-What is a Centrifugal Blower?

-Centrifugal Blower Main Application

-How To Choose a Suitable Centrifugal Blower?

-Understanding Fan Performance Curves

-Calculating CFM of the Blower 

-Centrifugal Blower Discharge Position: Duct and Direction

-Conclusions

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Choosing the right centrifugal blower is critical to ensuring optimal performance of ventilation and air handling systems. Centrifugal blowers are widely used in various industries and places, including automotive, chemical, food processing, kitchen, boiler, UV dryer, agriculture, HVAC, mining, pharmaceuticals, and power generation.

As one of the leading centrifugal blower manufacturers in Taiwan, Air Deviser will discuss the factors that you need to consider when choosing a centrifugal blower. When it comes to choosing a centrifugal blower, it is crucial to understand what it is, its main applications, factors to consider when choosing one, understanding the fan performance curve and discharge position.

What is a Centrifugal Blower?

A centrifugal blower is a mechanical device that uses an impeller to generate airflow. It operates by drawing air into the center of the impeller and then expelling it outwards in a direction at an angle to the incoming fluid. Centrifugal blowers are suitable for specific directed cooling. There are four main types of them: forward-curved, backward-curved, radial, and airfoil.

Photo Source: See page for author, Public domain, via Wikimedia Commons

Centrifugal Blower Main Application

Centrifugal blowers have two main applications - exhaust and airflow.

● Exhaust

Centrifugal blowers remove air or gas from an enclosed space, such as a room or building. Therefore, they are commonly used for exhaust applications, where they are used to remove contaminants or exhaust gases from a specific area or building. In industrial settings, these fans are used to exhaust hazardous gases, fumes, or vapors generated during the manufacturing process.

● Airflow

Centrifugal blowers are also used for airflow applications, where they are used to move air from one location to another. In HVAC systems, these blowers are used to circulate air throughout a building, while in industrial settings, they are used for process ventilation. Air recirculation is a common requirement in numerous industries that use burners and boilers that produce energy and heat. For these industries, centrifugal blowers are essential for ensuring fresh air flows into the system and maintaining sufficient oxygen levels for proper fuel combustion.

How To Choose a Suitable Centrifugal Blower?

When choosing a centrifugal blower, several factors need to be considered. These include the airflow rate, blower static pressure, speed requirement, and intended fan duty. Let's take a look at these factors.

1. Air Flow

The airflow rate is the volume of air that the fan can move in a given amount of time. This is typically measured in cubic feet per minute (CFM) and is determined by the size of the space or system that needs to be ventilated. A blower with a higher CFM rating is required for larger spaces or systems.

To choose the right blower, you need to know the airflow requirements of your system. We will talk about how to calculate CFM later.

2. Static Pressure

Another important factor to consider when choosing a centrifugal blower is the blower static pressure. This is the amount of pressure that the blower needs to overcome to move air through the system. It is a pressure exerted in all directions in the space in which it is contained, not the direction of the air. High static pressure means that the blower can also air the inside of high-density mounting devices. It is measured in inches of water gauge (WG). To choose the right blower, you need to know the static pressure requirements of your system. This can be calculated by adding the pressure drops in the system.

3. Speed requirement

The required speed of the centrifugal blower is also an essential consideration. Higher speeds are needed for larger spaces or systems that require a higher CFM rate. Fan speed is typically measured in the number of revolutions per minute

 (RPM). It is important to choose a blower with the correct speed to ensure optimal performance.

4. Intended Fan Duty

Finally, you need to consider the intended duty of the centrifugal blower. Duty refers to the continuous operating conditions that the blower will be exposed to. This includes factors such as temperature, humidity, and the presence of corrosive or abrasive materials. Choosing a blower with the appropriate duty rating so it will perform optimally under the intended operating conditions.

Understanding Fan Performance Curves

A fan performance curve is a graph that shows the performance characteristics of a particular blower fan at various operating conditions. Fan performance curves play a key role in selecting the right blower for your application as they help you determine the airflow rate, pressure drop, power consumption, and overall efficiency of the blower.

The fan curve graph has three axes: the horizontal bottom axis represents the airflow volume rate in cubic feet per minute (CFM) or cubic meters per second (m3/sec.). The vertical left axis represents the fan's static pressure in inches water gauge (wg), pascals (Pa), or millimeters water gauge. Finally, the vertical right axis represents the fan's brake horsepower (BHP).

The intersection between the static pressure (SP) curve and the system curve on the static pressure vs. air volume curve is known as the fan operating point. This is the theoretical static pressure and air volume that your fan should provide for a particular duct system with workstations connected.

To obtain accurate fan curves, industrial fan manufacturers carry out tests to determine the static pressure values of the fans and blowers at various air flow volumes. If you require the information to draft your fan curves or want to learn more about the testing process, you can contact the manufacturer directly.

Calculating CFM of the Blower 

CFM = Air Velocity (ft/min) x Cross-Sectional Area (ft²)

1. Determine the blower's air velocity. You can measure it with an anemometer. Alternatively, you can consult the blower's specifications, which may provide the air velocity.

1. Calculate the cross-sectional area of the blower outlet in square feet. You can measure it by finding the diameter of the outlet and using the formula for the area of a circle (A=πr²).

2. Multiply the air velocity by the cross-sectional area. This will give you the blower's airflow rate in cubic feet per minute (CFM).

Centrifugal Blower Discharge Position: Duct and Direction

The direction of the discharge should also be considered to ensure that the air is moving in the right direction. The ideal discharge position depends on several factors, including the layout of the system, the type of application, and the space available for installation.

When determining the discharge position of a centrifugal blower, it is important to consider the direction of rotation, which is determined by the drive side of the blower. For single inlet blowers, the drive side is located on the opposite side of the fan inlet. For double inlet blowers with drives on both sides, the drive side should be located on the same side as the higher-powered drive unit.

It is suggested to consult the manufacturer's recommendations and guidelines when selecting the discharge position of a centrifugal blower to ensure optimal performance and efficiency.

▲Our Single outlet with double suction type furnace blowers’ 3-Sectional speed design provides different options to let the fan operate more efficiently.

Conclusions

Taken together, choosing the right centrifugal blower is crucial to ensure the optimal performance of ventilation and air handling systems.

Today we have learned how to choose a suitable centrifugal blower for your business. A centrifugal blower is an essential component in many industries such as the steel and glass industry, that require air or gas movement. Choosing the right blower requires careful consideration of several factors, including the airflow rate, blower static pressure, speed requirement, and intended fan duty. Fan performance curves are an essential tool for selecting the right blower, and the discharge position must be considered during installation. By selecting the appropriate centrifugal blower, you can ensure that it will perform optimally under the intended operating conditions.

Air Deviser Industrial is a Taiwan-based company that specializes in air blowers, Sirocco fans, centrifugal blowers, Sirocco fan wheels, and fan impellers. Our products are exported to the global market under our AD brand. We have factories in both China and Vietnam. With over 30 years of experience in the blower industry, we possess strong capabilities in R&D and OEM. We have developed a wide range of blower fans and fan wheels in various sizes to meet the needs of our customers.

Want to know more about centrifugal blowers? Still have questions regarding how to choose one? Contact us today to learn more about how we can help you achieve your business goals with our air blowers.