Acrylic for solar water purifier

[piuz98]

Hello,
I want to ask some favor about acrylic.
I am trying to build solar water purifier, then i think to use acrylic as a body.
will it melt under sunlight temperature?
because, in the paper said the temperature can reach until 150'C
thx

 

[chayced]

Umm, focused sunlight? Sunlight on a black object? Or just sunlight on an clear acrylic tube?

If you are focusing it then yes, you can go above 150 pretty fast, if not then probably not an issue.

P.S. how are you going to use sunlight to purify water? Boil it to kill bacteria, or some other thermal application?

 

[piuz98]

the design will use vaporation method.
It will have some stages.
i attached the paper also for more clear.
thx

 

[chayced]

Don't see how temperature can go above 100C since it has water at atmospheric pressure flowing through it. This is basically a engineered up version of an old survival trick using a can and a plastic sheet. It relies upon evaporation of heated water vice boiling water. I think Acrylic will work fine.

Just wondering, why are you building one?

 

[piuz98]

OK...
thx for information
hehehe
i am doing project assignment from university...

 

[Redbelly98]

I am wondering if acrylic would soften at these temperatures. If so, polycarbonate may be a better choice.

 

[piuz98]

based from my researched, it might be betterthan acrylic.
but the problem is difficult to find polycarbonate in my place.
somemore, the shape i want to use is not available in the market.
is got, need spend long time to purchase.

 

[chayced]

acrylic may soften depending on the actual operating temp, but remember the project is not at pressure and does not boil the water. I think acrylic will work fine. Could just try building it on the small scale see if it melts then continue with the full sized if you are that concerned.

 

[piuz98]

Hi all...
firstly thanks for helping me in my previous question.

Now, i have another problem in the design.
I want to know, do infrared radiation from sunlight can through black polycarbonate...
because i have confuse with the purpose of put aluminum sheet under the polycarbonate in the solar water purifier design. (it show in pages 435 in attachement).

because i only can found transparant polycarbonate which is uses for roofing.
then, is there any type of polycarbonate in the market or it only uses for roofing?
thx for help.

 

[alxm]

First, to give some input on the original question:
What you need to look out for is the glass transition temperature of your acrylic. The glass transition temperature is the temperature where the plastic gets screwed up. It undergoes a phase transition, deforms and won't go back. (put a PET soda bottle - glass transition at 70C - in some boiling water and you'll see what I mean).

For ordinary acrylic/plexiglass, that temperature is 105C, but there are additives that can increase that value. So it depends entirely on what acrylic you get. But 150C may be out of the question. Polycarbonate on the other hand has a glass transition of 145C. It's much more heat tolerant.

I want to know, do infrared radiation from sunlight can through black polycarbonate...
because i have confuse with the purpose of put aluminum sheet under the polycarbonate in the solar water purifier design. (it show in pages 435 in attachement).

Infrared radiation is heat. So it's absorbed pretty well by black polycarbonate. Which I assume is also the reason why it's supposed to be black. You could probably paint some black if you can't find any black polycarbonate.

 

[Redbelly98]

The black polycarbonate absorbs pretty much all the radiation that hits it. However, the polycarbonate itself radiates long-wave I.R. (8 to 10 μm wavelengths, according to the article). The purpose of the aluminum sheet is to reflect this radiation back onto the polycarbonate.

You can order black polycarbonate from McMaster-Carr, if you're in the USA. If you're in another country, you may or may not be able to order from them.

Scroll down to where it says "opaque black" here:
http://www.mcmaster.com/#catalog/115/3509/=qpd3e
A 2 foot x 2 foot, 1/4-inch thick sheet costs 140 $US.

Compare that to black acrylic, which comes in thinner sheets and is much cheaper. Scroll down to where it says "Colored sheets to order" here:
http://www.mcmaster.com/#catalog/115/3513/=qphre


Also from the McMaster website:

black polycarbonate:
operating temperature -40 to 200 F
softening temperature 290 to 315 F

black acrylic:
operating temp -20 to 170 F
softening temp 196 to 239 F