Empirical Model Rating Method of Heat Removal Efficiency for Vertical Mantle Storage Tanks

The heat removal efficiency of a storage tank is effective to evaluate the thermal energy that users can obtain during its heat removal phase. With different types and volumes V_t, from 174 L to 1093 L, of six vertical mantle storage tanks widely applied to heat pumps and solar heating systems, the analyses of heat removal patterns were carried out. In addition, using a new integrated variable (T_i − T_w)/ V˙_d found from the heat removal patterns, an empirical model of heat removal efficiency has been developed. The study found that the empirical model is a logarithmic curve η_R = aLn((T_i − T_w)/V˙_d)+b with a good data correlation coefficient from 0.93 to 0.97. Characteristic heat removal efficiency η_R^* was set up with this empirical model based on the relation of η_R^* = η_R|_{(Ti − Tw)/V˙d = 1.5}. The characteristic heat removal efficiency η_R^* presents the useful thermal energy in a storage tank and the testing method is characterized by fitting it for different types, volumes, charge modes, and discharge modes of storage tanks. It is a practical testing method for the heat removal efficiency testing of a vertical mantle storage tank. The testing method provides the manufacturers of the systems with the information that how many energy output rates of their commercial products can be more improved, and then they can be sure to supply consumers the high quality of products.