Liquid-film thickness during flow boiling of pure hydrocarbons and their mixtures

摘要: The present study concerns an experimental investigation of the liquid-film thickness and void fraction during flow boiling of hydrocarbons and their zeotropic mixtures. High-speed flow images were also gathered. Experiments were performed for R600a, R290, R1270, R600a/R290 (70/30 M fraction) and R600a/R1270 (75/25 M fraction) in a horizontal stainless-steel tube with an internal diameter of 9.43 mm. Liquid-film thickness and flow footage were gathered in an adiabatic section, 50 mm downstream the heating section. The saturation temperature was kept at 5 °C, mass velocities ranged from 50 to 250 kg/m2s, vapor qualities from 0.07 to 0.81, and heat fluxes from 5 to 80 kW/m2. The experimental data comprehends annular flows, including results for the intermittent dryout-rewetting phenomenon. The rewetting front was found to be composed of a two-stage wave. Initially it approached the dry wall, increasing …