Dehumidification is the process of removing moisture from air. The two primary dehumidification technologies used in the drying industry are refrigerant and desiccant. Refrigerant dehumidification involves cooling the air below its dew point, causing moisture to condense. Desiccant dehumidification places air in contact with a desiccant material that removes moisture by direct sorption. In closed-drying systems, dehumidification is essential for removing evaporation moisture from air to promote drying and minimise or prevent secondary damage. Dehumidifiers of sufficient performance and capacity are necessary in most environments to create an effective drying system, but this is not always the case.
Conventional and low grain dehumidifiers remove moisture from air by the process of condensation. They contain a sealed refrigeration system, defrost mechanism, a fan and a water collection system (e.g. drip tray and pump). The dehumidifier removes energy from the incoming air, then returns this energy as sensible heat to the exiting air. During the energy removal process, water vapour condenses on the evaporator coil and is collected
Low-grain refrigerant (LGR);
LGR’s contain modifications to conventional refrigeration system that result in cooling the process airstream to a significantly lower temperature, using various energy exchange systems. This allows the LGR to remove additional energy across the cooling components (e.g. pre-cooling coil, evaporator coil) resulting in a lower exiting humidity (i.e. dew point, humidity ratio, and vapour pressure) and greater moisture removal capacity.
Desiccant dehumidifiers work on the principle of sorption with the key component being a slowly turning desiccant impregnated rotor or wheel; typically silica gel. The rotor revolves through two seperate air streams; process and reactivation.Process air enters the unit and the desiccant sorbs water vapour. The dehumidified process air then exits the unit and is delivered to the affected area.
The water vapour is sorbed by the rotor from the process air stream is then desorbed in the reactivation air stream. The reactivation air stream is heated, causing the desiccant to release its moisture. The moisture-laden reactivation air then exits the dehumidifier and is delivered to the outdoor environment. Desiccant dehumidifier utilise vapour differential to remove water and can be effective across a broad range of atmospheric conditions. To compensate for sensible heat gain in the affected area, Pre-cooling the desiccant or post-cooling may be added to process the air stream of the desiccant as well as deliver a lower process outlet temperature.