Car AC theory question

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Well, it's close, I forgot it's not the molecule itself that gets less dense but as Trader4 pointed out it's the spacing between the molecules that increases which makes the gas or liquid less dense. I was a physics major in college 40 years ago and I can't remember how to write a fancy calculation even if you put a gun to my head. ^_^

TDD

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It could be more stuff I forgot after all these years. I can't remember the specifics but I suppose I was thinking the change in energy level was caused by added electrons but now I seem to recall the added energy is simply winding up the molecule increasing the speed of particles and changing their orbit around the nucleus. Since stable identical molecules repel each other perhaps this increase in energy causes the increase in spacing. Heck it's been so many years since I was immersed in physics and I been busy making a living so I've used those brain cells for other things. It's a good thing I have Internet access, now I can go back and refresh my memory. I remember living in libraries but I can't sit still that long anymore. ^_^

Thanks, my physician friend who helps me is a cardiologist and we discus what works best since I despise drugs and having to take the darn things. I'll probably wind up on another anti-inflammatory at a lower dose that won't melt my brain. o_O

TDD

The correct term is turbo oven. That's what they started calling them in the late 70's. When they started to become popular in the 90's marketing thought convection was a better name. NOT.

Greg

There comes a point where the better emissivity of the black and the poorer conduction of the paint cancel out. I expect that where air movement is adequate, the non painted unit would be more effective. Where air movement is limited, the darker colour MAY help.

I believe the black paint is for protection.

I wouldn't discount that at all since I've seen a lot of corrosion damage done to condensers that were made from aluminum. Interestingly enough, the small condensing units that are under those soft drink vending machines are often painted black even if the fins are galvanized steel. ^_^

TDD

galvanized steel cooling fins??? are you sure or are you guessing? steel's a poor conductor and it's much harder to make gas-tight joins as easily as brass/copper/aluminum. i can't imagine why anyone would use it.

I own a small condensing unit from a vending machine that has steel fins that I've used for years as a recovery system for refrigerant. I purchased a new one a while back for an old Coke vending machine and that new unit has steel fins. Many soft drink vending machines have steel finned condensing units underneath them because they are more durable and less likely to be damaged by the myriad environments those types of machines wind up in. ^_^

TDD

i guess that would be a "specialty application". but how did you determine their material? when you say "fins", do you mean the grate-like arrangement at the back of a common refrigerator?

The condenser coil on the vending looks like a small radiator with a fan. The condensing unit is usually underneath mounted on a steel base with the compressor. The units can be slid out for servicing and or replacement. Take a look under a Coke vending machine or glass door Coke box and you may see the condensing unit. If you see a vender loading a soft drink vending machine, the door will be open and the condensing unit should be visible at the bottom. Ask the guy to point out the condensing unit for you. ^_^

TDD

Gas tight joints are not required between fins and tubes. The tubes are generally copper or tin-plated copper, with the find press fit to the tubing.- not even soldered in many cases.

true.

right

fins?

that's where i'm having the problem. steel is a poor conductor - it makes more sense to have the tubes steel and the fine fins made of copper or aluminum than the other way around.