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.
evacuated absorber tube, parabolic trough collector, exergetic efficiency, exergy destruction, exergy loss
 Clark JA. (1982). An analysis of the technical and economic performance of a parabolic trough concentrator for solar industrial process heat application. International Journal of Heat and Mass Transfer 25(9): 1427–1438. https://doi.org/ 10.1016/0017-9310(82)90136-3
 Almanza R, Lentz A, Jimenez G. (1997). Receiver behavior in direct steam generation with parabolic troughs. Solar Energy 61(4): 275–278. https://doi.org/ 10.1016/S0038-092X(97)88854-8
 Odeh SD, Morrison GL, Behnia M. (1998). Modelling of parabolic trough direct steam generation solar collectors. Solar Energy 62(6): 395–406. https://doi.org/ 10.1016/S0038-092X(98)00031-0
 Shahraki F. (2002). Modeling of buoyancy-driven flow and heat transfer for air in a horizontal annulus: effects of vertical eccentricity and temperature-dependent properties. Numerical Heat Transfer Part A – Applications 42(6): 603–621. https://doi.org/ 10.1080/10407780290059729
 Naeeni N, Yaghoubi M. (2007). Analysis of wind flow around a parabolic collector (1) fluid flow. Renewable Energy 32(11): 1898–1916. https://doi.org/ 10.1016/j.renene.2006.10.004
 Kassem T. (2007). Numerical study of the natural convection process in the parabolic-cylindrical solar collector. Desalination 209(1-3): 144–150. https://doi.org/ 10.1016/j.desal.2007.04.023
 Shuai Y, Xia XL, Tan HP. (2008). Radiation performance of dish solar concentrator/cavity receiver systems. Solar Energy 82(1): 13–21. https://doi.org/ 10.1016/j.solener.2007.06.005
 Bejan A, Kearney DW, Kreith F. (1981). Second law analysis and synthesis of solar collector systems. ASME Journal of Solar Energy 103(1): 23–28. https://doi:10.1115/1.3266200
 Bejan A. (1982). Extraction of exergy from solar collectors under time-varying conditions. International Journal of Heat and Fluid Flow 3(2): 67–72. https://doi.org/ 10.1016/0142-727X(82)90002-9
 Kurtbas I, Durmus A. (2004). Efficiency and exergy analysis of a new solar air heater. Renewable Energy 29(9): 1489–1501. https://doi.org/ 10.1016/j.renene.2004.01.006
 Bakos GC, Ioannidis I, Tsagas NF, Seftelis I. (2001). Design optimization and conversion-efficiency determination of a line-focus parabolic-trough solar collector (PTC). Applied Energy 68(1): 43–50. https://doi.org/ 10.1016/S0306-2619(00)00034-9
 Dudley V, Kolb G, Sloan M, Kearney D. (1994). SEGS LS2 solar collector — test results. Report of Sandia National Laboratories. SANDIA94-1884, USA.
 He Y, Xiao J, Cheng Z, Tao, Y. (2011). A MCRT and FVM coupled simulation method for energy conversion process in parabolic trough solar collector. Renewable Energy 36(3): 976–985. https://doi.org/ 10.1016/j.renene.2010.07.017
 Tao WQ. (2001). Numerical Heat Transfer. Second Ed, Xi'an Jiaotong University Press, Xi'an.
 DiPippo R. (2004). Second Law assessment of binary plants generation power from low-temperature geothermal fluids. Geothermics 33(5): 565-586. https://doi.org/ 10.1016/j.geothermics.2003.10.003
 Kotas TJ. (1995). The exergy method of thermal plant analysis. Malabar. FL: Krieger Publish Company.
 Bejan A. (1988). Advanced engineering thermodynamics. New York: Wiley Interscience. 133–137, 462–465.
 Petela R. (1964). Exergy of heat radiation. ASME Journal of Heat Transfer 86(2): 187–192. https://doi 10.1115/1.3687092
 Najian MR. (2000). Exergy analysis of flat plate solar collector. M.Sc. dissertion. Department of Mechanical Engineering, Tehran University, Tehran, Iran.
 Torres-Reyes E, Cervantes de Gortari JG, Ibarra-Salazar BA, Picon-Nunez M. (2001). A design method of flat-plate solar collectors based on minimum entropy generation. Exergy, An International Journal. 1(1): 46–52. https://doi.org/ 10.1016/S1164-0235(01)00009-7
 Khodayari Bavil A, Razavi SE. (2017). On the thermo-flow behavior in a rectangular channel with skewed circular ribs. Mechanics & Industry 18(2): 225. https://doi.org/ 10.1051/meca/2016057
 Dutta Gupta KK, Saha SK. (1990). Energy analysis of solar thermal collectors. Renewable Energy and Environment 283–287.
 Suzuki A. (1988). General theory of exergy balance analysis and application to solar collectors. Energy 13(2): 153–160. https://doi.org/ 10.1016/0360-5442(88)90040-0
 Suzuki A. (1988). A fundamental equation for exergy balance on solar collectors. Journal of Solar Energy Engineering. 110(2): 102–106. https://doi.org/ 10.1115/1.3268238
 Luminosu I, Fara L. (2005). Determination of the optimal operation mode of a flat solar collector by exergetic analysis and numerical simulation. Energy 30(5): 731–747. https://doi.org/ 10.1016/j.energy.2004.04.061
 Cornelissen RL. (1997). Thermodynamics and sustainable development: the use of exergy analysis and the reduction of irreversibility. Ph.D dissertion. Department of Mechanical Engineering, University of Twente, Netherland.
 Sadaghiyani OK, Pesteei SM, Mirzae I. (2013). The Effect and Contribution of Wind Generated Rotation on Outlet Temperature and Heat Gain of LS-2 Parabolic Trough Solar Collector. Thermal Science 17(2): 377-386. https://doi. 10.2298/TSCI110613123S
 Tao WQ. (2001). Numerical Heat Transfer. Second Ed, Xi’an Jiaotong University Press, Xi’an, China.