Economy Refresh

[markis10]

Also if you look up high altitude climbing there are stories where the water would boil at 65 odd degrees but take a long time to get there. Also there is the power output as mentioned above.

I think they are just stories, given most aircraft are pressurised to 10000 ft the water will boil at 92 degrees, it does not get down to 65 degrees even at cruise levels, mind you the water would be ice at 40000 ft given the ambient air temp:

29 in. Hg: 210.3 °F or 99.06 °C (at approx 1000 ft or 305 m above sea level)

28 in. Hg: 208.44 °F or 98.02 °C (at approx 2000 ft or 610 m above sea level)

27 in. Hg: 206.59 °F or 96.99 °C (at approx 3000 ft or 914 m above sea level)

25 in. Hg: 202.89 °F or 94.94 °C (at approx 5000 ft or 1524 m above sea level)

23 in. Hg: 199.19 °F or 92.88 °C (at approx 7000 ft or 2134 m above sea level)

21 in. Hg: 195.48 °F or 90.82 °C (at approx 10,000 ft or 3048 m bove sea level)

19 in. Hg: 191.78 °F or 88.77 °C (at approx 12,000 ft or 3658 m above sea level)

17 in. Hg: 188.07 °F or 86.71 °C (at approx 15,000 ft or 4572 m above sea level)

10 in. Hg: 175.11 °F or 79.51 °C (at approx 27,000 ft or 8230 m above sea level)

5 in. Hg: 165.85 °F or 74.36 °C (at approx 42,000 ft 12,802 m above sea level)

Read more: How does the elevation and air pressure affect the boiling point of water
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[Rebekkap]

You are correct about the boiling point being lower, however the time it takes to boil the water is longer.

I couldn't find the exact wording but this is pretty close:



Boiling - Wikipedia, the free encyclopedia

Also if you look up high altitude climbing there are stories where the water would boil at 65 odd degrees but take a long time to get there. Also there is the power output as mentioned above.

The link you quote is quite correct - cooking takes longer as water is boiling at a lower temperature, and so cooking would logically take longer. It does not, however, say that water takes longer to boil, even though it boils at a lower temperature. Which makes no sense, despite the anecdata you quote from climbers.

Power output being lower definitely explains the toast sitch though.

 

[nlagalle]

I think they are just stories, given most aircraft are pressurised to 10000 ft the water will boil at 92 degrees, it does not get down to 65 degrees even at cruise levels, mind you the water would be ice at 40000 ft given the ambient air temp:

My example was an extreme based on mountain climbing not in an a/c cabin.

 

[markis10]

My example was an extreme based on mountain climbing not in an a/c cabin.

Still a story regardless, its unlikely that a mountain climber would get an air pressure equivalent to the standard pressure at 65000 ft, note those figures are absolute pressure figures, not relative. Water boiling at 65 degrees according to climbers is probably also owing to the impurities in the water, lowering the boiling point.

As for the power being limited on an aircraft, there is plenty to boil water, on a 744 each engine drives an integrated drive generator rated at 90kVA, in addition the APU is also rated at 90kVA, it would be interesting to hear from JB747 what percentage of load is on that system, I doubt its 50% max (assuming all 4 are turning and burning). An A380 by comparison has 4 150kVA gensets, and the 787 even more:

 

[anat0l]

This is drifting off topic - more a science discussion now...


You are right, Rebekkap, that water in the pressurised cabin will boil at 92 degC given a cabin pressure of ~8,000 ft (or ~75 kPa). So in theory it should take less time for the water to reach boiling temperature than on the ground.

In fact, I did some quick calculations and even if you don't stop the boiling process as soon as the water hits the boiling temperature (i.e. some of the water starts to vaporise), then you will still do faster in the air than on the ground.

So my comment was a bit too quick and glib, as in the physics of boiling may itself play little part in how long it takes to make a good cup of coffee.

From re-reading milehighclub's post, the main bottleneck appears to be the machine "warming up". I'd imagine this is necessary since a cold machine and a cold galley environment both make it difficult for the boiling process to occur, wasting much energy and ultimately could ruin the cup of coffee. But now I'm really just guessing.

I did some Googling and found this brochure from a supplier of aircraft galley espresso machines: http://www.aerolux.co.uk/pdfs/s-AL-EX15-200Eiss5.pdf

This is not necessarily the same as the one found on QF aircraft (in fact, perhaps not, since this uses the Nespresso patented capsules), but it purports to have a cycle time of at most 45 seconds to produce a large cup of coffee. It doesn't mention the time required to produce steam, or warm up the unit, however.

 

[rechoboam]

They brought a plunger around in J on Wednesday. I think 85 degrees should be fine for that.

If I designed a plane I would run a bleed line from the pneumatics to an espresso machine. Need to add water vapour and heat?

 

[737]

The main issue with it taking a while to make an espresso coffee is usually the time it take to heat the milk. The steamer (for whatever reason) only produces a certain level of steam which means it takes a while to heat the milk. The milk is generally quite cold as our small fridges work extremely well therefore compounding the problem. The coffee itself does not take long to Brew (once the machine has heated up). It would take no longer usually than a normal coffee machine. However as mentioned it's the time it takes to heat the milk which adds to the time to make a coffee.

 

[Rebekkap]

The main issue with it taking a while to make an espresso coffee is usually the time it take to heat the milk. .

You've got microwaves, right??

 

[mannej]

Milk in espresso... no thanks

 

[Rebekkap]

Milk in espresso... no thanks

That was my first thought too but for those people who like milk... microwave!

 

[pm3207]

Slight O/T, but I saw on another board that there may be Business Class enhancements as well. Any news on these changes?

 

[airbound]

Are hot towels back?

Flying with Qantas | International Economy | Step on board and let us look after you

 

[blackcat20]

Interesting...

on selected international flights, you will be treated to a continuous refreshment service every 60-90 minutes...

Would have been nice on my flight last Friday; myself and the girl seated next to me were begging for snacks as we were both so hungry, and were told "we're out of snacks, everyone has eaten then", yet none ever came down our way. Same for my flight to the US; ended up digging into my own stash of food to keep myself going till breakfast. And the "refresh" bags are a joke; two truffles and a coffee flavoured shortbread.

 

[Rebekkap]

Interesting...

Even more interesting: "All flights will see the introdution of a bodum tea and coffee service..."

NON-INSTANT COFFEE!!!! I'm excited!