couple questions about HDD cooler and PSU

[guppie]

I'm trying to increase case flow on a budget. I currently have 2 sunon 80mm fans (mid-rear and lower-front), Sunon 80mm PSU, and HDD 5.25" bay cooler. Couple of questions that some of you might be able to help me with.

1.) what is a reasonable approximation of cfm for HDD bay cooler? It has 3 small (i think40mm) fans. You think 20cfm total is about right?

2.) How important is it that I have my 7200 RPM drive (main drive) being cooled by the HDD cooler? I currently don't have anything behind the HDD cooler, so its just blowing in cool air near the top toward the CPU, but its not alot...

3.) Although there is an 80mm fan in the PSU, is that still considered to be sucking 36cfm out even though its being obstructed by its own case and all the circuitry inside?

4.) Does this sound like a good idea? I am going to move the front-lower 80mm fan and mount that directly under the other 80mm fan in mid-rear (2 mid-rear fans) and then mount a Sunon 120mm fan in lower-front (84cfm). About 105cfm in/108cfm out...??? What do you think?

Remember, I'm on a budget and recycling the current 80mm fans it themost economical.

[guppie]

dang! Someone please (at least) answer Question 3. Should this fan be included in the overall estimation of cfm in = cfm out?

[Punk]

1) ya, around 20CFM sounds right, but i've seen HDD bay coolers go up to 32CFM

2) Depends how hot your HDD gets. My maxtor 7200rpm 30.7GB HDD doesn't even get warm

3) i dont know

4) ya, sounds good! the more fans and air flow the better

[Owenator]

Kudos, your questions are well thought out you are doing a great job on your own!

According to what I have read on fans (from teh manufacturer's web site) the cfm rating is for no (zero) resistance to flow. Any thing that gets in the way of the fans intake or exhaust can reduce the flow the fan puts out. The good news is that all of your fans probably have some sort of flow resistance due to fan grills case openings etc which means you can use the cfm ratings and not be to off on your calculations. I think you have it balanced very well. One thing I have noticed is that depending of in vs out flow there can be sound generated because the outlet fans are either being held back or forced to run faster by the in fans. I also se this if the in fans are too small for the out fans but not near as much as if the case is 'pressureized' by more in than out.

My $0.02

O