CFD simulation on the effect of primary nozzle geometries for a steam ejector in refrigeration cycle

Ruangtrakoon, Natthawut; Thongtip, Tongchana; Aphornratana, Satha; Sriveerakul, Thanarath

doi:10.1016/j.ijthermalsci.2012.07.009

Cited by 175 publications

(79 citation statements)

References 15 publications

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“…The density-based implicit solver, which has been verified as a suitable solver for supersonic flow fields [19], [20], has been employed in this study. A second order upwind scheme was selected to discretise the equations to achieve higher accuracy at cell faces [21].…”

Section: Methodsmentioning

confidence: 99%

“…A second order upwind scheme was selected to discretise the equations to achieve higher accuracy at cell faces [21]. To define convergence of the solution, all residuals for calculations must fall to a specific level [20], which, for the present work was specified as less than 10 −5 . Essentially the same CFD modelling has been used for the three different geometries -different separations of the plates that form the ejector duct in the present work: the choice of solver, the turbulence model, the working fluid, the boundary conditions and convergence criteria were the same for both studies.…”

Section: Methodsmentioning

confidence: 99%

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CFD Study of a Variable Flow Geometry Radial Ejector

Rahimi¹,

Buttsworth²,

Malpress³

2017

Proceedings of the 4th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'17)

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-To achieve higher performance from ejectors at some working conditions, implementations of variable geometry might be possible. While axisymmetric ejectors with axial flow paths have limitations that make practical implementation of variable geometry difficult, radial ejector configurations have a flow path that is conducive to changes in nozzle and ejector throat area during operation. The geometric adjustment of the radial ejector could be made by simply changing the separation of the radial ejector duct walls and/or the separation of the nozzle walls in order to optimize performance over a range of different conditions. The effects of such changes on the performance of a radial ejector have been investigated using a Computational Fluid Dynamic (CFD) analysis with ANSYS FLUENT software. Axisymmetric CFD models were generated to assess performance for a primary nozzle throat area of 8.792 mm 2 and for ejector throat separations of 2.2 mm, 2.4 mm and 3.0 mm, corresponding to ejector throat areas of 497, 543 and 678 mm 2 , respectively. The CFD analysis reveals that changes ejector performance can be achieved by changing the ejector duct's separation. An increase of 34% in entrainment ratio can be achieved by increasing the ejector throat separation from 2.2 mm to 3.0 mm at fixed primary and secondary pressures of 160 kPa and 1.8 kPa, respectively. If an increase in the ejector malfunction pressure is needed, it could be achieved by decreasing the ejector duct separation. An overall malfunction pressure increase of 18% can be achieved by decreasing the ejector throat separation from 3.0 mm to 2.2 mm at primary and secondary pressures of 250 and 1.8 kPa, respectively.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

CFD Study of a Variable Flow Geometry Radial Ejector

Rahimi¹,

Buttsworth²,

Malpress³

2017

Proceedings of the 4th International Conference of Fluid Flow, Heat and Mass Transfer (FFHMT'17)

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“…The complex flow in ejector has led to increasing reliance on CFD as a design tool (Fan et al 2011) and many researchers have agreed with CFD for predicting results closer to the experimental values (Rusly et al 2005;Ruangtrakoon et al 2013;Sriveerakul et al 2007). …”

Section: Numerical Simulationmentioning

confidence: 99%

“…The geometry and the operating conditions of the ejector influence the entrainment ratio (Varga et al 2009). The effect of operating conditions on the performance of the ejector is relatively well established when compared with the geometrical effects (Ruangtrakoon et al 2013;Varga et al 2009;Sankarlal & Mani, 2005). The most influencing geometrical parameters over the performance of ejector are the area ratio (ratio of the area between constant area mixing chamber to primary nozzle throat), the primary nozzle exit position, the convergent angle of the constant pressure mixing section, and the length of constant area mixing section (Eames et al 2007;Jia & Wenjian, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Analytical and Numerical Studies of a Steam Ejector on the Effect of Nozzle Exit Position and Suction Chamber Angle to Fluid Flow and System Performance

Ramesh¹,

Sekhar²

2017

JAFM

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Nozzle exit position [NXP] plays a vital role in the performance of the ejector, but its values are specified in a range for the required operating condition. In this study instead of the range of values, a specific value, named as entrainment diameter is developed and its effect on the performance of the ejector is studied for several combinations of suction chamber angle using numerical method. The effect of the condenser and boiler pressures on the performance of the ejector are also studied to ensure the off-design operating conditions. The entrainment diameter of an ejector is derived analytically by solving one dimensional compressible fluid flow equations using MATLAB. To study the effect of entrainment diameter on the performance of the ejector, CFD technique is employed. Analytical and numerical results are validated with experimental data available in the previous studies. For 7 kW refrigeration capacity, it is inferred that the suction chamber angle of 18° and the corresponding entrainment diameter 90.8 mm with the NXP of 23.62 mm yield the maximum entrainment ratio. The study predicts that the performance of the ejector is highly influenced by the pressure increment at the exit of the nozzle, while the suction chamber angle is between 12° to 21°.

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Design and numerical investigation of ejector for gas pressurization

Wang

Li³

et al. 2021

Asia-Pacific J Chem Eng

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Compared with the compressor, the ejector is a novel cost‐effective device to pressurize gas. Taking the regeneration natural gas pressurization process in the molecular sieve dehydration system as an example, it is first proposed to replace the compressor with an ejector to accomplish the pressurized recovery of low‐pressure regeneration natural gas. The numerical simulation method has been validated, and its results agree well with published experimental results. The simulation results indicate that the ejector designed with one‐dimensional theory can achieve the low‐pressure gas pressurization. Besides, the influence of operating parameters and structural parameters on the ejector performance is also investigated. As the discharged pressure increases, the entrainment ratio gradually decreases, but the pressure ratio rises linearly. With the increase of the induced flow pressure, the ejector pressurization range reduces. Under different discharged pressure, the entrainment ratio presents three different trends when the primary flow pressure enhances. Also, a larger nozzle exit diameter will cause the shock wave phenomenon, which is not conducive to the ejector performance, so there is an optimal nozzle exit diameter for the ejector. The length of the constant‐area mixing chamber has seldom effect on the pressure ratio. The optimal value of the NXP for entrainment ratio is equal to (0.5–1.0)d2. In conclusion, the research provides a new gas pressurization approach and a much better understanding of the gas flow and mixing process within the ejector.

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CFD simulation on the effect of primary nozzle geometries for a steam ejector in refrigeration cycle

Cited by 175 publications

References 15 publications

CFD Study of a Variable Flow Geometry Radial Ejector

CFD Study of a Variable Flow Geometry Radial Ejector

Analytical and Numerical Studies of a Steam Ejector on the Effect of Nozzle Exit Position and Suction Chamber Angle to Fluid Flow and System Performance

Design and numerical investigation of ejector for gas pressurization

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