Modified mathematical model for evaluating the performance of water-in-glass evacuated tube solar collector considering tube shading effect

In Egypt (30° Latitude angle), the results show that 10°, 30° and 45° are the optimum solar collector tilt angles during the summer, vernal and autumnal equinox and winter operation respectively. Also, the utilized solar energy increases about 2.8% when the mass flow rate increases 100%, and the solar collector with south-facing has the best performance except for vertical tube solar collector. The simulation results also show that solar collector with wide tube spacing reduce the shading effect and hence increase the absorbed radiation. The final tank temperature as a function of collector's mass flow rate for three different days; 21 March, 21 June and 21 December is also investigated. The total incidence radiation, absorbed solar radiation and utilized heat per tube are presented for the three optimum tilt angles 10°, 30° and 45°. Efficiency curve of water-in-glass evacuated tube collector is also set into comparison with flat plate solar collector and salt gradient solar pond.