Humidification & Water Systems

The System

Fresh drinking water is first filtered and de-mineralised before being piped into the Fogging unit. The Fog generator (or Fogger) has a small water container with a submerged metallic disc or Transducer, that is vibrated to a very high frequency, creating ultra-sound waves. This causes the water molecules to vibrate and turn into fog or a cold steam consisting of 3-5 micron droplets of water suspended in air. This process is called 'Nebulisation'.

Each Transducer can convert between 0.2 and 0.6 litres of water per hour into fog. Refrigerated or ambient air is first filtered and cleaned, then passed through the Fogger, to blow the Fog into the Fog Distribution System. As the fog travels into the display area it is super-cooled by refrigerated air. The fog circulates within the cabinet and its refrigeration system, being constantly replaced by more fog as the refrigeration dehumidifies the air and humidity dissipates into the atmosphere around the cabinet. Fogging provides a permanent, transparent blanket of fog to protect the product from dehydration.

The water droplets contained in the fog are too small to freeze. Droplet evaporation is retarded by super-cooling the water droplets. At this low temperature the droplets stay in suspension for 30 to 60 second, allowing plenty of time for them to travel through the refrigeration system.

The Water

Most Fogging units require a de-mineralised water supply. In addition, an Ultra Violet or Ozone De-germification unit cleans the system from the water and air inlets, right up to each fog outlet in the food area of the display case. The nebulising area and fog distribution ducts are flushed and cleaned periodically by the automatic system, to ensure that a high level of hygiene is maintained.

The Effect

This system is used in open, refrigerated Fresh food display cases. It cannot operate as a humidistat controlled humidifier due to the open environment. In order to maintain a constant atmosphere within the cabinet it is necessary to continuously circulate the fog. As the fog passes through the food display counter, it bathes the product on display, depositing, by condensation, a microscopic sacrificial layer of moisture onto the product surface. As fog is refrigerated at around freezing this has the effect, through evaporative cooling, of further reducing the surface temperature of the food product.

A consequence of the evaporation process is a boost in the relative humidity of the atmosphere around the product. Subsequently, dehydration, caused by the movement of dry air, is greatly reduced. Product weight loss is reduced by over 50% and product condition is maintained for hours longer to help match the product's stated shelf life.

The Benefits

• Ultrasonic Fogging is the driest form of Fresh Food Moisture Maintenance. For this reason it can be used on almost all Fresh food including Fresh Meat, Cheese, Soft Fruit, Vegetables and Salads without wetting.
• Food product display life is increased from 3-5 hours to 36-48 hours, increasing sales value, as there is less need to reduce prices to sell. With many products there is no obvious deviation in colour until 60 hours.
• Sales are increased by the ability to make bold displays all day with brighter, fresher products on display.
• Wastage is reduced, as there is less need to 'face' cut surfaces to remove dried and discoloured areas.
• Wastage is reduced since approximately 60% less weight is lost through dehydration.
• Labour cost is reduced as the product can be left in the display cabinet overnight.
• At night this system can also operate as a humidistat controlled Humidification system, with a pre-set relative humidity. The back of the display counter must be enclosed with night blinds or sliding doors and products can remain in the cabinet. Alternatively you can de-merchandise and clean the counter each night and re-set it up each morning.
• Once fogging is installed, it is easy to see the cold airflow, and if refrigeration fans break down in part or all of the display area fog will collect and draw attention to the refrigeration default.
  

Maintenance

Once optimum settings have been achieved it should not be necessary to re-adjust the system. The operation of UV lamps, ozone generators etc. used in the bacteria management system, should be checked on a regular basis and a scheduled maintenance routine established for a service visit every three or six months.