Refrigeration Dehumidifier by Halward

Refrigerant Dehumidifier   The most common dehumidifier used is the refrigerant type. It is cheap to produce, easy to operate and effective in most domestic and commercial applications. The primary benefit of a refrigerant dehumidifier is that it performs exceptionally well when used in warm, humid conditions. One of the most important things to understand about a refrigerant dehumidifier is that the performance is directly related to the difference between the air dry bulb temperature and the air dewpoint temperature.   A refrigerant dehumidifier is essentially a re-arranged portable air conditioning unit, where the air is first passed across the evaporator coil to cool it, then across the condenser coil to heat it. The air becomes both warmer and drier. The cold evaporator coil reduces the air temperature to a point where condensation occurs. Condensation formed on the cold coil then drips into a collection tray. Water is either drained away or collected in a container in the base of the unit. As the surrounding air becomes drier the dewpoint is lowered, so the temperature necessary to create condensation on the cold evaporator coil, also becomes lower. Even with an evaporator coil temperature of 0°C, it is unlikely that the air will be reduced much below 10°C dewpoint (it is worth noting that air at 20°C, 50% RH already has a dewpoint below 10°C). If the dewpoint of the air is already low, the coil temperature necessary to create condensation can easily be subzero. At this point, the operating efficiency of a refrigerant dehumidifier is greatly reduced. The evaporator begins to freeze as airborne water vapour makes contact with the cold tube surface. Defrosting of the coil is then necessary. Defrosting is normally achieved by allowing hot refrigerant gas from the compressor directly into the evaporator coil. During the defrost cycle, the dehumidifier process ceases to remove water from the air.