The PolarFLO from Horse of Iron

Bill Adams waterblock test


Horse of Iron Describes Their Design Goals for the PolarFLO:

Horse of Iron, Inc. recently broached the PC water-cooling market with the PolarFLO Universal water block. We wanted to begin our PC water cooling product line with a ‘flagship’ water block. The PolarFLO Universal water block presented in this review is the third revision refined over three prototypes.

We opted for a look of our own, especially since we wanted our customers to know us by our craftsmanship. Each of our water blocks is hand lapped and hand finished after assembly. The best manufacturing methods can be employed by anyone but there is no substitute for hand working. Each one of these water blocks receives our signature touch.

We also wanted to offer excellent performance with a reasonable price. The results of these efforts is within this review. We will constantly be optimizing our designs, exploring the synergy that exists between so many variables.

While the tested waterblock was uncoated, the aluminum top will be black anodized with a heavy nickel-acetate seal.

Lovas of Horse of Iron

Bill Adams – First Impressions:

An attractive waterblock, the PolarFlo is obviously the product of modern CNC machining and is quite finished in all regards. The waterbox is aluminum, the baseplate is C110 copper, and the two are attached with Allen head screws.

Three hose connections are utilized, with plastic 1/2″ barb connectors being threaded into the waterbox top; the discharge connectors being joined with an included 1/2″ barb fitting having a 60° included angle.

The copper baseplate is nominally 2.5″ in diameter with a square raised 1.75″ CPU contact area and nominally 0.35″ thick, not including the integral internal fin height. The baseplate is fastened with torqued fasteners and then lapped. This means that the baseplate should not be removed, clean with a suitable strong detergent if required. Torqued fasteners also imply thread deformation, their removal may result in stripped threads.

The baseplate of the PolarFLO appeared quite flat with a high luster, enabling the use of optical flats as described below.

Test Results – page 2…

Bill Adams

Test Results:

The PolarFLO was flow tested and from the results below it can be seen that its flow resistance is moderate.


The PolarFLO was then mounted under carefully controlled conditions 10 times and it’s “C/W” determined under ‘standard conditions’ (defined as 70W applied heat load, 3.8lpm coolant flow rate at 25.0°C, and 10kgf applied compressive load across the TIM joint). The following results were obtained:

  • “C/W” mean = 0.254
  • “C/W” range = 0.003
  • “C/W” standard deviation = 2.26E-03

The data is consistent with a normal distribution: P= 0.57 where the normal distribution has a mean = 0.2539 and standard deviation = 2.27031E-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 70W (about 100W per Radiate) under a range of flow rates from 1lpm to 11lpm.


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 somewhat defined ‘knee’, below (to the left of) which it is not very efficient. While increased flow would improve the cooling, not many pumps will have such capability.



Bill Adams

Upon completion of the performance testing the baseplate 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 ~0.000273mm (0.000010749in.). 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. As can be seen, the CPU contact area is slightly convex and VERY flat. Hand lapping this waterblock’s baseplate will certainly make it less flat.


Discussion of Results:

The PolarFLO is a moderate performing waterblock that is easy to install (given the three hose connections), but whose performance will be dependant on having a pump with good head capability.

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.

Thanks to Steve Lovas and Horse of Iron for sending us this attractive waterblock.

Details on the testing of commercial wbs may be found HERE.

Bill Adams

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