3 replies to this topic

[Aznadif]

We all know, when we talk about pumps, that the value of NPSH available is strongly temperature dependent (by the vapor pressure value of the treated fluid).

 

Does anyone have experience on how varies NPSH,req with temperature? In the normal pump performance curves, this parameter is drawn as a function of the flow rate considering a specific fluid and a fixed condition of temperature and pressure.

 

My problem arises because I should use a pump of which I have the performance curve for the same fluid and same pressure (also the flow rate is practically the same), but with a lower temperature (the pump was used at 55 °C but in the future we would use it at 80 °C). Starting from the layout of the system, I can calculate the value of NPSH,av but with which value of NPSH,req could I compare?

 

Having no experience I can not evaluate whether I can consider the value of NPSH,req constant when the T changes or if this is an unacceptable approximation.

 

Who is experienced in pumps or who has worked in a pump manufacturing company could give me some suggestions?

 

Thanks in advance.

[fallah]

 

Aznadif,

 

The temperature of the Liquid impacts the NPSH req of a pump. As the pumping liquid temperature increases, the size of the vapor bubbles due to cavitation get smaller, hence leading to lesser damage.

For instance, at a water temperature of 100 degrees C, the NPSH req value will be reduced by almost 0.3 m, at the same other conditions.

 

Then this effect actually provides a small increment in the actual NPSH margin.  Thus, don't worry about the NPSH req at higher operating temperature and just calculate the NPSH av at the new temperature without correction in NPSH req.

[breizh]

Hi ,

To support your query , together will Naser ,

 

Breizh

 

https://blog.craneen...is-it-important

Edited by breizh, 26 October 2018 - 09:09 PM.

[Aznadif]

Thanks to Naser and Breizh