MATHEMATICAL MODEL USING FOR ANALYSIS OF THE HEAT OPERATION OF CONCRETE SOLAR COLLECTOR

Abstract

Concrete solar collectors have long been used as low-temperature water heaters, for example for water heating in swimming pools. Their main advantages are cheapness, simplicity of realization and high operational qualities. One of the modern directions of concrete solar collector development is their integration into facades of buildings and constructions. They can be integrated to historical buildings without compromising the building’s appearance. The advantage of such systems is their aesthetics and structural strength, as they do not contain a brittle glass coating. At the same time, non-glazed absorbers, especially in the cold season and at night, can have significant heat loss due to convective heat exchange with the ambient air, as well as by long-wave radiation into the atmosphere. A mathematical model was used to analyze the influence of various factors upon the heat operation of a solar system with concrete collector. It calculates the changes of direct and diffused solar radiation on the collector surface during the day, taking into account the surface location and orientation, and time of year and day. The model solves the problem of non-stationary heat conductivity in a concrete absorber with a built-in pipes system with circulating liquid and storage tank. The daily water consumption mode is taken into account by changing the water flow rate to the circulation pump. The model was used to analyze the concrete collectors operating under Ukrainian conditions. The comparative calculations of heat operation of glazed and unglazed concrete collector were performed. It is shown that the efficiency of the solar system is significantly affected by the storage tank volume and the mode of water withdrawal, when concrete collector operating under closed-circuit conditions. This is due to the fact that after a sunny day much of the accumulated heat can be lost to the environment. Була вивчена можливість кращого використання накопиченого тепла, накопиченого поглиначем бетону після закінчення сонячного дня, за рахунок збільшення обсягу накопичувального резервуару та різних режимів розвантаження резервуарів.