Modeling of annular and intermittent flow condensation in micro- and mini- channels with experimental validation

摘要

Mechanistic models for predicting condensation heat transfer in the annular and intermittent flow regimes are presented and compared with data for different working fluids (R134a and R245fa) over a range of mass fluxes, saturation temperatures (30 ≤ T_(sat) ≤ 50 °C), saturation-to-wall temperature differences (1.5 < △T < 2.5 K), and channel geometries. The annular flow model is based on a laminar assumption and is applicable to arbitrarily shaped micro- or minichannels. Model predictions are validated using experiments focusing on low mass fluxes (G ≤ 100 kg m~(-2) s~(-1)), for which there are few analytical models or experimental data. The intermittent model developed here is also validated based on similar experiments. The annular model is found to be applicable for G ≤ 100 kg m~(-2) s~(-1), Re_δ < 61 (square), and Re_δ < 125 (circular), while the intermittent model is applicable for G ≤ 150 kg m~(-2) s~(-1) and 78 < Re_δ < 365.