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Re: Coolant flow restriction explained !

To: Randall Young <ryoung@navcomtech.com>
Subject: Re: Coolant flow restriction explained !
From: Joe Curry <spitlist@gte.net>
Date: Tue, 27 Jul 1999 13:57:32 -0700
Cc: "Triumphs (E-mail)" <triumphs@autox.team.net>
References: <01BED835.FCF39240.ryoung@navcomtech.com>
Randall,
While I don't dispute the referenced passage, I think there is a bit (if
not a lot) of truth to this story you have been hearing.  Here is my
explanation of the dynamics of what happens.

In order for the heated water to be cooled, it has to transfer its
energy to the heat sinks (cooling fins) in the radiator coils.  If it is
flowing too rapidly through the radiator, the amount of energy that is
absorbed by the fins is minimized, and reduces the effectiveness of the
radiator.

On the other hand, restricting the flow to a certain extent will cause
the water to stay in the engine too long and pick up more heat than is
dissipated by the radiator.  The trick is to find that magic point where
the water flows at just the right speed to dissipate just enough heat to
keep the engine at the desired temperature.  That is why the thermostats
are temperature rated to open at a desired temperature.

Of course this is dependent on a number of things:

Ambient temperature (look at all the trucks in the wintertime that have
the entire radiator covered with vinyl to keep the temperature up)

The particular design of the cooling system (some work much better than
others)

How old the car is (as referenced, older cars typically used a lower
pressure system)

The condition of the cooling system and the engine.

WARNING: DISCLAIMER AHEAD!

Any correlation between the above description and reality is purely
coincidental.

Regards,
Joe 

Randall Young wrote:
> 
> Listers :
> 
> For many years, I've been hearing the story that "you have to have a
> thermostat, or a restrictor, because otherwise the water flows through the
> radiator too fast and doesn't get cooled".
> 
> For just as many years, it hasn't made sense to me.  The faster the coolant
> circulates, the closer it keeps the radiator fin temperature to the engine
> temperature, which lets the radiator radiate more heat.
> 
> At last, I've found an explanation that makes sense !  Check out
> http://www.stewartcomponents.com/techtip3.htm, especially the paragraph
> that starts "Years ago".  It basically says the problem is that the extra
> flow through the radiator increases the pressure at the top of the
> radiator, which causes the (low pressure for our LBCs) radiator cap to blow
> coolant out the overflow, just like it was overheated !
> 
> Randall
> 59 TR3A "daily driver wanna be"

-- 
"If you can't excel with talent, triumph with effort."
 -- Dave Weinbaum in National Enquirer

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