Modelling of Refrigerant Distribution in an Oil-Free Refrigeration System using R134a

Xinwen Chen, Zhaohua Li, Yi Zhao, Hanying Jiang, Kun Liang and Jingxin Chen
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Xinwen Chen: Department of Mechanical Engineering, Yangzhou University, Yangzhou 225012, China
Zhaohua Li: Department of Engineering and Design, University of Sussex, Falmer, Brighton BN1 9QT, UK
Yi Zhao: École Polytechnique, 91128 Palaiseau, France
Hanying Jiang: Department of Engineering and Design, University of Sussex, Falmer, Brighton BN1 9QT, UK
Kun Liang: Department of Mechanical Engineering, Yangzhou University, Yangzhou 225012, China
Jingxin Chen: Department of Mechanical Engineering, Yangzhou University, Yangzhou 225012, China

Energies, 2019, vol. 12, issue 24, 1-15

Abstract: Increasing number of refrigeration units has led to an increase of CO 2 emissions and the destruction of the ozone layer. Using low global warming potential (GWP) refrigerants, improving the efficiency of vapour compression refrigeration (VCR) units, and minimising refrigerant leakages can reduce the global warming effect. Investigating the refrigerant distribution under varied operating conditions can provide a deeper understanding of refrigerant charge optimization. This study proposed a model of refrigerant mass distribution in a prototype oil-free VCR system using a linear compressor with variable strokes and R134a. The absence of the oil lubricant allows the adoption of compact heat exchangers, such as micro-channels, so that the total refrigerant charge can be reduced significantly. The predicted total refrigerant charge has a Mean Absolute Percentage Error (MAPE) of 3.7%. The simulation results indicate that refrigerant distributed in the condenser is most sensitive to operating conditions and total refrigerant charges. The refrigerant accumulated in the condenser is 6.8% higher at a total refrigerant charge of 0.33 kg than that of 0.22 kg. For a total refrigerant charge of 0.33 kg, 72.1% of the total refrigerant can accumulate in the condenser. At a fixed pressure ratio, the refrigerant as a two-phase form in the condenser decreases slightly with the increase of compressor strokes, resulting in a larger mass flow rate, thus cooling capacity. The present model can be adapted for optimization of a refrigeration unit and its components.

Keywords: R134a; oil-free VCR system; refrigerant distribution; condenser; adjustable operating conditions (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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