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Relationship between differential pressure and airflow through a filter

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Apr12-12, 11:08 AM
P: 2
I have a question regarding the relationship between differential pressure across a filter, the airflow through the filter and the size of the orifice that the aire is moving through. I would like to be able to predict differential pressure required to maintain a constant airflow as the filter I am using blocks over time.

I am having trouble finding a suitable expression online and Filter Manufacturers do not supply this information with their filters.

Can anybody tell me if there is a simple expression which can be used please?

Thanks in advance to anybody who can assist me!

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Apr12-12, 08:29 PM
P: 22,313
Welcome to PF!

I'm sorry, but this can't work because you have one unknown driving the other: You would have to know the loading of the filter to find the pressure drop on a table or via a formula but the only way to measure filter loading is by measuring the pressure drop!

What you need is to maintain a constant dp across a device known to be fixed, such as a cooling or heating coil. Then the pressure across the filter can fluctuate while keeping the airflow constant.
Apr13-12, 06:32 AM
P: 2
Thanks for the welcome Russ. I am not an engineer so I am taking time to get through things that probably seem very basic.

In relation to the pressure drop and loading I am working through correlating the two through measurements.

I am using a vacuum pump to generate the flow through the filter but cannot control the pressure or loading accross the filter. I know the pressure before and after the filter but not the airflow. Am I dealing with too many unknowns? Thanks for your help.


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