Questions tagged [thermal-conductivity]

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21 views

How to relate cross sectional area to total surface area?

This problem particularly deals with application of Fourier's law of heat conduction.At some point we are to calculate volume to total surface area ratio.However with length of the slab(given as ratio)...
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Would the temperature of a system continue to rise even if I heat it with a constant flame/burner?

For example, suppose I heat water in a vessel that's closed with respect to surroundings, and I keep it on a burner, and continue to heat it for let's say theoretically a very long amount of time. ...
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52 views

Given 2 hot air balloons, one ten times bigger then the other, which one will float for longer, by how much and why? [closed]

We assume that the balloons are perfect spheres. The temperature inside both is $120^\circ \; C$. Ambient temperature is $20^\circ \; C $ and ambient pressure equals the atmospheric pressure. I don't ...
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1answer
74 views

Transient heat conductivity with variable heat flux in 1D

I have a metallic block heated by a heat flux variable in time on one of its faces (let's assume that it is infinite in the other dimensions). I would like to compute the temperature over time at a ...
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2answers
49 views

Confusion about changes in temperature

If two bottles containing hot water are placed in a container for cooling purposes and water at 0 degree Celsius is used, instead of melting ice, the cooling is slower. I get that the ice is taking in ...
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Why isn't the upper disc removed after achieving equilibrium in Lee charlton method?

**The experiment **:- We know in lee charlton's method there are two discs the in between insulating disc results in in a gradient of temperature between the two discs. Now when the insulating ...
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1answer
40 views

Thermal conductivity of metal using kinetic theory of gases model

The first image gives the context about what i am gonna ask. Now in the second image i can understand upto the point where the book talks about kinectic theory in the second paragraph , after i am ...
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Defining energy current in a Normal metal - Superconductor junction

Background Consider a NS-junction modelled by the BdG equation in the seminal paper by Blonder-Tinkham-Klapwijk (G. E. Blonder, M. Tinkham, and T. M. Klapwijk Phys. Rev. B 25, 4515): \begin{equation} ...
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46 views

Method of images for infinite cylinder between two parallel surfaces, one insulating and the other constant temperature

Trying to solve for temperature distribution of a infinite cylinder of radius $R$ of uniform time independent heat generation [$P$] = W$\cdot$m$^{-3}$ suspended between two planes a distance $d$ apart,...
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1answer
41 views

Thermal diffusity. What do I use? [closed]

I'm not a physics expert. Actually don't know much at all but I'm trying to find an answer to a problem. If I had a silicone (or clear vinyl if more appropriate) tube with .25 inch interior ...
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41 views

Rate of conductive heat transfer at a boundary between two different materials

I have one block of material 1, and one block of material 2. They are in contact with each other, sharing an interface of area A. Material 1 behaves as a lumped capacitance, with temperature T1(t). ...
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Thermal conductivity contributions from bosons and fermions

I keep seeing a relation for the thermal conductivity where: κ = α T + β T 3 where the linear term is from fermions while the cubic term is from bosons. Can someone either explain or direct me to a ...
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1answer
31 views

The energy loss cause by Thermal Resistance

The absolute thermal resistance can be expressed in the following formula: $$R = \frac{\Delta T}{P} \left[\frac{K}{W}\right]$$ It shows how big is the temperature difference between two points in ...
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Thermal Conductivity

If we heat a rod of any conducting material by steam, there is heat loss by radiation. But if we heat it electrically, heat loss can be minimized. How?
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10 views

Thermal Resistance of a planar transformer in a multilayer PCB

I wanted to calculate the thermal resistance for the planr transformer which i designed in order to calculate the temprature rise in each board. Accordingly i can design the thermal vias. I was ...
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1answer
47 views

What is the significance of the height of these verical lines in Thermal Conductivity graph?

