# Evaporating droplet

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 July 12, 2022, 08:11 Evaporating droplet #1 New Member   Join Date: Mar 2014 Posts: 8 Rep Power: 10 Hi everyone. I am simulating the simple problem of sprayed particle in hot air. when the mass flow rate of spray is low everything is alright. however when the mass flow rate of particle exceeds a certain limit, the energy equation shows problems. The temperature would be limited to 1 K and 5000K. I tested with very small under relaxation factor of 0.01. It happens again in unsteady simulation. can any one give me a hand? thanks.

 July 12, 2022, 15:53 #2 Senior Member     Alain Islas Join Date: Nov 2019 Location: Mexico Posts: 101 Rep Power: 5 Does this error occur at the very beginning of your simulation? Or after some time? If its the first scenario, you may probably defined a bad boundary condition. What is your mass flow rate? injection velocity and droplet size? If its the second scenario, then probably there is something weird going on with the flow

July 15, 2022, 09:42
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Quote:
 Originally Posted by alainislas Does this error occur at the very beginning of your simulation? Or after some time? If its the first scenario, you may probably defined a bad boundary condition. What is your mass flow rate? injection velocity and droplet size? If its the second scenario, then probably there is something weird going on with the flow
Yes the error occur as soon as the DPM iteration starts. I'm not sure. I thinks the evaporation model depends on mass flow rate.

Air with dust enters the domain at the inlet with mass flow rate of 37.7 kg/s and temperature of 680 K. (air velocity at inlet is about 10 m/s)
There is 8 water spray with total mass flow rate of 27.7 kg/s with temperature of 340 K. The droplet diameter is 500-1000 micron. with injection velocity of 50 m/s.

If I reduce the mass flow rate to 0.277 kg/s everything is OK.
I think the fluent over predict the mass exchange between water droplet and air.

I tried everything.

 Tags dpm, droplet, energy, evaporation