Control range of adiabatic humidifiers

When selecting a humidifier, it’s important to make sure that it can achieve the maximum duty required. This is well understood, but an area that’s sometimes overlooked is the minimum capacity of the humidifier and the effect it can have on maintaining the desired humidity level in a theatre, office or manufacturing space.

This problem does not exist with the Gibbons humidification system, as we can turn the humidifier output down to virtually zero when required. Some alternative adiabatic humidifiers have a limit when it comes to lower levels of humidification they can achieve, often having a turndown ratio of only around 4:1. This means that a humidifier with a maximum capacity of 200 kg/h can only achieve a minimum of 50 kg/h as shown on the graph below.

Where the humidification load is moderate, such as during spring and autumn, there will be many times where the humidity demand is below the minimum that alternative humidifiers can achieve. In the example above, any demand level below 50 kg/h cannot be achieved.

Now suppose that the air volume were to be reduced to, say, half the maximum on which the humidifier capacity was calculated. This might be as a result of how the air system operates or it might be a permanent energy-saving measure now or in the future. It follows that halving the air volume would halve the demand on the humidifier, so instead of having a maximum load of 200 kg/h, the maximum would be 100 kg/h.

The minimum capacity of the alternative humidifier remains the same, so now the possible turndown of the humidifier is reduced to only 2:1, which severely limits the potential humidity control. The performance of the Gibbons humidifier would not be affected by the reduction in air volume because we can reduce output to virtually zero. For example, we have installed our system in a concert hall where the air volume is reduced to 10% of its maximum before a performance, and our humidifiers are still able to maintain the correct humidity level.

Below is a graph showing the maximum and minimum humidification requirement per month for a typical London building running 24/7. It can be seen that there are many occasions where the minimum conditions are below 50 kg/h, which mostly occur during daytime. In these conditions, it will not be possible to maintain the correct humidity levels in the space.

If the airflow were to be halved, it can be seen that there are many more conditions where the humidifier would not be able to maintain the desired level.

So, remember to check the minimum output from the humidifier you’re considering. If in doubt, choose Gibbons!

To find out about the many other benefits of Gibbons’ adiabatic humidification system, call Steve Rix on 07966 423165 or email steve.rix@gibbonsgroup.co.uk.