What Are the Different Methods of Humidity Control?

When the indoor load of the building is part of the design load, by reducing the chilled water flow and reducing the cooling capacity of the refrigeration unit, the indoor temperature can be controlled to remain constant, but this will reduce the dehumidification capacity of the air conditioning unit, which will increase the indoor relative humidity. The relative humidity is out of the allowable range and it needs to be controlled.

1. Indirect control method: For a certain indoor humidity production or small fluctuation of humidity production, as long as the dew point temperature L of the machine is controlled, the indoor relative humidity can be controlled. This method of controlling the relative humidity of the room by controlling the dew point temperature of the machine is called an indirect control method. E.g:

(1) The fresh air and return air mixing valves are controlled by the dew point temperature of the machine. This method is used in winter and transition season. If the spray booth is sprayed with circulating water and the outdoor air parameters change, it is necessary to keep the dew point temperature of the machine constant. Then, a dry bulb temperature sensor T _L can be installed behind the spray booth flap. According to the required dew point temperature given value, the fresh air, return air and exhaust air linkage valves are controlled by the actuator M ratio.

(2) The spraying temperature of the spraying room is controlled by the dew point temperature of the machine. This method is used in summer and the transition season when using chilled water. A dry-bulb temperature sensor T _{L is} set behind the water spray plate of the water spraying room. According to the given value of the required dew point temperature, proportionally control the three-way mixing valve in the cold water pipeline to adjust the spray water temperature to keep the dew point temperature of the machine constant.

Sometimes in order to improve the quality of adjustment, the given value of the dew point temperature of the machine should be corrected in time according to the change of the indoor humidity production. A humidity sensor can be added in the room. When the indoor relative humidity increases, the humidity sensor lowers the given value of T _L. Conversely, the given value of T _L is increased.

2. Direct control method: For the situation where the indoor humidity production changes greatly or the indoor relative humidity requirements are strict, you can directly set a wet bulb temperature or relative humidity sensor in the room, control the corresponding adjustment mechanism, and directly perform the indoor relative humidity deviation. Adjust to compensate for changes in indoor heat and humidity loads. This method of controlling the relative humidity in a room is called the "direct control method". Compared with the "indirect control method", the quality of regulation is better, and it has been widely used at home and abroad. ^[1]

The importance of correct humidity control and the main purpose of air humidification is to prevent direct or brief adverse effects on the human body or the surrounding environment due to the relatively low relative humidity of the air. The ideal relative humidity is 40-60% RH. Its importance and possible humidification purposes are listed below:

1. Improve life comfort and health: proper air relative humidity can increase life comfort and improve physical health. The relatively low relative humidity of the air can cause dry skin and itching.

2. Prevent the occurrence of static electricity: Generally speaking, static electricity will occur when the relative humidity of the air is lower than 40% RH.

3. Improve and promote the speed of wound healing: When the relative humidity of the air is too low, the surgical wound is likely to cause slow and bad wound healing due to the evaporation of skin moisture.

4, in accordance with the needs of environmental testing or greenhouse: artificial climate needs to control the temperature and relative temperature of the air, in order to facilitate environmental experiments under various temperature and humidity conditions.

5. Prevent the fiber from cracking: When the relative humidity of the air is too low, it will cause the fiber of the fiber product to crack and affect the product quality and production efficiency.

6. Reduce costs and increase profits: When the room temperature is slightly higher and the air is dry, it will make people feel uncomfortable. Usually this environment is a hotbed of many bacteria, which will cause employees to catch colds, sore throats, and indirectly affect productivity. Moderate, not only can reduce the indoor temperature and will not affect the comfort and productivity of employees' working environment. But judging by the benefits of increased productivity and reduced sick leave rates, air humidification is a viable option.

7. Eliminate or avoid odor: It has been verified that the sensitivity of olfaction will be lowered due to the increase of relative humidity, even to the extent that it can not smell. If the relative humidity of an enclosed space is higher than the surrounding relative humidity, the space Internal odors will disappear quickly; the exception is volatile or evaporative substances, such as paint.

8. Improve sound wave transmission: The transmission quality of sound waves penetrating air will be affected by the relative humidity and transmission frequency; the optimal humidity environment for transmitting sound waves is 40-50% relative humidity, and 15-20% relative humidity cannot transmit sound waves; However, the higher the transmitted sound frequency, the less affected by relative humidity.