4 ms·

As a former atmospheric science T.A., I'd give that a D for at least knowing the word adiabatic. I'd expect adiabatic cooling from air expanding as it rises up

As a former atmospheric science T.A., I'd give that a D for at least knowing the word adiabatic. I'd expect adiabatic cooling from air expanding as it rises up the tube. Expansion is in the vertical direction of course. Nothing magic is going to affect atm pressure inside the tube; it's the weight of the column of air above it, just like everywhere else. I'm not so sure that the benefits of removing mixing would be significant compared to slowing from having a boundary layer all the way up. Does it work because insolation on the chimney itself heats the air inside warmer than its environment? Maybe I should just look at the paper.

mannykannot 9y ago
> I'm not so sure that the benefits of removing mixing would be significant compared to slowing from having a boundary layer all the way up. For practical purposes, the expansion of a rising thermal can be treated as adiabatic, because the mixing is not large in comparison to the volume. One consequence of the flawed argument presented on the website is that this system will not run continuously, but only when the lapse rate is that of adiabatic expansion (dry or wet, depending on the relative humidity) - i.e. the same condition as for natural convection (and if there is condensation in the tube, that complicates the matter.) On the other hand, I suppose, if the proposal has some validity, that pumping air into the tube to raise it through an inversion might allow convection to start where it has not done so naturally, or to trigger conditional convection (where the air is buoyant only once saturated, on account of the release of latent heat as it rises further.)) I am also wondering about the Venturi effect, and the assumption that the tube will support itself against outside pressure with a 300mph wind blowing through it - though that figure comes from what appears to be a fatally flawed calculation.

mannykannot 9y ago

> I'm not so sure that the benefits of removing mixing would be significant compared to slowing from having a boundary layer all the way up. For practical purposes, the expansion of a rising thermal can be treated as adiabatic, because the mixing is not large in comparison to the volume. One consequence of the flawed argument presented on the website is that this system will not run continuously, but only when the lapse rate is that of adiabatic expansion (dry or wet, depending on the relative humidity) - i.e. the same condition as for natural convection (and if there is condensation in the tube, that complicates the matter.) On the other hand, I suppose, if the proposal has some validity, that pumping air into the tube to raise it through an inversion might allow convection to start where it has not done so naturally, or to trigger conditional convection (where the air is buoyant only once saturated, on account of the release of latent heat as it rises further.)) I am also wondering about the Venturi effect, and the assumption that the tube will support itself against outside pressure with a 300mph wind blowing through it - though that figure comes from what appears to be a fatally flawed calculation.