Insulation idea

[goshawks00]

This is a good read... it's a hotrod site, and the ceramic bead use is of much interest in keeping our hotrods cool with lots of engine heat passing buy. Also good places to buy what you need.

alternative to Lizard Skin
clipped from Google - 1/2012

Hopefully this link will take you there ..if you know how

Barry

[FC7039]

This is my current understanding of radiant barriers and Airstreams. They may be wrong. I got this all by reading the internet so it must be trueJ

Please feel free to educate me.

Sun light that hits the Earth and your trailer is mostly not in the infrared (IR) spectrum. Any radiation from the sun only heats the outer skin of the trailer and does not heat anything past the outer skin. White reflects sun better than aluminum so a white surface heats slower than an aluminum surface. Brighter and shinier improve this reflectivity. Shinier (less surface area) also improves emissivity of radiation (read further).

I do not know what properties reflect or absord IR radiation. I have read the silver and aluminum or good at it. We see these as shiny, but I have no idea if light reflectiivty has has any effect as IR is not visible. What about a material refelcts IR?

The heated outer skin gives off heat by the three heat methods of conductivity, convection, and radiation.

The outer skin conducts heat to the ribs that it touches. This is a very efficient method and transfers the heat well through the ribs to the inner skin. It also conducts heat through any insulation touching the outer skin. Usually insulation material is poor at conducting heat and is inefficient at transferring the heat from the outer skin to the inner skin.

The outer skin also heats any air in between the skins via convection. The air in turn, conducts heat to the inner skin. This also is not very efficient, but with a limited amount of air to absorb the outer skin heat, the air via convection heats to as close to the out skin as possible and conducts its heat to the inner skin.

The outer skin heated by the sun radiates IR waves to the next object in its path, either insulation or a radiant barrier (the inner skin is a radiant barrier), (all things are radiant barriers, some better than others, most being poor at it, aluminum and silver, being good at it, white paint is poor at it). Materials good at reflecting radiation are poor at emitting radiation. Aluminum does not emit radiation that well so its radiant heating of the inner skin is inefficient.

My conclusions are:
1. A thin radiant barrier as insulation probably has little effect. I believe that the air heated by convection will conduct through the barrier (highly conductive) and heat the air on the other side which will in turn heat the inner skin.
2. Polishing the inner skin (facing out) would act as a radiant barrier.
3. Venting between the skins would probably have the greatest impact as this would reduce the convection which is probably the greatest
transfer of heat.
4. If you cannot vent the space, then add insulation that retards air movement and convection, but does not touch the inner skin, as it is a radiant barrier, being aluminum. I think though it would only reflect the radiant heat of the insulation. It may be better to just fill the whole space.
5. Polishing the inner skin facing in would greatly reduce the radiant heat from the skin to a person or object.
6. Any method to retard the conductivity between the ribs and skins without reducing the monocoque construction (I believe a less than rigid rivet of the skins would introduce too much movement and lead to eventual failure). I plan to test ceramic infused paint (HSC-1500)

I plan to test these hypothesis’ here shortly. Please feel free to add and ask and suggest other methods to test.

[aluminitus]

I purchased some HSC (apparently HSC-1500 is no longer made, but HSC has better thermal properties) this morning and will post on my airforum blog how it works out.