Dynamic Modeling of Natural Convection Solar Energy Collectors for Agricultural Driers I: Theory and Complete Run of the Solutions to the Dynamic Model Equations of SSSCA Flat Plate Collector

Abstract

An analysis is made of the dynamic model of a flat plate solar energy collector to be employed in natural convection solar energy driers used for drying agricultural products like meat, fish, grains and vegetables and bring them to acceptable equilibrium moisture content to avoid spoilage when stored. Analytical solutions of the derived model equations enabled expressions for the mean glazing, absorber and outlet fluid temperatures to be obtained. Expressions were also obtained for the collector instantaneous energy delivery rate, efficiency, heat removal factor, and combined plates coefficient of performance (formally called plates efficiency). A plot of the collector output parameters against time from Os (at 6.00a/m.) showed that each possessed a maximum, which occurred between 1800s and 3600s after solar noon where global radiation had its maximum. The shift is attributable to the heat capacities of the materials of the collector Separation of the transient terms from the steady- state terms for the plates' temperatures showed the transient contribution to be very small and practically die out between 14400s and 16200s from start, showing that the transient terms can be neglected. This was confirmed when the transient terms were completely deleted as the maximum values of the output parameters and their times of occurrence remained the same in both cases. The developed output expressions (in closed form) for the dynamic model of flat plate solar energy air heating collectors can easily be used for optimization studies and design of better air heating solar energy collectors.