Pump curve speed calculator affinity law calculator. Changes in diameter d diameter, in or mm q flow, gpm or m 3 h h head, ft or m p power, hp or kw. Download a complete calculation example in pdf format. The affinity laws of centrifugal pumps or fans indicates the influence on volume capacity, head pressure andor power consumption of a pump or fan due to. Why can we consider as acceptable the affinity fan laws to evaluate the centrifugal compressor behaviour. Affinity laws the affinity laws are derived from a dimensionless analysis of three important parameters that describe pump performance. Using the affinity laws, it is possible to determine approximate curves to estimate the centrifugal pumps new best efficiency point. Many pumping applications require a pump to be operated at speeds that are different from the published performance curves. Evaluation of pat performances by modified affinity law. As far as i know, this just could be applied when the compressibility factor is. There are occasions when you might want to permanently change the amount of fluid youre pumping, or change the discharge head of a centrifugal pump.
The final flow capacity can be calculated by transforming 1. Care must be taken to correctly read the performance data from pump curves. Centrifugal pump curves home fluid flow centrifugal pump curves this tool determine centrifugal pump performance for different impellor diameter and speed based on affinity laws. Basic pump parameters and the affinity laws pdh online. The affinity laws below are well known and used daily by pump people. Pdf evaluating the approximation of the affinity laws and. Dear mates, two question in regards to affinity laws, dimensionless numbers and behaviour prediction in centrifugal compressors. Centrifugal pump affinity laws calculation chemical engineering. The flow gpm varies proportionally with the change in speed. The affinity laws allow engineers to estimate the resulting changes to certain hydraulic parameters caused by the manipulation of a single centrifugal pump variable. Actual bhp should be calculat ed from empirical data rather than by using pump affinity laws. Hydraulically the major subjects consist of head, capacity, hydraulic efficiency, power, and speed.
The following websites offer excellent additional information on pumps and hydraulic systems. Note that there are two sets of affinity laws affinity laws for a specific centrifugal pump to approximate head, capacity. The maximum break horsepower bhp would then be determined using the drivers efficiency. The pump affinity laws are widely used in adjusting pump performance curves from one pump or speed to another. The affinity laws were developed using the law of similitudes which provide 3 basic relationships. Chapter 6 explains affinity laws for centrifugal pumps and how the pump performance is affected by variation in pump impeller diameter or speed. To the affinity laws and beyond the affinity laws below are well known and used daily by pump people. They are also used for scaleup purposes when performance parameters exceed that of existing pumps refer to figure 2. Affinity fan laws for centrifugal compressor posted in student. Assuming the initial flow rate as 100 gpm, the initial head is 100 ft, the initial power is 5 bhp, and the initial speed is 1750 rpm and the final speed 3500 rpm.
In these rotary implements, the affinity laws apply both to centrifugal and. A sdvosb service disabled veteran owned small business. If you double the speed of the pump then you double the flow. The affinity law for fans and dynamic pumps, 2692018 duration. The equations relating rotodynamic pump performance parameters of flow, head and power absorbed, to speed are known as affinity laws.
If a centrifugal pump is driven by an ac driver, then it should operate at a fixed rate rpms dictated by the frequency of the supplied power. Flow is directly proportional to the speed of the of the pump in revolutionsmin. Centrifugal pumps are commonly used in industrial and urban. To approximate the performance of the pump, the affinity laws should be used as follows. How the affinity laws affect pump rerates turbomachinery. Centrifugal pump affinity laws provide a method to determine a new pump operating point when a performance curve that indicates performance with different impeller diameters or operating speeds is not available. Affinity laws affinity laws are used in hydraulics to express the relationship between variables involved in pump or fan performance such as head, volume flow rate, shaft speed and power. Im tasked with replacing a throttle valve on a centrifugal pump with a vfd and doing a cost analysis. The affinity laws also known as the fan laws or pump laws for pumpsfans are used in hydraulics, hydronics andor hvac to express the relationship between variables involved in pump or fan performance such as head, volumetric flow rate, shaft speed and power. If you know the shape of a pump performance curve at a certain speed or with a certain impeller diameter, you can use the affinity laws to predict the. With regard to total performance and efficient design, these two. The change in speed brings about a corresponding change in the head, flow, and power requirements of the pump according to the affinity laws.
Affinity law for multistage pumps pump engineering. Centrifugal pump affinity law is explained for speed change and impeller. The affinity laws for pumpsfans are used in hydraulics, hydronics andor hvac to express the. Hello everyone, i am sizing a pump and ran into a question of how to apply the affinity laws and interpret their results.
