Optimal placement of radiation shields in the displacer of a Stirling engine

Rinker, Garrett; Solomon, Laura; Qiu, Songgang

doi:10.1016/j.applthermaleng.2018.08.042

Cited by 7 publications

(6 citation statements)

References 28 publications

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“…The remaining parabola is drawn by extending the sag line from a in1 to a 1 = 0 mm (represented as dashed grey line) and has its vertex on the origin point (0, 0). The parabolic ring segment of the RAC model (solid blue sag line) is found by subtracting the h a1 in Y-axis from the virtual parabola, which ensures the focus in the origin point [Colour figure can be viewed at wileyonlinelibrary.com] The H n is the height of the ring, given by Equation (6).…”

Section: Rac Design Methodologymentioning

confidence: 99%

“…2,3 Fresnel lens concentrators are widely used in photovoltaic technology; however, these lenses have a limited concentration ratio due to their strong chromatic aberration issue. 4,5 The use of high solar flux benefits heatto-electricity conversion by Stirling engines [6][7][8][9] and organic Rankine cycle engines 10 ; direct light-to-material interaction, energetic transition from other non-renewable sources 11 ; high-power solar-pumped lasers [12][13][14][15][16] ; energy heat storage. [17][18][19][20] The existing parabolic mirrors have their own specific characteristics depending on their size and application, as shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…This is highly desirable and suitable for the aforementioned applications. [6][7][8][9][10][12][13][14][15][16][17][18][19][20] Furthermore, with the adoption of the RAC, the negative effect of the receiver's shadows on the performance of the concentrators will no longer be a serious concern for many applications.…”

Section: Introductionmentioning

confidence: 99%

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Analytical and numerical analysis of a ring‐array concentrator

Garcia

Liang

Almeida

et al. 2021

Intl J of Energy Research

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The maximum achievable solar concentration of a single reflective primary parabolic mirror is limited by its physical aspect ratio. The maximum concentration of a single refractive Fresnel lens is also largely limited by its chromatic aberration. To resolve these shortcomings, a ring-array concentrator (RAC) analytical model with variable aspect ratio is proposed here. The concentrator was composed of seven concentric parabolic reflective rings and a small Fresnel lens at the centre. A novel ring height modifier parameter (h d ) was integrated into the design model, which was complemented with the width of the rings (d w ), allowing the modification of each individual ring height. Different seven ring models were provided. Concentrated solar flux and optical efficiency were investigated with ZEMAX ray-tracing software for each model. Over 18 W/mm 2 concentrated solar flux and 54% optical efficiency were numerically achieved for most of these models. Novel ring-array designs with low total ring surface areas and low aspect ratios were also discussed. The best RAC concentrator configuration was found at d w = 60 mm and h d = 27.5 mm, which showed the highest concentrated solar flux of 18.7 W/mm 2 , high optical efficiency of 54.75%, while maintaining a moderate total RAC surface area of 1.81 m 2 and low aspect ratio of 0.50. The solar angle interaction and the associated tracking error were also studied. The proposed RAC model may constitute a very useful tool for designing advanced RACs by considering the strong influence of h d and d w on the key design parameters like concentrated solar flux, optical efficiency, total RAC surface area and aspect ratio.

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Section: Rac Design Methodologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analytical and numerical analysis of a ring‐array concentrator

Garcia

Liang

Almeida

et al. 2021

Intl J of Energy Research

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“…Zemax non-sequential ray-tracing and Ansys finite element analyses were both used to evaluate the temperature of both the ESFL and the flat Fresnel lens at the Z position with the highest concentration solar flux found in Section 4.1. Ansys allows thermo-optical calculations that deal with complex geometric shape and boundary conditions, enabling the approximation of variables in a volume or surface element that changes across the matrix [46][47][48].…”

