airplane and aviation ?

[standardmoose]

hello all,
was just wondering if anyone has had any experience working on aircraft or more specifically commercial air craft. i was asked a question at a conference the other day about what type of refrigerant is used in aircraft and quite frankly i have no idea. all i can assume is that is wont be hydro carbons or ammonia or co2 other than that i have no idea.

can any one help? anyone got experience or knowledge of what type of refrigerant is used? any help or input would be most appreciated.

cheers
phill

[chemi-cool]

http://www.youtube.com/watch?v=ZmBWiye-Sm4&feature=related

[Robert Hilton]

Seeing as it's -50 to -60 outside and the engines have a ready supply of +120 you will find that the refrigerant used is in fact air. It nothing more than a heat exchanger the most common being compound or bootstrap units.You do find closed cycle airco systems but they are not the norm

[jsimon]

Good answer and a great solutuon
what about when the aircraft is on the run way ?
i have worked on a lorry which had a full air con system built onto the chassis
and massive ducts to plug into the aircraft when on the deck
but these where 20 years ago and i have never seen them in the uk airports
the last 1 i repaired was sent to farnbrough and use to cool the hospitality tents

[Robert Hilton]

Dependant on the a/c. Most don't use a closed cycle system because of the weight penalty. On the ground you just have to sweat it out. I got blown over on Ascension by a pilot because he took a short cut during a taxy run. He found it too hot to stay in the a/c so ignored my marshalling signals.

[phil Landon]

Most commercial aircraft use a mix of bleed air off one of the engines which is then mixed with outside ambient air thru heat exchangers. the air is purified thru filters. there is also another method where the Bleed air is used to power up a cold air unit which is very much like a turbocharger. The bleed air drives the unit and the cooling is done thru the other side of the unit the air is then mixed downstream of the CAU( cold air unit) via electrical valves to get the cabin air to the desired temp there are CO2 sensors that allow the correct air mixture. In the air if an aircraft is above 8000 ft the cabin is pressurised to the equivalent of 8000 ft, the temp is then adjusted to a comfortable level via the mixing valves, the pipework under the floor is quite extensive and a real pain to work on . I have been in aircraft sitting on the ground that have had ice coming from the vents.

Whilst on the ground the pilot can run one engine up and shutdown the other to save fuel and also to run the airconditioning.

Whilst parked a portable cart can be hooked up tho the system to allow cool cabin air but in most circumstances they just leave the doors open until time to taxi. The only place I have seen a Cart hooked up was in Jeddah saudi Arabia where the temp on the tarmac exceeded 50 deg c

Hope this helps a bit

[kevinbick@iol.i]

I was in Cyprus last year and boarded a Thompson Air Airbus coming home. The outside air was about 35 deg C but the cabin air was about 9 deg C. I'm not sure how this was achieved but the reason for it was to sell 'comfort blankets' to those of us wearing shorts 'n t shirts.
I assume the A/C must have been free cos the cabin staff got more abuse than blanket sales.

[Brian_UK]

<snip>I got blown over on Ascension by a pilot because he took a short cut during a taxy run. He found it too hot to stay in the a/c so ignored my marshalling signals.
You need the Brits to handle marshalling properly..... :)
http://www.youtube.com/watch?v=Vz7FI_S0_NE

Sorry :off topic:

[Robert Hilton]

I am a Brit. It was a British a/c (Victor K2). I've never done any marshalling like that.

[nicas]

In addition to what Phil Landon says above which is absolutely correct you should know that every airliner has an extra engine called APU (Auxiliary Power Unit) which can be run independently on ground or in the air which supplies bleed air and electricity for the aircraft.Bleed air goes through the aircraft a/c system where it is cooled by rapid decompression in a turbine so the pilot selects either hot air from the engine bleed or cold from the turbine (air cycle machine) or a mixture of them to have the right temperature.The only case you can see an external APU (EXTERNAL CART) is when the aircraft APU is inoperative or external temperature is so high and the pilot wants to assist rapid cooling of the cabin.

[Jerrylemco]

Actually many GA (general aviation) and other aircraft use a standard a/c system similar to the ones found on automobiles and trucks. The refrigerant in use is generally R-134a (although a couple of customers tried R-22 with disasterous results for their hoses) or in the case of older equipment R-12.

[phil Landon]

would totally agree with jerrylemco, they would be aircraft that have less than 10-15 passengers. The original question was about commercial aircraft which are generally regarded as carrying more than 40-50 people. The size of a closed system that JerryLemco is talking about would be to limiting as weight is a very big consideration in any aircraft.

I understand that many GA aircraft are still prop driven and they can withstand the power drop off from the engines either thru the take off from the gearbox or from being belt driven.

I was trained in the aviation sector (15 years experience) and have been also working as a refrigeration engineer for the last 10.