Abstract: A novel thermal storage tank with a top flow stabilizer,a bottom stabilizer and two stabilizers on two sides are developed and investigated in this study.Two water fenders are set on the upper and the lower part of the tank respectively.The numerical model for the thermal storage tank is developed by the gambit.The thermal stratification in the tank is investigated by the fluent software when a heat pump system for space heating runs on the heating only mode and on the heating and heat charging mode,respectively.In comparison with a conventional thermal storage rank studied in a reference,the new tank can provide the uninterrupted space heating for 360 min and its outlet water temperatures are always higher than 313 K,while the conventional one provides space heating for 60 min under the same working conditions.The results also show that after running for 480 min,the average temperature difference between the upper part and the middle part of the novel tank is 6.8 K,while that between the middle part and the lower part is 4.6 K.