Mixing layer effects on the entrainment ratio in steam ejectors through ideal gas computational simulations

Ejector entrainment ratios are influenced by both pressure-driven effects and the mixing between the primary and secondary streams, but the significance of each factor has not been identified in prior literature. This paper presents a computational simulation investigation of flow in a representative steam ejector to specify the contribution of mixing and pressure-driven effects to the overall ejector entrainment ratio under different operating conditions. The simulation of mixing layer growth was validated by using experimental data available in the literature, while the application of the computational method to the ejector flows was validated using static pressure distribution and entrainment ratio data in the particular experimental ejector arrangement. Simulation results show that under a fixed operating condition for the primary and discharge streams, at lower secondary pressure the ejector entrainment ratio is more strongly influenced by the mixing effects. For the particular ejector and the operating conditions considered herein, about 35% of the ejector entrainment ratio is due to mixing effects when the secondary stream pressure lift ratio is 4.5, while this portion is reduced to about 22% when the secondary stream pressure lift ratio is 1.6.

[1]  Noel T. Clemens,et al.  Large-scale structure and entrainment in the supersonic mixing layer , 1995, Journal of Fluid Mechanics.

[2]  Thanarath Sriveerakul,et al.  CFD simulation on the effect of primary nozzle geometries for a steam ejector in refrigeration cycle , 2013 .

[3]  Xinping Long,et al.  Numerical investigation on the mixing process in a steam ejector with different nozzle structures , 2012 .

[4]  A. Roshko,et al.  The compressible turbulent shear layer: an experimental study , 1988, Journal of Fluid Mechanics.

[5]  Saffa Riffat,et al.  CFD modelling and experimental investigation of an ejector refrigeration system using methanol as the working fluid , 2001 .

[6]  H. M. Lee,et al.  Numerical prediction of jet behavior of thermal vapor compressor , 2011 .

[7]  Changyun Wen,et al.  Numerical investigation of geometry parameters for design of high performance ejectors , 2009 .

[8]  Peng Cheng,et al.  Experimental investigation and theoretical analysis of an ejector refrigeration system , 2013 .

[9]  T. Sriveerakul,et al.  Performance prediction of steam ejector using computational fluid dynamics: Part 1. Validation of the CFD results , 2007 .

[10]  S. Goebel,et al.  EXPERIMENTAL STUDY OF COMPRESSIBLE TURBULENT MIXING LAYERS , 1991 .

[11]  Goro Masuya,et al.  Spreading of two-stream supersonic turbulent mixing layers , 1986 .

[12]  Satha Aphornratana,et al.  An experimental investigation of a steam ejector refrigerator: the analysis of the pressure profile along the ejector , 2004 .

[13]  Bogdan Diaconu,et al.  Numerical assessment of steam ejector efficiencies using CFD , 2009 .

[14]  A. Roshko,et al.  On density effects and large structure in turbulent mixing layers , 1974, Journal of Fluid Mechanics.

[15]  Saffa Riffat,et al.  Computational fluid dynamics applied to ejector heat pumps , 1996 .

[16]  J. Dussauge,et al.  Compressibility effects on the structure of supersonic mixing layers: experimental results , 1994, Journal of Fluid Mechanics.

[17]  Paul E. Dimotakis,et al.  Turbulent shear-layer mixing: growth-rate compressibility scaling , 2000, Journal of Fluid Mechanics.

[18]  Hyomin Jeong,et al.  CFD investigation on the flow structure inside thermo vapor compressor. , 2010 .

[19]  Thanarath Sriveerakul,et al.  Experimental studies of a steam jet refrigeration cycle: Effect of the primary nozzle geometries to system performance , 2011 .

[20]  Bogdan Diaconu,et al.  Influence of geometrical factors on steam ejector performance – A numerical assessment , 2009 .

[21]  Randheer L. Yadav,et al.  Design aspects of ejectors: Effects of suction chamber geometry , 2008 .

[22]  T. Sriveerakul,et al.  Performance prediction of steam ejector using computational fluid dynamics: Part 2. Flow structure of a steam ejector influenced by operating pressures and geometries , 2007 .

[23]  Xiaodong Wang,et al.  Numerical study on the performances of steam-jet vacuum pump at different operating conditions , 2010 .

[24]  D. W. Bogdanoff,et al.  Compressibility Effects in Turbulent Shear Layers , 1983 .

[25]  Ian W. Eames,et al.  Results of an experimental study of an advanced jet-pump refrigerator operating with R245fa , 2007 .

[26]  P. Dimotakis.  Two-dimensional shear-layer entrainment , 1986 .

[27]  M. Slessor.  Aspects of turbulent-shear-layer dynamics and mixing , 1998 .

[28]  Alexander J. Smits,et al.  Turbulent Shear Layers in Supersonic Flow , 1996 .

[29]  Mo Samimy,et al.  Effects of compressibility on the characteristics of free shear layers , 1990 .

[30]  P. Dimotakis.  Entrainment into a fully developed, two-dimensional shear layer , 1984 .

[31]  Mohamed Ouzzane,et al.  The effect of operating conditions on the performance of a supersonic ejector for refrigeration , 2004 .