Radiator Push vs. Pull vs. Shroud Testing V2

Posted: January 15, 2012 in Radiators, Uncategorized
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While I have done radiator shroud testing before using more conventional 7 bladed fans, I wanted to do an update to both serve in shroud results and also give me some hands on time with my new radiator testing bench to see if there are any tweaks remaining before settling on a test method.  I had noticed in my previous shroud testing that push vs pull optimization was different depending on the fan used, but I didn’t really have enough data to conclude it was fan speed alone or if it was simply the type of fan.

After testing many more fans, the Gentle Typhoons were again one of the stronger in CFM/dbA ratio on a radiator, so I figure it only makes sense to follow up with that fan to see what if any change is apparent there.  In addition I used TFC 30mm shrouds in the old test and I wanted to compare that shroud to using an old gutted 25mm fan which is cheaper and many people do use.

So with that, I’m updating to a new radiator test bench with more controlled air flow measurements and the ability to also measure air flow volume.

Before getting started, I’d like to thank the sponsors that provided parts I used in this test:

Swiftech sponsored the MCR120QP radiator

Koolance sponsored the PMP-450 pump

Danger Den sponsored the MC-TDX waterblock

TFC sponsored the TFC 30mm shroud


Using my new radiator test bench V2, I’ll be running the system with the pump at setting 3 which is producing approximately 1.7GPM or so. Heat is provide via a modified aquarium heater and tuned to 125W for approximately a 10C delta system with the fan running at full speed.  Seventeen thermal probes are measuring water in, water out, air in, and air out.  In addition a hot wire anemometer is measuring air velocity, a “Kill-a-Watt” is measuring heater wattage, and another multimeter is measuring voltage at the fan plug.

Here is the setup with the access window temporarily opened.  During testing the top acrylic panel will be closed so all air out goes through the air out port for air measurement.

I’m looking to log temps for about an hour after stability is reached to average out the ambient fluctuations.

As with any good testing, I think it’s important to show not only the testing rig, but also the data collected to develop the conclusion.  While many go straight to the results, I’m sticking to my usual “testing story” approach and going to share the details of how I came to any conclusions.

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  1. Badelhas says:

    Hello Martin, great work, great site, congrats!
    Did you get to test push-pull on a 120mm thick 38mm rad? Linus and Tim Logan assure us it does help to reduce temps.

    • Martinm210 says:

      No, it could but considering I got gains on the RS120 slim/low density and none at all on the mcr120qp slim/low density, I don’t think you can assume any generalities. Likely depends on the exact radiator brand/type and perhaps the fan type too as it could adjust restriction enough to shift the curve to a hump in the fan curve etc. Very specific results is what I found so I would shy away from assuming more.

  2. Gadgety says:

    Very thoroughly done, Martin. I’m really glad you’re back to testing! I’m new to watercooling and I remember reading your previous conclusions about fan shrouds as I searched the net- I was set on getting shrouds. I appreciate this update.

  3. Dan says:

    Doesn’t it make sense that you see better results using a shroud on the XSPC than on the MCR since the FPI is very low on the XSPC at “sub 8 fpi” vs 20 fpi for the MCR?

    I would think that with the denser fin configuration; the further away you move the fan the harder it will be to penetrate the dense fin structure. Which would minimize befits obtained from decreasing the deadspot of the fans center.

    But on the less dense radiator you can realize the benefits more-so from decreasing the deadpsot since the loss of penetration into the fin structure is lessened.

    I would like to see how a 10mm shroud performs ? I guess is that you would have better performance.

  4. Sebastien says:

    hi martin thanks for another gret review with real numbers and real thoughts behind this.
    I have a question about push pull: you allways do the push pull tests with the sames fans and speed conditions, for both push and pull fan.
    I have a loop with 3 noctua nf p12 pushing fans and i have scythe karma low noise fans but low rpm too (500 rpm) that i don’t use becasue they are not enough powerfull by themselves.
    i was wondering if i add the scythe fans in pull with my noctua in push, do you think i should ahve some gain nor not at all or so ridiculous that it’s not worth installing it ???

    and my radiator is a swiftech mcr320 QP as you showed that radiator is important also.

  5. Ash says:

    I would assume there is more of a sound benefit than a cooling benefit when it comes to a shroud.
    as you dont have blades rushing within a few mm of radiator fins.

  6. Hydrow says:

    I have an idea but I don’t have the know age or equipment to test.

    I was wondering what the delta would be in a push pull setup on a 240mm radiator using 4x 120 SP vs 2x 120 SP push fans and 2x 140 mm A pull fans.

    Thank you

    • Martinm210 says:

      Not sure and no longer have the time to test either. Generally push plus pull or two pumps in series provides about a 30% flow gain. If you had an average 10c water to air delta, that would equal about 3C. Of coarse the delta is the bigger unknown. I have built high performance water systems than run no more than 2-3 degree deltas. I have also seen AIO kits push 20C. The gain is flow so degree gain is proportional to the unknown delta.

  7. Guy Cotnoir says:

    So no shroud will require less electricity to reach the same rpm as with shroud……interesting!
    I’d love to see if this results in higher or lower air flow with/without shround given the same rpm.