New approach for thermal testing of solar dryer: Development of generalized drying characteristic curve

• Published in: Solar energy 2012-07, Vol.86 (7), p.1981-1991
• Main Authors: Singh, Shobhana, Kumar, Subodh
• Format: Article
• Language: English
• Subjects: Applied sciences; Comparative analysis; Dimensionless parameter; Dryer performance index; Drying kinetics; Electrical engineering. Electrical power engineering; Electrical power engineering; Energy; Exact sciences and technology; Food preservation; Generalized drying curve; Miscellaneous; Mixed-mode solar dryer; Moisture content; Musa; Natural energy; Power networks and lines; Solanum tuberosum; Solar energy; Testing. Reliability. Quality control; Triticum aestivum; Users connections and in door installation
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2012.04.001

► Single generalized drying curve representing 16 drying kinetics is developed. ► A dimensionless parameter, DPI is identified to determine effectiveness of dryer. ► DPI is found to be independent of operating conditions and food characteristics. ► DPI can therefore be used as performance index to compare different dryer designs. It is necessary to develop thermal test procedure that can assist performance comparison between various solar dryer designs on common basis. In order to achieve this objective, the laboratory model of mixed-mode solar dryer is specially designed to perform indoor drying experiments with cylindrical potato samples. Sixteen drying kinetic curves are obtained over a wide range of various drying process variables. The variables investigated are absorbed thermal energy, air mass flow rate, food sample thickness and loading density. Based on experimental data of moisture content ratio-drying time, new concept to develop standard test method for performance evaluation of a given dryer is proposed. The proposed methodology facilitates to generate single generalized characteristic curve representing 16 drying kinetics and dimensionless parameter called dryer performance index (DPI) characterising the effectiveness of dryer system is identified. Different solar dryers with potato, banana and wheat are also tested in real climatic conditions to validate the proposed methodology. DPI with consistent values for all test conditions, indicating high degree of independence of operating conditions and food product characteristics, can therefore be used as a test parameter for performance comparison between different dryer designs on equitable basis.