Dehumidification is a crucial process in managing indoor air quality and comfort, particularly in humid environments. By reducing the moisture content in the air, dehumidifiers help prevent mold growth, improve respiratory health and protect equipment from damage.
Many business owners turn to dehumidifiers to fight excess humidity. But what does a dehumidifier do, and how does it work? In this guide, we’ll explore the process behind dehumidification. Whether you’re dealing with excess humidity or simply aiming for a more comfortable space, understanding dehumidification can empower you to make informed decisions about your environment.
What is Dehumidification and How Does It Benefit You?
Dehumidification is the process of removing water from the air, and it is achieved through devices known as dehumidifiers. The humid air passes through the dehumidifiers, and a certain amount of moisture is removed. Depending on the dehumidifier, it is released back into the space as either warm or cool, dry air. This process is used to reduce humidity and maintain an ideal level of moisture in the air.
The Role of Airflow in the Dehumidification Process
To explain how dehumidifiers work, we need to start by looking at airflow. All types of dehumidifiers rely on air movement to remove its moisture. Generally speaking, fans pull air into the dehumidifier and move it over the drying mechanism, whether that is a desiccant material or cooling coils. As the air moves over that mechanism, the moisture is removed. It then moves to the output duct and is released back into the space.
Depending on the dehumidifier type, multiple streams of air may be involved. A desiccant wheel, for instance, needs a second stream of air to replenish the system’s ability to dry the air. Dehumidifiers that rely on condensation to remove moisture have just one airstream.
Typical Air Conditions Before Dehumidification
To compare and measure dehumidification processes, we need a benchmark that compares temperatures before and after dehumidification occurs. Understanding the relationship between temperature and the dehumidification process provides insight into its effectiveness.
Dry Bulb and Dew Point Temperatures
In most cases, we refer to incoming air as air with a dry bulb temperature of around 80 degrees Fahrenheit and relative humidity of 60%. Dry bulb temperature refers to the temperature on a thermometer that’s not affected by moisture in the air, making it a key marker when measuring dehumidification capabilities. We can also use dew point temperatures, which refer to the temperature to which the air needs to be cooled to achieve a relative humidity of 100%.
The relationship between dew point and dry bulb temperatures can be misleading because of how the percentages work. The National Weather Service provides the example that a temperature of 30 and a dew point of 30 create a relative humidity of 100%, while a temperature of 80 with a dew point of 60 generates a relative humidity of 50%. Still, that 80-degree day with a higher dew point will feel much more humid than the 30-degree day, even though the relative humidity is considerably lower.
Regardless of the temperature at which it happens, moisture starts to leave the air when the dew point is reached. It might condense onto a nearby surface or be absorbed by desiccant materials. Dehumidifiers rely on that dew point to operate. Refrigerated dehumidifiers reach the dew point by bringing down the temperature. Desiccant dehumidifiers, however, absorb moisture until the desiccant is saturated and reactivation air helps dry out the desiccant.
Other Measurements for Humidity
Another useful metric is grains of moisture per pound. Incoming air at 60% relative humidity corresponds to 92 grains of moisture per pound. These values apply to both the process air and the reactivation air.
Types of Dehumidifiers
Dehumidifiers can come in various styles, with two popular types: refrigerant and desiccant dehumidifiers. The dehumidification process varies for each type.
- Refrigerant dehumidifiers: This type of dehumidifier uses a cooling coil to condense the moisture from the air and drain the water away. The cooled, drier air is reheated before being released back into the room.
- Desiccant dehumidifiers: These dehumidifiers absorb moisture from the air using desiccant material. They feature components such as a desiccant wheel, an internal heater and a blower that work together to carry out the dehumidification process.
How Air Flows Through a Desiccant Wheel
One of the most popular types of dehumidifiers is a desiccant dehumidifier, which uses a desiccant wheel and doesn’t call for energy-intensive refrigeration. This wheel is filled with silica, the same moisture-absorbing material you often find in white packets with sensitive products like medication and electronics.
Process air, or the air pulled into the dehumidifier, is pulled through the wheel via a fan system. Moisture from the process air gets absorbed — i.e., sticks to another molecule — into the silica, sending dry air back into the space through an output vent.
However, process air only moves across about three-quarters of the wheel. The other quarter is devoted to the reactivation of air. This air is used to “refresh” the silica to absorb more incoming process air. Reactivation air enters the dehumidifier and moves across the wheel on a separate airstream. Before it reaches the wheel, reactivation air is heated to a high temperature to prime it for the next step.
When the heated reactivation air moves through the wheel, the silica releases its moisture back into it. The air remains humid, but it serves the important job of returning the silica to a moisture-absorbing state that can again dehumidify the incoming process air. Desiccant dehumidifiers can, of course, feature a few different designs, but for the most part, reactivation air moves opposite to the process air stream.
What Is Dehumidification?
This is the process of removing water from the air. Dehumidifiers reduce humidity and maintain an ideal level in the air.
Heating the Reactivation Air
Reactivation air is generally heated with an electric heating device. It brings ambient-temperature reactivation air up to a temperature as high as 284 degrees Fahrenheit. The heating process makes the reactivation air readily receive moisture from the silica. It pulls this moisture off the desiccant and takes it away, leaving dried silica on the wheel, where it rotates around to dry out the process air and keep the cycle moving.
Does Air Movement Reduce Humidity?
Air movement can reduce humidity levels by enhancing the rate of moisture evaporation and enabling the air to mix with drier air. It can lead to a more uniform distribution of humidity. Additionally, increased airflow can improve the effectiveness of dehumidifiers by helping disperse the dehumidified air throughout the space, resulting in lower humidity levels.
Air Conditions Following the Dehumidification Process
Dehumidifiers can vary in capabilities, but you can generally expect the typical air conditions after the dehumidification to include lower humidity levels, increased temperature and improved air quality. The air feels drier and more comfortable, reducing the risk of mold growth and musty odors.
Take, for example, our 400-millimeter wheel on a system that accommodates 6,000 cubic feet per minute of airflow — one of our most common models. On average, air will exit the dehumidifier at about 123 degrees Fahrenheit, with less than 10% relative humidity and 54 grains of moisture per pound. That comes from a temperature increase of 43 degrees Fahrenheit, a relative humidity decrease of 50% and 38 fewer grains of moisture per pound. (Data derived assuming 80F DB / 60% RH entering air).
These numbers illustrate how effective dehumidifiers are. Whether you need to avoid moisture in a humid climate for a building full of shoppers or achieve exceptionally low moisture content for industrial or food-grade applications, a dehumidifier can do the job.
Reach out to Smart Family to Learn More About How A Dehumidifier Works
Dehumidifiers are a key part of many commercial operations. If you need one, the Smart Family of Cooling Products experts can help with rental-ready desiccant dehumidifiers for sale. We’re also well-versed in the ins and outs of dehumidifiers and can conduct service on Smart Family Cooling equipment and dehumidifiers from other providers.
Contact us today to learn more about our dehumidifiers, aftermarket repair service or the dehumidification process in general!
