Review on Experimental Investigation for ThermalPerformance of Evacuated Tube Collector

Solar water heaters ( SHWs ) which are now widely used in Iran, has drawn many engineers and manufacturers attention to itself. For the efficient and effective performance of water heaters, saving of the hot water is the main subject in this water heating systems. This paper mainly presents a review of exergy and energy analysis of evacuated tube solar collectors and asserting some examples investigated by some of renowned researchers.When the solar radiation falls on the evacuated tubes, this energy is absorbed by the tubes and transferred to water with natural conduction and convection. A natural circulation of water occurs due to the inclination in tubes and header. Solar water heaters with evacuated tube collectors perform better than those of flat plate collectors. The usage of evacuated tube collectors is increasing day by day. The space requirement for mounting these collectors in congested cities is a problem faced by solar industry. Mounting the collectors on the wall invertical orientation will be the easiest solution to the problem. For flat plate collectors it is essential that the inclination of the collectors should be based on the latitude of that place for better performance, but for evacuated tube collectors, there exist no proof that the performance will be best for a particular angle of inclination