If the friction coefficient of the materials against the inner wall of the Belt conveyor is small, the resultant force will be smaller and the height that the materials are thrown will be higher. It will be more difficult for the materials to slide along inner wall of the cylinder and the running routes will be more long. That is to say, under the effect of centrifugal force, the distance of movement of the particles in the belt conveyor will increase as the coefficient of friction of in the inner wall decreases. The purpose of the screw conveyor is to make the material do the axial movement. If the degree of the tangential motion is larger, the extra power consumed by the screw conveyor will be greater, the transport efficiency of the belt conveyor will be reduced. In order to obtain a higher efficiency of the belt conveyor, the barrel wall should have a certain degree of roughness, the friction coefficient should be suitably large preferably.
However, simply to increase the roughness of the inner wall of belt conveyor, in particular, to increase the roughness of the cylinder bottom, will also increase the resistance to the axial movement of the material in the belt conveyor and increase the extra transport power, wich is not conducive for the material conveying. Therefore, to reduce the resistance to axial movement of material, they should reduce the coefficient of friction of the bottom of the barrel so that the bottom can be smooth as far as possible and increase the coefficient of friction of the side wall of the cylinder to suppress the effect of centrifugal force.

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