EXPERIMENTAL AND THEORETICAL ANALYSIS OF THE HIGH FLUX - HIGH TEMPERATURE FIELD IN A DIELECTRIC SUBJECTED TO INTENSE SOLAR RADIATION

LARRYL KENT MATTHEWS, Purdue University

Abstract

The primary objective of this study has been to develop procedures and models for studying heat transfer in absorbing, emitting and highly scattering materials subjected to intense solar radiation; and to develop a methodology for determining parameters from data taken in the environment in which these materials are used. A theoretical model was constructed to describe the heat transfer mechanisms in the semitransparent materials and to be used for predicting and determining the role of thermal parameters (thermal conductivity and specific heat) and radiation parameters (single scattering albedo, extinction coefficient, back scattering fraction and index of refraction (real part)) on heat transfer across such materials. The theoretical model was used to perform a sensitivity analysis for the parameters. Of the aforementioned radiation parameters, the single scattering albedo was found to be the most important for the semitransparent materials being studied in this work. This is due in part to the single scattering albedo being close to unity ((TURN)0.99). For the thermal parameters, the sensitivity analysis found that the thermal conductivity and the specific heat were equally significant over the temperature range being studied. Nonlinear parameter estimation (inversion) techniques were used to determine the parameters from data taken using zirconia. Zirconia was used as the example material to demonstrate the procedures developed in this study. The zirconia was tested in a solar furnace with incident heat fluxes of 400 kW/m('2) and 600 kW/m('2). The parameters determined in this study are only estimates of the true values, due to the need to acquire more data. However, the theoretical model, along with the parameters, was able to calculate transmitted heat flux and reflected heat flux to within the error bounds (in most cases) of the data. In addition, the model calculated temperatures to within an average of 10% of the measured temperatures in the zirconia. Recommendations are given, along with an error analysis of the study, to improve the estimation of the parameters and the quality of the data.

Degree

Ph.D.

Subject Area

Mechanical engineering

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