Date: Thu, 29 Oct 1998 14:16:02 -0800
Reply-To: YauMan Chan <YauMan@CCHEM.BERKELEY.EDU>
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: YauMan Chan <YauMan@CCHEM.BERKELEY.EDU>
Subject: Re: Fridge ? - No? Fans!
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I think most DC fans used in computers and electronic circuits will work for you.
Commonly referred to as "Muffin" fans or "Boxer" fans, they are made by a number of companies - Roton, Toyo, etc. They are square and comes in three popular sizes: 5" (4.7"), 3" (3.14") and litte 1.5" for use directly over CPU chips. (there are a lot more odd ball sizes!) There are two very important classes.. the one with real ball bearing and those that use "bushings". The one for a Pentium chip that has ball bearing cost about $25 and the same size without ball bearing is about $10 (3" with ball bearing is about $20 and $8 without!) The differences is of course the one with ball bearing will last a lot longer and quieter.
A typical 3" muffin fan pushes about 30 CFM (cubit feet per minute) and the one for computer CPU chips pushes about 2.0 - 5.0 CFM.
The amount of current drawn is all over the map. The typical 3" fan running on 12Vdc consumes 1.0 Watts. Divide that by 12 (W=IxV) give about 83 milliamp. I have seen 8 Watt 3" muffin running at 12Vdc but that's pushing 90 CFM. Data for little 1.5" CPU fans are more difficult to come by. Most spec sheets don't list amps or wattage for little fans since that is not consider an important criteria for selection...instead they list fan life in MTBF (mean time between failure - 20,000 hours being typical) The last time I remembered measuring one, it drew less than 50 milliamp.
So, if you have an 80 Amp Hour battery, and your little fan draws 80 Milliamps, you can run the fan for 1000 hours before the battery is drained!
You can buy these fans from most electronics parts outlets or catalogs. My favorite is Jameco Electronic components. (www.jameco.com). For total mindboggling variety, try Newark Electronics... however, I don't know if they still sell to individuals. When I ran an electronics lab in Boulder, I got all my electronic parts from Newark. (If you are into electronic gadget, the 1500 page Newark catalog is the one to have - get one from www.newark.com!)
Yau-Man Chan
87 GL.
>>> Blue Eyes <lvlearn@MCI2000.COM> 10/28 1:08 PM >>>
<clipped>
Does anyone know of any suitable small super low current draw 12 volt
DC fans? If so, please post contact information, current draw,
price, etc. Also, what would be a nice way to power this ONLY when
the main burner heat is driving the refrigeration cycle? That feels
like the right approach to me. Doesn't this appeal to the inventive
spirit of you creative guys like Dave B.? No used three pound boiler
controllers please. Keep saying this: Simple, compact, reliable,
cheap, elegant. Say it, and designs will come.
>>
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