Why Radiators in the Front of the Case?

[Nanook]

With air flow from front to back isn't it just dumping all the heat blown off the rad to right inside the case?

[TempestCatto]

It's to give it fresh, cool air and give your CPU or GPU an overall cooler temp under load. The heat dumping into the case shouldn't be too much of an issue if you have good exhaust. That or if both the CPU and GPU are water cooled. That combined heat, even under full load, still shouldn't be much of an issue to the rest of the parts. It's really no different than having both CPU and GPU air cooled and having them run at full tilt. They're still dumping massive amounts of heat inside the case. Just make sure you have a way for that heat to escape is all.

[GhostRoadieBL]

depends on the priority parts needing cooling. 

so one of the laws of thermodynamics (paraphrasing) is the greater the difference in temperature the greater the heat transfer. If your CPU is priority for cooling you want the greatest difference in temperature between the air entering the rad and the liquid inside so you transfer the most heat to the air. the rest of your components inside the case which don't have radiators or big heatsinks required will less efficiently transfer their heat but it will still happen if there is a difference in temperature between the air in the case and the component touching the air, just less than if it was a lower temperature. 

Same with GPUs, the less heat you have in the air around the GPU the larger the difference in temperature causing the most efficient heat transfer. 

 

motherboard components can happily cruise along at 50+C which will still be around the temperature of the air coming out of a heavily loaded radiator and any air temp below that will still cool the components 

[Arrogath]

Basically TLDR version of all these explanations, as long as the air moves fast enough the actual temperature bump to internal components isn’t enough to matter since your already water cooling the important parts

[GhostRoadieBL]

5 minutes ago, Caroline said:

The same is applied to cars, the radiator goes on the front to have a fresh air intake, put it on the back and your engine will burn.

 

if your case has decent airflow then that hot air will be sucked by the rear/top exhaust fans and blown out of the computer in no time, remember hot air rises so most of it won't be catched by the GPU fans

this is partly true but not so much.  cars specifically tend to have radiators in the front because the car is intended to move that direction through the air so you are getting "free" cooling simply by air moving across and into the engine bay at the front, the VW beetle had a rear engine air cooled (no rad) and drive just fine because it scooped air from under and beside the car to cool the engine bay. Supercars have radiators anywhere you can put them based on weight distribution and airflow at speed, nothing to do with "fresh air"

 

natural convection (hot air rises) is only effective in a static air situation where the energy being put into the air (entropy) by the higher temperature surface causes the air to expand passing energy onto lower temperature air, typically "up". Forced convection which occurs when lower temperature air is forced across a hotter surface and is constantly replacing the heated air with lower temperature air is what you are talking about in computer cases, if you have a fan "sucking" air out of the case any air will move towards that fan to fill in the negative pressure zone it is creating regardless of direction. 

[Nanook]

4 minutes ago, Arrogath said:

Basically TLDR version of all these explanations, as long as the air moves fast enough the actual temperature bump to internal components isn’t enough to matter since your already water cooling the important parts

I get that hot air from the rad dumping into the case is probably not going to make a big difference, but it just seems like cases should be designed differently due to this? Maybe there should be room for a 360, 280, or 240 including fans in the rear to exhaust directly into the atmosphere.

[Arrogath]

Just now, Nanook said:

I get that hot air from the rad dumping into the case is probably not going to make a big difference, but it just seems like cases should be designed differently due to this? Maybe there should be room for a 360, 280, or 240 including fans in the rear to exhaust directly into the atmosphere.

Problem with that idea is the rear IO and psu eats up all that space so it doesn’t end up being practical without a chunky case or weird motherboard orientation.

 

Chimney style cases where your fresh intake goes from bottom up and exits through the radiator somewhat address your concern. Issue is you have to choose between better cooling at the radiator or marginally better case air temperature.

 

You could run your radiator loop air in a completely separate compartment but once again it’s a matter of space and case size for marginal benefits 

[unholy_walrus]

I won't pretend to know the science of it, but I do know that even with a 240 & 360 rads set as intakes and a single 120mm fan as an exhaust, the internal case temp won't reach even 40c during load at 25c ambient temp (Define S). Setting all rads as intakes has had only positive effects when running both cpu & gpu under water, based on my experience in the past few years. I don't mind having a very slightly higher case temp if as a result the liquid temp is lower.

[Mick Naughty]

I never put the rad in the front. Unless I’m desperate. 
The rads still get fresh air so it isn’t a concern. And no heating up my case or the parts inside from all the hot air. 
The way it should be. 

[unholy_walrus]

4 hours ago, Mick Naughty said:

I never put the rad in the front. Unless I’m desperate. 
The rads still get fresh air so it isn’t a concern. And no heating up my case or the parts inside from all the hot air. 
The way it should be. 

There is no "hot air". I wish I could find where this whole concept of "having rads as intakes is bad" was investigated and debunked, because I know I've seen that just a while back. I'd be willing to bet that even in a fairly extreme case such as mine the effect to case temps is mininmal, even negligible. What I can say personally is that when I tested 240 rad front intake-360 rad top exhaust-120 fan back exhaust vs 240 rad front intake-360 rad top intake, 120 fan back exhaust, even when stressing both the cpu and gpu the difference in MB temps & a case temp probe was negligible. Hardware used was a GTX 1080 & a 4770k @1.41v, fans at around 800-1k rpm. Having said that, I did see enough of an improvement on water temp on the second configuration, though I'm aware that my testing was absolutely inadequate, thus I won't make any absolute claims here. It was enough for me to choose that configuration for daily use though.

 

What do you mean by "fresh air"? 

