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Technical Briefs

Temperature of a Quartz/Sapphire Window in a Solar Cavity-Receiver

[+] Author and Article Information
G. Maag, C. Falter

Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland

A. Steinfeld1

Department of Mechanical and Process Engineering, ETH Zurich, 8092 Zurich, Switzerland; Solar Technology Laboratory, Paul Scherrer Institute, 5232 Villigen, Switzerlandaldo.steinfeld@ethz.ch

Fraction of energy flux emitted by a blackbody surface stretched across the cavity opening that is absorbed by the cavity walls (1).

1

Corresponding author.

J. Sol. Energy Eng 133(1), 014501 (Nov 23, 2010) (4 pages) doi:10.1115/1.4002774 History: Received March 25, 2010; Revised October 09, 2010; Published November 23, 2010; Online November 23, 2010

Radiation heat transfer within a high-temperature solar cavity-receiver containing a windowed aperture exposed to concentrated solar radiation is solved using the gray-band approximated radiosity method for semitransparent enclosures. Spectrally selective quartz and sapphire are examined for window materials. Window and cavity temperatures are calculated as a function of the incoming radiative flux and solar energy absorption efficiency. For validation and comparability, a windowless cavity is analyzed. Due to its relatively high reflectance in the visible spectrum, the sapphire window requires higher inlet solar radiative flux than the quartz window to obtain the same reactor temperature and energy absorption efficiency.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the solar cavity-receiver configuration

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Figure 2

Temperatures of (a) window and (b) cavity as a function of incoming solar radiative flux qsolar. The parameter is the solar energy absorption efficiency, η=0, 0.4, 0.6, and 0.8, for both window types and the windowless case.

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Figure 3

Fraction of total losses by emission, reflection, transmission, and natural convection as a function of the window temperature and the solar energy absorption efficiency for both window types with qsolar=3.0 MW m−2

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