CFD analysis of variable wall thickness scroll expander integrated into small scale ORC systems

Emhardt, Simon; Song, Panpan; Tian, Gui Yun; Chew, John W.; Wei, Mingshan

doi:10.1016/j.egypro.2019.01.241

Cited by 19 publications

(13 citation statements)

References 2 publications

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“…However, the 2D CFD approach in combination with the assumption of no clearances (and hence no leakage) restricted the accuracy. Emhardt et al (2019) [31] carried out CFD simulations for variable wall thickness scroll expanders. Over-and under-expansion phenomena occurred at two pressure ratios of 2.5 and 5.5 which was in accordance with the thermodynamic theory of scroll expanders.…”

Section: Introductionmentioning

confidence: 99%

CFD modelling of small scale ORC scroll expanders using variable wall thicknesses

Emhardt

Tian

Song

et al. 2020

Energy

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Section: Introductionmentioning

confidence: 99%

CFD modelling of small scale ORC scroll expanders using variable wall thicknesses

Emhardt

Tian

Song

et al. 2020

Energy

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“…The turbulence is considered with a Shear Stress Transport (SST) turbulent model in CFX, whereas with a k-ε model in PumpLinx, since neither the SST nor the k-ω are available for this software. However, it must be pointed out that the k-ε model is the state-of-the-art turbulence model in CFD simulations carried out on scroll geometries, as it is clearly highlighted in Table 6 of [5] and confirmed by the most recent CFD studies on scrolls [35,36]. So, the difference in turbulent model is www.videleaf.com considered useful to evaluate the accuracy of the k-ω model in comparison with the state-of-the-art k-ε approach.…”

Section: Numerical Modelsmentioning

confidence: 82%

“…A similar CFD simulation is carried out by Emhardt et al [35] to investigate the influence of the radial clearance on the www.videleaf.com performance of a scroll expander applied to small-scale ORC. In fact, decreasing the radial clearance from 200 µm to 75 µm, allows, on the one hand, to increase the isentropic efficiency from 31.9% to 53.9% but, on the other hand, to reduce the specific power output from 864.2 W to 336.5 W. The same research group also found that constant wall thickness scroll expander characterized by large built-in volume ratios allowed to achieve higher performance in small-sized ORC [36].…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Inner Fluid-Dynamics of Scroll Compressors and Comparison between CFD Numerical and Modelling Approaches

Cavazzini¹,

Giacomel²,

Benato³

et al. 2021

Advances in Energy Research

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Scroll compressors are widely adopted machines in both refrigeration systems and heat pumps. However, their efficiency is basically poor and constitutes the main bottleneck for improving the overall system performance. In fact, due to the complex machine fluid dynamics, scroll design is mainly based on theoretical and/or semi-empirical approaches. Designs strategies that do not guarantee an in-depth analysis of the machine behavior can be supplemented with a Computation Fluid Dynamics (CFD) approach. To this purpose, in the present work, the scroll compressor inner fluid dynamics is numerically analyzed in detail using two CFD software and two different modelling strategies for the axial gap. The analysis of the fluid evolution within the scroll wraps reveals unsteady phenomena developing during the suction and discharge phases, amplified by the axial clearance with negative impact on the main fluid flow (e.g., −13% of average mass flow rate for an axial gap of 30 µ) and on the scroll performance (e.g., +26% of average absorbed power for an axial gap of 30 µ). In terms of accuracy, the k-ε offers good performance on the estimation of average quantities but proves to be inadequate for capturing the complexity of the unsteady phenomena caused by the axial gap (e.g., −19% of the absorbed power in case of perfect tip seal). The need for Advances in Energy Research: 2 nd Edition 3 www.videleaf.com considering specific geometric details in design procedures is highlighted, and guidelines on the choice of the most suitable numerical model are provided depending on the analysis needs.

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“…It was found that scroll expanders with scrolls of variable wall thicknesses allow for the increase of the geometric expansion ratio without increasing the length of the scroll profiles, and thus avoiding the decrease in efficiency typical of constant wall thickness profiles; this feature is particularly useful for ORC systems as well as for refrigeration cycles and other power cycles where a high-pressure ratio enables higher performances. The same authors extensively studied the positive effects of a variable wall thickness scroll in [19,29,30] using a CFD modeling approach.…”

Section: Design and Technological Improvement Of Scroll Expandersmentioning

confidence: 99%

Feasibility Assessment of a Dual Intake-Port Scroll Expander Operating in an ORC-Based Power Unit

2022

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The main driver of research in the road transportation sector is almost certainly the development of technologies which allow for the reduction of CO2 emissions from internal combustion engines (ICEs). Wasted heat recovery (WHR) from the exhaust gases of ICEs based on organic rankine cycle (ORC) power units is one of the most promising technological solutions. However, several issues are raised when the recovery unit is scaled down to small applications, not to mention the fact that thermal sources are characterized by their intrinsically transient nature, as is the case with ICEs. In fact, this leads the ORC unit having to work frequently in off-design conditions. To successfully overcome this issue, the proper design and selection of the expanders are crucial. They are generally chosen from volumetric-type machines, thanks to their capacity to deal with time-varying thermo-fluid dynamic inlet properties. Among them, scroll machines represent one of the best solutions, despite them not yet being optimized as expanders, with them having been studied more as compressors. Dual-intake-port (DIP) technology is a novel solution used to enhance the performance of scroll machines. The effectiveness of this technology was assessed thanks to a comprehensive, experimentally-validated theoretical model of the scroll. It demonstrated that DIP technology can produce a 25% increase in mechanical power with respect to the baseline machine, without modifying the in–out pressure ratio. Maintaining a constant pressure difference across the expander at 5.6 bar, the power grew from 1131 W to 1410 W with the adoption of DIP technology. This power boost is lower than that achieved with a comparable DIP sliding rotary vane expander (SVRE) already studied by the authors, but the DIP Scroll achieved a higher efficiency (50–60%) when compared to the DIP SVRE case (40%).

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CFD analysis of variable wall thickness scroll expander integrated into small scale ORC systems

Cited by 19 publications

References 2 publications

CFD modelling of small scale ORC scroll expanders using variable wall thicknesses

CFD modelling of small scale ORC scroll expanders using variable wall thicknesses

Analysis of the Inner Fluid-Dynamics of Scroll Compressors and Comparison between CFD Numerical and Modelling Approaches

Feasibility Assessment of a Dual Intake-Port Scroll Expander Operating in an ORC-Based Power Unit

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