Thermal conductivity Definition and 185 Threads

TL;DR Summary: Trying to understand why there might be errors when using certain materials in a physics lab and how aluminum foil might impact this. I am looking for assistance on answer these questions. 1) What would likely be a significant source of error in performing this experiment on...

What'd be practical method and/or portable, simple tool (like sort of electricians' multimeter) to meter the heat conductive constant of a metal?

Whats its thermal conductivity compared to copper? (as in x times worse than copper) also, How electrically insulate is it? I'm looking to see if i can use it to encase an entire motherboard in a giant heat sink for a future project where i want to try and cool the entire motherboard to subzero...

The problem gives these data external (cold) air temperature: ##T_c = 20^\circ{\rm C}## internal (hot) air temperature: ##T_h = 80^\circ{\rm C}## lantern volume ##V=0.2 {\rm m^3}## lantern surface ##A=2.0 {\rm m^2}## lantern mass ##m_{\rm L}=30 {\rm g}## external convective heat transfer...

I know k is thermal conductivity but my teacher never told me about effective coefficient of thermal conductivity. I tried googling and found: $$k_{effective}=\frac{\Sigma{k.A}}{\Sigma A}$$ But I don't know the area to used that information. Is there another approach to do this question? Thanks

I've tried to explicitly solve the Fourier's equation in cylindrical coordinates but I'm getting some messy integrals which cannot be solved analytically. Additionally my instructor said that there's a neat trick for this problem and it's possible to obtain the answer in a rather elementary...

Good afternoon everyone! I've learned that thermal conductivity has a form of second-rank tensor. As you know, diagonal components of stress tensor mean normal stress and other components mean shear stress and like that do off-diagonal components of thermal conductivity tensor have some special...

When we measure 'the rate of conduction heat transfer'=Q , we assume that the hot side and the cold side's area are same. But if the both side's area is different to each other, how can i know the rate of conduction heat transfer? like below figure. Would you like to help me?? Thanks.

We know that, Conduction Heat Transfer Q = KA(t2-t1)/thickness K is the coefficient of thermal conductivity. If T2 = 1020°C and T1= 22°C also consider we know A and thickness value. K depends on temperature. K varies with temperature. For all the materials we have a tabular data of K for...

Hello, I'm searching for how magnetic field affects the thermal conductivity of the metal (such as steel in solid form). If someone suggests any article about it will be very helpful.

Here is the Q below I want to see if my values for part b) is okay? This is what I have tried: Any help would be nice! Thanks

I'm trying to find a heat transfer equation that includes time. Metal tank, partially filled with liquid. I need to find the time it would take for the temperature on the outside of the tank to drop from θ2 to θ1, given thickness, metal and liquid's properties, and tank dimensions

Overall thermal conductivity? for example, there are 3 layers made of different materials, having different thermal conductivities bonded with each other; conductivity of layer 1= k_1 = 1 W/m-K thickness of layer 1= t_1 = 0.004 m conductivity of layer 2= k_2 = 148 W/m-K thickness of layer 2=...

I worked on a lab experiment that was meant to measure heat capacity but left me with some other questions. The students measured the mass of a cup of liquid nitrogen as it boiled off, recording mass vs time. Then they drop a solid object into the bath, one experiment with a small bit iron...

A) What are the modern techniques used for enhancing the thermal conductivity of Phase changing materials (PCM) ? B) what are the negative effects (disadvantages) of using old methods of enhancing thermal conductivity of PCM ? ( construct table ) C) what are the different techniques used for...

Hi, yesterday a professor of mine told me that if you have a temperature gradient along the x-axsis you could have heat flowing in the y direction. Mathematically it is pretty straightforward to find the thermal conductivity tensor required, but in real life can you name some materials that...

$$\frac{\partial T}{\partial t}=\alpha\frac{\partial^2 T}{\partial^2 t}$$ with an initial condition and boundary conditions $$T(x,0)=T_0$$ $$T(L,t)=T_0$$ $$-k\left.\frac{\partial T}{\partial x}\right|_{x=0}=2A\cos^2\left(\frac{\omega t}{2}\right)=A(\cos\omega t+1)$$ where $A=V_0^2/(8RhL)$...

