Absolute humidity refers to the amount of moisture in the air (kgmoisture/kgdry air)
Relative humidity (%) is the ratio of the actual amount of moisture to the maximum amount of moisture the air can hold, expressed as a percentage. The maximum amount of moisture the air can hold varies with temperature. As the temperature rises, the amount increases, and conversely, as the temperature falls, the amount decreases. What we commonly refer to as humidity in daily life means relative humidity.
In the diagram, even if the absolute humidity is constant, if the temperature drops, the maximum amount of moisture the air can hold decreases, and thus the relative humidity increases (1→2).
When the air holds more moisture than it can, the excess humidity turns into condensation and is removed from the air(2→3).
Understanding Dew Point Temperature
An important concept in humidity management is the dew point temperature. This is the temperature at which condensation begins to form when you cool the air.
When air is cooled down to its dew point temperature, the relative humidity becomes 100%. It's only when the air is cooled below its dew point temperature that condensation actually forms and water droplets appear
How Air Conditioners Dehumidify: Removing Moisture by Lowering Temperature
Inside a typical air conditioner's indoor unit, there's a cold surface. As air passes over this cold part, its temperature drops. When the air temperature goes down, the maximum amount of moisture the air can hold decreases. Any moisture exceeding this reduced capacity then turns into water droplets (condensation) and is removed.
In essence, air conditioners remove moisture by forming condensation on a cold surface. For this to be effective, the temperature of that cold surface must be lower than the air's dew point temperature.
Air Conditioner Causing Mold? Here's Why!
Air conditioners are great at cooling things down, but there's a sneaky side effect often overlooked. As the temperature drops, condensation can form. This happens when water vapor in the air turns into liquid droplets. Here's the tricky part: even though the actual amount of water vapor in the air (absolute humidity) decreases, the relative humidity can paradoxically increase.
And why does that matter? Mold can grow anytime the relative humidity is above 70%, even at lower temperatures. This makes the inside of an air conditioner, where condensation easily forms and relative humidity can spike, a perfect breeding ground for mold.
So, while your air conditioner seems to be removing moisture as it cools, it can actually create an environment where mold thrives. It's just like how mold grows in any damp place with condensation. Keeping your air conditioner mold-free can be a real challenge!
How Dehumidifiers Work
Dehumidifiers essentially combine the indoor and outdoor units of an air conditioner into a single device. This design allows the air generated by the indoor unit to cool the outdoor unit.
The dehumidification process itself is identical to that of an air conditioner: moisture is removed from the air when water vapor comes into contact with a cold surface, causing condensation (dew formation). The key difference between a dehumidifier and an air conditioner is that dehumidifiers expel warm air during the dehumidification process.
The Challenge of Dehumidifying in Cooler Conditions In typical dehumidification, moisture is removed through condensation, which requires lowering the temperature. However, if the cooling surface drops below 0°C (32°F), ice forms instead of condensation, making it difficult for the equipment to function properly.
This becomes especially problematic when the air temperature falls below 15°C (59°F), as the cooling surface temperature can also dip below 0°C, causing the dehumidifier to stop working.
Furthermore, if the air humidity is low and the dew point temperature is below 10°C (50°F), the cooling surface temperature needs to be even lower than the dew point to remove moisture effectively. Since the temperature can't go below 0°C, the dehumidification performance and efficiency will significantly decrease.
The Hidden Energy of Water: Evaporation, Condensation, and Latent Heat Water molecules move differently depending on their state: their movement is restricted in liquid form but much freer in gas (vapor) form. This significant difference in kinetic energy between liquid and gaseous water means that energy must be either added or removed for these state changes to occur.
When liquid water transforms into gaseous humidity, we call this evaporation. Evaporation requires adding energy, for example, through heating. Conversely, when gaseous humidity turns back into liquid water, it's called condensation. Condensation requires removing energy, typically through cooling. This energy difference associated with state changes is known as latent heat.
Humidity carries significantly more energy than liquid water, specifically by the amount of its latent heat. To increase the absolute humidity of air by just 1 gram per kilogram (g/kg), you need to add the same amount of energy required to heat the air by 2.5°C.
Humidity: The Silent Killer of Metal Products!
Did you know that humidity significantly impacts the lifespan of metal products?
When relative humidity climbs above 60%, an invisible, thin film of water droplets (a "moisture adsorption layer") begins to form on metal surfaces.
This isn't just plain water. This moisture adsorption layer acts like an electrolyte, accelerating the metal corrosion process.
Through this layer, oxygen and various ions can easily move, which promotes the oxidation of the metal, drastically speeding up the rate of corrosion.
Ultimately, higher relative humidity means more severe corrosion for metal products.
Transpiration: How Plants "Sweat" and Why It Matters Transpiration is the process where plants release water vapor into the air from their leaves, stems, and flowers. This seemingly simple act is actually the main force that drives plant roots to absorb water and minerals from the soil. In fact, most of the water a plant takes in (over 95%!) is released back into the environment through transpiration.
This process is crucial for plants not only to release excess moisture but also to regulate their own temperature through evaporative cooling. However, if the surrounding humidity is too high, it reduces water evaporation from the plant's surface, which can hinder transpiration. When transpiration is slowed down, it can lead to stunted plant growth.
Same temperature, no humidity. Humicon features desiccant technology that helps maintain optimal humidity at 40%. It also includes air purification and ventilation functions, ensuring fresh and clean indoor air.
Huzero is an industrial dehumidifier designed for low-temperature and extremely low-humidity environments to improve factory productivity, offering energy efficiency 60% higher than existing market products.
Husheet is an innovative and patented technology, ultra-slim dehumidifier that can control humidity as well as deodorizing. It also has dehumidifying, deodorizing, antibacterial, and anti-fungal functions.
Protect your valuable clothes and belongings from humidity with Huspot, a desiccant dehumidifier designed specifically for dressing rooms in your home. Huspot effectively removes moisture from bathrooms and other areas using advanced desiccant technology, and safely release the humidity outside. Therefore, it is not neccessary to empty a water tank, install pipes, or worry about water leaks. Huspot can be installed on the ceiling, allowing you to maximize the use of your dressing room space while maintaining an optimal humidity level for your clothes and accessories. Keep your dressing room fresh and humidity-free with Huspot.
