The tag has no usage guidance.

learn more… | top users | synonyms

0
votes
1answer
42 views

What metal (or any other material) is a good thermal coductor but a bad conductor of electricity?

Also, this material needs to be easily manageable and accessible. So, I am trying to make a DIY soldering iron and I need to insulate the part that makes the heat and the part that transfers the ...
1
vote
2answers
2k views

Finding effective thermal conductivity multi-layer cylinder

How does one find the effective thermal conductivity of a cylindrical body made of multiple layers? E.g. Copper core (k1), insulator 1 (k2) and insulator 2 (k3). I need the effective properties for ...
2
votes
5answers
91 views

Is perfect thermal insulation possible?

Supposing someone says they have a sample of insulanium with the following properties: If you make a thermos out of insulanium, it will keep a drink hot or cold forever. If you put your hand on a ...
7
votes
2answers
251 views

Is the thermal conductivity of metals affected by magnetic fields?

Especially for a ferromagnet a magnetic field should have a field-induced band shift in the density of states but I wonder if this shift is big enough to be significant and affect the thermal ...
3
votes
1answer
79 views

What is the temperature of water at the end of the pipe?

I need to solve the following problem for a practical application. Water, initially at temperature $T_0$, flows with a constant speed $v$ through a PVC tube of length $l$ and diameter $D$. The ...
0
votes
1answer
41 views

Calculation of temperature distribution in bulk glass due to laser heating

I'm trying to figure out how to simplify the problem where laser pulses are focused to a small spot in bulk glass. The waist of the beam is about 20 microns. At the wavelength used there is only two-...
0
votes
2answers
228 views

Work done in adiabatic reversible process

I was solving a problem on turbine.the steam works on turbine adiabatic reversibly .Is change in enthalpy or is it change in internal energy which equal this work?
3
votes
1answer
214 views

Will heat flow by conduction oscillate until thermodynamic equilibrium is reached in a solid object?

Consider the following thought experiment with $2$ conducting objects $A$ and $B$, where object $A$ is initially at a much higher temperature than object $B$. The objects are now placed in perfect ...
0
votes
0answers
15 views

Question about a particular thermal shock scenario

I watched this video https://www.youtube.com/watch?v=xbuvcQrAOSk Where they heat up a pyrex pot and then add a few drops of cold water to see how the pot will react (while shooting the scene with a ...
0
votes
1answer
181 views

What is the overall rate of heat conduction through two pipes of different dimensions if the thermal conductivity is not constant?

I am trying to work out how I would find the rate of heat transfer through two pipes made of the same material that are joined at their ends but which have different cross-sectional areas and lengths. ...
4
votes
2answers
294 views

Is it possible for an object to have low specific heat capacity and low thermal conductivity?

As I see, there are many examples of object with low specific heat capacity and high thermal conductivity and vice versa. Since they are different properties of matter and their definitions are not ...
0
votes
1answer
29 views

Difference in steaming with superheated steam to saturated steam in coffee beverages

Coffee machines are emerging on the market which claim to superheat the steam they use in heating and aerating milk via a submerged nozzle for latte/cappuccino type beverages. So instead of the ...
2
votes
1answer
416 views

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 ...
0
votes
0answers
26 views

What is the rate of heat transfer between 25C water and 20C air?

This might be an elementary question, but I was only able to find the formula for heat transfer only in one substance. *Surface area: 1 meter square
0
votes
1answer
23 views

At what rate does a wet clothing decrease the temperature of a human body?

The question is required for my project, but it is frankly too hard for me... The variables that I consider are: Human Body: 36.5(C) Air: 20(C) Sunlight Intensity: 1,368(W/m^2) Wind Speed: 20(km/hr) (...
-3
votes
2answers
63 views

Which one is better at keeping you warm? [closed]

Does Glass feel warmer during winter when you keep your feet on it or Wood?
5
votes
1answer
57 views

Why do electrically conductive materials tend to be thermally conductive?

