Technology Background – Pumps and Fans

Pumps are used to transfer liquids and gases for processing. They provide cooling, heating and lubrication, power hydraulic systems and process sewage.¹

Fans are used widely in industrial and commercial applications, for ventilation, cooling, heat distribution, blowing and drying.

The power absorbed by a pump or fan (and the energy over time), is the product of pressure developed and volume flow rate. Reducing either the pressure or flow rate required will reduce power and energy. In an existing system, reducing the volume flow rate will, depending on the reduction mechanism, usually also reduce the system pressure requirements. These two parameters are often inter-dependent, and a small reduction in flow may therefore deliver a much larger reduction in energy required.

Pump systems

There are two main categories of pump. They are characterised by the way in which they impart energy to the fluid being pumped, namely positive displacement and centrifugal pumps.²

• Positive displacement pumps pressurise the fluid by squeezing it with each piston stroke or shaft rotation.
• Centrifugal pumps (or rotodynamic pumps) work by adding kinetic energy to a fluid using a spinning impeller. This fluid then enters the diffuser section of the pump where it slows and the kinetic energy is converted into pressure.

While for many applications either a positive displacement or a centrifugal pump could be used, centrifugal pumps are more common because they are simple and safe to operate, require minimal and fairly straightforward maintenance, have characteristically long operating lives, and can operate under a broad range of conditions.³

Fan systems

Fans are rotary bladed machines which move air; a distinction is made between fans and air compressors (which work at higher air pressures of greater than 350 kPa). They are used widely in both industrial and commercial applications for heating, cooling, ventilation, air circulation, blowing and drying.

Fans form part of a wider fan system which also includes an electric motor and associated control system, a drive system, duct- or pipe-work, filters and outlet diffusers, flow controllers, and possibly heat exchangers.⁴ Fans are also used to provide combustion air for boilers and for mine ventilation.

There are two main types of fans—centrifugal and axial. Mixed flow fans are a combination of both. The different types of fan are characterised by the path of the airflow through the fan.

• Centrifugal fans are the most common type of industrial fan. They consist of an impeller with multiple blades rotating within a scroll or spiral shaped casing. The rotating impeller draws air in through a central inlet and pushes the air outwards into the volute shaped casing and through the air discharge. Centrifugal fans can have several types of blade shapes, including forward curved, radial-blade, radial-tip, backward-inclined, backward-curved, and airfoil. They can generate high pressures with high efficiencies.
• Axial fans use rotating propeller blades to generate aerodynamic lift which pressurises the air and creates an air-stream parallel to the axis of the fan. They are available in a number of different types including propeller (the simplest), tubeaxial and vaneaxial.⁵

For more information

• Discussion Paper: Improving the Energy Efficiency of Industrial Equipment 2010 (Opens in a new window)
  • Equipment Energy Efficiency Committee
  • PDF 3.8 MB

  This Discussion Paper sets out ideas for improving the energy efficiency of new industrial equipment in Australia and New Zealand. It provides the policy context and describes key improvement strategies for key industrial equipment such motor systems, pumps and fans, compressed air systems, chillers and boilers.

  The Paper is being used to inform the development of a 10-year Strategy on Industrial Equipment as part of the Equipment Energy Efficiency (E3) Program.

• Improving Fan System Performance – A Sourcebook for Industry 2003 (Opens in a new window)
  • US Department of Energy
  • PDF 1.2 MB

  This guide is not intended to be a comprehensive technical text on improving fan systems, but rather a document that makes users aware of potential performance improvements.  It covers a range of topics including fan types, maintenance, indications of oversized fans, system leaks, controlling fans with variable speed drives and fan-system economics.

• Improving Pumping System Performance – A Sourcebook for Industry 2006 (Opens in a new window)
  • US Department of Energy
  • PDF 3.1 MB

  This guide provides some practical guidelines and covers a range of topics including common pumping system problems, indications of oversized pumps, piping configurations, maintenance, centrifugal pumps, positive displacement pump applications, pony pumps, impeller trimming and variable speed drives.