Condensation from superheated vapor flow of R744 and R410A at subcritical pressures in a horizontal smooth tube

Chieko Kondou, Pega Hrnjak

Research output: Contribution to journalArticlepeer-review

Abstract

This paper presents experimentally determined heat transfer coefficients for condensation from a superheated vapor of CO 2 and R410A. The superheated vapor was flowed through a smooth horizontal tube with 6.1 mm ID under almost uniform temperature cooling at reduced pressures from 0.55 to 0.95, heat fluxes from 3 to 20 kW m -2, and superheats from 0 to 40 K. When the tube wall temperature reaches the saturation point, the measured results show that the heat transfer coefficient gradually starts deviating from the values predicted by a correlation valid for single-phase gas cooling. This point identifies the start of condensation from the superheated vapor. The condensation starts earlier at higher heat fluxes because the tube wall temperature reaches the saturation point earlier. The heat transfer coefficient reaches a value predicted by correlations for condensation at a thermodynamic vapor quality of 1. The measured heat transfer coefficient of CO 2 is roughly 20-70% higher than that of R410A at the same reduced pressures. This is mainly because the larger latent heat and liquid thermal conductivity of CO 2, compared to that of R410A, increase the heat transfer coefficient.

Original languageEnglish (US)
Pages (from-to)2779-2791
Number of pages13
JournalInternational Journal of Heat and Mass Transfer
Volume55
Issue number11-12
DOIs
StatePublished - May 2012

Keywords

  • Carbon dioxide
  • Condensation
  • Heat transfer
  • Horizontal tube
  • R410A
  • Refrigeration

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanical Engineering
  • Fluid Flow and Transfer Processes

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