CFD Online Discussion Forums - torque shatf & power shaft

hi!

Im not an air fan expert and i`d like some tips. I have a fan modeled in a closed circuit which is somewhat being constricted past the fan, hence the pressure increaeses a little more. So the pressure difference is higher than the dynamic pressure only. Inlet is atmospheric. A mrf model of my fan alone in a environment, using MRF models, shows a mass flow rate of 12-13 kg/s of air at 2500 rpm. a second modeling, without MRF, but with boundary conditions simulating the flow from the fan (w/o swirling) an average surface pressure of 3400Pa results past the fan!
With some simple formulas i have:

Code:

shaft power as : massflowrate*deltaP

                         12.8*3425 = 43520W

shaft torque as:  shaft power/ 2*pi*N   , where N = revolutions per sec

                          60*43520/2/3.1416/2500 = 166Nm

i ask, is the math correct? arent these values a little too high for an 600mm diameter fan? do i have to attach a 1L car engine to keep up this fan rotating in this system?

any comments are mostly welcome!