NO-94-05-3 -- Experimental Evaluation of Interval Condensation of Refrigerants R-12 and R-134a PDF

Experimental and analytical work has been performed on local heat transfer for in-tube condensation of pure R12 and R134a. The data were taken in a 4.57-mm (0.18-in.) ID smooth copper tube of 2.90 m (9.5 ft) length. The test section was cooled by two counterflow water circuits, each covering half of the test section length. Sight glasses of the same diameter as the test section were located at the inlet and outlet of the test section for visual flow regime observations. Data were taken with test conditions in the following ranges - mass flux, 75 to 500 kg/m²×s (55,000 to 365,000lbm/ft²×h), saturation temperature, 35 deg C and 60 deg C (95 deg F and 140 deg F), average quality, 10% to 90%, and heat flux, 4 to 15 kW/m² (1,268 to 4,756 Btu/h×ft²). The observed flow regimes were wavy at low mass flux and quality, progressing sequentially through the wavy-annular, annular, and mist-annular flow regimes as the mass flux and quality were increased. The data for pure refrigerants in the wavy flow regime were successfully correlated with a modified Nusselt-type approach and exhibited no mass flux dependence. The annular flow data were successfully correlated based on an analogy between heat and momentum transfer.

KEYWORDS: experiment, calculating, condensation, refrigerants, R12, R134a, heat flow, tubes, copper, testing, saturation temperature, fluid flow, condensers, heat transfer coefficient.