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Questions tagged [thermal-conductivity]

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2answers
50 views

Compression of gas [on hold]

What happens when a gas kept in a metallic container is suddenly compressed via a piston and left for some time? Does the pressure increase or decrease?
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1answer
10 views

Relationship between CO2 concentration and thermal conductivity of the air in a volume?

How much would the percentage of CO2 in a room need to change in order to make a measurable change (using transient hot wire method) to the thermal conductivity of the air inside room? Are there other ...
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0answers
31 views

What formulas do I need to calculate the time it takes for a room with opened window to become the same temperature as outside?

I want to calculate how long I have to open my window to become the same temperature as outside. To make things more easy let’s assume there’s almost no wind helping the exchange of temperature.
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0answers
22 views

Determination of read/write lifespans of NAND drives [migrated]

I check around and there are various numbers for different manufacturers solid state drives as read and write life terms. At the very fundamental level input/output speeds of these devices are pretty ...
0
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1answer
37 views

Thermal resistance of a rod

I have a confusion about how to calculate the thermal resistance of a solid rod ( not hollow). The general formula is $$R=\ln(r2/r1)/(2\pi Lk)$$ In my case, $r1=0$ Any hint would be highly ...
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0answers
25 views

Fluid dynamics - boundary later equation $f'''+ff''-f'^2+\theta = 0$ and $\theta''+Prf\theta' = 0$

Our lecturer gave us a system of boundary layer equations: $$\begin{align}f'''+ff''-f'^2+\theta &= 0 \\ \theta''+Prf\theta'&=0 \end{align}$$ subject to boundary conditions: $$f=f'=0, \...
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2answers
47 views

which give higher cooling rate , strong circulated water or thick copper plate? [duplicate]

imagine if I have hot metal piece I want to cool it as fast as possiple, should I put it in strong circulated water bath or just stick it between 2 thick copper plates ? the calculated heat ...
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1answer
23 views

which is more effective chilling for metal casting, thick copper die or water-cooled thin copper mold? [closed]

It is will known that increasing cooling of a metal casting will lead to finer micro-structure which mean higher mechanical properties. If I have 2 molds one is thick copper die ,& second is just ...
2
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2answers
52 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 ...
0
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1answer
32 views

Can a semiconductor become more conductive than a conductor with heat?

I am looking for a good idea for a science fair project for PA Junior Academy of Science (PJAS). An interesting idea that I have stumbled across is making semiconductors more conductive with heat. I ...
1
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1answer
21 views

Air gap in a radiant barrier insulation system: why?

It's generally accepted that a reflective surface, when used to insulate a system by reflecting radiant energy back to it, must have an air gap in front of it. Why exactly is this, and what determines ...
0
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1answer
35 views

Is placing a fire safe inside a larger fire safe helpful?

If I put a small fire safe (say, one rated for 1 hour at 1700°F) inside a larger, equivalently-rated fire safe, to what degree is the fire/heat protection improved?
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0answers
25 views

Experiment to determine thermal conductivity of composite material

Recently at a laboratory class we experimentally measured thermal conductivities $k$ of several materials. The experimental set-up was this: The idea was to use hot steam from a steam generator to ...
7
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2answers
866 views

Does the order in which I layer blankets matter? [closed]

It’s getting cold where I live and I sleep with multiple blankets. I am wondering whether it generally matters how I might use blankets to keep something warm; if I put blanket $A$ on top of blanket $...
2
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2answers
119 views

Is thermal conductivity correlated with speed of sound in metals?

Right off the bat I should say: thermal conductivity and electrical conductivity are definitely correlated in metals. image source: https://www.doitpoms.ac.uk/tlplib/thermal_electrical/printall.php ...
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1answer
20 views

Thermal Efficiency

For a thermally efficient house, is it better for the windows to be framed with something like aluminium, or steel? I am considering the thermal conductivities, aluminium has a value of 200, while ...
2
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3answers
151 views

Why does a steel rod keep increasing its temperature after removing the source of heat?

