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Questions tagged [radiative-transfer]

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Why is the temperature of electron-proton recombination obtained from Saha equation so small?

I read a blog about the temperature of the Universe at recombination phase. The ionization potential of a hydrogen atom is $13.6\, eV$, throw it into the thermal energy equation $E=\frac{3}{2}kT$, ...
Halcyon Mo's user avatar
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Can radiative transfer theory be used to calculate an effective index of refraction?

As I understand it, the (real) index of refraction is given by the ratio of speed of a monochromatic light wave in vacuo versus speed in medium. When it comes to the question of propagation of a light ...
roland's user avatar
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1 answer
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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} \...
mwoods's user avatar
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21 votes
6 answers
5k views

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 ...
katefull06's user avatar
1 vote
0 answers
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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 ...
pretzlstyle's user avatar
1 vote
1 answer
45 views

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 (...
pretzlstyle's user avatar
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1 answer
32 views

How radiative heating of a gas should scale with gas density [closed]

Let's say I have a gas in a fixed volume being heated by a uniform, monochromatic light source. I'd like to know how the radiative heating rate per unit mass of the gas in J/kg/s scales with the ...
pretzlstyle's user avatar
1 vote
1 answer
75 views

How can I determine how much energy a sensor pixel can withstand before exploding? [closed]

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 ...
Benzene enthusiast's user avatar
1 vote
2 answers
59 views

What is the ideal amount of shade for a house with air conditioning and solar cells on the roof? [closed]

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 ...
SarahJuliet1510's user avatar
2 votes
3 answers
137 views

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 ...
electronpusher's user avatar
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1 answer
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How do I understand the time evolution of gas temperature in this paper?

I am reading this paper Title: "Radiative transfer through Galactic medium" I am having some problems with equation $(8)$: $$\frac{dT}{dt}=\frac{2(G-L)}{3kn}+\frac Tn\frac{dn_e}{dt}-3\frac{\...
Sophus's user avatar
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2 votes
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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{\...
Chris K.'s user avatar
1 vote
1 answer
216 views

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 ...
Emerson's user avatar
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1 answer
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Net flux in radiative transfer

I encountered the need of computing the net flux of a specific intensity given by $$I_{ex}(\theta,\phi) = I_0 \delta(\theta) \delta(\phi)$$ traversing an horizontal plane whose normal coincides with ...
Lorenzo Eboli's user avatar
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1 answer
22 views

Change of intensity along path element - plane-parallel geometry

How to derive this formula, please? Why is it true? $\mu$ is an emission coefficient
Elena Greg's user avatar
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2 answers
322 views

Challenge: How can this meta-material be in thermal equilibrium?

The following simple ideal device comprises just two objects radiating at each other with a radiant concentrator in between. As far as I can tell, this device can't be in thermal equilibrium AND be at ...
Will Temple's user avatar
1 vote
0 answers
28 views

Brightness Temperature layered atmosphere

I'm trying to figure out how to apply the radiative transfer model to calculate the brightness temperature Tb in microwave (Rayleigh–Jeans approximation) considering atmosphere and no scattering. If I ...
Rick's user avatar
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2 votes
1 answer
150 views

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)=\...
MrDerDart's user avatar
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1 vote
1 answer
139 views

Calculating pressure and flux tensors in radiative astrophysics

I need to calculate the components of the radiative flux tensor and the pressure tensor, but I am having a little trouble figuring out what the integral should be. The flux is defined as $$F_v = 4{\pi}...
philosophytophysics's user avatar
2 votes
1 answer
144 views

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}} = - \...
The Pointer's user avatar
-2 votes
2 answers
266 views

What is the solid angle $d\Omega$ in radiative transfer?

The Wikipedia article for radiative transfer gives the following definition: In terms of the spectral radiance, $I_{\nu }$, the energy flowing across an area element of area $da$, located at $\mathbf{...
The Pointer's user avatar
0 votes
1 answer
154 views

Difference between stationary and non-stationary radiative transfer?

I am currently studying radiative transfer. In researching this subject, I found that there is stationary radiative transfer and non-stationary radiative transfer. However, it is not clear what the ...
The Pointer's user avatar
0 votes
1 answer
181 views

How does radiation heating work at the fundamental level?

I was thinking something Let's consider radiation incident on a gas If it were a bunch of electrons in place of photons, then incident electrons would increase the kinetic energy of each and every ...
Souparna Nath's user avatar
1 vote
2 answers
237 views

What would be a beginner's book on radiative transfer?

I want to learn the basics of radiative transfer for my reasearch, which is on planetary sciences. I am looking for a book that would give me the basics of radiative transfer (the mathematics involved)...
0 votes
1 answer
188 views

Temperature rise due to thermal radiation? [closed]

Consider a cylindrical metal rod of a certain diameter and length and a rectangular plastic plate of certain dimensions. The rod is suspended in air above the plate at a certain distance from the ...
Somanna's user avatar
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0 votes
1 answer
257 views

Melting plastic with radiant heat? [closed]

I want to melt a bed of plastic powder so that the powder bed once melted then cooled form a solid sheet of plastic. In order to melt the powder I thinking of passing a nichrome (Ni80/Cr20) wire over ...
Somanna's user avatar
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1 vote
0 answers
37 views

optical thickness of a supernova [closed]

I need to explain this question to a bunch of students tomorrow and I am not 100% sure how to solve it myself..Help would be much appreciated. The question is. If a Classical Nova ejects $10^{−5}$ ...
Coolcrab's user avatar
  • 215
6 votes
3 answers
639 views

Shouldn't $CO_2$ forcing depend on the surface temperature?

When I read about radiative forcing due to CO2 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-...
Livid's user avatar
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0 answers
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How many scattering events happen in the atmosphere over 1 km?

In Vector Monte Carlo Atmospheric Radiative Transfer Simulations, they take a Stokes vector, let's say [1,1,0,0] and multiply it with a matrix, with elements close to 1. But if there are much ...
Gregonymus's user avatar
2 votes
2 answers
810 views

Why the source function is equal to Planck function when we have a local thermodynamic equilibrium? [duplicate]

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 (...
Marios K.'s user avatar
2 votes
0 answers
358 views

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 ...
D Young's user avatar
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