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Economic and Energetic Analysis for Optimizing the Length of Flat-Plate Solar Air Heating Collectors

One dimensional steady state mathematical model has been developed for study the thermal behavior of two types of flat-plate solar air heating collectors. The model allows demonstration the influence of the collector's dimension leading to optimize the length of the collector. The model implemented numerically using finite-difference technique with mass flow rate of 0.01 kg/s per unit area of solar collector and the incident solar radiation equal to 900W/m2. The analysis has been done for a large range of areas. Illustrative results such as the temperatures of the components of the collectors (glass cover, absorber plate, air flowing through the collector and the rear plate), efficiency and useful heat extracted from the collector are graphically presented. The obtained results from both the energetic and economic analysis showed that, for the first type of the flat-plate solar air heating collector, the optimum length is 4.05 meters, moreover, it dawdles its energy collected past for lengths greater than 6 meters. There is no optimum length for the second type, but there is no much energy gain for lengths greater than 6 meters anyhow, the economic analysis showed that the length must be greater than 2.5 meters for both types of collectors.