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Humidity Control for Walk-In Coolers

How does the Sorbite Humidity Control System work in your cooler?

1) Humidity in Refrigerated Systems
2) Controlling Humidity with Sorbite™
3) How this affects the cooler's contents
4) How this affects the cooler's temperature

Humidity in Refrigerated Systems

In order to reduce air temperature, the air is circulated and drawn across the fins and coils of the heat exchange unit (sometimes called the "Evaporator"). As the air passes over the fins, the refrigerant in the coils absorbs the heat from the air reducing the air's temperature. The relative humidity in the cooled air rapidly rises to the point of saturation and the water vapor condenses (and normally drained away). The air then exits the heat exchanger and mixes with the rest of the air in the cooler. So what is seen is that the natural process of refrigeration is continually reducing humidity and eventually the air becomes dry. For small coolers, when the door is opened, a large percentage of the air is replaced with air that is warm and humid. As the new air enters the chamber, the relative humidity of the mixed air rapidly rises to 100% and is now saturated. The moisture quickly condenses on any cold surfaces inside the cooler. The act of condensation releases large amounts of heat energy that must then be removed in order to maintain the desired temperature. In large coolers, only a small fraction of the air is exchanged when the door is opened. The air near the door does become saturated and surfaces near the door become wet, but the air inside is always dry. In summary, the air in small coolers suffers from large swings in relative humidity, while the air in large coolers is always dry. In either case, any condensed moister tends to stay that way, as it takes considerable energy for the evaporation process and there is no source for this energy.

Controlling Humidity with Sorbite™

What happens in a refrigerated chamber with the Sorbite™ system installed? When the door is open and the hot, humid air enters, the mineral rapidly absorbs the moisture preventing the air from reaching 100% relative humidity. Since the air is not saturated, condensation is a greatly reduced and liquid water is not absorbed in porous objects (like cardboard boxes and paper labels) nor does it collect on the cold objects. When the door is closed, the natural process of refrigeration reduces the humidity, but the Sorbite™ releases moisture maintaining the relative humidity near 80%.

How this affects the cooler's contents

Condensation that collects on the surfaces of the raw food and in the cardboard boxes provides an excellent environment for the growth of bacteria and mold. This attack literally eats away at the food stuff and leaves toxins that aggravate the process as well as creating a health risk to your patrons.

While most food service professionals believe condensation is the primary cause of deterioration, in actuality, it is when the air is too dry that most of the damage occurs. As moisture is pulled from foods the cell membranes are ruptured. It is this process which causes exposed animal products to change color and dry out, and plant products to loose their crispness and flavor.

There are several physical laws which govern the state of gases and liquids in an enclosed system. Primarily we are dealing with equilibrium and partial pressures. In simple terms, when the air is too dry, water contained in other mediums or states is trying to increase the humidity of the air. So why isn't the accumulated condensate evaporated to re-humidify the air? The answer is that water has a very high Specific Heat. Specific Heat is the amount of energy released or absorbed when a change of state (e.g. from liquid to vapor) occurs. The bottom line is that it takes less energy to pull the moisture from the food than to evaporate the condensate and so the damage occurs.

The only way to combat these destructive processes is to regulate the humidity level which is precisely what Humecon Humidity Control System does.

How this affects the cooler's temperature

As explained in the previous section, water has a very high Specific Heat. When the hot humid air enters the cooler, the moisture condenses; a tremendous amount of energy is released into the air. This causes the air temperature to rise until the air is no longer saturated. As the temperature rises, the compressor kicks in and the cooling process begins. This viscous cycle repeats every time the cooler door is opened and large swings in temperature and humidity ensue.

The Humecon Humidity Control System to the rescue again. By absorbing the humidity as it enters the cooler, the amount of moisture condensing is reduced and less energy is released into the air. The temperature is stabilized and the compressor does not cycle as often reducing the electrical energy required to maintain temperature.