Questions tagged [heat-conduction]

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32 views

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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1answer
45 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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The thickness of the hot air layer above a hot metal

I need a simple way to estimate the thickness of the hot air layer above a metal heated up by about 100K above the room temperature. I'm not sure how to go about estimating this. What happens there, ...
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6 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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Software to simulate molten salt flow and thermodynamic operations

I was curious if there was any software (preferably in C++, Java, and/or python) that could be used to simulate the following: Heat capacity of a fluid Heat transfer through a liquid and a solid ...
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35 views

(Finite Element Method) Zero thermal conductivity and Non-zero convection boundary condition

I asked this same question in Computational Science Stack but no one proved it mathematically (see the link below). Link of original question: https://scicomp.stackexchange.com/questions/32959/fem-1d-...
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1answer
53 views

How is heat propagation a semi-deterministic process?

Arnol’d in his Ordinary Differential Equations, states that The propagation of heat is a semideterministic process: the future is determined by the present but the past is not. How is this so? If ...
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1answer
50 views

Will increase in flow rate increase the rate of cooling down?

Suppose a hot body is surrounded by a coil of very good thermally conducting pipe with cold water flowing inside which comes at a certain fixed low temperature in the pipe and leaves at some higher ...
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26 views

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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1answer
68 views

General relativistic heat conduction equation

I read this wikipedia article https://en.wikipedia.org/wiki/Relativistic_heat_conduction It mentions the relativistic heat conduction equation: $$\frac{\partial \theta}{\partial t}=\Box\, \theta$$ ...
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2answers
75 views

Can thick fur isolate against heat?

I started writing this question on pet.SE but realised after a while that I think it has more to do with physics than pets but if some admin disagrees, please move it back to pets. I have heard ...
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3answers
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Conduction, convection, radiation: Does evaporation count as one of those?

The forms of heat transfer are traditionally described as conduction, convection, and radiation. Is evaporation (or any other change of state) counted as one of those forms? Or is it considered its ...
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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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Minimum Wall Thickness Heat Transfer

We are asked to find the minimum wall thickness of a composite wall given an inside wall temperature $T_i$ and outside wall temperature $T_o$. Also we are given three types of bricks $A, B, C$ with ...
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9k views

Why does wrapping aluminium foil around my food help it keep warm, even though aluminium is a good conductor?

Aluminium being such a good conductor, how is it possible that it is helping me keep my food warm ?? Because ultimately it should conduct the heat that is inside to the outside for exchange and ...
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38 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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21 views

can low pressure systems act as coolants

I apologise if this is the incorrect way of wording this question but I was wondering about whether for example, a container with very low pressure could cool down its surroundings?
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104 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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1answer
27 views

What are the heat equation boundary conditions with heating?

I'm trying to figure out how to do a simplified model of heat flow through a wall when the wall is also sunlit. The simplified model is a 1-dimensional heat equation, $$\frac{\partial T}{\partial t} = ...
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2answers
33 views

A heat flow generalized problem featuring light bulb and oven

If an incandescent light bulb under constant power is taken from room temperature 25 deg C to an oven at 75 deg C, does the filament temperature increase by 50 C? Assume radiated power is negligible ...
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9 views

Is there an electronic version of diffuse mismatch model for metal-metal contact thermal resistance?

Interfacial heat transport in phonon systems is routinely described by diffuse mismatch model for phonons. Has anyone come across a similar model to describe interfacial heat transport in electron ...
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1answer
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What happens when two bar of different material are joined and their opposite ends are heated to same temperature. How would the heat transfer work?

Imagine two bar, one of copper and another of steel of same length and cross section are joined together end to end. Now the bars are insulated except the end such that no other forms of heat transfer ...
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3answers
54 views

Thermal Energy in a Conductor

We know that thermal energy developed in a current-carrying resistor is given by $U=I^2Rt$ and also $U=VIt$. So my question is- Should we say that $U$ is proportional to $I$ or $I^2$
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How does the change in entropy of the universe vary as water is heated in different increments

I get the same answers for 2 parts of a question that I think should be different. The question is... If 0 $^{\circ}$ C water is heated by a 100 $^{\circ}$ C reservoir to thermal equilibrium, what is ...
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1answer
25 views

Why does the bottom in contact with surface sweat more?

It is summer, I have noticed that when I am sitting, my bottom which is contact with the chair sweats the most. Why does that happen? I think it might be because of friction, but I don't move alot ...
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1answer
59 views

Calculating the temperature of flowing gas in copper tube

A copper coil is immersed in a water bath. The water bath provides heat to heat the nitrogen gas when it passes through the copper coil. Nitrogen gas at room temperature is passed through the copper ...
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53 views

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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34 views

How to calculate total heat energy with fluctuating temperatures?

I had a question relating to a math problem that I'm doing. Let's say I have a heater that produces heat until it reaches a specific temperature, after which it turns off until it reaches a minimum ...
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2answers
49 views

How to determine the temperture inside a pipe knowing the temperature outside?

