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General discussion

Airflow Direction of CPU Fan

by rfn109 Jun 29, 2009 7:58PM PDT

This is all about my old Dell Dimension 4400's design. I noticed that there were only two fans installed on my computer - a CPU Fan installed at the back of the casing with a duct heading towards the heat sink (no fan on top of the heat sink) and the other is the exhaust fan of my PSU - all are exhaust, meaning, they all pull hot air out. With this kind of set-up, I'm always having clogged optical drives because there is not even one fan pushing fresh air in nor any ventilation holes in it. Recently, after upgrading my processor, I had my CPU Fan faced the inner side so as to blow fresh air into the heat sink. I have also installed some kind of plastic mesh on the grilles of the casing to filter out dirt and dust from the outside. But I have some reservations about this set-up because it's only right below the PSU Fan which blows out hot air. Because of the proximity of these two fans, I'm afraid that the CPU Fan would just be recirculating in the hot air being exhausted by the PSU Fan.

My question is: Am I doing the right thing or am I ruining Dell's design regarding heat management?

Discussion is locked

3 Posts
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Cooling system
by Willy Jun 30, 2009 10:21PM PDT

This is the way it works for Dell and any other typical system. Fresh air in frt. and exhaust air to the rear. Dell does this using only the 2-fans you mentioned. While both are at the rear, they do draw in fresh air as they exceed the threshold of the inside capacity and provide "air flow" from frt to rear.

You are defeating the Dell design if a mesh or air cleaner arrangement as that will reduce air flow. Basically restricting the best level of air flow. You can increase air flow(CFM) by using larger fans and/or increased RPM or yet more fans. The ducting Dell uses a more direct capture as the fan isn't on the cpu yet can still does the job. However use of less fans is cost-effective in corporate thinking.

FYI- considering the life cycle of fans, Dell suspects they're fans will still work for the typical service of a system, around 3+yrs. However, cleaning a fan will help longevity.

tada -----Willy Happy

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Higher-CFM fan for Dell M4400 laptop?
by seth.teller Jul 15, 2010 4:10AM PDT

We have several Dell M4400 laptops running outdoors
in hot sun. They're in a ventilated cabinet, but are
still running too hot, and throttling their CPU speeds.
We'd like to replace the stock internal CPU fan:
MCF-J13BM05
5VDC, 0.3A
6.1CFM
Hangzhou Toshiba Home Technology Electronics Co
Rev A00
with something that will move more air through the
laptop. Can someone suggest a drop-in replacement
for the stock fan? We don't care about noise, and
are willing to dedicate a few more watts to the fan
if we could get better cooling.

Thanks,

Seth Teller
teller@mit.edu

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M4400 fans
by TimAnderson22 Nov 13, 2010 3:06AM PST

Don't know if you've solved this yet, but it's been my experience that Toshiba Home Tech fans are usually over-rated and perform poorly compared to other fans. There is no way I'll be convinced that the CPU fan will move 6.1CFM at only 0.3A.

A couple of suggestions:
1. Use one of those laptop platforms with the built in fans to blow more air on the bottom of the laptop and into the air intakes.
2. Look for a fan by Sunon, ForceCon, or other manufacturer that actually moves more air than the Toshiba and replace the fan. I've seen quite a bit of variance in output for the same Dell p/n by different suppliers. E.g. for the Dell E1705 graphics fan, I've seen outputs ranging from 0.28A & 3.1CFM up to 0.4A & 6CFM, all with the same Dell p/n.
3. If you're brave (or stupid) like me, get a slightly larger fan and modify it or the case so it will fit.
4. Move the laptop closer to the cabinet ventilation openings.
5. Increase the airflow through the ventilated cabinet.
6. Duct outside air directly to the laptop instead of drawing in air circulating through the cabinet.
7. Use a portable air conditioning unit (Home Depot has them) to provide chilled air to the cabinet.

Good luck,
Tim

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