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easyJet To Run Dry For Efficiency
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I wonder what crews might make of this? I can imagine the idea would be offset by the gallons of water people would be taking on board for hydration. Over the next 12 months, UK carrier easyJet plans to find out if they can improve the efficiency of their operations by removing moisture weight from their aircraft, the airline announced Wednesday. The carrier's yearlong test involves installation of 66-pound "Zonal Dryer" systems in four Airbus A320 aircraft. It is hoped that the system, provided by CTT Systems of Sweden, will remove up to 550 pounds of moisture per flight from the jets. The carrier says the weight is equivalent to removing 12 bags from the cargo hold and that could save nearly 10 million pounds of fuel, per year. The company also claims passengers will see a benefit. According to easyJet, the move is in keeping with their efforts to be "as environmentally responsible as possible" and "using the latest technology to minimize the fleet's environmental impact." If the dryers work, the airline expects they could shave down the roughly $2.35 billion it spends on fuel each year while also "improving air quality for the passenger." The system works by using a fan, heater and moisture-absorbing silica-impregnated rotors to reduce water retention and channel dry air to particular parts of the aircraft to inhibit water retention. According to easyJet flight operations manager, Captain Chris Foster, "We're confident that we'll see significant and positive results on completion of the trial." |
Aren't some airliners (A380, 787) being marketed as maintaining cabin humidity closer to that at sea level so as to make them more comfortable? |
If you take the trouble to read up on the system, you will see that the moisture is removed from the zone between the cabin and the aircraft skin.... and moister air can be directed into the cabin air system.
Sounds like a win-win to me. |
I'd love to see the weight / fuel burn calculation for that one :}
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I don't understand how they will actually remove the humidity from the aircraft in order to actually reduce weight while in flight? Silica gel only sequesters the water vapor, the weight is still there until you replace the adsorbing material. Do they actually plan on jettisoning it en-route? :eek:
I can understand the "increasing comfort" part (by actually making cabin air moister and hence more comfortable for humans) but the fuel saving part sounds like total PR bull to me, and I'm not even considering the power requirements of these gadgets. Guess what that power will inevitably be generated with?? |
N2 versus H2O
For a given volume, isn't the mass of humid air less than the mass of dry air? After all, air is mostly N2 which as a molecule is certainly heavier than H2O. So....removing the gaseous water vapour from the cabin and expelling it outside the aircraft somehow will actually make the aircraft heavier, assuming the pressurization system maintains the same pressure
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If memory serves, air around the skin of the aircraft is passed over a rotating 'wheel' of silica gel. The section now containing moisture is rotated around into a warmed cabin air stream which dries out the silica (continual process). The result is drying out insulation etc reducing weight, but also transferring that moisture to the cabin air.
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I've read up on it and found out that the system actually should prevent condensation forming inside the plane. The weight quoted is probably the average amount of condensation water in liquid form carried around in a plane.
I still don't understand how trapping it into silica gel will get rid of the weight though, unless the material is actually jettisoned in flight. := I also haven't found any hard data on how much power the units will require, power that will ultimately have to come from the fuel and will have to be offset against any actual fuel saving. |
The result is drying out insulation etc reducing weight, but also transferring that moisture to the cabin air. Edit to add: and the units themselves have to be flown around, as pointed out by catttletruck. |
Dg800 <<I still don't understand how trapping it into silica gel will get rid of the weight though, unless the material is actually jettisoned in flight.>>
Because it is only temporary, until that silica gel is rotated into a flow of heated cabin air, which will dry out silica gel, the water vapour therefore will be introduced back to the cabin, and the freshly dried silica will be ready to absorb more moisture. This will cause much lighter insulation, less ice on aircraft skin interior etc. edit replied before previous post showed. Ice does weigh a lot, so does soggy or iced up insulation. Water in gas form doesn't weigh much at all, infact less than dry air. |
Because it is only temporary |
haha indeed
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If they saying that there is half a ton of condensation in the linings etc then I'd love to know if it features in the aircraft's weight schedule? Dry operating weight (he he) is factory derived and won't account for gash atmospheric weight picked up in service. Half a ton is getting towards significant on a 60t aeroplane.
They'd find it on a re-weigh, but until then are we carrying half a ton of unaccounted for moisture? Wouldn't it be easier just to carry a member of the management on each flight so all the hot air drives the moisture out? |
Many years ago the insulation was removed from a 767 during maintenance and when it was reweighed well over half a ton of moisture had been removed. That's a lot of fuel burn over a year.
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Many years ago the insulation was removed from a 767 during maintenance and when it was reweighed well over half a ton of moisture had been removed. A better solution than installing moisture extraction fans would have been to using insulating material that does not absorb or is impervious to condensation in the first place. |
Dry, high altitude, atmospheric air enters engine, is compressed, passed through packs to cool and regulate the pressure and then passed into the cabin.
Passengers breath in dry air, and breath out humid air (that's why you need to drink more while flying - you are expiring moisture and need to replace it). That moist air eventually moves towards the outflow valve at the rear of the aircraft - but on the way it rubs against the cold aircraft skin, the moisture condenses and either freezes as ice or soaks the insulation. A better solution than installing moisture extraction fans would have been to using insulating material that does not absorb or is impervious to condensation in the first place. This system dries the air before it gets to the cold section and returns some of the water to the cabin air and exhausts the rest of the water overboard. |
Thanks CB, I understand the principles involved and my train of though is coming around to liking this idea.
My point on the insulation was why do they use a material (sponge/fibre) placed against the aircraft skin whose insulating thickness also contains a large proportion of cabin air. Could they not use a different kind of static insulation next to the cold skin that doesn't have room for the cabin air so as not to form any condensation in the first place. |
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