A CFD-based numerical analysis of a two-phase R744 ejector using heterogeneous mixture model is presented in this work. The flow patterns inside the ejector, such as the mass transfer rate, change of pressure and velocity alongside the ejector are analyzed. Based on the experimental work, the numerical model is validated. The effect of the ejector’s nozzle geometry on the ejector performance is discussed, and an optimization of the nozzle geometry is performed. Based on the experimental data, the numerical model predicts the motive mass flow rate and the suction pressure within an error margin of 6.5%. Shock wave phenomenon can be observed around the nozzle exit. The motive mass flow rate of the ejector decreases and the motive velocity increases with the increasing divergent length. The optimization of the nozzle geometry can increase the ejector efficiency by 10.5%.
WANG Yufeng,WANG Dandong,HU Jichao,CHEN Liang,CHEN Jiangping
. A Numerical Model of the Two-Phase CO2 Ejectors[J]. Journal of Shanghai Jiaotong University, 2019
, 53(7)
: 860
-865
.
DOI: 10.16183/j.cnki.jsjtu.2019.07.013
［1］TISCHENDORF C. Investigation of an ejector in a R744 refrigeration systems with intermediate pressure evaporator ［D］. Braunschweig, Germany: Braunschweig University of Technology, 2014.
［2］LIU F, GROLL E A. Study of ejector efficiencies in refrigeration cycles ［J］. Applied Thermal Engineering, 2013, 52(2): 360-370.
［3］LUCAS C, KOEHLER J. Experimental investigation of the COP improvement of a refrigeration cycle by use of an ejector［J］. International Journal of Refrigeration, 2012, 35(6): 1595-1603.
［4］YAZDANI M, ALAHYARI A A, RADCLIFF T D. Numerical modeling of two-phase supersonic ejectors for work-recovery applications［J］. International Journal of Heat and Mass Transfer, 2012, 55(21/22): 5744-5753.
［5］PALACZ M, SMOLKA J, KUS W, et al. CFD-based shape optimisation of a CO2 two-phase ejector mixing section［J］. Applied Thermal Engineering, 2016, 95: 62-69.
［6］ANSYS Inc. ANSYS Fluent theory guide ［CP］. Canonsburg, PA: ANSYS Inc, 2011.
［7］SINGHAL A K, ATHAVALE M M, LI H, et al. Mathematical basis and validation of the full cavita-tion model［J］. Journal of Fluids Engineering, 2002, 124(3): 617-624.
［8］ELBEL S, HRNJAK P. Experimental validation of a prototype ejector designed to reduce throttling losses encountered in transcritical R744 system operation［J］. International Journal of Refrigeration, 2008, 31(3): 411-422.
［9］MATSUO K, MIYAZATO Y, KIM H D. Shock train and pseudo-shock phenomena in internal gas flows［J］. Progress in Aerospace Sciences, 1999, 35(1): 33-100.
［10］GNANI F, ZARE-BEHTASH H, KONTIS K. Pseudo-shock waves and their interactions in high-speed intakes［J］. Progress in Aerospace Sciences, 2016, 82: 36-56.
［11］LIEELE A B, GARIMELLA S. A critical review linking ejector flow phenomena with component- and system-level performance［J］. International Journal of Refrigeration, 2016, 70: 243-268.
［12］KAWAMOTO Y, OGATA G, SHAN Z. Ejector energy-saving technology for mobile air conditioning systems［J］. SAE Int J Passeng Cars-Mech Syst, 2017, 10(1): 102-110.
