| [GMCnet] John Biwersi's new direct replacement fan [message #268935] |
Mon, 05 January 2015 19:57  |
Advanced Concept Ener
Messages: 112
Registered: December 2014
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Senior Member |
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The HP required to drive a fan is proportional to the cube of the flow and the square of of differential pressure produced by the fan. That means if the fan flow goes up by two the HP goes up by eight. If you flow more air over a fixed area of resistance the differential pressure drop across the area goes up by the square. Don’t be trying to save HP by small increases in fan efficiency. The fan noise is caused by air velocity passing through a restriction or the air backing up in the fan because it can’t produce enough pressure to move the air out of the blade. If you have 10 blades instead of 7 chances are the velocity across the blade is lower and probably more quiet. Drag on a smooth sheet metal blade probably won’t make that much difference from a smoother plastic blade in our application at our velocities. The HP to be saved is in the clutch and fan speed. The thermostat limits the water flow to reach setpoint temperature of the stat. Trying to control fan speed from radiator water temperature means you are fighting the thermostat. You would probably want to control the oil temperature (assuming no bypass) back to the engine to control fan speed and let the thermostat take care of the water temp. The idea of using an electric clutch and using pulse width modulation to control oil temperature sounds very do-able and very interesting. You can buy an electronic controller (with remote setpoint dial) that senses temperature and outputs pulse width modulation for the fan clutch for about $12.00. (check Ebay) So who has the part number for the electric clutch? I think I also found a clutch that uses a remote strap-on sensor to control it. No electronics and no complications. If you can provide the right amount of air for only the cooling you need than you have optimized the process and minimized HP.
Jon Darcy
aces4nrg@gmail.com
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