Effects of stratification on the performance of solar air heating systems

A theoretical model is presented which predicts the effects of stratification in the rock bed storage unit of a solar air heating system. The results are presented in terms of a stratification coefficient which is defined to be the ratio of the actual useful energy gain to the energy gain that would be achieved if the rock bed were maintained at a uniform temperature. This stratification coefficient is shown to be a system constant which depends on only three dimensionless system parameters.