## Fluids

#### How to define the mass flow rate in injection of DPM

• mreza65
Subscriber

Hi. Could you please clear it below?

For example in a microchannel, we have an inlet and outlet. In a single-phase mode I assume "Velocity inlet" as the condition of the inlet with a velocity of 0.45m/s. However, in the Discrete Phase Model, I choose surface injection and the surface is my the inlet. Now, I want to add "Volume Fraction" of particles as a second-phase. In the injection window, I have to specify the amount of mass flow rate. My question is here, is it correct to use the formula in the attached file?

• DrAmine
Ansys Employee
As ANSYS staff we do not look into attachments.
• mreza65
Subscriber

Hi Amine.

I wrote the formula in the attached file because I cannot that here.

I explain my problem statement here in detail.

First, I want to decrease the temperature of a 2-D microchannel with water. Inlet velocity is 0.45m/s, inlet width is 0.2mm, density equates 995.7 kg/m^3.

So, the mass flow rate is equal to 0.45x0.0002*1*995.7 (=0.089613).

Then, I want to inject AL2O3 with a volume fraction of 0.03. I think that I can apply this fraction in  Discrete Model in the mass flow rate of injection. Could you help me how can calculate it? I use the following formula;

mass flow rate of particle= (volume fraction x density of particle x mass flow rate of water obtained above) / (density of water)=(0.03*3600*0.089613)/995.7

Is it correct?

• Rob
Ansys Employee

In the injections you'll see a mass flow: that is the mass of DPM material.  If you want to inject a certain volume or mass fraction of particles you'll need to do the sums.

If you're interested in a certain volume fraction then work out the inlet (fluid) volume flow rate and then calculate from there.

• mreza65
Subscriber

Thank you.

• hero55
Subscriber

please mreza65   can share me how you calculate total mass flow to get 0.03 volume fraction

and thank you

Any help would be appreciated

• hero55
Subscriber

up

• Rob
Ansys Employee

Maybe read his post carefully? Volume fraction calculations are explained in most text books.

• hero55
Subscriber

sir rwoolhou   here I dont understand you (If you want to inject a certain volume or mass fraction of particles you'll need to do the sums. )

what did you mean  (you'll need to do the sums) what sums?

and thank you very much.