CT-10 Vertical Intube Condensation of Mixtures and Pure Components in the Presence of Noncondensables-Data and RPM Improvement

Z. H. Yang

This report presents an improvements to the HTRI Resistance Proration Method (RPM) for condensation of mixtures and pure components in the presence of noncondensable gases inside vertical tubes; supporting data are also provided. HTRI conducted more than 500 data runs on the Vertical Intube Condensation Unit (VICU) in 1995 and 1996. With noncondensable gases present, six fluids—p-xylene, propylene glycol, steam, isopropanol, p-xylene/n-pentane mixtures, and p-xylene/n-pentane/n-heptane mixtures—were condensed over a wide range of conditions. Inlet noncondensable gas mole fractions varied from 0.15 to 0.85, and test pressure from vacuum (2.0 psia (13.79 kPa)) to 94.0 psia (648.1 kPa). Condensation flow regimes ranged from mist-annular flow to the region of transition from shear-controlled flow to gravity-controlled flow (Cgt £ 0.6). We used these data to evaluate the current RPM for vertical intube condensation.

Results of the data analysis show that the current method overpredicts the heat transfer coefficient by about 10 to 50 percent in cases of condensation with a noncondensable gas concentration mole fraction > 0.5 (yg > 0.5 mole fraction) and a condensate Reynolds number < 2000. HTRI has developed an improved RPM based on these new data. This improved method, which includes increased diffusion resistance from the noncondensable gas, predicts the condensation heat transfer coefficient for HTRI data and literature data within ± 25 percent accuracy.