Valves and pumps

A pressure change can be specified at either the upstream or the downstream end of a pipe. These changes can be described as fixed pressure drops, fixed pressure increases or as a function of the mass flow in the pipe.

Only a valve or a pump can be specified in a pipe.

For a pump, the current pressure is calculated on the basis of the expression below:

Where:

A, B are constants determined through interpolation between relevant reference values (ΔQ,Q) in the pump characteristic.

Q        =       mass flow in the pipe [kg/s

η        =       efficiency of pump

 

For valves, the pressure reduction is calculated according to the following formula:

 Where:

Q        =       Flow [l/s

K_v       =       Valve coefficient [t/h/√mwc