Fan Selection Using CFD (Cosmos FloWorks)

[mbowers]

Hello,

I'm using Cosmos FloWorks to select a fan for an enclsoure I'm designing. Thus far, I've built the pressure drop curve for my enclosure by specifying different volume flow rates at the fan inlet (5CFM, 10CFM, 15CFM, etc...). This resulted in what I consider a reasonable curve (~0 in H2O at 3CFM up to .36in H2O at 30CFM). Based on the required temperature rise, I determined that 20CFM was needed for my enclosure.

I went to a major fan manufacturer and found a fan that would supply about 20CFM at the corresponding back pressure from my enclosure pressure drop curve (~.16in H2O). Then, I built the fan curve in FloWorks and used that to validate my selection.

The results of that simulation were mixed... The temperature rise was within a degree or two of the simulation I ran just using a 20CFM volume flow. However, the pressure was a good deal higher (0.3 in H2O vs. the 0.16in H2O from the 20CFM simulation).

Does anybody have any ideas as to what might be happening? Shouldn't I be seeing about the same pressure using the fan? All of the simulations were run at a 101325 Pa environment pressure and an ambient temperature of 50 Deg. C. I took the static pressure results from the same face that I specified the volume flow/fan.

Any help is appreciated

Thanks!

(This thread was also posted in the Cosmos forum)

 

[btrueblood]

Well, what was the fan's volumetric flow rate in the simulation (i.e. how does it compare to the fixed-volume flow case), and how do the inlet static and total pressures compare between the two runs?