The air velocity can be adjusted using two methods.
- A electronic frequency controller and baffling (normally used to optimize the air flow in an old kiln with insufficient fan capacity).
- Kiln-direct/Wooddryer system utilized an interval operated main fans.
The first method of using frequency drives for changing the electrical frequency going to the motors is slowly becoming more common. On some occasions the frequency drive is tied into the control system, which then can help adjust temperature, relative humidity and the air velocity.
The second method is often an overlooked method of controlling air velocity on average is the technique of operating the fans in intervals. This method has several lesser known advantages; such as more even drying and less costly than frequency drives. We at Wooddryer System offer controllers that incorporate these interval operated fan systems. Without getting complicated, we know that the air flow is more throughly distributed at higher air velocity; therefore, the load dries more evenly. We also know the reason for slowing the fan speed is the energy savings ( the claim is sometimes made that a fan operating at 50% only used 25% of the energy is not always true. This is especially not the case in a kiln where you have to deal with static pressure as well. The only credible study we have seen demonstrates a proportional relationship between rpm and ampere use). In most cases, we at Wooddryer System believe you will be better off using the interval system as opposed frequency controllers for the fans.
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