Closer Examination

I have had hands on experience with Alphacool's original 360, 480, and 560 mm NexXxos ST30 radiators and of course the recently reviewed ST25, but having a thin and large copper radiator in front of me in person is something else. You go from thinking it's going to be heavy to realizing that the steel casing and thin copper tubes and fins don't really add much to the mass. Even with the radiator filled with coolant, it is still easily installed into a case. All these reasons are why slim radiators are always going to be a thing even with small form factor builds going out of fashion courtesy all the power-hungry hardware as of late. The NexXxos HPE-30 360 mm measures 392 x 124 x 30 mm, giving you an additional 15 mm of room over the NexXxos HPE-45, which could be taken up by a slim 15 mm fan. The design language is otherwise identical to the thicker radiator with rounded corners and an end tank split in the middle. We still have a steel case given a black paint job, although I imagine Alphacool is working on bringing white radiators to the market too. Unfortunately, the blue branding continues to catch the eye on two sides, making it hard to classify this as a particularly clean-looking radiator.


On a highly positive note, I was very pleased to see Alphacool retain the five BSP G1/4" threaded ports. This makes the NexXxos HPE-30 a unicorn among slim radiators, although the one of the shorter sides had been bent in slightly. Not a great look, but it didn't change functionality. Two ports have blue-colored dust covers. These are what you would use at a minimum to connect the radiator to the watercooling loop. Then we see two others on the opposite side for more leeway with plumbing, and a fill/drain port is on the other side. These additional three ports have stop plugs that are flush with the case, which is more useful than you would think.


The fan holes in the steel frame are well-threaded, which gets the aforementioned black paint to better match most PC DIY builds than the native steel color. These holes are the standard 15 mm apart, which works with just about any case today. I am also happy to see screw shields as they provide a safety barrier with longer-than-appropriate screws that might otherwise pierce coolant tubes instead of just fins.


Those flush-fit stop plugs aren't new, yet something I have not seen other brands adopt. These are extremely low-profile stop plugs, and installing or removing them takes the tool Alphacool includes. The bottom of each plug has a silicone base which does the same job as a typical O-ring seal on a higher profile fitting or stop plug. The four BSP G1/4" ports on the end tanks are part of the frame in that there are brass inserts for the actual threads since copper is too soft. These are also threaded perfectly, and the other two ports come with blue plastic covers that are really only meant to keep dust out before use. You would replace these with standard BSP G1/4" threaded fittings when using the radiator as part of your loop. A look through one of these ports just shows you the stop plug on the other side, with the tanks starting slightly inward and making the coolant take a gentle turn into the core. Speaking of which, the radiator core adopts the more typical U-flow design for the coolant, with either port on the left or right as the inlet and the other side as the outlet, which depends on your plumbing layout. There is a single row of fins and tube stacks with 14 tubes that are ~1.5 mm thick. The 14-way parallel split of the coolant will result in lower coolant flow restriction than other single-row radiators with fewer tubes—12 is typical—or thinner tubes, such as the Black Ice Nemesis GTS/LS, but will generally fare worse against dual or triple-row radiators. The entire core is copper, which itself signifies the absence of an alloy in favor of a higher-purity copper core.


As for the fin stack, we get the usual ~7 mm high and lightly louvered serpentine fins, which should increase the contact surface area for air flowing through the core. While possibly a boon at higher airflow, it may adversely affect thermal dissipation at lower RPM or laminar flow regimes. The fins are rated at 18 FPI in density and measured in at 18–19 FPI on my sample. The core itself is ~20 mm thick with a ~5 mm plenum on either side between it and the frame, which is not the easiest to measure given the fins extend past the tubes. Without exactly knowing how thick the fins are, this combination leads me to believe that this radiator will be a low or medium-airflow optimized cooling solution. That having been said, we will see how the radiator fares in our testing over the next couple of pages.