The heat dryer belongs to a high temperature heat pump unt . is working princileis:the refigeranti compressed by the compressorto become igh temperature andhigh pressuregas,which enters thecondenser.condenses and loueties the heat whichi used to heat the ir in the drying room, so as to provide the temperature of thedrying room. in the form of hotair,the waterin the materialis aporized and evaporated,and thevaporated watervapor is discharged bythe dehumitification system toachieve the purpose of drying materials. The heatrecovery davice is adopted in the dtehumidification system. The recovered heatis used to heat thefresh air, which cansave 60%-70% of the energy consumption of the fresh air preheating, so as to achieve the purpose of further energy saving.