Re: [Phys-l] physics of dissipation (was: T dS versus dQ)

[chuck britton <cvbritton@mac.com>]

Time is indeed a variable that doesn't get a lot of attention in the 
Thermo field.
These posts have been quite interesting and informative.

I'm going to try to generalize a bit - not proofs or claims of 
over-arching 'great truths' intended.

I took a rather unorthodox intro chem course  back in the '60's. 
Co-taught by two world class research chemists. One a 
thermodynamicist and the other an analytical instrumentation guy.
One 'topic' that sticks in my mind was the discussion of extracting 
useful energy from chemical combustion - specifically - slow burn vs 
explosion. (external steam boiler vs internal combustion comes to 
mind.) There were two different 'names' for the 'useful' energy 
available under these two conditions. (I'm sure that someone will 
provide the names and symbols for these.)
The slow-burn always came out on top.

and now - really stretching here - is there any generalization that 
relates to the recent (short lived) discussion of 'Residence Time').

Are there counterexamples available where quick make less entropy than slow?

Thanks for some great discussions folks ! ! !


At 8:51 AM -0700 1/14/10, John Denker wrote:
> The repeated assertion that the compression of the gas
> is the same no "matter whether done slowly or quickly"
> is completely untenable.
>
> To summarize: 
>  -- slow and gradual ==> isentropic, non dissipative
>  -- sudden           ==> dissipative