TY - JOUR
T1 - Numerical simulation of two-phase flow in the second header of MAC condenser
AU - Li, Jun
AU - Hrnjak, Pega
N1 - Funding Information:
We are grateful for financial and technical support from the Air Conditioning and Refrigeration Center at University of Illinois at Urbana-Champaign.
Publisher Copyright:
© 2019 SAE International. All Rights Reserved.
PY - 2019/4/2
Y1 - 2019/4/2
N2 - 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.
AB - 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.
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U2 - 10.4271/2019-01-1065
DO - 10.4271/2019-01-1065
M3 - Conference article
AN - SCOPUS:85064592036
SN - 0148-7191
VL - 2019-April
JO - SAE Technical Papers
JF - SAE Technical Papers
IS - April
T2 - SAE World Congress Experience, WCX 2019
Y2 - 9 April 2019 through 11 April 2019
ER -