Condensation heat transfer of R1234ze(E) and its A1 mixtures in small diameter channels. (May 2022)

• Record Type: Journal Article
• Authors: Azzolin, Marco; Berto, Arianna; Bortolin, Stefano; Del Col, Davide
• Is Part Of: International journal of refrigeration. Volume 137(2022)
• Page Start: 153
• Page End: 165
• Publication Date: 2022-05
• Subjects: Condensation -- Heat transfer coefficient -- Flow visualizations -- Pressure drop -- R515B -- R450A; Condensation -- Coefficient de transfert de chaleur -- Visualisation de l'écoulement -- Chute de pression -- R515B -- R450A; Refrigeration and refrigerating machinery -- Periodicals; 621.56
• DOI: 10.1016/j.ijrefrig.2022.02.002
• Languages: English
• ISSNs: 0140-7007

Abstract

Highlights: Condensation of R1234ze(E) and two A1 blends (R515B, R450A) is investigated. Experiments are performed inside a 3.38 mm and a 0.96 mm diameter channel. Heat transfer coefficients, two-phase pressure drop and flow regimes are investigated. Predictive models for condensation heat transfer and pressure drop are assessed. A comparative analysis based on penalty factor is performed among the tested fluids and R134a. Abstract: 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 °C). Heat transfer coefficients are measured at 40 °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.