Since the last thread about memory contained some very interesting info about stuff not related to RAM, I thought I'd start a new thread on what I find to be another interesting topic:Computer case thermodynamicsMy questions:1) I see a lot of case manufacturer's putting a place for the PSU on the bottom of the case. What are the benefits of this?2) How does the air move about inside a case, what changes with side/front/top intake/blow fans - do side fans help?3) How to choose which fans blow and which ones suck?4) Also related, how do you know which HSF is best for your CPU, and will it fit your case?

1) I see a lot of case manufacturer's putting a place for the PSU on the bottom of the case. What are the benefits of this?

If I recall correctly (which I may not be), the BTX standard had the p/s at the bottom of the case. This is one reason why you see them there today. Many cases, such as my Silverstone TJ09, can run BTX boards in them...thus the bottom mounted p/s. BTX was supposed to supplant ATX as the "Next Great Case Standard" and that was over 10 years ago...and BTX has never really caught on.You can of course google around for various articles on this, but my opinion is that they want the p/s at the bottom to allow the critical components (cpu, mem, etc.) to be nearer the top, where (presumably) a blowhole fan would be located, or a, 120mm rear fan would located.Another (lesser) factor is the fact that the p/s weight at the bottom means the rig is less likely to tip over when kicked (such as when you read some of these hardware forum posts lately).Finally, I think there was an attempt to lessen cable clutter using the BTX setup.The thermodynamic stuff...the push vs. pull stuff...not my forte...I'll let others talk about that :D

A tower with at least 8 inches in width and with no side door fan should clear the CPU HSF.. Mine is 8.2"You may be able to skim by with just a touch less. My tower has a riser for the motherboard tray track mechanism which allows the entire motherboard to slip out the back of the tower on its tray for service but to be sure I would make sure you have a min 8" widthI prefer the PSU at the bottom of the tower.. although when I first saw this design my first thoughts were "heat rises" but after using the TJ series for 3 years I am happy with the design. The only thing I do not like about the design is the use of perf metal grills on the top (and the center fan in the earlier models of the TJ series) The tower had a perf metal grill in the center intake (inside the tower down by the HDD rack) which I completely removed. I left the top alone as to not destroy the esthetics however I would have much preferred Silverstone not use fine perf metal for those top fan grills as it does restrict airflow. Wire frame open grills are the best which is what the rear fan uses on that tower

I think the biggest advantage of having the PS mounted on the bottom is that it draws cooling air from outside (under) the case, and exhausts it out the back, so the PS is getting cooler air than a top-mount config where it draws already warmed air flowing inside the case.My CoolerMaster HAF932 can take the PS in either top or bottom, but with it in the bottom, I get to use a top-mounted 230mm exhaust fan where the PS would be. Given that heated gas rises, I like having a high-flow exhaust at the top.RegardsBob ScottColonel, USAF (ret)ATP IMEL Gulfstream II-III-IV-VColorado Springs, CO

I think the biggest advantage of having the PS mounted on the bottom is that it draws cooling air from outside (under) the case, and exhausts it out the back, so the PS is getting cooler air than a top-mount config where it draws already warmed air flowing inside the case.My CoolerMaster HAF932 can take the PS in either top or bottom, but with it in the bottom, I get to use a top-mounted 230mm exhaust fan where the PS would be. Given that heated gas rises, I like having a high-flow exhaust at the top.RegardsBob ScottColonel, USAF (ret)ATP IMEL Gulfstream II-III-IV-VColorado Springs, CO

I agree Bob and in that respect where the dual fan PSU is in use.. towers which use PSU's like that which intake from the bottom must also not be placed on deep carpet or anything that restricts that airflow underneath.But in my system, the PC Power and Cooling 750 does not use dual fans.. its simply a 80mm deep pitch exhaust fan. The PSU fan rarely kicks up as I always spec a solid overhead for the PSU (as I know you understand) specifically for that purpose.. better rail, high overhead = much less heat and noiseBut I can see the advantage as you pointed out with the PSU which incorporate dual fans

I agree Bob and in that respect where the dual fan PSU is in use.. towers which use PSU's like that which intake from the bottom must also not be placed on deep carpet or anything that restricts that airflow underneath.But in my system, the PC Power and Cooling 750 does not use dual fans.. its simply a 80mm deep pitch exhaust fan. The PSU fan rarely kicks up as I always spec a solid overhead for the PSU (as I know you understand) specifically for that purpose.. better rail, high overhead = much less heat and noiseBut I can see the advantage as you pointed out with the PSU which incorporate dual fans

Yeah, that's true...I have my case up about 24 inches off the (carpeted) floor. The amount of dirt/fuzz down at floor level, even with regular vacuuming, is eye-opening. Keeping the case up high keeps the dust bunnies from getting sucked into the PS inlet and also puts the relative heights of the various parts of the water cooling system in line so that the pump has very little head to work against.I have one of those PC Power and Cooling 750 Silencers in my secondary PC...come to think of it, I guess there is just the one (dead quiet) fan. I went with their 910W Silencer on the new build to preserve the option to SLI the video (for 3D shooters). It has a 120mm fan in the bottom and an 80mm backside one. And it's really quiet, too. I haven't had one of their supplies die on me yet, where I have smoked a couple of the Antecs I used to use.CheersBob ScottColonel, USAF (ret)ATP IMEL Gulfstream II-III-IV-VColorado Springs, CO

Since the last thread about memory contained some very interesting info about stuff not related to RAM, I thought I'd start a new thread on what I find to be another interesting topic:2) How does the air move about inside a case, what changes with side/front/top intake/blow fans - do side fans help?3) How to choose which fans blow and which ones suck?

