Basic pump parameters and the affinity laws a pdh online. 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. Pump affinity laws are equations of proportionality that indicate how a change in impeller diameter d, or rotative speed n, affects the capacity q, the differential head h, and the required brake horsepower hp of a centrifugal pump. Back in the dark ages of 1976, before we all had computers sitting on our desks and when engineers still used slide rules, i came to work at eldridge as a very young sales engineer. Also using the pump law we can see that there is a relation to the flow rate of a pump and the power required for the pump. If you are trimming impellers on a 10stage pump, you will need to reduce the amount of trim by roughly 15 percent to avoid reducing the capacity and head below what you would originally expect from the affinity laws. The affinity laws for pumpsfans are used in hydraulics, hydronics andor hvac to express the relationship between variables involved in pump or fan performance such as. The affinity laws state changes in the speed or diameter change capacity by direct proportion. As far as i know, this just could be applied when the compressibility factor is negligible. 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. White paper stop falling off the curve maintenance.
Pump affinity laws for centrifugal and positive displacement pumps. They are also useful to modify your pumps for new and different required duties. Affinity laws for centrifugal pumps as applicable to variable. Affinity is the latest stateoftheart pump selection program from flowserve. The following websites offer excellent additional information on pumps and hydraulic systems. Note that the affinity laws for pumps are not identical with fans fan affinity laws. Evaluating the approximation of the affinity laws and improving the estimate of the 1. Affinity laws toolbox calculating gpm with rpm change impeller diameter constant design rpm 1 design gpm 1 new rpm 2 new gpm 2 calculating tdh with rpm change impeller diameter constant design tdh 1 new tdh 2 calculating bhp with rpm change impeller diameter constant design bhp 1 new bhp 2 calculating gpm with impeller change speed is.
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 different speed or impeller diameter. Enter information as instructed below and press calculate. The new york blower company is committed to supporting and supplying necessary equipment to meet the critical demands of the supply chains essential to aid america in this time of need. Fan laws and system curves new york blower company. The good news affinity law theory helps us understand the principle of flow, head, and power dynamics. Hvac equipment and systems fan affinity laws for the. Capacity, head, npsh and horsepower change as a result of impeller diameter change. The pool pump affinity law chlorine king pool service. The mystery behind pump affinity laws and other curve phenomena have you ever had a centrifugal pump that does not operate on its curve. The affinity laws relate the performance of a known pump along its. Variable speed photovoltaic water pumping using affinity laws.
Pdf evaluating the approximation of the affinity laws. It should be remembered that the affinity laws are more accurate when used to calculate speed variations than for impeller diameter variations. The efficiency of the pump does not change with speed changes. The affinity laws are derived from a dimensionless analysis of three important parameters that describe pump performance. Usually, pump performance curves are based on standard.
The affinity laws of centrifugal pumps or fans indicates the influence on volume capacity, head pressure andor power consumption of a pump. This research is a continuation of efforts aimed at establishing the modified affinity laws for viscosity to predict the pump performance directly from a plot in terms of dimensionless numbers i. Pump flow is taken at the largest impeller diameter for double suction impellers pump flow is divided by two. Apr 28, 2017 the equations relating rotodynamic pump performance parameters of flow, head and power absorbed, to speed are known as affinity laws. The above rules can be expressed by the following equations. Various published handbooks and data sheets use a modified form of the affinity laws to estimate the performance of a pump when the impeller diameter is reduced. Customers have access to the same pump selection tool that is used by flowserve application engineers. 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. The affinity laws for centrifugal pumps state that the hq curves at various rotational speeds can be derived from the following relationship as conventionally represented. The pump affinity law for pool pumps shows how all of this is possible between the 3 main components. The affinity laws are used to change the pump characteristics by changing the pump speed, and consequently, the pump flow rate, head, and power will be varied.
Q flow rate h head y specific energy n rotational speed if pq. Centrifugal pump fundamentals pumps are broadly classified as kinetic or positive displacement. Dear mates, two question in regards to affinity laws, dimensionless numbers and behaviour prediction in centrifugal compressors. The affinity laws for centrifugal pumps and fans are used to express the influence on volume capacity, head pressure andor power consumption due to.
Many pump manufacturers produce a range of curves that illustrate performance at various impeller diameters. Represented in figure 3 are the three affinity laws. The pump speed, head, and flow relationships are expressed by the affinity laws. All you need to know is the system head and flow requirements to determine the right pump for the job. With regard to total performance and efficient design, these two. The affinity laws can also be applied to impeller diameter variations. The affinity laws variable frequency drives theory the affinity laws can determine the system performance for centrifugal devices, including theoretical load requirements and potential energy savings.
