Hole size for PVC fire gear dryer

[teamz]

I'm constructing an air dryer for our fire department's PPE (turnout, bunker gear) using PVC pipe and a blower and need to determine the best hole size for all the PVC pipe and fittings (lots of holes throughout the PVC to supply air drying). The blower is a Zoom W4L 750W blower producing 700 CMF. To distribute the air, the base structure consists of a 2' x 8' box built using standard 2x6 lumber with a 3/4" plywood top and bottom, and 3" holes. Mounted to the top are eight capped 4 foot long 3" PVC pipes to dry 4 pairs of pants. For coats, there are four 4' long 3" PVC pipes each connecting to a 3" Tee which is reduced to 2" for the shoulder followed by 45 deg fitting that reduces to 18" of 1 -1/2" PVC pipe for the arms and then capped; imagine a stick figure. There will also be six capped 1-1/4" PVC pipes about a foot long for drying gloves and hoodies. The blower will be mounted in the middle facing down into the box to help distribute the air; perhaps with a cone mounted below it. The pipe mounting for pants and coats will most likely alternate with 2 coats and 2 pants on each side of the blower. I'm anticipating the need for about 700 or less holes. How do I calculate the best hole size to drill in the PVC pipe and fittings? I'm concerned that small holes could result in too fast of an air stream that might damage the PPE and/or cause too much back pressure and burn out the blower. And if the holes are too big, I'm concerned that not all PVC pipes will get sufficient airflow. I can always start with smaller holes and make them larger (700 more holes to drill out) but not conversely so I'm hoping to select the best size initially. I've attempted some calculations for 1/4", 5/16", 3/8", and 1/2" as I'm guessing these are most probable size have seen examples of "DIY PVC fire gear dryers" on the internet.; the results are velocity but not sure what makes sense. For simplicity I'm hoping to use the same hole size throughout all PVC pipes and fittings. Any suggestions would be appreciated, especially knowing how to calculate this seeing that my number of holes is just an estimate at this time. Thank you!

 

[dvd]

You might consider approaching you nearest engineering school and discussing this with a mechanical engineering professor. It might make a good project that the students could solve and apply some engineering theory to.

How did you decide on the blower size? It seems like you should start at the nozzle outlet flow and size back from there. Any thoughts on how you will deburr all of those drilled holes on the inside of the pipe?

Think about contacting a nozzle supplier. Spraying Systems sells air nozzles. A phone call with an applications engineer might provide some insights.

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WindJet air nozzles, air amplifiers and air knives for compressed air and blower air reduce operating costs for drying and blow-off applications.

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[MintJulep]

too much back pressure and burn out the blower.

That's probably not a concern, but you need to know the blower type, or just do a simple test.

The way the gear is put on will probably far outweigh the effect of hole size.