So true!!! Why not dress up my 3 sphere radiation demonstration
to prove "once and for all" that back radiation never occurs.
Let me repost this from the beginning of this year
Tom was correct in that anything that inhibits radiation from an
radiating object with a fixed amount of power to radiate will indeed
raise the needed temperature of that object as that is the only way to
overcome that very inhibition and radiate that fixed amount of power.
This is not back radiation nor Greenhouse effect. This is only the
way thermodynamics has been, and must be done.
For this I need to simplify the geometry so there are no weasel words
allowed. The parallel plates Tom uses, allow much weaseling.
The fight between Bill and Svante was all over such words
For this I will use the geometry of concentric spheres, with
a fixed emissivity over any temperature range used. Such
a sphere is an isotropic radiator with one cross sectional
area that always radiates to 4 pi steradians. No leaks.
So we can tell the direction of thermal flux each sphere
has some thermal conductivity between the inner and
outer surfaces. To be able to measure I suggest the
conductivity to be 9 mW/ cm-degree Celsius.and a
thickness. of 1 mm. I only use degree to indicate
"unit" Kelvin, rather than Kelvin. For radiation and
all thermodynamics, a huge difference in meaning(
(an interval rather than a value)t
Three concentric spheres 6 cm dia, 9 cm dia 12 cm dia.
6 cm has a 5 watt resistive element on the inside surface
the outside of the 6cm inside and outside and the 9 cm
and the inside if the 12 cm are constant 95% emissivity at
all significant wavelengths. each supported by threads
by the next larger sphere the 12 cm sphere outside is
chilled by suitable means to 0 Celsius. (For Kelvin add
273.15) The two inner spheres communicate via radio
waves to indicating inner and outer surface temperatures.
The 6 cm sphere has a battery and control to produce exactly
5 watts of thermal power. switchable via radio control. vacuum
between all shells so no transfer except by thermal radiation.also
with 0 conductive heat transfer by any wires With no power on
all surfaces are a the 0 Celsius ice water bath.
Here is what I claim as a result:
Outer sphere 0 Celsius radiance 0. 0300 watts/sq
cm-steradian
delta T inner to outer +1 degree
9 cm sphere 38 Celsius radiance 0.0497 watts/ sq cm-steradian
delta T inner to outer <+ 2 degree
6 cm sphere 93 Celsius radiance 0.0935 watts/ sq cm-steradian
delta T inner to outer +4 degree.
By the always decreasing temperature to the outside the thermal
flux is always outward. and no power is ever returned "to" a
warmer surface. Each surface takes on only that temperature
required to move 5 Watts outward. This is the "dynamics"
of thermodynamics
5 Watts of power always from resistor to 6 cm sphere conduction
5 Watts of power always from 6cm to 9 cm sphere thermal
radiation
5 Watts of power always from 9cm to 12 cm sphere thermal radiation
5 Watts of power always from 12cm sphere to bath conduction
The 5 Watts is the only power you have and none is returned
Radiance is not radiation . Radiation can only be 5 watts that
is all the heat energy you have. The same is true for the 9 cm
sphere. the 12 cm sphere is the eventual receiver of all 5 watts.
From this the temperatures of each surface can be calculated
How much a lower temperature of the 6cm sphere. if the 9cm
sphere were not there. The 6 cm sphere t cools to 68 Celsius
Is this the weird concept of Greenhouse effect caused by CO2?
It is only geometry. not Greenhouses!
On Earth, there is no downward, "flux",fFrom the atmosphere
only potential downward flux to some instrument at 0 Kelvin