The working principle is that the heat pump evaporates refrigerant at low pressure to absorb heat from its surroundings and then condenses the refrigerant at high pressure on the other coil to release the heat absorbed earlier by a fan blows air across the coil.
Through this process, heat is pumped from surrounding to drying room. The moist in the material will be vaporized by hot air, the evaporated moisture will be removed by dehumidify system, thus the material will be dried and dehydrated.