I watched an experiment and I'm not sure why this happened. A metal rod was heated by a flame like this: sensor ======== -> metal bar flame The metal sensor ...
1
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1answer
32 views

Vapor pressure of sublimating ice in vacuum

I am trying to find a vapor pressure of sublimating ice as a function of thermal energy being absorbed by ice. Basically, I am starting with a sample of ice (t=200K) in a vacuum. From there, I am ...
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0answers
21 views

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 ...
0
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0answers
19 views

Pressure and temperature conditions for discarding the ideal gas model for air

I'm trying to calculate the heat conductivity of a mold-polymer interface. I'm assuming that there's a thin layer of air between the polymer and the mold (gap conductance). According to some ...
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2answers
23 views

Heating a stock water tank

I am building an insulated cover to go around a plastic stock watering tank for the winter. I have no electricity in the pasture and don't want to axe ice in the tank all winter. I am building 3 sides ...
0
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1answer
84 views

When/How does thermal radiation stop (if it stops) and conduction starts?

Consider two solid objects in the vacuum (of different materials, if you will) at different temperatures approaching each other until they make "perfect contact" through flat surfaces (no gaps or ...
3
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0answers
65 views

Why does a salt water solution have a higher coefficient of thermal expansion (i.e. expands more) than distilled water?

I have found several different sources of data which show that a solution with a higher concentration of salt has a higher coefficient of volumetric thermal expansion than a lower concentration salt ...
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0answers
21 views

modeling heat transfer in a non-hollow cylinder starting at r=0

I have 2 questions about the heat equation in a cylinder that involve the behaviour at $r=0$ and the boundary conditions. But first a little more context: I want to model a reaction in a cylindrical ...
1
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1answer
86 views

Derivation of thermal conductivity of a solid body

I am reading a german physics book called "Festkörperphysik" written by Gross/Marx. And I came to following situation: $$\frac{d\langle n\rangle}{dt}=\frac{\partial\langle n \rangle}{\partial t}\...
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3answers
60 views

How do phonons impact the way heat is transferred between two solids?

If we assume that in a system heat is only transferred by conduction (between two different solid of different materials), what role do phonons play in this phenomenon?
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1answer
49 views

Viscosity Vs Conduction

Viscosity of a moving fluid (e.g. a gas) is commonly related to the exchange of momentum between layers of such fluid moving at different velocities. Intuitively, one could think that in a gas such ...
0
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1answer
97 views

Understanding boundary conditions in heat transfer

In the context of heat transfer, how does one physically interpret the following boundary conditions: $$ u \cdot \mathbf{n} = 0, \qquad \frac{\partial u}{\partial \mathbf{n}} \cdot \tau = 0 $$ where $...
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0answers
45 views

Heat transfer: Can I model layers as homogenous medium?

I'm a nerd preparing to build an earth-bermed concrete house in a cold climate. Before involving the professionals, I want to refine the design to minimize long-term insulation and heating cost. I ...
0
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1answer
35 views

Are there any thermal insulation equation that uses change over time and temperature?

I'm currently working on a science experiment to find out whether the thickness of a material affects the insulator's ability to insulate, and if so, to what extent. I've set up an experiment where ...
0
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0answers
112 views

Convert `w/m K` to Tog?

Im trying to work out some calculations for an underfloor heating system (UFH). Basicly i need to have a floor finish over the UFH with a a Tog <2.5. The floorings thermal resistance is ...
1
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1answer
88 views

Combined radiation with conductive and convective heat transfer

I have a tube(only the cross-section displayed in the figure!), where gas flow is used to heat up the water. The water flows inside the steel tube, where the walls have been marked red. The heat ...
1
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2answers
122 views

What material is best suited for eating ice cream from, without the ice cream melting too fast on the edges?

