11 votes

Does good electrical conductivity imply good thermal conductivity?

Beryllium oxide is a very good electrical insulator but at the same time the best non-metal (except diamond) thermal conductor. So to summarize. In general, good thermal conductivity is correlated ...
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  • 1,046
9 votes

Are there any materials known to be sound-insulating but thermally-conductive?

I can think of a few possible ways to approach this. Probably the first thing to look at is the design of the case itself. They generally tend to be made up of thin, flat panels riveted to a frame. ...
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7 votes

Does good electrical conductivity imply good thermal conductivity?

For metals, good electrical conductivity does indeed imply good thermal conductivity. This is known from the Wiedemann–Franz law, which gives the ratio between electronic contribution of thermal ...
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  • 155
6 votes
Accepted

Why does the author assume the temperature to remain constant, in this case, along the axial direction?

For a steady state solution, (after a loooong time), because the temperature of the air is considered constant the heat lost $\dot{q}$ to the environment will be equal to the heat lost from the fluid $...
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  • 22.6k
5 votes
Accepted

How can I determine the thermal conductivity of an open container?

If you are interested in knowing why your tea is cooling in different times, you already answered the question yourself. It is due to the different thermal conductivities of the different items you ...
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  • 1,704
5 votes

Easily compute a good approximation of heat conductivity of cooled semi-vacuum (water vapor + air)

In the molecular flow region of pressure, the thermal conductivity of an ideal, monatomic gas is obtained by this equation. $$ k = \frac{1}{\pi^{3/2} d^2}\sqrt{k_B^3T/m} $$ where $d$ is the ...
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4 votes

Examples of two dimensional heat conduction problems

You can model heat conduction in two dimensions when there is no heat flux in the third dimension. (Sorry if that sounds trite, but IMO that part of the question is so trivial it shouldn't be ...
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  • 12.5k
3 votes

Rapidly cool a flue gas without water circulation

Your approach is not an unusual one, engine brakes to measure horsepower usually make use of such a method, but they use much bigger water barrels. To answer your questions: "Can I just fill a ...
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  • 1,164
3 votes

Heat Loss in Typical House

No, it's not meaningful to express it as a ratio. The best insulation is deep insulation everywhere. You also need to consider convection losses, and your ventilation strategy. The attic is usually ...
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  • 3,701
3 votes

Use two passive CPU coolers on one single CPU?

Well, I would think that two smaller ones rigged up in an "amateurish" fashion (apologies, but that's we both are, right) are going to be worse than just one (sufficiently large) properly mounted ...
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  • 251
3 votes
Accepted

Are there differences between Ice Packs?

There can be differences between ice packs, but in practice the differences seem pretty small, and you'll have a hard time finding hard data on different ice packs' cooling abilities. How much ice/ice ...
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3 votes
Accepted

Is it just surface area alone that causes bridges to freeze?

Heat is the transfer of energy from a hotter region to a cooler region. The surface in contact with the earth enjoys the benefit of conductive heating. Being cooler, the energy of the warmer earth ...
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  • 6,192
3 votes

What material might by used to 'staple' coils down in this stovetop element?

I expect the same material as the coils would be the easiest answer ; nichrome ,Inconel ( 600, 601 or other number) , chromel. There are small differences but any one you can find would be good. That ...
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  • 5,779
3 votes
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How can I trust a K-type thermocouple purchased from a no-name company?

Go to Omega.com to learn all you want to know about thermocouples (TC). I'll give you here a few basics, directed at your questions. TC science is well understood and standardardized. Every type TC ...
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  • 370
3 votes
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Filling gaps in heatsink design to improve thermal conductance?

Your are correct that the smallest surface area will be a limit on the thermal conductivity. Before we dive into that lets look at the over all approach and some other limits. Are your temperatures ...
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  • 7,469
3 votes

What and why thermal diffusivity?

Both Thermal Conductivity and Specific Heat relate two different quantities, "heat" and "temperature." The point of giving "Thermal Diffusivity" a separate name is that ...
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  • 12.5k
3 votes
Accepted

Calculate Thermal Conductivity of Layered Structure

The thermal resistance for a slab in steady-state heat transfer is $R_t = w/(kA)$ (K/W), where $w$ is thickness (m), $k$ thermal conductivity (W/m K), and $A$ cross-sectional area (m$^2$). For serial ...
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2 votes

Are there any materials known to be sound-insulating but thermally-conductive?

The first couple of things that come to mind are metallic 'wools' (ex. steel wool/stainless steel 'scrub pads'), or carbon foams. Metal wools will provide minimal thermal insulation (metal strands ...
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2 votes
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Relationship between thermal conductivity and reaching the steady temperature?

$\dot{Q} = k A \frac{\Delta T}{l}$ $l$ thickness $A$ surface area From this follows that besides other factors the rate of heatflow is proportional to the thermal conductivity $k$. $\dot{Q} \...
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  • 1,704
2 votes

Radioactive Materials to Energy AT HOME

Attempting this as a home experiment is unlikely to be feasible. https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator#241Am gives the efficiency of professional prototype designs using ...
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  • 12.5k
2 votes
Accepted

Winding a wire heating element after a few uses

I have not used Kanthal, but I imagine it has similar properties to nicrome. Basically when you heat the wire up and cool it quickly, it quenches the wire. To reverse this process (or avoid it all ...
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  • 7,469
2 votes
Accepted

How thick do I need to make the insulation in my homemade furnace?

First off, the design problem is not trivial and it looks like you have done your homework. On high temperature, small vessels like this you need to consider the 3 dimensional transfer of heat (the ...
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  • 7,469
2 votes

Does good electrical conductivity imply good thermal conductivity?

As alluded to in the other answers, a most notable exception is diamond. Diamond is an excellent thermal conductor. The thermal conductivity of natural diamond is around 22 W/(cm·K), which makes ...
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  • 840
2 votes

Calculation for heat transfer rate / cooling capacity for air cooled solid

Stagnate Gas When the gas is stagnate, view the system as though it is an extended surface (from compressor to outlet). Take the heat transfer inside the tube as having no radial component. Develop ...
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2 votes

Wall temperature of pressure cylinder - Boundary condition

There are a lot of variables to consider for a thermal analysis, but none of them require pressure as a boundary condition. As alephzero indicated in their comment, this is function of heat source ...
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2 votes

How to calculate the volume of air required to keep electrical box cool?

This question can only be answered after many tests as to the convective properties of the box, it's geometry with respect to the geometry of the void, ignoring radiation. Because convection which is ...
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  • 21k
2 votes

How to calculate the volume of air required to keep electrical box cool?

If I get you right, there is a box having a small device that dissipates 30 Watts of heat continuously into the air. The air is blocked into a box, no way in or out. There are no fans/blowers trying ...
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2 votes

Heat transfer for a copper rod

If your temperature sensor is far away from the heat source, the detected temperature may increase even after the heat gun is turned off due to a preexisting temperature gradient evening itself out.
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2 votes

Heat conduction in a hollow cylinder with low conductvity coefficient - Why do I get negative temperatures?

The results are telling you that—according to this model—there is no outer temperature that you can apply to obtain an inner temperature as low as 1300 K at steady state for this power output, ...
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2 votes

Material selection of heating element

Consider that ohmic heaters are usually made of thin wire, and that the majority of the current flow going through any wire is close to the surface of the wire. Both these things mean that even if the ...
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