at From United States of America, joined Jul 2000, 863 posts, RR: 0 Posted (9 months 3 weeks 5 days 16 hours ago) and read 6059 times:
I was surprised to hear that modern commercial aircraft have ovens, but do not have refrigeration units- instead keeping food and drink cool by a combination of ice, dry ice, and airconditioning.
Just curious why. Surely standard refrigeration equipment is not that expensive, that heavy, or that risky.
Wouldn't a couple of freezer/refrigeration units be useful? Esp for Premium Class meals, where foods often have to be preserved/served at specific temperatures?
type-rated From United States of America, joined Sep 1999, 4343 posts, RR: 21 Reply 1, posted (9 months 3 weeks 5 days 16 hours ago) and read 6014 times:
I think it's because the chilled food items in a bin come onboard in a wheeled container. They just leave it in there until off loading at the final catering station. Saves time having to move the items from the cooled bin to the refrigerator and back to the bin again for off loading.
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tristarsteve From Sweden, joined Nov 2005, 3687 posts, RR: 34 Reply 2, posted (9 months 3 weeks 5 days 15 hours ago) and read 5981 times:
First of all dry ice is very good. A couple of sachets in the top of a food cart will keep it cold for hours.
Secondly thr chillers that cool the cart areas on a lot of aircraft keep the area cold. They will keep a large area at fridge temps. Our A320 have a chiller in the rear galley that holds 6 full size carts at around 5 degC.
All our long haul aircaft have good chillers on them.
And yes real fridges are around. Many years ago we had them on the Gulf Air B737-200s. Amazing complicated affairs that came in pieces, and we seemed to be always evacuating and charging them.
bwaflyer From United Kingdom, joined Jun 2004, 674 posts, RR: 0 Reply 3, posted (9 months 3 weeks 5 days 15 hours ago) and read 5941 times:
bmi fitted fridges on all short haul Airbuses (except one class 144 seat A319s). They take the place of one oven and A320s and A321s have (had) one in the front and one in the back galley. A319s had one in the front galley only. Due to galley reconfigurations and the retirement of short haul A321s, they are slowly disappearing, but if you do find yourself on a short haul A320, as you board you'll see what looks like a metal oven in galley 2 (the forward facing galley in front of 1DEF, and if you look in the back galley, you'll see one of the ovens looks a bit different as it will have a metal rather than a plastic door.
JRadier From Netherlands, joined Sep 2004, 4597 posts, RR: 51 Reply 4, posted (9 months 3 weeks 5 days 13 hours ago) and read 5898 times:
Quoting tristarsteve (Reply 2):
First of all dry ice is very good. A couple of sachets in the top of a food cart will keep it cold for hours.
I have quite the opposite experience. I worked in both the office (dealing with catering) and as crew and dry ice could hardly keep a trolley semi-cool for 1-2 hours, which wasn't enough.
Quoting tristarsteve (Reply 2): Secondly thr chillers that cool the cart areas on a lot of aircraft keep the area cold. They will keep a large area at fridge temps. Our A320 have a chiller in the rear galley that holds 6 full size carts at around 5 degC.
All our long haul aircaft have good chillers on them.
Airchillers are indeed the easiest way to keep trolley contents cool, and it in no way impedes the cabin crew in their work (apart from the galley getting a bit colder).
For once you have tasted flight you will walk the earth with your eyes turned skywards, for there you have been and ther
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 81 Reply 5, posted (9 months 3 weeks 5 days 12 hours ago) and read 5846 times:
Quoting at (Thread starter): I was surprised to hear that modern commercial aircraft have ovens, but do not have refrigeration units- instead keeping food and drink cool by a combination of ice, dry ice, and airconditioning.
There is no functional difference between a galley chiller and a refrigerator. Just think of the chiller as the mechanical side of the refrigerator and the galley cart + enclosure as the box. Both systems are just heat pumps moving heat from the air inside the box to the outside.
Having run into a cross-wired galley chiller once, they're more than capable of being pretty good freezers too.
KELPkid From United States of America, joined Nov 2005, 5929 posts, RR: 4 Reply 6, posted (9 months 3 weeks 4 days 18 hours ago) and read 5359 times:
Quoting tristarsteve (Reply 2): And yes real fridges are around. Many years ago we had them on the Gulf Air B737-200s. Amazing complicated affairs that came in pieces, and we seemed to be always evacuating and charging them.
Not suprised. A conventional refrigerator (like one in a house or an RV) is very sensitive to how level it sits. Placing it on a slight incline is asking for a reduced lifespan (which usually manifests itself in the form of a refrigerant leak!). Most RVs (campers, motorohomes, travel trailers, etc.) are designed to be easily leveled at a campsite or parking area for this reason.
As you and I know, when an aircraft flies, it spends a fair amount of time in a less than level attitude...
Celebrating the birth of KELPkidJR on August 5, 2009 :-)
faro From Egypt, joined Aug 2007, 1443 posts, RR: 0 Reply 7, posted (9 months 3 weeks 4 days 17 hours ago) and read 5314 times:
Conceivably, one could design a fridge that uses the fuselage skin (in cruise) as coolant although you would need a pretty funky regulation mechanism; has this ever been implemented/attempted?
LMP737 From , joined Dec 1969, posts, RR: Reply 8, posted (9 months 3 weeks 4 days 11 hours ago) and read 5155 times:
Quoting faro (Reply 7): Conceivably, one could design a fridge that uses the fuselage skin (in cruise) as coolant although you would need a pretty funky regulation mechanism; has this ever been implemented/attempted?
