Enthalpy

Senior Members
  • Content count

    3199
  • Joined

  • Last visited

Community Reputation

220 Beacon of Hope

2 Followers

About Enthalpy

  • Rank
    Scientist
  1. Multi-Fibre Laser

    Oops : e-6~1/400 coupling by the evanescent wave through 120µm coolant needs transverse j50krad/m that demand 1.45-1.449 96 difference between the refractive indices, impossible to stabilize. ========== Cooling figures The following figures aren't optimum nor well chosen. They shall only shaw that some set of parameters looks feasible. I use data from the silica family, but fibre lasers prefer aluminosilicates. Gaseous nitrogen seems easy, but I compute with gaseous hydrogen. Colour centres can work under the synchronization sections too, as the overtemperature is small. This eases the manufacture. I compute with an even distribution through the core's depth, but concentrating them near the cladding as depicted would even the core's temperature hence light intensity and is made by just one deposition step more. The sync sections can share the cladding's material. Or maybe use the core's material, but then phase shifts happen. I suppose the fibre can receive the thicker cladding everywhere and be etched thinner outside the sync sections. A smooth surface matters: heat again? Sources don't tell it, but I guess some lossy material is needed around the cladding to force the single mode. Here it needs an intermediate low-index material in between. The low-index and lossy materials must be absent from the sync sections. Remove them mechanically? That's easier if they are organic. Or deposit them after the sync sections are assembled? I hope the sync sections can be sintered together, or maybe glued. Electric sealing would need Na+ ions to my knowledge. Gaseous hydrogen at 300K 300bar has compressibility Z=1.19, 10110mol/m3, 20.4kg/m3, capacity 28.8J/mol/K 14290J/kg/K 291kJ/m3/K, viscosity 9.7µPa*s and 0.48mm2/s. 420 fibres, 2m long, shall deliver 420*140=58,8kW light and produce 420*70=29,4kW heat. The sides of a hexagonal pattern are 8+1 fibres wide (err, no, it's more), or 1.6mm. 54dm3/s hydrogen exit 2K warmer, so silica fibres whose index drifts by 8.7*10-6/K propagate 1300nm light over 700µm with +-2.5° discrepancy to be evened out by the sync sections. Hydrogen flows at 5.6m/s at the 3*2m*1.6mm ports and some 13m/s between the fibers. If the fibres didn't interact, then Reynolds ~1600 makes the flow transitional and Cd=1.0. Tripling the drag without reason to account interactions, the flow pushes 0.14N/m on the fibres. Stiff supports with 700µm period leave 5.5nN*m bending moment, so R=70µm and E=90GPa give 0.4nm deformation and 20kPa stress. The experimental 0.32 gauge factor over the volume changes the refractive index by <70ppb only. 1.4W/m/K silica conduction from r=0 to R=50µm and uniform 35W/m per fibre make the centre 2.0K warmer than the interface, so the index 17*10-6 bigger amplifies the field by <2.0 over the outer 20µm radius. The algebraic solution would be better, and colour centres only near the interface would give uniform temperature and field. From r=50µm to R=70µm, the temperature drops by 1.3K, the index by 12*10-6 and the field by <1.4 more than what both materials do. The coolant resides some 8µs around each fibre so heat diffuses only 3µm deep, and turbulence shouldn't reduce that further. This coolant layer warms by mean 3K and this won't differ much among the fibres. Arbitrary exp(6)~400 field attenuation over 2*40µm thick sync sections needs a transverse wave number j75krad/m. Indices of 1.45 et 1.450 080 achieve that, needing for instance 0.05mol% GeO2 doping at the core, and possibly some compensation of the colour centres. Marc Schaefer, aka Enthalpy
  2. Iceberg to Capetown

    The thermal conductivity of dry sand is rather 0.25W/m/K, so over 300 days, 1m thick sand would let melt only 3% of the the 1000m long, 190m base, 90m high ice dump suggested on September 30, 2018. Sorting the sand to keep only one grain size may reduce the thermal conductivity. ========== Some places like the North American Great Lakes region have icy winters, hot summers and a rich big population. Insulated dumps can keep ice from winter to summer to sell for the already described air conditioning. One source of ice could be the lakes themselves. Distribution of the ice is again a significant cost contribution. Suburbs, near to the ice dump and where trucks circulate better, ease that. The many short rotations enable electric trucks easily. Swap the batteries if necessary to save time. Marc Schaefer, aka Enthalpy
  3. Multi-Fibre Laser

