What functional segments should be included in the internal resistance of the air conditioning box?

The internal resistance of the air conditioning box should be calculated based on the actual air path. Common items include filters, coils, humidification or water retaining devices, muffler structures, internal air valves and transition air ducts. The list must be consistent with the selected configuration, and uninstalled functional segments cannot be included in the sample.

Correspond each loss to a functional segment

For filters, the initial resistance and post-use resistance must be determined for design consideration; for coils, the air volume and dry and wet conditions must be confirmed. The calculation boundaries of segmented resistance remain consistent to avoid counting the exit attachment both inside and outside the machine. The internal resistance data provided by the manufacturer should indicate the processing section and accessory range.

The filtration section should record the efficiency configuration, air volume and resistance state adopted; the heat exchange and wet section should record the actual configuration of coils, water retaining and humidification components; the internal air path includes related losses such as air valves, local diameter changes or turns. The three types of projects correspond to different functional segments, and we cannot just give a total resistance figure. Please refer to the caliber differences between external static pressure, full pressure and static pressure.What is the difference between static pressure, total pressure and static pressure outside the air conditioner box?。

The filter resistance should be distinguished between initial resistance and final resistance.

The filter resistance increases with the increase of dust accumulation, so the selection cannot be calculated based on the initial resistance alone. The initial resistance corresponds to the state of the new filter material, and the final resistance corresponds to the state when it needs to be replaced. The fan pressure budget usually needs to cover the final resistance. Filters with different efficiency levels and structures have different initial resistance and resistance changes after dust collection.

How to configure filter classification, please refer toHow to configure the primary-efficiency and medium-efficiency filters of air-conditioning boxes in different stages? . How to select the filter level according to the inlet air conditions, please refer toHow to select the air conditioning box filter grade based on the inlet air conditions? . Whether the high-efficiency filter is placed inside the machine or at the end will also affect the resistance range within the machine. Please refer toShould the high-efficiency filter of the air-conditioning box be placed inside the machine or at the end of the air supply?。

Coil and wet section resistance are related to working conditions

The air resistance of the coil changes with the number of rows, fin density, head wind speed and wet and dry conditions. There is a water film on the fin surface under wet conditions, and the resistance may be higher than that under dry conditions. Humidification sections, water baffles and water removal structures also increase local resistance. When selecting, the actual air volume and coil resistance data under working conditions should be obtained, rather than just estimating based on the number of rows.

How to select the type of surface cooler according to the air inlet and outlet conditions, please refer toHow to select the type of air conditioner cooler according to the air inlet and outlet conditions? . For the relationship between coil row number and cooling capacity, please refer toWill the greater the number of coil rows in an air-conditioning box, the greater the cooling capacity? . For the influence of wind speed facing the coil, please refer toWhat impact does the coil head-on wind speed have on heat exchange and water entrainment in the air conditioning box?。

Silencers, dampers and transitional air ducts are easily missed

Mufflers, internal dampers, reducers, elbows and outlet diffusers all create local resistance. These components are sometimes not prominently featured on the functional segment list, but make a real contribution to the total resistance. The list should be listed section by section by air path, indicating the name of the component and the source of air volume and resistance data.

How to determine the order of function segments, please refer toOn what basis should the sequence of functional sections of the air conditioning box be determined? . The length and internal structure of the mixing section will also affect the resistance, please refer toHow long is the air mixing distance required in the mixing section of the air conditioning box? . For the location of the filter section before and after the fan, please refer toWhat needs to be considered when arranging the filter section before and after the fan?。

Synchronously update the internal resistance after configuration changes

After increasing the filtration level, silencer section or changing the cross-section, the resistance within the original machine cannot be used directly. Even if the overall dimensions are the same, different processing units may result in different pressure requirements; the itemized list should be updated first, and then the fan operating point should be reviewed instead of directly increasing the motor power.

How to establish the fan pressure budget, please refer toHow is the total pressure of the air conditioning box fan determined by the internal resistance and external demand? . For the relationship between fan operating point and efficiency range, please refer toWhy should we check the efficiency range when selecting air-conditioning box fans? . When the total air volume is insufficient, check the measurement first or increase the speed first. Please refer toIf the total air volume of the air conditioning box is insufficient, should I check and measure it first or should I increase the speed first?。

Aili industrial supporting equipment

Aili Industrial can jointly check the configuration of the filter, fan and box, and describe the internal resistance range according to the confirmed functional segments to facilitate connection with the external requirements provided by the design. Aili's industrial manufacturing end covers independent R&D and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. The resistance data of the filter section, coil section, muffler section and fan section can be corresponded in the same set of supporting materials; non-standard functional sections can be adjusted according to the project air path.

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 resistance data, 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 the on-site air volume balance and pressure measurement results.

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Related questions and answers

Is it enough to count only the filter and coil for internal resistance?
not enough. Mufflers, air valves, reducers, elbows and water retaining structures will also produce resistance, which should be calculated segment by segment based on the actual air path.

Is filter resistance calculated based on initial resistance or final resistance?
The fan pressure budget usually needs to cover the final resistance. The initial resistance only corresponds to the state of the new filter material and cannot represent the later period of use.

Can Aili Industrial provide breakdown information on internal resistance?
Corresponding resistance data can be provided according to the confirmed function segments. The specific values ​​must be confirmed based on product configuration and on-site working conditions.

Related articles

1. What is the difference between static pressure, total pressure and static pressure outside the air conditioner box?

2. How is the total pressure of the air conditioning box fan determined by the internal resistance and external demand?

3. How to configure the primary-efficiency and medium-efficiency filters of air-conditioning boxes in different stages?

4. How to select the type of air conditioner cooler according to the air inlet and outlet conditions?

Key points for selection and acceptance inspection