Intake Fan BC, using Pressure-jump?

Abhya · October 11, 2014, 05:42

I am working on a an air duct into which air is pushed by fan positioned at the duct inlet.
I'm using " Pressure-jump" to model the fan using the "Static Pressure Fan curve form the manufacturer"
The Pressure jump box allows to define the pressure jump as a function of the " LOCAL normal velocity " as is stated in FLUENT manual here :
http://www.arc.vt.edu/ansys_help/flu...ec_bc_fan.html

However, I want to use the Mass-weighted average velocity at the fan face for calculating the pressure jump.
This is also specified in fluent in section -
"6.3.18.1.1. Modeling the Pressure Rise Across the Fan"
as - "You can, optionally, use the mass-averaged velocity normal to the fan to determine a single pressure-jump value for all faces in the fan zone."
However, I have searched everything and I couldn't find anything related to how to get Mass weighted average velocity at the fan face to calculate the pressure jump.
Anybody please help !
Its Urgent

The "INTAKE-FAN" boundary condition in FLUENT uses

Abhya · October 11, 2014, 06:02

Also, The pressure jump stated in FLUENT is the total pressure jump or the static pressure jump due to the FAN???

Abhya · October 13, 2014, 03:00

for no reply here...
I have figured it out myself though !

Conclusion:
Mass weighted average values for the "polynomial fan curve inputs" can't be used directly ! one has to find the mass weighted normal velocity at the fan in face and input the corresponding Pressure jump (constant) into fluent!

For using fan-curve to give sensible results refer to the following link!
http://www.eureka.im/307.html

bightv42257 · February 2, 2015, 14:51

I have a similar question as well.
I am simulating a radiator, which is cooled by a 120 mm X 120 mm fan (example).

Since we are interested in the vortex effect for a radiator, the radiator is divided into hundreds of cell and only one small cell is defined in Fluent.

My question is, what to choose the fan's boundary condition correctly?

The pressure jump of fan is known. It looks like this Polynomial profile can not be applied directly at the fan Inlet of a single cell. Otherwise, the model becomes a while fan blows into a small cell of radiator.
For a single cell, a fixed fan speed might be more appropriate.

So, I could assume an operating point of the fan and choose a fixed fan speed at the inlet of the small cell.
If air's inlet speed is fixed, the fan's operating point will not be considered due to the pressure drop of vortex's geometry.

How can I simulate fan's operating point according to vortex's geometry? Probably, a full size of radiator is needed, but the model size will be huge.

October 11, 2014, 05:42	Intake Fan BC, using Pressure-jump?	#1
Abhya Member Join Date: Jul 2012 Posts: 48 Rep Power: 13	I am working on a an air duct into which air is pushed by fan positioned at the duct inlet. I'm using " Pressure-jump" to model the fan using the "Static Pressure Fan curve form the manufacturer" The Pressure jump box allows to define the pressure jump as a function of the " LOCAL normal velocity " as is stated in FLUENT manual here : http://www.arc.vt.edu/ansys_help/flu...ec_bc_fan.html However, I want to use the Mass-weighted average velocity at the fan face for calculating the pressure jump. This is also specified in fluent in section - "6.3.18.1.1. Modeling the Pressure Rise Across the Fan" as - "You can, optionally, use the mass-averaged velocity normal to the fan to determine a single pressure-jump value for all faces in the fan zone." However, I have searched everything and I couldn't find anything related to how to get Mass weighted average velocity at the fan face to calculate the pressure jump. Anybody please help ! Its Urgent The "INTAKE-FAN" boundary condition in FLUENT uses

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October 11, 2014, 06:02		#2
Abhya Member Join Date: Jul 2012 Posts: 48 Rep Power: 13	Also, The pressure jump stated in FLUENT is the total pressure jump or the static pressure jump due to the FAN???

October 13, 2014, 03:00		#3
Abhya Member Join Date: Jul 2012 Posts: 48 Rep Power: 13	for no reply here... I have figured it out myself though ! Conclusion: Mass weighted average values for the "polynomial fan curve inputs" can't be used directly ! one has to find the mass weighted normal velocity at the fan in face and input the corresponding Pressure jump (constant) into fluent! For using fan-curve to give sensible results refer to the following link! http://www.eureka.im/307.html

February 2, 2015, 14:51		#4
bightv42257 New Member Anderson Join Date: Dec 2014 Posts: 2 Rep Power: 0	I have a similar question as well. I am simulating a radiator, which is cooled by a 120 mm X 120 mm fan (example). Since we are interested in the vortex effect for a radiator, the radiator is divided into hundreds of cell and only one small cell is defined in Fluent. My question is, what to choose the fan's boundary condition correctly? The pressure jump of fan is known. It looks like this Polynomial profile can not be applied directly at the fan Inlet of a single cell. Otherwise, the model becomes a while fan blows into a small cell of radiator. For a single cell, a fixed fan speed might be more appropriate. So, I could assume an operating point of the fan and choose a fixed fan speed at the inlet of the small cell. If air's inlet speed is fixed, the fan's operating point will not be considered due to the pressure drop of vortex's geometry. How can I simulate fan's operating point according to vortex's geometry? Probably, a full size of radiator is needed, but the model size will be huge.