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 ...