Experimental investigation of refrigerant condensation in circular and square micro- and mini- channels. (September 2021)

• Record Type: Journal Article
• Authors: Keniar, Khoudor; Garimella, Srinivas
• Is Part Of: International journal of heat and mass transfer. Volume 176(2021)
• Publication Date: 2021-09
• Subjects: Condensation -- Microchannels -- Synthetic refrigerants -- Experiments; Heat -- Transmission -- Periodicals; Mass transfer -- Periodicals; Chaleur -- Transmission -- Périodiques; Transfert de masse -- Périodiques; Electronic journals; 621.4022
• DOI: 10.1016/j.ijheatmasstransfer.2021.121383
• Languages: English
• ISSNs: 0017-9310

Abstract

Highlights: Construction of a low heat duty, low mass flux facility to measure condensation heat transfer. Experiments conducted at different mass fluxes, channel geometry and working fluids. Heat transfer coefficient is higher for a square geometry compared to circular. R245fa has higher heat transfer coefficient than R134a and R1234ze(E) at the same conditions. R1234ze(E) is drop-in replacement for R134a in condensation applications with heat transfer penalty < 10%. Abstract: Microchannel condensers have the potential to improve system level efficiency by increasing the heat transfer coefficient because of the small hydraulic diameters. In addition, they offer a high surface area-to-volume ratio, reducing the overall system size and fluid inventory. Understanding condensation in microchannels is essential for efficient component design, especially with the need for new low Global Warming Potential (GWP) working fluids. Condensation of refrigerants R134a, R245fa and R1234ze(E) in circular ( D h = 1.55 mm) and square ( D h = 0.98 mm) microchannels over a range of mass fluxes (50 < G < 200 kg m −2 s −1 ), saturation temperatures (30 < T sat < 50°C), and wall subcooling (1.7 < ΔT < 5K) is investigated in this study. It is found that at high mass fluxes ( G ≥ 150 kg m −2 s −1 ), R245fa has a higher heat transfer coefficient and pressure gradient than both R1234ze(E) and R134a, which have comparable heat transfer coefficients at similar conditions. In the circular channel, for a mass flux range of 50 < G < 150 kg m −2 s −1 and T sat = 30°C, the heat transfer coefficients for R245fa, R134a, and R1234ze(E) varied between 2.3 and 6.7 kW m −2 K −1, 2.5 and 4.7 kW m −2 K −1, and 2.2 and 5.4 kW m −2 K −1, respectively.