Questions tagged [thermal-conduction]
The thermal-conduction tag has no usage guidance.
232
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Wiedemann-Franz law
The Wiedemann-Franz law states that the ratio of thermal conductivity $\kappa$ and electrical conductivity $\sigma$ for metals fairly accurately obeys $\kappa/\sigma = LT$, where $T$ is the ...
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Why is thermal conductivity of a gas higher than one would think from diffusion coefficient
When we study kinetic theory of gases we find relationships between the processes of diffusion, heat conduction and viscosity, and collisions in the gas. In particular the diffusion coefficient is ...
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Temperature distribution in a current carrying conductor
A rod of uniform cross section and composition is connected across a battery. Let the middle part of the rod(when divided into three equal parts) is heated uniformly.
A book says that the temperature ...
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Calculating new temperature of an object when air temperature changes
I'm trying to calculate the new temperature of an object when the air temperature around it changes, given a period of time.
Basically I get periodic readings from an air temperature sensor in a ...
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Dimension reducing of heat equation 2D problem
I have two metal objects of different thickness and conductivity:
1) thicker, but poorly conductive. It's properties: $k_1, H$
2) thin and much better conductive. It's properties: $k_2, h$
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Time to reach steady state in transient 1-D heat conduction
Suppose that there is a slab with thickness $2L$ and other dimensions of the slab are very bigger than $L$. Both sides of the slab are kept in the constant temperature $T_0$. In time $t=0$ a heat ...
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With what speed does a thermal front travel through a solid?
The heat equation provides theoretical temperature distributions as a function of space and time. Take for example an infinitely long rod that is suddenly heated up at $t = 0$ at its end $x = 0$. The ...
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conduction through solids
How is heat transferred through two separate bodies which are in contact. The collision of the lattices of atoms of the two bodies is a good answer but if there is a net energy transfer then shouldn't ...
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Is stoßlüften - quick exchange of air through windows actually more efficient than slow exchange through a wall ventilation fan?
In German areas with near air-tight homes, it is recommended that full house ventilation is performed by stoßlüften - opening windows fully to exchange as much air as possible in shortest amount of ...
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In kinetic theory of gases, in finding connection between pressure and molecular kin. energy, why $N/2$ & not $N/6$ molecules are assumed to hit wall?
In my book While driving a relation between pressure and average kinetic energy of a single molecule [i.e. $P = (Nmv^2)/2$ ], an ideal gas of $N$ molecules is assumed to be enclosed in a cubical box ...
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Heat resistance of sphere
I have been taught that the heat resistance of a hollow cylinder is
R(hollow cylinder) is proportional to ln(outer radius/inner radius)
It was assumed in the derivation that the inner surface is at ...
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How can you determine how fast (m/s) heat will travel through a material being heated on one end?
I was wondering how fast heat will travel through rectangular glass bottle, heated on a tray under vacuum.
I work in a lab where an inert atmosphere glovebox is used, and when moving glass bottles ...
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What does it mean for resistance, as it appears in Ohm's law, to be an integral, evaluated over the body as a whole?
In literature I read:
The three linear flux laws mentioned are:
As seen, a correspondence exist between the hydraulic conductivity $K$, thermal conductivity $\lambda$, and electrical conductivity $\...
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Does the Mpemba Effect affect none-water substances?
Does the Mpemba Effect work on liquids other than water? If so, what are the similarities/differences, and what contributes to it(mainly the differences)?
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Thermal physics of cooking with an electric stove
I'm wondering why stoves have a 1-9 scale of the amount of heat and a not temperature scale.
My understanding is that for each of the modes corresponding to a number, a certain amount of heat is ...
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Does heat flow always in the direction of maximum decrease?
I was wondering if at a given gradient temperature heat could flow in any direction satisfying moving from a higher to a lower temperature. Or it can only flow in the direction of gradient? Consider a ...
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Proportion of heat or energy passing through a window by radiation vs conduction
I'm trying to understand how modern window films or coating (so-called "Low-E" coatings) can improve the "R" value of the window just by reflecting internal room radiant energy (presumably long-wave ...
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How would one calculate the time it takes for an object immersed in liquid nitrogen to reach a specific temperature?
I have an aluminium object which will be immersed in liquid nitrogen for a specified amount of time. I would like to know, if the object is initially at room temperature, how long it would take for it ...
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Vapor pressure of sublimating ice in vacuum
I am trying to find a vapor pressure of sublimating ice as a function of thermal energy being absorbed by ice. Basically, I am starting with a sample of ice (t=200K) in a vacuum. From there, I am ...
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What is the physical limit of thermal insulation?
If we consider a container (at very low) temperature $T_0$ surrounded by some passive structure, in turn surrounded by an environment at temperature $T_1>T_0$, there will be an inward heat flow ...
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Neumann boundary condition for Laplace's equation in 2D axisymmetric coordinates?
I have the Laplace's equation, say, describing the density $\rho(r,z)$ distribution in a 2D axisymmetric coordinate:
$$\nabla^2 \rho=\frac{1}{r}\frac{\partial}{\partial r}\left(r\frac{\partial \rho}{\...
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At the lambda point, why does specific heat capacity tend to infinity?
The specific heat capacity is the energy required to raise the temperature of unity mass by 1K, if at the lambda point all the bosons occupy the lowest quantum state, shouldn’t the specific heat ...
