Computational Heat Transfer and Two-phase Flow in Miniature Tubes

Keywords:
CFD, level sets, heat transfer, micro tubes

Abstract:
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.

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Nanotech 2006 Conference Program Abstract