How to determine the humidification amount of air-conditioning box according to the air inlet conditions in winter?

The humidification amount of the air-conditioning box should be calculated based on the difference between the dry air mass flow rate passing through the humidification section and the target and inlet moisture content, and the room humidity load and system division of labor should be checked. In winter, the outdoor relative humidity is high, and a large amount of humidification may be required because the absolute moisture content of the air is very low.

Use the moisture content first, then calculate the amount of water replenished per hour

When using mass balance, the humidification amount is the dry air mass flow multiplied by the moisture content increment. If the moisture content is expressed in g/kg, it should be converted into kg/kg first. For example, if the dry air flow rate is about 10,000 kg/h, an increase of 3 g/kg is required, and the theoretical humidification amount is about 30 kg/h. This example only illustrates the unit relationship and cannot replace the calculation of project conditions.

The inlet conditions should write the design temperature and humidity in winter and the actual air state before the humidification section; the target conditions should write the target moisture content, allowable fluctuations and air supply limits; the verification conditions should write the minimum air volume, the lower limit of equipment adjustment and the actual water vapor absorption conditions. Only when the three conditions are placed in the same working condition table can the calculation of humidification amount be closed. The difference between dehumidification capacity and cooling capacity can be referred toHow to calculate the dehumidification capacity of air conditioning box from the difference in air moisture content? , the humidification calculation also needs to be based on the moisture content difference.

High relative humidity does not mean high moisture content

Outdoor air temperatures are low in winter, and even if the relative humidity appears to be high, its absolute moisture content may still be low. The relative humidity will decrease after the air is heated, and if the moisture is not replenished, the room may be dry. Therefore, we cannot just look at the outdoor relative humidity to determine whether humidification is needed, nor can we directly calculate the amount of humidification using the relative humidity percentage.

For the relationship between moisture content and relative humidity, please refer toWhy does air conditioning box selection depend on relative humidity and temperature? . How to determine the value of the air inlet status in winter, please refer toShould the inlet air temperature and humidity of the air conditioning box be designed to be outdoor or return air? . When the proportion of fresh air is high, the humidification load in winter will also increase accordingly. Please refer toHow is the proportion of new return air to the air-conditioning box determined by project requirements?。

Humidification method affects usable conditions and maintenance

Steam humidification requires confirmation of steam supply or power supply, drainage and distribution methods; electrode type and electric heating humidifiers have different requirements for water quality, control range and maintenance methods. Just because the rated humidity production of the humidification equipment is sufficient does not mean that it can be absorbed by the airflow within a short distance. The position of the steam distribution pipe, absorption distance and air flow speed will all affect the actual effect.

For the difference between electrode type and electric heating humidifiers, please refer toWhat is the difference between electrode type and electric heating humidifiers used in air conditioning boxes? . For the positional relationship between the humidification section and adjacent functional sections, please refer toOn what basis should the sequence of functional sections of the air conditioning box be determined? . If the humidification section is close to a coil or filter, also make sure that water droplets cannot enter downstream components.

The humidification amount should also be checked with the room humidity load.

The calculated humidification amount is the moisture that needs to be supplemented by the air treatment in this section, and is not equal to the total humidity load of the room. Moisture dissipation from personnel, processes, penetration by opening doors, and introduction of fresh air all affect room humidity. If the goal is to control room humidity, the room moisture balance should be done first, and then determine how much humidification task the air-conditioning box will undertake. Confusing the humidification capacity of the unit with the humidity load of the room may lead to equipment selection that is too large or too small.

How the circulating air handling unit bears the indoor load can be referred toWhat indoor loads should the circulating air handling unit be selected based on? . For the relationship between supply air dew point and moisture control, please refer toWhat role does the supply air dew point play in the selection of fresh air air conditioning boxes?。

Low load and minimum air volume should be checked separately

During low-load operation in winter, the system air volume may decrease, and it needs to be checked whether the minimum output of the humidification equipment is adjustable. If the lower limit of humidification volume adjustment is too high, frequent starts and stops or humidity fluctuations may occur. The temperature and humidity measuring points before and after the humidification section should also be reasonably positioned to avoid local unabsorbed steam from affecting the readings.

After calculating the humidification volume, you should also check whether the fan, coil and control configuration can operate stably at the minimum air volume. For issues involving partial load regulation, please refer toWhy should we check the efficiency range when selecting air-conditioning box fans? . How to avoid local airflow at the sensor location, please refer toHow should the air supply temperature sensor of the air conditioning box avoid the influence of local airflow?。

Aili industrial supporting equipment

Providing the winter design status and minimum operating air volume to Aili Industrial helps to simultaneously check the humidification section size, control range and supporting interfaces. Aili Industrial can jointly check the humidification section, coil, filter and control configuration; the manufacturing end covers the independent research and development and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. The interfaces between the humidification section and the front and rear functional sections can be aligned in the same set of packages, and non-standard humidification sections can be adjusted according to on-site space.

Product form can be viewedAir handling unit andFan box page; clean air supply package can be combinedFFU fan filter unit andEFU equipment end fan filter unit verification; terminal particle filtration can be combinedHEPA/ULPA filter confirmation; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. The specific humidification effect, applicable conditions and delivery scope still need to be verified based on the corresponding configuration data and on-site working conditions. The actual effect is subject to on-site debugging and performance test results.

Submit project parameters:https://ailigy.com/contactus.html

Related questions and answers

The relative humidity outside is high in winter. Do we still need humidification?
May be required. When the outdoor temperature is low, the absolute moisture content may be very low. After the air is heated, the relative humidity decreases, and the humidification amount still needs to be calculated based on the moisture content difference.

Can the humidification amount be calculated directly by subtracting the relative humidity?
cannot. Relative humidity is a proportional value. The calculation of humidification requires the difference in moisture content. The moisture content is expressed in terms of the mass of water vapor per kilogram of dry air.

Can Aili Industrial help check the humidification configuration?
The humidification section and control configuration can be checked based on the winter air inlet status, minimum air volume and humidification method. The specific plan needs to be confirmed based on the project conditions.

Related articles

1. How to calculate the dehumidification capacity of air conditioning box from the difference in air moisture content?

2. Why do we need to consider the temperature when selecting an air-conditioning box based on relative humidity?

3. What is the difference between electrode type and electric heating humidifiers used in air conditioning boxes?

4. On what basis should the sequence of functional sections of the air conditioning box be determined?

Key points for selection and acceptance inspection