Heat storage technique is important to solar thermal energy utilization. Furthermore

it a key technology that uses water as a thermal storage medium. To improve the performance of water storage tank

a novel equalizer was proposed in the study. Richardson number (Ri)

Mixed number (MIX)

and filling efficiency (ξ) analysis method were used to analyze thermal characteristics of the novel equalizer under an initial temperature of 70 ℃

an inlet temperature of 10 ℃

and different flow rates (corresponding to 1

2

3

4

5

and 6 L/min). The performance of water storage tank with the novl equalizer was compared with the water tanks with the direct inlet structure and three-layer orifice structure. The results indicate that with increases in the inlet flow rate

the ξ of the direct inlet structure and the three-layer orifice structure water tank are reduced while the ξ of the equalizer is initially enlarged and subsequently reduced. When the flow rate is 6 L/min

the Ri for the three modes is 6

4×104

and 4×106; the ξ corresponds to 0.534 93

0.584 93

and 0.814 05

respectively. The results demonstrate that the proposed equalizer reduces the mixing process and improve the thermal stratification in the heat storage water tank. In addition

the stratification performance of water tank can be effectively evaluated with filling efficiency because it contains the influences of both temperature and flow rate which are the key factors for thermal stratification in a water tank. Therefore

the filling efficiency can be used to analyze the stratified characteristics of water tank quantitatively and qualitatively.