Suppose that a large mixture of ice and water is in thermal contact with a reservoir which contains a large quantity of water and steam. Assume that both the ice/water bath and the water/steam reservoirs are otherwise thermally isolated and at a constant temperature. The only contact between...

Hello! I am a materials engineering BSc student currently writing my bachelor thesis. The topic of my thesis is regarding the PV/T system and the best material choice for the interface between the glass/glass PV module and the heat mat. I would appreciate any ideas for material with best thermal...

Homework Statement Hello, As part of my engineering orientation class, my team and I have to make a device that can keep a beaker of water warm. We have a list of materials we can and cannot use, but my team and I have decided on aluminum foil and maybe wood. We don't actually have to build...

I am working on a project; a computer case made out of wood, most likely oak. I was wondering if two fans (one bringing air in, on taking air out) would be enough to keep the system at a stable temperature. I wasnt sure because i know most cases are made of thin metal which conducts and...

Hello, my name is Stephen Lanford and I am currently working on a Physics II lab. I am solving for the thermal conductivity of four materials (glass, plexiglass, pine, and sheetrock) using data from thermal conductivity experiments. The experiments consist of a steam chamber at 100 C, a block...

Phonons on their own lead to the common heat equation. One sees that for example in insulators or non doped semiconductors. However in metals (or conductors), the electrons are the ones that are mostly responsible for the heat transfer, which extremely surprisingly to me, is also of the form of...

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 defects, so that thermal contact conductance effects are absent, even though interfacial thermal...

Hello, Just a quick question if I have a let's say a heat source of under a layer of bricks that have a thermal conductivity of 1.6 (W/m/°C.) and on top of the brick a layer of copper with a thermal conductivity of 398 (W/m/°C.). Is my assumption right that since the layer of brick has such a...

Progress This is the experimental data of thermal conductivity of stainless steel 304L at low temperature. The data is calculated with the Fourier's law of thermal conduction. I checked many times in the excel file and I confirmed that there is no mistake in the calculation. The parameters are...

Homework Statement Hi there, I am designing a heat exchanger and I am really struggling to find out how to fairly accurately estimate the density, viscosity and thermal conductivity of a gaseous mixture at ~~20bar. There is 8 components in the mixture: methane, ethane, ethene, ethlyene oxide...

Question#1 I would like to compare a 100' length of 4" PVC pipe with air in it surrounded by Earth and/or water. What length of 4" copper pipe would equal a 100' length of PVC? Question#2 If the inside of the pipe had turbulence what length of non-turbulent 100' PVC 4" pipe would it equal? I...

HI, I have application where i need to lift metal plate, 3kg weight, ( 3mmX 15mm), 250degree.C hot, for the period of 1min and put it back. For lifting purpose i am using actuators. As i have no opportunity to make hole in plate i have to use magnet for lifting purpose. I got Electromagnet...

Homework Statement I must calculate chemical potential using the Boltzmann equation in relaxation time approximation $$f=f^0-\tau v_z^2 \partial f^0/\partial z,$$ where ##f^0## is given as $$f^0 = 2(\frac{m}{2\pi\hbar})^3 \frac{1}{\exp{\beta(z)(\frac{mv^2}{2}-\mu(z))}+1}$$ I have to consider...

Does the phonon thermal conductivity account for a large part of the total thermal conductivity in thermoelectric materials like Bismuth Telluride? As far as I know, the phonon conductivity is the largest contributor to the total thermal conductivity in semiconductors. Is this still true for...

Hi! I am using a Zn-Mg alloy (52% and 48% respectively) as a phase change material in a thermal energy storage system, but I have been unable to track down important properties, such as specific heats and thermal conductivity. Is there any way to approximate these relatively accurately given...

