Cold storage

Humidity problems

High humidity levels, especially during the summer, can cause problems with the production process, which leads to delays and can have financial impact.

In cold rooms the passage of air from one room to another is inevitable, as people and products move from one process to another: reception, racking, storage etc. This passage of outdoor air can produce ice and frost formation, and add to the following problems:

Slippery floors and water puddles.
High ice accumulation in evaporators and cooling systems.
High number of defrost cycles.
Low quality of products due to ice formation on surfaces.
Detection failures in photoelectric systems.
Wet or damp packaging.

FISAIR dehumidifiers prevent the formation of ice and defrost cycles are significantly reduced, ensuring smooth and high-speed operation throughout the year.

Our dehumidifiers remove moisture before it can accumulate as ice inside your equipment. Unlike conventional dehumidifiers, FISAIR units use advanced desiccant technology.

FISAIR offers a desiccant rotor drying system capable of removing moisture from the air at extremely low temperatures. The process involves the air in the chamber being passed through a silica rotor that absorbs water vapour from the air, even at temperatures down to -70°C and passes it to another section of the equipment, the reactivation circuit, which provides external energy, and removes the water vapour to be extracted externally.

For more information contact our experts.

Installation

Our equipment can be installed in anterooms with airlocks to maintain low moisture infiltration, as well as in the chambers themselves to dry any moisture infiltration.

Installing this equipment improves the air quality in the space, gives a significant reduction in energy consumption and a lower impact on the maintenance of the facilities.

The main precautions for freezer design are the quantification of moisture infiltration and the determination of the appropriate dew point to control.

If the installation is complete, the designer’s work is as simple as taking temperature readings from the walls, floors and conveyor supports where ice formation is to be minimized. The dew point to be controlled should be slightly below this surface temperature. In some cases, the temperature will be so low that it is not economically feasible to keep such a low dew point to prevent ice formation. It may be necessary to determine the temperature from which it is cost effective, and assume that there will be some ice formation, but much slower.

The lower the dew point, the more efficient the cooling system will be. The result being less frost on ceilings and conveyors. By removing moisture at source, before entering the refrigerated space, the system will have lower purchase and operating costs.

Advantages of dehumidification:

Fewer defrost cycles.
Improved product quality.
No process interruptions.
Improved job security.

Design Principles:

Remove moisture at source.
Remain below dew point to prevent ice formation.

Determine the loads

Moisture loads come from the infiltration of wet air, the opening of doors, gaps around conveyors, and evaporation from the product.

Product Humidity:

The water vapour from the product is relatively easy to quantify by weighing the product when it enters and leaves the freezer. The weight difference is almost all moisture. If the product is wrapped before freezing the load will be almost zero.

Infiltration air:

The air that enters the space from outside provides most of the moisture load. Air will enter when doors open and when doors close (through the pressure relief valves PRV) or it may enter continuously through the openings surrounding conveyor belts. In all these cases, it is important to minimize the load by using lobbies and entrance tunnels. In addition, opening/closing of the doors should be minimized.

Types of freezer

No antechamber:

Spiral or fast-freezing blast freezers are often built without a lobby. While lobbies are often impossible to add for space reasons, conveyor tunnels are essential to minimize ice formation inside the freezer. The figure explains the system graphically. Air is extracted from the factory environment (or from outside), processed through the dehumidifier, and driven into the conveyor tunnels. The flow rate should be sufficient to maintain a minimum speed of 0.5m/s through the belt openings.

With antechamber:

When space permits, the lobby system may be the best solution to minimize moisture in the freezer. It has the advantage of being low cost and easy to install. The figure explains the system graphically. The air is extracted from the lobby, processed by the dehumidifier, and returned to the lobby area, right in front of the freezer entrance. This ensures that all the air introduced into the freezer is dry air, with a lower humidity level than the temperature of the evaporators. The dehumidifier can be activated by a controller that monitors condensation in order to maintain air at a certain dew point.

