Lattice Boltzmann Simulation of Optimal Biphilic Surface Configuration to Enhance Boiling Heat Transfer

Abstract

To study the processes of boiling on a smooth surface with contrast wettability, a hybrid model was developed based on Lattice Boltzmann method and heat transfer equation. The model makes it possible to describe the phenomena of natural convection, nucleate boiling, and transition to film boiling, and, thus, to study heat transfer and the development of crisis phenomena in a wide range of surface superheats and surface wetting characteristics. To find the optimal configuration of the biphilic surface, at the first stage a numerical simulation was carried out for a single lyophobic zone on a lyophilic surface. The dependences of the bubble departure frequency and the departure diameter of the bubble on the width of the lyophobic zone were obtained, and its optimal size was determined. At the next stage, the boiling process on an extended surface was studied in the presence of several lyophobic zones of a given size with different distances between them. It is shown that in the region of moderate surface superheat, the intensity of heat transfer on biphilic surfaces can be several times (more than 4) higher compared to surfaces with homogeneous wettability. Based on numerical calculations, an optimal configuration of the biphilic surface with the ratios of the lyophobic zones’ width of the order of 0.16 and the distance between the lyophobic zones in the range of 0.9–1.3 to the bubble departure diameter was found.

Modelling of pool boiling on the structured surfaces using Lattice Boltzmann method

“…As it was described previously [10], at low wall superheat the heat transfer occurs in the mode of singlephase natural convection. That is why the boiling curves <q>(ΔT΄) approximately do not depend on the surface configuration.…”

“…The regime with N = 5 caverns with size h = l = 0.3 mm was considered. As it was shown and discussed in previous paper [10], the pitch size between the hydrophobic partens should be of the order of the bubble departure diameter to achieve heat transfer enhancement. In this section p = 4.8 mm was used, which is slightly exceeds mean value of the bubble departure diameter Dd ≈ 3 mm for our conditions.…”

“…The following model is used that was thoroughly described elsewhere [9,10]. Only the main features of this model shall be presented below.…”

“…It is based on the calculation of the distribution function of pseudoparticles over discrete velocities and space. In recent years, this method has become popular in modelling liquid boiling [6][7][8][9][10]. One of the features of the method is the possibility of modelling the process of vapour phase generation without specifying additional initial conditions based on empirical relationships.…”

“…The effect of contrast wettability on the smooth surface was considered in previous papers [9,10]. The aim of the work is to determine the optimal configuration of a structured surface in terms of heat transfer enhancement at boiling using a hybrid model based on the Lattice Boltzmann method and solving the heat transfer equation in a two-phase medium in a wide range of wall superheats.…”