Authors: D. Lakehal and C. Narayanan
Affilation: ASCOMP, Switzerland
Pages: 621 - 624
Keywords: CFD, level sets, heat transfer, micro tubes
We will report on our recent advances made in predicting this class of flow, using the Level Set approach, in which we have incorporated phase-change capabilities, surface tension and triple-line dynamics models based on the Young’s unbalanced forces. We will focus on the tremendous role played by flow regime in controlling heat transfer. We will show that a tiny change in the gas-phase Reynolds number can change a bubbly flow regime into a bubbly-slug flow regime, which in turn leads to an appreciable increase in local heat transfer. The 2D axisymmetric simulations were performed in a 1mm diameter tube heated at the surface, in which air bubbles were then injected into a water stream. The computational strategy combines the unsteady Navier-Stokes equations for the flow and Level Sets for interface dynamics. These novel methods were found to accurately predict various multi-fluid micro-flow phenomena. Figure 1 shows predicted bubbly/slug flow regime. The heat removal rate is shown to increase as compared to the single-phase flow regime (upper panel), and was found to be higher than the bubbly flow regime (see isocontours of temperature –blue: low; red: high). The presence of phase change will add to the heat transfer removal rate.