Archive for the ‘DEHUMIDIFIER’ category


May 1st, 2014


Dehumidification is the removal of water vapor from air of an area.

Methods of Dehumidification

Cooling; Refrigeration of the air below its dew point (temperature at which air must be cooled at constant pressure in order for it to become saturated with respect to a plane surface of water) is the most common method of dehumidification. This method is advantageous when the gas is comparatively warm, has a high moisture content, and when the outlet dew point desired is above 40°F.

Liquid Desiccant; Liquid desiccant conditioners (absorbers) contact the air with a liquid desiccant, such as lithium chloride or glycol solution . The water vapor pressure of the solution is a function of its temperature and its concentration. Higher concentrations and lower temperatures result in lower water vapor pressures.

Dehumidification equipment: DEHUMIDIFIER

A Dehumidifier uses refrigeration principles same as the way an air conditioner does, but it doesn’t cool the air—in fact, it warms it slightly. Warm humid air from the structure/place is drawn into the cold dehumidification coil of the dehumidifier. Then the temperature of the air is lowered below the dew point condition and water (humidity) is collected on the dehumidification coil.

During the dehumidification process heat produced as water vapor becomes a liquid. This latent heat is then collected by the refrigerant system along with the heat taken from the entering air stream (sensible heat). Along with the latent heat, the energy used to operate the refrigerating compressor is also collected as heat energy and added to the refrigerant. Latent heat and compressor heat is then transferred by the refrigerant system to the condenser (re-heat) coil of the dehumidifier where it is added back into the air stream.

Construction of Dehumidifier


A dehumidifier is a box that contains

  • cold evaporator coils,
  • warm condenser coils,
  • a fan, and
  • a reservoir or drain to catch water

The fan blows moisture-laden room air over the cold coils, where water condenses and drips into the pan or drain. The drier air then blows across the warm coils and back into the room.

Although a dehumidifier does not cool the air, it makes it more comfortable because it decreases the humidity. But a dehumidifier does not function well under about 65 degrees F.

A dehumidifier’s fan must have electric power, the evaporator coils must contain a proper charge of refrigerant, and the controls must work for the dehumidifier to operate.

In the same way that a thermostat controls a heater or air conditioner, a dehumidifier is cycled off and on by a humidistat that measures a room’s humidity.

Types of Dehumidifiers

There are many types of Dehumidifiers; some of them are listed below, each of its own advantage and disadvantages.

Heat pump dehumidifiers extract water from the air by using a heat pump that is similar to an air conditioner pump. First, a fan pulls the indoor air across a very cold coil, which causes the moisture to condense. The droplets drip into a bucket inside the unit. The dry air is warmed by a second, heated coil and exhausted at room temperature. These dehumidifiers are considered among the most effective.

Chemical absorbent dehumidifiers work best in warm climates. They use a chemical drying agent, or desiccant, on a heat exchange wheel to absorb water molecules from the air. Damp air is sent outside via vents. Desiccant dehumidifiers use a lot of energy. They are more commonly used by industries than homeowners.

Dehumidifying ventilators have a sensor controller and exhaust fan. The sensor controller activates the unit when humidity reaches a specified level. Dehumidifying ventilators are less effective in muggy climates because they draw outside air into the house. These dehumidifiers often are used in basements. But they can depressurize a room and cause gas spillage. Make sure gas furnaces are properly vented.

Portable dehumidifiers are the kind that you usually see in the home improvement aisle; they’re often plastic, relatively cheap and very lightweight. They’re designed to be most effective in smaller spaces like a bedroom or kitchen.

Restoration humidifiers are heavy-duty machines that can withstand harsh conditions — they’re usually used to repair heavy water damage caused by hurricanes or other natural disasters.

Application of Dehumidifier

Some commercial application of dehumidifier are:

• It lowers the relative humidity to facilitate manufacturing and handling of hygroscopic materials
• It lowers the dew point to prevent condensation on products manufactured in low-temperature processes
• It provides protective atmospheres for the heat treatment of metals
• It controls humidity in warehouses and caves used for storage
• It preservers ships, aircraft, and industrial equipment that would otherwise deteriorate.
• It maintains a dry atmosphere in a closed space or container, such as the cargo hold of a ship or numerous static applications
• It eliminates condensation and subsequent corrosion
• Drying air to speed the drying of heat-sensitive products, such as candy, seeds, and photographic film.
• Drying natural gas.
• Drying gases that are to be liquefied.
• Drying instrument air and plant air .
• Drying process and industrial gases .
• Dehydration of liquids .
• Frost-free cooling for low-temperature process areas such as  brewery fermenting, aging, filtering, and storage cellars; blast  freezers; and refrigerated warehouses.
• Frost-free dehumidification for processes that require air at a subfreezing dew point humidity.

Preventing the mold growth and allergies using Dehumidifier

Dehumidifiers can help mitigate the effects of common allergies to dust mites, fungus and mold; if the air at a place is excessively moist, it can encourage the growth of these allergens.Mold only requires a bit of moisture to grow, and it can set up shop at a place as soon as one of its airborne spores finds a hospitably damp surface. A mold problem can cause serious illness. And once it shows up, mold is a pain to eradicate and can permanently stain or damage whatever it’s decided to live on. The easiest strategy is to just keep it from showing up at all.

Safety Notes

1 .Do not connect unit to any AC electrical socket that is damaged.

2 .Ensure filter and removable water tank are correctly installed before turning on unit.

3. Always turn off the dehumidifier at the control panel when not in use and before unplugging.

4. Do not use it in the following locations:

i) Next to a source of heat

ii) an area where oil and water is likely to splash

iii) an area exposed to direct sunlight

iv) near a bath,shower or swimming pool( where the unit can get wet)

v) in a green house

5. Never insert your finger or other foreign objects into grills or openings.