An Integrated Lumped Parameter-CFD approach for off-design ejector performance evaluation

Besagni, Giorgio; Mereu, Riccardo; Chiesa, Paolo; Inzoli, Fabio

doi:10.1016/j.enconman.2015.08.029

Cited by 100 publications

(49 citation statements)

References 70 publications

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“…To obtain more accurate prediction performance, the ejector component efficiencies should be determined carefully since they dramatically influence the validity of an ejector model [26] and the values of the efficiencies depend on the ejector geometry, working fluid and operation conditions [8,9]. In this paper, five efficiencies, η p , η s , η m , φ m and η d are introduced in critical point model.…”

Section: Experimental Verificationmentioning

confidence: 99%

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Performance Predictions of Dry and Wet Vapors Ejectors Over Entire Operational Range

Chang

et al. 2017

Energies

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Abstract:If a traditional ideal-gas ejector model is used to evaluate the performance of a wet vapor ejector, large deviations from the experimental results will be unavoidable. Moreover, the model usually fails to assess the ejector performance at subcritical mode. In this paper, we proposed a novel model to evaluate the performance of both dry and wet vapors ejectors over the entire operational range at critical or subcritical modes. The model was obtained by integrating the linear characteristic equations of ejector with critical and breakdown points models, which were developed based on the assumptions of constant-pressure mixing and constant-pressure disturbing. In the models, the equations of the two-phase speed of sound and the property of real gas were introduced and ejector component efficiencies were optimized to improve the accuracy of evaluation. It was validated that the proposed model for the entire operational range can achieve a better performance than those existing for R134a, R141b and R245fa. The critical and breakdown points models were further used to investigate the effect of operational parameters on the performance of an ejector refrigeration system (ERS). The theoretical results indicated that decreasing the saturated generating temperature when the actual condensing temperature decreases, and/or increasing the saturated evaporating temperature can improve the performance of ERS significantly. Moreover, superheating the primary flow before it enters the ejector can further improve the performance of an ERS using R134a as a working fluid.

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Section: Experimental Verificationmentioning

confidence: 99%

“…Compared with their experiment data of R141b ejectors, the maximum evaluation error is 22.99%. Besagni et al [9] proposed a model for sonic and sub-sonic ejectors based on the ideal-gas assumption. In the model, the correlation equations of ejector component efficiencies were determined by CFD method.…”

Section: Introductionmentioning

confidence: 99%

Performance Predictions of Dry and Wet Vapors Ejectors Over Entire Operational Range

Chang

et al. 2017

Energies

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“…Moreover, the spatial discretization was developed considering the "Green-Gauss Cell Based" approach for the gradient and the "Third-Order MUSCL" for the flow and the turbulent kinetic The calculation mesh was obtained with the devoted tool of Fluent considering the following aspects: about 530,000 cells, tetrahedral type, unstructured approach, curvature and proximity (5 cells minimum number) method, 10 inflation levels on the solid boundaries (preliminary calculations showed no significant solution variation increasing the inflation levels, in agreement with the wall treatment performance shown in [27] for the fine mesh). A preliminary mesh was obtained with the Fluent mesher tool.…”

mentioning

confidence: 62%

“…The obtained mesh quality was about 0.5. This mesh was selected after some preliminary calculations to obtain a good solution independence from the grid [27,28]. Theses preliminary simulations showed about 13% change in the recirculation ratio (in comparison with the chosen approach) for a mesh composed of 252,000 cells and no significant variations for values higher than 500,000 cells.…”

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confidence: 99%

Validated ejector model for hybrid system applications

Ferrari

Pascenti

Massardo

2018

Energy

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The aim of this work is the presentation of a new model for ejector performance calculation using a commercial tool. Due to the critical issues in recirculation performance, special attention is devoted to applications in hybrid systems based on high temperature fuel cells. The theoretical activity is supported by an experimental rig able to operate tests on ejectors at different operative conditions, with a layout similar to the fuel cell anodic recirculation. The model validation, operated considering experimental data obtained with this rig, is essential to evaluate the tool performance for design and off-design calculations. This aspect is particularly critical due to important limitations in the recirculation ratio (especially for the anodic side), to avoid unacceptable operative conditions in the fuel cells.The results presented in this work were obtained with this validated model for an ejector applied on the anodic side of a Solid Oxide Fuel Cell (SOFC). A parametric analysis was carried out to show the effects of several parameters on the recirculation performance. The fully independent analysis of the influence of different properties (carried out with a specifically validated model) is an important innovative result for the application of such ejectors on high temperature fuel cells.

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“…The discussion about turbulence models has been continued. Zhu et al rendered that the RNG k-epsilon turbulence viscosity model agreed best with the shock wave structures [27], while Besagni compared seven models and showed that the k-ω SST presented a better performance [30]. Considering the calculating time and convergence rate, the standard model was applied to simulate the high speed flow in this work.…”

Section: Cfd Methodsmentioning

confidence: 97%

Reverse Circulation Drilling Method Based on a Supersonic Nozzle for Dust Control

Yin

et al. 2016

Applied Sciences

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Abstract:To reduce dust generated from drilling processes, a reverse circulation drilling method based on a supersonic nozzle is proposed. The suction performance is evaluated by the entrainment ratio. A series of preliminary laboratory experiments based on orthogonal experimental design were conducted to test the suction performance and reveal the main factors. Computational fluid dynamics (CFD) were conducted to thoroughly understand the interaction mechanism of the flows. The Schlieren technique was further carried out to reveal the flow characteristic of the nozzle. The results show that the supersonic nozzle can significantly improve the reverse circulation effect. A high entrainment ratio up to 0.76 was achieved, which implied strong suction performance. The CFD results agreed well with experimental data with a maximum difference of 17%. This work presents the great potential for supersonic nozzles and reverse circulation in dust control, which is significant to protect the envrionment and people's health.

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An Integrated Lumped Parameter-CFD approach for off-design ejector performance evaluation

Cited by 100 publications

References 70 publications

Performance Predictions of Dry and Wet Vapors Ejectors Over Entire Operational Range

Performance Predictions of Dry and Wet Vapors Ejectors Over Entire Operational Range

Validated ejector model for hybrid system applications

Reverse Circulation Drilling Method Based on a Supersonic Nozzle for Dust Control

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