Densely lined with wedge-shaped hollow shaft hollow blades, heat medium through the hollow axial flow through blades. Unit effective volume of a very large area of heat transfer, heat medium temperature from -40 ℃to 320℃ , can be water vapor, may also be liquid-type: such as water, oil and so on. Indirect conduction heating, the air does not carry away the heat, the heat is used to heat materials. Only through the device body heat loss to the environment, heat insulation layer. Wedge-shaped blades with self-cleaning heat transfer surfaces. Wedge-shaped surface material particles and scrubbing effect relative movement, to wash away the wedge surface material attachments, so in operation have maintained a clean heat transfer surfaces. Blade dryer for the W-type shell, the shell of the general arrangements for 2-4 hollow stirring shaft. Shell with a sealed cover with the cover to prevent dust leakage and collection of materials, solvent vapor materials. Set out and exit pull a block, to ensure a high degree of material level, so that heat transfer surface is covered with fully materials. Heat medium through the rotary joint, passing through the shell jacket and the hollow stirring shaft, hollow shaft stirring according to the type of thermal media have different internal structures to ensure the best heat transfer.