Journal
INTERNATIONAL JOURNAL OF REFRIGERATION
Volume 137, Issue -, Pages 153-165Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.ijrefrig.2022.02.002
Keywords
Condensation; Heat transfer coefficient; Flow visualizations; Pressure drop; R515B; R450A
Categories
Funding
- ESA (European Space Agency) through the MAP Condensation program ENCOM [AO-2004-096]
- MiSE (Italian Ministry of Economic Development) - ENEA (Italian National Agency for New Technologies, Energy and Sustainable Eco-nomic Development) program Ricerca di Sistema Elettrico - Piano Triennale di Realizzazione
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R1234ze(E) has emerged as a low Global Warming Potential substitute for R134a. However, it is mildly flammable. This study compares the heat transfer coefficients and two-phase pressure drops of R450A and R515B binary mixtures with R1234ze(E) as potential non-flammable alternatives.
R1234ze(E) has emerged in the recent years as low Global Warming Potential substitute for R134a in refrigeration and air-conditioning systems. As a drawback, R1234ze(E) is classified as a mildly flammable fluid (A2L class) and, in the search for non-flammable alternatives to R134a, hydrofluorocarbon/hydrofluoroolefin binary mixtures can be considered. In the present work, condensation tests are performed with R1234ze(E) and non-flammable binary mixtures R450A (R1234ze(E)/R134a at 58.0/42.0% by mass) and R515B (R1234ze(E)/R227ea at 91.1/8.9% by mass) inside two channels with inner diameter equal to 3.38 mm and 0.96 mm. R515B is an azeotropic mixture whereas R450A is a near-azeotropic blend (temperature glide 0.6 K at 40 degrees C). Heat transfer coefficients are measured at 40 degrees C saturation temperature and mass flux from 40 kg m(-2) s(-1) to 600 kg m(-2) s(-1). Flow pattern visualizations are recorded by a high-speed camera in the 3.38 mm inner diameter tube. Two-phase pressure gradients are measured in the 0.96 mm test section at mass flux equal to 200 and 400 kg m(-2) s(-1). The prediction accuracy of condensation heat transfer and two-phase pressure drop models is assessed against the experimental results. A comparative study between the tested fluids and R134a, accounting for both the heat transfer coefficients and the two-phase pressure drops, is performed.
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