Effect of Glass Thickness on Performance of Flat Plate Solar Collectors for Fruits Drying

This study aimed at investigating the effect of thickness of glazing material on the performance of flat plate solar collectors. Performance of solar collector is affected by glaze transmittance, absorptance, and reflectance which results into major heat losses in the system. Four solar collector models with different glass thicknesses were designed, constructed, and experimentally tested for their performances. Collectors were both oriented to northsouth direction and tilted to an angle of 10° with the ground toward north direction. The area of each collector model was 0.72？m2 with a depth of 0.15？m. Low iron (extra clear) glass of thicknesses 3？mm, 4？mm, 5？mm, and 6？mm was used as glazing materials. As a control, all collector performances were analysed and compared using a glass of 5？mm thickness and then with glass of different thickness. The results showed that change in glass thickness results into variation in collector efficiency. Collector with 4？mm glass thick gave the best efficiency of 35.4% compared to 27.8% for 6？mm glass thick. However, the use of glass of 4？mm thick needs precautions in handling and during placement to the collector to avoid extra costs due to breakage. 1. Introduction In many countries, the use of solar drying systems for agricultural products to conserve vegetables, fruits, and other crops has been shown to be practical, inexpensive, and environmentally sound approach [1]. Solar dryers offer a cheaper and an alternative way of processing fruits and vegetables in clean and hygienic condition within international standards. Moreover, they save time, occupy less area, improve product quality, protect the environment, and provide better control of required drying air condition [2]. However, the availability of good information is lacking in many countries, where food-processing systems are mostly needed [1, 3]. Centrally to that, indirect cabinet dryer with forced convection flow is one of the best drying methods which can produce high-quality products and eliminate the risk of spoilage during drying [4, 5]. Although solar air collector is a very important component in the solar drying system, it has not received much attention during dryer design [6]. In theory, the performance of solar collector depends on climatic conditions and several operating condition such as collector orientation, thickness of cover materials, wind speed, collector length, collector depth, and the type of absorber material used [7–11]. Currently, these factors are not well considered during solar system design. Therefore, development of a