We are in the midst of an explosion in AIO liquid cooling and its radiators, where manufacturers are betting very strongly on this type of cooling solutions and this is causing a massive arrival of models. Logically, there is a fundamental aspect that influences the performance of each unit launched and this is its radiator. We have seen bets of all kinds but is a larger radiator really a better buy for these AIOs in terms of performance?
With this feature of AIOs, we have to stray from the bespoke liquid cooling concept. And we must do it for numerous purely logical reasons: thermal performance. This on the other hand encompasses a number of elements that detract from the performance of each unit, so let’s address them to answer the initial question.
Why isn’t AIO liquid cooling performance scalable to larger radiators?
A larger radiator in terms of length or width is always going to be better than a smaller one for parameters like custom liquid cooling. We have a number of restrictions in AIO liquid cooling that have surprised us on several occasions while testing devices against their competition.
Bigger is thus not equivalent with better; it cannot be accepted as dogma in an AIO for a variety of reasons. First and foremost, we have the system pump, which is a critical component. As a general rule, and with the exception of “slightly custom” models, we’re talking about pumps rated between 6 and 8 watts, with flow rates that seldom surpass three figures in terms of litres per hour, and are often considerably closer to the digit than to the three.
What will happen with this? A radiator’s performance is almost proportional to the amount of water that passes through it. You can improve performance by changing the fan, but you can’t replace the pump. As a result, a greater surface area in terms of width or length reduces performance, because common pumps aren’t increasing at the same rate as the rest of the system.
A bigger surface area radiator requires a higher pump performance to sustain the flow, which when combined with a greater usage of fins on the cold plate creates an enormous problem in these systems.
Better fans only alleviate the problem
This performance limitation of today’s pumps to larger and larger radiators can and should be remedied with better fans. As you may have seen, the same fan is not always duplicated in AIO, even if the models are from the same series. LED fans are employed in some circumstances and not in others, with vastly varying RPM, mmH2O, and CFM ranges, as well as loudness.
This results from the preceding, since if your pump is unable to move enough liquid, your radiator is too restrictive, or the block is too restrictive, performance must be obtained somewhere, and in this instance, the simplest solution is to add a higher performance fan.
Taking this into consideration, is purchasing an AIO liquid cooling system with larger radiators accurate, ideal, and recommended? Not necessarily; as we’ve seen, in these systems, other considerations must be considered, and sometimes more isn’t better.