What Is an Axial Flow Fan?
An axial flow fan is an AC-powered fan used to cool equipment.
It is used to exhaust heat generated inside the equipment to the outside and, conversely, to supply air to the inside from ambient heat outside the equipment. Its main role is to control the temperature inside the equipment.
If the heat treatment of electronic components that generate heat by operating or driving equipment is left unchecked, the electronic components inside the equipment may fail or be damaged in the worst case scenario. Axial flow fans are used to supply and exhaust air from the heat generated in the equipment.
Uses of Axial Flow Fans
The main applications for axial flow fans include control panels, measuring equipment, office automation equipment, communications equipment, power supply equipment, medical and scientific equipment, amusement equipment, and industrial equipment. They are also used for ventilation and cooling of capacitors and IC electronic components in equipment such as vending machines and refrigerated showcases. The purpose of all of these applications is to ensure the long-term use of equipment.
Principle of Axial Flow Fans
A typical axial flow fan consists of a bladed plastic or metal cooling fan attached to a motor driven by an AC power source. Air is drawn in from the front of the fan and exhausted out the back to cool the inside of the equipment. Conversely, some fans intake air from the rear of the fan and exhaust air from the front.
Axial fans are fans in which the direction of airflow with the fan is in the axial direction. They are the most efficient of all turbofans and are widely used for cooling applications of heating elements. Relatively little increase or decrease in airflow due to resistive objects is a characteristic of axial fans. When axial fans are installed in equipment, the noise and power consumption of the equipment can be reduced by setting the operating point of the fan to the maximum airflow side.
The most important factor in fan performance is the required airflow relative to the amount of heat generated by the cooling target. To accommodate cooling by fans in various environments, parallel or series operation of fans, large types, or double-reversing fans may be used to obtain the required air volume.
How to Select an Axial Flow Fan
When selecting an axial flow fan, first estimate the amount of heat generated in the equipment, W. The heating value can be calculated by converting the power consumption of the equipment into heat value. Then, the allowable temperature rise value ΔT in the equipment is determined as the difference between the allowable temperature of the equipment and the maximum suction temperature of the fan. Next, the required air volume Q to satisfy the allowable temperature rise value ΔT is calculated.
The system resistance is also estimated based on the ventilation resistance in the equipment or historical data. Finally, the pressure P-airflow Q characteristic of the axial fan is used to select a fan. If it is difficult to estimate the ventilation resistance, the fan is selected so that the maximum airflow is 1.3 to 2 times the required airflow.
On the other hand, the use of a fan may cause dust and other particles to flow into the equipment to be cooled for a long period of time, which may lead to failure or damage of electronic components. In this case, a filter on the intake side in front of the fan can prevent dust and foreign matter from flowing into the equipment. This ventilation resistance must be added.
Other Information on Axial Flow Fans
1. AC Fan Motor
AC fan motors are motors driven by AC voltage. AC fan motors are composed of a stator and a rotor, and the change in the magnetic field generated when current is applied to the stator generates eddy currents in the rotor to generate power.
AC fan motors come in two types of AC power sources: single-phase and three-phase. AC motors do not normally run on single-phase alone. Therefore, single-phase AC fan motors use a built-in capacitor to advance the phase or a structure called shading. Also, motors with three-phase power supply have three different phases, so they can move if the power supply is applied as it is, and are also called induction motors.
Unlike DC fan motors, which have rotational speed control, the rotational speed of the blades is generally fixed according to the frequency of the AC power supply. There are also special ACDC fan motors that have the ability to convert AC to DC.
2. Difference Between Axial Flow Fan and DC Axial Flow Fan
The difference between an axial flow fan and a DC axial flow fan is the power source that drives the fan motor; a DC axial flow fan is a DC-powered fan. On the other hand, an axial flow fan is a fan that is driven by an AC power source.
The frequency of the AC power supply causes the fan to rotate at a constant speed, whereas the DC axial fan can change its rotation speed depending on the motor circuitry.