[DeTomaso] To thermostat or not to thermostat

[Ken Green]

Actually, I think convective heat transfer involves the expansion of a heated fluid (usually air) and rising resulting in heat transfer.  I think we are dealing with conductive heat transfer.
   
  I think the big question to ask is the flow rate for a given radiator where the flow becomes turbulant.  Seems like you'd like to at least reach that level.
   
  The big radiators I picked up for Dennis (MD) and myself are huge single pass radiators which were made for use on Super Speedways.  Seems like the flow would be pretty slow and I really don't know if it is turbulant or not.  But they do have a very large volume, so the water is in them for a longer time.  I'll send an email to the manufacturer (Ron Davis) and see what they say.
   
  Ken

Don Thomas <dtpantera at gmail.com> wrote:
  Here is the engineering explanation that I got from my friend (the
engineer's engineer and rocket scientist) at Boeing who deals with
thermodynamics everyday.

"Turbulent heat transfer (flux) coefficient (Nusselt number
http://en.wikipedia.org/wiki/Nusselt_number ) is linearly proportional to
the Reynolds number. The Reynolds number itself is linearly proportional to
velocity. Don't feel bad - this wasn't covered in your basic engineering
thermo class. It's in the realm of convective heat transfer. "

Which what he is basically saying... you want high rate of flow in order to
induce turbulence to transfer heat more efficiently.

This is also mentioned on the Stewart components website at the bottom of
one of their tech tips page. i.e.:

"Metal temperatures always increase when you slow the water pump down."

http://www.stewartcomponents.com/tech_tips/Tech_Tips_6.htm

So if someone tells you slower is better... that isn't true for cooling.

I hope that helps.

-dt





> Thanks, Will.
>
> I think the idea is that if the water flows through the system too quickly
> it can't absorb the heat properly.
>
> My Robert Shaw thermostat didn't perform any better than the lesser priced
> NAPA 197. Just my experience.
>
> Jim Gray
>
> -----Original Message-----
> From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com]On
> Behalf Of Will Kooiman
> Sent: Tuesday, May 20, 2008 9:57 PM
> To: detomaso at realbig.com
> Subject: Re: [DeTomaso] To thermostat or not to thermostat
>
> I agree with Mikey about running the Robert Shaw 333-180 thermostat. There
> aren't any downsides to running a thermostat - unless you get a cheapo
> thermostat - which the Robert Shaw is not.
>
> I don't buy the idea that you have to slow down the water or it won't cool
> enough. It makes more sense to me that if you don't restrict the water,
> it'll cool too much. So, in other words, if you're not running a
> thermostat, and the engine is running too cool, put a smaller restrictor in
> place. This only makes sense in a controlled environment - like dirt track
> racing.
>
> This is one of those topics that, in my opinion, we over analyze. Use a
> proper thermostat so it'll stay hot enough. Get rid of the air in the
> system. Make sure the fans are working properly. That's all it takes. Oh
> yeah, stainless pipes/tanks and green stripe hoses, but that's more for
> corrosion/leak protection - not cooling.
>
> By the way, I haven't had a high pressure/swirl tank in over 4 years. I
> haven't put many miles on my car the last year (mostly due to traveling for
> work), but before that I drove it 1,000 miles a month. The only time it
> overheated was when the fans stopped working - and that was in 100+ degree
> weather in stop/go traffic, up hill, with no shoes on.
>
> Will.
>
>
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