    This illustrates coolant flowing transversally among the fibres: With two "poles" (similarly to an electric machine) and pumping illumination from the sides, or six coolant poles and pumping unspecified. Notice the lack of fibres at the centre where the coolant stagnates. A powerful laser needs much coolant throughput, transverse flow eases that. ========== An evanescent wave through the coolant may be possible but is not easy. Imagine the evanescent wave at vacuum 1330nm shall decrease by exp(6)~400 over transverse 120µm in the coolant. That needs transverse k=j314krad/m in the coolant. Propagating in silica at k=6.850Mrad/m from N=1.450, it needs 6.843Mrad/m in the coolant, or N=1.448. Coolants with a matching index exist (N=1.449 for CCL4, mix it) and some will be transparent enough, but the index drifts with temperature in silica and in liquids. The close match must be kept despite heating. Surrounding a fibre core with a material of similar composition, like a bit of fluorosilicates added to silica, keeps more naturally the tiny index difference over temperature. Marc Schaefer, aka Enthalpy
  4. Multi-Fibre Laser

    A first pumping scheme uses one fibre laser to pump each fibre of the multifibre laser. The pumping light arrives in the narrow multiple lasing fibres, with single cladding or no cladding. Coupling by the evanescent wave is easier, and cooling the multifibre laser has no additional constraint by the pump. Fibre lasers are already common. Just build many independent ones and cool them. The multifibre laser receives pumping light, for instance at 1µm, that is not coherent from one fibre to the other, and makes light, for instance at 1.3µm, that is coherent across the fibres and can be well focussed. A good power efficiency for this step resembles the wavelength ratio. The pumping fibre lasers had already converted light from laser diodes which themselves received electric power. Two pumping lasers per fibre, one per side, make sense too. Splitting or merging the pumping light is also possible if somehow advantageous. Marc Schaefer, aka Enthalpy Thanks Swansont! Source?
  5. Multi-Fibre Laser

    Hello everyone and everybody! Fibre lasers produce a high quality beam up to very few kW output and with excellent power efficiency. Nice to cut steel sheets for instance. But 2kW in D=100µm and er=2 make already 7MV/m, and the material's breakdown doesn't allow much more. To obtain more power from several fibres and keep the phase coherence among them, I propose to synchronize the phase by evanescent waves. With a cladding thinner than usual, fibres side-by-side share some light, and if done often enough while the laser light is produced, I hope the bundle emits coherent light. This shall be easier than a single oscillator driving independent lasers amplifiers before merging the beams, which needs difficult precautions to limit the phase drift over the long amplifiers. The fibres alternate a certain number of amplifying sections, with colour centres and dissipation, and synchronizing sections where the evanescent wave drops slowly enough to couple the fibres. Short distances between synchronization avoid excessive phase discrepancy. If the coolant has low optical losses and an index close to the fibres' one, it too can couple the fibres by evanescent wave. Then the synchronization sections can become mere space holders. Cladding at the amplifying sections reduces the light amplitude in the coolant and at the interface, if this is necessary against losses. If the synchronization sections or space holders are very short, dissipation there can become acceptable, and the fibres can contain colour centres there too. Pumping light can arrive from any end, or both, or from the sides. The coolant too can flow axially, though radial flow makes a greater flux or a lower speed, especially with four poles or more as in electric machines. Thin fibres are easily cooled. The multifibre laser can oscillate or amplify. The pilot light might sometimes be fed in a single fibre, but I expect it will be spread most often. Mirrors at none, one or both ends are commonly Bragg gratings, more easily because synchronization is done elsewhere. The multifibre laser needs not be straight, as long as the fibre lengths are identical enough. It can build a ring for instance, optionally with several turns. I believe to have described this already on the Net. I someone knows where, please tell! Marc Schaefer, aka Enthalpy
  6. Quick Electric Machines

