In certain cases, the term “test curves” is used to refer to fan performance tables, which are derived from data obtained from laboratory tests. A typical test curve will typically specify the performance characteristics for a certain design and size of fan, running at a given speed, and moving a gas with a defined density. This is because they are all operating at the same speed. This graph, upon closer inspection, will reveal that it is really made up of four distinct curves, which are as follows: • Curve of Static Pressure in Relation to Volume: This particular plot is the one that is sometimes referred to as the “fan curve” or the “characteristic curve” due to the fact that it outlines all of the probable pressure-volume combinations that the fan is capable of creating given the circumstances that are provided (i.e. rpm and gas density). As you can see, this curve is divided into two distinct regions: one is denoted by dashed lines, while the other is denoted by a solid line. When selecting fans, it is necessary to ensure that the design point is situated on a solid piece of the curve, ideally in a region that has a high level of operational efficiency. Because the dashed region of the curve represents a zone of possibly unstable performance, it is best to avoid performing operations on that area of the curve. For this reason, it is prudent to provide some room for reserve between the peak static pressure and the design pressure. This is done in order to compensate for a larger resistance to flow than what was predicted by the design calculation. • The relationship between static efficiency and the volume curve: In the majority of situations, it is preferable to have a fan function as near to its peak efficiency as is feasible. The static efficiency vs volume curve provides a quick and easy way to get an understanding of the efficiency of fan performance. • Power vs. Volume Curve: Showing the power draw of the fan at any position on the characteristic curve, this graphic displays the relationship between power and volume. The volume flow rate versus pressure characteristics of the system in which a fan will be placed are defined by the system curve, which is referred to as the system curve. A graphical representation of the performance of fans is known as the fan curve. During the process of selecting fans, it is definitely one of the most helpful instruments that can be used. Despite the fact that multi-rating tables are convenient, performance curves provide additional information such as the amount of reserve pressure head that exists between the design pressure and the peak static pressure, the maximum power that the fan is capable of drawing, and the efficiency with which it operates. The following equation, which is often referred to as the “duct law,” governs the connection between the volume flow rate and the pressure with respect to the majority of applications: Once the system designer has calculated the pressure loss (P) of the system for a certain flow rate (CFM), it is fairly simple to calculate the pressure loss that corresponds to any other flow rate by utilizing this “rule.” When the performance curve is supplied by the fan manufacturer, the system curve is not included on the curve, and the determination of the system curve is left up to the system designer. It is important to emphasize that a fan that is operating at a certain speed may have an unlimited number of operating points all over its characteristic curve. This is something that should be emphasized at this point in time. An operational point will be produced as a result of the fan’s interaction with the system, which will occur at the point where the fan curve and the system curve cross. It is important to keep in mind that the operating point on the fan curve will be determined by the system in which the fan is mounted. Therefore, it is of the utmost importance that the system designer precisely identify the system losses in order to guarantee that the actual air flow rate is as near as possible to the air flow rate that was designed. To get more information, kindly visit the website located at http://www.canadablower.com. Engineer of Heating, Ventilation, and Air Conditioning, Susan Terlitski canadablower@canadablower.com Website address: http://www.canadablower.com/air/index.html/ Canada Blower Company http://www.canadablower.com/enclosures/index.html
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