Numerical simulation of two-phase flow in the second header of MAC condenser

Research output: Contribution to journalConference article

Abstract

Phase separation circuiting have been proved in the past to effectively improve the performance of mobile air conditioning (MAC) condensers. In the vertical second header of the condenser, liquid separates from vapor mainly due to gravity, leaving vapor-rich flow with higher heat transfer coefficient to go into the upper passes. The condenser effectiveness is improved in this way. However, separation is usually not perfect, expressed through the separation efficiency (ηl and ηv). This paper presents the numerical study of phase separation phenomena in the second header. The Euler-Euler method of Computational Fluid Dynamics (CFD) is used. Simulations are conducted for two-phase refrigerant R-134a for MAC application. Inlet mass flow rate is simulated at values of 16 g-s-1, 20 g-s-1, and 30 g-s-1 for 21 inlet microchannel tubes, which is the same 1st-pass tube number as of a real separation condenser. Corresponding mass fluxes are 166 kg-m-2-s-1, 207 kg-m-2-s-1, and 311 kg-m-2-s-1. Inlet quality is simulated to be 0.16 to 0.21, which was covered by past flow separation efficiency experiments. The CFD simulation is compared to the experimental results with flow visualization and the results of a simple mechanistic model based on empirical correlations. Results agree well with each other, which provides a backup for the physical understanding of two-phase flow inside the second header. Conclusion can be drawn that liquid separation efficiency ηl decreases with increasing ηv following a step-wise decreasing trend. Pressure and streamline profiles inside the header are revealed. Reversed flow can be seen on the cross section of the header.

Original languageEnglish (US)
JournalSAE Technical Papers
Volume2019-April
Issue numberApril
DOIs
StatePublished - Apr 2 2019
EventSAE World Congress Experience, WCX 2019 - Detroit, United States
Duration: Apr 9 2019Apr 11 2019

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Air conditioning
Two phase flow
Computer simulation
Phase separation
Computational fluid dynamics
Vapors
Flow separation
Liquids
Refrigerants
Flow visualization
Microchannels
Heat transfer coefficients
Gravitation
Mass transfer
Flow rate
Experiments

ASJC Scopus subject areas

  • Automotive Engineering
  • Safety, Risk, Reliability and Quality
  • Pollution
  • Industrial and Manufacturing Engineering

Cite this

Numerical simulation of two-phase flow in the second header of MAC condenser. / Li, Jun; Hrnjak, Predrag Stojan.

In: SAE Technical Papers, Vol. 2019-April, No. April, 02.04.2019.

Research output: Contribution to journalConference article

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