Realize energy savings in cold store
The colder the climate, the more important it becomes to keep moisture under control, explains Kris van de Rijt, director of Air in Motion B.V. His company has developed solutions for managing the moisture load in cold stores and cold storages (freezers) for many years.
We often come across situations in which customers have been ‘fighting’ for years to dehumidify via the evaporators. When moisture from a warmer climate enters the cold store through door motions, the only way to remove this moisture is via the outlet of the evaporators. During this process the moisture must precipitate on the cooling block of the evaporators, and then be discharged via the defrosting process as liquid water with a temperature of > 0ºC.
Often and in particular with small and medium-sized refrigeration installations, the defrosting process takes place by means of electric heating coils, which must heat the entire cooling block of the evaporator to above freezing point. During this defrosting process a lot of heat is lost to the freezing environment, which results into a rising temperature. In addition, the efficiency of the evaporator deteriorates considerably in case of ice formation on the cooling block in the evaporator. This efficiency can be reduced to 70% of the normal capacity. After all, less air can pass through the evaporator and the heat can no longer be transferred as efficiently to the cooling block of the evaporator due to the ice. Because of this, the energy costs, for maintaining the temperature, will increase.
Dehumidifier "in front" of or "inside" the cold store
To answer this question, it's important to understand how an adsorption dehumidifier works, which you can read about here.
These unique properties of an adsorption dehumidifier allow it to dehumidify air very efficiently, even at low temperatures (5ºC and lower). However, this doesn't change the fact that the amount of energy required to remove 1 kg of water per hour from the air increases significantly as the temperature drops.
Various parameters play a role in determining the best (energy-efficient) solution: "repelling moisture from the freezer" or "drying inside the freezer."
Important factors:
- Opening time of the freezer door
- Dimensions of the freezer door
- Temperature and moisture load in the adjacent climate
- The type of product in the freezer
- Future vision of the organisation
Compare
If a 3x3 meter (WxH) passageway is opened for a total of one hour during a working day (8 hours) to a climate of 20ºC and 60% RH, the moisture load in the direction of the -18ºC cold store will be approximately 200 kg per day.
Option 1: Prevent moisture in the freezer room
With proper separation technology at the entrance to the freezer room, combined with a dehumidifier positioned in the climate zone in front of the cold store, a separation efficiency of over 90% will be achieved. For more information, see our website about AFIM® Air Doors. This limits the moisture load in the direction of the cold store to just 20 kg per day. After working hours, which are approximately 16 hours per day, the dehumidifier in front of the cold store can be automatically switched off to save energy.
Option 2: Removing moisture from the cold store
With a good basic separation technique at the entrance to the cold store, combined with a dehumidifier positioned inside the cold store, a separation efficiency of 50% based on moisture will be achieved. For more information, see our website about AFIM® Air Doors. This reduces the moisture load towards the cold store to 100 kg per day. The dehumidifier, installed in the cold store, will then remove the moisture along with the existing refrigeration system. Over 62 kg per 24 hours is removed by the dehumidifier, leaving only 38 kg per 24 hours to be removed by the refrigeration system. Over 80% of the moisture load can therefore be reduced by applying the right separation and dehumidification techniques.
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Summary
Purchasing the right dehumidifier requires thorough expertise. An incorrect choice has significant financial consequences for energy consumption for years to come.
Our solutions not only save energy but also prevent slippery work floors and dangerous situations in cold stores, says Van de Rijt. Air In Motion's solutions are now being successfully implemented in dozens of countries worldwide.
