Heat Transfer of Near Pseudocritical Nitrogen in Helically Coiled Tube for Cryogenic Energy Storage

Yi Wang, Tiejun Lu, Xianglei Liu, Adriano Sciacovelli and Yongliang Li
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Yi Wang: School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK
Tiejun Lu: School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK
Xianglei Liu: School of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Adriano Sciacovelli: School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK
Yongliang Li: School of Chemical Engineering, University of Birmingham, Birmingham B15 2TT, UK

Energies, 2022, vol. 15, issue 8, 1-20

Abstract: This paper investigates the cryogenic heat transfer phenomena of nitrogen flowing in helically coiled tubes under the combined effects of pseudocritical conditions, buoyancy, and coil curvature. The ultimate goal was to design optimum heat exchangers for liquid air energy storage. Local heat transfer coefficients were evaluated peripherally across tube cross sections. The pressure, mass flux, and heat flux effects on the heat transfer were examined. The dual effect of buoyancy and coil curvature on heat transfer coefficients was interpreted via a dimensionless number Ψ, which denotes a ratio between the two effects. Results reveal that the heat transfer coefficients increase with increasing mass flux but decreasing pressure and heat flux. The buoyancy effect dominates the heat transfer at fluid temperatures below the pseudocritical temperature (e.g., −146.3 °C at 35 bar), while the coil curvature-induced centrifugal effect dominates at higher temperatures. The heat transfer coefficients for the helical coil were approximately 13% lower compared with those in straight tube at fluid temperatures below the pseudocritical temperature, but their difference shrinks (<±6%) at higher temperatures. The reason is that the benefits of coil curvature and improved turbulent mixing on heat transfer are counteracted by the thermophysical property variation and buoyancy effect.

Keywords: supercritical nitrogen; pseudocritical; helical coil; convective heat transfer; centrifugal force; buoyancy (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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