A corner assembly for a tube conveyor system comprises a housing defining a wheel receiving area and a flow path with ports at opposite ends of the flow path. A wheel rotatably received in the wheel receiving area comprises a rim having an upper surface and a lower surface; a pair of spaced apart channels formed in at least one of the upper and lower surfaces of the rim; and at least one flapper pivotally mounted to the wheel inside of the rim. The flapper is freely movable between a position in which it is aligned with a wall of one of the channels and a position in which it is aligned with a wall of the other of the channels. Thus, when the wheel rotates, the flapper will sweep any material in the wheel receiving area towards and through one of the channels and into the flow path.