How to Design a Pump for Reduced NPSH

by Kerry Oliphant on Jun 20, 2017 4:39:30 PM

Cavitation occurs in a pump when the bulk liquid pressure starts to approach the vapor pressure of the liquid, and cavities of vapor form as seen in Figure 1.  This figure shows the inlet of a cavitating pump tested in Concepts NREC’s water flow loop.  These cavities can degrade the head rise and efficiency of the pump, create instabilities, and cause significant damage to the pump impeller and other components.  To avoid these effects, a pump must operate with an inlet head that is at least as high as the required net positive suction head (NSPH) that the pump was designed to achieve.  The NPSH is the difference in the inlet head and the liquid vapor head (or vapor pressure converted to liquid head).  Many pumping systems would benefit from the ability to operate at lower NPSH and so reducing the required NPSH of a pump is often of great concern to pump designers.

Turbomachinery is the Key for Sustainable Development

by Thiago Ebel on Jun 15, 2017 4:28:44 PM

While common sense might lead one to conclude otherwise, increasing energy consumption worldwide is a good thing. Higher per capita energy consumption is associated with a higher quality of life: electricity for home appliances, transportation, affordable heating, lighting and so on. On the other hand, there is and should be enormous concern about the type of energy being used to fuel this increased consumption stemming from issues such as environmental impact, national security, etc.  

The chiller industry is under tremendous pressure to convert to new, more environmentally friendly refrigerants.  This change is driven by new global regulations including, the Montreal Protocol and European Union (EU) F-gas regulation. Many chiller OEMs are already announcing new lines of chillers redesigned to use this latest generation of refrigerants. OEMs that have not have started their redesign efforts have a lot of work to do.

New engine development is a costly endeavor and making the right decisions early in the engine design is extremely important. It requires multi-disciplinary consideration of the engine thermodynamic cycle coupled with preliminary aerodynamic design of key engine components. This includes evaluation of size, weight and cost parameters, with constraints imposed by aero, structural, geometrical, manufacturing, and material requirements.

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