SUMMARY

The proposed study addresses the need for zero ozone-depletion-potential (ODP) refrigerants or ‎refrigerant blends with properties similar to CFCs (Chlorofluorocarbon) and HCFCs ‎‎(Hydrochlorofluorocarbon). The azeotropic refrigerant blend R410A (equal parts of R32 and ‎R125 by mass) has zero ODP and has properties similar to R22, and is therefore of interest for ‎vapor compression cycles in high-temperature-lift space-conditioning and water heating ‎applications. ‎ This investigation focuses on experimentally determining local heat transfer coefficients and ‎pressure drops for R410A during condensation at 0.8, 0.9xPcritical and gas cooling at 1.0, 1.1, ‎‎1.2xPcritical. All experiments will be conducted for flow through three different round tubes (D = ‎‎3.048, 1.524, 0.762 mm) over a mass flux range of 200 < G < 800 kg/m2-s. An innovative ‎thermal amplification technique will be used to accurately determine the heat duty while ‎ensuring low uncertainties in the refrigerant heat transfer coefficients. ‎ The experimental results will be compared with the limited literature for similar conditions. Flow ‎regime maps from the literature will be used as the basis for developing models of the measured ‎pressure drop and heat transfer during condensation. Similarly, in the supercritical states, the ‎models will account for the sharp variations in the thermophysical properties near the critical ‎point.‎ The models and physical understanding resulting from this investigation will provide the ‎information necessary for designing and optimizing new components that utilize R410A for air-‎conditioning and heat pumping applications.‎