Numerous papers were devoted to various aspects of theory, numerical simulation, and experimental investigation the expected date of free convection heat transfer from flat isothermal plates. This is due to the wide range of engineering applications of the heated or cooled isothermal plates in power-engineering, heat-exchange and process equipment for power generation, aerospace, chemical and oil-processing industry, transport, and commercial heat power engineering. In addition to the limiting cases of flow adjacent to vertical and horizontal surfaces, the intermediate case of inclined plates has also been examined by a number of investigators. Almost all of the experimental and theoretical results, found in the literature on this subject are summarized in the paper. The results of the different investigations of convective heat transfer from horizontal, vertical and inclined plates have shown a span range of about 50% from the mean value. The principal reasons for this divergence are in the differences among the models and mechanisms proposed to explain heat transfer in different configurations, experimental equipment precision, data analysis methods.