Laws, traditions and customs relating to affinity vary considerably, sometimes ceasing with the death of one of the marriage partners through whom affinity is traced, and sometimes with the divorce of the marriage partners. A hard sphere collision model is used, and subsequently a correction to account for the flow behaviour of air is incorporated. You can quickly determine the effect of changes in either pump speed or impeller diameter on pump performance. This page provides information and resources regarding the affinity laws that are used to project new performance points and curves for a pump or fan given a known performance point or curve. For example, if rpm drops to 70% of the original, gpm drops to 70% of the original. Providing support for 80plus products, affinity is a webbased tool that delivers immediate, realtime access to the latest, most accurate data on flowserve pumps. The affinity laws allow engineers to estimate the resulting changes to certain hydraulic parameters caused by the manipulation of a single centrifugal pump variable. Each curve represents a series of points derived from the 60 hz curve for flow and corresponding head points, transformed using the affinity law equations.
In the united states, electricity is at 60 cycles per second hertz. Affinity laws can be used to calculate volume capacity, head or power consumption when speed and wheel diameters are changed. This method is referred to as the affinity laws or fan and pump laws. The flow gpm varies proportionally with the change in speed. Affinity law for multistage pumps ione mechanical 19 feb 10 06. Physical similarity is achieved if the ratios see characteristic coefficient of the original and the model are the same. The affinity laws describe how changes in rpm n affect gpm, head, and hp in centrifugal pumps. Capacity, head, npsh and horsepower change as a result of speed change. Fan laws o14 reference information fantech 2016 o nomenclature for symbols used in this page. Affinity laws and specific speed in centrifugal pumps. Centrifugal pump fundamentals pumps are broadly classified as. Horwitz project engineer affinity laws the performance of a given pump at various speeds and the performance of geometrically similar pumps is governed by a set of formulas known as the. The laws will help you extrapolate and predict pump performance at different velocities. Most of the savings is from the reduction of the speed of the motor rpms even though some of it is contributed to how efficient a permanent magnet motor is.
The pump speed needs to be reduced in order to achieve the required flow at the twl and the required speed can be calculated using the affinity laws. 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. 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. Thus pump performance curves for frequencies other than 60 hz or 50 hz can be generated with the affinity laws. In general, the affinity laws project the new operating points by moving up and down a system curve. Affinity laws pump training, pump education and online. View test prep affinity laws from eess gt001 at american university in cairo. In practical application, grundfos provides all the information you need to easily determine your energy savings with e pumps and boosterpaqs. Turbo machines affinity laws can be used to calculate volume capacity, head or power consumption in centrifugal pumps with changing speed or wheel diameters. Often times a fans speed or impeller diameter will be changed. N speedrpm the affinity law for a centrifugal pump with the impeller diameter held constant and the speed changed.
It is also required that the two impellers speed or diameter are running at the same efficiency. Inputting the data that was calculated form the earlier equations. The course content is in a pdf file 467 kb basic pump parameters and the affinity laws. I planned on using the affinity laws to calculate the energy savings, but another student showed me a table we are supposed to use which showed that throttling the pump reduces the power of the pump. Our calculations prove the affinity laws and provide numerical estimates of the air delivery, thrust and drag on a rotating fan. Using affinity laws, we can accurately calculate the pressure, flow and required speed and power of a pump from a specific known set point. If the fan is a centrifugal fan, then the change in performance of the fan can be predicted quickly through the affinity laws. Affinity law for multistage pumps pump engineering engtips. Affinity laws are also known as affinity equations. You have probably been taught that pumps always operate on their curves. When a fan operates in an unchanging system, the fan laws tell us that the airflow varies proportionally to fan rpm, static. Basic pump parameters and the affinity laws pdh online. Being able to predict these affects allows the rotating equipment engineer to examine the effects before implementing the changes. The only requirement is that the two pumps or fans are dynamically similar, that is the ratios of the fluid forced are the same.
In this paper, the affinity laws are adapted to achieve the pump hydraulic requirements while the power delivered to the pump motor remains unchanged by constructing new pump curves. With pump impeller diameter d held constant and speed n change. As pump efficiencies are more or less dependent on friction conditions, they are subject to other conversion laws see efficiency scaleup. For centrifugal pumps, the affinity laws that relate flow, pressure head gain, and power to the speed of the pump, can provide a good approximation of the real pump behavior for a wide range of.
Hydraulically the major subjects consist of head, capacity, hydraulic efficiency, power, and speed. Care must be taken to correctly read the performance data from pump curves. Pump affinity laws the pump affinity laws predict the affects of changing the speed of a centrifugal or rotary pump on flow rate, head and power. The affinity laws see peerless technical information bulletin no. Because most pumps are directly coupled to a standard industrial electric motor, the pump speed is most often the motor. 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.