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Is my method of calculating thermal conductivity of a metal wrong?
I am trying to determine the thermal conductivity of pure copper at various temperatures using the Weidemann-Franz Law but for some reason it is not matching up to textbook data. I used the Bloch ...
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In a non-degenerate plasma, why are e-e collision negligible compared to e-ion for thermal conduction?
I'm trying to make some order of magnitude estimates of heat transfer in stars - to better understand 1) why conduction is said to be negligible (for non-degenerate matter) and 2) when convection ...
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How does white powder coat change aluminum emissivity?
I have a telescope with an aluminum tube powder coated white. I took 940 temperature data points from a temp sensor attached to the tube and a weather station for ambient temperature.
It seems the ...
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Temperature Estimation for Insulated Bottom Surface in Water Cooling
In a 2D plane heat flux q'' is incident on an insulation layer (which has a thickness L and a thermal conductivity k). The bottom surface of this insulation layer is exposed to water cooling with a ...
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At temperature $T>0K$, are all normal vibrational modes present simultaneously in a one-dimensional solid?
I am studying Debye theory of Specific heat.
hyperphysics has this picture and there it says
"Considering a solid to be a periodic array of mass points, there are constraints on both the minimum ...
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Is it possible for an absorption refrigerator to pump heat to a reservoir that is at a higher temperature than the heat source used to run it?
Judging by the wiki page I get the feeling that this type of heat pump would not function if it's radiator were hotter than the heat source, but I can't quite put into words why and I feel like there ...
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Why do we move the spoon in a plate to cool it down?
Say we have a plate full of soup, why to cool it down we move the spoon around in the plate? Is it to facilitate the thermal interchange between the air and the soup? Also why is the edge of the plate ...
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Why does a baking tray sometimes warp in the oven, but a frying pan never does on the stove?
I can take a thick case iron frying pan and heat it on the stove until oil smokes. I do this regularly to season it. The heat is high. Temperature gradients are high. But the frying pan never warps.
...
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Simulating Dirichlet Boundary Conditions for Lattice Boltzmann Method
So, I'm going through A.A. Mohammad's book "Lattice Boltzmann Method : Fundamentals and Engineering Applications with Computer Codes." And I'm currently coding the D2Q9 lattice with respect ...
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What is the formula for heat transfer for a cup?
I am doing an experiment to see how does the thickness of the cup affect its heat transfer.
I need to find a theoretical equation that shows me the amount of heat transfer in a certain time for the ...
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Cryostage solid state active insulation
I am designing an ultra-high vacuum cryostage for a fluorescence microscope. The cold finger is cooled by a closed loop liquid nitrogen system. The base of the stage is maintained at room temp with ...
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Is the Schrödinger equation the heat equation with imaginary constants?
Playing around with the Schrödinger equation, I separated the time partial derivative this way:
$$\frac{\partial \Psi}{\partial t}=\frac{i\hbar}{2m}\frac{\partial^2\Psi}{\partial x^2}-\frac{i}{\hbar}V\...
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Quantum effects on phonon transport?
Phonons are the quanta of vibrations in a crystal lattice. As the name suggest, phonons are already a quantum phenomena but when studying heat transfer the phonons are mostly very classical (wave ...
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Heat conduction across 2 solids with large thermal condcutivity difference
I am solving a transient heat condcution problem involving 2 solids using implicit finite difference method.
At the interface, I soppose the finite difference equation at the interface should be
$$ \...
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How can I model convection in a simple and effective way?
I have a project in which we're trying to model heating of a room. We are modelling the room in 3D. The room has realistic walls, windows and a door, which will loose heat through them. To balance the ...
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Do inviscid fluids have thermal conductivity?
Inviscid fluids are an idealization and they don't have viscosity. The no-slip boundary condition DOESN'T apply to them and consequently, these fluids won't display a hydrodynamic boundary layer.
I've ...
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Prigogine vs. Bronsted and the minimum entropy production principle
I apologize for the length of this question.
Prigogine's minimum entropy production principle fails in the simplest heat conduction case, because the temperature distribution that minimizes the ...
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How to derive specific heat of a crystalline material from phonon density of states?
I have done a simulation of a crystalline material using DFT and have extracted its normal modes and its phonon density of states.
Does anyone have an algorithm/code or a detailed resource that can ...
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Does rate of latent heat transfer of steam to another fluid increase with increasing temperature?
I know rate of sensible heat transfer is dependent on temperature difference, but I haven't found much information on the rate of latent heat transfer of steam with respect to temperature. Take, for ...
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Planck radiation law of a dielectric layer
Suppose we have a rectangular slab of thickness $h$, width $a$ and length $b$. The upper surface of the slab is put at constant temperature $T$ while all the rest is at initial temperature $T_0$. ...
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Thermal Conductivity of a Harmonic Lattice
I have been trying to compute the conductivity using the Green-Kubo formula obtained from molecular dynamics simulations. I used a square lattice and a harmonic
potential and I consistently get a ...
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Heating a rod of any material at one end without losing heat to the surrounding
I am interested in learning about heat flow but I am a noob.
Suppose there is a rod of finite length that can conduct heat. Suppose we always keep one end of the rod at a temperature say $u$. Will the ...
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Heat Conduction in Deformed Solids
I am working on a model for isotropic elastic solids and have to make a decision about whether heat conduction should be isotropic in the reference or deformed configuration.
I have spoken to two ...
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