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Questions tagged [heat-conduction]

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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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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
50 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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1answer
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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
23 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
53 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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0answers
50 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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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
36 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
31 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
28 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
32 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
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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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0answers
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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
136 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
50 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
158 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
111 views

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
44 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
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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
63 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
40 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
187 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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1answer
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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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4answers
112 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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5answers
452 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
54 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 ...
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3answers
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Why does a lot of water vapour come suddenly after the heat source of boiling water is removed? [duplicate]

I have noticed this several times. When I am boiling water, a few seconds before its boiling point, vapours are formed as usual. But if I turn the gas off before boiling, the moment it turns off, I ...
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2answers
61 views

More efficient way to heat liquids

If we consider two processes to heat up a bucket of water as follows:- Taking one bucket and heating it to our desired temperature for V volume. Taking two buckets of half the volume and heating one ...
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2answers
197 views

What is temperature as a function of time in Fourier's Law?

Can we find temperature as a function of time using Fourier's Law of thermal conduction? For example: If we have two square parallel plates of a given length, width, and distance apart with one ...
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2answers
267 views

Temperature at different points in a metal rod during heat conduction

$$ k = \frac{\frac{Q}{t}}{A(\frac{T_1 - T_2}{L})} $$ where k is thermal conductivity of the solid, Q is total amount of heat transferred, t is time taken for the heat transfer, A is area of the cross ...
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3answers
74 views

Focusing Sunlight with Flat Mirrors- solar barbecue

Say somebody had 48 1sqft glass mirrors (almost 4.5 sq.m total), because these tiles cost about $1 each. If mirrors are all tediously aligned to redirect sunlight onto a Weber BBQ, the air temp inside ...
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0answers
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Behaviour of photons in different materials

Often when learning about heat transfer within metals and thermal conductors,the heat transfer is explained by saying how molecules vibrate in thier positions to conduct heat. But if that's the case ...
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1answer
53 views

Is the randomized motion of particles produce heat?

In the show on factomania from gregg foot I've heard that when sun light comes then some gas particles of air get more energy and velocity and as the average kinetic energy of molecules is Temperature ...
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1answer
74 views

Calculating rate of heat loss through conduction and radiation

I'm trying to calculate the rate at which a hollow cylinder with a heating element inside will lose heat, specifically through both conduction and radiation. I realize that the total heat loss per ...
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1answer
41 views

Effect of pressure when drying wet clothes in a windy environment

When we hang wet clothes outside, they dry faster if it is windy. The wind causes forced convection and removes the air saturated with vapor, and the rate of evaporation does not decrease much in ...
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1answer
69 views

What causes burns when in contact with hot water?

As I understand it thermal energy (heat) is simply a measure of the kinetic energy of an object (For example : water).Hot water is simply water with a larger kinetic energy in its molecules, right ? ...
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3answers
188 views

In an adiabatic process, why is it that if work is done very quickly then there is no time for energy transfer to the surrounding?

I don't seem to understand the logic in adiabatic process of how 'if work is done on the system very quickly e.g. compress a piston containing n number of gas particles, there is no time for energy to ...
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1answer
290 views

Temperature of solids and “average translational kinetic energy”

Temperature is related to the random motion of atoms and molecules in a substance. More, specifically, temperature is proportional to the average "translational" kinetic energy of molecular motion. ...
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0answers
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Thermic isolation for 3D printer buildplate

I have questions about heat conduction, directly related to a problem I have with my 3D printer. Here is (schematic) front view of my 3D printer buildplate: The orange top plate is a PCB heated bed (...
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1answer
35 views

How do I convert $W/(mK)$, $W/m^2$ and $W/(m^2K)$ to the same “dimensionality” and unit?

How do I convert $W/(mK)$, $W/m^2$ and $W/(m^2K)$ to the same "dimensionality" and unit? $W/mk$ is thermal conductivity. $W/m^2$ is heat flow density related to one unit. $W/m^2k$ is heat transfer ...
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0answers
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Heat loss due to thermal penetration [closed]

I am doing an experiment on a regenerator (Period 120 s). I found the thermal penetration depth through the insulation as 13 mm. I'm not sure how to estimate this heat loss?. I tried to estimate by ...
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0answers
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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 ...