I want to build a DIY air purifying system that incorporates a HEPA filter.
I'm a bit confused on the different types of fans available for filtration purposes.
When I tried to learn more about fans, I come across terminologies like "centrifugal" and "axial". The way I understand, axial fans are the common type that we are all familiar with, it can move lot of air but cannot generate high static pressure.
But I'm a bit fuzzy on the terms "centrifugal", "squirrel cage", "blower". Are they all pretty much the same thing? Any of those would be suitable for a HEPA filter provided the static pressure is sufficient right? Do you know what pressure is sufficient for a HEPA filter (assuming clean filter, just need a rough ballpark idea)
I do know what you are talking about and yes I could explain them but going through all the fans, teaching you how to read the grafs and understanding the terms is a several year project. I highly recommend you use your search engine and look at each of the items you mentioned and many many more thing you will find. There are some major flow restrictions with some of the HEPA filters so you need to know what you are using and the square area of the filter before you can size the fan. Have fun and good luck.
Yes, you are certainly confused. The first thing is what relation does your project have to Arduino?
Second is you NEVER try to pressure air through a filter, you ALWAYS pull the air through a filter, unless you enjoy cleaning a fan every time you change the filter. Moreover, a pressure fan will cavitate at a certain pressure and not be able to go beyond that limit, but will spin faster and faster. Suction will suck to a limit and continue to suck even though a vacuum is being produced.
If you are confused, study a commercial version of your project.
I did try to study a commercial version, still a bit confused:
I can see that it's a squirrel cage type fan. And yes, I see that it pull the air through the filter. But it still doesn't tell me what kind of fans I need to search for (say, on Digikeys) when building my own. I just need some right terminologies to get started so I can do my own research.
Not sure I understand this:
Moreover, a pressure fan will cavitate at a certain pressure and not be able to go beyond that limit, but will spin faster and faster. Suction will suck to a limit and continue to suck even though a vacuum is being produced.
I thought if the filter is used up and there's a lot of obstruction, it will cause the fan to draw more current and pose a fire risk. That's why I want to be able to measure the pressure drop before and after the filter. And there is where the Arduino comes into play. Might also need it to control the fan speed.
Can you start off by answer that "yes/no" question?
If you can provide some general terminologies, that'll help me get started with my own research. For instance, I did break apart a commercial air purifier and see that the fan is a custom made "squirrel type" fan (or so I think), but it doesn't tell me what kind of search terms I should use when searching for the type of fan that'll generate the pressure needed.
Thanks
[quote="paulwece, post:4, topic:1104128"]
I thought if the filter is used up and there's a lot of obstruction, it will cause the fan to draw more current and pose a fire risk.
A fan draws current when it is moving air. IF it can't move air, why would it draw more current? IT is equivalent to a motor with no fan. A fan moves air because the pressure on one side of the fan is less than on the other side of the fan. If the pressure is equal, no air moves and no work is done.
All HVAC systems use squirrel cage fans because they are solidly constructed and designed so nothing will flop around, like fans with blades. Also much easier to balance than fan blades. Fan blade must be balanced both for weight and for identical pitch of all blades. A squirrel cage fan only needs to be weight balanced.
A motor with a bladed fan needs thrust bearings because of the axial load of the fan. A squirrel cage fan uses only the radial bearings that are part of the motor.
Don't fool yourself into thinking that the result will be as efficient, safe, or as cost-effective as a certified, professionally designed, commercially produced fan + HEPA filter unit.