How do normal passenger planes such as a Boeing 757 200 not overheat while travelling what cooling system is used ?

Other answer:

Commercial jet engines don't have a cooling system like a car. There are a couple factors that work together to ensure the engines don't overheat:

1. The engines are designed for high temperatures. They are made primarily of Nickel based alloys which can withstand temperatures of over 2,000+ degrees F. (someone mentioned titanium – that is not correct. Titanium would melt in a jet engine. Its used for lots of other parts on the airplane because its light and saves weight compared with aluminum or steel, but not in the hot portions of engines).

2. On a car engine you have a giant chunk of steel (the engine block) surrounding the pistons where the combustion occurs. That means that the engine block absorbs tons of heat energy and you need cooling systems to prevent too much heat energy from being absorbed.

But on a jet engine the combustion works more like a torch which is positioned to force the turbine to spin. That means that most of the heat created by the combustion is retained in the combustion gasses and not the metallic components. This air (exhaust) is then blasted out the back of the engine very quickly, which means that most of the heat created in the engine is blown out to the atmosphere before it has a chance to transfer any of that energy to the engine components.

3. As other people have mentioned the engine blows a LOT of air through itself by design, and that air is freezing cold while in flight. Temperatures of 30 to 100 degrees below zero are common and can go even lower.

A few things are happening in the engine in order to keep it cool.

1.) Bypass air is used around the engine to draw heat away from the engine and keep the outer components cool.

2.) Within the combustion chamber there's some cool things going on. Yes the material is made of a strong heat resistant alloy, however, if the burning gasses were allowed to touch them they would melt. Inside the combustion section are burner cans that mix the fuel and air to maintain combustion, essentially it looks like a blow torch. Inside this can, there is air being directed in a very specific manner to focus the burn and keep it physically separated from the walls of the can. By physically directing the burning gas into a narrower area components can contain something burning at a higher temperature than their melting point.

3.) Oil. In turbine engines specifically: Yes the oil is used for lubrication, however its second feature is its cooling properties. The oil has to be sprayed onto or flow near components reaching up to 1500 degrees, it must then absorb that heat and draw it away from the part. From there it is brought through a heat exchanger located in an area it can receive ram air flow. (Alternatively some engines use fuel as the cooling medium) The oil flows into the exchanger, through small channels resembling a cars radiator, where heat (which flows from hot to cold) is drawn out and into the passing air.

Engine bleed air is used for power source for ACM air conditioning units of airliners –
Operation of the ACM or engine bleed air has no effect on operation of engines –
Just a few degrees extra on the engine EGT…

Some smaller jets use freon air conditioning packs – cools better than air cycle packs .
That is the case of business jets – Similar to a car freon air conditioning system –
Freon air conditioning units use electrical power for comptrssors – not bleed air –

Some early 707's had a freon packs option – Many airlines in USA made that choice –
Just bigger electrical generators we required – 40 KVA rather than 30 KVA –

If a problem occurs with the ACM, overheat (?) – it will "trip" automatically –
Which means some loss of pressurized air – the 757 has 2 ACM's – the 747 has 3 ACM's…

With nearly 40 years as pilot (and as flight engineer initially = I knew how to keep passengers "comfy") –
Be aware that a 747 cabin with 400 passengers is not easy to keep "cool" –
400 human bodies emit a lot of "calories" – compare that to 400 "100 watts lightbulbs" for heat –
This despite the outside air temperature in flight being -50º C –

By contrast, an empty plane cabin (or a cargo airplane without passengers) is difficult to keep warm –
I flew million dollar race horses or polo horses in a 747F –
Keeping the temperature comfortable for these animals is NOT easy –
We take care of million dollar horses BETTER than human passengers…!

What people do not know, window shades should be closed to keep cabins cold (sun rays) –
At night, empty airplanes, closing window shades help keep cabin temperature up –
Cabin crewmembers with experience know what to do with these shades –

If by overheating you are wondering if air friction on an airplane at cruise speeds might cause a problem, it doesn't. At Mach 3 the old SR-71 Blackbird would experience airframe heating and expansion, but airliners cruise much slower, a bit under Mach 1.
The aircraft is flying through air that's at about minus 50. Over heating isn't a problem.
The aircraft is flying through air that's at about minus 50. Over heating isn't a problem.
Jet engines are made out of high heat resistant materials, such as titanium. They also have oil running through them.

Plus, they suck in A LOT of air. The air that they suck in is typically around -50 to -70 degrees at cruising altitude.

Lord Bacon:
Flying at an altitude where the outside temperature is typically around -50 degrees Celsius kind of deals with any heat problems, don't you reckon?
♛ Nicolas ♛:
well they fly really high up.
a 757-200 has a cruise altitude of 35,000. at that altitude, air temperature is around -65.61 degrees F(-54.2 degrees C).
With these air temperatures airplanes actually have to deal with icing on the wings which can cause poor airflow and reduced lift and increased drag. they often use heating systems to keep ice from forming on the important bits of the plane.
The aircraft is flying through air that's at about minus 50. Over heating isn't a problem.

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