Motor selection for process fan.

[srinivasan]

1)fan is going to use for suck the waste gas from industry and outlet will be connected to thermal oxidizer chamber. incoming gases rate is 22000 Nm3/hr. i dont know about fan design calculation. In this worst case i have to make panel inquires. without motor rating it is not possible . give me some rough calculation for fan details with this flow.

2) In same case damper valves is going to be use for control the flow of gases. which type of damper valve is good to control the flow(butter fly, pipet valve etc..). Damper valve are motorized control . how select motor rating for dampers.

3) if fan details are known.. inertia is in Nm . How to calculate HP rating for motor.

4) What is the calculation to select VFD for motors.

 

[Phil Corso]

Srinivasan...

To start, the value you cited, 22,000 Nmt³ has the wrong dimension! N is force, while mt³ is volume! (Yes, I purposely use mt for meter, to avoid confusion about m as mass!)

Regards, Phil Corso

 

[GoldDigger]

Srinivasan...
To start, the value you cited, 22,000 Nmt³ has the wrong dimension! N is force, while mt³ is volume! (Yes, I purposely use mt for meter, to avoid confusion about m as mass!)

...inertia is in Nm...

Torque and energy, not inertia (mass) or moment of inertia, would have dimensions of N-mt, while volume of gas would be in mt³. And the power required by the fans would be the total work per second, which would involve the back pressure times the area times the mass flow rate IF back pressure was a major factor, and a much more complex value involving drag of the fan rotor is negligible back pressure.

Pressure = N/mt²
Area = mt²,
Energy has units N-mt.
Power has units N-mt/sec.
The OP's units were only off by (1/sec)!
Dimensional analysis definitely has its limits when it is not clear what your input variables are in the first place.

 

[petersonra]

In general you need to calculate how much mass needs to be moved how fast and that will give you an idea how much energy is required over a period of time. That will tell you how many HP is required in a very rough way as a bare minimum.

Why would you have both a damper and a VFD?

 

[srinivasan]

Torque and energy, not inertia (mass) or moment of inertia, would have dimensions of N-mt, while volume of gas would be in mt³. And the power required by the fans would be the total work per second, which would involve the back pressure times the area times the mass flow rate IF back pressure was a major factor, and a much more complex value involving drag of the fan rotor is negligible back pressure.

Pressure = N/mt²
Area = mt²,
Energy has units N-mt.
Power has units N-mt/sec.
The OP's units were only off by (1/sec)!
Dimensional analysis definitely has its limits when it is not clear what your input variables are in the first place.

22000 Nm3/hr is flow rate not pressure.how ever torque is required to calculate hp rating of the motor. moment of inertia or rotor inertia is the considerable factor in calculation of torque. please explain if i am wrong. there is no back pressure because blower motor will be in on condition for all operating condition.

 

[srinivasan]

In general you need to calculate how much mass needs to be moved how fast and that will give you an idea how much energy is required over a period of time. That will tell you how many HP is required in a very rough way as a bare minimum.

Why would you have both a damper and a VFD?

damper is to control the chamber reactions (reversible actions for heat recovery) and vfd for control the process fan

 

[wallypiper]

Call a fan expert (rep or distributor) or go to a fan manufacturers website. BHP required is standard part of performance data for every fan. Fan performance is based on volume (cubic feet, cubic meters, liters . . .) and TSP (total static pressure). All fans have a characteristic curve that plots volume against TSP and normally includes HP. No need to work out how to calculate all that for yourself. There are just too many variables - fan type, blade design, double inlet or single inlet etc. A prop fan uses much less HP for a given volume than a centrifugal fan but typically has much less pressure capability or at least a very flat performance curve. You're re-inventing the wheel.

 

[petersonra]

This sounds like a system that would need some experienced and astute engineering input on. I would not be making any wild guesses about fan or actuator sizes. It is just too easy to be wrong, and wrong by an order of magnitude is not impossible.