It's hard finding substances that are good insulators of one and conductive of the other. Why the correlation? And why do some materials not have this correlation?
3
votes
1answer
87 views

Why thermal conductivity increases with temperature?

what is the molecular mechanism with which thermal conductivity increases by increasing temperature? at least for metals? I know that heat increases the oscillations of the atoms in the crystal. But ...
4
votes
2answers
97 views

Heat distribution in a long cylindrical electrical resistive element

I want to know what the maximum temperature will be within a heating element. Quite a few assumptions can be made, such as constant thermal conductivity, constant electrical resistivity, and assume ...
2
votes
4answers
991 views

Glass pipe cutting

I want to know how to quickly create the straightest possible breaks in glass pipes I apologise if this is only borderline suitable for a physics forum - I just hope experts with a lot of experience ...
0
votes
3answers
392 views

Heat flow in a hollow cylinder

Consider a hollow cylinder of different outer radius and inner radius and two different temperatures are maintained at the outer and inner surfaces such that inner temperature is higher. Because of ...
0
votes
1answer
41 views

Thermodynamics - Change in temperature based on time

Hello Physics Stack Exchange, This is my first post on this forum, please correct me on any semantic mistakes I may make. Recently in my physics class we did a lab on Heat Capacity, where we had a ...
0
votes
2answers
26 views

Discrepancy between the rate of heat flow

I'm in a introductory college physics class, and my professor recently gave us this formula for the rate of heat flow: $\frac{dQ}{dt} = \frac{A \Delta T}{R_{factor}}$ where $R_{factor}$ is $\frac{L}{...
2
votes
3answers
164 views

Why engines don't melt?

The temperatures of internal combustion engines are well above the melting points of the component materials. For example, temperatures can reach 2200° C whereas the melting point of aluminium is 659°...
0
votes
1answer
41 views

Convective heat transfer coefficients - how do you calculate them?

How do you calculate (or otherwise determine) h_i and h_o (convective heat transfer coefficients) for a heat exchanger? Standard thermodynamics equation below for reference. My specific situation ...
-1
votes
3answers
117 views

Bird on electric wire: theoretical distance between the two bird legs [closed]

Hey guys, please someone help me with this exercise :) For our exercise, assume that the bird’s body resistance (from leg to leg) is 50kΩ. Given is a high voltage power line with a current of 100A ...
2
votes
1answer
59 views

Localized Phonon Vibrational Modes and Thermal Conductivity

I chanced upon this 1D chain Mass Impurity model: At the end of all the derivations, it concludes that Case 1: $ 0 < M_0 < M$ The impurity is lighter than the host atoms. The frequencies ...
0
votes
0answers
18 views

Systems with these temperature dependence of thermal-conductivity

I want to find out examples for systems (of any kind) in which the temperature dependence of thermal-conductivity($\kappa_{T}$) is of type- \begin{equation} T^{-\alpha}~~~~~ where ~~~~~\alpha>0 \...
3
votes
2answers
164 views

Different results for thermal resistances using different methods

A system is set up which is composed of a cylinder with hemispheres on either ends. The length of the cylinder is l and inner and outer radii of cylinder and hemisphere are $R_i$ and $R_f$. The ...
0
votes
1answer
36 views

Is thermal transfer in a vacuum proportional to temperature difference?

I would have thought that heat dissipation was proportional to temperature difference, especially in a vacuum. Is this true?
1
vote
0answers
19 views
3
votes
2answers
60 views

Why are metals worse conductors when heated?

When metals, (such as in circuits), are heated, their ability to conduct electric current is hampered. Why is this? Does the transition towards liquid disrupt a metal's ability to conduct, or is ...
0
votes
1answer
39 views

Relationship between thermal conductivity and reaching the steady temperature

The diagram is for three materials with 3 different thermal conductivities, i think the material with higher thermal conductivity is the number 1 because it transfers the heat much better so it gets ...
0
votes
1answer
49 views

Transfer of heat from ice to water in a beaker

How does the transfer of heat takes place from ice below 0 degree celcius to water at room temperature? Does it take place by conduction? Does temperature of water rises uniformly throughout or it ...
3
votes
5answers
5k views

Why does a larger thermal conductivity provide a smaller temperature gradient?