The following image is from the Wikipedia Article on Thermal Conductivity: Please click here if you want a good image resolution, as I was unable to upload it here due to "Unsupported Image Format". ...
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1answer
36 views

Energy Losses - Hot Water Tanks

In the interest of saving steam and therefore money, can someone clarify if extra energy is required to maintain the temperature of water in an enclosed, vented and insulated tank depending on the ...
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43 views

Thermal resistance calculation

With reference to the given diagram I am asked to find the thermal resistance of the interface(that is the common surface) between 1 and 2.All that I knew was the resistance diagram drawn right below....
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1answer
94 views

Calculation of final temperature [closed]

what would be the final temperature of any body with the change in the ambient temperature? A Body temperature was recorded at 27.2°C ambient temperature is 60.2°C Final temperature of body is 60....
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2answers
68 views

Intuitive understanding of heat conduction equation

$$ k \frac{dT^2}{d^2 x} +heat generation =\rho c \frac{dT} {dt} $$ I find it counter-intuitive that if temperature gradient is linear, temperature won't change with time at a point. I mean if there ...
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37 views

What is the real physical property behind the term “temperature” on macro-level?

Let's assume I have two ideal cubic solid bodies. I place them close to each other, so there is no gap between faces. For simplicity let it be in vacuum. And they will start to interact by exchanging ...
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1answer
113 views

Does changing in exposed surface area affect the temperature change of an object in liquid?

I am doing an experiment regarding heat transfer. I put aluminium pieces of same mass (about 15.3g) but different exposed surface area. To create this, I cut 4 aluminium pieces into same dimension (...
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1answer
77 views

Does a crushed ice cube and a regular ice cube have different potential energies?

For a question on an heat transfer experiment on melting ice cubes in water and measuring the temperature decrease in water, there was a question that asked: Suggest the effect, if any, of crushing ...
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17 views

“Directional” conductivity in linear flux-potential laws?

Question: Has the notion of "directional conductivity" been defined and used in the study of heat flow and electric current flow? Context: The table below gives three laws that describe linear flux-...
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30 views

Is graphene a better thermal conductor than diamond?

I was listening to the BBC Inside Science Podcast episode about artificial diamonds and they mentioned that diamonds are the most thermally conductive material. One of the people on the episode was ...
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2answers
24 views

Influence of pressure on thermal conductivity of water vapour (steam)

I am looking for an analytical correlation of the thermal conductivity of water vapour (steam) in function of pressure. Apparently the effect is not large, but I would like to confirm this by some ...
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1answer
44 views

Can a thermometer be used over the max indicated temperature? [closed]

So I have a thermometer in my film developing tank that is bonded to the inside of the tank and the max temperature is 25degree Celsius. Modern development chemicals must be heated to 38 degrees ...
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1answer
48 views

What is the exact usage of internal heat generation term used in a general heat conduction equation?

∂/∂x (λ ∂T/∂x)+ ∂/∂y (λ ∂T/∂y)+ ∂/∂z (λ ∂T/∂z)+ q_v= ρC_p ∂T/∂t------1 T - Temperature (Temperature of the material) ρ - Density of the material C_p - Specific heat capacity of the material t - ...
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72 views

How do the thermal conductivity and specific heat influence the amount of heat transferred between two objects

Through research on the topic I found that the one with the higher thermal effusivity would be able to transfer more heat. I was wondering what the effect of one material being in liquid state vs ...
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70 views

Calculating heat current through a spherical shell [closed]

I have a spherical shell with inner radius $a$ and outer radius $b>a$. There is a temperature difference of $\Delta T$ between the inner and outer shells. The thermal conductivity is $k$. The ...
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1answer
128 views

Heat transfer through 2 slabs of same material properties, but different thickness

Let'se say we have two walls, wall A and wall B. Both walls are made from the same material, but they differ in thickness. Wall A is L cm, whereas Wall B is L + ΔL cm. Wall A and Wall B make up parts ...
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31 views

why the bulk thermal conductivity of water-saturated soils is higher than that of water and dry soils alone?

According to wikipedia, the thermal conductivity of water is around 0.5-0.6 W·m-1·K-1, depending on the temperature (say 25 degree Celsius is 0.5918 W·m-1·K-1, and the thermal conductivity of dry ...
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28 views

Linear expansion over temperature change

From the equation $\Delta L=aL\Delta T$, $\frac{\Delta L}{\Delta T} = aL$ For small change $\frac{dL}{dT}=aL$ Solving we get $L(T)=e^{aT}$ (as differentiating it with respect to temperature gives $...
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What are ways or methods to calculate or measure the thermal conductivity of a hybrid nanoparticle?

