The flow around the high speed rotating pirn and energy loss are measured experimentally . A technique to decrease the energy loss is considered. The results obtained are as follows : 1) It is shown quantitatively that the air around the rotating pirn is sucked from the upper and lower parts and is blown from the middle part. 2) When the cover, of which the cross sectional shape is triangle, is set aroundthe rotating pirn , the energy loss is improved about 20 percent.