    No hard limit. It's a matter of diameter, of an angular speed convenient for the other items on the shaft, and of optimization rather than clear barriers. Magnetic materials can operate at kHz, MHz, even GHz (though less useful at many GHz). But over few kHz, the good materials use to be brittle, which I'd dislike at an aeroplane. One can misuse iron laminations at higher frequencies, but at some point the higher frequency becomes a drawback then, not an advantage. Power electronics can still switch efficiently at 100kHz for instance, but in the MW or GW domain, lower frequencies are better. Then you want to switch must faster than the produced waveform that powers the machine, which puts a strong limit. My waveforms are a new solution to this https://www.scienceforums.net/topic/110665-quasi-sine-generator/?do=findComment&comment=1041409 Electric machines improve with the peripheral speed, which is limited by feasibility (in a dam), centrifugal force, and possibly the speed of sound and aerodynamic losses. Presently, a sleeve of hardened steel circles the fastest rotors. I proposed to wind graphite+matrix filaments instead. 50-100m/s is common in 1GW turbogenerators, 200m/s is reasonable with permanent magnets, while variable reluctance can be much faster. A small centrifuge can rotate much faster than 400Hz, but a D=1.3m turbogenerator rotor at 100m/s only achieves 25Hz.
  7. Motional EMF

    With a brush, a machine can work. That' a typical homopolar machine. But you show a measuring loop on the photo, completely static and without any sliding contact. This can't produce a DC voltage.
  8. Storing Renewable Energy

    Fraunhofer's storage spheres pump water out of pressure-resisting constructions. They need some material (typically concrete) to keep the vacuum. A seducing aspect of the underwater bags is that, to store compressed air at depth, the bladders resist no pressure at all. So to say, the Ocean's pressure keeps the air under pressure in the bag. Though, underwater bags need some weight to stay in the depth. Unless the installer finds heavy rocks or sand at the seabed, he'll have to bring concrete, and in significant amounts too. One other aspect is that water is easier to pump and turbine with decent efficiency than air to a high pressure ratio, and better, storage in the spheres can transport just electricity to and from the depth. ========== Build extra production capacity: sure. When storage is obviously too expensive, this is a part of the solution. Wind electricity is already cheaper than nuclear one and is continues to get cheaper, so more wind turbines are affordable. The other part of the solution is to transport electricity. Between Scotland, Greece and Romania, the distance covers one depression width, so we won't lack wind at all locations simultaneously. Even from Scotland to Galicia, we won't have under 5 Beaufort at all locations for more than one day.
  9. How is energy stored in a field?

    And where is the second body when the electron and positron have already disappeared by annihilation, two gamma rays propagated, and one electron detects a gamma ray? Or if you prefer fields with many photons, send a radio wave to the Moon for reflection there, receive it back on Earth two seconds later. In the meantime, you can wrap the emitting antenna in aluminium foil, destroy it somehow, whatever you like. You don't need the emitting item. The receiving item is sensitive to the field that existed after the emitter was made inoperable. Similarly, the receiving antenna can be extracted from an aluminium foil just prior to receiving the wave. If light comes from a remote galaxy, our detector didn't even exist when the light was emitted, and the light source may be a black hole when we detect the light. In such situations, if you want to keep the laws of energy conservation, momentum conservation, you have to accept that fields exist at times when the items that create or sense them are absent. There is more. As light passes by a massive object and gets deflected, light also pulls the massive object, even by that little bit. This is necessary if momentum conservation works. It happens possibly at a time where both the emitter and the detector are inexistent, and at a time when photons are not created nor destroyed. Cumulating all this, one has to admit that propagating fields have an existence independently of the items that create or sense them.
  10. Iceberg to Capetown

    Please see my second answer there https://www.scienceforums.net/topic/116226-iceberg-to-capetown/?do=findComment&comment=1071764 I suppose professionals know better answers. Please see my fourth answer there https://www.scienceforums.net/topic/116226-iceberg-to-capetown/?do=findComment&comment=1071764 I consider closing the bottom when arrived. Moving a sac of water in water can be cumbersome. But presently, I prefer to lose the molten water, mine the ice once arrived and transport it solid to the land. Whether storage shall be liquid or solid depends on the use. Bladders have been considered to transport sweetwater over the Ocean. Whether the source is an iceberg shouldn't change much, since melting is harder to prevent than to encourage. You have a whole Ocean full of heat for that. I have doubts about solar energy at 40°, 50°, 60° South. Wind should be more dependable there. Autonomous: I have absolutely nothing against. That's more interesting for smaller transport units. If downsizing to 300 000 t makes economic sense, maybe a hull can replace the bladder, and then movement becomes more natural, including with sails. I have no investors nor plan to earn money with that. That's a reason why I put it on the Web. Feel free to become a billionaire with the idea. Don't forget in your business plan the few technical subdetails to be solved.
  11. Iceberg to Capetown

