Probabilistic flow pattern-based heat transfer correlation for condensing intermittent flow of refrigerants in smooth horizontal tubes

This paper presents a signal analysis method used for condensing refrigerants that results in a modification in the prediction method for heat transfer based on probabilistic time-fractional results. Development of an objective visual method for discrimination of flow patterns and determining probabilistic time-fractions in intermittent flow is presented. The frequency domain was identified as the main candidate for discrimination of sub-regimes present in intermittent flow. Experimental work was conducted using refrigerants R-22 and R-134a, at an average saturation temperature of 40°C, with mass fluxes ranging from 200to700kg/m2s, and with test section inlet vapour qualities ranging from 0.65 down to 0.10. These test conditions mostly represent intermittent flow. The new time fraction-corrected flow regime-based heat transfer correlation is heavily based on the Thome et al. (2003) [36] correlation. The modified correlation predicted the experimental data with a mean absolute deviation of 10%.