I was thinking about Fourier's Law in heat transfer today and for some reason I am just not understanding the relationships it gives us. Fourier's tells us that if the heat transfer rate is kept ...
1
vote
1answer
94 views

Help me solve a heat conduction/emission transfer problem. Mathematica has failed me

My problem: A thin-walled tube (length $L$, diameter $D$ and wall thickness $t \ll D$) is in a vacuum. It is held on one end (at $x=0$) by a heat source at constant temperature $T(0)=T_0$. The only ...
0
votes
1answer
99 views

Drift velocity of electrons in a conductor

How does the drift velocity of electrons in a conductor depend on the temperature? I have two contradicting views for this. First, we can say that increasing the temperature of the conductor will ...
0
votes
2answers
250 views

relationship between pressure and thermal conductivity

Using a kinetic model for gases, is it possible to derive a relationship between pressure and thermal conductivity? From what I have read, I thought pressure was independent of thermal conductivity? ...
0
votes
1answer
22 views

Estimating fraction of radiant energy absorbed by a metal

I have a couple of texts on thermodynamics and radiant energy but am finding it difficult to figure out from these how energy absorption and reflection work. The area of interest is heating ferrous ...
3
votes
3answers
16k views

The relation between permittivity and conductivity

I am able to measure relative permittivity $\varepsilon_r$ of a fluid, and I want to calculate conductivity of same fluid. Can anyone suggest me how to do this? I found one formula to calculate ...
1
vote
2answers
2k views

Why bodies lose heat faster in water than in air?

A simple question. In several places, including this very recent and already famous paper http://www.sciencemag.org/content/348/6236/786.short it is stated that bodies lose heat in water very fast ...
0
votes
0answers
17 views

What's the simplest, first order way to calculate the temperature change in this scenario?

I am trying to model this experiment in a simple (i.e., relatively analytic, non-computational) way. I have a little square of a thin film (10s of nanometers thin) of material A, on a relatively ...
0
votes
3answers
89 views

Thermodynamics at the stoves, cooking problem

I was wondering about a daily question with respect upon heat, time and thermodynamics "made easy". Supposing I put a pot on the stove (we can say without losing so much that the pot is a cylindrical ...
1
vote
1answer
29 views

thermal fatigue and thermal conductivity

Today I argued that heating and cooling a metal many times will affect its thermal conductivity. My idea is that heating and cooling, ie. thermal fatigue, will affect longterm the the microstructure ...
0
votes
1answer
56 views

Conduction problem [closed]

A hot reservoir with a temperature of $782 K$ is $0.56 m$ away from a cold reservoir with a temperature of $331 K$. The two reservoirs are insulated from each other except for a rod of brass ($k = 109 ...
0
votes
1answer
58 views

Why the 3D heat equation is $\frac{\partial u}{\partial t}=\alpha\nabla^2u$ [closed]

Why the 3D heat equation is $$\frac{\partial u}{\partial t}=\alpha\nabla^2u=\alpha\left(\frac{\partial^2 u}{\partial x^2}+\frac{\partial^2 u}{\partial y^2}+\frac{\partial^2 u}{\partial z^2}\right)?$$ ...
1
vote
0answers
88 views

Is thermal and electrical conductivity correlated for all phases of matter?

After reading this interesting post about why copper is a great heat conductor, I wondered if a plasma would conduct heat better than a gas. Or, are some properties like density more important for ...
0
votes
1answer
51 views

Anomalous expansion of water when heated

In one question I found that when water was heated from 0°C to 15°C then the volume 1st decreases and then increases why is that so ?
3
votes
1answer
357 views

Why are wooden houses warmer than concrete ones in cold regions?

Why are wooden houses warmer than concrete ones in cold regions? I went looking for data and I saw that both have similar emissivity and similar conductivity. Thus I am confused. Moreover, the ...