What is meant by relative and absolute humidity in the industrial dehumidification process?

Air humidity is an important measure to consider in various contexts, including industry, agriculture, and construction.

To fully understand the role of air humidity, it is essential to make clear distinctions between relative humidity and absolute humidity.

What is meant by absolute and relative humidity?

Absolute humidity (AH) refers to the actual amount of water vapor present in the air, measured in grams per cubic meter (g/m³).

This parameter provides specific information about the actual quantity of water in the air, regardless of its capacity to hold moisture.

Absolute humidity can vary significantly based on climatic and environmental conditions.

Relative humidity (RH) represents the amount of water vapor present in the air compared to the maximum amount it could hold at a given temperature and pressure.

It’s expressed as a percentage and can range from 0% (completely dry air) to 100% (fully saturated air).

For example, a relative humidity of 50% indicates that the air contains half the water vapor it could hold at that particular temperature.

Does air humidity also affect the industrial dehumidification process?

Now that we have learned this basic information, we can then focus on the importance of air humidity in industrial production.

Air humidity plays a fundamental role in specific industrial production processes.

In many manufacturing environments, high humidity can cause problems such as condensation, mold and bacterial growth, material corrosion, and deterioration of moisture-sensitive goods.

Industrial dehumidification is necessary to maintain environmental conditions at an acceptable level, and the process is generally performed using devices called dehumidifiers.

They remove excess moisture from the air, thereby reducing the relative humidity to the desired level, depending on the specific case.

There are various types of dehumidifiers, that are used in industries, including:

• Refrigeration dehumidifiers

They are the most common and they work by passing the air through a chilled coil where the water vapor condenses and is collected. The dehumidified air is then heated and returned to the environment. This process reduces both the relative humidity and the absolute moisture content of the treated air.

• Desiccant dehumidifiers

They use absorbent materials such as silica gel to capture moisture from the air. Once the absorbent material reaches its maximum capacity, it is regenerated through heating or exposure to hot air currents. This allows the removal of accumulated moisture and restores the absorbent material’s capacity.

• Adsorption dehumidifiers

They use porous materials that selectively absorb water vapor from the air. The material is then heated or exposed to low pressure to remove the moisture. This process is particularly effective in environments with extremely high humidity.

• Chemical dehumidifiers

They utilize chemical reactions to remove moisture from the air using deliquescent or desiccant products. Unlike other dehumidifiers, chemical dehumidifiers require the replacement or regeneration of the chemical products to continue functioning efficiently.

How to measure the moisture content of the air?

The measurement of air humidity is carried out using an instrument called a hygrometer.

There are different types of hygrometers, but the two most common ones are:

• Hair hygrometer: It utilizes the property of hair or certain animal hairs to expand or contract in response to changes in humidity. Human hair, when exposed to relative humidity between 2.5% and 100%, undergoes elongation. As humidity increases, the hair expands, while it contracts when humidity decreases. This variation is then transmitted to an indicator or measurement system, providing the reading of relative humidity.
• Electronic hygrometer: It uses electronic sensors to detect humidity. These sensors measure electrical conductivity or other physical properties that vary depending on the amount of moisture in the air. The collected data is then converted into a reading of relative humidity.

So, now we know how to measure the moisture content of the air and also we know that it’s really important to have an industrial dehumidification system, but specifically what to do if you work with plastic materials?

Air humidity and plastic materials production

Accurate measurement of air humidity is essential in many sectors, including industry, and can be performed using different types of hygrometers.

Air humidity can significantly influence production processes and industrial dehumidification aims to reduce its magnitude (both relative and absolute humidity) to maintain suitable environmental conditions and prevent issues caused by excessive moisture.

Vismec industrial dehumidifiers, for example, allow for safe and continuous control and regulation of air humidity over time, calibrating relative humidity, absolute humidity, dew point, and vapor pressure deficit.

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