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Everything posted by sethoflagos

  1. Starting point without a doubt is Coulson and Richardson's Chemical Engineering: Volume 2A: Particulate Systems and Particle Technology, Sixth Edition. That's your broad brush introduction to the subject. But the range of application is extremely diverse - many, many specialist study areas with not so much common ground to unite them (or so it seems to me). If you have particular interest in some particular field, I may be able to give some relevant further references.
  2. Nearly. But it isn't the properties of the medium that are changing: it is whether or not the medium is flowing away from you toward the trains, which would delay your detection of the whistles; or flowing toward you from the trains, which would advance the detection. If you had no information on airspeed, say for instance you were observing via a remote video camera and microphone, your measurements of the (apparent) speed of sound would vary according to wind speed and direction wouldn't they? This is an example of Galilean non-invariance. Now substitute 'speed of light' &am
  3. In what circumstance would a medium be not at rest with respect to itself? Perhaps you intended "... at rest with respect to the observer", ie. a restatement of our 'still air' constraint. Could another restatement of this constraint be that observer and medium must be in the same Galilean reference frame? If so, then if the constraint was a necessary precondition, wouldn't this imply that the apparent speed of sound was not invariant under a Galilean transformation? I stress the word 'apparent' to distinguish between transmission over a measured distance in a measured tim
  4. Meteorites survive passage through the atmosphere, so perhaps you intend 'audible fireballs'. Even so, these propagate, initially at least, as supersonic bow shocks (sudden pressure discontinuities) rather than sound waves - at velocities dependent on their initial trajectories, and independent (for a while at least) of atmospheric properties. If one bolide were travelling towards the observer, and one away, they would be experienced as two blast wave fronts, the first perhaps considerably more powerful than the second. 'Pitch' is meaningless here. There may be some reflected afte
  5. 'Robotic skin' is a highly active area of current research, and your OP seems to require a relatively low resolution, planar version of the same thing. I'm puzzled why you pick impedance as the sensed property for this. Most work in this field has been focused on traditional resistance strain gauges, piezoresistance, and capacitance methods though Fibre Bragg Gratings (FBGs) seem to have received a lot of attention recently. The EU Roboskin Project is funded to the tune of about 5 million Euros: details at https://cordis.europa.eu/project/id/231500
  6. I clearly remember my grandmother starting the fire like that as the family gathered for christmas dinner. The sudden updraught caught her pet budgie by surprise and... it didn't end well.
  7. Natural draught is used extensively as a power source, but not in an obvious way. It doesn't provide enough power to pull combustion air through a commercial power station, but it contributes significantly in reducing the power requirement of the forced- & induced-draught fans. Similarly, natural draught cooling towers (and domestic coal fires for those old enough to remember them) don't need forced ventilation in order to maintain air flow.
  8. Would I be reasonably correct in thinking that the product of mean particle momentum and mean particle separation would need to be oto Planck's constant?
  9. That's actually quite interesting. Thank you +1 Maybe pointing to the rarest naturally occurring element in the universe is stretching the limits of "commercially available" a tad though.
  10. Very few materials we commonly encounter have a structure that is stable under a pressure of 1 GPa. Most, much less. We do not have presses capable of exceeding 100GPa by a huge amount, because we do not have the commercially available materials to construct such presses. Give or take the odd colliding celestial body. And they are a one shot deal.
  11. Sorry, but I don't buy this explanation. Take this example from a previous post: If there was "no heat whatsoever" flowing into your cold sink, that would imply that the thermal efficiency of your machine was 100% (it can't be, but we'll let that pass for now). In other words, you were extracting every last milliJoule of work allowed by the 2nd Law of Thermodynamics. However, if your heat engine did indeed "utilize ALL the heat fed into it" from say 1 kg of hot cocoa, then you would not only have your 100% thermal efficiency, but you would also have attained 100% Carnot eff
  12. You're confusing Carnot efficiency, 1 - TC/TH ... with thermal efficiency, 1 - QC/QH It is entirely consistent with both classical thermodynamic theory, and centuries of detailed empirical observation by the most gifted of experimentalists, for a machine to have a low Carnot efficiency (the fraction of energy in an input stream that is available for conversion to work) and a high thermal efficiency (the fraction of that available work you manage to convert to actual work) The following demonstrates most clearly that you are totally unaware of this distinction: With an in
  13. Please give me a credible mechanism for the creation of a slush (suspension of ice particles in water) in the system I have described. I currently regard the idea as a deus ex machina, but would be delighted to be shown otherwise.
