Questions tagged [thermal-conductivity]
The thermal conductivity of a material is a measure of its ability to conduct heat.
564
questions
0
votes
1
answer
24
views
Source of light in a heating coil
When we connect a heater coil to an electric circuit then according to "joules law of heating effect" due to its resistance it will produce thermal energy . My question is why light is ...
1
vote
0
answers
22
views
How best to maintain the temperature of a swim spa?
All the advice I have seen on the internet suggests that it is more economical to keep the thermostat of a hot-tub at its intended temperature, rather than turning down the thermostat when the tub is ...
2
votes
2
answers
43
views
Why do most metals have high thermal expansion coefficient although their thermal conductivity are generaly high?
the relationship between thermal conductivity and thermal expansion in metals. Why do most metals have high thermal expansion coefficient although their thermal conductivity are generaly high? Please ...
0
votes
0
answers
15
views
How to add markers to IR photographs
I'm using an IR camera to identify thermal patterns.
The thermal images are similar to this [LINK] image.
I'd like to add markers to the area being measured to determine dimensions and normalize the ...
1
vote
2
answers
53
views
EM energy flux and heat distribution in a cylindrical conductor
Consider a cylindrical conductor made of a single material (say, copper) with conductivity $\sigma$. Assume there is a current through the conductor and, to avoid complications, assume that the ...
0
votes
2
answers
39
views
Is higher or lower specific heat better for cooling an object via contact?
Suppose you want to cool an object by putting it into contact with another object, much colder object, and the transferal of joules to an intermediary equilibrium temperature is instantaneous.
If this ...
-5
votes
2
answers
83
views
Why don't we overheat just by existing? What is the theoretical model? [closed]
Our bodies constantly generate heat, but we don't overheat just by sitting in room temperature! Why?
Something about the shape of our bodies at standard-temperature-pressure is at equilibrium with the ...
3
votes
2
answers
298
views
Does specific heat capacity depend on temperature of the substance?
A substance at 200-degree Celsius is given some amount of heat to raise its temperature by one degree Celsius and the same substance when at -200 degrees Celsius is given some amount of heat to ...
1
vote
1
answer
38
views
What is the relation between phonon anharmonicity and thermal conductivity?
The textbook says that: if the vibration of the lattice were harmonic, then the states of phonons would be orthogonal to each other. As a result, there would be no interaction between phonons, hence ...
1
vote
0
answers
33
views
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
$$ \...
1
vote
1
answer
58
views
Clarification on Searle's method to determine thermal conductivity
Here In Searle's method to determine the thermal conductivity of a good conductor, the heat transfer rate of the conductor along a displacement(thickness) d is given by:
Q1/t=KD(T1-T2)/d.
=>Q1=KD(...
0
votes
0
answers
28
views
Understanding steady state in heat transfer on a molecular level
I am trying to get to a molecular understanding of what happens before a steady state is achieved. I understand that macroscopically, the temperature of any point along the rod won't change when ...
0
votes
1
answer
42
views
Why is heat current same in two different materials connected to each other?
I recently learned in my physics class that the heat current at a boundary between two materials with different thermal conductivities is equal. Why is this so?
When these two materials are not ...
1
vote
2
answers
154
views
Why is heat current constant in a cylinder?
In a hollow cylinder made of some uniform material with thermal conductivity k, length L and inner radius a and outer radius b, the total heat current (dQ/dt) has a constant value in the direction of ...
0
votes
1
answer
25
views
Identical atoms in a potential energy well given heat
When two neutral atoms in the potential energy well are given some amount of heat, why does the distance between them tend to increase? It seems to me from the potential energy versus distance graph ...
1
vote
1
answer
42
views
How to calculate heat dissipation of metal box? [closed]
Lets say I have a steel cubical box of size $1$m filled with water at room ($20$°C) temperature. At first everything in box is $20$°C temperature, and then internal water heater (with power of $10$kW) ...
0
votes
1
answer
41
views
How long does it take specific types of metal to heat up in the sun?
