Computational Analysis of a Subcooled Boiling Flow with a One-group Interfacial Area Transport Equation

Abstract

For a multidimensional analysis of a two-phase flow, a computational fluid dynamics (CFD) code was developed with the implementation of an interfacial area transport equation that is beneficial for dynamically estimating the interfacial area concentration (IAC). The code structure was based on the two-fluid model and the Simplified Marker and Cell (SMAC) algorithm. The SMAC algorithm was extended to a two-phase flow simulation with a phase change. Various well-known constitutive models regarding boiling, condensation, and nondrag forces have been implemented into the code. To verify the robustness of the code to predict wall boiling and void propagation phenomena, a subcooled boiling test in a vertical annulus channel was analyzed as a benchmark problem. As the analysis results, a model for bubble departure diameter on the heated wall was identified as the principal factor for subcooled boiling phenomena, and the limitation of the current departure diameter models under a low-pressure condition resulted in a deviation of the void fraction and IAC when compared with the results of the experiment. It is necessary that the research on the interfacial area transport equation focuses on modeling reliable source terms for the boiling mechanism as a future work.

Multi-phase mixture modelling of nucleate boiling applied to engine coolant flows

“…Bae et al [5] benchmarked their full EulerEuler (two-fluid) multi-phase model with an interfacial area equation using the experiment from the Seoul National University. The sub-cooled boiling of water The inner and outer annulus radii were R in = 9.5 and R out = 20 mm.…”

“…The closures for the remaining model parameters have been selected based on the assessment of the existing empirical closures reported in literature. For the bubble diameter, the correlation of Tolubinsky, see [5], is modified by introducing an adjustable factor C bw (C bw = 0.6 in the original correlation):…”

“…The bubble release frequency and nucleation site density are calculated from Cole's and Lemmert and Chwala's correlations (see for example [5]), respectively:…”

“…In the past, the majority of published CFD predictions of boiling flows employed the RPI model of Kurul and Podowski [1] for interfacial transfer closures. It was validated against high pressure flows but later some authors [3,4,5] adopted this model for low pressure boiling flows. Model improvements have been proposed by [6,7], while the model extension to conditions close to CHF was reported in [8].…”

“…In the majority of CFD simulations [3][4][5]9, 10] the boiling model has been coupled with multi-fluid conservation equations where individual velocity, temperature and other field variables can be solved for each phase. The exception is Bo's work [11], where the homogeneous multi-phase mixture (single fluid) approach was used in conjunction with the author's own mass transfer model.…”