The effect of variable cross sectional tubes on the performance of flat plate solar collectors

Flat plate solar collectors are the heart of domestic solar water heating system, due to their permanent position, simple construction, low cost and require little maintenance. The major purpose of this work is to estimate numerically the performance of flat plate solar storage collectors and investigate the thermal enhancement by enhancement of dimensions and geometry. Five types of flat plate storage solar collectors were examined for Iraq-Baghdad climate conditions with tilt angle at 33.33o. These types of collectors were flat plate solar storage collectors, which are trapezoidal, ellipsoidal, circular, square and triangle models. The analysis of these collectors is according to the absorption of solar radiation, heat loss from the collectors, temperature distribution of absorber and the working fluid flowing through the collectors. The collectors are simulated utilizing Matlab program. Comparisons between the calculated & measured results of outlet and inlet water temperatures was performed, it indicated a satisfactory agreement. Theoretical results show that highest outlet temperatures were 60.53 ˚C, 60.83 ˚C, 60.2 ˚C, 59.51 ˚C and 58.63 ˚C, at solar noon in the five models, respectively. Maximum values of efficiencies were calculated 57.2%, 56.48%, 56%, 55.52% and 54.53% in five models.