term describing infrared trapping efficiency?
 

does anybody know if there is a word or measurement that describes that
efficiency at which a substance traps longer waved solar radiation?

For example glass is pretty good at trapping heat, so that may be rated at
100 "Scovillage" units or possibly it could be described as having a
"Maxwell" rating of .5 celsius per second per cubic meter. Polycarbonate
also used for green/glass houses may have a similar values while brick or
other opaque materials would be close to zero. What would the real term
for Scovillage or Maxwell be?

On Thu, 26 Aug 2004 05:44:55 GMT, Salty Thumb
wrote:

does anybody know if there is a word or measurement that describes that
efficiency at which a substance traps longer waved solar radiation?

For example glass is pretty good at trapping heat, so that may be rated at
100 "Scovillage" units or possibly it could be described as having a
"Maxwell" rating of .5 celsius per second per cubic meter. Polycarbonate
also used for green/glass houses may have a similar values while brick or
other opaque materials would be close to zero. What would the real term
for Scovillage or Maxwell be?

Greenhouses? Child/pet endangerment units?

there is specific heat capacity
http://scienceworld.wolfram.com/phys...tCapacity.html
greenhouse gases
http://www.eia.doe.gov/oiaf/1605/ggccebro/chapter1.html
ability to absorb infrared and NOT re-emit it. CO2 and methane CH4 have very high
absorption/retention rate way beyond ability of individual atoms.
Ingrid

Salty Thumb wrote:

does anybody know if there is a word or measurement that describes that
efficiency at which a substance traps longer waved solar radiation?

For example glass is pretty good at trapping heat, so that may be rated at
100 "Scovillage" units or possibly it could be described as having a
"Maxwell" rating of .5 celsius per second per cubic meter. Polycarbonate
also used for green/glass houses may have a similar values while brick or
other opaque materials would be close to zero. What would the real term
for Scovillage or Maxwell be?



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Unfortunately, I receive no money, gifts, discounts or other
compensation for all the damn work I do, nor for any of the
endorsements or recommendations I make.

If it what you want is truly a measure of efficiency, then it would be
unit-less. (It's just a ratio)

For example:

The energy of one 680 nm photon is:
E = hc/?
10-19 J

Photosynthesis requires 59 kJ per mol of ATP. Meaning that:
EATP = 59 10 3 J mol-1 / 6.022 1023 mol-1 = 9.80 10-20 J per ATP
molecule.

So, the energy efficiency of photosynthesis is:
= 9.80 10 -20 J /2.92 10-19 J = 0.34 or 34%

Salty Thumb wrote in
news:rNeXc.1129$Cc.449@trnddc07:

does anybody know if there is a word or measurement that describes
that efficiency at which a substance traps longer waved solar
radiation?

For example glass is pretty good at trapping heat, so that may be
rated at 100 "Scovillage" units or possibly it could be described as
having a "Maxwell" rating of .5 celsius per second per cubic meter.
Polycarbonate also used for green/glass houses may have a similar
values while brick or other opaque materials would be close to zero.
What would the real term for Scovillage or Maxwell be?

I would be surprised if there were such a term because the greenhouse
effect is not a property of the material alone. The obvious (to me, at
least) variables a
1) The spectrum of the incoming radiation. For an incandescent
source such as the sun this is mostly determined by the source
temperature. (The "surface" of the sun is about 6000 K) But
atmospheric absorption figures in this as well.
2) The spectrum of outgoing radiation. This is mostly determined
by the temperature reached by surfaces inside the greenhouse.
3) The transmission coefficient of the glass at every wavelength.

Also, it is not meaningful to talk about the greenhouse effect with
opaque materials as there is no radiation passing through. (Unless you
want to talk about x-rays and gamma rays.)

--
----------------------------------------------------------------
A L B E R T A Alfred Falk
R E S E A R C H Information Systems Dept (780)450-5185
C O U N C I L 250 Karl Clark Road
Edmonton, Alberta, Canada
http://www.arc.ab.ca/ T6N 1E4
http://www.arc.ab.ca/staff/falk/

Alfred Falk wrote in
:

Salty Thumb wrote in
news:rNeXc.1129$Cc.449@trnddc07:

does anybody know if there is a word or measurement that describes
that efficiency at which a substance traps longer waved solar
radiation?

For example glass is pretty good at trapping heat, so that may be
rated at 100 "Scovillage" units or possibly it could be described as
having a "Maxwell" rating of .5 celsius per second per cubic meter.
Polycarbonate also used for green/glass houses may have a similar
values while brick or other opaque materials would be close to zero.
What would the real term for Scovillage or Maxwell be?

I would be surprised if there were such a term because the greenhouse
effect is not a property of the material alone. The obvious (to me,
at least) variables a
1) The spectrum of the incoming radiation. For an
incandescent
source such as the sun this is mostly determined by the source
temperature. (The "surface" of the sun is about 6000 K) But
atmospheric absorption figures in this as well.
2) The spectrum of outgoing radiation. This is mostly
determined
by the temperature reached by surfaces inside the greenhouse.
3) The transmission coefficient of the glass at every
wavelength.

Also, it is not meaningful to talk about the greenhouse effect with
opaque materials as there is no radiation passing through. (Unless
you want to talk about x-rays and gamma rays.)


I didn't like my chances, either, but I thought I'd ask anyway. To
clarify, I'm looking for a term that enables comparisons of different
materials for use in a greenhouse application. The term/measurement
doesn't necessarily have to have mathematical precision, but if there is
a directly measurable value that's good too. Something like R- values
for building insulation in the US, or PR/+ ratings for microprocessors.

If the E in low E (emissivity) glass is quantifiable (even with some
fudging allowed) and not just some vaccuous idea, then that's probably
exactly what I'm looking for.

Seems polycarbonate is widely used, but is that because of superior
trapping or a combination of trapping, structural strength, price and/or
other?. I'd also like to see how Lexan, plain plexiglass, clear PVC and
one other clear plastic (don't remember off hand) compare solely from a
heat trapping / heat retention perspective.

Salty Thumb wrote:

does anybody know if there is a word or measurement that describes that
efficiency at which a substance traps longer waved solar radiation?

I'm jumping back 30 years or so, but I think the ASHRAE Manual
[American Society of Heating & Refrigeration mumble-mumble] has a
table with material's emissivity and absorbtion rates. [and 'transfer
rate' might be a separate table]

The only part of it I remember offhand is that unglazed brick is very
similar to human flesh-- that's why we think of it as 'warm'.

The 'E' in 'E-glass' *is* quantifiable-- though I'm not sure if all
manufacturers use the same standards yet. [they didn't in 1970] The
emissivity is how much of the heat gets passed through-- not how much
gets absorbed/trapped.

Jim