Very key point. If you want to take heat out of a box, you're far better to point the fans out and let them draw in cool air from the other side than to point the fan in and "blow cool air in". Here's why.
When you blow a fan into a box (K2, PC, or your house in the summer) you're blowing into a confined space and the pressure goes up. That increase in pressure fights against the fan and reduces the amount of air that flows. Mechanical efficiency and air transfer go down. Turn the fan around and blow it out of the box into the "universe". The outside world cannot be pressurized by the fan so the fan moves air more effectively. And I believe the air being blown into the box helps to set up dead zones where hot air can pool up. The flow through the box is better in the exhaust case. I've tested the theory both with my computer and with using fans to cool my house in the summer. In both cases, better cooling is achieved with fans blowing out than in. Makes me wonder about reversing the fan in the K2. It just might make it more effective and allow it to say on low longer. I have to open it up to tighten the HW and insert one more shield spring so I'll get another chance to give it a good lookin' over. - Keith N1AS - - K2 5411.ssb.100 - -----Original Message----- From: Don Wilhelm The fact that an exhaust fan flow cools objects better than blowing air onto a surface is a bit counter-intuitive because standing in the downstream side of a fan feels cooler to the skin - but that is only because of evaporation. Careful measurement will show that the cooling effectiveness for an object like a heat sink is more effective by moving the heated air away from the object. Getting the heat away is the objective, and blowing on it is less effective than exhausting the heated air. _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
