sethoflagos

I did my apprenticeship in a paperboard mill where we regularly ran a grade for conversion to fish boxes for storage and transport of frozen fish. Typical product range details can be found at https://diepvriesurk.nl/en/packaging/carton-packing/ Storing such boxes in strong direct sunlight would not be recommended. Why would anyone want to do this?

Guess I'm fortunate that all my stainless polishing needs (trumpet valves mainly) are quite adequately met by Duraglit. Well-over 50 years regular use and no freakish accidents yet, touch wood.

GRIND GRIND GRIND GRIND GRIND GRIND GRIND GRIND GRIND GRIND GRIND GRIND buff buff buff Many. This is a typical medium duty one for an industrial workshop. From whatever a decent domestic power drill costs these days upwards. Consider looking at taking a training course in basic metalworking first. It is REALLY easy to lose an eye or a finger with these things if you get it wrong.

It was indeed. There are quite a few episodes of Up Pompeii floating around Youtube space.

The 2nd Law formally states that the primary prerequisite for an isentropic process is that there is no nett exchange of heat with the surroundings. Since heat transfer (and other dissipative processes such as friction) are relatively slow processes then fast processes lean toward the isentropic. Like a power station? Near isentropic compression and expansion through the boiler feedwater pumps and steam turbines respectively are extremely rapid. But the working fluid spends far more residence time exposed to the heat transfer surfaces. The steam condenser is intrinsically near isothermal in operation, and although the radiatively heated water wall is not, the ancillary surfaces: deaerator, economiser, superheater and reheater bundles; are sized and positioned so as to maximise overall station thermal efficiency. Which is equivalent to saying that they are designed to fit the station cycle to the Carnot optimum theoretical cycle as closely as possible. I guess this is not what you envisage when you write 'engine'. A better word may be 'machine' which has a precise engineering meaning: a device that transforms one form of energy into another. Heat engines, electrical transformers and power stations are all machines by this definition.

Fast processes tend towards the isentropic. Efficiency and overall economics work hand in hand. Isothermal processes in extremis call for infinite cycle time and/or infinite heat transfer area. The economics just don't work as a practical proposition so we have to compromise. There is really no such thing as a Carnot design as it is an abstract theoretical concept: not a tangible object like an Otto or Stirling engine. Some designs can approach the Carnot limit more closely than others and that's all there is to it. Closer approaches need bigger budgets with ever-declining potential Return On Investment.

Bump.

'Half-empty' is a misleading concept when your gas density is >80% of the liquid density as in this case. Even if the receiving cylinder were free of liquid, at pressure it's still > 80% full. A syphon discharge from below the liquid level of the main storage vessel will definitely get a few more pounds delivery, though some of this will evaporate on transit. If the deficit is so important, then you could consider placing the receiving cylinder in a bath of iced water both prior to and during filling. This will condense everything coming in from the supply vessel. Even if the supply vessel pressure falls to 40 bar or so, the receiving cylinder will repressurise when returned to ambient so maybe think twice before exceeding the cylinder's rated CO2 weight capacity.

I've been a heavy smoker since I was 19. Just background fact. After maybe 17 malaria-free years in Nigeria, I eventually came down with it in 2016 (P. falciparum) and running 400 C I was immediately hospitalised for 3 days on a combination quinine/paracetamol drip. This repeated 2 years later. On both occasions, I had three days of no urge to smoke whatsoever, which was a really big deal to me. Normally two hours abstention pushes me into a tense, hyperactive somewhat sociopathic state that can alarm those around me. Basically. I smoke to stay in employment (and married!). So any way out of this circular trap would be highly beneficial. Of course, I discussed this with the medical staff responsible for my treatment, but they showed not the slightest interest whatsoever. Which didn't impress me much. I doubt that it's malaria that will kill me in the long run. When the treatment finished, immediate cold turkey. A third infection a couple of years ago I self-medicated with artemisinin/lumefantrine combination (+paracetamol as antipyretic) which worked but didn't give the same respite from my nicotine addiction. Has anyone the slightest inkling of what may be behind the addiction respite? I can't find anything relevant online, and I've looked. Numerous times.

