[NSRCA-discussion] Heat Sinks

Mon Aug 4 07:03:39 AKDT 2008

As in most projects, when you are 99% done, you only have 25% left to  do.  
That is how most projects in my work environment went.  I always  told the 
project managers that when they reported their project status and  I was usually 
right.  If I was wrong, they had more than 25% left to  go.....  

Don

In a message dated 8/4/2008 7:30:18 A.M. Pacific Daylight Time,  
gfowler at raytheon.com writes:

Anthony 

My new plane is 99.5% complete-all I have to do is  balance and align the 
wings-and then "re-learn" to fly. My kid just completed  the massive soccer 
"qualifying" tournament-6 games, two weekends, nothing  below 103F, so I am 
conditioned to start flying again.  

Gray  Fowler
Senior Principal Chemical Engineer
Radomes and Specialty  Apertures
Technical Staff Composites Engineering
Raytheon  

Anthony Romano  <anthonyr105 at hotmail.com> 
Sent by: nsrca-discussion-bounces at lists.nsrca.org  
08/04/2008 09:17 AM      
Please respond  to
General pattern discussion  <nsrca-discussion at lists.nsrca.org>

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General pattern discussion  <nsrca-discussion at lists.nsrca.org>    
cc
Subject
Re: [NSRCA-discussion] Heat  Sinks

Hi Gray,
Glad to see you still lurking.
First, saw  that technique to cool the batteries on the moon  rover.

Anthony

____________________________________

To: nsrca-discussion at lists.nsrca.org
From:  gfowler at raytheon.com
Date: Mon, 4 Aug 2008 08:51:48 -0500
Subject: Re:  [NSRCA-discussion] Heat Sinks

Guys 

Considering that I do not fly E, this may not work,  but here is a trick from 
the missile world where the electronics generate  massive heat in a small 
package (no air cooling at mach 3!!)  that must  be dissapated. 

Heat sinks work well but rely on intimate contact  with the heat source, 
which can be the actual problem-how to get the battery  heat into the sink with 
the odd shape of the battery packs and the flatness of  the aluminum. Since you 
guys know the operating temperature of the dischaging  batteries, choose a wax 
that melts just below your target temperature. Cast  the wax around the 
battery pack (you need a container or tub-super thin  aluminum). Then have the 
cooling fins-heat sink on top. When the batteries  heat up the wax will melt. This 
phase change will cool the batteries-then the  viscous liquid wax will also 
efficiently transfer the heat to the aluminum tub  and the aluminum heat sink. 
The heat sink will cool the wax which then cool  the batteries. 

After recharging, the batteries cool, the wax  resolidifies and it is ready 
to go all over again. Wax is light weight, the  aluminum tub-heatsink  would 
need to be custom fabbed and very thin-and  basically sealed.  Wax can be easily 
cleaned from the batteries if  needed. 

Just a thought

Gray Fowler
Senior Principal  Chemical Engineer
Radomes and Specialty Apertures
Technical Staff  Composites Engineering
Raytheon  

"Earl Haury"  <ejhaury at comcast.net> 
Sent by:  nsrca-discussion-bounces at lists.nsrca.org  08/01/2008 04:15 PM 
Please respond  to
General pattern discussion  <nsrca-discussion at lists.nsrca.org>

To
<bob at toprudder.com>, "General pattern discussion"  
<nsrca-discussion at lists.nsrca.org>    
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Subject
Re: [NSRCA-discussion] Heat  Sinks

Bob 

My thought is that  packs setting on something thermally conductive rather 
than insulating seems  better. Love your CO2 cartridge idea - wonder if AMA 
would consider that a  "gaseous boost". 

Earl 
----- Original Message  ----- 
From: _Bob  Richards_ (mailto:bob at toprudder.com)  
To: _General pattern discussion_ (mailto:nsrca-discussion at lists.nsrca.org)   
Sent: Friday, August 01, 2008 3:47 PM 
Subject: Re:  [NSRCA-discussion] Heat Sinks     I've been thinking about 
this, and I think  the best way would be sandwich thin pieces of aluminum between 
the cells  and extend past the edge of the pack. But I'm not sure I like the 
idea  of placing anything electrically conductive between the cells. Best to  
provide an air space between the cells and duct the cooling air between  them. 

Of course, if you really want some wow-factor in the  setup, you would have a 
thermostatically controlled cowl flap that only  opens up once the pack 
starts to go beyond the optimum temperature.  Maybe even an emergency cooling 
system - a small CO2 cartridge from an  air rifle might do. ;-)

Bob R

--- On Fri, 8/1/08, Jay  Marshall <lightfoot at sc.rr.com> wrote: 
The idea of a real heat sink, maybe  with the fins as part of the skin of the 
plane and in the airstream, and  the LiPo cell edges bonded to the sink with 
thermal compound, has some  merit and may require some investigation – if 
cooling is what we really  want. 

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