MRT) lattice Boltzmann (LB) method. Firstly, the phase-change MRT-LB method coupling finite different method (FDM) to solve the energy equation was verified by the D2 law of the droplet's evaporation, which improve the model could precisely realize the numerical simulation of phase change. Subsequently, effects of wall wettability and subcooling as well as the geometry structure of the heterogeneous on the dynamic behaviors of droplet's growth, coalescence and falling, temperature field and heat flux were investigated via the phase-change model. The resultsshow that for the homogeneous cooler wall, it is easier for dropwise condensation formation with decreasing the wettability of the subcooled surface, and the condensate droplets on the vertical surface are easier to coalesce and fall under the gravity. It was found that in the condensation process, the saturated vapor mainly converges near the triple-phase contact line and leads to the further growth of the condensate droplets, and there is a higher heat flux and much more isotherm folds around the triple-phase contact line than other regions. The subcooled wall with hydrophilic-hydrophobic spacing distribution is more conducive to dropwise condensation; at small subcooling, the transient average heat flux remains almost unchanged, and with the occurrence of condensation, the heat flux rapidly increases, but as wall subcooling increases further, the increases of the heat flux decreases, and when the degree of wall subcooling further increases, the transient heat flux decreases first and then increases.It also can be concluded that increasing the length of the hydrophilic spots on the heterogeneous wall, the dropwise condensation will be easier to form, but too much hydrophilic spots will not contribute to the fall of the droplets.

Copper-Based Superhydrophobic Nanostructures for Heat Transfer in Flow Condensation

“…Accordingly, the distance between hydrophilic islands affected both droplet growth rate and coalescence-induced droplet departure and was an important parameter for enhancing condensation heat transfer. In addition, the Lattice Boltzmann method has been applied in multiphase flows and phase change heat transfer. , Moreover, in recent studies regarding the Lattice Boltzmann phase change model, surfaces with heterogeneous mixed wettability, different wettability, and textured structures were considered for condensation heat transfer.…”

“…In addition, the Lattice Boltzmann method has been applied in multiphase flows and phase change heat transfer. 28,29 Moreover, in recent studies regarding the Lattice Boltzmann phase change model, surfaces with heterogeneous mixed wettability, 30 different wettability, 31 and textured structures 32 were considered for condensation heat transfer.…”

Numerical hybrid thermal MRT-LBM for condensation and boiling phenomena on horizontal walls of different wettability

“…The small dimensional requirements associated with the cooling of electronic equipment have produced new challenges at the micro and mesoscale levels in boiling and condensation phenomena as well (Rohsenow 1951, Moore and Mesler 1961, Nukiyama 1966, Collier and Thome 1994, Chaabane et al 2017, Huo and Rao 2018, Alipour Lalami et al 2019, Pawar et al 2019, Mondal and Bhattacharya 2021, Xu and Zhou 2021. Different models are adopted to study these problems (Bhardwaj and Dalal 2017, Qian et al 1992, Hou et al 1997, Zou and He 1997, Quan et al 2011, Gong and Cheng 2012, Jung et al 2014, Kim et al 2016, Chaabane et al 2017, Cheng et al 2017, Huo and Rao 2018, Rao et al 2018, Pawar et al 2019, Zhao et al 2020. They offer many advantages, including clear physical illustrations and easy implementation of boundary conditions.…”

Biphilic Surfaces with Optimum Hydrophobic Islands on a Superhydrophobic Background for Dropwise Flow Condensation

“…In addition, noteworthy efforts have been recently made in developing numerical models to investigate hybrid surfaces for their thermal performance and droplet dynamics. 53 A lattice Boltzmann phase change model for surfaces with heterogeneous wettability 54 and textured structures 55 was also considered.…”