I'm wondering how long it would take different metals -- for the sake of this question I'll say steel -- to heat up in the sun. Assume it was an 80 degree day and a piece of steel was sitting in a ...
0
votes
0
answers
48
views
Defining Temperature [duplicate]
I have learnt the definition of Temperature as
Temperature is defined as the average of Kinetic energy of the particles in the Object.
My doubt is can't we measure the temperature near the sun as ...
0
votes
0
answers
18
views
What would provide greater thermal insulation, a single 1.5 inch thick wool sweater, or 5 thin 0.3inch sweaters layered over each other?
So in this hypothetical,its winter time and your wearing lets say a shirt and a jacket, but inbetween the shirt and jacket you have the option of a sweater. But which layout would result in greater ...
0
votes
1
answer
40
views
Adiabatic Index ($C_{p}/C_{v}$) Through Phase Change
Does the adiabatic index change when a phase change happens?
For example, when we have a compressible liquid (say CO$_{2}$) inside a pipe that goes from high pressure (100 bar) to low pressure (1 bar) ...
0
votes
1
answer
49
views
Thermoelectric Thomson effect as generator
In thomson effect we need an electrical current and a temperature difference at the same time. So it is possible use Thomson effect to generate an electric current? That is, how I generete an electric ...
0
votes
2
answers
72
views
Thermal Conductivity and Specific Heat Capacity: Calculating the Time Required for a Volume of Water to Cool
I'm a chemist by training and have experience solving differential equations, though it has been insufficient in solving the problem I have.
Here is the problem:
I brew my own beer and I'm building a ...
0
votes
2
answers
92
views
Time to heat an object
If I have a sphere of material (radius $= r$ and Temperature $= T_1$) in a hot environment $(T_h)$, how long will it take to heat the object to $T_2$, (where $T_1<T_2<T_h$) through to the centre?...
0
votes
1
answer
54
views
Will stainless steel heat up faster than a cordierite-based surface in a gas oven?
Background:
As some may know, pizza stones, used to accumulate heat before the
pizza dough is put into the oven, are often made of cordierite. If
it's well heated it should provide the underside of ...
0
votes
0
answers
19
views
Gas to solid heating?
I am doing a study on the phenomenon of pyrolysis. This is purely a study of the underlying physics. Generally, in practice, pyrolysis feedstock is heated conductively but we are examining the energy ...
0
votes
1
answer
51
views
Is the heat flow $\dot{Q}$ in a series system is same for all its constituent parts? Question is wrong
Question is wrong. You can close it.
Actually I was learning about the conduction method of heat transfer. I found that there is thermal resistance for a system which can either be series or parallel. ...
1
vote
0
answers
31
views
Why is my max heat transfer lower than the actual heat transfer value (NTU-method)? Heat exchanger effectiveness is greater than 1 [closed]
I am using the NTU-method to calculate the effectiveness of a heat exchanger.
The fluids are water (cold) and ethylene (hot).
So far I got:
$$
C_h = c_{p,h} \cdot m_h = 42.9\frac{kJ}{kgK} \cdot 44.4\...
1
vote
0
answers
24
views
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 ...
1
vote
0
answers
17
views
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 ...
0
votes
0
answers
18
views
Thermal boundary layer of an inviscid fluid
We know that an inviscid fluid flowing along a flat plate doesn't develop a hydrodynamic boundary layer because there is no friction.
we also know that viscosity is caused by intermolecular forces and ...
0
votes
0
answers
25
views
Thermal mass flow meter
I am trying to build a thermal mass flowmeter, but I am facing some challenges describing it theoretically. I have an aluminium pipe with a heating element. I am measuring the temperatures of the pipe ...
0
votes
1
answer
25
views
Doubt regarding thermal conduction in series combination
How is the rate of heat flow same in both conductors when the thermal conductivity constant is different for both conductors?I have seen this everywhere and have been confused regarding this
0
votes
0
answers
45
views
Confusion regarding effects of changing any mass in Principle of Equilibrium of Mixtures/Principle of Calorimetry
My book says that a calorimeter is made of thin copper sheets, and the thinner the better since less mass means less heat capacity, which means for the same temperature change, less heat is required ...
