Articles: Cooling

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Design and Functionality

The Kraken X40 represents the classic design of closed-loop liquid cooling systems. It consists of a waterblock combined with a pump, a radiator with fan, and connecting pipes.

We’ve studied and tested such designs a lot of times, but the Kraken X40 is special in one respect:

Of course, we mean its large radiator which measures 138.4 x 172.5 x 27.0 mm.

According to NZXT, the radiator’s surface area is enlarged by 36% in comparison with ordinary ready-made solutions with 120mm radiators. The coolant now moves along 13 flat pipes instead of 9-11 as usual.

A stretch of corrugated aluminum ribbon is soldered (or even just glued) between the pipes. The radiator's body is only 16 mm thick, so there are no advantages compared to other products based on the Asetek platform in this respect.

The radiator sticker tells you the product's model name and power specs (12 volts, 7.5 watts). The power parameters must be those of the pump.

There are two fittings on the other side of the radiator. Pipes with an exterior diameter of 10 millimeters are press-fitted on them.

The length of the pipes has been increased from 300 to 400 mm, letting you place your NZXT Kraken X40 anywhere in your computer case.

The new waterblock/pump combo hasn’t changed visually. It still measures Ø72x32 mm. The performance of the pump is not specified.


However, we can learn that the pump’s motor works at a speed of 2900 (±150) RPM, which our monitoring tools confirmed. There is a thin layer of high-efficiency thermal interface pre-applied on the waterblock’s base.

Removing the plastic cap, we can see an electric motor and a small PCB.


NZXT says that the copper waterblock has a microchannel structure like all Asetek-based models although NZXT doesn’t confirm (or reject) the affinity of the Kraken X40 with Asetek. The waterblock's contact spot is finished well:

We’ve got the following thermal grease imprint on the convex heat-spreader of our CPU:

It’s clear that the pressure is the highest at the center of the waterblock and CPU heat-spreader.

The pump features nice-looking highlighting of the manufacturer’s logo.

Its color and brightness can be regulated using special software we’ll discuss shortly.

The Kraken X40 is equipped with one 140mm NZXT FX-140 fan.


The 9-blade impeller with a diameter of 134 mm should cool the thin radiator well enough even at low speeds. It is PWM-regulated in a range of 800 to 2000 RPM. The fan is specified to produce an air flow of 54 to 98.3 CFM at 21-37 dBA of noise and a static pressure of 0.8 to 2.2 mm of water.

The fan’s 42mm motor runs on a fluid dynamic bearing. The sticker doesn’t provide much information:

The bearing is specified to last for 35,000 hours or 4 years of continuous operation. The peak power consumption of the fan is said to be 7.08 watts although it was not higher than 5.3 watts according to our own measurements.

The fan is connected to a 4-pin cable that goes from the pump.

You can connect a second fan but it won’t be PWM-regulated. The pump’s cable is 240 mm long while the fan’s cable is 385 mm long. The pump is also connected to a mainboard’s 3-pin fan connector and USB header (with a 600mm cable). The latter is needed for the software aspect of the Kraken X40 which we will discuss shortly.

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