Cabinet Type Humidifiers
Automizing Type Humidifiers
Ultrasonic Humidifiers Or Pan Type
Chemical De-Humidification
Chemical De-Humidifiers
Room Dehumidifiers
Humidistat is used to control the level of humidity. Too much humidity may cause swelling of hygroscopic materials (wood products) and may cause condensation on cold surface. Such as windows, window frames and doors. It may also condense inside the outside walls. Excess humidity should be avoided because mol and rot can occur at 70 percent RH. Electric Humdifiers Building which have steam heated, hydronic heated or warm air heated equipment are examples of installations that can use an electric humidifier. Warm air heating units sometimes are equipped with humidifiers that use the warm air as a source of heat, however, if the humidifier water is r separately heated, the amount of humidification can be more accurately controlled. The electric humidifier has the advantage of case of installation, flexibility of location and accuracy, of humidity control. As shown in the figure an electric humidifier designed for use in a duct installation. This unit has an 800 watt electric heating coil which is controlled by an adjustable humidistat water level is controlled by a pan type float which operates a switch in the solenoid water valve circuit. Cabinet Type Humidifiers The use humidifier is required in many situations that are separate from and independent of the heating system. They are popular when a hydronic or steam heating system is used. Many are used with warm air heating systems. Independent humidifying units are housed in an attractive cabinet and usually consist of a large wheel or drum which has a rim of porous material. A humidistat control a fan motor, which drives the large wheel that is wetted as it dips into a water reservoir. As the air flows through the wet, porous, rim most of the moisture evaporates and adds moisture (water vapor) to the air. Some of the units have an electric heater to warm the outlet air. The water reservoir is manually filled with water. A float operated switch will turn on a signal light when the water level is low. The unit is easily maintained. The water tank and the porous wheel rim can be removed and clean. A cabinet type humidifier in which a porous filter revolves and picks up moisture. Air blown through porous material vaporizes some of the water, rising the humidity in the room A- power cord B- humidty switch, indicator lights C water tank F- switch light which, when lit, indicates that water tank is empty. Automizing Type Humidifiers Atomizing means producing a fine spray. When liquid water is atomizes, the smaller the diameter of the water drop lets, the greater inter facial area between water and air and thus the higher the rate of the evaporation and humidification. When air flows through an atomized water spray from an atomizing humidifier, if the difference between the temperature of the water spray and the wet-bulb temperature of the ambient air is small, the result is an increase in the humidity ratio of air from the additional of evaporated water vapor and a corresponding drops in air temperature because of the absorption of required latent heat of vaporization from the ambient air such a humidification process is an adiabatic saturation or evaporative cooling process and follows the thermodynamic wet-bulb temperature line on the psychometric chart. Atomizing humidifiers can be classified, according to their configuration and mechanism of the atomizing as ultrasonic humidifiers, centrifugal atomizing humidifiers, pneumatic atomizing humidifiers and air washers. Ultrasonic Humidifiers Or Pan Type An ultrasonic humidifier uses piezoelectric transducer to convert high frequency mechanical electric signals to a high frequency oscillation. The transducer is submerged into a water pan in which water is well treated and dematerialized the negative oscillation produces a momentary vacuum that causes the water to cavity into the vapor at low pressure. The positive oscillation creates a high-compression wave which forces the water particles to low the water surface and inject into the air stream water films are them broken into fin mist. Air condition this mist can be blown into the space directly or through an air system by a fan. If the water is well treated, it will be free of mineral deposits, and no filter is required down-stream from the humidifier. Chemical De-Humidification In some installations, certain chemicals are used which can be absorb moisture from the air where used, the chemicals- are usually cycle in such a way that first the moisture from the air is absorbed into the chemical then the chemicals are heated. Moisture driven from the chemical is exhausted out of the doors and the chemicals are ready to once more absorb moisture. Chemical methods of removing moisture from air used in many ways industrial processes requiring a low dew point temperature. Chemical De-Humidifiers The components of an absorption equipment dehumidification apparatus area tray or rack to contain the adsorbent, a blower to force moist air through the bed, and a source of heat to reactivate the adsorbent. A silica gel adsorption machine of the continuous type is shown in the figure given below A drum rotating 5 to 8 times revolution per hour forms the gel bed. A single motor drivers two blower, are drawn moist air through the gel bed and distribution system: the other draw heated air through the gel bed, from reactivation and exhausts hot moist air. The reactivation process leaves the bed hot. Therefore, unless the dehumidifying process requires hot dry air for dehydration it is customary to subject the bed to a cooling cycle in order not to add any residual reactivation heat to the conditioned air suitable drag seals are provided on both the inside and outside of the drum in order to separate the drying reactivation, and cooling process. Water vapor condenser within the pores of the absorbent and heat is released is equal to the sum of the latent heat of condensation of the vapor, plus the heat of reaction. The heat is released in the from of the sensible heat and causes the air temperature flowing through. or over the adsorbent bed to rise. Room Dehumidifiers Typically dehumidifier consists of a hermetic compressor. Condenser, And evaporator using a capillary tube refrigerant control. See figure given below. In the schematic diagram dark red indicates high-pressure liquid and dark blue. low-pressure liquid light blue indicates, low-pressure vapor and light blue high-pressure vapor. Liquid refrigerant collets in the lower coils of the condenser it flows through the filter into the capillary tube. Then it is moved into the evaporator, which is under low-pressure. In rapidly it picks up fan forced large amounts of air through the evaporator. Due to the low evaporator temperature, moisture carried in the air condenser (is charged to liquid) on the evaporator temperature, moisture carried ‘in the air condenser (is charged to Liquid) on the evaporative surface. The moisture drips to the bottom of the evaporation and into the condenser trough. Air flowing through the evaporation is both cooled and dehumidified. Cooled air is then forced through the condenser. There, it cools the condenser and again picks up heat. Therefore, the air leaving the humidifier is about the same temperature as it was when it entered. How ever, air discharged by the dehumidifier has a lower relative humidity than the intake air low-pressure vapor is drawn from the evaporator through the suction line to the compressor it is again compressed to high-side pressure and is forced into the condenser. Here it is cooled and becomes a liquid. The cycle is repeated. In addition to a ON-OFF switch, dehumidifiers usually have two other controls. One is humidistat used to regulate humidity it permits the humidifier to operate until the desired relative humidity is reached. The control then shuts the machine off the other is a frost, control element this is placed in the suction line between the evaporator and the compressor. It stops the motor compressor when a sufficiently high temperature is reached therefore, the evaporator will not freeze over and stop the flow of air through it. In the drawing arrows in black show the direction of air flow through the dehumidifier. A fan is commonly used to move the air.
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