ABSTRACT
Heat pumps employed for wood drying are heating-only devices that use two main types of heat exchangers: moist air-to-refrigerant evaporators for sensible and latent heat recovery; and refrigerant-to-air condensers for sensible heat delivery to the wood drying enclosure. Moist air-to-refrigerant evaporators are finned-tube heat exchangers where unmixed fluids (moist air and refrigerants) move roughly perpendicular to each other. Moisture condensers are compact, extended surface, direct expansion heat pump evaporators. They are provided with dense arrays of finned tubes in order to achieve very large heat transfer surface area per unit volume on the moist air-side. The major components of air-to-refrigerant evaporators are tubes and tube sheets, fins, and drain pans. Fins are used on the air-side to increase the heat transfer area because the thermal resistance associated with the airflow is too high compared with that of the refrigerant.