They are useful particularly for the modification of existing pumps to meet a new service. In this work we use kinetic theory to attack this problem. Affinity laws pumps affinity laws d1 510 d2 530 initial q1. 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. This tutorial goes a step further and describes the effect of these changes on pump efficiency. Affinity laws changes in diameter changes in speed. Geoff edwards, the technical product engineer at axair fans uk limited, explains the three basic fan laws when applied to warehouse ventilation studies. Affinity fan laws for centrifugal compressor student. Hbhp hydraulic brake horsepower required by pump pump efficiency 1. The following relationship exists for centrifugal pumps for frequency based on affinity laws and considering a rated frequency of 60 hz new motor rpm new or changed frequency 60 hzmotor rpm at 60 hz new flow rate new or changed frequency 60 hzflow rate at 60 hz. Affinity laws the affinity laws are derived from a dimensionless analysis of three important parameters that describe pump performance. Affinity fan and pump laws what is the effect of a changing speed.
Pdf efficiency prediction of centrifugal pump using the. Jul 16, 2012 the pump affinity laws can be used to predict the performance of a centrifugal pump as two variables change, the pump shaft rotational speed and the pump impeller diameter. Im tasked with replacing a throttle valve on a centrifugal pump with a vfd and doing a cost analysis. The affinity laws for centrifugal pumps state that the hq curves at various. The affinity laws are valid only under conditions of constant efficiency. Please request a pdf toolbox cd from your local heidelberg office in order. The affinity laws answer these and other similar questions. If you know the shape of a pump performance curve at a certain speed or with a certain impeller diameter. Todays eitpe exam question looks at the pump laws with with a constant diameter impeller. N pump speed rpm bhp brake horse power in kw pump input power. The power saved would also be lowered because of the reduced efficiency. The fan laws are a group of useful equations for determining the effects of a change in the speed, the diameter of the fan and the density of air in the system. How to use affinity laws to calculate a new best efficiency point. The mathematical relationships that exist between flow rate, head, power and speed and based on a known pump performance are referred to as the affinity laws.
Mar 04, 2016 the affinity laws the affinity laws state that 1 flow will change directly when there is a change in speed or diameter, 2 heads will change as the square of a change in speed or diameter, and 3 hp will change as the cube of a change in speed or diameter. A 25 horsepower and 3600 rpm b 15 horsepower and 1450 rpm c 60 horsepower and 2900 rpm d 15 horsepower and 2900 rpm. Law 1 means that as rpm is reduced, flow gpm is reduced in a linear relationship. They are also used for scaleup purposes when performance parameters exceed that of existing pumps refer to figure 2. Pumps affinity laws d1 510 d2 530 initial q1 flow rate 405 initial p1 pressure 95. These keywords were added by machine and not by the authors. The energy savings are achievable through affinity laws. 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.
Affinity laws are a set of equations or laws governing the operation. Using the affinity laws, it is possible to determine approximate curves to estimate the centrifugal pump s new best efficiency point. This process is experimental and the keywords may be updated as the learning algorithm improves. In addition to kinship by marriage, affinity can sometimes also include kinship by adoption or a step relationship. Turbo machines affinity laws can be used to calculate volume capacity, head or power consumption in centrifugal pumps with changing speed or wheel. As formulae, affinity laws are expressed as follows in table 1. Engineers use a shorthand for estimating the effect of speed rpm on power. Or to put it another way, the affinity laws for a centrifugal pump do not and are not supposed to be dependent on duty. First affinity law flow is proportional to the shaft speed, i. Leave a comment if you would like to discuss the affinity laws or variable frequency drives. Pump affinity laws for centrifugal pumps or fans 1. Why can we consider as acceptable the affinity fan laws to evaluate the centrifugal compressor behaviour. The analysis is based on the reduced impeller being geometrically similar and operated at dynamically similar conditions or equal.
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. They are merely a way of predicting the charcteristic curve of the pump when you have a known characteristic curve and wish to make a variation in speed of the pump or diameter of the impeller. But there are times when pumps do not operate, or appear to operate on their curves. Now using the pump affinity laws, we can see there is a relation to the flow rate and the speed at which the impeller turns. What is the resulting change to the pump speed and horsepower needed. This centrifugal pump curve calculator is meant to quickly calculate the different operating conditions when a centrifugal pump is sped up or slowed down. 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. Pdf evaluating the approximation of the affinity laws and. The pump head pressure varies with the square of the change in the speed.
The performance of a given pump at various speeds and the performance of geometrically similar pumps is. The affinity laws govern the performance of your pumps. Jun 14, 2014 affinity fan laws for centrifugal compressor posted in student. Friction a b hs h o figure 3 conclusion of our look at a new tool that predicts how pumps and systems interact. N speedrpm the affinity law for a centrifugal pump with the. Affinity law for multistage pumps pump engineering. Pump curve speed calculator affinity law calculator. These laws are mathematical expressions that define changes in pump brake horsepower bhp, head and capacity when a change is made to pump speed, impeller diameter, or both.
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