The tag has no usage guidance.

learn more… | top users | synonyms

4
votes
2answers
256 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
2answers
1k 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
1answer
400 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 ...
1
vote
1answer
26 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 ...
1
vote
1answer
34 views

Is $\kappa_e$ caused by charge-carrier transport or electron transport?

$\kappa$ usually symbolises thermal conductivity, a material's ability to conduct heat. $\kappa$ can be expressed with other partial thermal conductivities: $\kappa=\kappa_e+\kappa_{ph}+...$ where ...
1
vote
1answer
65 views

Spherical Shaped Electrical Leads for Thermal Conductivity Mitigation?

I am designing a thermionic converter and one of the biggest inefficiencies is the thermal conductivity and limited electrical conductivity of the leads. I'm trying to mitigate the loss of heat ...
0
votes
1answer
19 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 ...
0
votes
1answer
30 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?
0
votes
1answer
35 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 ...
0
votes
1answer
18 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 ...
0
votes
1answer
39 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 ?
0
votes
1answer
169 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. ...
0
votes
1answer
191 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?
-1
votes
1answer
178 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?
-1
votes
1answer
325 views

How to prove R value for insulation?

I ran some tests on different types of insulation. I heated water, and placed it into an insulated box. The temperature was recorded every minute, for the water, as well as the air. The insulation ...
-1
votes
1answer
801 views

Why do phonons cause excellent heat conduction in diamonds?

Phonons are the quantum of lattice vibrations in crystals and are not to be confused with photons, the gauge bosons of the electromagnetic force. Apparently, they contribute to heat conduction, but I ...
2
votes
0answers
158 views

Is my method of calculating thermal conductivity of a metal wrong?

I am trying to determine the thermal conductivity of pure copper at various temperatures using the Weidemann-Franz Law but for some reason it is not matching up to textbook data. I used the Bloch ...
2
votes
0answers
86 views

In a non-degenerate plasma, why are e-e collision negligible compared to e-ion for thermal conduction?

I'm trying to make some order of magnitude estimates of heat transfer in stars - to better understand 1) why conduction is said to be negligible (for non-degenerate matter) and 2) when convection ...
1
vote
0answers
57 views

At the lambda point, why does specific heat capacity tend to infinity?

The specific heat capacity is the energy required to raise the temperature of unity mass by 1K, if at the lambda point all the bosons occupy the lowest quantum state, shouldn’t the specific heat ...
1
vote
0answers
80 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 ...
1
vote
0answers
44 views

Heat transfer coefficients

I am trying to make a model of non-stationary heating on a plate and I have questions considering coefficients. I am using explicit method to solve it (have to use it). I am not sure if I am using the ...
1
vote
0answers
30 views

Why the whole object cannot be observed to vibrate when energy is transferred through conduction (solid)?

Conduction is the transfer of thermal energy when particles in an object vibrate and collide with neighbouring particles thereby transferring their kinetic energy to them, why doesn't the whole object ...
1
vote
0answers
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?
1
vote
0answers
31 views

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 ...
1
vote
0answers
88 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 ...
1
vote
0answers
467 views

Thermal expansion of two bolts

I have this question asking me about the thermal expansions of two bolts, a steel one, and a brass one. I have the equation: $\ (\delta L/L)/T = \alpha $ I don't understand how I can use this ...
1
vote
0answers
145 views

Conduction– conservation of energy

So I know that conduction is transfer of thermal energy by direct contact via molecular collisions. For conduction, $Q/t$ is the rate of heat flow and is heat current ($I$). My textbook says that ...
1
vote
0answers
209 views

Thermal Conductivity Graph

This is our first time (as an engineer) seeing this type of graph that we can't interpret. This is a rough comparision of thermal conductivity from the Wiki page. ...
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 ...
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
0answers
57 views

Heat Losses to furnaces

I am looking in to the thermal efficiency of a furnace vessel. I am wanting to get a full, or at least better, understanding on the calculations needed to look at the thermal efficiency. So I know ...
0
votes
0answers
35 views

How is Thermal Design Power (TDP) related to Surface Power Density (SPD)

Although this question is kind of IT related I'm interested into the actual physical backgrounds and thus posting it here. I know that TDP is an indicator for dimension of the thermal dissipation ...
0
votes
0answers
40 views

Thermal conductivity of a binary gas mixture

I want to estimate the thermal conductivity of binary gas mixture, say water vapor+nitrogen. I assume the mixture as ideal gas. The molar fraction and thermal conductivities of the components are ...
0
votes
0answers
22 views

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 ...
0
votes
0answers
30 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 ...
0
votes
0answers
40 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 - ...
0
votes
0answers
34 views

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 ...
0
votes
0answers
48 views

Activation energy as a function of defects

Electrical conductivity has a form of Arrhenius equation. It is assumed that activation energy decreases with defect density in the insulating state and becomes zero in the conducting state. Can one ...
0
votes
0answers
54 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?
0
votes
0answers
315 views

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 ...
0
votes
0answers
57 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 ...
0
votes
0answers
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 ...
0
votes
0answers
56 views

Can we make any substance that will produce ions at low temprature

I am talking about thermal ionization, Is to possible to make any material or is there any element that can be ionized at let say 20 degree centigrade Temperature? I am a computer engineer and into ...