Barrel coatings test

comnoz · Mar 10, 2015

Barrel paint

I thought I would share the results of testing different barrel coatings. Not exactly the results I was expecting.

[video]http://youtu.be/dJEgo4Fego8[/video]

lcrken · Mar 10, 2015

Great stuff, Jim. Now I can continue using black paint with a clear conscience.

Ken

Biscuit · Mar 10, 2015

Nice conclusion, something Norton probably figured when they put that rock-hard thick whatever it was coating on the black barrels. Looked good, wore well, made no difference regarding heat dissipation.
Me thinks we thinks too much.

comnoz · Mar 10, 2015

Well the factory coating is enamel. I will be using stoving enamel from now on for cast barrels.

The bottleneck is obviously the cast iron so the coating doesn't make much difference.

I suspect the results would be different with aluminum. I also bet I will find out. Jim

Matchless · Mar 10, 2015

Thanks for posting this Jim. Very interesting. Please let us know how aluminium barrels compare. It would be nice to see how the Maney/Dunstall pattern compare to the Les Emery aluminium type, which are modelled on the standard 850 style.

Martyn.

comnoz · Mar 10, 2015

ludwig said:
So , on a moving bike , the coating matters little or none .
But I would think that the type of coating can only have an effect on heat transfer by radiation .
May be a better test would be to switch the fan off to eliminate convection and
see if radiation alone can make a difference , simulating stop and go traffic ?
Or while you're at it : see how quick the different barrels cool after heat and fan are switched off ..?

I will have to give that a try. First I am going to have to come up with a new heating element.
I tried to get a little higher temps and tried to raise the voltage to the element and it didn't take it. Jim

jaydee75 · Mar 10, 2015

I love to watch your test movies and appreciate the time you put in. Surprising results for sure, but mostly due to insulation effects with the coatings mostly due to their thickness. For another test I suggest you try to get the cylinder temp up to like 300F where the radiant heat transfer will be 3.4 times stronger than at 100F. Radiant heat transfer will also show that color does make a difference with a dull black surface much better than a lighter color due to the higher emissivity of the black.
Thanks again for the test.
Jaydee

Anonymous · Mar 10, 2015

I love it when people do science!
Quantitative data to prove or disprove theories is just excellent!
Maybe could have run a survey first to collect qualitative data as to how 'cool' each rider 'felt' using their chosen barrel coating would make them.

Hobot · Mar 10, 2015

2nd Jaydee's statements that the temps and heater btu output so low - this is not a test of anything but what common equilibrium is reached even if barrels wrapped in rags or no air flow. Wrapped may show a dozen F higher but not testing surface finish for high fuel burn and poor wind direction. I'd bet similar temps reached in this test if fins cut off and highly polished back refliecting infra red mirror put on exterior. Surface finish test would need jugs heated over expected operating temp, say 400'F and no fan timed cool downs. If not getting hot enough for the better surface finish to come into play then similar to testing a bigger carb and saying it don't make any more power but only tested from idle to 2000 rpm. Needs El Flamo Grande or ya just proved NASA and coaters are full of poopoo with false advertising and stealling money.

baldy · Mar 10, 2015

Jim,

I suspect the thickness of the powder coat may equal more convective surface area which is your primary mode of cooling. You might try a super thick powder coat and see how it compares.

Baldy

Anonymous · Mar 10, 2015

Hi comnoz.
The coatings debate is now moot thanks to the experiment you have just conducted.
However, should you continue testing for the multiple factors of coatings, thicknesses, materials, barrel designs, manufacturers, temperatures, etc as suggested in this thread you will need Taguchi Design of Experiments to reduce test iterations. Unless you are sitting in your shed looking to fill your days, you may consider accepting donations to offset the time, materials, energy, capital, etc costs that you will need to expend on this project.

