# [SOLVED]Radiator size discussion and Request for Opinions

#### Imacflier

##### Distinguished
Hi, Guys!

Radiators: the LOWEST temperature a passive, i.e., not refrigerated, radiator can cool to is equal to the temperature of the air passing over its fins.
That statement (which was not obvious to me initially) has the consequence that once you have enough radiator fin volume, adding more is just a waste of money.
Definition: Radiator Fin Volume. This is a calculated number I made up (so take it with a grain of salt) to compare radiators of varying sizes an numbers. It assumes
that all radiator fins are equivalent (which is false on its face). It is calculated by multiplying the length times the width of the radiator opening times the thickness of the radiator....all
measurements in cm and Fin Volume in cubic cms.

Discussion: This measurement has NO quantitative data to support it and some obvious flaws (fin density and shape come to mind), but it is easy to obtain and I believe it provides a decent means
of comparing the cooling power of one radiator to another.

Question: How much Fin Volume (or rather how many radiators and of which size) am I going to need to do a custom loop of an overclocked i5-11600K and an overclocked RTX 3080 Waterforce?

Research results: maximum power draw of overclocked CPU ~ 250 Watts; maximum power draw of overclocked GPU ~ 350 Watts for a total draw of ~ 600 Watts.
A 120mm radiator has a Fin Volume of 389 cu-cm. (Three on-hand)
A 200mm x 200mm x 85mm radiator has a Fin Volume of 3400 cu-cm (Four on-hand)
A 200mm x 200mm x 45mm radiator has a Fin Volume of 1800 cu-cm (Two on-hand)
Other hardware: PSU - Corsair HX1000, on-hand, certainly sufficient for this build
Fans - Noctua NF-A20 PWM, 147 cu-M/hr
Physical Constraints and Preferences: I can squeeze a MAXIMUM of two of the 200mm radiators (either sort) inside the case, which would be my preference. However, I can add all the rest of my radiators on top of my case if required.

Guys, I KNOW this it can only be a "what your 'tummy' tells you" opinion, but how on earth would you suggest I proceed? And, yes, I know I can always add more if I need to, but revising hard lines is not something I relish doing!

Please speak up and tell me your thoughts...they will be appreciated even if not followed.

Very warm Regards,

Larry

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Solution
Since you have the parts, assemble them outside of the case and try different options.
Once you know what the best is, then remount them all in the case and customize your tubing.

I might add that an all core overclock on a 12th gen processor may not be the best way to get maximum performance for games. The turbo mechanism can boost a couple of cores higher than your overclock.
A few faster cores is what most games need.

#### Eximo

##### Titan
Strange sizes, but your single 200mm x 200mm x 85mm has potentially more surface area than two standard 280mm radiators. I use that to run a 3080Ti and i9-10900F. You are being a little pessimistic about CPU power consumption, you would have to really push things to get that warm. Even unlocked with a fixed voltage I can only reach about 150W with a 10 core.

50C GPU maximums and CPU in the low 70s as is typical for CPUs.

I would say using both 200mm radiators would be more then good enough and would avoid the complexity of adding all those 120mm radiators.

#### geofelt

##### Titan
Since you have the parts, assemble them outside of the case and try different options.
Once you know what the best is, then remount them all in the case and customize your tubing.

I might add that an all core overclock on a 12th gen processor may not be the best way to get maximum performance for games. The turbo mechanism can boost a couple of cores higher than your overclock.
A few faster cores is what most games need.

#### Imacflier

##### Distinguished
Strange sizes, but your single 200mm x 200mm x 85mm has potentially more surface area than two standard 280mm radiators. I use that to run a 3080Ti and i9-10900F. You are being a little pessimistic about CPU power consumption, you would have to really push things to get that warm. Even unlocked with a fixed voltage I can only reach about 150W with a 10 core.

50C GPU maximums and CPU in the low 70s as is typical for CPUs.

I would say using both 200mm radiators would be more then good enough and would avoid the complexity of adding all those 120mm radiators.

Eximo,

I just knew I could count on you for a response! Thank you so very much. Yeah, those power numbers are pretty high....the highest I found on search...but better too much cooling than too little. I believe I will take try using two of the 200 x 200 x 85 radiators and see what actually happens on synthetic benchmarks!

Warm Regards,

Larry
Strange sizes, but your single 200mm x 200mm x 85mm has potentially more surface area than two standard 280mm radiators. I use that to run a 3080Ti and i9-10900F. You are being a little pessimistic about CPU power consumption, you would have to really push things to get that warm. Even unlocked with a fixed voltage I can only reach about 150W with a 10 core.

50C GPU maximums and CPU in the low 70s as is typical for CPUs.

I would say using both 200mm radiators would be more then good enough and would avoid the complexity of adding all those 120mm radiators.

#### Imacflier

##### Distinguished
Since you have the parts, assemble them outside of the case and try different options.
Once you know what the best is, then remount them all in the case and customize your tubing.

I might add that an all core overclock on a 12th gen processor may not be the best way to get maximum performance for games. The turbo mechanism can boost a couple of cores higher than your overclock.
A few faster cores is what most games need.

geofelt,

AHA, another voice! YAY!

AND good advice: If I use flex tubing and an external mount, it is not quite so much an investment in time and possible leakage which makes it a rather good approach! Particularly since the combination of rads I would like to use due to ease of installation is one 200 x 45 plus one 200 x 85!

I will let y'all know how it goes!

Larry

#### Eximo

##### Titan
I'm sure those are the lower density FPI style, but it makes up for it with thickness and in this case, size. I have decent metrics in my head for 360mm and 280mm radiators and you can scale down easily with those. These are a shot in the dark, but if you do a volumetric calculation similar to what you have done, you can make some simple assumptions.

140x280x30 = ~1.2 million x2 = 2.4 million (standard 35mm radiator, also commonly find 45mm radiators) I would say right now my system averages 400-450W under a high end gaming load. GPU sits at its 350W limit if I play demanding games at 1440p, CPU bounces around 60-100W draw.

200x200x80 = 3.2 million + 1.6 million for another 40mm. Probably have something like 600W capacity in the thicker one, and another 300W in the thinner one. Diminishing returns after a while, but you should be able to get away with some very lazy fan speeds.

#### Imacflier

##### Distinguished
I'm sure those are the lower density FPI style, but it makes up for it with thickness and in this case, size. I have decent metrics in my head for 360mm and 280mm radiators and you can scale down easily with those. These are a shot in the dark, but if you do a volumetric calculation similar to what you have done, you can make some simple assumptions.

140x280x30 = ~1.2 million x2 = 2.4 million (standard 35mm radiator, also commonly find 45mm radiators) I would say right now my system averages 400-450W under a high end gaming load. GPU sits at its 350W limit if I play demanding games at 1440p, CPU bounces around 60-100W draw.

200x200x80 = 3.2 million + 1.6 million for another 40mm. Probably have something like 600W capacity in the thicker one, and another 300W in the thinner one. Diminishing returns after a while, but you should be able to get away with some very lazy fan speeds.

Excimo,

Since I have one of the 45's mounted to a fan sitting on my desk, I went ahead and counted the fins. For what it is worth they are 12 fins/inch...the same as the 85mm, I can't seem to lay hands on one of my 120mm rads for comparison so I don't know if 12 fpi is low density or not.

On another topic: since all my fittings are compression types and I do not want to buy a whole other set for flex tubing, do you see an issue of installing a 5/8" copper stub into a compression fitting, sliding the stub into flex tubing and clamping it for short term testing?

Larry