When I buy some ice cream from a parlor or get some from the supermarket I find that the containers (also the standard bowls I can find in my kitchen) are not perfect for eating ice cream from. The ...
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1answer
27 views

temperature of each layer of a cooler

I have a cooler with five layers and I know the temperature outside and inside of the cooler. I created a Matlab model that demands me the temperature of each layer of the cooler. I want to know how ...
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1answer
40 views

Confusion about Thermal Resistance and Heat Distribution

I'm trying to understand the flow of heat between electrical components and circuit boards, and I'm having some trouble understanding some basic concepts. Suppose I'm considering a chip with a $\...
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1answer
30 views

Thermal Conductivity Conversion

I need to convert a thermal conduction unit W/m.K to Btu/ft.h.°F. I have 400 W/m.K and I ...
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0answers
35 views

What is the thermal resistance of a hollow cylinder to heat flow in radial direction considering that there is heat generation inside the material

http://www.cdeep.iitb.ac.in/webpage_data/nptel/Mechanical/Heat%20and%20Mass%20Transfer/Conduction/Module%202/main/2.6.2.html shows the same for a composite hollow cylinder, by assuming there is no ...
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1answer
208 views

Minimum Thickness of Insulation of a Pipe

We know that there is the critical radius of insulation where heat transfer is maximum at that radius. Heat Transfer vs Insulation Thickness]1 From the graph, we can see that as long as the radius ...
0
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1answer
63 views

Refrigerant vs water heatpipe [closed]

For a heatpipe that is connected to a 50 Celsius object on one side,and a heatsink at 23 Celsius air at other side, what fluid filling will give better heat conductivity? Plain water, or some kind of ...
2
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1answer
85 views

Revisiting the choice of tungsten in light bulbs

I admit questions around why tungsten is used in light bulb tend to be very common, but hopefully what I'm asking here is not a duplicate. I am trying to understand which properties of tungsten make ...
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4answers
2k views

Why are compressed air tanks cold? [duplicate]

Why is a compressed air tank cold to the touch when it’s in a compressed state before use?
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2answers
289 views

Prevost Theory of Exchange

I am having a trouble in understanding this concept. If bodies are at thermal equilibrium, there is no heat transfer. Heat is transferred through three different ways: Conduction, convection and ...
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3answers
42 views

When is a slab said to be in a steady state?

The steady state is distinct from thermal equilibrium for which the temperature at any position of a slab must be the same. Could anyone explain this line to me?
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0answers
56 views

Comparison of emissivity and absorptive power of two bodies from temperature vs. time graph

How can one compare the emissivities and absorptive powers of two bodies from the temperature vs time graph if both have same initial temperature? For instance body A and B in the attached image
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3answers
183 views

Does heat transfer happen instantanoeusly in a perfect harmonic crystal?

A perfect harmonic crystal (PHC) has infinite thermal conductivity (see here for example, or also (1)). Does this mean that in a PHC there is instantaneous heat transfer? Fourier's law would seem to ...
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2answers
42 views

Subtract thermal resistance of material from thermal output of heat source [closed]

Im trying to work out the heat output of a under floor heating system. The underfloor heating system has a stated output of 80w/m2 (watt per meter squared). This is for the system installed with no ...
6
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1answer
135 views

How do I calculate how long water will take to warm from 22°C to 35°C?

I'm a microbiologist and my physics is not up to par for figuring this out. I've requested our engineering department to perform a temperature mapping of the vessel, but they can't do it for me. I ...
2
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1answer
415 views

Do conventional ovens heat by thermal conduction or radiation?

I am curious which energy transfer mechanism dominates in a conventional oven, thermal conduction or thermal radiation? A naive guess would be that early on, when the food is still cold, the heat ...
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1answer
59 views

Heat that we feel [duplicate]

I have just came across a site saying that when we touch a good conductor and if it's temperature is a lower than our body we feel it cold as heat starts flowing from our hands to it. On the other ...
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1answer
117 views

What can I do to be invisible for the IR-camera on board of a police helicopter? [closed]

I think we all have seen the images of crime suspects, running in the dark of the night to escape the police, made with the help of infrared cameras. What can I do to be invisible to these cameras ...