Hobot · Mar 10, 2015

too thick of anything ain't good but painting can actually help and black is not always the best color either. Scratch one or your ends on this for next experiment or shot in the dark best finish. Mostly the black on radiators is so they don't show through the fancy grills to onlookers.

http://www.madsci.org/posts/archives/20 ... .Ph.r.html

comnoz · Mar 10, 2015

needing said:
Hi comnoz.
The coatings debate is now moot thanks to the experiment you have just conducted.
However, should you continue testing for the multiple factors of coatings, thicknesses, materials, barrel designs, manufacturers, temperatures, etc as suggested in this thread you will need Taguchi Design of Experiments to reduce test iterations. Unless you are sitting in your shed looking to fill your days, you may consider accepting donations to offset the time, materials, energy, capital, etc costs that you will need to expend on this project.

Since this is just an unpaid spare time project there are definitely some shortcuts involved in my testing. But I am still learning and satisfying my curiosity.

Right now there are 3 barrels soaking at 375 degrees in the oven. 1 with the [aerospace] coating. 1 with powdercoat and 1 with silver high temp "header paint".

This evening I will take them out one at a time a place them in my box with a board in place of the fan. I will start a timer when the temp gets down to 350 degrees and stop the timer when the temp reaches 250. This should be a fair test of the emissivity. Jim

Anonymous · Mar 10, 2015

Hi hobot.
Please explain 'What happens to the heat reflective value of aluminium when it is painted?' from your link http://www.madsci.org/posts/archives/20 ... .Ph.r.html and how it relates to the 'Barrel coatings test' as undertaken by comnoz?
It appears to me to be about heat/light reflection of aluminium foil on mylar and, I think, how to keep your cooler cool (I also interpret 'cooler' to mean 'esky' in Stine).

baldy · Mar 10, 2015

Black color is always the best for radiation heat transfer. Engineers who design automotive radiators know what they are doing. I believe dull black is best but who wants a dull barrel on your combat.

Hobot · Mar 10, 2015

needless why the show down attitude I'm making no claims nor selling anything just pointing at sites that may or may not apply. I'm half fast up on lens and solar panel coatings but we'll have to wait for fractual surface etching nprep for graphene flakes laid on then forest of nano carbon tubes coated - when it becomes affordable.
Colors only affect what wavelenghts reflected so little to do with heat conduction of coating.

texasSlick · Mar 10, 2015

Surface roughness has a large effect on convective heat transfer.

A thick coating may cover the sand cast texture, smoothing out the roughness, and reducing convective heat transfer. Polishing the fin surfaces has the same effect.

Surface roughness increases heat transfer as follows:

The roughness breaks up the laminar boundary layer, creating a turbulent boundary layer. The turbulent eddies move heat from the laminar sub-layer (the micro thin layer of air smack next to the surface) to the moving air stream by mixing. Heat moves thru a laminar boundary layer mostly by conduction (less effective than mixing).

Slick

Anonymous · Mar 10, 2015

The test comnoz has conducted is for the insulating properties of various coloured paints vs plastic (powdercoat) compared to the convection of heat from uncoated barrels. The findings show a little variation around 110°F as measured at the thermocouple in the barrels. Interpretation: my factory painted black barrels just looked 'cool' in keeping with the 'manhood' era.

His current test is for radiant heat loss and the insulating effects of the coatings on the barrels so surface roughness/smoothness, lamina flow, etc are negated.
That's enough to make any betting person baulk!

texasSlick · Mar 10, 2015

baldy said:
Black color is always the best for radiation heat transfer. Engineers who design automotive radiators know what they are doing. I believe dull black is best but who wants a dull barrel on your combat.

True. The operative word here is "radiation" heat transfer. Color has little effect on conductive or convective heat transfer per Hobot's post above.

Gloss back (emissivity about 0.9) is nearly as good as flat black (emissivity about 0.95), and about 3 times more effective than silver(emissivity about 0.3) for RADIATION heat transfer. In short, black radiates 3 times more heat away from a hot object as silver.

Slick

DogT · Mar 10, 2015

Doesn't surprise me at all, convection will overwhelm radiation nearly anytime. Radiation depends on temperature differential and color, convection depends on surface area, of which the cylinder has plenty.

I'm glad to see the test though, thanks Jim. I guess I won't worry about my silver barrels, not that I did.

Dave
69S

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