air temp rise at outlet of a blower 2

[vesselguy]

It's been a hell've a long time since I did any thermodynamics so I'm asking for some help here.

How do you calculate the outlet temperature from a rotary air blower? I want to confirm what I'm seeing from a test report is for real or not. In a test report, a 2 lobe blower has 30F ambient air discharging from the blower at 14 psi at 220F. That just don't make sense to me why it should be so high temperature. I've hit back on my books and know that this is a constant volume isothermal process. Using ideal gas law, P1/T1 = P2/T2 (V is cancel out due to constant volume) I only get T2 = (29 psia/14.5 psia)30F = 60F.

 

[25362]

zdas04

Thanks for the clarifications.

Another site of interest would be:

https://www.pdblowers.com/admin/uploads/32_urai_pressure_performance_curve.pdf

From the graphs therein, and as expected, higher [Δ]p's and lower rotating speeds cause a higher rise in temperatures, due to the "slip" effect.

Would the OP let us have the blower's make, size and rpm to confirm the above assumption?

 

[Compositepro]

Pressure drop of ambient air filters are more commonly measured in inches of water column than psi. While up to 15 psi is possible it wouldn't be prudent.

 

[25362]

From what I've heard it is quite customary for these units to operate with an adiabatic efficiency ([η]) of about 55%. In this particular case, using zdas04 findings for an adiabatic process:

[η] = (137-30)[÷](220-30) = 0.56 = 56%