Voxon post 8561 Re - paint and temperatures

Submitted: Monday, Jan 12, 2004 at 20:25
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Voxon made an interesting observation back in mid November when he used temperature probe to check the temperature of various paint colours. There was a little bit of comment at the time which was lighthearted enough.

Last week I posted a comment in regard to the positioning of the temperature probe in an Engel fridge which I thought inocuous enough until I placed my arm on top of the fridge yesterday.

The day was cool enough, hat and tee shirt but not hot. My head needs the hat. I quickly noticed the feeling of my unfortunate arm on the dark coloured top of the Engel. The sides were a completely different temperature. It does not need hot sun to heat up the dark paint or necessarily the sun on it although it did for a short time.

My point is I guess I am using Voxons thought to suggest that it may need additional insulation to overcome the darker colour paintworks that are nice and fashionable, or perhaps a better choice of colour helps. As travellers it may mean we end up carrying less fuel to keep our cars and our food cool. Yes Voxon, I immediatly thought of your research from my hot arm.Regards

JohnR - Not enough of the right travelling, some here..... some over there.......
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Reply By: jemima puddle duck - Monday, Jan 12, 2004 at 21:15

Monday, Jan 12, 2004 at 21:15
gday john.
good point.
or you could always buy a weaco lol(just stiring)there not blackyou reckon your cute
richard(eskimo)
but im a lot cuter

AnswerID: 42725

Follow Up By: cokeaddict - Monday, Jan 12, 2004 at 21:20

Monday, Jan 12, 2004 at 21:20
Hey guys,
Used my Waeco 80 ltr for the first time last week.
It was in the car for 4 days. I had it set at half way on the green lights as i havent used it before. The freezer is just that, a bloody freezer. And with the hot weather we encountered over the 4 days, those coke cans were bloody marvelous iced cold. Im not knocking the Engel's ok, just wanted to share the fridge story with you all...oh and by the way....

Not 1 once of battery problems either. I am impressed...although, i did park the car on a slope just incase they did die...and NO i dont mean asian.I love it when you talk DIRTY !
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Follow Up By: pathfinder - Tuesday, Jan 13, 2004 at 12:42

Tuesday, Jan 13, 2004 at 12:42
could probably do without the racist slur thanks cokeaddict...
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Reply By: Voxson (Adelaide) - Monday, Jan 12, 2004 at 22:00

Monday, Jan 12, 2004 at 22:00
Hi John R.... It was a while ago that i first even took an interest in measuring car paint temps..... One day i was leaning on my mates Bravo 4x4 (against the top of the bonnet) having a yak...... Both of our vehicles had not been running that day and when i lent on my bonnet it was unbearable to touch...... His was just warm.... (white vs patrol dark green).......Since then i have bought dick smith thermometers and placed them in my car (which is white now) and my mates blue patrol and mine is always 2 - 4 degrees cooler whilst we have been driving under the exact same conditions and we have swapped thermometers and the same occurs...... It is a difference of up to 10 degrees so far with stationary testing but we havent left our cars in over 36 degree temperatures yet.....___________________________________
Simpson trip 05/04 then turn left at Birdsville to Darwin via Lawn Hill etc
___________________________________
AnswerID: 42739

Follow Up By: Member - JohnR - Monday, Jan 12, 2004 at 22:42

Monday, Jan 12, 2004 at 22:42
G'day Voxson, I thought it was worthy of discussion when you first brought it up. When I was in South Aussie before Christmas in the warm and the placement of the temperature probe meant such a difference to the temperature reading in the fridge.

I just think we probably have to apply a bit more thought to our selection, and Engel too perhaps for their colours.

Thanks for the comment to make us think. I reckon mine will be cooler now with a roof rack full. Regards

JohnR - Not enough of the right travelling, some here..... some over there.......
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Reply By: David N. - Tuesday, Jan 13, 2004 at 07:56

Tuesday, Jan 13, 2004 at 07:56
I reckon with our summers any car colour is fine..... as long as it's white!

Also did you know insurance companies have figures which prove darker cars have more accidents- simply because they are harder to see!
Try this any time the visisbility is a bit poor- you'll see a lighter coloured car WAY before a darker one. Hot AND dangerous!!
And yet people are buying dark cars in droves? Since when did fashion follow common-sense..

Like I said, any colour is fine..... as long as it's white!- and for a fridge too!
Basic Physics- I remember well doing experiments on that at school (a long long time ago)
Cheers
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Reply By: Hatcher - Tuesday, Jan 13, 2004 at 09:56

Tuesday, Jan 13, 2004 at 09:56
My wife has a white Chrysler Neon and curiously, my old silver 4Runner was always cooler inside than the Neon, even though the 4Runner had a black canopy. Has anyone compared temperatures on silver cars vs plain colours?
AnswerID: 42777

Reply By: Andrew - Tuesday, Jan 13, 2004 at 12:19

Tuesday, Jan 13, 2004 at 12:19
Colour vs temperature is part of the story. another part is vehicle shape and glass area.
The interior temperature of vehicles is also affected by radiant heat through the glass. If your vehicle shape has less glass area or more shading then you will get less heat inside. So you can't really compare different vehicles makes effectively just based on colour.
However the basics still apply. Light colours reflect more heat and dark colours retain more.

