

  (Source: CBS)





Melting Prius owner



Studio City





[Image Source: Jason Mick/DailyTech]


Source: CBS

Comments     Threshold


RE: Umm
By mlmiller1 on 1/26/2012 1:22:39 PM , Rating: 2
The open carport receives enough radiant heat to raise the air from 77 to 120 degrees? Peak solar about 1kw per meter sq. So 1KW direct from sun and assume 1kw for reflection. With 120 degree ambient. So at what point does the black body mirror housing obtain convective heat balance with the incident radiation of 2kw/meter? Yep about 200C, good melting point for most PVC's

RE: Umm
By AnnihilatorX on 1/26/2012 5:02:38 PM , Rating: 1
Your figure is way too lax.

The black body mirror cannot have 1kw per sq. meter surface area, that's a huge mirror housing.
More like 250cm^2= 0.025m^2.

Reflection is not 100% efficient either, I'd say 90% since you are assuming a 1sq. meter window project all it's reflection on the mirror with no missed beam.

So the radiation input is 0.925kW

RE: Umm
By mlmiller1 on 1/26/2012 5:53:37 PM , Rating: 2
Yep the 2KW / meter sq. is general, but is the rate that a surface receives heat, regardless of the surface area (assuming no lens or focusing effect). This basically cancels area out of this, "back of the envelope" type "is it possible," calculation. Area cancels because convective heat transfer (cooling) very proportional to surface area, as is heating (the area exposed to the radiation (light)).

To be more accurate looks like 85% of infrared ration is reflected for the below film:
PVC melts from 100-260C

So 1.85KW/meter sq. is still enough to melt some PVC. (1kw from sun, .85 from reflection)

Solar Absorption for black paint is 0.98 (white is like 0.25)

From this we can see that if painted white it wouldn't hit over least on the back of the envelope.

From the pic, looks like the convective currents (at the more vertical parts) get cooled enough. Its just the top has a slower moving air currents and then heats up, then melts.