    1200kg Ice storage to cool a detached house for a week can look like this: The ice stays in the storage. Air from the house or filtered from the atmosphere or passes through a heat exchanger at the tank's bottom. Regulators in the rooms suck as much cold air as needed locally, they blow and mix it as needed, and the ice melts accordingly. 0.2m foam plus the metal at the top opening leak 43W or 62kg=5% in a week. Flowing the arriving air first around the insulation would reclaim the leaked cold, an opportunity for thinner cheaper foam. The heat exchanger needs roughly 10m2 fins of banal alloy. To clean the exchanger, the foam around it is removable. 2mm steel weigh around 400kg so series production may cost a bit over 1k€ a piece. Some sort of key and measure of the delivered quantity, shared by the supplier and the user, seem necessary. The meltwater can be useful in many gardens. ========== If the ice comprises blocks of very different sizes, more can pack in a tank, just like concrete comprises stones, pebbles and sand. Easily done when mining the iceberg. Delivery trucks, reasonably manoeuvrable, can carry around 25t ice, so they should make a rotation for <<133€, easier than the previous estimate. If a truck makes 6 rotations a day, 20 days a month, it looks feasible, but remains a significant cost share. Marc Schaefer, aka Enthalpy
  12. Quick Electric Machines

    I described here on Apr 08, 2013 an APU that tells how smaller a motor is if it rotates fast http://www.scienceforums.net/topic/73798-quick-electric-machines/?do=findComment&comment=737931 1270kW machine too, but estimated 16kg for 813Hz instead of 224kg for 20Hz. The two-stage gear needs maintenance and weighs a bit too. An intermediate solution, with a single-stage gear and a medium diameter motor, may be considered too. Planetary (epicyclic) gears are compact and powerful at small electric motors. Would they be good for electric aeroplanes? wikipedia
  13. Quick Electric Machines

    Here's an example of gearless ring motor for the described Dornier 328: 1400kW at 20Hz. 10mm thick Neorec53b magnets (Nd-Fe-B from Tdk) at the D=0.84m rotor move with 52.8m/s and provide 1.16T at +60°C in 2mm gap, of which prestressed graphite composite wound filaments occupy 1mm to hold the magnets. The L=0.16m rotor and 3-phase stator have 24 pole pairs (though differing numbers would cog less). The conductors pass once per pole through an own slot, so the peak voltage is 468V. The magnets are 80% as wide as the poles, so the waveform provides a fundamental amplitude of 1.21*468Vpk. No fractional pitch here, but the slot skew is +-1/7 the pole width, multiplying by 0.967 the fundamental si H1=548Vpk=388Veff and 1400kW take 1203Aeff=1701Apk per phase. The inverter needs inconvenient 1100VDC (if no H3). Multi-turn coils in parallel are more usual and may enable <500VDC, but then only a very symmetric machine avoids stray currents. Fractional pitch would bring known advantages and stay <3000VDC. The bars superimpose 48 flat enamelled e=0.5mm W=6mm conductors that may be lasercut or etched from much bigger sheets for easier turns. I hope to introduce them sequentially in the slots. Estimated with optimism at 0.25m per bar, they show 1.35mohm per phase and lose 5.9kW in total. The 480Hz azimuthal induction in the slots is 0.31Tpk near the teeth, so the eddy currents in the conductors lose 1.4kW in total. I didn't evaluate the radial induction component. The stamped 4mil lamination are of Supermendur (Fe-Co from MKMagnetics) used at 1.87Tpk. This enables three 7mm wide slots per 55mm pole. They lose 40W/kg at 480Hz, or 2.7kW between the slots and 2.2kW outside. All these losses, 12.2kW=0.87%*1400kW, can be conducted away by the bars within 22K if some grease makes the contact with the laminations. Outside the slots, the conductors are spread to cool by ventilation, and they rotate one position in the slot between two slots, as a simpler form or "Litz" (=braided) wire. The stator currents superimpose 94mT at the gap, needing additional 45Vpk in quadrature per phase. The laminations don't saturate. The induction through the slots need additional 71Vpk in quadrature per phase. The machine could be shorter, thicker, lighter. Fractional pitch would ease here. Here are masses in radius order: 54kg Fe-Co external 34kg Cu 68kg Fe-Co between slots 1kg Graphite 25kg Magnets 42kg Steel ------ 224kg Sum The shaft, rings, bearings, casing, fans are not included. More poles would enlighten the motor. Marc Schaefer, aka Enthalpy
  14. Iceberg to Capetown

