CFD analysis of a supersonic air ejector. Part I: Experimental validation of single-phase and two-phase operation

Hemidi, Amel; Henry, F.; Leclaire, Sébastien; Seynhaeve, Jean-Marie; Bartosiewicz, Yann

doi:10.1016/j.applthermaleng.2008.07.003

Cited by 187 publications

(68 citation statements)

References 14 publications

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“…Although there were no noticeable effects under double-choke operation, an increase of 13% to 98% in the single choke secondary mass flow rate was observed for inlet primary pressures within the range 107 to 446 kPa and inlet humidities between 4.3% and 11.2%. A similar behavior has been reported along with an increase of 5% in P lim for motive inlet humid fractions up to 1% by Hemidi et al [24]. Nonetheless, these results should be taken with caution since the ejector was studied as an independent unit in both cases and using an uncommon fluid pair (air-water) in refrigeration systems.…”

Section: Introductionsupporting

confidence: 58%

“…Concerning two-phase operation, comparisons were made regarding the choked mass flow through a convergent divergent nozzle and the effect of the primary inlet saturation on the entrainment ratio. Figure 5 compares the predicted entrainment ratio values against experimental data from different studies [8,10,24,[34][35][36] with varying dimensions, working gases and operating conditions. As a first step, friction and mixing losses are neglected here such that:…”

Section: Validation Of the Thermodynamic Modelmentioning

confidence: 99%

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Thermodynamic Modelling of Supersonic Gas Ejector with Droplets

Croquer

Poncet

Aidoun

2017

Entropy

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This study presents a thermodynamic model for determining the entrainment ratio and double choke limiting pressure of supersonic ejectors within the context of heat driven refrigeration cycles, with and without droplet injection, at the constant area section of the device. Input data include the inlet operating conditions and key geometry parameters (primary throat, mixing section and diffuser outlet diameter), whereas output information includes the ejector entrainment ratio, maximum double choke compression ratio, ejector efficiency, exergy efficiency and exergy destruction index. In single-phase operation, the ejector entrainment ratio and double choke limiting pressure are determined with a mean accuracy of 18% and 2.5%, respectively. In two-phase operation, the choked mass flow rate across convergent-divergent nozzles is estimated with a deviation of 10%. An analysis on the effect of droplet injection confirms the hypothesis that droplet injection reduces by 8% the pressure and Mach number jumps associated with shock waves occuring at the end of the constant area section. Nonetheless, other factors such as the mixing of the droplets with the main flow are introduced, resulting in an overall reduction by 11% of the ejector efficiency and by 15% of the exergy efficiency.

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Section: Introductionsupporting

confidence: 58%

Section: Validation Of the Thermodynamic Modelmentioning

confidence: 99%

Thermodynamic Modelling of Supersonic Gas Ejector with Droplets

Croquer

Poncet

Aidoun

2017

Entropy

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“…Of particular importance is the dissipative effect of the shock trains as it produces a compression and a shift from supersonic to subsonic conditions. There is considerable research concerning experimental [46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65] and numerical [66][67][68][69][70][71][72][73][74][75][76][77][78][79][80][81] studies of the flow phenomena inside an ejector. Even further detailed knowledge and modeling of these phenomena should allow for better component design.…”

Section: Supersonic Ejectormentioning

confidence: 99%

Ejector refrigeration: A comprehensive review

Besagni

Mereu

Inzoli

2016

Renewable and Sustainable Energy Reviews

414

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a b s t r a c tThe increasing need for thermal comfort has led to a rapid increase in the use of cooling systems and, consequently, electricity demand for air-conditioning systems in buildings. Heat-driven ejector refrigeration systems appear to be a promising alternative to the traditional compressor-based refrigeration technologies for energy consumption reduction. This paper presents a comprehensive literature review on ejector refrigeration systems and working fluids. It deeply analyzes ejector technology and behavior, refrigerant properties and their influence over ejector performance and all of the ejector refrigeration technologies, with a focus on past, present and future trends. The review is structured in four parts. In the first part, ejector technology is described. In the second part, a detailed description of the refrigerant properties and their influence over ejector performance is presented. In the third part, a review focused on the main jet refrigeration cycles is proposed, and the ejector refrigeration systems are reported and categorized. Finally, an overview over all ejector technologies, the relationship among the working fluids and the ejector performance, with a focus on past, present and future trends, is presented.

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“…Most CFD ejector models have been validated by comparing with experimental data [13], [14], [15] with most authors claiming acceptable agreement with experimental results [16]. In some of these studies, simulations have been within 10% of the experimental data [4], but errors around 20% have been reported in [4].…”

Section: Introductionmentioning

confidence: 97%

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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CFD analysis of a supersonic air ejector. Part I: Experimental validation of single-phase and two-phase operation

Cited by 187 publications

References 14 publications

Thermodynamic Modelling of Supersonic Gas Ejector with Droplets

Thermodynamic Modelling of Supersonic Gas Ejector with Droplets

Ejector refrigeration: A comprehensive review

CFD Study of a Variable Flow Geometry Radial Ejector

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