Back to topic...as to which fans blow in and which out, I try to keep air flowing as much as possible in one general direction through the case. Right now I have 230mm intake fans in the lower front and side, and exhaust fans in the back (140mm) and top (230mm) of the case. The video card also exhausts a fairly good volume of air just below the back-mounted exhaust fan. If the case is screen-vented, balancing the fans (intake vs exhaust) is less of an issue than if your case is only aspirating via the fan openings. If you have some of your fans speed-controlled via the BIOS, keep in mind the effects that can have on in/outflow balance too.The side fans are good for insuring the mobo and its chipset is getting positive airflow. The memory DIMMs, voltage regulator, and southbridge heatsinks all need good direct flow across them, especially if your room temp runs on the warm side (i.e. above about 25 deg C/78 deg F). It's also good to have a fan blowing across HDDs, especially the higher performance drives like Velociraptors, as they do run on the warm side. My dual-core unit has a large HSF (a Tuniq tower with an internal 120mm fan), and it was critical to make sure it was blowing towards the rear exhaust fan to prevent it from working against the intake fans in the front of the case.I have, in the past, blown cigar smoke into the intake fans to watch flow through the case. If you have a plexiglass viewing port and a camera it can give some good insight into how air flows (or does not flow) through the box. If it's a fine cigar, a glass of 12-year-old scotch should be added to appropriately enhance the investigational process. :( CheersBob ScottColonel, USAF (ret)ATP IMEL Gulfstream II-III-IV-VColorado Springs, CO

Hmmmm that TJ case is pricey heheI spose you get what you pay for :)My case is from the first time I got my parts, AMD3700, asus a8n32sli deluxe.... Thermaltake TsunamiHere's the fans that I have in it.... I only have an arctic freezer pro in there but I'm not OCing the AMD6000So the side fan probably doesn't do much. The front low fan probably doesn't do much either cause the case design is restricting flow if you don't have the front panel completely openThe back of the case doesn't have those ring type exhaust panels like you recommend, it has little circular openings.

...The front low fan probably doesn't do much either cause the case design is restricting flow if you don't have the front panel completely open...

As far as I can see from the picture there are several horizontal holes on the front panel that seem to give a sufficient air intake. If you put your hand inside the case behind the hard disk section you should feel the air flow into the case. If not, try to clean the dust filter.

I have, in the past, blown cigar smoke into the intake fans to watch flow through the case. If you have a plexiglass viewing port and a camera it can give some good insight into how air flows (or does not flow) through the box. If it's a fine cigar, a glass of 12-year-old scotch should be added to appropriately enhance the investigational process.

Now THATS what I call an in-depth high tech investigation of field application vs theory in design :( Some may consider what you posted a joke.. in reality the 'puff' test it a great way to verify the aerodynamics of a tower which of course is much easier if the tower has a clear plex window in the door. For those who may not appreciate a fine cigar with the right scotch or in my case, cognac: http://www.regin.com/shop/smokepen.htmTo answer the questions above in the order they were asked... 1) I see a lot of case manufacturer's putting a place for the PSU on the bottom of the case. What are the benefits of this?Answered above.. You must take into consideration all the variables around the case you wish to purchase and the PSU itself. No 'one' design is perfect. As Bob mentioned above the dust bunnies can be vacuumed into the tower very quickly with 2 fan PSU's if the tower is not located off the ground where that dust collects which is another reason why I prefer the PC P&C PSU. Single fan, no intake on the bottom. That does not mean its the best solution If the PSU was mounted in the top of the tower that extra fan in the PSU can act as a heat remover too as it would draw air above the HSF and expel it out the back. 2) How does the air move about inside a case, what changes with side/front/top intake/blow fans - do side fans help?Again., this is something that comes with the total design of the tower and how you intend to use it. You will not be using any tower with a door side fan which obstructs the door from closing due to the size of the selected HSF. Most high-end coolers such ast the TRUE, the IFX 14, etc are too large to allow a fan mounted on the door in the same area they are located. There are towers that have fans on the door which cool the video card area and are out of the way of the HSF. This is all something YOU as the builder must figure out using the PDF mechanical drawings of the HSF and tower3) How to choose which fans blow and which ones suck?When it comes to flow, each tower design has its own characteristics around that. The final build may demand a change in how the towers original fans were positioned to push air, (in or out). This is something the builder must figure out.. Its really not that hard and a matter of common sense with some help from the temp sensors in the system and experimenting with changes in flow.4) Also related, how do you know which HSF is best for your CPU, and will it fit your case?As I pointed out above,... 8 inch or greater width should handle any high end air cooler. In order to make some sense of what I posted above I will explain what I did with the Silverstone towers I use.This is going to be long winded but perhaps me explaining what I did may help someone else make decisions and get ideas on what to look forFirst of all.. let me preface this by saying that I was NOT AFTER the most efficient, most

Hmmmm that TJ case is pricey hehe

Not if you run 2 or 3 builds through it. Then you get your money's worth. You know, PC Power & Cooling used to make cases. I still have a PC Power & Cooling mid-tower that I bought about 10 years ago, and I could probably drive my 4x4 over it, use it as a ramp to change oil, etc. Well, maybe not. But you get the idea. Today's cases, like your Tsunami, have much better provision for fans than do the old cases though.

Mace makes a good point. Those towers I have will probably be around after I