Airflow through an air extraction grill

[Hedgehope]

TL;DR

Two spaces separated by an open grille, does reducing pressure in one space draw air through the grille from the other space in a uniform manner ? (volume, pressure & velocity)

Hello,

New member here, brainstorming some ideas for my 'invention'

I need to draw the high humidity air contained in plenum 1 into plenum 2 in a uniform manner to assist with evenly removing the moisture from a single layer of fabric, suspended parallel in plenum 1

My question is does placing a 'simple' (evenly spaced, consistent thickness) grille between the two plenums achieve this ? Or is there more to this than meets the eye ?

 

[Lnewqban]

Welcome, @Hedgehope !

Air tends to follow the path of less resistance.
The effect of the grille on the uniformity with which the air will flow through the cloth is debatable and depends much on the geometry of the whole system.

 

[jrmichler]

The added grille makes no difference.

If the fabric covers the entire opening, and the air is drawn through the fabric, then the airflow through the fabric depends on the resistance to airflow of the fabric. If some portions of the fabric are more porous than other areas, the porous areas will flow more air and dry faster. If the fabric is evenly porous over the entire area, then it will dry evenly.

If the fabric is smaller than the opening, then the air will flow around the fabric and dry the edges faster than the middle.

Or is there more to this than meets the eye ?

There certainly is more to drying than meets the eye. You might find it interesting to read about drying large amounts of paper by searching paper machine dryer section. It's not directly applicable to your situation, but will give you some idea that there is more to drying than just setting a fan in front of something wet.

 

[russ_watters]

The added grille makes no difference.

If the fabric covers the entire opening, and the air is drawn through the fabric, then the airflow through the fabric depends on the resistance to airflow of the fabric. If some portions of the fabric are more porous than other areas, the porous areas will flow more air and dry faster. If the fabric is evenly porous over the entire area, then it will dry evenly.

I agree with this, though my first reaction was to disagree due to the wording of the OP:

I need to draw the high humidity air contained in plenum 1 into plenum 2 in a uniform manner to assist with evenly removing the moisture from a single layer of fabric, suspended parallel in plenum 1

My question is does placing a 'simple' (evenly spaced, consistent thickness) grille between the two plenums achieve this ? Or is there more to this than meets the eye ?

I'm not sure of the thought process here, but uniform flow through the grille isn't important, just uniform flow through the fabric. Perhaps you're envisioning something like flow straighteners on a wind tunnel, but resistance vs a plenum is what creates uniform flow for your type of situation. You can achieve uniform flow through the grille with a high pressure drop/low free area, but the fabric pressure drop is likely to be pretty high, so that won't have any impact since it will already be uniform coming through the fabric (assuming the fabric is uniform).