In general, most manufacturers will place a lower limit on speed reduction to approximately 40 to 50 percent of full speed before considering speed reduction as extreme, and, beyond that, affinity laws may be used for predictive purposes. Affinity laws pump training, pump education and online. Centrifugal pump affinity laws calculation chemical. The affinity laws of centrifugal pumps or fans indicates the influence on volume capacity, head pressure andor power consumption of a pump or fan due to change in speed of wheel revolutions per minute rpm geometrically similarity change in impeller diameter note that there are two sets of affinity laws. The method of determining the impeller size or speed required to achieve a specific operating point is explained using examples. Centrifugal pump fundamentals pumps are broadly classified as.
Pump efficiency is considered as a constant and variation in speed and impeller diameter is. Evaluating the approximation of the affinity laws and improving the estimate of the efficiency for variable speed pumping by marchi, a. The pump capacity, or flow rate, q varies with the ratio of rpm. The analysis is based on the reduced impeller being geometrically. Pressure or head is proportional to the square of shaft speed. Affinity law for multistage pumps ione mechanical 19 feb 10 06. Q1 q2 n1n2 x d1d2 h1 h2 n1n22 x d1d22 p1 p2 n1n23 x d1d23 npsh31 npsh32 n1n22 per standard nomenclature, q is flow rate, h is head, p is power, and npsh3 is net positive suction head for a 3 percent head drop. Pdf centrifugal pump head prediction using affinity laws. Affinity laws 2 affinity laws 1 pump formulas psig pdf file 467 kb basic pump parameters and the affinity laws.
Other pump formulas affinity laws changes in diameter changes in speed d diameter, in or mm q flow, gpm or m3h h. Centrifugal pump head prediction using affinity laws modified for viscosity. Pdf evaluating the approximation of the affinity laws. Centrifugal pump affinity laws are set of mathematical equations correlating the flow rate, head, brake horse power, speed and impeller diameter of the pump. The result, which can be regarded as the modified pump affinity laws for viscosity flows, was obtained based on the relationships between dimensionless coefficients. Pump affinity laws chicopee mechanical 3 aug 12 22. You may occasionally need to estimate the hydraulic performance of a centrifugal pump at a speed or impeller diameter not shown on the catalog performance curves. Affinity laws online excel calculator is available for download. Example 1 pump affinity laws when pump speed changed impeller size constant. Its free and a wonderful resource for the industry and you can download it at. Centrifugal pump affinity laws mechanical hi everyone, im hoping you all can help shed some light on a problem im working on for my internship.
This is a complete example using a real system which will take the reader through all the steps required to calculate the total head of a pump, the n. The affinity laws are mathematical relationships that allow the performance of a pump to be determined at these different speeds. Estimation of the efficiency for variable speed pumps in. Once a pump has been selected and the impeller diameter to deliver a defined flow rate. The affinity laws or fan laws, as they are sometimes referred to play an important role in determining centrifugal pump performance when operating conditions change.
Changes in speed q flow, gpm or m 3 h h head, ft or m p power, hp or kw n speed, rpm. Q1 q2 n1n2 x d1d2 h1 h2 n1n22 x d1d22 p1 p2 n1n23 x d1d23 npsh31 npsh32 n1n22 per standard nomenclature, q is flow rate, h is head, p is power, and npsh3 is net positive suction head for a 3% head drop. Alps cannot handle the complication of a control valve in the pumps discharge line. The affinity laws are a set of forumlas that predict the impact of a change in rotational speed or impeller diameter on the head and flow produced by a pump and power demanded by a pump. Impeller dia change speed change initial speed final speed final flow final head final brake horse power units input data output data m kw rpm initial flow. The affinity laws tell you how a centrifugal pump responds to changes in conditions see section 4. The relationships established between the physical quantity of the original and that of the model by means of the characteristic coefficients are called affinity laws. Using affinity laws, we can accurately calculate the pressure, flow and required speed and power of a pump from a specific known set point. Affinity fan laws for centrifugal compressor student. Enter information as instructed below and press calculate. The affinity laws are useful as they allow prediction of the head discharge characteristic of a pump or fan from a known characteristic measured at a. The affinity laws are applied to a specific point on a performance curve. If the system pump is flowing x gpm at y feet of head and we want to double the flow rate.
The bell and gossett system syzer and pump affinity laws. Pdf affinity laws relate to the characteristics of pumps operating at different speeds, and in a water distribution. The affinity laws the affinity laws of centrifugal pumps. We finish with a discussion of suction conditions and liquid friction. Using characteristic pump parameters such as the impeller diameter d, rotational speed n, acceleration due to gravity g and the density of the fluid handled. I planned on using the affinity laws to calculate the energy savings, but another student. It says, the change in pump head or pressure drop in the system varies as the square of the change in gpm flow rate.
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