Process and system for drying products and materials, such as wood

Claim 1

A process for the drying of wood and other materials using a heat pump cycle including a compressor, an evaporator and a condenser, comprising: placing the material in a chamber; selectively withdrawing air from the chamber, from the outside, or from both the chamber and the outside, passing the air through the evaporator to remove heat from the air; selectively returning the air to the chamber or discharging the air to the outside, depending on the properties of the air after it has passed through the evaporator; passing the air to be returned to the chamber through the condenser prior to returning the air to the chamber; withdrawing additional air from the chamber; passing the additional air directly through the condenser; controlling the ratio of air passed through the evaporator to additional air passed directly through the condenser in response to the properties of the air passed through the evaporator after it has passed through the evaporator; and mixing the air withdrawn from the outside with the air withdrawn from the chamber, before the air from the chamber is passed through the evaporator.