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If your facility is in a cold environment such as Winnipeg, MB, Canada, the incoming air can easily be 0Â°F and 50% relative humidity during a typical winter day. If this entering cold air is warmed up to 40Â°, the humidity will now fall to less than 20% because warm air is able to hold more moisture. This lower humidity level poses little problem to the proper operation of the facility.
However, if your facility is in Los Angeles, CA, the incoming air could easily be 65Â° with a relative humidity of 65%. If this entering warm air is reduced to 50Â° inside the skating rink, the humidity will skyrocket to 100% rh because the cold air will not hold as much moisture. At this point, there is only one thing the water vapor can do: It condenses into water droplets and the problems begin.
Just as a boiling kettle deposits moisture on a cold window on a winter day, airborne moisture in an ice rink deposits on cold surfaces; of course, the coldest spot is very likely the ice surface itself. When this happens, the ice will cloud over, losing its desired sheen, and will become rather slushy to skate on. The glass around the ice surface will also fog over, obstructing the view of the audience.
In addition to the aesthetic inconveniences caused by excessive humidity, the condensing moisture releases a tremendous amount of heat onto the ice surface that must be removed at the expense of operating the refrigeration equipment longer than would normally be required. Condensation can permeate building insulation, drastically reducing its effectiveness; and, of greater consequence, structural steel will start to rust and wood will start to rot, further reducing the integrity of the facility.
Fortunately, with proper design, humidity can be controlled effectively and efficiently. The two commonly used styles of dehumidification systems are the mechanical dehumidifier and the desiccant dehumidifier.
In recent years, desiccant dehumidifiers (Figure 1) have been gaining favor in ice skating facilities.
A desiccant dehumidifier is comprised of an air handler with a fan section, a slowly rotating desiccant wheel, and a gas-fired burner section. The fan section draws fresh air into the building as well as recirculating and distributing air within the ice rink.
Studies in recent years cite serious problems associated with indoor air quality within ice skating facilities. The desiccant dehumidifier has the added benefit of replenishing fresh air as well as dehumidifying it at its source, before it has a chance to condense on cold surfaces.
The desiccant wheel is comprised of a honeycomb structure impregnated with silica gel. The moisture-laden air is passed though the slowly rotating desiccant wheel, allowing the moisture to be absorbed. The humidity content in the air coming off the wheel is negligible.
As humidity is absorbed from the air passing through the slowly rotating desiccant wheel, a portion of the wheel enters the burner section, where the moisture is driven off (similar to what takes place in a clothes dryer). The regenerated silica gel is now capable of absorbing more moisture as it rotates back into the fan section.
Although the effectiveness of the system is increased by a properly designed distribution system, ductwork is not required throughout the entire facility. The extremely dry air leaving the desiccant system creates a “dry hole” that literally draws moisture from all corners of the building.
It is advisable to introduce a small amount of dry air above a low-e ceiling, to head off any future moisture problems which notoriously plague these installations.
Art Sutherland, of Accent Refrigeration, Victoria, BC, Canada, has been in refrigeration for more than 25 years. Accent Refrigeration specializes in the design and installation of refrigeration systems for ice skating rinks.
Publication date: 09/04/2000