Sunday, June 28, 2009

Fans and Cooling (One Step Forward, Two Back)

Most things never turn out as planned - which happens to be the case with the fan / duct ideas... :-(

Anyway - the plan was something like the following...



The standard axial-flow type computer fan would be used to push the air through the 1U power supply - sucking air across the rest of the main board...
Initial step was to build some ducting...

I needed a duct to connect the angled fan onto the 100 x 40 mm sized power supply.

Initial thoughts were to make a duct out of material - and gather it around the fan and the power supply. Like the following



Didnt really seem right...

So I went for something more solid - started constructing shapes out of cardboard cereal boxes... cutting, folding and taping



These models gave a much better feel - so I started towards turning these shapes into something more permanent. Initial attempts were with paper mache (or however it is spelt) - but using material instead of paper. OK but a bit flimsy.



Next attempt moved to using standard white hobby glue with the material - giving it a week to dry results in a pretty strong, slightly flexible duct. Definitely OK for the job.



Now it comes to the problems...

I now connected up the fans, with the ducting, and the power supply.
Pretty dismal airflow - no where near what was happening with the tiny 9000 rpm 40 mm fans originally in the power supply.

Pulling things apart further, I found that even the fan simply sitting in the metal frame had pretty poor airflow - removing the frame, and airflow was fine.



Some Google-ing shows up that the standard axial fan is no good at handling air pressure.
Putting any blockage in the way, means that the fan doesnt want to function well.
Options are to put some kinds of vanes into the axial fan design, or to go with a centrifugal fan, like this used in laptops...

Just as an experiment, I took an old noisy axial fan, and tried to convert it into a centrifugal fan...



Basically you block off the side where the air flows out, put a shroud around the air intake side of the fan, and cut away one side of the existing fan housing. It actually worked surprisingly well - has a reasonable airflow out the side...

Anyway - seems like I am back to the drawing board when it comes to the overall design for this version 2 layout... need to work out how this airflow and cooling is really going to work. Will require some field trips to see what kinds of low noise fans (axial, centrifugal) I can purchase....

 

1 comment:

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