EXPERIMENTAL EVALUATION OF INTERNAL CONDENSATION OF REFRIGERANTS R-12 AND R-134a

Dobson, M.K., J.C. Chato, D.K. Hinde, S.P. Wang* Air Conditioning and Refrigeration Center Department of Mechanical and Industrial Engineering University of lllinois at Urbana-Champaign *Chemical Engineering Research Institute South China University of Technology Guangzhou, PRC Experimental and analytical work has been performed on local heat transfer for intube condensation of pure R-134a and R-12. The data were taken in a 4.57 mm (0.18 in) ill 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, 75-500 kglm2-s (55,000-365,000 Ibm/ft2-hr), saturation temperature, 35 and 60°C (95 and 140 OF); average quality, 10-90%; heat flux, 4-15 kW/m2 (1268-4756 Btu/hr-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.