Systems for drying moisture-containing work pieces and methods for drying same

A dry kiln system for controllably drying moisture-containing work pieces, which comprises:

• a drying compartment defining an internal workspace for housing and drying said moisture-containing work pieces by introducing heat into said internal workspace and heating the moisture-containing work pieces located in said internal workspace by removing heated moisture from the work pieces and absorbing said heated moisture into the air in the workspace to produce heated humidified air;
• a multi-directional air flow heat exchanger for receiving heated humidified air and atmospheric air and for recycling waste heat from exhaust air from the drying compartment, and for heating the atmospheric air in the heat exchanger using recovered heat extracted from the heated humidified air to a temperature higher than ambient temperature thereby reducing energy costs and drying time and preventing the loss of circulation air;
• and
• first and second reversible variable speed fans, each of said fans being independently controllable at respective intake and exhaust modes and at variable air flow rates, without employing a damper for controlling the flow of exhaust air and atmospheric air to and from said heat exchanger;
• and
• a humidity control system including sensors for monitoring the conditions in the workspace, including air temperature before and/or after the heat exchanger. and sending a control signal;
• variable frequency drives interfaced with said humidity control system to set the speed of the first and second reversible variable speed fans which proportionately increase or decrease the speed of the first and second reversible variable speed fans to increase or decrease the air flow through the dry kiln in response to the control signal sent by said control system,
• said first variable speed and/or said second variable speed fan controlled by said humidity control system and (a) controllably exhausting said heated humidified air from the drying compartment into said heat exchanger, (b) introducing atmospheric air at ambient temperature into said heat exchanger, (c) controllably exhausting said heated humidified air from said heat exchanger after heating the atmospheric air, (d) replacing the humidified air transferred from the drying compartment with the heated atmospheric air, and (e) controllably correcting pressure imbalance in the workspace by running the fan at intake mode, and the fan at exhaust mode, at different respective speeds, the drying operation being conducted at any level from 0 to 100% of required output to sustain the dry kiln operation at a predetermined output level for maintaining a steady state operating conditions.

A method for controlling drying conditions in a kiln for drying wood by venting and recycling waste heat from exhaust air from the workspace defined by said kiln, which comprises

• providing a kiln including said workspace for housing and drying wood;
• introducing wood into said workspace;
• introducing heat into said workspace for drying said wood;
• heating the wood located in said workspace;
• removing heated moisture from the wood and absorbing said heated moisture into the air in the workspace to produce heated humidified air thereby forming wood which is substantially uniformly dried;
• providing a multi-directional air flow heat exchanger for receiving heated humidified air and atmospheric air;
• providing first and second reversible variable speed fans, each of said fans being independently controllable at either one of an intake and exhaust mode and at variable air flow rates, the first and second reversible variable speed fans being run at different speeds which preserves a balanced pressure inside the workspace, without employing a damper for controlling the flow of exhaust air and atmospheric air to and from said heat exchanger;
• providing a humidity control system including sensors for monitoring the conditions in the workspace, including air temperature before and/or after the heat exchanger, and sending a control signal;
• providing variable frequency drives interfaced with said humidity control system to set the speed of the first and second reversible variable speed fans which proportionately increase or decrease the speed of the first and second reversible variable speed fans to increase or decrease the air flow through the dry kiln in response to the control signal sent by said control system;
• controllably exhausting said heated humidified air from the workspace into said heat exchanger using said first variable speed and/or said second variable speed fan;
• supplying atmospheric air at ambient temperature into said heat exchanger using said first variable speed and/or said second variable speed fan;
• heating the atmospheric air in the heat exchanger to a temperature higher than ambient temperature using recovered heat extracted from the heated humidified air thereby reducing energy costs and drying time and preventing the loss of circulation air;
• controllably exhausting said heated humidified air, after heating the atmospheric air, from said heat exchanger using said first variable speed and/or said second variable speed fan;
• controllably correcting pressure imbalance in the workspace by running the fan at intake mode, and the fan at exhaust mode, at different respective speeds;
• and
• replacing the humidified air transferred from the workspace with the heated atmospheric air using said first variable speed and/or said second variable speed fan, the dry kiln operation being conducted at any level from 0 to 100% of required output to sustain the dry kiln operation at a predetermined output level for maintaining steady state operating conditions.