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Research Papers

Effect of Cameralike Aperture in Quest for Maintaining Quasi-Constant Radiation Inside a Solar Reactor

[+] Author and Article Information
Nesrin Ozalp1

Department of Mechanical Engineering, Texas A&M University at Qatar, P.O. Box 23874, Doha 23874, Qatarnesrin.ozalp@qatar.tamu.edu

Anthony Toyama

Department of Mechanical Engineering, Texas A&M University at Qatar, P.O. Box 23874, Doha 23874, Qataranthony.toyama@qatar.tamu.edu

Jayakrishna Devanuri

Department of Mechanical Engineering, Texas A&M University at Qatar, P.O. Box 23874, Doha 23874, Qatarjayakrishna.devanuri@qatar.tamu.edu

Reza Rowshan

Department of Mechanical Engineering, Texas A&M University at Qatar, P.O. Box 23874, Doha 23874, Qatarreza.rowshan@qatar.tamu.edu

Yasser Al-Hamidi

Department of Mechanical Engineering, Texas A&M University at Qatar, P.O. Box 23874, Doha 23874, Qataryasser.al-hamidi@qatar.tamu.edu

1

Corresponding author.

J. Mech. Des 133(2), 021002 (Jan 24, 2011) (7 pages) doi:10.1115/1.4003179 History: Received January 25, 2010; Revised November 17, 2010; Published January 24, 2011; Online January 24, 2011

Solar reactors can convert intermittent solar radiation into storable chemical energy in the form of fuels that are transportable. In order to use solar energy as a source of high temperature process heat in a solar reactor, incident radiation needs to be concentrated over a small surface area, the inlet of which is called the aperture. The image of the incoming solar radiation over the aperture can be approximated by a Gaussian distribution where the solar radiation inside the reactor varies by the peak value and aperture size. Due to the transient nature of solar energy, there is a critical need for proper control to maximize system efficiency under field conditions. The objective of this paper is to present numerically proven advantages of having a camera-like variable aperture, one that is sensitive to natural variations in solar flux, and having the ability to shrink or enlarge accordingly in order to maintain quasi-constant radiation inside the reactor. Since the internal temperature has a major impact on reactant to product conversion efficiency, by maintaining the temperature constant, process efficiency is kept high. By maintaining the internal temperature despite transient operating conditions, the system can maintain peak performance through a wider insolation range than fixed aperture systems. Our numerical results from optical, thermodynamic, and flow dynamic simulations led us to develop a computational two dimensional heat transfer distribution model inside the reactor in order to validate our optical results. The combined simulation results show that correctly varying the aperture diameter with respect to transient incoming solar flux densities facilitates the maintenance of quasi-constant temperature distributions inside the reactor.

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Copyright © 2011 by American Society of Mechanical Engineers
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References

Figures

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Figure 3

Cross section of a generic cylindrical vortex-flow reactor. 200 mm long axis, 100 mm diameter. Z-Y plane.

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Figure 4

Flowchart of the aperture actuation and control systems

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Figure 5

Optical simulation model of the vortex-flow reactor, <1.0% of total rays shown. Z-Y plane.

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Figure 6

Simulated flux image created in TRACEPRO , Pin=5.67 kW, 8 cm diameter aperture, on back wall of reactor. X-Y plane.

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Figure 1

Generic aperture with blades (a) closed and (b) open. X-Y plane.

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Figure 2

Detail of the proposed variable aperture system. X-Y plane.

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Figure 9

Averaged reactor temperature results from optical and FLUENT simulations for various insolation and aperture diameters

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Figure 7

Pap as a function of aperture radius and Pin

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Figure 8

Temperature distribution within reactor cavity based on FLUENT simulation. Pin=5.67 kW, 4 cm aperture diameter. Z-Y plane.

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