The series of analyses was conducted by Satoshi Maeda in our Engineering Department. In the model of Lee shown in Figure 2, it is assumed that evaporation occurs when the liquid temperature of each fluid element is higher than the saturation temperature (boiling point) and condensation occurs when it is lower than the saturation temperature, and the phase change volume is calculated in consideration of the densities of the gas and liquid. These increase and decrease can be represented in a model established by Lee (a series of basic equations concerning evaporation and condensation proposed in 1980) in Los Alamos National Laboratory in the U.S., assuming the local balance.
At the same time, increase and decrease of the latent heat and volume (density difference between a liquid and a gas) is considered. Therefore, consider a macro approach instead.Īs shown in Figure 1, a boiling flow is analyzed with the VOF method for free surface flow analyses and the phase change between evaporation and condensation is modeled with increase and decrease of the F value (volume fraction of fluid). In a micro approach of a boiling flow, modeling of generation of bubble cores on the heat transfer surface and growth/separation of these bubbles is required, however, there is no analysis method that has been established universally. They are complex flows whose flow pattern varies according to the temperature difference between the liquid and the heat transfer surface, etc. Boiling flows are widely used in industrial fields such as heat exchangers and cooling systems. However, there are multi-phase flow phenomena for which analysis is still difficult. By using recent computers that have evolved dramatically, issues concerning multi-phase flows have come to be solved by fluid simulation analyses. Boiling flow analysis (free surface flow analysis with phase change)īoiling flow analysis is an example of gas-liquid two-phase flow analyses.
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