  14. Average low night temperatures on mars are below 200 K throughout the year. There is next to no atmospheric blanketing and the (blackened) pipes are shielded from the ground by mirror finish parabolic troughs. They are in thermal communication with nothing but the empty vacuum of space. You may have noticed that I switched from an initial single 48" ND pipe to multiple 8" ND pipes. This was specifically directed at providing the necessary 'A' in sigma.A.T^4 to meet the night side heat shedding load. You may also have noticed that I've switched to extracting the 18 m^3/s via multiple
  15. ... So... Well you expressed disbelief that the interface pressures could be controlled by the operator. My second to last post sort of covered that, but maybe I could flesh out some details for you. It is relatively easy to set the pressure of a ringmain. A very simple example would be to fit it with an open header tank set at the appropriate elevation and sized to accommodate any expansion/contraction or temporary fluctuations in inventory. Something a little more sophisticated would be called for here. Maybe an underground reservoir with a substantial gas blanket to absorb the flu
  16. Not that interested in ad hominems. Guess we're done.
  17. I'm comfortable with a waterside delta P of ~100 bar (10^7 Pa). Over 10,000 km, this equates to a pressure gradient of 1 kPa/km. This gradient is compatible with a line velocity of 0.15 m/s in 8" double extra strong (XXS) linepipe. This is less than 1% of the flow generated by the freeze thaw cycles making ~ 18 m^3/s available to be tapped off into a high pressure ringmain operating at say 10 bar less than the high pressure (freezing) interface. Similarly, a low pressure ringmain operating at 10 bar above the pressure of the low pressure (thawing) interface will return the
  18. Why would any particular m^3 of ice need to be thawed in 1 second? So long as it's fully thawed by mid afternoon, say, before the heat input has reduced to the point where it starts to refreeze, then it's done its job. 6 hrs to thaw = ~5,000 km of the collection array doing the thawing. Actually, if your figure of 590 W/m^2 is good, a high efficiency collection strip 100 m wide will do the job over ~1,200 km or about an hour and a half. So there's a fair safety margin to play with. PS. Thinking about it, since I'm going to be reinjecting the somewhat warmish low pressure discharge
  19. Why the tone of ridicule? You state that 6 x 10^5 m^2 of collected solar radiation will melt 1 m^3 of ice in one second So 240 x 6 x 10^5 = 1.44 x 10^8 m^2 will melt 240 m^3 of ice per second, the thermal duty we are looking for. My order of magnitude guess of a 100 m strip around the planet seems to meet the requirement several times over. Yes They come as an indivisible pair. The one leads to the other and vice versa. Argument from incredulity? The safety systems could well be a challenge Following a dynamic peturbation (passing dust
  20. Seriously? Non-cowboy operations condition their gas in a proper gas plant with the full demethaniser, deethaniser, depropaniser and debutaniser set to maximise LPG extraction and ensure their sales gas output is fit for purpose. Cowboy operations cherry pick a rough LPG cut with a single stage J-T or turboexpansion stage and more often than not screw up the national sales gas supply grid with intermittent slugs of condensate. Don't confuse typical US practice for global practice. Most of the world falls into the first of these two categories.
  21. It isn't right though is it, Tom. Right would be investing in the appropriate refrigeration system to take out the condensate cut you want in a conventional condenser. Just like the textbooks say. Just sayin'
  22. If that's how you read my posts then, I'm sorry, it was not my intent. Having spent the last 22 years in the West African oilfields, I am unfortunately more familiar with such malpractices than you can possibly imagine. Unless that is you've done time with Shell Petroleum Development Company of Nigeria which would put us on a par. Using a turboexpander as a souped up J-T valve is simply something you should not be broadcasting to the world in my view. At best, people won't have a clue what you're on about, and those who do understand will assume you've worked for Shell Petroleum Develo
  23. This is about as a valid a use case as calling your car a tractor to explain why its upside down in a potato field. Turboexpanders, if they were in the slightest way relevant to your OP which they are not, are NEVER designed for the purpose you describe and to infer that they are serves no purpose other than to mislead the membership of this site.
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