Re: [DML] Engine cover screens - necessary or not?

[Peter Lucas <lucas@xxxxxxxx>]

No, that is not exactly what "heat soak" means.   The term is properly used in two ways:

1) "Something absorbing heat from something else until it stops functioning properly".  So, for example, an intercooler can stop doing its job if its local ambient temperature gets too high.

2) "Heat moving from a hotter part of a system to a cooler part, making the cooler part hotter, and the hotter part cooler".    So, for example, if you turn off an engine, the coolant stops flowing, so the parts of the engine that were being cooled by the coolant can get significantly hotter by heat soak from deeper in the engine, but only because those deeper parts are getting *cooler*.  This is simply the system moving toward thermal equilibrium. The Second Law of Thermodynamics ensures that the *average* temperature of the engine constantly goes down, starting the instant you turn it off. 

If you disagree with this, I ask again:  If the engine is off but getting hotter, where is the heat coming from?

You can read about heat soak here, courtesy of our Lotus friends:

http://www.lotustalk.com/forums/f25/please-explain-heat-soak-50397/

--Pete Lucas
VIN #06703

On Feb 22, 2013, at 2:12 AM, Martin Gutkowski <martin@xxxxxxxxxxxxxx> wrote:

> It's called heat soak. The moment the engine is switched off, the coolant stops flowing and for a period the engine actually gets hotter. It's why I don't like turning the car off when the fans are running.
> 
> Some cars have some pretty complex electrically driven water pumps to prevent heat soak issues
> 
> Martin
> 
> Sent from my BlackBerry®
> 
> -----Original Message-----
> From: Peter Lucas <lucas@xxxxxxxx>
> Sender: dmcnews@xxxxxxxxxxxxxxx
> Date: Thu, 21 Feb 2013 17:28:46 
> To: <dmcnews@xxxxxxxxxxxxxxx>
> Reply-To: dmcnews@xxxxxxxxxxxxxxx
> Subject: Re: [DML] Engine cover screens - necessary or not?
> 
> 
> On Feb 21, 2013, at 6:08 AM, jtrealtywebspannet <jtrealty@xxxxxxxxxxxxx> wrote:
> 
>> Once the motor stops the heat builds up quickly.
> 
> I'm a little skeptical about that one, Dave. Sounds thermodynamically impossible.  If the motor isn't running, where is this heat coming from? None is being generated, so the temperature can only go down.  It is possible that the *compartment* could get hotter when the car isn't *moving*, but I don't see any mechanism by which the engine running or not would matter in a D.   Now, an engine with a mechanical fan might be another matter...
> 
> Am I missing something?
> 
> --Pete Lucas
> VIN #06703
> 
> 
> 
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
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