Effect of the Circulation Number on the Stratification Coefficient for Solar Heating Systems

Abstract

The effect of the circulation number (the number of times the entire storage mass is circulated through the system each day) on the stratification coefficient is investigated. An earlier model ignored the effect of the circulation number, assuming that a large value (a value > 2) did not have any effect. In this paper, an analytical model is developed to consider the effect of low circulation number. This model is combined with the previous model and a general expression for the stratification coefficient is developed that is valid for the entire range of circulation number. The extended analytical model is verified through numerical simulations. The results are valid for liquid-based as well as air heating systems. Clarifications are made regarding the definition of the stratification coefficient by introducing a concept of an instantaneous stratification coefficient.