Effect of noncondensable gas on the condensation of R-123 on enhanced tube geometries Conference Paper uri icon

abstract

  • Data showing the effect of several concentrations of non-condensable gas on the condensation of R-123 - the scheduled non-CFC replacement for R-11 - are presented for bundles of four enhanced tube geometries: a 1,024-fpm (26-fpi) tube; a low-fin, 1,475-fpm (40-fpi) tube; and two enhanced tubes, designated the Tu-Cii and the G-SC. The test bundles are five columns wide by five rows deep in a staggered tube arrangement with a 22.2-mm (0.875-in.) horizontal pitch and a 19.1-mm (0.75-in.) vertical pitch. Tests for the effect of noncondensable gases were conducted at four concentrations of nitrogen by volume: 0.5%, 1.0%, 2.0%, and 5.0%, at four heat fluxes between 18,000 W/m2 (5,700 Btu/h·ft2) and 34,000 W/m2 (10,780 Btu/h·ft2). All the data were obtained at a saturation temperature of 35°C (95°F). The Tu-Cii generally performed the best at noncondensable gas concentrations up to 5.0%, followed by the 40-fpi, G-SC, and 26-fpi geometries. The Tu-Cii was also found to be the most susceptible to small gas concentrations (0.5%), with decreases in average bundle heat transfer coefficients of 50% and 35% at the lowest heat flux (20 kW/m2) and highest heat flux (34 kW/m2), respectively. Row-by-row data showed that noncondensables work to smooth out individual row performance, so that at the highest noncondensable concentrations all rows within a bundle perform similarly. High concentrations of nitrogen also cause the different bundles to perform similarly, within approximately 13% of each other. What are believed to be vapor-shearing effects in the noncondensable gas layer were found to have a noticeable effect with all tube geometries, particularly at the highest heat fluxes.

author list (cited authors)

  • Rewerts, L. E., Huber, J. B., & Pate, M. B.

publication date

  • January 1997