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FAQ

Has there been any independent comparison between Alentpumpen and reduction of fan speed?

There have been comparisons but not official reported.
Many of our customers have done comparisons before they ordered Alentpumpen. Others have taken note of fellow test and subsequently invested in Alentpumpen. In this way, word of mouth, we now have 300 installations.


Do you have to add more heat when you stop the fan motors?

No, you do not need to that when drying with the Alentpump, despite the fans are stopped half of the drying time. This is how it works;
The water from the wood has to vaporize from the wood surface and the evaporation energy, we will not escape. A normal drying rate in a chamber dryer, 120 m3 of pine, 38x110 mm, 75-12% M.C. at -5 ° C outside temperature, draws more than 35 MWh of thermal energy. The evaporation part is almost 22 MWh. Warming pulls over 6 MWh and heating of fresh air just over 5 MWh. The remaining heat requirement is largely dependent on the building. Heat conduction through the door, walls, ceilings and floors may be 1-2 MWh. Large leaks and poor insulation require additional spraying that consume several MWh. The conditioning draws energy for evaporating of spraying water.
Alentpumpen has several advantages that reduce heat consumption:
+ Leakage is reduced when the fans are stopped
+ Heat loss through the walls, ceilings and especially port is substantially lower when the air is stationary
+ additional spraying is not needed with Alentpumpen

The fan motors adds no heat when they are stopped but you do not need to fully compensate for this. If you are drying to low wood moister content in an old kiln, you are saving heat with Alentpumpen.



Do you have to compensate for fan stop with higher timber temp or higher psychrometer?

No, the Alent Pump is based on alternating and rapid venting and rest. The timber average temperature is rather lower when pumping. Psy is higher during the short active phase of the pumping but the long rest periods reduces cracking.


Does the fan motors need more service?

No,
Experiences show that the motors lifecycles extends , rather than shortens.
We do not have any statistics on the fan motor life when you run Alentpumpen. All indications are that life expectancy is increasing!
The fan motor is stopped in intervals of 10-60 minutes. There will be no extra stops for reversal. During these stops the internal motor temperature is decreased and it leads to a longer life. There is no risk of condensation on the engine even during long pump stop. To get condensation the motor temperature has to drop below the dew point temperature in the chamber and it is an impossibility, unless the engine is equipped with active cooling.


Higher drying temperature?

Since the fan motors are given time to cool down during 10-60 minutes when reversing, you can keep a higher dry temperature during drying without any harm to the motors. The setpoint in the dry temperature can be slightly higher than the corresponding temperature for conventional drying because the average temperature in the timber during a pump stroke is a few degrees below the setpoint.


Do you need to prolong the drying time when you stop the fans 50% of the drying time?

No, the theory indicates and practice shows that the drying time is shortened.
When drying to low moister content you can save days!


Does drives save as much electrical energy as Alentpumpen?

No, far from it!
Drives are normally running at 30-50 Hz when drying to lower moisture contents. That compares to the Alent Pump which stops the fans 50% of the drying time. In addition, drying time is shorter with the Alent Pump. When reducing the fan speed by drives you have to prolong the drying.


How does it works, the Alent Pump?

The timber is subjected to brief, harmless stress periods and in between longer periods of rest or stress relief. Almost as repeated conditioning sessions. The drying process is enhanced by "pumping" that maintains a high moisture migration inside the timber without building up dangerous tensions. Water evaporates from the wood surface even during fan stop, but then taken heat from the wood rather than from the air. Wood surface is cooler than the interior of the timber, and this helps to increase moisture migration towards the surface. It is the vapor pressure that drives moisture migration. During the stop there is an adding force to the moisture migration due to the temperature gradient in the wood and drying is faster.

Higher moister in the middle of the board ?

This is not a generall understanding among those who uses the Alentpump. Measurments shows a lower gradient, except in one test case - perhaps it is this which have caused the question, or roumor.


How much does it cost to install Alentpumpen?

The pay off time for installing the Alent Control system with Alentpumpen is normally two years.


How can Alentpumpen save heat?

During the rest periods the heat valve is closed and the air in the dryer is stationary. Leakage from the dryer decreases. Convection, ie heat conduction through walls and ceilings, decreases due to stagnant air layer next to walls and ceilings. Alentpumpen does not need spraying and it can save large amounts of heat, especially in older dryers with leakage. With conventional drying schedules spraying can easily consume several MWh heat.