Axial Fans: The Basics

Cooling Tower Fans

Comments (0) June 8, 2017 /

Do You Know Your Cooling Tower Fans?

Heat is an interesting thing. On the one hand, heat can be a great thing. It keeps us warm when it is cold, has allowed us to industrialize more than our ancestors could have ever imagined, and is generally the hallmark of an advanced society. On the other hand, heat can be rather detrimental to certain processes. For many industrial applications, heat can not only cause a decrease in productivity but, if left unaddressed, can actually cause major issues. Luckily, we as a society have developed effective means to get rid of unwanted heat and, in today’s post, we are going to go over one of the components that is essential for the mitigation of heat in industrial applications: axial fans. Continue reading below to learn more.

The Axial Fan is Important

To talk about axial fans, it is important to first understand exactly what an axial fan is. In the simplest of terms, an axial fan moves air parallel to its axis of rotation. This makes axial fans ideal for low-resistance, high-flow applications such as those needed in industrial cooling applications. Additionally, axial fans are able to have a wide range of operating characteristics depending upon the shape and width of the individual fan blades. In addition to these factors, other variables can affect the effectiveness of fan blade efficiency. Below, we have listed a few more of these variables.

  • Tip Clearance: Although the average person is not really aware of this fact, the amount of tip clearance that a fan blade has in a cooling tower housing can have a huge effect on the efficiency of the entire tower. The amount of clearance has such an effect because it affects the amount of air loss or leakage around the tip, known as the tip vortex. As the air exits the cooling tower, it will be at a higher pressure than the incoming air due to the work exerted by the fan blades. The less clearance there is around the tip of the fan blades, the less likely it is that the air within the cooling tower will be able to slip around the fan.
  • Inlet Conditions: When considering the effectiveness of the axial fan within a cooling tower, it is important to consider the effect of airflow as it enters the tower. In the area around the fan blade, known as the fan ring, air must be collected from all directions and equally accelerated to the velocity at the plane of the fan. If a smooth transition is not achieved, the inability of the airflow vectors to make the appropriate, rapid changes in directions will cause a “Vena Contracta” at the blade tip. Basically, this area of the fan blade will become starved for air, rendering the area near the tip of the blade ineffective. Considering the majority of the work is done on the outer portion of the fan blade, if this issue is not addressed, there can be a loss of efficiency as high as 15 to 20 percent.
  • Air Density: A factor that many people fail to consider in relation to the efficiency of their cooling tower fans is the effect of air density within a given environment. The density of air is affected by air temperature and altitude at the plane of the fan and can, if not accounted for, can have a serious impact on the effectiveness of a cooling tower. Look at it this way, a cooling tower at sea level is going to have to exert a lot more force than a cooling tower at 5,000 feet above sea level because the air density at sea level is much higher. To account for this difference in air density, it is important to adjust the rotational speed of a fan to make sure that the proper volume of air is being pushed through the tower.

We hope that this short blog has helped you gain a better understanding of the variables that can impact the effectiveness of cooling tower fan performance. If you would like to learn more about the cooling tower fan options that we offer or you would like to schedule a maintenance check with one of our cooling tower technicians, contact us today and set up an appointment. At Industrial Cooling Solutions Inc., we are dedicated to providing the best in industrial cooling tower solutions, and we are certain that we can help you with any need that you may have. Contact us today and let’s get started!

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