How to prevent the build-up of ice in freezers

How it works

In cold storage, the temperatures are usually between +3 to +5°C, and in a freezer this drops to around -25°C.

The key point within a freezer or cold store is to achieve a dew point temperature within the room air, lower than those of the surfaces within the store, and foremost to be lower than the dew point of the evaporator.

By doing so, the build-up of ice in freezers can be significantly reduced or eliminated. This makes the evaporator work more efficiently, i.e. consume less power, and there will be little to no need for de-icing, which is often a costly and time consuming process.

There are three main ways to install a dehumidifier in a freezer or cold storage facility. This will depend on the existing construction as to what is the preferable approach.

  1. The dehumidifier can be installed inside the freeze room. This will take up some room inside the freezer, and also require the reactivation air ducts (connected to the external air) to be heavily insulated outside of the freezer, to prevent ice forming inside. Ease of maintenance should also be considered, as this may be difficult when the internal temperature is -25°C.
  2. You can install the dehumidifier outside of the freezer and lead the process air ducts into the room. This has the advantage of not taking up any space within the freezer itself, but the ducting outside of the space will again need to be heavily insulated to prevent ice build-up on the external surfaces of the pipe. The dehumidifier itself comes with a 100mm thick insulated case to avoid icing. This arrangement also has the benefit that any access or maintenance to the machine is not hindered by the freezer temperatures.

3. The third way is to dehumidify the air lock(s), rather than the freezer directly.

In this application the unit can be mounted within the air lock or external to it, with little changes in the installation, as there is no longer a large temperature differential between the two air streams, and the main factor being availability of space for the unit.

The most common way is to install the unit inside the airlock, like in the inside version of the freeze room, but you can also install it as an outside version and let the dry air into the airlock, like in the outside version. The advantage of dehumidifying the air in the air lock is that you reduce the most important factor concerning the moisture load, the infiltration during door openings. This is perhaps the most favourable way to dehumidify a freeze storage.

More information

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Dantherm Group UK

Marcus Bailey

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Alessandro Bisinella

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