About this Journal Submit a Manuscript Table of Contents
Advances in Materials Science and Engineering
Volume 2012 (2012), Article ID 158067, 8 pages
http://dx.doi.org/10.1155/2012/158067
Research Article

Modeling Approach for Determining Equivalent Optical Constants of Plastic Shading Nets under Solar Radiation Conditions

1Department of Agricultural Engineering, College of Food and Agriculture Sciences, King Saud University, P.O. Box 2460, Riyadh 11451, Saudi Arabia
2Mechanical Power Engineering Department, Faculty of Energy Engineering, South Valley University, Aswan 81528, Egypt

Received 16 February 2012; Accepted 3 August 2012

Academic Editor: Fengqiang Sun

Copyright © 2012 A. M. Abdel-Ghany and I. M. Al-Helal. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The radiative properties of several plastic shading nets were measured under natural solar radiation conditions. We found that the plastic nets behave as homogeneous translucent materials (e.g., plastic film, plastic sheets, and glass). Based on this behavior, we suggest that it is possible to treat plastic nets as translucent materials and to characterize them with equivalent optical constants (i.e., equivalent refractive indexes, 𝑛eq, and equivalent extinction coefficients, 𝜎eq). Here a physical model to determine 𝑛eq and 𝜎eq of plastic nets was described in analogy to homogeneous translucent materials. We examined three groups of nets based on their color (black, black-green, and beige). Each group consisted of nets with four or five different porosities. Nets of each group had almost the same texture structure. For each group, we derived an equation for 𝑛eq as a function of the net porosity and determined an average value for 𝜎eq. Once values of 𝑛eq and 𝜎eq were determined, the solar radiative properties of a net could then be calculated from 𝑛eq and 𝜎eq for any incident angle of solar beam radiation without the need of measurements. The present model was validated by comparing the calculated with the measured radiative properties of three nets at different incident angle of solar beam radiation. The calculated radiative properties reasonably agreed with measured values.