Dave Marshall-George, Sales Director, Condair Limited

Author: Dave Marshall-George, Sales Director, Condair Limited


Preventing ice & mist with dehumidifiers

Dave Marshall-George, Sales Director at Condair, explains how dehumidifiers can be used in cold stores and freezers to prevent ice and misting.

Commercial cold stores and freezers are tightly sealed environments, but excess water will always find a way to get in. Cleaning routines, evaporation from produce and people, or simply carried in by the air through open doorways, moisture ingress is inevitable. It can lead to ice on floors, walls and ceilings, frost damage to produce and mechanisms, or air misting and reduced visibility. All of these things will impact an operation’s productivity, profitability, and health and safety. But it doesn’t need to be this way…

Dehumidifiers specially designed for use in this environment will extract humid air from the freezer, remove the excess moisture and return dry air back to the storage environment. This dry air delivery is normally directed to where a problem is being experienced, for instance above an entrance if the issue is doorway icing. Alternatively, it can be in an ante-room or airlock area just outside the entrance, to minimise the volume of moisture initially entering the freezer.

Beyond improving the internal environment of a cold store, removing moisture with a dehumidifier will also reduce the amount of ice build-up on the refrigeration system’s evaporators. By lowering the ambient humidity level, the need to defrost can be significantly reduced and the operating efficiency of the system improved. In some blast freezer projects, we’ve seen the need to defrost be extended from once per week, to once every three months. Additionally, as the dehumidifiers were blowing directly on to the evaporators, leaving them running during the defrost cycle reduced the defrost time from a whole day to just a few hours.

Removing moisture from a cold environment requires desiccant dehumidifier technology, such as the Condair DA. This is a type of dehumidifier that passes wet air through a slowly rotating desiccant rotor. It literally absorbs water from the air like a sponge. As this rotor revolves, a section of it continually passes through a hot air flow, which removes the water and allows the rotor to remain absorbent. This is called “regeneration”.

This type of dehumidifier therefore needs two ducted airflows to operate. A process airflow, which takes air either from the cold store or ante-room area, passes it through the dehumidifier’s drying rotor, then re-introduces the now dry air back to the cold store environment. The other airflow is the regeneration airflow. This draws in fresh ambient air, heats it, then passes the hot air through the rotor to regenerate it, before finally being exhausted externally, along with the moisture it collected from the rotor.

Removing moisture from a cold environment requires desiccant dehumidifier technology, such as the Condair DA.

Removing moisture from a cold environment requires desiccant dehumidifier technology, such as the Condair DA.


This type of dehumidifier isn’t unique to cold store projects, as it’s used in many close control, low humidity or low temperature drying applications. But there are some features that are specifically needed for successfully drying a cold store or freezer. These can include exceptionally thick insulation, a thicker than normal rotor, different rotor speeds, special heaters, and pressure configurations that avoid the potential for air leakage and undesirable thermal transfer that will lead to internal freezing or condensation.

Over many cold store and freezer projects, Condair’s freezer dehumidification systems have been tailored to include a very flexible range of options to suit any cold store requirement. Models are available that can be located outside the cold store, in an ante-room or airlock area, inside the cold store or even outside the building. Each strategy has pros and cons, but a particularly useful feature is the energy savings that are possible only when placing the dehumidifier outside the cold store.

As these systems are operating 24/7, minimising energy consumption is vital. The majority of the energy used by a desiccant dehumidifier is for heating the regeneration airflow. In cold store applications, it’s possible to use the fridge system’s condenser coil to heat this airflow. Using this energy source alone can be sufficient to get the air to 65-70°C and obtain enough drying capacity to achieve a project’s humidity control objectives. This strategy is not possible when installing the dehumidifier inside the cold store.

Ice formation before and after the installation of a dehumidifier.

Ice formation before and after the installation of a dehumidifier.


Another energy saving feature involves using a heat recovery system on the exhaust side of the regeneration airflow. Before the hot wet air is vented, running it through a heat recovery unit can transfer around 75% of the energy back to pre-heat the incoming regen airflow. Incorporating both these strategies can see a dehum’s energy consumption reduced significantly and could result in a net reduction in overall energy use, when considering the improved efficiency and energy savings on the chiller plant.

Alongside the energy saving benefits that are possible by locating the dehumidifier outside of the cold storage area, there are other advantages. Servicing is much simpler, as engineers can operate in ambient conditions. The dehumidifier can be turned off without any risk of internal moisture freezing, causing issues with moving parts. Also, due to the low temperatures, PLC controllers aren’t an option for units inside the freezer, limiting the functionality of the system. And lastly, dehumidifiers are large and if located inside a cold store, will take up a lot of valuable storage space.

But whatever location or energy saving options are selected for a project, being able to proactively reduce the humidity of the air inside a freezer environment has obvious benefits for commercial operators and can produce rapid return on investment.

Get advice from Dave on reducing ice in freezers with dehumidifiers


Get advice from Dave on reducing ice in freezers with dehumidifiers

Bunkermuseum Hanstholm

Erik Ansø

Museumsforvalter

“The noise level is now so low that you can talk normally in the ventilation room even though both the ventilation and a dehumidifier are running, which was one of the criteria. You certainly couldn't do that before, and it's worked out well in a concrete bunker.”

Prime Ocean

Jan Bork Nordmann

Produktion

“The dehumidification solution from Condair is one of the best investments we have made down here.

Prime Ocean is one of Europe’s largest importers of fresh cod from FAO27 and also imports large volumes of salmon. Both fresh fish products and high-quality frozen products are produced. The dehumidification solution has helped eliminate condensation problems, the daily downtime of the machines has been virtually eliminated and the maintenance work on both machines and buildings has been significantly minimized.”

Vyra Suites Hotel in Qatar

Kiran Nair

Sales Engineer at Mentor Trading

“The ceiling mounted dehumidifiers are compact in size and were fixed above the pool and spa areas. We were very satisfied with Condair’s service and their prompt response to the project.

The quality of the Condair DP-C dehumidifiers is of a high standard and they were easy to install and simple for the customer to operate. We look forward to a working with the Condair team in the future.”

T Clarke

Doug Lumb

Project Engineer

“The Condair DC 50W dehumidifier was actually chosen by our designers, as it fitted the bill perfectly for the environment. The unit size was based on the quantities of kit hung in the room to dry when the firefighters return to the Centre at the end of their training exercises.

It’s a reliable product and currently operating at the station just as expected, plus installation was really simple and didn’t take long at all, so all very good.

I would definitely specify Condair dehumidifiers for future projects.”

The Savanna

Lisa Gardshol

Founder and CEO

“We have been very happy with the performance of the Condair dehumidifiers JTR installed to comply with our drying approach. It has not only allowed us to increase production efficiency but also produce our award-winning biltong.

We have full control over the entire process and can make decisions based on the data that we recieve. This is something which we couldn’t do as well before.”

John Todd Refrigeration (JTR)

Matt Gough

Refrigeration Engineer

“The rooms need very tight environmental control but the previous strategy introduced outside air to help lower temperatures when needed. JTR redesigned the drying rooms and installed Condair DC-N dehumidifiers.

The dehumidifiers, located in the rooms, both dry and heat the air to the required condition, resulting in a fully sealed area and a consistently controlled drying process.”

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