Ventilation of buildings and houses and temperature control are the most important functions of HVAC, and they are also an indispensable system in industry and life.
Therefore, it is very important to choose a suitable HVAC fan for HVAC, which seriously affects the subsequent installation, maintenance and use costs.
As a professional HVAC fan manufacturer, this article will introduce you to:
Hope it helps you.
What is an HVAC system?
HVAC stands for Heating, Ventilation and Air Conditioning. HVAC refers to the different systems used to move air between indoor and outdoor areas, as well as the heating and cooling of residential and commercial buildings. They are systems that keep you warm and comfortable in winter and cool and fresh in summer. They are also systems that filter and clean indoor air, keeping you healthy and keeping humidity levels at optimum comfort levels.
Common HVAC Fans for HVAC Systems
-
Axial Fan
Axial fans have the simplest structure, with blades arranged in a propeller shape around the axis of rotation. These fans are designed for applications where both airflow and static pressure are relatively low.
Axial fans are generally the lowest cost of the three types described in this article, but keep in mind that they are not suitable for applications with airflow resistance (high static pressure).
Some common applications for axial fans include cooling towers, outdoor air conditioner condensers, electronic component cooling, and internal combustion engine cooling. All of these devices require airflow to release heat, but have little or no resistance to air flow, so low-cost axial fans can be used.
-
Centrifugal fan
Centrifugal fans are classified by their radial, forward-curved, or backward-sloping blade shapes, which increase the speed of the airflow by rotating the impeller. As the air reaches the tip of the blade, the velocity increases, which is then converted into pressure. These fans are capable of generating high pressure, which makes them suitable for harsh operating conditions, such as systems with high temperatures or humid or dirty airflow. Tip vortex or tip leakage flow created by differential pressure across the airfoil section can be a problem for these basic fans.
Forward-curved centrifugal fan, which looks more like a hamster wheel, can generate more air pressure. Because of this, they tend to be noisier than axial fans and require more power to run. They are durable, easy to clean and maintain, and have fewer drag issues. Forward curved centrifugal fans are also known as blowers.
Backward-curved centrifugal fans are uncommon blades that can be curved or straight, making these fans ideal for high flow and variable resistance. They are usually used for industrial purposes.
These fans are commonly used in industrial applications with high airflow and variable resistance, such as dust collection, incineration systems, process cooling, and glass tempering. In commercial HVAC systems, backward-sloping fans are often used for energy recovery ventilation (ERV).
HVAC fan selection elements
HVAC fans and blowers come in two styles and three grades. The two styles are forced ventilation and induced ventilation.
Forced ventilation refers to the movement of air under pressure. Forced-air fans and blowers are so named because they "force" air to move.
Induced ventilation refers to the movement of air by inducing a partial vacuum. Induced fans and blowers "draw in" air.
The AMCA class for HVAC fans and blowers describes the equipment's compliance with Air Movement and Control Association (AMCA) requirements.
Depending on the application, 4 parameters need to be determined:
-
Fan type
Fans all perform the basic function of moving air from one space to another. But the huge variety of fan applications has led manufacturers to develop many different models. Each type and model is beneficial for certain applications, providing the most economical way to perform air flow functions.
-
Air volume flow (CFM)
Once the fan type is known, the airflow must be determined. Your local building code should contain information on recommended air changes for proper ventilation. Use the following formula to calculate the CFM required to adequately ventilate an area.
Room Volume = LxWxH CFM = Room Volume ÷ Min/Variation
-
Static pressure
Accurately measuring static pressure is critical for proper fan selection. Fan static pressure is measured in inches. One pound per square inch is equivalent to 27.7 inches of SP. Static pressure in a fan system is typically less than 2” SP or 0.072 Psi.
The amount of static pressure that the fan must overcome depends on the air velocity in the duct system, the number of duct turns (and other resistance elements), and the duct length. For properly designed systems with sufficient makeup air, the guidelines in the table below can be used to estimate static pressure.
-
Sound (Noise)
The sound produced by the fan must be considered. For the fan industry, the common unit for expressing sound pressure level is Sones.
As a general guideline, choose a fan that is rated within the specified range.
Selection of HVAC Fans and Blowers
The following types of fans are used in HVAC systems.
Axial Fan
In this type of fan, the blades are mounted parallel to the direction of the rotor axis. In HVAC systems, axial fans are used for cooling or dilution ventilation. These can be AC/DC powered.
Two types of fans are selectively used in HVAC systems.
-
Tubular Axial Fans
In these fans, the fan blades are enclosed in the duct from the outer tip. This creates a consistent airflow. These fans are used for consistent cooling and even air output.
-
Bladed Axial Fans
These fans consist of blades/pockets between the blades. This helps direct airflow without creating swirling motion. These fans are ideal for variable flow cooling and ventilation applications.
Centrifugal Fan
A centrifugal fan consists of blades aligned at 90° to the rotor axis. The construction of these fans is similar to a hamster wheel. These fans are suitable for generating large volumes of air for cooling and ventilation applications. These fans utilize centrifugal action to increase air volume and provide high pressure, high volume air output.
The output of the centrifugal fan varies according to the design. The following are popular designs of centrifugal fans used in HVAC systems.
-
Forward curved centrifugal fan
The forward curved design provides high pressure air output. The tips of the blades of these fans are curved forward, thus providing moderate air volume at high pressure.
-
Back curved centrifugal fan
A backward-curved fan has blades that are straightened or slightly curved back. These fans consume low power and produce less noise. These fans can be used when a lot of air is required and the power is relatively low. The most common application of these fans in HAVC systems is Energy Recovery Ventilation (ERV).
-
Airfoil centrifugal fan
Airfoil centrifugal fans have sloping blades that form an airfoil structure. The inclination of these blades is set according to Bernoulli's principle. These fans can generate high-speed air output without creating a vortex. These fans operate silently and are suitable for HVAC systems with active ventilation requirements.
NOTE: One or more of the above fans can be used for a ventilation system. However, choosing a fan for a specific HVAC operation requires consideration of factors such as required air volume, pressure, temperature, air circulation capacity, energy consumption, and more.
Conclusion
For best results and performance, be sure to ask your HVAC engineer or HVAC fan manufacturer for advice. HVAC systems not only affect the power consumption of the fans, but also the heating and cooling loads.
If you are looking for the right products to start your HVAC or other business, then welcome to contact us. Langdi is a leading HVAC fan and ventilation system fan manufacturer in China, favored by many domestic and foreign manufacturers, and can provide you with high-quality centrifugal fans and axial fans and other related products.