0
votes
1
answer
82
views
Why is cup containing coffee hot?
It happened that I was having my coffee and saw this video at the same time. It's an interview given by RP.Feynamn. In that Feynman explains about why is a cup containing coffee hot, he says that as ...
4
votes
7
answers
196
views
Speed of heat through an object
According to the Heat equation (the PDE), heat can travel infinitely fast, which doesn't seem right to me. So I was wondering, at what speed does heat actually propogate through an object?
For example,...
1
vote
1
answer
43
views
Is thermal conductivity additive?
Suppose I have water in a beaker. I measured, its thermal conductivity by some means to be $\kappa_0$. Next, I added some salt to it so that it dissociate from it. Say,
$$AB\rightarrow A^++B^-$$
Now, ...
1
vote
2
answers
101
views
In case of heat transfer in a rod, why actually steady state occurs after a time (why sections of rod cant further absorb heat)?
In heat transfer across a rod, why actually steady state occur?
why temperature of sections of rod don't further increase as heat is even flowing through them and as whole rod is of same material then ...
1
vote
2
answers
54
views
Possibility of combining photovoltaics and solar thermal energy
In a private setting, photovoltaics and solar thermal energy are often harvested on the home's roof and roof area is limited. So, I thought about combining both, i.e. mounting solar collectors ...
0
votes
1
answer
62
views
Help regarding discovery question in Thermodynamics
new to the forum and I'm currently learning about "heat capacity" in my physics book, and I've had a bit of a tough time trying to see the reasoning behind a certain question. In this book, ...
0
votes
0
answers
26
views
Drude theory for liquids
Suppose a compound AB that dissociates into A$^+$ and B$^-$ when dissolve into water. If we suppose that the Drude theory is valid with the same assumptions. Then we can write the conductivity as
$$\...
1
vote
2
answers
102
views
Why does the steady state exist In thermal conduction?
In thermal conduction,why doesn't transient state go on continuously,why does steady state exist?why after some considerable time A metal bar sttached to a sink and source comes to steady state where ...
1
vote
0
answers
31
views
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 ...
3
votes
2
answers
56
views
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 ...
56
votes
4
answers
4k
views
Does anything in an incandescent bulb actually reach its color temperature (say 2700 K)?
This question is inspired by a question about oven lightbulbs over on the DIY stack. It spawned a lengthy comment discussion about whether an incandescent lightbulb with a color temperature of 2500 K ...
0
votes
0
answers
114
views
1D Heat Equation with different materials
I'm trying to solve a 1D-Heat Equation with Finite Difference Method in python.
The object I'm trying to depict has "Material A" with a high conductivity on the outside and a core of "...
0
votes
0
answers
5
views
Does boundary layers between two metals decrease thermal transfer rate?
Assuming perfect contact, does layering different metals decrease thermal transfer rate?
I initially thought that since the two metals were in perfect contact, then the boundary between the two metals ...
0
votes
1
answer
26
views
Heat transfer from stovetop through heated water to air [closed]
This is a question about efficiency.
My understanding is that resistive heating is very efficient. So if I turn on an electric burner on the stove, once the stove+stovetop equalizes, radiation into ...
1
vote
2
answers
47
views
Is there a name for the type of boundary condition where the initial boundary values are known but are not held constant over time?
I'm exploring the heat equation to model a particular 1D scenario, and I understood the Dirichlet and Neumann boundary conditions, but neither are sufficient for my scenario. Assuming a rod of length ...
0
votes
0
answers
23
views
How do we justify the equation of heat current through a perpendicular cross section?
Fourier's equation for heat flow:
$$ \frac{dQ}{dt} =-KA\frac{dT}{dx} $$
is usually derived by quoting its similarity with electric current and comparing variables to arrive at a similar equation. ...
2
votes
1
answer
29
views
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 ...