Bill Adams waterblock test
Be Cooling Describes Their Design Goals for the SlitEdge:
The SlitEdge waterblock was developed with several objectives in mind – Performance, Price, and Appeal. We wanted a very good performing block for large and small die CPU’s as well as thermoelectrics, at a good price. The block has 4 tapped corner holes which can be used to retain a peltier and coldplate.
It is well known that thermal transfer is done best when the internal surface area AND turbulence is high. Surface area is accomplished through 11 small slits, each 1/16″ wide and to a depth of 1/4″. Even though the channels are straight across, the coolant flows through it like a wave – up and down. This churns the coolant, mixing it and creating the required turbulence.
Flow characteristics of the block were optimized as well. Only a small amount of restriction was entered into the design. This provides enough to increase the velocity of the coolant yet not overwork a typical aquarium type powerhead pump. Thus, an inlet port over the die is not needed. This also eliminates dead zones or air pockets.
The waterblock lid is anodized aluminum with AMD and P4 mounting holes built in. It will be upgradeable to future processors with a simple lid swap.
The SlitEdge is typical of the more recent waterblock designs utilizing a less massive (therefore lighter) copper baseplate and mounting by means of holes in the waterbox cover. The SlitEdge is well made and attractive, and due to its layout very easy to consistently mount.
The copper baseplate is 2.4 x 2″ square and nominally 0.375″ thick, including the integral internal fin height. The top cover is black anodized aluminum. The SlitEdge incorporates chrome-plated 1/4″NPT barb connectors for 1/2″ ID tubing in the top, centrally located between the mounting holes. The dry weight is 308 grams +/- 5 grams and filled with coolant weighs 327 grams +/- 5 grams.
The baseplate of the appeared flat with faint circular tool marks. It has a high luster which enables using optical flats as described below.
The SlitEdge was flow tested and from the results below it can be seen that its flow resistance is quite low.
The SlitEdge was then mounted under carefully controlled conditions 10 times and its “C/W” determined under ‘standard conditions’ (defined as 70W applied heat load, 3.8 lpm coolant flow rate at 25.0°C, and 10 kgf applied compressive load across the TIM joint). The following results were obtained:
- “C/W” mean = 0.226
- “C/W” range = 0.006
- “C/W” standard deviation = 2.15E-03
The data is consistent with a normal distribution: P = 0.99 where the normal distribution has a mean = 0.2262 and standard deviation = 2.25136E-03. The “C/W” distribution is shown below. ‘Standard Error’ bars are indicated to enable an estimate of the measurement uncertainty.
The “C/W” was then determined with an applied heat load of 70 W (about 100 W per Radiate) under a range of flow rates from 1lpm to almost 12lpm.
Combining the head loss and “C/W” data yields the graph below which enables one to estimate the “C/W” based on the pressure drop (or head loss) across the wb. (The wb pressure drop will be only a portion of the total coolant system’s flow resistance, the flow rate being a consequence of the pump’s capability at the total system head.)
This waterblock’s “C/W” curve has a rather well defined ‘knee’, beyond which there is only a slight increase in cooling at even substantially higher flow rates.
Upon completion of the performance testing the bp surface was again inspected. There was no indication of unevenness in the pattern of the residual thermal grease upon disassembly (uniform widely dispersed very small ‘specks’, characteristic of the grease used).
It was then inspected with an optical flat in a reflex viewer using monochromatic light from a filtered mercury bulb. On a suitably reflective surface ‘fringes’ will be apparent and each one represents a height (difference) of ~0.000273 mm (0.000010749″). These are VERY small numbers and while ‘absolute’ flatness is a desirable ideal, the purpose here was to look for grosser indications of unevenness.
The image below has been manipulated to make the contrast between the fringes more visible. The die contact area (10x10mm) can be faintly made out by the slightly dark square outline in the center of the image. Of significance is the vertically oriented depression to the right. This is not so deep as it may appear, say 8 fringes @ 0.000273 mm is still only ~0.0022mm, but no doubt did adversely affect the results slightly. It is suspected the baseplate was slightly bumped after finishing.
Discussion of Results:
The low flow resistance of the SlitEdge ensures that it will function well with about any pump provided the other system components are not unduly restrictive.
This is an excellently performing waterblock that is easy to install, but that could accumulate an air pocket when the connectors are horizontally mounted (with the baseplate set vertically).
As is always the case with aluminum components, their corrosion resistance will depend on the quality of the anodizing, and such can only be determined with longer term testing. In any case, the use of an effective corrosion inhibitor is always recommended in WCing systems containing aluminum.