I would like to know if there is a way to determine using calculation the inner wall temperature of a pipe which has a steady flow of water through it knowing the temperature measured on the surface ...
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1answer
52 views

thermodynamics problem about thickness of ice

the problem is outside temperature is -10 C and on the lake there is 5 cm of ice. After what time will 15 cm be reached. $Q=\frac{kA(T_2-T_1)}{H}$, where $A$ is area, $H$ thickness of ice, $T$ ...
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1answer
33 views

Will a box with black or mirror lining have a higher temperature?

Imagine having two boxes side by side out in the sun. Both boxes have cardboard as the floor and side surfaces. The top surface of the box is a piece of glass to allow in heat and insulate it. Each ...
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1answer
31 views

Clarification on the three omega method for measuring thermal conductivity

I've recently come across the $3\omega$-method for measuring thermal conductivity in materials. Now I'm told that we use a lock-in amplifier to measure the 3rd harmonic in the voltage across the metal ...
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1answer
34 views

Equation for simultaneous cooling and conduction

Imagine a long, uniform metal rod placed on the positive $x$-axis being heated with a power $P$ from its end at $x=0$. It is cylindrical in shape and the cross-section is a circle of radius $r$. ...
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1answer
20 views

From Boltzmann transport equation to fouriers law - infinite speed of propagation of information

The macroscopic Fourier's law can be derived from the Boltzmann transport equation using the relaxation time approximation for the collision integral. This is demonstrated for an ideal gas in this ...
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A problem in heat conduction at a steady state

Question : Three rods of identical cross-sectional area and made from the same metal form the sides of an isosceles triangle $\triangle ABC$, right angled at $B$. The points $A$ and $B$ are ...
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1answer
149 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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1answer
52 views

Conductive heat transfer water through concrete to water

So I've been asked to do a calculation on heat loss from a floating swimming pool. Strange and not something you're likely to come across on an everyday basis. I have already calculated the ...
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0answers
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Dependence of heat transfer rate on acoustic boundary layer thickness

I have generated a sine wave acoustic signal of constant amplitude and different frequency (i.e. 50Hz to 250Hz). At low frequency i am getting higher evaporation rate. However, at low frequency ...
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2answers
160 views

Should I walk or run to my towel when naked and wet? [closed]

This morning when I got out of the shower, I realised I had left my towel in the bedroom. Naked and wet I ran as fast as I could to get the towel. On my way back I didn't run, but rather walked, and ...
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4answers
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What is heat and heat transfer?

Physics books write that heat is the transfer of thermal energy. They also write that heat transfer is the transfer of thermal energy from a thermodynamic system of high temperature to a one of lower ...
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1answer
52 views

Why no heat is absorbed by the conductor in steady state

Why is it that no heat flowing through the conductor is absorbed by any cross section when the conductor is in a steady state , there was a question on PSE about the same concept , but the answers ...
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2answers
71 views

What boundary conditions does a steady state initial temperature profile that evolves according to the heat flow equation obey?

A cylindrical rod of length $L$ is insulated over its curved surface. The end of the rod at $x = 0$ is in contact with a heat bath at temperature $\Theta_0$ and the end of the rod at $x = L$ is in ...
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1answer
107 views

How to develop a model for cooling rate of steel tube in air?

I am trying to develop an equation to determine the cooling rate of a steel tube in air. I'm using Fourier's Law, Stefan-Boltzman Law, Newton's Law as well as the specific heat capacity equation. The ...
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1answer
42 views

Heat equation volume source vs. heat flux boundary condition

I want to solve the heat equation in the 3D unit sphere $B$ with a general heat flux boundary condition, no volume sources and some given constant initial temperature: $$ \rho c_p\partial_t T - \...
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1answer
298 views

What does the area under the curve of a temperature-time graph represent?

I’m trying to calculate the total heat produced by a system over a period of time and I’ve gotten a regression line of y= log x to represent the best produced by the system. To calculate the total ...
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Microscopic level - What happen to the particles in a heat transfer through conduction?

So on a macroscopic level, there is physical contact and the heat energy is being transferred from the higher temp. to lower temp. But what about in a microscopic level, whats going on? As far as i ...
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What do you mean by infinite thermal conductivity? How is the temperature constant when the thermal conductivity is infinite?

What do you mean by infinite thermal conductivity? How is the temperature constant when the thermal conductivity is infinite?
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123 views

Why is a temperature gradient set up in a heated rod? [duplicate]

Suppose a cylindrical rod is maintained at 100 degree Celsius and the other at 0 degree Celsius. My book says that after reaching "Steady State" the rod will have developed a constant temperature ...
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464 views

Physical meaning of potential in heat equation

I'm working on the mathematical theory of parabolic equations. The prototype of such equations is heat equation given as follows : Let $\Omega$ be a bounded region of the space and $T>0$ a fixed ...
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2answers
55 views

Which heat equation should I choose if I want to toggle between conductive and convective heat transfer?

I have a science project where I have an aluminum cylinder, filled with oil, with a diode chain floating inside of it. The diode chain has a bimetallic temperature switch on it that turns off the ...