Car radiator

[paulo1913]

I have a homework question which I am stuck on part of it...

 

A particular car radiator works by the hot air from the car conducting heat on to medal fins in the pipes. What does the color of the tubes have to do with the radiator?

 

I was completly stuck on this... any help appreciated...

[Fred56]

Maybe its meant to be a sign, like one tube goes in the other goes out, type a thing.

[iNow]

I think paulo might have speaking of the change of color in the metal due to the expansion and contraction of heating and cooling... like in an exhaust pipe on a motorcycle for instance, will turn interesting shades of purple.

 

Paulo... can you clarify? Is this a color like on electrical wires used to tell the difference before they are even installed, or the color metal due to heating and cooling, or something else entirely?

[MrMongoose]

If its a radiator, it will be radiating and different coloured things have different emissivities. I like Fred's answer, but mines more likely to be what a hand wavy physics teacher is getting at.

[tvp45]

I have a homework question which I am stuck on part of it...

 

A particular car radiator works by the hot air from the car conducting heat on to medal fins in the pipes. What does the color of the tubes have to do with the radiator?

 

I was completly stuck on this... any help appreciated...

 

Most car radiators are black because that is the cheapest, most widely accepted, color of corrosion protection.

 

Car radiators are not actually radiators but rather convectors (or, properly, heat exchangers) and work by having hot liquid flow from the engine into the tubes where the heat is conducted to fins, past which cooling air is forced either by a fan or movement of the car. Corrosion inhibits that process.

 

The cooling fluid normally contains corrosion inhibitors to control corrosion inside the tubes. The outside of the tubes actually doesn't matter much - it's the outside of the fins you want to protect - but as long as you're coating the fins, the tubes are free, and the outside is coated with a corrosion protection like, for example, anodizing.

 

Many people think the black color has something to do with emissivity. It does not. The confusion arises from the fact that perfect emissivity is known as "Black Body Radiation". In fact, there are polished aluminum radiators, quite shiny, that work perfectly well. If you were willing to pay for it, you could even have an electric green radiator.

 

Mr. Mongoose is probably right in thinking your teacher is a hand waver. I'd bet the answer he is looking for is that black radiates better.