DEHUMIDIFICATION DEFINITION AND HVAC BASIC TUTORIALS


Dehumidification
Dehumidification occurs when air passing through a chilled water coil, a refrigerant coil or a chemical dehumidifier releases moisture and is dehumidified. The air leaves the dehumidifier at condition point A (70°FDB and 10%RH).

In this example, the dry bulb temperature remains constant while the wet bulb temperature, dew point temperature, relative humidity and specific humidity decrease. In a typical commercial and industrial cooling coil HVAC system, using either a chilled water coil or a refrigerant coil, the psychrometric process is both cooling and dehumidification simultaneously (see below). When using a chemical dehumidifier, the process is heating and dehumidifying.


Heating and Humidification
Both heating and humidification occurs when air passes through a warm water spray or steam. The air absorbs moisture and is humidified and heated simultaneously. The air leaves the spray at 80°FDB and 50%RH (condition C). The dry bulb temperature, wet bulb temperature, dew point temperature, relative humidity and specific humidity increase.

Cooling and Humidification
When air passes through cold water, either a spray or a wetted pad, it absorbs moisture and is humidified and cooled simultaneously. This is “evaporative cooling” and is effective in dry (arid) areas with low relative humidity. The air leaves the spray at 80°FDB, 70°FWB and 61%RH (B). The wet bulb temperature remains constant while the dry bulb temperature decreases. The dew point temperature, relative humidity and specific humidity increase.

Heating and Dehumidification
When air passes through a chemical dehumidifier the psychrometric process is heating and dehumidifying following along a constant wet bulb line. The air leaves the dehumidifier at condition point D (80°FDB, 60°FWB and 30%RH). The wet bulb temperature remains constant while the dry bulb temperature increases. The dew point temperature, relative humidity and specific humidity decrease.

Cooling and Dehumidification
Air is dehumidified and cooled simultaneously by passing it through sprays of cold water or over a cold surface such as an energized refrigerant coil or chilled water coil. The most common type of HVAC cooling is “mechanical cooling” using a cold surface.

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1 comment:

Robin Peterson said...

Your article is written very articulately and gives a very good explanation about commercial hvac systems. Great post! This article should be read over and over again.

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