Introducing the air at the base would require much more compression, and since the expansion occurs overwhelmingly in the top couple of hundred metres, that's where the suction will be generated in any case. There are such animals as flexible submarine hoses (eg here), but these are highly complex composite builds that have other issues to address. I would have thought that rigid wall piping was mandatory whatever the pumping method. I'm not clear on what sort of flowrate we are supposed to be considering now. For the Mm3/s range, a somewhat buoyant cylindrical honeycomb structure a couple of km in diameter held in place by a suitable spread of anchor chains strikes me as potentially feasible. It could conceivably be constructed predominantly from a couple of km3 of reprocessed plastic waste which would be one approach to carbon sequestration. Whether appropriate or not for the climate, as a technical challenge, this topic has some very interesting aspects. It's still performed some PdV work on its surroundings, so yes, there will be a corresponding if small adiabatic temperature drop.

Beat them to it by spontaneously launching your own preferred non-contact greeting.

PS: I was going to say something about whether polyethylene was up to handling the considerable tensile forces involved, but perhaps we can save that for later. And for >>1m in the previous post please read <<1m. I really must get my eyes checked.

Actually looking at this a little more closely, if the 1 metre diameter pipe (say 0.785 m2 cross-section) were to oscillate the full one metre wave height (crest to trough I assume) and back every 5 seconds then 0.785 / 5 x 3600 x 24 = 13,572 m3/d at 100% efficiency doesn't it? So how does the quoted 13,000 m3/d amount to 60% efficient operation? Now I'm a little suspicious. The pipe is tracing a displacement ca. h = 0.5 sin (1.26 t) m where 0.5 - wave height / 2, 1.26 = 2 x pi / wave period Hence pipe velocity dh/dt = 0.628 cos (1.26 t) m/s Pipe acceleration d2h/dt2 = - 0.792 sin (1.26 t) m/s2 Mass of pipe contents ~ 0.785 x 1,025 x 1,000 = 804,625 kg Maximum upward force exerted by buoy = 0.792 x 804,625 = 637,007 N = 64,954 kgf neglecting friction So the buoy must be capable of developing a lift of 64,954 kgf with >> 1 m displacement from the ocean surface. Clearly some displacement is required so let's take 0.1 m Buoy cross-section >= 64,954 / 1,025 / 0.1 = 634 m2 hence buoy diameter >= 28.4 m That's pretty big even by single buoy mooring standards but I guess it can't be ruled out as a concept. For a moment I thought we were looking at a supertanker hull.

An interesting paper. The technical feasibility and volumetric scale factor of the scenario is defined by the following: The Kithil reference was rather difficult to locate but I eventually found it here. So the pumping principle is essentially that of a wave-powered shaduf (no disrespect - it's just a mental picture). Perhaps we should note that wave height and period given here are roughly in tune with a consistent 20 knot wind which implies installation in the 'roaring forties' for example..

The game changer appears to be arbitrarily reducing the seawater flowrate by a factor of 106 and moving the seawater intake from the abyssal plains to 3 parts of the way up the continental rise. Are we done with the original thread?

At the instant you posted the OP, it is more than arguable that the universe of the current instant didn't exist. It had no mass, possessed no energy, occupied no space. In short, it was the absolute nothing you referred to in your OP. Yet now the present exists in all its spacious, energetic enormity. How did it arise from absolutely nothing? If absolute Now has a perfect inverse Now such that Now + Now = 0, then perhaps they can and do arise spontaneously in a manner consistent with all our expectations of conservation of funamental properties, and separating as Now tracks its property gradients in one time direction while Now tracks its own back into the past. Hence Now deevolves back into Then. at exactly the right time to meet the instant you posted the OP whereupon Then + Then = 0. Hence the past also vanishes for eternity into absolutely nothing. And so on until the first Dawn where there was no Then to annihilate with. So Dawn and Dawn evolved in perfect mirror symmetry. For a better explanation of this inverse universe idea see Advanced Waves Detected (John G. Cramer) on which my amateur musings borrow heavily.

