How do the backward-inclined and forward-inclined fans compare when used in air conditioning boxes?

When backward-inclined and forward-inclined fans are used in air-conditioning boxes, the performance, power and maintenance conditions should be compared under the same air volume, pressure, space and noise requirements. The impeller form can help understand product characteristics, but it cannot be concluded that a certain fan must be more energy-saving or quieter just by 'backward tilt' or 'forward tilt'.

Put at least four actual results in the comparison table

Check the design point input power, available speed range, complete machine installation dimensions and acoustic data, and confirm whether the pressure is the full pressure of the fan or the static pressure outside the equipment. Different impeller diameters and drive modes will change the comparison results. One large-sized low-speed fan and another model with limited space cannot be simply attributed to the blade direction.

The performance should be compared with the power and operating range under the same air volume and pressure caliber; the structure should be compared with the impeller diameter, drive arrangement, maintenance and cleaning accessibility; and the acoustics should be compared with the sound power or corresponding test data under the same measurement boundary. If the three items are placed in the same table, the difference in impeller form is meaningful. How to check the fan efficiency range, please refer toWhy should we check the efficiency range when selecting air-conditioning box fans?。

Differences in aerodynamic characteristics of the two impellers

The backward-inclined impeller blades are bent backwards, and the airflow accelerates more slowly in the blade passage. It usually has better efficiency performance in the range of higher wind pressure and larger air volume, but the impeller diameter and box space requirements may be larger. The forward-inclined impeller blades are curved forward, with a compact structure and a large downwind volume of the same size, but the efficiency curve and noise characteristics are different from those of the backward-inclined impeller.

These characteristics are general trends, not absolute conclusions. The impeller angle, number of blades, diameter and speed of the specific model will change actual performance. There is a lack of model-level basis for directly equating 'leaning back' with high efficiency, or directly equating 'leaning forward' with low noise. 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?。

Cabinet space and installation conditions will change the conclusion

If the entrance of the unit is blocked, the exit is in a sharp bend, or the installation distance is insufficient, the working point of the entire unit may be shifted. When the diameter of the backward-inclined impeller is larger, the height of the box and the maintenance space requirements increase; the forward-inclined impeller has a compact structure and may be more suitable for units with limited space. But compact construction can also bring maintenance and cleaning limitations.

The comparison should use the same air density, accessories and measurement boundaries, and differentiate between fan aerodynamic efficiency, motor efficiency and total input power. The structural form of the fan box can be referred toOn the fan box page, please refer to the sequence relationship between the filter section and the fan.What needs to be considered when arranging the filter section before and after the fan?。

Noise comparison should be performed under the same measurement boundary

The noise spectrum characteristics of the backward-leaning type and the forward-leaning type may be different. When the total A-weighted value is close, the sub-band performance may still be different. When comparing, it should be confirmed that the measuring point distance, acoustic environment, operating conditions and weighting method are consistent. For the difference between sound power level and sound pressure level, please refer toHow to distinguish the sound power level and sound pressure level of air conditioning box?。

If the project has clear requirements for noise, the equipment acoustic data and propagation path should be checked together. You can refer toWhat noise propagation paths should we pay attention to when selecting an air-conditioning box? . The on-site noise level cannot be judged solely by the impeller form.

The driving mode and speed adjustment range should also be compared together.

Both backward-tilting and forward-tilting types can use direct-coupled DC drive or belt drive. The drive method will affect efficiency, maintenance and speed regulation characteristics. The regulation characteristics of DC fans under partial load are different from those of AC fans. When comparing, you should confirm that the motor type, speed range and controller match.

For the driving conditions of DC fans, please refer toWhat driving conditions need to be matched when using a DC fan in an air-conditioning box? . How to calculate fan energy consumption by operating period, please refer toHow to calculate the energy consumption of air conditioning box fans separately according to operating periods? . Annual energy consumption cannot be estimated only based on rated power, please refer toWhy can’t the annual energy consumption of air conditioning boxes be estimated based on rated power alone?。

The choice of impeller should also be subject to the layout of the box

The inlet, outlet and return space of the unit will affect the performance of the fan. After selecting the form, you also need to check the motor load, support, vibration reduction and maintenance paths. If the project already has a restricted size, dimensional drawings should be submitted first and then compared with candidates that can be actually installed, rather than locking the impeller form first and then compressing the necessary space.

Whether the length of the cabinet can be compressed when the space of the cabinet is limited, please refer toCan the length of the horizontal air conditioning box be reduced when there is insufficient plane space? . For installation space and horizontal and vertical selection, please refer toWhat kind of space do horizontal air-conditioning boxes and vertical air-conditioning boxes require?。

Aili industrial supporting equipment

Aili Industrial can check candidate solutions based on the matching conditions of fans, motors and casings; the comparison table should retain specific working conditions to avoid purchasing based solely on type names. Aili Industrial has motor manufacturing and independent fan R&D and production capabilities. It can match the fan form according to the target air volume, internal resistance, external static pressure and speed regulation requirements during the selection stage. The manufacturing end covers independent R&D and production of motors and fans, control systems, sheet metal, air filters and complete machine assembly. The impeller form, drive layout and box interface can be checked in the same package.

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; multiple equipment linkage can understandMatching method of FFU computer group control system ; terminal particle filtering can be combinedHEPA/ULPA filter confirmation; when it comes to gaseous pollution control, you can communicate separatelyChemical filter solutions. The specific fan performance, 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 air volume balance and performance test results.

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

Related questions and answers

Are backward-tilting fans more energy efficient than forward-tilting fans?
uncertain. Whether it saves power or not depends on the actual input power and operating point under the same air volume and pressure. The impeller form is only a feature.

Are forward-tilting fans suitable for air conditioning boxes with limited space?
The structure may be more compact, but the air volume, pressure, noise and maintenance space still need to be checked, and cannot be judged based on the impeller form alone.

Can Aili Industrial help compare fan models?
Candidate plans can be checked based on the target air volume, pressure, space and noise requirements. The specific configuration needs to be confirmed based on the project conditions.

Related articles

1. Why should we check the efficiency range when selecting air-conditioning box fans?

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

3. How to distinguish the sound power level and sound pressure level of air conditioning box?

4. What driving conditions need to be matched when using a DC fan in an air-conditioning box?

Key points for selection and acceptance inspection