Section: Temperature Analysis Of Both the Esfl And The Flat Fresnel Lensmentioning

confidence: 99%

Elliptical-Shaped Fresnel Lens Design through Gaussian Source Distribution

et al. 2022

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A novel three-dimensional elliptical-shaped Fresnel lens (ESFL) analytical model is presented to evaluate and maximize the solar energy concentration of Fresnel-lens-based solar concentrators. AutoCAD, Zemax and Ansys software were used for the ESFL design, performance evaluation and temperature calculation, respectively. Contrary to the previous modeling processes, based on the edge-ray principle with an acceptance half-angle of ±0.27° as the key defining parameter, the present model uses, instead, a Gaussian distribution to define the solar source in Zemax. The results were validated through the numerical analysis of published experimental data from a flat Fresnel lens. An in-depth study of the influence of several ESFL factors, such as focal length, arch height and aspect ratio, on its output performance is carried out. Moreover, the evaluation of the ESFL output performance as a function of the number/size of the grooves is also analyzed. Compared to the typical 1–16 grooves per millimeter reported in the previous literature, this mathematical parametric modeling allowed a substantial reduction in grooves/mm to 0.3–0.4, which may enable an easy mass production of ESFL. The concentrated solar distribution of the optimal ESFL configuration was then compared to that of the best flat Fresnel lens configuration, under the same focusing conditions. Due to the elliptical shape of the lens, the chromatic aberration effect was largely reduced, resulting in higher concentrated solar flux and temperature. Over 2360 K and 1360 K maximum temperatures were found for ESFL and flat Fresnel lenses, respectively, demonstrating the great potential of the three-dimensional curved-shaped Fresnel lens on renewable solar energy applications that require high concentrations of solar fluxes and temperatures.

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“…This method allows thermal-optical calculation that deal with complex geometric shape and boundary conditions, enabling the approximation of variables in a volume or surface element that changed across the element. Thus, the variation of the field variables can be specified to increase degrees of approximations (An et al, 2005) (Li et al, 2015) (Rinker et al, 2018) (Khalil et al, 2019).…”

Section: Fig 4 Rac Solar Flux As a Function Of The First Width Ringmentioning

confidence: 99%

A three-dimensional ring-array concentrator solar furnace

et al. 2019

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A single ring-array concentrator solar furnace unit was firstly modeled analytically, and then optimized numerically by ZEMAX ® and ANSYS ® software, reaching a temperature of 3778 K, nearly equivalent to that of a medium size solar furnace with 3.14 m 2 collection area. A novel three-dimensional ring array concentrator solar furnace was subsequently proposed and analyzed. It consisted of five single ring array concentrators, forming a compact box-shaped solar furnace with an opening at the rear side for an easy access to a common focal spot in the center. Based on the edge-ray principle of non-imaging optics, 3.53 times higher concentration ratio was analytically calculated for this three-dimensional solar furnace, as compared to that of the medium size solar furnace, leading to significantly enhanced thermal and optical efficiencies. The temperature performance of the three-dimensional ring-array concentrator furnace as a function of receiver size and collector area was analyzed numerically and compared to that of the medium size solar furnace. For a 5.68 mm diameter spherical receiver and large collection area varying from 3.14 m 2 to 100 m 2 , 1.1 times gradual enhancement in the maximum attainable temperature was calculated for the ring array concentrator furnace. More importantly, its average and minimum temperatures were significantly improved by 870 K and 1140 K, respectively, as compared to that of the medium size solar furnace. With convection loss, the 3D RAC solar furnace also more efficient in attaining maximum temperature than that by the parabolic mirror furnace. In addition, the three-dimensional ringarray concentrator also presented a significant tracking error compensation capacity in relation to that with the medium size solar furnace.

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Optimal placement of radiation shields in the displacer of a Stirling engine

Cited by 7 publications

References 28 publications

Analytical and numerical analysis of a ring‐array concentrator

Analytical and numerical analysis of a ring‐array concentrator

Elliptical-Shaped Fresnel Lens Design through Gaussian Source Distribution

A three-dimensional ring-array concentrator solar furnace

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