General Wesley R. Elsberry on 27 Apr 2009 07:42 am
An Aid to Thought
Over at “wattupwiththat”, a commenter opined some time ago:
I remember when I was a kid playing with a bicycle pump that compressing a gas heats it up. Is it possible that some of the high surface temps on Venus are because of that pressure?
Why not have a cold beer to help think that one through?
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on 27 Apr 2009 at 12:21 pm 1.George said …
The same principle worked to warm the air flowing out of the mountains in Colorado.
Some I suspect that as atmosphere moves up / down cooling and warming takes place from expansion and compression just as it does on earth. Although, I suspect that venus is warm/hot becuase of the abudnance of greenhouse gasses and proximity to the sun.
on 27 Apr 2009 at 2:27 pm 2.Austringer said …
The main thing I was critiquing was the notion that the Pv = nRT at time of compression has much if anything to do with the value of T some millions or billions of years later. The fact that the CO2 in a beer had to be pressurized at some point doesn’t mean the beer can never thereafter be cold.
on 27 Apr 2009 at 5:26 pm 3.George said …
Quite right. I got your point. Mine was to acknowledge that localized adiabatic heating of the atmosphere is likely ongoing on Venus similar to the Earth. But that such a process was a result of a more dominant weather system on Venus driven by solar radiation, as on Earth. And that a dose of greenhouse gas heat trapping exacerbates Venus’ plight.
But of course, you already know this.
on 08 May 2009 at 1:11 am 4.jahigginbotham said …
But what if (starting at room temperature and pressure) you were compressing hydrogen or helium?
on 09 May 2009 at 5:03 am 5.Austringer said …
There’s nothing special about hydrogen or helium with respect to change in temperature with change in pressure.
When I get a SCUBA tank filled, air is pressurized to a bit over 3000 PSI. The tank gets noticeably warm. Most places put tanks being filled in a water bath, which is far more effective at distributing heat from the tank than air. But either way you go, the tank of pressurized air doesn’t remain at a high temperature; it eventually equilibrates with ambient temperature. The internal pressure is still at 3000 PSI, but there’s no persistent temperature increase due to the fact that it is under high pressure.