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Flow boiling heat transfer of zeotropic mixture refrigerants R454B and R449A in a smooth horizontal tube.

Author(s) : XIA Y., YU J., SUULKER D., WANG H. S.

Type of article: IJR article

Summary

The paper reports an experimental investigation of local saturated flow boiling heat transfer of two environmentally-friendly zeotropic mixture refrigerants – R454B and R449A – in a horizontal 8.7 mm ID smooth tube, under high pressure and high heat-flux conditions. The test section is divided into five subsections to obtain quasi-local heat transfer and the refrigerants are heated by hot water in counter-current flow. For R454B, mass flux varied from 201 kg m−2 s−1 to 269 kg m−2 s−1 and the inlet pressure varied from 1.691 MPa to 3.282 MPa. For R449A, mass flux varied from 178 kg m−2 s−1 to 328 kg m−2 s−1 and the inlet pressure varied from 1.449 MPa to 3.244 MPa. The temperature glide and composition shift during flow boiling due to volatility difference between components were investigated. R454B and R449A displayed a temperature glide respectively from 1.12 K to 1.33 K and from 3.04 K to 4.61 K at the inlet of the test section in the present tests. During the process of saturated boiling, for R454B, mass fraction of the less volatile component, R1234yf, in liquid phase was over 7% more than that in vapor phase; For R449A, mass fractions of the less volatile components, R134a and R1234yf, in liquid phase were around 6% and 4% more than those in vapor phase. Thermal resistance and mass transfer resistance were discussed. Before the occurrence of partial dry-out, heat-transfer coefficients of R454B were mainly located between 6.5 kW m−2 K−1 and 10 kW m−2 K−1 while most of data of R449A lay in the range of 3.5 – 8 kW m−2 K−1. The results of heat-transfer coefficient indicate that R454B exhibited greater heat transfer than R449A under close operating conditions. For both refrigerants, the heat transfer performance was locally enhanced in the region of near-zero vapor quality and gradually declines before intermediate vapor quality. After intermediate vapor quality, it tended to rise with vapor quality until a dramatic fall due to partial dry-out.

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Pages: 313-326

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Details

  • Original title: Flow boiling heat transfer of zeotropic mixture refrigerants R454B and R449A in a smooth horizontal tube.
  • Record ID : 30031731
  • Languages: English
  • Subject: Technology
  • Source: International Journal of Refrigeration - Revue Internationale du Froid - vol. 150
  • Publication date: 2023/06
  • DOI: http://dx.doi.org/10.1016/j.ijrefrig.2023.01.019

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