    Ice has more value in air conditioners than molten at a tap. It might also supply +5°C to fridges, but uneasily -10°C to freezers. The former iceberg is too big for that use, and the main cost is to cross the last km to the customer, not the Southern Ocean. de.wikipedia metric, en.wikipedia exotic Every 1000kg=1.09m3 provides 334MJ cold at 0°C, and I neglect the cold liquid's 30MJ. To provide the same, a 350% efficient air conditioner would consume 26kWh costing 5.3€ at 0.2€/kWh. A 40% efficient generator would consume 5.4kg fuel to make the 26kWh - compare with 0.12kg fuel per ton to transport the iceberg from the South. The previous iceberg arriving with 60 000 000 t would be worth 318M€ electricity at retail price and make routine transport very profitable, but it's slightly too big. A rich hot city with 1M inhabitants may have 300 000 buildings with air conditioners that provide each mean 2kWth for 8h a day, 150 days a year: the city consumes 2.6PJth/year. 7 800 000 t ice suffice and save 41M€ electricity. That's an 80m thick, 400m long and 270m wide berg yearly. Bringing net cold to a hot city is more rasonable than dumping net heat to cool the buildings. Over 40km2 at mean 250W/m2, the city receives 130PJth from the Sun over the 150 days. 2K difference? I suppose that a floating bucket wheel can exploit the iceberg anchored at the cost and coveyor belts bring the ice blocks to land storage. Unclear to me. This hardware can serve for several cities and years. Storage would be on the ground, within 2m sand between geotextiles: 1000m long, 90m high, 190m base expose 0.45km2. <1W/m/K and 25K leak <5.6MW. Over 150 days, 220 000 t melt, or 3%. This would apply also if using the iceberg as sweetwater. Every day, a house with air conditioners using mean 2kWth needs 58MJth from 173kg ice. Storage for a week means 1200kg that occupy <3m3 and are only 6.4€ worth of electricity. Carrying 14.4t in the city, a truck should make a rotation for <<77€, not easy. The storage must be accessible from the truck, not by foot over a lift. A D=1.5m H=1.7m tank insulated by 0.2m foam leaks 43W, that's 78kg lost in a week, or 7%. Bigger buildings don't ease much, since trucks have a limited size. A heat exhanger at the tank and few air pipes and fans replace the expensive air conditioner. Marc Schaefer, aka Enthalpy ========== Hi everybody, nice to see that the topic catches the imagination!
  15. Woodwind Materials

    I proposed on Nov 13, 2017 that the wall material can influence the sound by an elliptic vibration around the tone holes http://www.scienceforums.net/topic/111316-woodwind-materials/?do=findComment&comment=1023070 and the effect of the toneholes' nature is consistent with my explanation. As explained by Miyazawa and many more, the toneholes of a flute as of some saxophones can be drawn from the body of soldered on it http://www.miyazawa.com/media-library/educational-articles/options/drawn-vs.-soldered-toneholes/ Drawing the toneholes from the body makes them even thinner, while soldered ones are thicker. The toneholes are the very item that stiffen the instrument against elliptic vibrations there, and the effect of soldered toneholes is said to resemble a thicker body: stronger darker sound. I won't be more positive than "consistent with my explanation", because: I never compared by myself the two hole constructions. So many sales arguments aren't justified! This feature is never an option within a flute series. It characterizes series that have more differences. Soldered tone holes are typically undercut, so the transition from the bore has a bigger and better controlled radius. This knowingly matters. The rim shape may differ. The flow gets easily nonlinear there, and angles would change the sound. I suggested to electroform complete flute joints, the body with the tone holes at once. With denser current or more time, including insulating masks, electroforming can produce locally thicker metal, for instance at and near the tone holes. Marc Schaefer, aka Enthalpy