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Research Papers

Secondary Concentrators to Achieve High Flux Radiation With Metal Halide Solar Simulators

[+] Author and Article Information
Xue Dong

Centre for Energy Technology,
School of Chemical Engineering,
The University of Adelaide,
Adelaide, SA 5005, Australia
e-mail: xue.dong@adelaide.edu.au

Graham J. Nathan, Zhiwei Sun, Dahe Gu

Centre for Energy Technology,
School of Mechanical Engineering,
The University of Adelaide,
Adelaide, SA 5005, Australia

Peter J. Ashman

Centre for Energy Technology,
School of Chemical Engineering,
The University of Adelaide,
Adelaide, SA 5005, Australia

Manuscript received August 23, 2015; final manuscript received March 6, 2016; published online April 5, 2016. Assoc. Editor: Wojciech Lipinski.

J. Sol. Energy Eng 138(4), 041001 (Apr 05, 2016) (10 pages) Paper No: SOL-15-1272; doi: 10.1115/1.4032943 History: Received August 23, 2015; Revised March 06, 2016

This paper presents assessments of the sensitivity of the performance of high flux solar simulators to the key variables of conical secondary concentrators for metal halide lamps, which offer complementary benefits compared with xenon arc lamps. The assessment is performed for both a single-lamp configuration and a seven-lamp array, each lamp close-coupled with its own elliptical reflector, and then aligned with a common conical secondary concentrator. The simulation of heat flux from both the single- and the seven-lamp systems was performed with the Monte Carlo ray-tracing code, which was validated with the experimental results from the single-lamp system. The calculated heat flux at the focal plane agrees with the measured peak flux to within 5% and to within 13% of the measured half width. Calculated results also show that the addition of the secondary concentrator to the single-lamp system can increase the peak flux by 294% and the average flux by up to 93% within a target of 100 mm in diameter, with a corresponding reduction in total power by 15%. The conical secondary concentrator is less effective for a seven-lamp system, increasing the peak and average fluxes by 87.3% and 100%, respectively, within 100 mm diameter focal plane, with a corresponding reduction in total power by 48%. The model was then used to assess the sensitivity of the geometry of the secondary concentrators for both the single- and seven-lamp systems. The results show that the average heat flux is sensitive to the surface reflectance of the secondary concentrator, with the average flux decreasing almost linearly with the surface reflectance. The presence of the secondary cone greatly reduces the sensitivity of the concentrated heat flux to misalignment of the tilting angle of the elliptical reflector relative to the arc.

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Figures

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Fig. 1

Schematic diagram of the configuration of the single-lamp solar simulator, together with the terminology used to define the dimensions of the conical secondary concentrators. The outlet plane of the secondary concentrator is aligned with the focal plane of the elliptical reflector for all the cases assessed with the single-lamp system, i.e., S + L = 3 m.

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Fig. 2

Arrangement of the seven-lamp solar simulator: (a) front view and (b) side view. The focal length of each elliptical reflector is 3 m.

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Fig. 3

Heat flux at a plane 50 mm down-beam from the outlet of the secondary concentrator for the single-lamp system: (a) the planar measurement, (b) the planar ray-tracing simulation, and (c) the comparison between the measured and simulated heat flux. The error-bar of ± 3% for the measurement was determined from the accuracy of the heat flux transducer.

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Fig. 4

Normalized line of sight radiation as measured from the arc and as calculated with the assumptions of the multilayer arc model described previously [12]

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Fig. 5

Sensitivity of the simulated heat flux to the surface reflectance of the secondary cone for the single-lamp system. Radiant flux was acquired at the outlet plane of the conical secondary concentrator at constant L = 1000 mm, θ = 10 deg, and d = 50 mm.

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Fig. 6

Sensitivity for the single-lamp system of the simulated heat flux at the outlet of the cone, to the half angle of the secondary cone. Data are reported for various cases of D at constant R = 0.95 and L = 1000 mm.

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Fig. 7

Sensitivity for the seven-lamp system of the simulated heat flux to the half angle θ of the secondary cone. Radiant flux acquired at the outlet of the secondary cone, varying D at constant R = 0.95, L = 600 mm, and S1 = 0.

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Fig. 8

Sensitivity for the seven-lamp system of the simulated heat flux to the length L of the secondary cone, varying L and D at constant R = 0.95, θ = 24.5 deg, and S1 = 0

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Fig. 9

(a) Sensitivity of the simulated heat flux to the outlet diameter d of secondary concentrator for the seven-lamp system, varying d at constant θ = 24.5 deg and R = 1. (b) Sensitivity of the simulated heat flux to the surface reflectance of the secondary concentrator for the seven-lamp system at constant θ = 24.5 deg, L = 600 mm, d = 100 mm, and S1 = 0.

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Fig. 10

Sensitivity of the simulated heat flux to the misalignment of the elliptical reflector relative to the lamp for the cases with and without the conical concentrator for (a) a single-lamp system and (b) a seven-lamp system. Heat flux was calculated with θ = 10 deg, L = 1000 mm, d = 200 mm, and R = 0.95 for the single-lamp system, while that for the seven-lamp system is θ = 24.5 deg, L = 600 mm, d = 200 mm, R = 0.95, and S1 = 0. The conical secondary concentrators applied are in their aligned positions.

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Fig. 11

Arrangement of the seven-lamp solar simulator with both the secondary concentrator and the conical back reflector. The distance bewtween the focal plane and the outlet of the secondary concentrator is S1 and that between the focal plane to the inlet of the conical back reflector is S2. D3 and L3 are the diameter and depth of the conical back reflector, respectively.

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Fig. 12

Sensitivity of the simulated heat flux to the geometry of the tertiary cone for the seven-lamp system, varying D3 and L3, at S1 = 50 mm, S2 = 50 mm, L = 600 m, and θ = 24.5 deg. Heat flux is calculated at the focal plane of (a) 50 mm, (b) 100 mm, and (c) 150 mm diameter, respectively. Reflectance of all the reflecting surface is 0.95.

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Fig. 13

Sensitivity of the simulated heat flux to the surface reflectance of the conical back reflector for the seven-lamp system, with D3 = 100 mm, L3 = 20 mm, θ = 24.5 deg, L = 600 mm, d = 100 mm, S1 = 50 mm, and S2 = 50 mm. Heat flux is calculated at the focal plane of 100 mm. Reflectance of all the other reflecting surface is 0.95.

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