# Tagged Questions

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### Heat transfer in liquid helium channel connected to “infinite” reservoir

I am trying to solve the temperature distribution in liquid helium using numerical analysis (OpenFOAM for those who are familiar with it). One part of the fluid is contained in a narrow channel, one ...
1answer
57 views

### Thermal Interaction in a Vacuum

In order for a thermal interaction, or heat energy transfer, to take place, two bodies must be in contact. Whether this be the particles of air in contact with your skin to make you feel warm or cold, ...
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31 views

### Solving for temperature at the source, given a distant measurement

Let me start of by stating that I am not a physicist, so this question may appear trivial to those more enlightened than me. My problem is as follows: I have an object at $x = 0$ and at some initial ...
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44 views

### Kubo formula for thermopower (seebeck coefficient)

I have a long-standing puzzle about the Kubo formula relating to the thermopower defined as S=L_{21}/L_{11}. Here L_{ij} are elements a 2 × 2 matrix of transport coefficients, with J_E=L_{11} E - L_{...
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### How do you go from the heat equation to calculate the steady state heat transfer to the end of a rod?

Heat equation: $$k\nabla \cdot \nabla T + \dot{q} = \rho C_p\frac{\partial T}{\partial t}$$ I want to know given a rod or a cylinder of material, but lets start simply with a rectangular rod, and ...
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87 views

### How to find the variation in temperature at a certain point inside a body undergoing heat transfer via conduction?

I am trying to find a way with which I can find out the temperature of a certain point inside a body undergoing thermal conduction. I understand that this might not be very simple to calculate since ...
2answers
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### 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 ...
1answer
61 views

### Melamine dish cools beyond ambient temperature

I have observed a phenomenon that I find hard to understand. A plastic, melamine like dish is filled with food (spaghetti, chile, soup, etc.) The dish and food is heated in a normal microwave oven ...
2answers
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### Loss of temperature of a sphere [closed]

I am trying to get an intuition of whether it theoretically seems possible for a living cell (a yeast for example) to regulate its own temperature. Let's consider a spherical living cell which radius ...
1answer
1k views

### How does the hot cup of tea cool down? [duplicate]

I am not sure about my answer. I think that the cup of tea cools down by the following modes: Radiation between the surface of the tea and the air molecules. Conduction between the tea and the cup ...
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### 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 ...
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235 views

### Air Thermal Conductivity vs Humidity

If air of a certain temperature blows through a car radiator (or a computer case), what effect will air humidity (non-condensing) have on cooling rate?
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### Single story, hotter outside, some shade from porch, enough to cool house with/without air flowing?

So, I know this question, without shade or one-story, has been answered many times on the 'net, so I have some actual physics for the one-story. I am fairly certain my roommate mixed up thermal ...
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 ...
3answers
1k views

### Does paint affect the thermal conductivity of a metal?

We noticed that in our experiment that painting a metal increases its thermal conductivity; is this true? If so, can you guys send me a link to a research paper to support this claim.
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983 views

### How can a material conduct heat but not electricity

Mica is a good conductor of heat but an electrical insulator. According to free electron theory (which applies only to metals) free electrons carry heat and electricity. Therefore, thermal ...
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### Where do limits of integration come from in the equation of heat transfer by conduction?

I was watching the third lecture of Diffrential equations on OCW. As an application, the model of heat transfer by conduction is provided. We derived this equation which models the system where $T$ is ...
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29 views

### Does illuminating a conductor with light energy less than its workfunction change the measured conductivity?

For example, does the light absorbed in an exposed metal wire increase the average velocity of the electrons, hence increasing mobility and conductance?
1answer
342 views

### How does temperature in a solid sphere change with time when moving through a gas?

I'm interested in the following problem: There is a solid sphere with radius $r$ and mass $m$ at temperature $T_{s0}$. It is moving at velocity $v_s$ through a gas of temperature $T_g$. How does the ...
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### What is the boundary of restorable thermal expansion?

As every book indicates, thermal expansion is a linear process $\frac{\Delta L}{L}=\alpha \Delta T$. Upon heating an object the result is thermal expansion. If we cool it down it is restored its ...
2answers
564 views

### What's the true reason behind thermal expansion?

Thermal expansion is a normal concept everyday. There are 2 explanations: 1, thermal expansion result in stress, then result in deformation 2, thermal expansion result in deformation, then result in ...
1answer
621 views

### What type of glass is used in oven glass doors? [closed]

I understand that the glass used in convection oven door must be able to withstand high heat. But what should be the exact specification if I am thinking of replacing my broken oven door and ...
1answer
266 views

### Does doping silicon affect its coefficient of thermal expansion (CTE)?

Everywhere I have searched I always see the CTE of silicon listed as 2.6*10e-6 °C^-1. However, I have silicon that was phosphorus-doped to an ion concentration of of 2.41*10e11 atmos/cm^3, and I would ...
2answers
550 views

### Why does room temperature water and metal feel almost as cool as each other?

From what I've read about heat, temperature and conductivity, I understand that the reason water at room temperature feels colder than most other things at the same temperature (like wood, air, cotton)...
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449 views

### Copper Bath Keeping the Water Warm

I was watching a home improvement program the other day and the presenter mentioned that a copper bath kept the water warmer for longer. She didn't say what it was being compared with but I have ...
1answer
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### Thermal conduction through 1D rod with changing thermal diffusivity?

I've been working with solving partial differential equations in 1D numerically using the finite difference scheme. My case is for example this: I've got a rod that's insulated around the sides such ...
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55 views

### How water and honey behave with increasing pressure?

Is there any relation between pressure and viscosity of water and honey? I hardly found the topic. Is it related to the Laplace law?
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### Thermal conductivity in vacuum

It is my assumption that material objects preserve/gain heat via: 1) material contact (air or other touching material/object) and/or 2) absorbing radiation / electromagnetic waves So, imagine that ...
2answers
165 views

### How does aerogel attain its enormous heat isolation properties?

In a text about properties of aerogel I read some interesting facts - clothes with aerogel proved to be impractical, being far too warm to wear. If you isolated a house with aerogel and lit a candle ...
1answer
209 views

### How to define the heat current in an isotropic continuum material

I'm doing a FDTD (finite difference time domain) simulation of an isotropic continuum material. And I have several questions. How do you define the energy transferred through an isotropic continuum ...
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180 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. ...
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59 views

### Thermal conductivity in gases

I've been musing about thermal conductivity and came upon the following question. Heat is transported through matter by molecules passing their kinetic energy onto other molecules, or simply by the ...
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?
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96 views

### For thermal mass flow measurement technologies is it necessary to measure gas pressure to determine volumetric flow rate?

Mass flow readings from thermal mass flow measurement technologies often provide output readings in volumetric units (e.g. standard liters per minute). Mathematically I can derive the volumetric flow ...
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29 views

### Hot wire anemometry and gas species

Hot wire anemometry is a technology that measures mass flow of a gas stream in the neighborhood of a heated wire. The sensitivity of a flow sensor using this technology is usually specified for a ...
3answers
304 views

### Asymmetric heat conduction?

So I have this side-view drawing. Now I wonder, will such a multi-layer material have asymmetric heat conduction properties? Namely, because of radiative conduction, reflective aluminum surface ...