jeff1000man

THere is some new info for the brain. I've seen a lot of chrome plated coolers and I bet no of them have ever thought about that. My self included. Guess I will have to see how it holds up now.

bustedbrick

Are the internals plated too? Chroming the exterior shouldn't make a huge difference the primary heat transfer occurs internally between oil and water.

getrdunn

iTrader: (7)

I hear what your saying however grab your cooler immeadiately after running WOT for a few minutes. The heat still needs to disapate. It's similar to that of your engine as well. No paint at all would probably be the best however not real advised unless it's all aluminum. After a lot of R&D the experts claim Black paint supposedly disapates the heat the most to my knowledge. Do a reasearch on it. You'll be surprised. Sounds way out there however it's true.

bustedbrick

This will be boring, beware.

I think it's a bit blown out of proportion the affect of color on heat transfer. Heat transfer takes place via three methods: Conduction (two pieces stuck together), Convection (fluids flowing by something carrying heat away), and Radiation (how you get hot under stage light or the sun). The color of a surface only affects its radiative properties, nothing else. Black absorbs the most radiation (i.e. black boat in the sun), and it also emits the most radiation (what's you're referring to). The reason why I say that it's blown out of proportion is that in the real world, radiation only becomes a dominant heat transfer method at high temps, typically higher than what we see. By far more important typically are the conduction (two surfaces bonded together) and convection, where a fluid passing over something hot carries heat away.

Assume for this case that in our oil cooler, the oil is hotter than either the air or the water. It's the likely scenario anyway. You have three fluids (air, water, and oil) exchanging heat across a couple copper barriers. Oil is in the shell, cold water is in the tubes, and cold air is outside. The two ways oil will lose heat is into the water and into the air.

The water is a much much better fluid at keeping the copper that touches it cold. This is because of its properties and the fact that it is being pumped through the tubes so the tubes are always flushed with cold water. The air on the outside is pretty stagnant for one, and moreover it's properties are not as favorable for pulling heat away from a surface. You can test this pretty easily. Hold your hand out of the window when its 40F and it will cool down. Now drag it through water at 40F and it will be cold much quicker. This is convection. The water does a much better job at conducting heat away from your hand.

The chrome plating is adding a layer of insulation to the outside of the cooler, so yes, it will diminsh the transfer of heat with the air because heat will have to transfer between the copper and now a heavy coating of chrome.

But the main reason why marine oil coolers function is the water through the tubes pulling heat out of the oil, not the air around the outside.

I'll eat my words if I'm wrong.

Mr. Cool

You want boring? Hold on Buster Brown (hehe) :

Re: Chrome plating: I'm an engineer. I say that because I read bustedbrick's post and began investigating because it was so logical but fought with what I had learned from someone 35 years in the business of making heat exchangers. I've seen this 40% efficacy loss posted on a reputable source's web page and confirmed that before posting it (I'm not gonna swat them publicly) and heard it for so long I believed it to be true. It's not. I'll eat crow publicly on this. Wrong is wrong.

But as with many wives tales, it is based on some relationship to the truth. It is not chrome plated coolers that are the issue. It is stainless steel (which looks like chrome to a degree when polished) because of the change in transmissivity between copper and SS. I'm not hanging my hat on any 40% number but there is a substantial change in the rate of transmissivity (ability to transfer heat) between Stainless Steel and Cu.

The following is an unconfirmed story -- Commander engines -- overheating sunk the company. This occurred because they changed from copper to SS 1:1 on length. Overheating was rampant. Can anyone confirm?

In Chrome plating A continuous deposition of ni ~.0007" and then chrome ~.000020" (dims close?) are applied and what you actually see is the nickel showing through the chrome. So what bustedbrick said is completely logical. A coating on the outside (and yes, it's only on the outside) shouldn't effect the heat transfer on the inside.

I'm kinda glad he called me out on it.

I hope it doesn't make me seem like a dummy head out touting stuff like this - I thought it was true. The rest of that stuff I wrote is personal experience and chemistry.

This is my second public apology and I plan on making it my last ... but I don't have an editor... :-)

I'm going to look into the black paint vs no paint.

jeff1000man

I thought the 40% was a little high, but I am not going there. There is a certain percentage of heat transfer that is slowed by coating the outside of any type heat exchanger. It is not a number that can be used across the board.

So many factors go into the efficiency of a heat exchanger ex: water flow (voume), water temperature, air temperature (is the water being cooled or heated by outside air((if it is, how much effect is the coating having on the AIR heat transfer while the internal process of heat transfer is going on)))?

Also volume (capacity of the cooler)? If you are using a cooler designed for a 500HP engine and you isntall it on a 600HP engine, wouldn't the cooler all ready be over loaded? If you painted, powedered, or chromed this cooler? Would not the coating affect the ability of this cooler to try and work to it's peak capacity??

Just food for thought. I have no research or data to go with this. just thought it sounded logical.

bustedbrick

Stainless is about 25 times less conductive than copper.

As far as black versus unpainted, I'll take a stab that unpainted will be better only because there is no layer of insulation (paint), nothing to do with it's color. Color only affects radiation, and at the temperatures we mess around at 220F for oil, radiation is not a big factor, therefore color is not a big factor. Remember radiation doesn't need air to work. The sun heats you up even though there is no air in space.

The bigger factor will be the air flowing by the cooler and carrying heat away. The color doesn't matter here either, but the effect of a layer of plastic paint will insulate the cooler.

Good thread, and Mr. Cool, I certainly wasn't trying to come off as a snob engineer!

stoltz

I powder coated my oil cooler to have it match the engine block. When i got it back the ends that were sodered in were not there any more. Also had it pressure tested afterwards and it had leaks. So I ended up taking it to a radator shop to get repaired. After all the hasle and time it would have been cheaper to buy a new one. My thoughts are just buy a new one bigger than you think you will need and get the color you want and don't go through the headack that I ran in to.

Mr. Cool

I didn't think that sir and I hope I didn't come off that way either. I felt bad for posting very wrong information and was kinda trying to make up for it. I chatted with a PhD in heat transfer from a local university who I happen to know. He said mathematically there should be little effect from the coating at the thicknesses we're talking about (which confirms your post), then followed with "but you should test it". Then bounced that off of some old salts I know and they agreed that it made sense. I appreciated your post Bustedbrick. If I came off disrespectful, please accept my apologies.

from that PhD and confirmed by Mr. Cool experience (the company's experience): The largest contributors to heat transfer are reaching the right fluid speeds (reynolds number), delta in temp between seawater and oil, and cooler surface area. But many of you already knew that :-).

OK...phew....

klaw

ok we also have the pesky laminar versus turbulent flow in this mix

And also who uses parallel flow versus counter flow?

I liked machine design much better so I prob fell asleep in my Thermo and Incompresable fluid flow classes so I am just babblling

LOL