[AR] Re: Orions and PDEs (was Re: More MAX delays.)
- From: Jim Davis <jimdavis2@xxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Tue, 28 Jan 2020 19:57:14 -0600
On 1/28/2020 2:16 PM, Norman Yarvin wrote:
The thing is, if the pressure were higher after expansion, wouldn't
that have to mean it was higher before expansion, too?
Yes, Indeed it would. Constant volume heat addition will result in a
higher pressure and a higher temperature than the same amount of heat
being added at constant pressure. The difference is that the constant
volume heat addition results in a lower entropy increase than the
corresponding constant pressure heat addition. This means the Humphrey
cycle rejects less heat which means more of the heat added is doing work
which means the cycle is more efficient.
And if you
pumped up your conventional engine to that same higher pressure,
wouldn't it have the same efficiency?
Indeed, it might have higher efficiency. But we're comparing cycles
with the same pressure ratio.
Jim Davis
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