Well I must confess you made me smile. Any way, I think effects and conditions are quite different than you thought. Let me say what I think, If it goes up to the thousand feets, it means less oxygen, and air density is lower. Lower air density should mean slower movement in copper. Assume it's DC and constant current, its level isn't changing but its time are going to be different with regard to either it has more oxygen or less. Do we want it to act slower or faster as much as possible to not get a quite heat loss? I say, we must want it act faster. So in my opinion, we don't need it has a thin hard layer since it normally prevents further oxidation.Does the hammer deform the anvil, or knock it up in the air? Is there a reason you smack the anvil on the way up instead of just on the way down (put the anvil on the right side)?
That's okay! Yes, about the heat dissipation differences for the busbar once it is oxidized, and relationship from over the altitude difference. Do you think I'm wrong about what I've written in the previous post?I'm so sorry! I meant that reply for a different thread, and somehow it ended up here! I was wondering where my reply went! Doh!
I did do some searching on your question, to try to find out what the difference in heat conduction is for copper oxide versus clean copper, but I wasn't able to find anything helpful.
Are you asking about the oxidation rate of the copper versus time at altitude, or about the heat dissipation differences for the busbar once it is oxidized?
Sorry, what is "it" in this quote?Do we want it to act slower or faster as much as possible to not get a quite heat loss? I say, we must want it act faster.
I meant current, so do electrons. DC source will pomp the electrons, but electrons' speed must be variable depends on amount of oxygen in my opinion. Low oxygen, low speed of act of the electrons that's what I thought.Sorry, what is "it" in this quote?
You can coat a bar with some material that has higher thermal resistance than the copper. But if the layer is thin, it only makes a small difference.Summary: In what ways an aircraft ,at over 35000 feet, imply methods to dissipate the heat generated in a busbar? What's done to get away from the heat with ease?
means lower the heat and get away with ease, Doesn't it?
I appreciate, Tom. That's what I wanted to hear.A quick search shows Thermal conductivity of CuO around 20 to 80 W/mK. The Thermal conductivity of pure Cu about 400 W/mk. Since the Oxide layer is so thin I would expect little temperature difference in free air at sea level.
In free air most heat loss is due to convection, that is the air moving past the busbar is heated by conduction and the heat carried away as the air moves away.
In a vacuum, heat loss is mostly by radiation to the surroundings, and some by conduction through anything touching the busbar.
'Emissivity' is how well a material radiates energy compared to how well a 'perfect' emitter would radiate energy at the same temperature. An emissivity of 0.1 indicates the material radiates 1/10 the energy that a 'perfect' (emissivity = 1) radiator would radiate.
Polished, bare Copper has an emissitivity around 0.035. A thick Black Oxide layer raises the emissitivity to 0.78, over 20 times greater.
At high altitudes (lower air pressure, closer to a vacuum), heat transfer by radiation gets larger than heat loss by convection. So you would like a layer of Oxide on the Copper to help keep it cool.
Cheers,
Tom
I'm talking about a busbar or a cable. They're with the engine part. I'm not sure you're thinking this through. You can't expect a cable to feel -57C. Convective is a natural way of cooling at a sea level. At higher altitudes around 35000 feet, Radiation looks like the only way. AND, I don't get why you expect the conductor to be made from Aluminium, Copper's higher conductivity and much more durable.Copper conductors are often tin or zinc plated to prevent surface oxide formation.
In an aircraft I would expect the conductor to be made, not from copper, but from aluminium, plated with a conductive metal.
Heat radiation and conduction are not dependent on air density or pressure. Convective cooling is dependent on air density.
Outside the cabin, at 35,000 feet, the air is only about 30% of the density at sea level, so it provides less convective cooling. But the temperature at 35,000 feet is stable and close to –57°C, which lowers the resistance of the conductor.
Inside the cabin, air pressure is maintained to be equivalent to a maximum altitude of about 7,000 feet. Convective cooling and heatsinks then work normally, as specified.
I thought it through years ago. You have not googled or researched the subject.I'm not sure you're thinking this through.
I appreciate, but conductivity wasn't the only factor that i thought. BUT, thanks any way, I'll dig up much more than I did.I thought it through years ago. You have not googled or researched the subject.
Start at page 73; https://www.nexans.com/Poland/2007/Aircraft.pdf
General info; http://www.flight-mechanic.com/wiring-installation-wire-types/
I'm talking about a busbar or a cable. They're with the engine part. I'm not sure you're thinking this through. You can't expect a cable to feel -57C. Convective is a natural way of cooling at a sea level. At higher altitudes around 35000 feet, Radiation looks like the only way. AND, I don't get why you expect the conductor to be made from Aluminium, Copper's higher conductivity and much more durable.