Thermal Difference Between a Classic Solar Collector Evacuated Tube and One with a Thermosyphon Flow Tube
Abstract
In order to diminish the environmental problems it is urgent to look for energy alternative sources that help to decreasing of pollutant agents, besides taking advantage of the renewable resources, as it is the solar energy case, especially in a country like Mexico, that receives a high solar radiation quantity, 25 MJ m-2 day1, but is even in an incipient development and use of this technology. In Mexico the use of solar heating water technology is gradually growing. The design of flat plate finned tubes solar collector has dominated the market and has a great number of national manufacturers of this equipment. Nevertheless, in the last five years, the technology of solar collectors of evacuated tubes produced abroad, are becoming to dominate the national market and now exist a great amount of solar distributors of this equipment that begins to displace the solar manufacturers at the country. However, the evacuated tubes solar collectors, by their own design, enormously low their yield by the amount of accumulated fouling in the tubes, especially when high content of hardness water (more than 250 mg L-1 like calcium carbonate) is used, what it is very common in our country. With this problem occurring in the evacuated tubes of solar collectors, we have proposed to redesign a system of evacuated tubes in order to have a tube with an entrance and one exit emulating to a finned tube in a thermosyphon flow in opposition to the classical evacuated tube, in order to observe the differences in efficiency of both systems . The hypothesis of the present work was that the evacuated tube must be open on both sides, thus promoting a straightforward thermal circulation of the work fluid into the tube to the water thank, increasing the thermal efficiency in relation to the classical evacuated tube set-up, which has only one open side.