Questions tagged [radiative-transfer]
31 questions
21
votes
6 answers
How does fire heat air?
I understand that fire heats its surroundings via conduction, convection and radiation. I've read that conduction is nearly irrelevant to this process as air is a poor heat conductor. In descriptions of convection, people often just say "fire heats…
katefull06
- 313
7
votes
3 answers
Shouldn't $\mathrm{CO}_2$ forcing depend on the surface temperature?
When I read about radiative forcing due to $\mathrm{CO}_2$ it says:
"Radiative forcing is a measure of the influence a factor has in
altering the balance of incoming and outgoing energy in the
Earth-atmosphere system and is an index of the…
Livid
- 1,096
2
votes
3 answers
Is thermal conduction really radiation?
I have no doubt thermal conduction is a useful model for heat transfer, wherein kinetic energy is transferred between particles when they collide. However, according to explanations that I believe are canonical, two molecules collide due to…
electronpusher
- 1,236
- 1
- 9
- 14
2
votes
0 answers
What are those weird flux-like quantities ($N$-notation?) I see in astrophysics papers?
I have been reading some astrophysics papers on Fermi Bubbles and in a lot of them, diagrams depicting SEDs use a weird $ E^2 \, \frac{\text{d}N}{\text{d}E} $ quantity, in units of $ \left[ \frac{\text{eV}}{\text{cm}^2 \, \text{s} \, \text{sr}}…
Chris K.
- 39
- 2
2
votes
1 answer
Radiative transfer equation for a three-level system
I am trying to derive the radiative transfer equation for a three-level system, which is supposed to be given by:
$\frac{dI(\omega,x)}{dx}+N [\alpha\rho_{11}-\beta( \rho_{22}+\rho_{33})]I(\omega,x)=\beta(\rho_{22}+\rho_{33})$,
where $I(\omega,x)$ is…
MrDerDart
- 292
2
votes
1 answer
Stationary equation of radiation transfer: Which one is correct?
I am currently studying radiative transfer. I have seen the stationary equation of radiative transfer written in two different ways:
1.$$\dfrac{\partial{I}(\mathbf{r}, \mathbf{s})}{\partial{s}} = - \mu_t I(\mathbf{r}, \mathbf{s}) + \dfrac{\mu_s}{4…
The Pointer
- 939
2
votes
2 answers
Why the source function is equal to Planck function when we have a local thermodynamic equilibrium?
I understand that the source function $ S_λ $ for the special case of blackbody radiation is equal to the Planck function $B_λ $.
However, in the broader case of a local thermodynamic equilibrium (and not the special case of a blackbody) I would…
Marios K.
- 21
2
votes
0 answers
Heat transfer on Mars
SCENARIO:
I have been tasked with finding the heat transfer across a composite wall on Mars.
On the left of the wall there is air maintained at Earth atmospheric conditions and room temperature (101 KPa, $21^\circ C$). On the right there is Martian…
D Young
- 21
1
vote
0 answers
Behavior of Radiative Transfer in Homogeneous Plane-Parallel Scattering Media
Coakley and Chylek (1975) provide a formulation of the plane-parallel equation of radiative transfer:
$$
\mu \frac{dI^{+}(\tau,\mu)}{d\tau}
= I^{+}(\tau,\mu)
- \frac{1}{2} \int_{0}^{1} d\mu'\, p(\mu,\mu') I^{+}(\tau,\mu')
- \frac{1}{2} \int_{0}^{1}…
Phoenix
- 11
- 3
1
vote
1 answer
What is the Beer's law energy density in spherical symmetry?
The radiative transfer equation in 1D spherical coordinates without emission and scattering and a homogeneous medium is given by
$$+\mu \frac{\partial I(r, +\mu)}{\partial r} + \frac{1 - \mu^2}{r} \frac{\partial I(r, +\mu)}{\partial \mu} + \rho…
mwoods
- 11
- 4
1
vote
0 answers
How do surface temperatures drop in response to optical depth?
I'm trying to come up with a super simple estimate for how atmospheric surface temperatures would be affected by a substance overhead with some optical depth $\tau$. I'll assume that the sun is always directly overhead, and that the parallel-plane…
pretzlstyle
- 129
1
vote
1 answer
How does a volcanic eruption cool the planet's surface?
For example, after the eruption of Mt. Pinatubo in 1991 according to this paper,
The introduction of large amounts of sulphuric acid aerosol into the stratosphere increases the planetary albedo (essentially the Earth's reflectivity of solar…
pretzlstyle
- 129
1
vote
1 answer
How can I determine how much energy a sensor pixel can withstand before exploding?
I am trying to design a camera system to image a laser beam. I know the sensor is a Sony IMX226, and I have the data sheet for this sensor. The data sheet, however, does not list a maximum energy threshold for the sensor. It does give a decibel…
1
vote
2 answers
What is the ideal amount of shade for a house with air conditioning and solar cells on the roof?
Considering a mid latitude (e.g. in Virginia), south facing, single family house with two stories, AC cooling and solar power on the roof:
What would be the ideal level / amount of shade for the house in summer?
An additional condition is that the…
1
vote
1 answer
Kirchhoff's Law of Thermal Radiation - When is a (radiative) process in thermodynamic equilibrium?
I'm very confused/struggling to understand the scope of Kirchhoff's law of radiation, put simply my understanding of the law is
\begin{gather}
\varepsilon = a
\end{gather}
where $\varepsilon$ is the emissivity of the material, and $a$ is the…
Emerson
- 205