Aim\ To find out the factors which affect the circulating flux in an agitated tank with draft tube

and optimize the type of impeller. Methods\ The effects of impeller types

the Renolds number of impeller

diameter of draft tube

clearance between draft tube and the bottom of tank

liquid height

the tube numbers and the circulation area on the circulation flux were systematically investigated by thermo tracing system in a flat bottomed cylindrical vessel of 0.5 m and 0.8 m in diameter

equipped with a draft tube and modeling heat exchange tubes. Results and Conclusion\ A new type impeller which can improve the circulation flux in agitating tank is exploited. The effects of the different structure parameters on the circulation number are shown.