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Stead State NPSHa Calculation with UNISIM

Stead State NPSHa Calculation with UNISIM

Stead State NPSHa Calculation with UNISIM

I tried to be as explanatory in the pic as I can be. To model tank with a water level (not tank level) of 10m I used a single vertical pipe segment (of length 10m & -ive elevation of 10m) because in steady state tank's level has no impact on NPSHa which is to be calculated.

Pipe's ID is chosen such that friction gradient per unit length is kept minimum to only account for static head. Manual calcs are are shown side by side.


Why NPSHa calculated by UNISIM is 4m higher? I have taken into account velocity head due to Pump suction nozzle dia; increasing it reduces NPSHa drastically ...its understandable as the suction velocity goes down; is my understanding correct (highlighted parts in manual calcs)?


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