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Old 01-16-2012, 06:09 PM   #93 (permalink)
Josh8loop
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Quote:
Originally Posted by Air-Hybrid View Post
That's interesting Josh. I'd like to hear more about your experiences making DIY heatpipes. What applications have you used them for?
I procured one for myself from a defunct 80s audio amp - it's literally a straight brass tube sealed off at either end. Though I haven't put it to any specific use as yet I suspect that most automotive apps would be to hot for it to work efficiently.



I have also considered using ultrasonics for mist creation, but one thing that might negate its efficiency gains is having to convert energy 3 times (mech-to-electrical-to-mist) with ultrasonic as opposed to once with a mechanical injector pump. Also I would like to get some figures on how much (if any) having hotter water would help it atomise off the sonics. Gut feeling is that water just below boiling would require substantially less electrical energy to 'break-free' but this might be a false assumption.


The main issue I have with the OP's suggestion that steam rather than water can recover some of the waste heat rejected in the exhaust is that the argument runs counter to the process that makes a heat-engine work.


The heatpipes(2) I made were quite rudimentary but worked well. They were more like thermosiphons since they had no wick structure, and needed to be oriented with hot end lower than the cold end to work. I ended up using a 3' piece of 3/8"copper tubing and sealed one end with solder. I dribbled a small amount of acetone into the tube, dipped the tube in chilled water, applied a vacuum to the pipe, and hammered the end until it was pinched off. After it was pinched off from the slow hammering, I soldered the end shut. The other one I made was similar in construction, but I pinched the end shut with a vice, and soldered it shut. They both worked well, and would transfer heat from one end to the other(3 feet) in around 20-30 seconds. Solid copper that long would take a hour to do that.

There are much better construction methods out there than I used, but it proved to me that a functional unit could be home brewed. Wick material could also be inserted to allow multiaxis functionality-you would want to select a wick material that is compatable with the working fluid. Also, water, alcohol, and many other fluids can be used as the working fluid and don't necessarily need to be under vacuum.
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2002 VW Jetta TDI 5-speed(completed 01M-5-speed swap at 155K miles) 45 MPG City with the 01M, 5-speed 60+ MPG City. Nokian Entyre Low RR Tires. Experimenting with the "Hybrid" 205 Deg F T-stat:

http://forums.tdiclub.com/showthread...=306799&page=4

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