Key considerations

In winter, the air has a much lower water vapour content, so defrost problems are significantly reduced. The ideal solution involves reducing humidity in summer to winter levels.

Air flow regulation:

Maintaining correct pressure is a key aspect of system design. To achieve the right system balance, air volume control dampers should be placed in the suggested locations. As in any air system, it is important to size the dampers so that the air can be adjusted without needing to open or close the dampers completely.

Insulation:

Ducts outside the main parts of the factory building, through which cold air circulates, should be insulated to avoid condensation.

Cost:

Both purchase and operating costs can be minimized by reducing the moisture load. Belt tunnels, lobbies and reduced door openings will reduce this load. The operating cost of the dehumidifier can also be minimized by installing a modulating control to monitor reactivation and determine the amount of energy needed to completely reactivate the desiccant material, while minimizing power consumption.

Conventional systems cannot efficiently remove moisture:

Process freezing systems are designed to remove sensible heat from the product quickly and efficiently. They achieve this cooling either through direct contact with the product as in a sheet hardner, or indirectly by cooling the air circulating around the product. However, they are not designed to remove latent heat from the air in the chamber efficiently.

While chiller evaporators can be easily defrosted, ice on belts and floors must be removed manually, causing production to slowdown or even stop. In addition, evaporator defrosting adds to the thermal load of the freezer and leaves the chiller evaporator out of service, which in turn, can prevent the system from maintaining low temperatures. This means that the cooling rates of the product can vary with the amount of ice on the evaporators, causing irregular production quality.

Some freezers’ need for a defrost cycle causes production to slow down or stop due to loss of capacity. This causes expensive and unnecessary delays.

To reduce frost, moisture in the air should be reduced. Cooling systems lack the cooling capacity to achieve low dew points when humidity is high. Evaporators freeze before low moisture is achieved. In addition, when evaporators expel moisture the air becomes saturated (it can no longer contain additional moisture) so it has no capacity to absorb moisture loads from either the product or outside infiltration.

Food

There are countless companies within the food industry, each with its own specific requirements and challenges, however, many deal with condensation on the surface of cold products. This spoils product quality and encourages bacteria. Some products are hygroscopic and require particularly low levels of moisture to prevent them from spoiling.

Traditional outdoor ventilation only introduces more moisture into the building and heating has no effect on the dew point of the air.

The only effective way to treat unwanted moisture is to use dehumidification to reduce moisture levels in the air or the dew point at which moisture condenses.

Adsorption dehumidifiers are the most effective and economical solution, making it possible to guarantee low humidity and temperatures, while making the most of the available thermal energy.

Refrigerated spaces

Refrigerated areas, such as slaughterhouses, dairy farms, cheese manufacturing centers, etc., often encounter problems with moisture in the air, which condenses and drips over food. This is totally unacceptable for many reasons.

The problem starts with the incoming air, which has a higher dew point than the cold zone temperature. This causes the moisture in the air to condense on products, floors, ceilings, and other surfaces.

The solution is to ensure the dew point of the air is below the temperature of the refrigerated area. The most energy-efficient way to do this is by dehumidification.

Return on investment in a short space of time

Similar problems arise in cold storage areas and freezing tunnels, where any condensed moisture on cold surfaces will freeze.

In cold storage facilities, this results in ice formation on floors, ceilings, and walls, which is a danger to workers. Freezer elements also become frozen and time and energy is wasted during the thawing process. Dehumidification equipment can help prevent these problems, as well as provide savings of up to 10% on overall energy consumption.

In freezing tunnels ice formation can cause major production problems. Moisture in the air condenses on interior surfaces, conveyor belts, screws, and accessories. This freezes and ice accumulates until it prevents movement of the conveyor belt. The system then has to be thawed, cleaned, and cooled again, resulting in a substantial and costly disruption to production, as well as considerable energy consumption.

Dehumidification systems increase efficiency in freezing tunnels by 50%, as well as reducing energy costs, which means expenditure is recovered in a few months.

Contact your nearest office.