Articles: Cooling
 

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Design and Functionality

We are very well familiar with Zalman cooling systems featuring a radial heatsink, we have been reviewing them since 2005, when the impressively efficient Zalman CNPS9500 LED came out. And today, seven years later, the new Zalman CNPS9900DF still has some of the familiar traits:

 

  

Although now the heatsink is built of two arrays, there are two fans and a different heatpipe layout. The cooler has also become larger and measured 154x140x100 mm. It weighs 850 grams.

The new Zalman CNPS9900DF is very similar to Zalman CNPS9900 MAX, but has an extra fan and a larger first heatsink array:

 

As a result, the total effective surface area of the Zalman CNPS9900DF compared with Zalman CNPS9900 MAX increased from 5,402 cm2 to 6,800 cm2. Although this number is still fairly low compared with what other contemporary super-coolers have to offer.

The heatsink fins soldered to the heatpipes at 1.0-2.5 mm distance from one another are made of solid copper and are nickel-plated, just like the heatpipes. A 135 mm fan sits in a recess in the first heatsink array. A second 120 mm fan is installed between the two heatsink arrays:

 

There are only three heatpipes and they come out of the cooler base in different directions. For some reason there is only one heatpipe piercing the larger heatsink array, while the smaller arrays has two heatpipes in it:

We don’t know what the reasoning behind this solution was, because it is more logical to have more heatpipes inside a larger heatsink array, because it should be dissipating more heat. Zalman engineers must be very confident in the efficiency of their composite heatpipes that is why they decided to implement this particular heatpipe layout and use so few heatpipes altogether:

I would like to remind you that composite heatpipes, that are Zalman’s unique invention, can be 50% more efficient than regular heatpipes. Unfortunately, we haven’t yet been able to confirm this statement.

The heatpipes lie in special grooves in the cooler base and are soldered to the base:

The finish quality of the cooler base contact surface is pure perfection:

It is also impeccably smooth - the thermal paste imprints were complete and even for both cooler positions:

 

 

As for the fans, they deserve a separate mention. The fans have nine-blade impellers 120 and 135 mm in diameter respectively:

The rotation speed of the smaller central fan cannot be adjusted and is set at 1000 RPM. The larger fan can be controlled using PWM (Pulse-Width Modulation) method in 900-1400 RPM interval. Frankly speaking, we do not quite understand why they would mismatch the rotation speeds and fan diameters like that. The cooler noise is declared at 19-27 dBA and there is no mention of the MTBF for the enhanced slide bearings in the fan motors.

I would also like to point out that both fans have blue LEDs, which makes the cooler look gorgeous in the dark of the night:

 

 
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