Numerical Study on R32 Flow Condensation in Horizontally Oriented Tubes with U-Bends

Zehan Cao, Hao Zhang, Haohan Mei, Gang Yan, Wenxiao Chu and Qiuwang Wang
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Zehan Cao: Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Hao Zhang: Department of Refrigeration & Cryogenic Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Haohan Mei: Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Gang Yan: Department of Refrigeration & Cryogenic Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Wenxiao Chu: Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Qiuwang Wang: Key Laboratory of Thermo-Fluid Science and Engineering, Ministry of Education, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China

Energies, 2022, vol. 15, issue 13, 1-21

Abstract: In this paper, the flow condensation heat transfer characteristics of R32 in a horizontally oriented tube with a horizontal U-bend (HUB tube) and a horizontally oriented tube with a vertical U-bend (VUB tube) were numerically investigated. The volume of fluid (VOF) multiphase model with the mass transfer assumption by Lee is adopted to simulate the flow condensation behavior of R32, which are validated by well-known empirical correlations. The influence of structural parameters, mass flux and vapor quality on the heat transfer coefficient (HTC) and liquid film distribution is investigated. Meanwhile, the local liquid film thickness (LLFT) and local heat transfer coefficient (LHTC) are also depicted. The phase transition at the U-bend section is captured. Results show that the U-bend has remarkable disturbance on the flow pattern and LHTC due to the effect of centrifugal force where the LLFT is changed, inducing strong secondary flow. The LHTC is increased by a maximum of 8.47% and 11.86% in VUB tube and HUB tube, respectively, when compared to the case in a horizontally straight oriented tube at the same operating conditions.

Keywords: R32 flow condensation; VOF model; heat transfer coefficient; film thickness (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: 2022
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