I'm looking for ways of estimating or approximating the value of the thermal conductivity of two nanoparticles added or combined. Creating a hybrid nanoparticle.
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36 views

help: calculating surface temp for rotating planet from solar constant 1366 w/m2

I'm interested in calculating the maximum surface temperature for a rotating planet from the solar constant. I can calculate the solar constant for a planet at any distance from the sun, no problem, ...
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1answer
29 views

How to distinguish the radius from the electrical or thermal resistance? And how to distinguish thermal resistance from electrical resistance?

We know both the electrical resistance and the thermal resistance of a cylinder is inversely proprortional to the square of the radius of the cylinder. But the letters R and r are used sometimes for ...
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1answer
56 views

Why do purely harmonic interatomic interactions result in infinite thermal conductivity?

When interatomic interactions are purely harmonic, normal modes cannot interact, and therefore no phonon scattering occurs, thus resulting in infinite thermal conductivity. But why is anharmonicity ...
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1answer
249 views

How does the thermal conductivity works? What is the significance of thermal conductivity? [closed]

I'm newbie to thermal conductivity. I read an article from https://thermtest.com/what-is-thermal-conductivity that thermal conductivity refers to the ability of a material to transfer heat but I don't ...
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1answer
32 views

An Expression for $\Delta T$ for a Thermal Conductivity derivation

In kinetic theory, the thermal conductivity of a gas is $$K = \frac{1}{3} C vl.$$ In deriving this formula, why is the following equation valid? "Now $ \Delta T$ between the ends of a free path of ...
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63 views

How long does it take a gas to equilibrate with a container's temperature?

Initial Conditions in a vessel: P~my unknown, but ~100torr, V=5000cc, T=35C, gas is 50/50 N2/He Laser drill a hole in the initial volume of diameter=10mils through a chamber wall thickness of 0.75mm. ...
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1answer
26 views

Thermal radiations

everything having temperature above 0 k emits radiation. But those radiations depend upon temperature of the body and not on nature of the body. Why thermal radiations are not material dependent?
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82 views

How much conduction, radiation and convection influence in a thermos flask?

It has been thoroughly repeated that thermos flasks prevent heat loss by minimizing heat conduction, radiation and convection from the bottle to its ambient. This has been answered in this SE. However,...
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1answer
32 views

Copper conductor thermal limitation [closed]

"The maximum permissible current density of copper in open air is approximately 3.1×106 A/m2 of cross-sectional area, above which it begins to heat excessively." I came across the above statement ...
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Why do low concentrations of H2 in He gas exhibit lower thermal conductivity than either?

Thermal conductivity of He+H2 mixtures, as a function of molar concentration of H2, exhibit a minimum at around 14% H2. See Fig. 2 below from "Thermal conductivity of the hydrogen-helium mixture". ...
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233 views

How is the 1D transient heat conduction equation derived? [closed]

From my book: $$\frac{\partial T}{\partial t}=\alpha\frac{\partial^2 T}{\partial^2 t}$$ with an initial condition and boundary conditions $$T(x,0)=T_0$$ $$T(L,t)=T_0$$ $$-k\left.\frac{\...
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Will forcing a gas through an aluminum foam cool or heat it up

Metal foams are known to be porous and interconnected when in open cell form, will forcing a gas stream through the network heat it up due to restrictions and friction or cool it down due to large ...
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51 views

How do I relate phase shift to heat capacity or thermal conductivity for frequency domain thermoreflectance?

I'm trying to measure either thermal conductivity or heat capacity of Silicon devices using frequency domain thermoreflectance (FDTR). I can get phase shift between the incoming signal from pump laser ...
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4answers
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Why don't you get burned by the wood benches in a sauna?

When you go to the sauna you may sit in a room with 90°C+. If it is a "commercial" sauna it will be on for the whole day. How does it come that when you sit on the wood you don't get burned? I ...
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1answer
39 views

Infrared pass material thermal camera

I have a situation in which I need to use a thermal camera in a rain enviroment, the camera is mounted on a gymbal and can rotate 360 degrees, so I tought it may be an option to build a dome in order ...
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2answers
75 views

Doubt in definition of linear thermal expansion

It's stated in my textbook that upon heating a rod , the linear change in its length is directly proportional to its original length and the change in temperature , therefore the equations should look ...

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