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Russian Cold War Technology For Your Computer
Meet the Delta 120x76mm GFB1212VHW.
http://www.xtremesystems.org/forums/...1&d=1157160187http://www.xtremesystems.org/forums/...1&d=1157160437
This double bladed, dual motor beast, pumps out a maximum CFM of 220.29 and an air pressure of 15.04mm H20, at only 59 dBA! The fans spin at 3550/3200 RPM, and each motor uses 12v of power at only 1.325A/15.9W, or 2.65A/31.80W between the two of them if hooked to the same control, which is actually how they should be controlled since they should both always be spinning at the same exact speed. By spinning in different directions, these dual propellers actually reduce resistance, allowing the air flow to be much more efficient.
The first appearance of this technology was during the Cold War in 1956, when Russia accepted into service the Tu-95 Bear Strategic Bomber.
http://www.xtremesystems.org/forums/...1&d=1157160475
The Bear was the first aircraft in world history with dual propeller turbofan drives, giving it superior speed, range, use of horse power, etc. It was able to fly to a range of 12,500 km, and travel at a speed of 925km/h. “The new drives NK-12M were created in Kuznetsov OKB. TVD two coaxial screws in the opposite parties were supplied by differential reduction gearboxes, gyratings. The propellant consumption of new drives made only 0.207 kgs (h.p. h).” Of course the US Government was pretty much freaking out at this point, since Russia had such a superior piece of military hardware in that day and age.
The GFB fan uses this same technology, that appeared over 50 years ago, and it still works pretty damn well. Having dual propellers reduces stress on the blades, meaning that the propellers don’t need as much RPM behind them, so they can spin slower, and by working together, achieve the same CFM of single prop fans at a slower speed, thereby producing less noise since the resistance is so much less and the fans aren’t whining from that high RPM, which I’ll explain later can actually be a drawback.
If you compare to other Delta fans, like the TFB1221GHE, which pumps out a very close maximum of 220.01 CFM and an air pressure of 26.44mm H20, at 65 dBA, and look at the differences in design, you’ll notice a few things.
http://www.xtremesystems.org/forums/...1&d=1157160502http://www.xtremesystems.org/forums/...1&d=1157160514
First off, besides the values I just stated that differ from the GFB, this single propeller TFB model has to spin at a much higher 4600 RPM and suck up 2.45A/29.40W of power to achieve this! That single propeller has to work much harder than a dual propeller design. That extra RPM is also going to produce more noise as a result, and so is the added resistance against that single blade.
Of course, there are a lot more differences between these two designs that cause these different values.
I’m sure you’ve all noticed that while the GFB1212VHW is superior to the TFB1221GHE in several ways, it lacks the air pressure that the TFB can achieve. Remember, higher air pressure is very important for air flow. CFM doesn’t mean anything, unless that CFM is being pushed through and around obstacles by the air pressure, across the area you need to cool.
It’s a double edged sword. A fan can be rated for 200 CFM, but produce only a small fraction of the pressure that a fan rated for much less CFM can pump out, while in comparison, a fan with a high air pressure may only produce a small fraction of the CFM as another fan with much less CFM. You have to pay close attention to these two specs, when shopping for a fan, while also comparing them against dBA, power consumption, weight, RPM (which really isn’t that important), bearing design, quality of materials, life span, etc.
The TFB series, also has a series of static stator vents on the exhaust side of the fan (seen in the second picture), that helps clean up and direct airflow, reduce resistance, and helps eliminate back pressure caused by anything blocking its airflow, like a guard or a filter. However, the GFB series does not have this feature, because it doesn’t need it.
So why is the air pressure less than the TFB1221GHE? While the GFB has only three blades per fan, the TFB series features a turbine like fan design, meaning it has three times the blades, a total of nine blades. By having more blades covering more of an area and doing more work, a turbine fan design produces much more pressure than the standard three blade designs, and air pressure always increases as you raise RPM, however so does dBA. Again, a double edged sword.
Secondly, the more powerful TFB fans, have elongated blades which reach out longer than the front of its frame, acting as scoopers (seen in the first pic). While making the use of fan guards difficult, this feature adds to the efficiency of the design, allowing the fan to reach out and grab a little more air to push, further boosting its CFM and pressure.
So this is why the GFB, while more efficient in noise, use of RPM, and CFM, lacks the air pressure that the TFB series can produce. If the GFB featured a turbine fan design and these added "scoopers", the air pressure would be dramatically improved.
I hope you all enjoyed reading my article. :)
