Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.
Abstract
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.Air Conditioning and Refrigeration Center Project 0
