Steerpike wrote:IsaacKuo wrote:Basically, you are confusing temperature and heat. Of course your hard drives get warm out in the open--they have hardly any airflow to work with. Without any active airflow, the temperature will simply rise and rise until it's hot enough to generate convective airflow.
Hard drives can survive on convective airflow in open air, but it's not nearly as good as providing them some active airflow.
Isaac - I'm trying to be polite and open minded, allowing that you may be correct in some areas, but you seem to be taking a rather stubborn stance on this. I studied physics and maths to a rather ridiculous level in the past, and have worked with computers all my life, and have built more systems than I can count.
Polite or not, I'm being stubborn because you're simply wrong about this matter.
I have some systems at the moment with hard drives inside the case, others with the hard drives outside the case. All my cases rely only on the PSU for airflow, and my CPUs typically run around 40 deg C (P4 Northwoods, as mentioned; chosen for their low heat gen). I measure the drive temps on all my systems. The simple fact is, the hard drives that are inside my cases run warmer. I could aleviate that, of course, by increasing the air flow inside the computers, but that increases noise. By mounting the drives outside the case, as we all seem to agree, I can get away with zero airflow for the drives, and that can't be beat from a noise perspective.
You can get away with zero airflow, true, but it's worse than being inside the case from a noise perspective. The case can block a significant amount of noise, so a naked external drive is noisier.
So...what about temperatures? There are only two reasons why a hard drive would run warmer inside a case than outside:
1. Poor case design.
or
2. Builder error.
With a properly designed case and/or proper airflow design, the hard drive should receive fresh cool ambient air from outside. This air is exactly the same air that would cool a naked external drive, but with one difference--there's active airflow!
Now, you say that all these cases have a single exhaust (the PSU). I don't know why you mention this, because it has exactly nothing to do with the part of the airflow design which matters--where the hard drives are and where they get airflow from. In a well designed ATX case, the hard drives are in the front bottom, right behind the case's main intake. If the case is being cooled by just the PSU fan, then what happens is that the PSU creates negative air pressure within the case. Air leaks in wherever is available--mostly from the front air intake just in front of the hard drive.
Obviously, this isn't happening in your computers (if it were, then your hard drives would have better temps inside than outside). Why? Without more information, it's impossible to say. Maybe the hard drives are placed in a stupid place. Some ATX cases place the hard drives just underneath the 5.25" bays, well above the front intake. These hard drives can suffer from stagnant air, without even the opportunity for significant convection cooling. I've cooked enough hard drives to death in these cases to recognize the problem. Maybe the hard drives are in the proper location, but the front intake is too restrictive. Many ATX cases have a ridiculously restrictive front intake, so air will instead enter from other places if it has the chance.
Let's look at this from a very simplistic point of view - the hard drive is a source of heat (it consumes energy in the form of electricity and since it is not 100% efficient, it generates heat (which in the old days in England was measured in Joules, I think, but that's probably old fashioned by now)).
It matters HOW MUCH heat is generated. Heat is measured in joules, which is the modern day metric unit for energy. However, for our purposes it's the rate of heat generation which is more useful--watts (joules per second).
The percentage of efficiency only really matters for the PSU. Practically everything else in the computer is 100% efficient at generating heat. For a hard drive, some truly insignificant amount of energy theoretically might go into magnetizing the media, but for all practical purposes every joule consumed is turned into a joule of heat.
It therefore contributes energy inside the computer case, and therefore increases the net amount of heat inside the case (all other things being equal), and therefore, increases the cooling requirements inside the case - I don't think this can be disputed.
Yes, by an ignorably small amount.
This increased cooling requirement is typicaly accomodated by increased airflow through the computer, which means, more or faster fans.
No, actually the increased cooling requirement is typically accomodated by letting the rest of the computer run just barely warmer--not enough to matter.
See, you're looking at cooling requirements in the wrong way. It isn't a matter of running enough fans to remove a certain amount of joules per second. The simple fact is that a computer generating 150 joules per second WILL BE COOLED BY 150 joules per second. It's an unavoidable fact! No matter how much heat a computer generates and no matter how little fan generated airflow it has, it will reject exactly that much heat! Even with no fans at all!
No, it matter what the desired operating temperatures are. And this is where the particular properties of a hard drive are important--even though they need to be kept very cool, they themselves generate very little heat. Put a hard drive in a tube with a small amount of airflow and try to detect a difference in the temperature of the incoming air and the outgoing air. Good luck! No, you'd have better luck measuring the amount of power drawn by the hard drive and deducing from that how much heat it must be generating.
So, putting the hard drive in the computer's main airstream results in an insignificant increase in cooling requirements.
But don't take my word for it, just try it! You measure your CPU and PSU temperatures? How much difference is there when you remove the hard drives from the case?
