The NexXxos XP is shown in the image below borrowed from a review at Nokytech.


Photo Nokytech

The NexXxos XP is based on the tried and true, extruded pin design. That is, the impingement zone (area directly above the CPU-core where water impacts) is comprised of many small pins which are left standing after CNC machining away 1-mm of material from a 2-mm thick copper base plate. Contrary to what people often visualize, in thermodynamics heat transfer entails heat (kinetic energy) traveling from an area of high temperature, to an area of lower temperature. It's basically a rapid collision of molecules which diffuses outwards until the reaction reaches equilibrium (cools). Therefore heat (heat = kinetic energy (rapidly agitated or moving molecules)) propagates from the CPU up through the pins, where it's absorbed, and removed by the water entering the block. To ensure the water entering the block is distributed evenly onto the pins in an area approximating the CPU's core, the XP utilizes a secondary flow plate. This plate rests over the first, and has multiple holes drilled through it directly over the pins. Additional material (copper) is machined around the impingement area which channels the water up through the outlet. Conduction naturally draws the heat generated by the CPU up through the base plate, into the pins and then into the water flowing over them. As water exits the block, its original kinetic energy (heat) exits with it. Another critical aspect in water block design, and a contributing factor to the NexXxos XP's cooling prowess, is base plate thickness. In the NexXxos XP, thickness from the bottom of the base plate, to the top of the pins (which comprise the impingement zone) is 2-mm. Where the base plate has been machined creating micro-channels between pins, and to the depth of the channels surrounding the pins, is just 1-mm thick. The photo below (also from Nokytech) exemplifies the block's internal plates.


Photo from Nokytech

The NexXxos XP was designed for optimal performance in a "low-flow" environment; therefore the Alphacool AP1500 pump (included with Xtreme Pro Set ) will be used. This pump is made by Oase exclusively for Alphacool, it circulates approximately 900l/h at 12V and uses 1/4" tubing.

The pump is remarkably quiet and I found myself checking it repeatedly because I thought it was off. Alphacool also includes a power converter, which allows the end-user to switch between 12V/900l/h and 24V/1500l/h, regardless of your PSU's capabilities; you can operate at either voltage.

I chose to use the pump at its lower/slower setting of 12V pushing 900l/h. On this subject, I believe the terminology "low-flow" (especially in the USA) brings with it negative connotations. I fear the concept has been unfairly branded with a Scarlet Letter; implying lower-flow designs are somehow inferior. This subject has been a point of contention with some USA site's adamantly defending the higher pressure = greater performance, view point. Coolers such as the Cascade, which forces water through mini jets partially submerged into isolated 'cups" might be considered the epitome of a design based on high water-pressure. While I do believe the Cascade is an excellent performer, and an astute piece of engineering, I haven't had the opportunity to test it. My mention of the block in past articles (although complimentary) seems to have created a rift between myself and defenders of such designs. Nonetheless I'm quite familiar with Danger Den's TDX water block which I believe to be very close to the Cascade in its design execution.

My outlook on the situation is that while high-pressure water blocks are effective, they require hardware (pumps/tubing) which can be physically obtrusive. Where many USA systems rely on 1/2" ID tubing, forcing that tubing over male barbs stretches the material. Given the combination of high water pressure and time, such connections may have a greater propensity for leakage. Alphacool employs ¼' tubing which inserts and locks into female connectors. Perhaps the most important aspect of low-flow systems on the whole is that the entire system, tubing, pumps, easily fits into our often overcrowded PC-cases and the entire philosophy is in harmony with the our need for a micronized PC World. Compact pumps such as the Alphacool AP1500 also require less current, placing a minimal load on the power supply.

Water cooling allows one to pinpoint water flow onto a very small area, effectively removing much more heat then air-cooling ever could. At the risk of being redundant, as die sizes continue to shrink (albeit in sync with Moore’s Law, or not) ironically the transistor count increases, and so too does the amount of current required to operate these "switches." As the amount of "real-estate" these transistors occupy shrinks, the collective heat generated increases. Air cooling requires surface area to dissipate that heat, and thus equates to mass. The combination of thin fins and heat-pipes, no matter how effective, still relies on a large copper mass. This is the reason why we see large and heavy heatsinks score high in [M]’s latest P4 HSF roundup. We’re rapidly approaching the point where these HSF (Heat Sink Fan) combinations are simply too large and heavy to mount on our motherboards. Given the benefits of H20, I believe it's only a matter of time until most CPU's are water-cooled.