[Marteusz]

Hi everyone,

I want to simulate a flow through Bosch Rexroth directional valve. I modeled geometry. I want to obtain nominal flow rate through valve.

I have found how companies determine it.

This quotation from Bosch rexroth documentation from their website.

" No norm exists for the term “nominal flow rate”. To obtain a clear numerical value, Rexroth has defined the following:

Inlet pressure: pabs = 7 bar
Differential pressure: ∆p = 1 bar
Medium temperature: TM = 293 K (20 °C)
Humidity: Φ ≅ 0 %

Flow rates are indicated in volumes per time unit. The volume refers to a
normal state valid for pneumatics according to ISO 8778, and this is as
follows:

Pressure: p0 = 100 kPa (1 bar)
Temperature: T0 = 20 °C
Relative humidity: Φ ≅ 65 %

In order to identify the flow rate q as a slack volume, the acronym ANR
(Atmosphère Normale de Référence) can be added after the unit.
Example: q = 12 dm3/s (ANR)"

According to this documentation, I have asssumed reference pressure 1bar, 6 bar pressure at inlet, and 5 bar at outlet.

Ansys CFX gave me mass flow at outlet q = 0.00743 kg/s and i divided it by 1,18kg/s (density in nominal state) and I multiplied it by 1000 and 60 to determine nominal flow in dm^3/min.

But unfortunately results are about 4 times less than from technical card about this directional valve.

Did I simulate this valve in proper way? Why there is so big difference?

Thank you for your help


Mateusz K.