higher cfm fans on heatercore-worth it??
 

hey all.i have a line on cheap delta 120`s.1.2 amps 12.6 watts.would there be a temp decrease on my my watersetup ,using these fans :confused:
i have right now 2x panaflos.
1 high and 1 med on my heatercore
so i would be going from approx 170 cfm total airflow thru 86`chevette heatercore,all the way up to 300
i have a rheobus which i could turn them down,to be quiet,but still have more air flow
thnx for input

more airflow = lower temps (up to a point).

The c/w will respond to increased air flow more so than increased water flow. Look here at graphs 14 & 15. If noise is a issue consider 2 120mm fans in a push pull setup and run them @ 7v. If it is not consider 2 @ 12v for some serious flow.

thnx for replies.i have my panaflos setup right now in a push pull.68 cfm pushing
105 cfm pulling.they are turned down a litlle but not much

If you can cope with the niose and want more cfm you can use the -12v line from your psu (pin2, blue pin on ATX connector) with the +3.3v, +5v or +12v to get a pd increase. This gives 15.3v, 17v or 24v. Normal 12v fans *might* burn out after a while at 24v but its likely they wont, I have tested it with a 80mm ystech and it works well and pushes a very high cfm. There is only one warning though, most ATX psus have weak -12v rails, and weaker -5v rails. Measure the current the mobo is using on -12v to amke sure there is enough spare, or disconnect that pin from the mobo. You could be able to run 3 or 4 80mm fans from -12v but mot many more.

Watch the amperage draw on that -12V line. You could burn out your PSU by drawing too much.

I only intend to run a single 172mm fan from -12/+12 which draws 0.5A at most my psu can do 1A. Im hoping I dont need to worry about start up current too much

STatic pressure ratings on the fans in question are more important than CFM ratings. Remember that a rad is fairly high restriction, so it is possible that a higher pressure lower CFM fan might end up moving more air than a low pressure high CFM fan in actual practice. Generally speaking, thicker fans are better than thin ones, but you really have to look at the PQ graphs to see which is better for sure.

Also note that there is a diminishing returns factor involved, it is possible that if you already have good cooling with your panaflos, you might not gain all that much more with the deltas.

Gooserider

with a single fan chevette heatercore I dropped 5-6C by adding a second fan NEXT to the fan I had on it...not on the other side, NEXT to it. pretty awesome IMO, I think the flow from the one cancels the deadzone from the other

heatercores are pretty unrestrictive...

he was referring to airflow, not waterflow.

hm I thought they were pretty decent with air too, but I might be wrong.

My 172mm fan is 50mm thick. I am hoping it is good enough to push lots of air through two heatercores, one behind the other. Both heatercores are exactly the same. Would putting another fan (well, 4 normal 92mm's) between both heatercores help much?

turn a fan on and let it blow on your hand. then put it next to your rad and feel again. big difference. obviously this varies with different styles / thicknesses of radiators, but a typical 2-inch thick heater core is very restrictive to airflow.

kbn, im not sure if it would be any better than one core and the fan. the added flow restriction (more tubing + a second core) and decreased air flowing through the cores in that arrangement may offset any gains having a second radiator would have. you are free to try though and let us know how it goes lol.

Not really. What you did was place two fans in series, which (almost) doubles the static pressure of a single fan. Because you had a higher SP, the airflow was greater. The standards for fans are that putting fans in series keeps the same free air volume, but increases the maximum static pressure. Putting fans in parallel increases the free air volume, but keeps the same pressure.

However, putting two fans right next to each other is usually much less efficient than the theoretical maximum. The first fan feeds turbulent air into the second fan, reducing it's efficiency and causing increased noise. It would be much better if there was an inch or two worth of shroud between the fans so that the air from the first fan has a chance to straighten out and become non-turbulent before it enters the second fan.

According to what I've read, of the three possible arrangements of two fans and a rad, and assuming there are few or no airleaks between the fans and the rad, the best is one fan on each side of the rad (push / pull). Next is two fans pulling, followed by two fans pushing. In each case, having a 1-2" shroud between the fans, and between the rad and the fans will improve the airflow, and reduce the noise level.

BTW, a shroud is the ONLY way to effectively kill the "dead spot" on the rad face. (and a little rad like the chevette needs all the help it can get!)

Gooserider