Homework Statement Homework Equations P = k A \frac{dT}{dx} The Attempt at a Solution a) Assuming steady state transfer, energy transfers through rods at the same rate everywhere. Letting T be the temperature at the point of welding. P_1 = k_1 A \frac{T_h-T}{L} \\ P_2 = k_2 A \frac{T -...

More thermal conductivity means there's more energy?...

Hello Physics Forums! My problem is as follows. I have a device that produces heat via Nichrome coils. I want to heat another small piece of metal (in this case stainless steel) with those Nichrome coils. I need to reach 175 degrees C, and so far I haven't found a readily available thermal...

1. Homework Statement I've been failing to find examples dealing with "longitudinal" thermal conductivity and how two objects in contact with each other would affect the heat flow compared to not being in contact at all. Problem: Given the following information, determine the thermal energy...

Homework Statement The problem is given. Homework EquationsThe Attempt at a Solution I tried to solve the question as if there is a nanowire between two reservoirs and got an answer. But I don't know what should I do to measure thermal conductivity in a thin film. My formula for k in a...

First of all, even I did mentioned Solar Cooker, the main goal is to reach most temperature of 500ml of water in 30 minutes. Basic information that I have is some material with different thermal conductivity. I seek for simple english language and a bit complex physics language. The idea of...

Hi Guys I was studying the thermal properties of SiC at high temperatures and now i have a few questions Usually, at high temperatures, the photons effect are much more intense than phonons at high temperature, correct? According to Rosseland heat diffusion equation Krad = 16σT3 /3β, β= 4πK/λ, σ...

Homework Statement Case 1: Which will boiling faster the container having steel ball dipped in it or container having only water? Case 2: Which one will attain thermal equilibrium faster? Consider balls are just in middle of the container. every condition of each the cases have same volume...

Homework Statement In each of the following, state and explain which container will have the hotter liquid after thirty seconds: a) You pour equal amounts of of hot coffee into two cup s from a percolator. The cups are the same general size and shape. One is made from heavy china one is made...

Homework Statement My textbook on lasers has mentioned thermal conductivity a few times, but hasn't specifically mentioned it's importance. I'm at a part talking about Nd:Glass lasers and it says that glass has a lower thermal conductivity than Nd:YAG lasers, which prohibits continuous wave...

I'm designing an oven and want to ensure that the insulation I specify has a low enough Thermal Conductivity (k) to resist excessive heat loss. I determine heat loss (Hout)with the following equation: Hout=A*U*(T1-T0). U is dependent on k (U=k/L). I omitted the heat transfer coefficient in...

Homework Statement I would like to derive an equation that relates the thermal conductivity to the pressure using the kinetic theory of gases. However, I assumed that thermal conductivity was independent of pressure. Homework Equations I know that P = 2N/3V (1/2mv^2) Also: I believe that...

How does insulator's density affect its thermal conductivity? For example, considering such insulators as rock wool, It seems that the thermal conductivity should increase with an increase in density (due to elimination of 'air pockets'). However, experimental results, in many cases, look more...

Hello friends, I am having a hard time understanding thermal conduction and was hoping someone could shed some light for me. I am looking to protect a component from heat by placing a thermal barrier between it and the heat source, the heat applied to the surface of this barrier would be...

I have a question that I've been debating with some co-workers. We are using conical springs (tapered) that most of the time in our application fully compress once engaged. We are measuring minute changes in temperature and I was wondering if a spring diffuses more heat compressed or relaxed...

It is a thought I just thought of with all the wonderful attention that climate change has been getting recently. The thought goes as follows: The world has ever increasing entropy as the whole universe has so. With humans adding to this effect even if green house gases curbed due to this...

Wood and Copper are heated upto a steady state condition which will have a higher average of temperature at points ? Please state your mathematical approach 1. Homework Statement Dimensions remain same for both the materials as well as the temperatures both are heated to is the same Homework...

How to calculate K or Q without one or the other? For example, if the material is unknown (but cannot test density, or melting temperature) how would you test heat flux? Q=K(Th-Tc)/(x)