Superhub : overheating

[grantus1]

hi
got a problem with the dark green cabinets the colour it self is a problem it will absorb & retain heat so if these where painted say light grey it would reflect some of heat that builds up in these cabinets.
ps can we let sir richard branson know this when he goes to the near space atmosphere. simple technology for outer space.

[Sirius]

Originally Posted by grantus1

hi
got a problem with the dark green cabinets the colour it self is a problem it will absorb & retain heat so if these where painted say light grey it would reflect some of heat that builds up in these cabinets.
ps can we let sir richard branson know this when he goes to the near space atmosphere. simple technology for outer space.

http://www.cableforum.co.uk/board/12...een-boxes.html

[craigj2k12]

the new ones are grey, read through the thread sirius has linked

[AndyCalling]

Colour has no effect on heat retention. It is all myth. That is unless it is silvered well to reflect the heat, but that would be distracting to traffic and probably more expensive.

[jb66]

It does work actually, they had sensors in the cabs and the white ones were cooler

[AndyCalling]

Well that's odd. Experiments done regarding clothing show colour as having no effect. Could it be the materials used in making each paint causing the difference?

[jb66]

Well whites more reflective so It won't absorb as much heat, I guess it's why folk who live near the desert wear white clothes and tesco refrigerator lorries are white

[qasdfdsaq]

We're not talking about clothing here AND we're not talking about heat retention. What we're looking for is heat reflection.

jb66 gets it spot on.

[AndyCalling]

Originally Posted by jb66

Well whites more reflective so It won't absorb as much heat, I guess it's why folk who live near the desert wear white clothes and tesco refrigerator lorries are white

Well, with clothing many wear black in hot and desert countries. In tests, neither black nor white nor any other light or dark colour made a difference. For clothing. Not to heat retention nor reflection. To reflect (or indeed to insulate by reflecting back in) the material has to be silvered like those mylar sheets marathon runners use after a race. If white did reflect heat like silvered material does then it would insulate internally radiated heat as well as shield against external sources of course. It doesn't though. The idea that white or light is more reflective is a myth. The idea that black or dark absorbs more heat is a myth.

We are talking radiated heat here of course.

Colour shouldn't make a difference with anything else either (such as cabs), where radiated heat is concerned. Other varient qualities in the paint might make a difference to conducted or convected heat though. Any varience in cabinet construction across those tested would also play a part as would location and heat generation levels inside the cabs.

Remember, colour is only about our perception. It doesn't actually exist as an innate property of an object.

What the material needs to reflect here is infra-red.

If black were to absorb more heat, it would actually keep that heat from being released into the cab. If it reached capacity then it would be radiating heat instead. This is what we are suggesting white does though. If white reflected then it would insulate the cab by radiating heat in both directions. If there is a difference in how these colours react to infra-red then it's balancing out pretty well. If this is the case then one has to measure the temp of the air inside the cab and not the surface temperature of the cab.

There is a lot to look in to, but I still maintain that the use of non metalic colour to insulate or protect against heat is a myth. A commonly held one though.

[kwikbreaks]

All the BT Infinity cabs that I've seen which all contain active components are khaki so they clearly don't regard the colour as being especially important even though there will doubtless be differences both in absorption and radiation.

Most of the cabs around here are covered in fly posters and graffiti anyway

[ferretuk]

Originally Posted by AndyCalling

...

Nonsense snipped...

Infra red, being close to visible light in the electromagnetic spectrum, behaves very much like light and can be reflected or absorbed.

With light, the variation in different objects reflectivity of different wavelengths gives the perception of colour. Surfaces highly reflective to all wavelengths of light look 'silver', less reflective look 'white', less again look grey (more than 50 shades!) through to black which reflects very little. Surfaces only look to have colour if the reflective property is in some way non-linear i.e. some wavelengths reflect better than others.

Any radiation not reflected is absorbed by the object - For infra red this absorbed radiation heats the object up.

[kwikbreaks]

If you want to be pedantic about this then any absorbed radiation heats it up not just infra red...

[Kymmy]

Originally Posted by jb66

Well whites more reflective so It won't absorb as much heat, I guess it's why folk who live near the desert wear white clothes and tesco refrigerator lorries are white

Clothing in hot areas tends to be natural open fibres to allow airflow and the coloring tends to have nothing to do with it (otherwise don't you think that burkas would be mainly white??)

I will though agree that a solid paint color like on the outside of cabinets will have an effect on internal heat dependant on how much radiant heat it reflects..

[kwikbreaks]

Don't forget that if there are powered components inside then black will radiate surplus heat from them better than white can

[grantus1]

grantus1
hi some of you guys out there are just mmmm a bit too technical i am going to buy some light grey paint and paint the green cabinets a lighter colour.i may be saving vm a fortune by not getting engineers out and wait for it i know there is a problem in the dd3 area of dundee with these dark green cabinets.