XSPC RS240 Radiator Pressure Drop Flow Testing


Welcome to my pressure drop testing of the XSPC RS240 radiator.  I would like to give special thanks to Paul from XSPC for yet another great product to review, the products I have tested have all surprised me in the amount of attention XSPC gives towards top performance at great prices.  They really put 100% into making products that perform well!  

With this review I will focus on the pressure drop and flow characteristics for this radiator.

Radiator Characteristics

The radiator is a typical brass chamber and tube construction with copper fin similar in fin density and size of the Swiftech MCR quiet series or the HWlabs BIP series. I found that it had the following characteristics:

  • Copper Fins (13 folds per inch)
  • Brass Chambers
  • G1/4 barb ports to accept a wide variety of G1/4 fittings
  • Blue UV paint finish
  • 4.75" (120mm) width
  • 10-5/8" (270mm) height
  • 1.35" (35.5mm) thickness
  • 1lb 3.9 ounces (without barbs) weight
  • ROHS compliant

Hydraulics and Pressure Drop Testing

The most scientific way to determine a blocks hydraulic resistance is to test pressure drop. Pressure drop is a measurement of pressure loss across a radiator that varies with flow rate.  This is basically a measurement of energy loss, and directly influences how much flow rate you will have.

  • Dwyer Digital Manometer 477 Mark V - Accuracy .5% of Full Scale.  Range 0-20.00 PSI range, Resolution .01 PSI
  • King Instruments 7520 Series 0-5GPM, 250mm scale - Accuracy 2% of Full Scale.  Range 0-5GPM, Resolution .1 GPM (can be interpolated to .02GPM)
  • Water Source - Household water pressure - 50PSI at >5GPM - Because flow rate readings are instantaneous, household tap water and water pressure are a good and powerful source for pressure drop testing.

And my results are as follows, the pressure drop results are very very good!

And if you're not familiar with what this means, I'm providing a relative chart below comparing a few other published and tested curves to the acquired results.  Keep in mind these comparison curves were based on other testing facilities, so there could be some error in different test beds but pressure drop is generally a fairly repeatable test if good equipment is used.  The XSPC RS240 is right near the bottom of the group, it is the best flowing of the single row tube style radiators, very nice.  Upon careful inspection of the interior from what I can see, these radiators flare the tube ends more than others and this reduces entrances losses which helps lower pressure drop, very nice!

This will allow you to maximize your system flow rates for excellent thermal efficiency in your water blocks.  This is yet another great product from XSPC with bottom line performance.

Cost Comparison

So another important consideration with most people is cost.  For a fair cost comparison, I chose the good folks at watercoolingshop.com since they carry both the XSPC and Thermochill PA series radiators.  

At watercoolingshop.com the prices were including VAT as of 4-10-2008

XSPC RS240 = UV Blue £25.99 (Black = £23.99)
Thermochill A120.2 = £49.99
HWlabs BI GTS240 = £30.98

So in terms of cost using the black RS240, you can save 23% over a GTS 240 radiator and 52% less than a Thermochill PA120.2, that's a great price!

Thermal Testing 

This is my first 240mm radiator I've tested thermally.  I did my normal radiator testing (See Thermal Testing Specification on this page) on this radiator using my crystalfontz to log four air inlet, three air outlet, a water inlet, and a water outlet over 5 1-hour tests until water delta equilibrium was reached.  Each test was run using a different fan and RPM setting to give you a nice broad range of performance figures.  Flow rate was fixed at 1.5 GPM and heat load was provided by a modified aquarium water heater plus an assumed 5 watts for the Danger Den CPX-1 pump (5.88 consumed)  for a total of 300 watts which was kept within a couple of watts using a variac.  Each fan was tested the same using a pull configuration without shroud.

The following results were obtained:

First are my tabular results which includes additional data like the air in and air out, etc.  This is fairly typical of a slim 21mm thickness lower density radiator optimized for low speed fans.

And this is the estimating chart where you can select a heat load in watts and get an estimated water temperature.  For example assuming I was running a 200 watt quad core setup using Ultra Kaze fans at 2930RPM, I would get about a 4.4C delta.  So if my ambient temperature was 20C, my water temperature would be around 24.4C.

To estimate a heat load you can use the following tools:
Also worthy of noting, like any radiator, there is a significant performance increase between the ultra slow and ultra high fans, in this case you nearly triple the performance using the high speed fans.

These are the c/w values plotted over the fan range, more than anything this just shows you the overall testing is following a fairly controlled trendline which is good, and c/w gains diminish as the RPM increases.

And everyone wants to know what heat dissipated is.  This is what I call the 10C "Average Performance" delta where, where it's still good, but not an extreme setup where 5C deltas are desired.  With this you can see that you could cool a wide range of different components depending on the fan performance and there is about a 2.6X performance gain using the 3000RPM 38mm high pressure fans vs. the undervolted 1000RPM 25mm fans.

And this is the high performance 5C delta chart where water temperatures are very cool and would provide extreme cooling performance.  You can cool a very hot overclocked quad core or something in the 200W range with fans running about 2400RPM or higher, or an overclocked dual core around 115W with slow speed 1350 RPM fans.  Or you could run a dual core and GPU, etc it all depends on the actual heat load and fan used, but there are options available with this size.

There you have it, a very low pressure drop, low cost, and well performing compact radiator that can suit many needs.  Due to the low pressure drop of this radiator, I would certainly consider running two or three in the same loop if it's needed to gain the cooling capacity needs you are after.  Use the above guides to estimate your heat loads and water temperature.  If running two of the same radiator, simply take your actual heat load and cut it in half over the two radiators.  My recommendation is to strive for a 5C delta if possible, but up to a 10C delta is generally considered acceptable.

Shroud or push/pull gains

I used the RS120 to do a whole bunch of fan orientation and shroud performance gains here. I saw some significant performance gains particularly using the 38mm fans in different orientations.  Installing two 38mm fans in push pull on this radiator provided nearly a 25% gain over one fan in pull, or just one 38mm fan in push with a 30mm shroud provided a 19% gain.  All of this testing and results on this page was done with a single fan in pull condition so if you double up on fans in push/pull or use a shroud, you'll see better performance than the above results. 


  • Very low pressure drop - Great for adding into existing loops for multiple radiator setups.
  • Compact and easy to fit in many locations, works well as a supplimental raditor for existing setups.
  • Excellent price point
  • Performs well, depending on the fan used can fullfill a wide variety of cooling needs.
  • Responds well to the addition of shrouds or two fans in push/pull.
  • Optimized for low speed fans
  • M4 tapped screw holes
  • G1/4 barbs


  • Depending on the heat load and fans selected, it may be desireable to run multiple radiators in the same loop to achieve the desired cooling performance goals. 

Where to buy

XSPC Retailers Link