Condensation of a Zeotropic Refrigerant R-321R-125/R-134a (23o/al25o/al52%) in a Horizontal Tube

Abstract

This experimental study examined the local heat transfer coefficients and frictional pressure gradients of a ternary zeotropic refrigerant mixture, R-32/R-125/R-134a (23%/25%/52%) condensing in a smooth, horizontal tube. The test section consisted of a 3 ft long, copper tube with a diameter of 0.277 in (7.04 mm) surrounded by a counter-flow, water-cooled annulus. Test conditions varied the average quality from 10% to 90% and the mass flux from 55 to 474 klb/ft2_hr (75 to 650 kg/m2-s) to insure that data points were taken all across the wavy and annular flow regimes. The temperature difference was held approximately constant at 5.4 OF (3.0 ??C). At mass fluxes higher than 364 klb/ft2_hr (500 kg/m2-s), the Dobson correlation consistently overpredicted the heat transfer coefficients requiring a least squares-determined factor of 0.836 to correct. As the flow regime approached wavy flow, the Dobson correlation increasingly overpredicted the heat transfer coefficient due to the dominance of zeotropic degradation. Frictional pressure gradient data showed similar trends to the Souza pressure drop correlation but were significantly lower.Air Conditioning and Refrigeration Center Project 3