I'lll take that as a 'No' One pumping method that may be worth considering is Gas Lift. By sparging compressed air perhaps 200 - 300 m below the top of the pipe via an array of nozzles, the density of the mixed fluid above is substantially reduced generating the pressure difference necessary for the desired flowrate. Not cheap, but it's a practical proposition. And it would help with oxygenation too.

I gave the links. You're just pretending I didn't. However, there seems little point in insisting on 3-digit accuracy when your OP proposal fails to meet its objective by such a phenomenal number of orders of magnitude. Orders of magnitude estimates are all that is necessary here. I remind you of those objectives: In other words, you are seeking to duplicate the natural oceanic upwellings in the ocean 'deserts'' (which are btw underlain predominantly by abyssal plains at depths of 3,000 to 6,000 m). As @Ken Fabian and others have informed you, the natural upwellings typically involve flows of tens of millions of cubic metres per second span tens of kilometres, and are powered by TeraWatts of solar energy.. Any proposal to duplicate them in areas where they don't occur naturally MUST have at least the same number of digits. Your practical proposal? When I read this, my initial impulse was to check the OP wasn't dated April 1st. But apparently you were being serious. Do you still stand by your original proposal or not?

No, it was made before I posted to this thread. I'm a little curious. Why are you spending so much time and effort trying to establish that something that I'd previously and voluntarily described as 'a bit of nonsense' was actually a bit of nonsense?

Whoever constructed this chart has assumed water to be incompressible. Many people do. However, the bulk modulus of water is not infinite, it is 2.2 GPa. The over pressure due to 4,000 metres of seawater is around 2% of the bulk modulus so consequently the density at this depth is around 2% higher. So I guess that's the basis of the 1,050 kg/m3 figure and clearly the cartoon presented is significantly inaccurate. But that's all by the by. Something has to persuade the flow to spread out horizontally at the top of the 7 km diameter pipe, and that's a flat topped mound of water oto 25 metres high. This provides the potential energy necessary to source a 10 metre deep, 20 m/s horizontal outflow at the pipe circumference. Hence the 2.5 bar/1000m and 1TW estimates still stand. . 6.3 m3/s vs 40,000,000 m3/s Didn't someone mention a bit of a scale disconnect earlier in the thread?

Here

Before anyone looks too closely at it, I should point out that while 2.5 bar/km is a reasonable order of magnitude estimate for pipeline pressure losses, the rationale I gave for the figure is a bit of a nonsense. Oops your kind rep just disappeared, so I guess someone has just woken up.

Just some back of envelope stuff. Recast the objective as the transport of a nominal 100 tpd of deep ocean dissolved iron to the surface. Typical deep ocean iron concentration (from here) seems to be around 0.5 nM which sets the pumping volume to a little over 40,000,000 m3/s. While it is correct that the external water column does largely support the pumping effort, deep ocean seawater density is generally taken to be around 1050 kg/m3 as ooposed to the 1024 kg/m3 of surface waters and that 26 kg/m3 difference does give a static pressure difference of around 250,000 N/m2 per 1,000 m. If upward velocity were negligibly small (really huge diameter pipe) then a 100% efficient pump would consume a minumum VdP of 1TW / 1,000 m. As we're already exceeding the electrical power consumption of China and haven't yet touched on friction losses, I see little purpose in pursuing this further. Tankering in liquid fertiser is a far, far more cost effective method of meeting the initial objective. Whether or not the initial objective was a good idea, I'm with @Ken Fabian (as usual).

@Genady opened my eyes somewhat a couple of weeks ago by suggesting I look into the extension of GR into a fifth dimension by Kaluza-Klein which seems to have been a catalyst for QED. A similar extension into a sixth dimension (if I understand correctly) led to Yang-Mills and thence to QCD. What seems odd to me is that having started with GR, why should extensions into yet further dimensions be expected to 'give birth' to a theory of gravity when GR already seems to have that one covered? Is there some reason why Ouroboros must swallow its tail like this? All particles we have ever observed are accounted for by these theories so what more do we need (other than some tidying up of the mathematics perhaps)?

Has physics stagnated for seventy years on this dilemma?