Choosing the right cooling fanJanuary 26, 2021
Heat buildup can be a major issue, resulting in reduced performance, premature deterioration and very real safety concerns.
That is why it is vital to choose a cooling fan that matches the very specific needs of an operation, from initial thermal analysis to performance factors.
“How to Select a Cooling Fan,” will outline how to choose a cooling solution that fits operational and budget needs for the best possible results. This eBook will discuss how to:
- Calculate critical data points to find the best solution
- Select a single fan or blower that best fits an application’s needs
- Evaluate factors like performance curve, speed control and fan maintenance
- Start the troubleshooting process
In the manufacture of most parts and components, or their subsequent assemblies, the dissipation of heat is a major consideration. Heat buildup can result in reduced performance of equipment and processes, in premature deterioration of components and lubricants, and can raise safety considerations for operating personnel and end users. Cooling fans are often used to dissipate heat buildup. When selecting the right fan for any operation, a thorough selection process is critical to their successful operation and ultimate ability to deal with heat. The first step in this process is a thermal analysis.
The point of a thermal analysis is to determine the amount of heat generated inside a piece of equipment or during a process so the volume of air required to cool a system can be computed.
Temperature, thermal resistance and heat dissipation will all help to dictate the airflow that is necessary to cool the system. This process is begun by investigating the origin of the heat and measuring the amount of heat emanating from each source using sensors and other devices. Surface temperatures are typically measured using one or a combination of six different types of sensors: thermocouples, resistive temperature devices, infrared radiator or sensors, bimetallic devices, fluid or liquid expansion devices, and change-of-state sensors. Data delivered from these sensors can indicate where heat problems exist while helping to map the necessary airflow to provide cooling.
The next step in the cooling fan selection process is to determine the system impedance. As air travels between fan inlet vents and exhaust vents, the air pressure will drop. System impedance is simply the sum of this pressure drop. In the event of multiple air paths, individual impedances are totaled. Alternatively, air chambers can be used to create a model system to make these impedance calculations. Once system impedance as well as overall airflow requirements have been identified, the system’s static pressure at the required airflow can be gauged.
Fan or blower?
Once these critical data points have been calculated, it is time to decide what equipment will deliver the best solution: a fan or a blower. Fans and blowers differ primarily in their flow and pressure characteristics. Fans, which tend to work against low pressure, deliver high flow rates of air parallel to the fan blade axis. When blowers deliver air, it is perpendicular to the blower axis, at lower flow rates, but against high pressure. Blowers can generate much higher pressures than fans but are typically noisier.
Fan characteristics are best represented as a fan curve, which is a performance curve for any particular fan under specific conditions. The fan curve, which graphically represents a number of inter-related parameters, is developed for a given group of conditions, including fan volume, system static pressure, fan speed and brake horsepower necessary to drive the fan under conditions in a particular application.
Bearing assemblies in fans and blowers predispose them to failure, so their operation should be carefully monitored. Failure monitoring circuits can be used to track performance and potential malfunctions in advance. Some of these fan performance monitoring circuits even include thermal shutdowns that will cut the power if overheating is detected.
All operating systems require maintenance, and cooling fans are no exception. Using either hours of operation or calendar period, devise a basic maintenance schedule that is also based on manufacturer recommendations and experience with fans in similar applications.
Additional information about Pelonis cooling fans and blowers can be found at Pelonis Technologies.