Аннотация
The given work presents the methodology of computing the entropy generating and researching the thermal characteristics for thermosiphon flat solar collector. Heat losses in the flat solar collectors are computed using the thermal losses upper factor. The work herein discusses the methodology, based on the 2nd law of thermodynamics, which provides an accurate technique of assessing the heat losses in the flat solar collectors. Entropy generation in the collector is linked, mainly, with the modes of heat conductivity and convection. Collector's heat losses happen, mostly, at the expense of the heat transfer modes thereof. As well there has been computed the heat quantum transmitted by irradiation onto an internal solar collector glass surface.