The engineering involved probably would not be worth the cost.
Quoting JRadier (Reply 4): Airchillers are indeed the easiest way to keep trolley contents cool, and it in no way impedes the cabin crew in their work (apart from the galley getting a bit colder).
Just not the extactly the funnest thing to change once they go bad. Especially the one mounted above the O2 bottle in the E/E bay of the 767.
tdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 81 Reply 9, posted (9 months 3 weeks 4 days 11 hours ago) and read 5146 times:
Quoting faro (Reply 7): Conceivably, one could design a fridge that uses the fuselage skin (in cruise) as coolant although you would need a pretty funky regulation mechanism; has this ever been implemented/attempted?
The concept exists as a skin heat sink, occasionally used in ECS systems.
Conventional chillers reject their heat into the crown area, where the heat is dumped to atmosphere via a combination of crown ventilation and skin conduction. The newer systems use liquid cooling at the galley and a liquid-to-air heat exchanger in the ECS system. However, at the end of the day, they're all using the outside air as their heat sink.
You can't use ambient air as your primary cooling source though; the critical case for the galley cooling system is hot day on the ramp, exactly the time when you don't have cool outside air. The chillers don't have to work hard at all during cruise; it's that August day in Arizona that screws you.
jetjack74 From United States of America, joined Jul 2003, 7335 posts, RR: 52 Reply 10, posted (9 months 3 weeks 4 days 10 hours ago) and read 5127 times:
At DL, our A330s have enclosed chillers with doors on them to retain the cold air which are constant forced air while our 767/777 have chillers where the cooling vents open when a cart is inserted into it's galley position. We can turn them off and when we want to.
The PMDL 757/767 aircraft has a chiller/freezer cabinet in the 1st/BE galleys
The 777 aircraft have chiller/freezer cabinets in all galleys.
rfields5421 From United States of America, joined Jul 2007, 6140 posts, RR: 25 Reply 12, posted (9 months 3 weeks 3 days 11 hours ago) and read 4823 times:
Quoting KELPkid (Reply 6): . A conventional refrigerator (like one in a house or an RV) is very sensitive to how level it sits. Placing it on a slight incline is asking for a reduced lifespan (which usually manifests itself in the form of a refrigerant leak!).
While some high end RVs have commercial household refrigerators - most RVs have a dual gas/electric Absorption Refrigerator which has no compressor or fan or similar moving parts. My camping trailer has a 6 cu ft Dometic.
Yes, they are sensitive to being level - needing to be within 5 degrees of level to operate properly. (Most picky RV leveling in my experience of years of camping with RVs is that people are very sensitive to sleeping on a slope. They don't like it. Or like with mine - the water won't drain properly from the sink, basin or shower if the RV is not almost level.)
They would operate well on aircraft, but no one wants a fridge on an airplane which depends on a flame, or electric heating element to heat the solution, and having pure ammonia as a potential leak. RV fridges have all the operating components vented to the outside so that if a leak develops it won't kill everyone in the RV..
The biggest problem in my mind about having a household type Vapor-Compression Refrigerator on an aircraft is the noise of the compressor and fan, and how to dissipate the waste heat they generate. The cooling coils at the back of a normal household Vapor-Compression Refrigerator is quite hot.
LMP737 From , joined Dec 1969, posts, RR: Reply 14, posted (9 months 3 weeks 2 days 19 hours ago) and read 4598 times:
Quoting tdscanuck (Reply 9): You can't use ambient air as your primary cooling source though; the critical case for the galley cooling system is hot day on the ramp, exactly the time when you don't have cool outside air. The chillers don't have to work hard at all during cruise; it's that August day in Arizona that screws you.
What drives me crazy is when someone leaves them on when they are not needed.
Tod From Denmark, joined Aug 2004, 1682 posts, RR: 3 Reply 16, posted (9 months 2 weeks 22 hours ago) and read 3426 times:
Quoting tdscanuck (Reply 9): Conventional chillers reject their heat into the crown area, where the heat is dumped to atmosphere via a combination of crown ventilation and skin conduction.
Some use the crown, others dump the warm condenser exhaust air below the floor where it eventually finds its way to the outflow valve.
744 do both. Door 1 and door 2 galley complexes exhaust under the floor outside the right side of forward cargo compartment via a large boost fan. The upper deck and door 4 galleys dump into the crown.
Quoting tdscanuck (Reply 9): You can't use ambient air as your primary cooling source though;
The evaporator airflow is typically a closed loop out of the chiller into the chilled portion of the galley and back to the chiller. The condenser side typically draws ambient air right at the chiller location or from under the cabin floor.
Quoting tdscanuck (Reply 9): The chillers don't have to work hard at all during cruise; it's that August day in Arizona that screws you.
Chiller testing in Hong Kong last Saturday was fun too.
bikerthai From United States of America, joined Apr 2010, 1588 posts, RR: 4 Reply 17, posted (9 months 2 weeks 18 hours ago) and read 3365 times:
Quoting faro (Reply 7): Conceivably, one could design a fridge that uses the fuselage skin (in cruise) as coolant although you would need a pretty funky regulation mechanism; has this ever been implemented/attempted?
Skin heat exchange is used on Military aircraft to provide cooling air for the electronic equipment (AWACS etc). But as Tom said, they are useless on a hot tarmac, so cart air becomes the primary source of cooling air to cool equipment and chillers (via the ECS system) when on the ground.
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