Energy and exergy analysis of parabolic trough collectors

In this paper, the effect of evacuated glass cover on convective heat loss and exergetic efficiency is studied. First, the evacuated receiver tube of LS-2 parabolic trough collector is simulated and analyzed with computational fluid dynamics (CFD). The results have good agreements with tested results. Secondly, this mentioned collector and its absorber tube are simulated without evacuated glass cover for various wind speeds and collector orientations. Finally, exergetic analysis of each case-studies are calculated and effect of wind blast and collector orientation on the exergy destruction and exergy loss are investigated. It is found that when wind blows on the convex side of the parabolic mirror, the impressibility of outlet temperature from wind speed is least than other orientations. Also, if the wind blows on the convex side of the parabolic mirror, the impressibility of outlet temperature from the variation of orientation is most than other orientations. Therefore exergy efficiency of collector will be decreases. With increasing of wind blast, the exergy loss and the destruction of collector increase. Therefore exergy efficiency of collector will be decreases. Also, using evacuated tube leads to increasing of exergy from 10 to 60 percents.