[Mick Naughty]

6 hours ago, unholy_walrus said:

There is no "hot air". I wish I could find where this whole concept of "having rads as intakes is bad" was investigated and debunked, because I know I've seen that just a while back. I'd be willing to bet that even in a fairly extreme case such as mine the effect to case temps is mininmal, even negligible. What I can say personally is that when I tested 240 rad front intake-360 rad top exhaust-120 fan back exhaust vs 240 rad front intake-360 rad top intake, 120 fan back exhaust, even when stressing both the cpu and gpu the difference in MB temps & a case temp probe was negligible. Hardware used was a GTX 1080 & a 4770k @1.41v, fans at around 800-1k rpm. Having said that, I did see enough of an improvement on water temp on the second configuration, though I'm aware that my testing was absolutely inadequate, thus I won't make any absolute claims here. It was enough for me to choose that configuration for daily use though.

 

What do you mean by "fresh air"? 

The air coming out after the rad is hot. That isn’t questionable. So thus fresh air would be ambient air from outside the case. 
 

There are factors involved and if we aren’t taking into consideration sure, anything will work. 

[unholy_walrus]

On 9/4/2020 at 8:16 PM, Mick Naughty said:

The air coming out after the rad is hot. That isn’t questionable. So thus fresh air would be ambient air from outside the case. 
 

There are factors involved and if we aren’t taking into consideration sure, anything will work. 

1) Define "hot". Sure, the radiator heats the air to an extent. That's how radiators work. The point is that (at least I claim) the effect on internal component temps is minimal.

2) What factors did I not take into account? Saying something isn't being taken into consideration and then not mentioning what that something is - that's not great. Note that while I would never claim that my testing is anywhere near even adequate, I do think that if running rads at intakes, dumping all that "hot" air into the case, was really that bad temp-wise, I should've seen at least some indication of it during my fairly extensive run of stressing, gaming, movies, work etc. Obviously this isn't the first time either, and I've yet to see a "hot" internal temps -scenario.

 

To be clear - I'm not claiming there is no difference. I'm saying the difference in internal temps is very small. However, having thought about it, I think I am ready to make the claim that having radiators as intakes is slightly more benefitial as a whole (obviously doesn't apply to every case). 

 

On 9/4/2020 at 8:16 PM, Mick Naughty said:

The air coming out after the rad is hot. That isn’t questionable. So thus fresh air would be ambient air from outside the case. 
 

 

I'm just trying to make sure I don't misunderstand - I'm not sure if I'm getting this right. It seems to me that you're saying that having a rad as an intake in the front is bad, but on the top it's okay? I really don't think that's what you're saying, hence why I asked about this. I mean the first post was;

 

On 9/4/2020 at 8:38 AM, Mick Naughty said:

I never put the rad in the front. Unless I’m desperate. 
The rads still get fresh air so it isn’t a concern. And no heating up my case or the parts inside from all the hot air. 
The way it should be. 

Now, the only two options I see here are that you're saying what I discussed just now, or that a) you're running rads outside the case a'la MoRa or b) you have a case with a basement for example, that allows you to run them as intakes without effecting the main compartment. If either a or b is correct, that would've been really good to know as it would've made this post much, much less confusing.

 

I wouldn't be surprised if much of this is just misunderstanding either. If that's the case, I'm sorry.

[Mick Naughty]

5 hours ago, unholy_walrus said:

1) Define "hot". Sure, the radiator heats the air to an extent. That's how radiators work. The point is that (at least I claim) the effect on internal component temps is minimal.

2) What factors did I not take into account? Saying something isn't being taken into consideration and then not mentioning what that something is - that's not great. Note that while I would never claim that my testing is anywhere near even adequate, I do think that if running rads at intakes, dumping all that "hot" air into the case, was really that bad temp-wise, I should've seen at least some indication of it during my fairly extensive run of stressing, gaming, movies, work etc. Obviously this isn't the first time either, and I've yet to see a "hot" internal temps -scenario.

 

To be clear - I'm not claiming there is no difference. I'm saying the difference in internal temps is very small. However, having thought about it, I think I am ready to make the claim that having radiators as intakes is slightly more benefitial as a whole (obviously doesn't apply to every case). 

 

I'm just trying to make sure I don't misunderstand - I'm not sure if I'm getting this right. It seems to me that you're saying that having a rad as an intake in the front is bad, but on the top it's okay? I really don't think that's what you're saying, hence why I asked about this. I mean the first post was;

 

Now, the only two options I see here are that you're saying what I discussed just now, or that a) you're running rads outside the case a'la MoRa or b) you have a case with a basement for example, that allows you to run them as intakes without effecting the main compartment. If either a or b is correct, that would've been really good to know as it would've made this post much, much less confusing.

 

I wouldn't be surprised if much of this is just misunderstanding either. If that's the case, I'm sorry.

You said with you’re test using a 1080 and 4770k and it didn’t make a difference. I wouldn’t expect it to given the hardware used. But I don’t know the case, the rads, fan or pump. Or the speeds in which they are used. Or the ambient temps. Or the temp of the vrm or any other component inside the case. 
 

if you have a board full of sensors and other hardware like nvme’s and capture cards that benefit from cooler air, it becomes a factor. Not just the basic claim of my cpu and gpu temps didn’t change. 

I can run my 4770k on prime95 and not go over 40c if I’m just throwing out numbers. I’m sure I can do the same with a rad as intake but that isn’t the point overall. 
 

But I run all my rads as exhaust. Would prefer not to dump additional heat into the case and impede airflow. And also not have components running hotter than my cpu when it isn’t needed and easily avoided. Asi helps maintain positive pressure given the slight restriction the rads pose.