"Ignoramus10802" wrote in message
...
On 2009-10-29, ATP* wrote:
True. Yet I still hear this type of "reasoning" all the time. Should be a
simple concept even for the technically challenged, for example, people
who
argued here that you can compress air and allow it to expand (while doing
no
useful work) with no loss of energy.

That would be almost possible if compressing and expanding was done
very quickly, before compressed air cools.

i

But it has to be done *awfully* quickly. That's why there's a minimum
cylinder size for diesel engines -- something like 300 cc. Below 3,000 rpm
or so, the compressed air cools too quickly to ignite the fuel. And heat
transfer gets worse as compression goes up.

--
Ed Huntress