A frozen dinner manufacturer had a problem with frost collecting on the dinners during the final dressing of the plates. The company turned to Nyle Corp., Brewer, Maine, a manufacturer of dehumidification drying systems. Nyle supplied a dehumidifier for the freezer room that brought in fresh air and dehumidified it so that the freezer room was under a slight positive pressure. The dewpoint of the air entering was low enough to absorb the moisture generated by the bodies of the workers in the room. Outside air was introduced and cooled by refrigeration to 36°F (2.2°C) to remove most of the water in the incoming fresh air. The air then passed over a desiccant wheel, and the dewpoint was reduced to -10°F (-23.3°C).
Because of the heating effect of the desiccant process, the air was approximately 65°F (18.3°C) after desiccant drying. Additional cooling therefore was required to allow the air to be introduced to the work room at 20°F (-6.7°C) but dried to a -10°F dewpoint. By using the refrigeration system first and cooling the air to 36°F, the amount of water left for the desiccant wheel to absorb, as well as the heating required to regenerate the desiccant, were greatly reduced. The final cooling was only “sensible” cooling and also was minimized. The result was a system that reduced energy consumption by more than 50 percent compared to the alternative system that used a desiccant dehumidifier as the first stage.
A Cool, Dry Solution to a Frosty Problem
May 1, 2008