Proceedings of the Second International Energy 2030 Conference,
November 4-5, 2008, Abu Dhabi, UAE

Performance Characterization of Two Selected Refrigerants in a Flat-Plate Micro-Tube Condenser

E. Al-Hajri
University of Maryland, USA

S. Dessiatoun
University of Maryland, USA

A. Shooshtari
University of Maryland, USA

M. Ohadi
The Petroleum Institute, UAE

Abstract
This work presents a detailed characterization study of two-phase condensing flows of two refrigerants, R134a and R-245fa, in a single water-cooled micro-channel with a 0.4 mm x 2.8 mm cross-section (0.7 mm hydraulic diameter and 7:1 aspect ratio) and length of 190 mm. A single micro-channel was chosen for the study to eliminate flow mal-distribution issues commonly encountered in micro-channel banks. The experiments included a parametric study of the effects on average heat transfer coefficient and overall pressure drop of variations across the micro-channel condenser with mass fluxes between 50 and 500 kg/m²s, saturation temperatures between 30ºC and 70ºC, and inlet super heats between 0ºC and 20ºC. The inlet state was kept either at 100% quality or superheat and the outlet condition at 0% quality; these calculations were based on water-side heat rejection. Careful design and instrumentation of the test setup resulted in energy balance uncertainty within +/-11% and uncertainty of average heat transfer coefficient within +/-12%. It was determined that inlet superheat has little effect on heat transfer coefficient and overall pressure drop, but that the corresponding effects of saturation temperature and mass flux are significant.