A solid hygroscopic agent is a solid substance that can absorb water vapor from the air, also known as a solid desiccant. It utilizes porous materials with large surface areas to absorb moisture from the air through surface adsorption and capillary condensation. Because the water vapor partial pressure on the surface of the solid hygroscopic agent is lower than the water vapor partial pressure in the air, it absorbs moisture from the air to achieve dehumidification.
Solid desiccant is a solid substance that can adsorb water vapor from the air, also known as a solid desiccant. It uses porous materials with a large surface area to absorb moisture from the air through surface adsorption and capillary condensation. Because the water vapor partial pressure on the surface of the solid desiccant is lower than the water vapor partial pressure in the air, it absorbs moisture from the air, achieving the purpose of air dehumidification.
The most commonly used solid desiccants are silica gel and calcium chloride. On the enthalpy-humidity chart, the air processing process using solid desiccants is an isenthalpic temperature rise. When Solid desiccant in contact with moist air, the solid desiccant absorbs moisture from the moist air and releases latent heat of vaporization, causing the air to warm up, while the enthalpy of the air before and after dehumidification remains unchanged.
A typical application of solid desiccants in evaporative cooling air conditioning technology is in wheels. Rotary dehumidifiers use solid desiccants to absorb moisture from the air to achieve air dehumidification. The key component of a rotary dehumidifier is the wheel, which is composed of corrugated media made of special composite heat-resistant materials, and the corrugated media contains solid desiccants.
The advantages of using solid desiccants are that the equipment is relatively simple and the investment and operating costs are lower.
The disadvantages are that the solid desiccant needs to be regenerated after absorbing moisture to a certain extent, and the dehumidification performance is not stable, so it is suitable for use in places with smaller dehumidification requirements.
Liquid desiccant is a liquid substance that can absorb water vapor from the air, also known as a liquid desiccant. Liquid desiccant dehumidification uses the strong hygroscopicity and moisture holding capacity of the liquid desiccant to directly treat the air. When the liquid desiccant comes into direct contact with moist air, the driving force is the difference between the partial pressure of water vapor in the air and the saturated vapor pressure on the surface of the liquid desiccant, thereby achieving the effect of air dehumidification. During the dehumidification process, the liquid desiccant will release heat, which is the heat released when the moisture in the air changes from gaseous to liquid state. The moisture content of the moist air decreases, and the liquid desiccant absorbs the moisture in the air to become a dilute solution. On the enthalpy-humidity chart, depending on the concentration and temperature of the liquid desiccant, an isenthalpic dehumidification process and an isothermal dehumidification process can be achieved.
In air conditioning engineering, the liquid desiccants used include calcium chloride, lithium chloride, and lithium bromide. Calcium chloride desiccant has the worst hygroscopicity and has strong corrosiveness; lithium chloride and lithium bromide desiccants both have strong hygroscopicity and are widely used at home and abroad. The main advantages of using liquid desiccant dehumidification are that it can achieve a large reduction in air humidity, making the air reach a very low moisture content; while the disadvantage is that the liquid desiccant dehumidification process requires a set of brine regeneration equipment, the system is complex, the initial investment is high, and it is suitable for places with very low moisture content requirements.
Gas Desiccant is a special gaseous dry air that can dilute water vapor from moist air by mixing with moist air, also known as a gaseous desiccant. Gas desiccant dehumidification utilizes the heat and mass transfer process that occurs when two air streams with different humidities (dry air and moist air) are mixed, thereby achieving the effect of moist air dilution dehumidification. Gas desiccants do not require regeneration, have stable dehumidification performance, and are a low-cost, green desiccant.
Compressed air dehumidification device
Compressed air has been widely used in petroleum, oxygen production, and aviation industries. In addition, compressed air, as a medium for dry air, i.e., "gas Desiccant ", can be combined with evaporative cooling technology for use in air conditioning, such as some mine air conditioning, and in recent years, it has been increasingly used in textile factory air conditioning. High-pressure jetting uses compressed air as a refrigerant. Compressed air is ejected through a high-pressure nozzle, and the compressed air comes into contact with moist air. After adiabatic expansion, it absorbs heat from the air. At the same time, the dry compressed air and moist air absorb moisture from the moist air through entrainment and mixing, achieving the effect of air dehumidification.
