Instrument Rating
Joined: Dec 2001
Posts: 546
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From: europe
Timothy
I think we are in agreement.
Bookworm
I was probably being over picky, but while case 3 in your post correctly describes sublimation, the important atmospheric phenomina of lapse rate does not include dry air except as a theoretical possibility, and not at any meaningful pressures on the water phase diagram, so I hold that while precise wording is not essential for everyday conversation, it is helpful when considering meteorological conditions,so case 4 in your post is not a reality.
I think we are in agreement.
Bookworm
I was probably being over picky, but while case 3 in your post correctly describes sublimation, the important atmospheric phenomina of lapse rate does not include dry air except as a theoretical possibility, and not at any meaningful pressures on the water phase diagram, so I hold that while precise wording is not essential for everyday conversation, it is helpful when considering meteorological conditions,so case 4 in your post is not a reality.
Joined: Aug 2002
Posts: 0
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From: Surrey, UK.
Hmmm, we seem to have come a long way from whether IR's are worth the candle.
It is exactly these sort of semantics that determine your results in the (CAA/JAA) IR writtens - so not a wasted effort, Timothy
It is exactly these sort of semantics that determine your results in the (CAA/JAA) IR writtens - so not a wasted effort, Timothy
Joined: Aug 2000
Posts: 3,648
Likes: 2
From: UK
I was probably being over picky, but while case 3 in your post correctly describes sublimation, the important atmospheric phenomina of lapse rate does not include dry air except as a theoretical possibility, and not at any meaningful pressures on the water phase diagram, so I hold that while precise wording is not essential for everyday conversation, it is helpful when considering meteorological conditions,so case 4 in your post is not a reality.
Both water and ice have vapour pressures. In the same way that water will evaporate if you blow an unsaturated air stream across it, ice will [whatever, involving change of state to vapour] if you blow an unsaturated (doesn't have to be perfectly dry) air stream across it. It is very much a reality.
Joined: Jun 2003
Posts: 13,787
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From: EuroGA.org
Interesting discussion. Direct transition from solid to vapour is what happens on the N and S poles. It definitely does happen.
What would interest me is how quickly would clear ice clear (say in mm per hour) in a 140kt parallel airstream at say 35% RH (roughly today's conditions) at say -5C.
I bet somebody has measured this.
The reality will be different with the front window, partly because the spray from the TKS de-iced prop covers it with mist, and partly because it can be heated from the inside. I suspect the latter is likely to be not significant due to poor thermal conductivity of polycarbonate.
What would interest me is how quickly would clear ice clear (say in mm per hour) in a 140kt parallel airstream at say 35% RH (roughly today's conditions) at say -5C.
I bet somebody has measured this.
The reality will be different with the front window, partly because the spray from the TKS de-iced prop covers it with mist, and partly because it can be heated from the inside. I suspect the latter is likely to be not significant due to poor thermal conductivity of polycarbonate.
