Knowledge about air dehumidification-Shenzhen Tony Electronics Co.,ltd.

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Knowledge about air dehumidification

Writer：dl-admin2010-07-21 00:00 HEAT：885

Summary: The principles and purpose of dehumidifier: now it is used the most effective way of freezing dehumidification in dehumidifier. According to the characteristics of the air, air moisture in the indoor can be coagulated constantly into drops of water when the temperature is low, and drops of water are wiped out to storage tank or outdoor. This makes indoor humidity decreasing constantly, and obtains the purpose: the air is dried.

(A) Influence and hurt of humidity

In our daily life, people always live and work in a great deal of disturbance when change of weather and seasons.

Especially the moist air on the human body comfort, on the products quality, on technical process and equipment maintenance, all will have a direct impact.

When it is rainy season or hot season, people feel uncomfortable hot, goods will damp and will cause mildew, oxidation, rust, deterioration and aging. The instrument or equipment will result in abnormal by wet, and will shorten life. It is difficult to guarantee product quality in production process. High humidity will accelerate the breeding of bacteria, and it is a serious impact on people’s living environment and health. All of these instances, are the feelings of us on the impact and harm of wet in the air.

Therefore, when the humidity is too high, we must take effective dehumidified measures to reduce humidity in the air, in order to the environment becomes dry and comfortable. When in spring and summer, if air relative humidity is > 60%, metal items will rust and biological products will go moldy, paper products will become weak, people will sense of suppression in the chest. In this case, it is required to dehumidify down to <60%.

When in autumn and winter, if the relative humidity is <40%, because of too little moisture in the air, accumulated static electricity can not be conducted underground, so if you wear sweater or pull the door, you will have a feeling of shock. IC, crystal oscillator, and other components will be knocked down by accumulated static electricity. Requirement of humidification at this time is increasing to > 40%.

Low humidity is required in some specific industries, such as laminated glass <25% (Construction laminated glass and automotive laminated glass are produced in clean, constant temperature and humidity conditions and combined with PVB film), capsules drying <22%, lithium battery injection liquid <1% (gather lithium).

High humidity is required in some specific industries, such as tobacco >60%, printing >70%, textile > 65%, mushroom >80%, aging laboratory >90%.

(B) Humidity Range for goods storage and equipments use

(At room temperature) Relative humidity % HR. Here are environments for goods storage and equipments: 60~50% for household articles, offices, computers rooms, print workshops, foods processing, leather products, vacuum coatings, craftworks colors boxes, and materials warehouses; 50%~60% for audio-visual equipments, antiques calligraphy, medicine and tea, food and tobacco, telecommunications equipments, books, files, storage warehouse; 40%~30% for precision instruments, measuring instruments, optical components, chemicals, polymers, semiconductors and seed preservation.

A: The main functions of air condition are refrigeration and heating, an air condition with dehumidification function can dehumidify, there is a small amount of desiccant and quite slowly, and cold wind was blown out, then the more dehumidification, the more cold it is. In addition, since air condition is fixed installation, only in the scope of local small dehumidifier, more importantly, when the air condition dehumidified independent, it needs to increase several times load to operate, and it is not only large power consumption, but will also damage the compressor, that is, period use of compressor is shorten. So air condition can not replace dehumidifier.

Storage is usually not allowed to dehumidify under decrease temperature condition, because after decrease cooling, it will coagulate water drops on the surface of goods when hot air joints in (there is moisture in the hot air), that means it is more affected with damp. So it should not use air condition to decrease temperature for dehumidification. Dehumidifier dehumidifies at smooth temperature or dehumidifies at slightly warming temperature.

(D) How to select dehumidification mode

1. According to region climate conditions. Common climates are known as following: (1) high temperature and high humidity - in the hot summer mugginess weather; (2) high temperature and low humidity – dry and hot season in northern hot and arid climate; (3) low temperature and high humidity – the southern rainy season; (4) low temperature and low humidity – usually cold weather in northern.

Usually climates mainly need to dehumidifying are (1) and (3), if there is a hot and humid area, it is recommended air conditioner. And because it is used of cooling mode, the temperature will also come down in the dehumidification process. If there is a low temperature and high humidity area, it is recommended with independent dehumidification air conditioner or a dehumidifier.

2. According to situation. For the living situation, use air conditioner to dehumidify should be more economical, as the most suitable air humidity of 60 to 70% for person, this humidity is easy to realize when use air conditioner. Noise of dehumidifier is more loudness than noise of air conditioner, especially of large power dehumidifier. So air conditioner is the first choose for the living situation.

3. According to using objects. For industrial products such as optical lenses, magnetic recording materials (including CD-ROM), video film, electronic information media, electronic components, instruments, meters, powder materials, paper, wood, silk, leather, tobacco, food, tea, grain, it is need to strictly control the humidity, so use professional dehumidifier will get a obvious effect. It is recommended to use dehumidifier to dehumidify.

(E) Types of dehumidification mode

1. Cold adjust dehumidification, cool the air to below the dew point, and then remove coagulate water. It is effective mode when situation is above the dew point.

2. Compressive dehumidification, first to compress the humid air, and cool it, at last to separate the water. It is effective mode when air flow is low, but it is not suitable when the air flow is large enough.

3. Rotor Wheel absorb dehumidify, process the thin plate that immersed hygroscopic agent (for example: silica gel) into wheels with honeycomb type for ventilation, let the wind through it. Dehumidification structure is simple, and the dew point can down to - 70℃ when the structure with a special combination. It is mainly used in glass, capsules, batteries, pharmaceuticals and other industries.

(F) Humidity parameters

1. Web bulb temperature (℃), temperature of wet gauze wrapped on the thermometer thermal bulb (that is, the relative humidity is 100% saturation);

2. Dry bulb temperature (℃), temperature of the thermometer thermal bulb without wet gauze.

The difference of web bulb temperature and dry bulb temperature reflects the air humidity data.

3. Dew point temperature (℃), cool some certain state of air along the constant humidity line (refer to the graph), when there is coagulated water, temperature at this time is called dew point temperature (i.e. relative humidity reaches 100%).

4. Relative humidity (%), degree of water saturation in the air, ratio of water vapor partial pressure to saturation pressure. It is the greater value the more humid.

5. Moisture content (g/kg), gram value of water vapor in per kilogram weight of dry air.

6. Enthalpy (kw/kj), energy of a certain point in the air, in order to select the compressor or electric heating power.