Not really sure whether it will work or not ... but one thing for sure if the air is exhaust at the bottom will rise and used by the intake fan again in cooling off the HDD...

so will it be efficient to make the exhaust fan set below the intake fan ?

one thing for sure.......... blow out fan must at the top or must be higher than intake fan

Yes it can destroy ur hdd only if u dun ground ur hdd(non-metal rack)....i dun think tht config utilises air to the max efficiency.....i suggest mounting the air outlet at the back of ur casing...the air would pass by the largest hdd area plus ur mobo components on the way to the back....dust problem....it depends on ur place...like air cond/no air cond...windows open/close...distance from high  traffic roads..etc.

Yes the higher the psu power...the more stuffs u can put not oni fans...go use a psu requirement calculator(easily found by google) to compute out ur max power and the power currently u using.

cant get wut u try to say.. or maybe my english suck 
reexplain please...

why arr?

u dont go to school ka    joking 
actually hot air will go up, dont u remember study this at school ???

its a no point mode, as the hot air and cold air keep circulating internally and externally...

@2uk3y thanks for reminding me hahhahha

so, i need to change the fans place???
mean.. the blow in below... and the blow out upper ??

some picture i think can give u some idea....

some picture i think can give u some idea....

yeah...it shud work better....bout dust...positive pressure inside collects lesser dust compared to negative pressure

so tomolo can la show ur rig picture what have u done....
real picture, easy to discribe lol

ehmm bout the heat movemnt.. do you think can affect my hdds???

meaning...?
u mean air movement?

fantagero, thats an interesting method you got there.

there are several problems of course. it would work, so long as there is a temperature difference, heat would be transfered [ie. cold air cools the right side of the HDD, the right side is cooler than the left, so heat from the left side moves right]. it would be terribly INefficient. there is too little surface area [as someone mentioned above]. if im not mistaken, the majority of the heat in a HDD is passed through the sides and not the top/bottom plates, so id assume fixing heatsinks to right side to work?

you thought of this to try to 'fix' the dust problem. unless you have a fully enclosed [or close to fully enclosed ] subsystem, the intake fan is bound to blow air all over the place. some of that airflow is bound to get further into your casing, carrying dust along with it. in an enclosed environment [ie. a tunnel], you'd only need one fan, either at the front or at the other end.

i really find the idea of a fully IN-OUT 'chamber' interesting! but at the end of the day, i think fan filters are just most practical!

if u afraid of ur samsung HDD will spoilt.. just added HDD cooler wit setup that already shown to u..

fanta.. why u dont put the red blow in fan as same level as the blue blow out fan? u put like that i think the cool air will be sucked out by the green blow out fan before it touched the HDD.. 

if u afraid of ur samsung HDD will spoilt.. just added HDD cooler wit setup that already shown to u..

the heat movemnt from left to right

so i guess..put on both the right side fans to blow in..

and the rear & left panel fan to blow out~

this should be ok.,

Ok oso la...boleh tahan....by the way...how many hdds do u have? its best of u space them max apart and it will be cooler ade without any fans....i used to place a 3.5 in front of the hdd but now after spacing no need ade....temp hovers nicely between 35 and 40

yeah so far i think that is the best way 

btw what is that plastic infront of ur fan ???? what for ??? 

u mean the cooper cooler???
i got 2 hdd/s the top and the bottom.. thecenter is for floopy.. unfortunately cant remove it. as the floppy hole is permanently at the fron panel...

take out the floppy drive la.. less people using floppy these years

i took it out edi, summore increasing my casing weight load since it all steel, take it out, u have more air space between ur harddisks.

thanks for the idea man...... 
i've thought of this b4.. but afraid if i might use it..
can i just use usb floppy for laptop ??

Harddisk - Heatsink mod
What you need:
1. A hard disk (duh!)
2. Few aluminum heatsinks (duh duh!). Aluminum dissipates heat better.
3. Thermal paste.
I used the paste I got with SI-120.
4. Isopropyl alcohol.
I used spirit used by doctors. May not be as good as IPA but does
the job and is better than using after-shaves/nail polish removers.
5. Cotton swabs (without your earwax ofcourse)
6. Hammer. So you can smash your head if your HDD crashes.

What you get:
A cooler hard disk which will be grateful to you for implementing this mod.

I have 3 HDDs in my cabinet and inspite of managing the cable to increase the airflow, the HDD temps always reached 47-48 deg C. Sometimes even 50. Too hot for me. Connecting the HDDs in front of the 120mm front intake didn't help either as the temps only dipped about a couple of degrees.

During one of my extensive weekend cleaning sessions, I noticed the smooth metal surface on the HDDs (Hitachis in particular as the label is very small and stuck at the bottom, leaving ample clean, smooth metal surface for our use) and thought why not attach a few heatsinks to try and dissipate the heat. You can remove the labels if you don't have enough space to attach the heatsinks but make sure you know what you are doing. Removing the lables may void your warranty.

1. Take a clean cotton swab, dip it in IPA (spirit) and clean the
whole metal surface of the HDD. Use the other dry end to soak
up the remaining fluid. Do the same for the heatsink bottom.

2. Squeeze a tiny amount of the thermal paste on the bottom of the
heatsink and press (and I mean gently. Don't press it like you are
fixing postage stamps.) it on to the metal surface of the HDD. Twist
the heatsink in both directions to remove any air bubbles and to
spread the thermal paste.

3. Do this for all other heatsinks.

4. I've arranged the heatsinks at an angle as this should create some
turbulence and increase the heatsink surface area coming in contact
with air. If you fix the heatsinks in a straight line, air will just flow past
the heatsinks without coming much in contact with the HS surfaces,
thus reducing the heat dessipation.

5. Repeat the above steps for all HDDs.

Source:LINK

topic starter. your design either circulates the air in and out and in and out or its not efficient in cooling. it depends on how you want to design the cooling actually. normally if you want to cool the hot hard disk. other than wc, passive cooling is too hard to cool it up. frankly if you have alot of hard disk. try placing them close together and fan them directly. any fan will do, but do remind it has to have a high preassure and prefereable high cfm to maximise cooling. my hard disk mod is the same as your latest one. but mine is a large 12cm nidec beta V at one side while another delta in front of the casing. exhausting hot air is not a concern to me as my casing is naked. for the case of dust. i think there is not much you can do about it. if you're in an air con room then its good as the air con will filter most of the dust. but if you're on the plain ceiling fan, i suggest you install a air filter. its cheap and keeps you from doing daily house keeping on the pc. my friend is currently trying out another method of reducing dust without the usage of filter. he's thinking on using static energy but its kinda dangerous as  electrical component might get faulty due to it.

if your place your hardware too far apart and cooled on a parallel air way. then its not good. since you have plenty of space tryblowing it. if dust is your concern, you can try salvaging old heat sink and then blow or suck on the heat sink attached to the hard disk. work fine for me.
always remember hot air rises. cold air is always at the bottom. to force air thru tight places, high pressure fans are required( fast spinning fans) high cfms fan work best in moderating and removing heat fast.