Do affinity laws apply to compressors?

Author: Miss Alessia Waters  |  Last update: Thursday, December 4, 2025

Compressor/fan curves can generally be curve fit to a polynomial: The appropriate affinity law is then applied to the compressor/fan curve, and a speed ratio, denoted with the symbol s, that meets the user's specification on the Variable Speed tab on the Compressor/Fan Properties window is determined.

What are affinity laws for centrifugal compressor?

The affinity laws express the mathematical relationships between the several variables involved in pump performance. They are used to predict what effect speed or impeller diameter changes have on centrifugal pump performance. One can trim an existing impeller and the affinity laws will apply to the new conditions.

What are the laws of compressor?

Boyle's and Charles' gas laws
  • Boyle's law states that if the temperature is constant (isotherm), then the product of the pressure and volume are constant.
  • Charles's law says that at constant pressure (isobar), the volume of a gas changes in direct proportion to the change in temperature.

What are the limitations of the affinity law?

Limitations of Pump Affinity Laws

That is, the actual exponents in the affinity equations are slightly less than their stated values and are different for each pump. This results from friction in hydraulic passages and impellers, leakage losses and variation of impeller discharge vane angles when diameters are changed.

What are the affinity laws for fans?

The affinity laws (also known as the "Fan Laws" or "Pump Laws") for pumps/fans are used in hydraulics, hydronics and/or HVAC to express the relationship between variables involved in pump or fan performance (such as head, volumetric flow rate, shaft speed) and power. They apply to pumps, fans, and hydraulic turbines.

Pump Affinity Laws Example

What are the requirements for affinity?

Windows
  • Windows-based PC (64-bit) with mouse or equivalent input device.
  • Intel, AMD or ARM64 * processor.
  • Hardware GPU acceleration **
  • DirectX 10-compatible graphics cards and above.
  • 8GB RAM recommended.
  • 1GB of available hard drive space; more during installation.
  • 1280x768 display size or larger.

What are the affinity rules?

Affinity is a rule you would set up that establishes a relationship between two or more roles (i,e, virtual machines, resource groups, and so on) to keep them together. AntiAffinity is the same but is used to try to keep the specified roles apart from each other. Failover Clusters use AntiAffinity for its roles.

How accurate are pump affinity laws?

It is important to note that the Affinity Laws are only an approximation, and if pump manufacturers have performance data for different pump speeds, use those values instead.

What are the three basic fan laws?

To summarize these 3 fan laws, flow changes proportionately to speed. Static pressure changes as a function of the change in speed squared. And brake horsepower changes as a function of the change in speed cubed.

What are the prohibited degrees of affinity?

In law, a prohibited degree of kinship refers to a degree of consanguinity (blood relatedness) and sometimes affinity (relation by marriage or sexual relationship) between persons that results in certain actions between them being illegal. Two major examples of prohibited degrees are found in incest and nepotism.

What is the first law for compressor?

The First Law of Thermodynamics expresses the principle of energy conservation. It states that energy is neither created or destroyed. From this, it says that the total energy in a closed system is always conserved, thereby remaining constant. It merely changes from one form into another.

What not to do with a compressor?

- Do not use air directly from a compressor for breathing purposes unless the system has been designed specifically for breathing air. - If you are using your own pressure vessel, only use those that are built to national or international standards. - Never crimp, couple or uncouple pressurized hoses.

What are the limits on air compressors?

Low-Pressure Air Compressors: under 145 PSI (or 10 bar) Medium-Pressure Air Compressors: between 145 and 1,160 PSI (or 10 to 80 bar) High-Pressure Air Compressors: between 1,160 and 15,000 PSI (80 and 1,000 bar) Hyper-Pressure and Very High-Pressure Air Compressors: over 15,000 PSI (1,000 bar)

What is the affinity law?

The affinity laws express the mathematical relationship between the several variables involved in pump performance. They apply to all types of centrifugal and axial flow pumps.

What is the law of centrifugal compressor?

The working principle of centrifugal compression. All air compressors exploit fluid dynamics, either through Boyle's Law or Bernoulli's principle. Compressors that use Bernoulli's principle are categorized dynamic (centrifugal ) or positive displacement compressors.

What is the first law of affinity?

First Affinity Law: speed and flow rate

The first law states that if you alter the speed of a fan or pump, the flow rate of air or water changes proportionally. Simply put, double the speed, and you double the flow.

Is CFM proportional to RPM?

The first fan law relates the airflow rate to the fan rotational speed: Volume flow rate (CFM) is directly proportional to the fan rotational speed (RPM). If the fan RPM is increased, the fan will discharge a greater volume of air in exact proportion to the change in speed.

Does increasing CFM increase static pressure?

The static pressure is controlled by increasing or decreasing the speed of the blower. As your CFM increases, the static pressure will decrease.

What is the relationship between pressure and airflow?

Flow of air or any other fluid is caused by a pressure differential between two points. Flow will originate from an area of high energy, or pressure, and proceed to area(s) of lower energy or pressure.

What are the affinity laws as applicable to centrifugal pumps?

The premise of the first set of affinity laws is: For a given pump with a fixed diameter impeller, the capacity will be directly proportional to the speed, the head will be directly proportional to the square of the speed, and the required power will be directly proportional to the cube of the speed.

What are the affinity laws of VFD?

By taking advantage of affinity law

In the case of centrifugal pump, affinity law specifies the relation between speed and power. It is thus the best option to adjust the supply frequency and speed to control the flow instead of traditional valve throttling. Affinity law saves a considerable amount of power.

Do affinity laws apply to positive displacement pumps?

The worst cases are engineers that try to apply these laws to positive displacement pumps and blowers. That is just wrong! Only centrifugal (dynamic) devices follow these rules.

How to check affinity rules?

Under Tools, select Settings. Under Settings, select Affinity rules, then select Create rule under Affinity rules. Under Rule name, enter a name for your rule. Under Rule type, select either Together (same machine) or Apart (different machines) to place your VMs on the same machine or on different machines.

What is anti-affinity rule?

During a composite VNF deployment, if a couple of VMs need to communicate with each other constantly, they can be grouped together (affinity rule) and placed on the same host. If two VMs are over-loading a network, they can be separated (anti-affinity rule) and placed on different hosts to balance the network.

What are the system requirements for affinity?

Affinity V2 will only install and run on Windows 11 & Windows 10 May 2020 Update (2004, 20H1, build 19041) or later, and require a 64-bit CPU to install and run. To find out which version of Windows you're running, please read this article from Microsoft.

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