If you have your fridge in direct sunlight absorbing radiant heat it will work a lot harder than if it is shaded and only absorbing ambient heat. We sometimes forget the sun shining through the window onto the fridge.

Same goes for vehicles actually, thats why vehicles with loaded roof racks tend to be cooler inside (and why old land rovers had safari roofs).

Interesting thing about window tinting is that the vehicle can actually get hotter inside when parked because the tint acts an insulator in both directions so that the heat thet gets in doesn't get out easily. Of course if you have the air on it is irellevant.

just for thought

regards
A
AnswerID: 42794

Follow Up By: Member - JohnR - Tuesday, Jan 13, 2004 at 17:28

Tuesday, Jan 13, 2004 at 17:28
Andrew, some good points there, but the point on the paint is the one I was trying to draw attention to. In the case above of my Engel in South Aussie the fridge was by a tinted window but in a camper box I thought it would be more likely to get ambient heat than the radiant from the glass.

In another post Michelle drew attention to putting a tea towel over the top of the fridge to dry and also to act as a Coolgardie safe as the water evaporated. I think it would also help the insulation against the radiant heat. Any towel over the top would be useful.

With my camper box there is absolutely no insulation. The point on safari roofs is valid too. Tent flys too, as far as that is concerned. It is also interesting to feel tinted glass absorbing heat and energy, I don't know how much is radiated but the energy is reduced to the skin I have felt.

The post further above about visibility is valid too but not one I was concerned with in the thoughts here for the time being.

I would be interested in further information from Voxson or anyone else about the colour temperature linkages, including white/silver/gold!Regards

JohnR - Not enough of the right travelling, some here..... some over there.......
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Follow Up By: Voxson (Adelaide) - Tuesday, Jan 13, 2004 at 23:30

Tuesday, Jan 13, 2004 at 23:30
I think i will take that challenge.............___________________________________
Simpson trip 05/04 then turn left at Birdsville to Darwin via Lawn Hill etc
___________________________________
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Follow Up By: Member - Eskimo - Wednesday, Jan 14, 2004 at 08:19

Wednesday, Jan 14, 2004 at 08:19
Solar reflective films reflect solar but increase thermal heat gains.

Cant beat good insulation ... 40 mm is a minimum starting point...just llok at domestic fridges....the manufacturers have made this decision based on cost to make v running costs.

However more is better ...hence tha ozzie standards are increasing for minimum insulation requirements to houses.

Heat load calculations tell us this also.

Fridges (car ones too) like cool air for condensing so try to keep the car as cool as possible during warm to hot days. Compressors do not like running at high ambient such as 45 or more. They become very less efficient when temps start to climb. Remember at an outside temp of 35 could mean the inside of car could be 45+ (which is the ambient for the fridge)

Also a dark coloured vehicle on the move is not a big heat gain to the interior. The heat is removed by the increased air speed over the panels. Most gains/losses come from glass and infiltration (small gaps that allow outside air in). (Being Stationary Is Another Story But!) Wow! am I cute
If yer ain't fishing, Yer ain't livin
Richard
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Reply By: Member Colin - NSW Bungendore - Wednesday, Jan 14, 2004 at 21:59

Wednesday, Jan 14, 2004 at 21:59
I am an avid anti Henry Ford fan !? - He said 'you can have your car in any colour providing it is black'

Well colour makes a huge difference - all my cars bar one have either been white or silver.
And in regard to frigs, the same applies - I covered my BROWN 3 way frig in self adhesive foam backed foil bought from Clark Rubber - this made a huge difference to the inside frig temp.Subaru Forester
"size isn't everything"
AnswerID: 43022

Follow Up By: Member - JohnR - Wednesday, Jan 14, 2004 at 22:30

Wednesday, Jan 14, 2004 at 22:30
Colin, won't comment on Ford generalisations or Colin ones either but would be interested in any measured responses to how big the 'huge' defference was.

Not that I don't believe you, would be interesting too whether it is the foam or the foil that made the greater difference. I may ultimately go the same way with the fridge;-)Regards

JohnR - Not enough of the right travelling, some here..... some over there.......
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Follow Up By: Member Colin - NSW Bungendore - Thursday, Jan 15, 2004 at 23:33

Thursday, Jan 15, 2004 at 23:33
JohnR
Sorry - no measured responses in regard to the foam/foil change.
I didn't take any measurements but the cooling element inside the frig now frosts up on 12v - it only ever got cold to touch before the changes.

I have to admit that this change was part of '3 way' changes I made to the frig.
1. the foil
2. changed to power supply to heavy wire direct from battery
3. added a computer fan to rear

So the drop in temperature was from a combination of changes but the added insulation/reflection (doubled the thickness) I believe would have had the most effect ?? The colour must make a difference as well - just feel the difference in temp when touching the outside of a white and a dark coloured car. I also have window film on this car - you can feel the extra heat when you wind down the window in full sun.

So the the answer is - all these changes help.

Subaru Forester
"size isn't everything"
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FollowupID: 305504

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