Nem Kontrol Teknolojileri: Verimli Bir Endüstriyel Nem Alma Cihazı Nasıl Seçilir?style="text-align: justify;">Humidity is an effective factor in many environments, from living spaces to industrial facilities. Maintaining optimal humidity levels is critically important for comfort, health, and process efficiency. As NKT Academy, we will cover in detail how to calculate the humidity load in an enclosed control volume in this article.What is Humidity?
Humidity refers to the amount of water vapor present in the air. Water molecules in the atmosphere evaporate from various sources and mix with the air, creating humidity levels. Humidity varies depending on air temperature, pressure, and environmental conditions, and is generally expressed as a percentage (%) in weather reports.
Relative Humidity?
Relative humidity expresses the ratio of the amount of water vapor in the air to the maximum amount of water vapor that the air can hold at that temperature, in percentage terms. In other words, relative humidity indicates "how moist" the air is.
How Does Relative Humidity Work?
Air can hold more water vapor as temperature increases. Therefore, for the same amount of water vapor, as air temperature rises, the relative humidity decreases; when temperature drops, relative humidity increases.
When relative humidity reaches 100%, the air has reached the maximum amount of water vapor it can hold at that temperature. At this point, the air can no longer hold water vapor, and the water vapor transforms into water and condenses as dew. This point is called the "dew point."
The dew point refers to the temperature at which water vapor in the air begins to condense, transforming into water droplets. Dew point and relative humidity are two important thermodynamic terms used together to understand the amount of moisture in the air. These two concepts are closely related and should be considered together in process calculations.
Absolute Humidity
Absolute humidity refers to the actual amount of water vapor within a specific volume of air. It is typically measured in grams per cubic meter (g/m³) or grams per kilogram (g/kg) with density. Absolute humidity directly indicates the amount of water vapor in the air and is not dependent on temperature.
Example: Let us assume we are working in an enclosed control volume of 100 m³. If there is a total of 200 grams of water vapor in the air within this space, the absolute humidity will be 200 g/ 100 m³= 2 g/m³.
In this case, the absolute humidity in that room is 2 g/m³, and this value does not change regardless of the room temperature. However, if you increase the room temperature, the air can hold more water vapor, which may lower the relative humidity. If you decrease the room temperature, the air can hold less water vapor, which may increase the relative humidity.
So absolute humidity expresses a fixed amount of water vapor in the air, and this amount is not affected by temperature changes. Relative humidity, on the other hand, changes depending on temperature and is a percentage expression of the air's moisture capacity. Absolute humidity can be expressed as g/m³ or g/kg.
What is Humidity Load?
Humidity load refers to the total amount of moisture entering and remaining in a specific area. This amount is generally expressed in kilograms of water vapor. Humidity load is an important factor in the design of heating, ventilation, and air conditioning (HVAC) systems, sizing of humidity control systems, capacity selection of dehumidifiers, and improvement of indoor air quality.
The first step is to identify the moisture sources in the area. Humidity load can come from people, plants, fresh air sources, cleaning activities, process steam, or industrial processes.
- People and Animals: They produce moisture through respiration and perspiration.
- Plants: They produce water vapor through transpiration.
- Water Usage: Activities such as process steam, floor washing in industrial areas, and mandatory water use in the process itself.
- Industrial Processes: Moisture is produced during certain manufacturing processes.
- Construction Materials: Materials used during new construction or renovations can contain moisture.
- Fresh Air: When air from outside that is more humid enters the control volume where humidity control is being performed, the fresh air moisture load must be considered.
Calculating Moisture Production Amounts:
The hourly or daily moisture production amounts of each moisture source should be calculated. This data can be obtained from literature or determined through experiments and observation.
Human: People release moisture into their surroundings through respiration and perspiration at 20-25°C temperature:
- High-intensity work: 200 grams per hour,
- Medium-intensity work: 125 grams per hour,
- Low-intensity work: 60 grams per hour.
When starting a humidity control design, the moisture load equal to the number of people in the relevant control volume must be included in calculations.
Humidity of the Control Volume:
Calculating the humidity load in an enclosed volume is important for achieving targeted humidity control, removing moisture from the room, and optimizing humidity levels. Follow the steps below to calculate the humidity load in an enclosed volume.
Calculate the volume: First, find the volume of the area where you will perform the calculation. This can be calculated with the formula: length x width x height. For example, for a room measuring 10m x 5m x 2m, the volume will be 100 cubic meters.
Volume (m³)= length (m) × width (m) × height (m)
Determine the absolute humidity level: You can use a hygrometer or moisture meter to measure the absolute humidity level. Absolute humidity is generally expressed in grams per cubic meter (g/m³).
Calculate the humidity load: To calculate the humidity load, multiply the absolute humidity level (g/m³) by the volume (m³).
Humidity Load (g)= absolute humidity (g/m³) × volume (m³)
Example: There are 4 people working at high activity in a room with a volume of 100 m³ and an absolute humidity level of 8 g/m³. We can calculate the humidity load as follows:
Humidity load of air in the volume (g)= 8 g/m³ × 100 m³= 800 g
Humidity load from people (g)= 200 g × 4= 800 g
The total humidity load is found by adding up the production amounts of all moisture sources.
800 (g) + 800 (g)= 1,600 (g)
The difference between the target absolute humidity value and the absolute humidity value in the enclosed control volume is multiplied by the control volume and the density of air at the relevant temperature to find the dehumidifier capacity to be discharged. The resulting capacity plays an active role in dehumidifier selection. Dehumidifier capacities must be selected to meet the total humidity load at the target temperature and relative humidity values.
System Sizing According to Humidity Load
Our expert sales team at NKT – Humidity Control Technologies is always happy to provide information regarding the calculation of alternative humidity loads and dehumidifiers. With total humidity load information, you can properly size humidity control systems (dehumidifiers, humidifiers, HVAC systems, etc.). Proper engineering work increases energy efficiency and ensures sustainability in the process.
Avoiding Common Mistakes
The most important factor to consider during humidity load calculation is accuracy in the data collection and calculation stages. Correctly identifying sources and production amounts is essential for obtaining precise and reliable results.
This guide provides a general framework for understanding and calculating humidity load. It is important to consider the unique needs and characteristics of each project to achieve optimal results.
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