Thermal conductivity Definition and 173 Threads

Homework Statement we have a metalic bar with thermal condutivity of 200w/(m*k) it has an area of 20 cm^2 which is in contact with with an heater that delivers 200 W and is at 300ºC. the metalic bar has a thickness of 1cm The two questions are: a) once the system have entered a...

How do I go about deriving the thermal conductivity of graphene (specifically, in the low temperature limit) when I'm given the phonon dispersion relation? I haven't been able to find anything explaining how the dispersion relation relates to the thermal conductivity in materials. (this is...

I mean how can i analysis the thermal conductivity of two structures with their phonon spectrum. thank you!

Homework Statement i need to find the thickness of the insulating material that is needed to block out the heat that is coming into the room. the area of the affected wall is 3.3m2 the temp in first room is 18 degree celsius while the 2nd room is 45 degree celsius. the thermal...

I understand that thermal conductivity is W/(m.K) and u-factor is W/m² K. Obviously U factor is energy transfer over an area but how does this compare to thermal conductivity?

Hi to all Can some one help me for below question: What is different between "isotropic thermal conductivity" with " anisotropic thermal conductivity" ? where and when we must use isotropic or anisotropic ? which one is more accurate? I solve an example in a FEM software and it is...

Thermal Conductivity , k , for water is .1455 cal/sec/ meter * C ( converted watts to cal/sec) Q/t = k* A delta T/ d A= area M2 d = thickness of water/ice boundary layer Suppose I want to calculate time for 100 grams of ice to melt ( 8000 calories absorbed from surroundings by conduction. I...

I'm currently running RELAP5-3D to model a molten salt reactor and I require the thermal conductivity of graphite. Is there anyone that is aware of this value, or can inform me of a proper resource? Thanks!

We have a customer asking us for the thermal conductivity of a product we sell. None of the engineers have that number. I can think of a simple experiment that might do it, but I don't know the math. I want to take a piece of this material (it's a pipe), put a cap on the bottom, then...

Hey everyone! Got an interesting problem here, I am thinking I did it correctly but I wanted to see your opinions. Here is the problem.. A 0.2-m-thick plane wall is constructed of concrete. At steady state, the energy transfer by conduction through the wall is 0.15 kW/m2. The inside...

Homework Statement Ice has formed on a shallow pond, and a steady state has been reached, with the air above the ice at -9.6°C and the bottom of the pond at 5.5°C. If the total depth of ice + water is 2.1 m, how thick is the ice? (Assume that the thermal conductivities of ice and water are...

Homework Statement solve d/dx(kdT/dx)=0 where k is linear function of temperature k=k(0)(1+BT) Homework Equations this is the solution T+BT^2/2=Ax+C The Attempt at a Solution i opened the equation so that it becomes equal to dk/dx*dT/dx+kd^2T/dx^2=0 i subtitute the...

I'm working on a model that needs to calculate the approximate thermal conductivity of a mixture of gases. I'm having trouble finding a model which is being used by one of my sources but is not cited and I can't seem to find a source for it. I'm hoping that someone here might recognize the model...

In the case when heat is flowing at a steady state through two materials with different thermal conductivities, the classic Q/t = A(T2-T1)/ L1/k1 + L2/k2 applies. In this case T2 is fixed and the two different k values are combined. In the case of cooling , Newtons...

I am trying to decide what alloy I should use in an experimental heat transfer device. I am considering 2 materials- 304 Stainless Steel and SAE 516 Grade 70 boiler steel. I want to choose the material that has the best conductivity characteristics. To be clear, I want the material that has...

Homework Statement Design a portable container that will keep medicines at around 4 degrees celcius for at least 12 hours. Homework Equations Fouriers law, q=kA(T1-T2/L) Thermal Resistance=L/kA q=heat transfer rate (in W) K=thermal conductivity (W/M*degrees C) A=cross sectional...

Homework Statement Rod of cross sectional area A and length l has its left end held at constant temperature t1 and its right end held at t2<t1. If the conductivity varies with distance from the left end, x, according to the relationship k= x/R + k0 (R and k0 are positive), what is the steady...

HI I would like to test the thermal conductivity of r wall by K=Q*d/ A (t2-t1) K =conductivity d+=thickness A= area Q= heat flow my problem how I could simulate heat in my experiment and how I will measure the heat flow? could you please help me. Kind regards

Exterior commercial frames (.053") embedded in a concrete wall 8" thick with 3" layers of polystryrene (3# density) on each side of concrete cavity. Frame rests on foam inside and outside of building. Frame is grouted solid with poured in place concrete. Is there an appreciable (to be...

Hi :) I'm having difficulty with finding the relationship between specific heat, c, and thermal conductivity, k and cannot answer these questions - Six objects are placed in a 500 F (260 C) oven and allowed to reach thermal equilibrium. Each object has a mass of 1.0 kg . The specific heat and...

Homework Statement This is my first post on these forums, this problem is part of a lab and its part my end of year result but we never did anything on it in class so i have'nt a clue how to do it. Help would be really appreciated The handle of a freezer door 12cm thick is attached by two...

Homework Statement A wall is insulated with glass wool of thermal conductivity K = 0.046 W/m oC. What is the rate of heat loss (in W) through an area 1.0 m wide by 1.5 m high, insulated with a layer of glass wool 20 cm (.2 m) thick, if the temperature difference across the layer is 20.0 oC...

Homework Statement A Cylindrical Tube of Length 35m, inner radius = 2.5m The tube is lines with 6cm thick insulation where k = 4X10^-5. The inside temp=25 degrees celcius Find the rate of heat delivered if the outside is -35 degrees celcius which keeps the inside temp at constant 25...

Homework Statement The passenger section of an airplane can be thought to have a shape of a cylindrical tube. For a small airplane, the tube is 35 m long and has an inner radius of 2.5 m. The exterior of the tubular wall is lined up with a 6- cm thick layer of insulating material of thermal...

Homework Statement To summarize, I am given 6 objects and their corresponding specific heat capacity and thermal conductivity values. All objects have the same mass. The question is asking me to rank the objects based on temperature if they are put in a hot oven until they reach thermal...

Is it possible to calculate thermal conductivity of a material given just the delta-T at steady state and the material thickness? I have material that is 1/2 inches thick and has a 145 degree-C diffential @ 220C. Can I calculate its k-factor from that data alone? Thank you.

is there any corrolation between thermal conductivity coefficient and molecular wieght Mw according to the units [K] W/(m·K) it is independant of mass units (kg or g/mol etc) in my question i am asked to show with a graph, but i have no idea what graph they are talking about

Hello! I'm writing an essay on 'relationship between density and thermal conductivity'. Could anyone explain to me the relationship? e.g. is it proportional or reciprocal? I'm kind of closing to the answer by doing an experiment. I took two concrete blocks with different densities and got...

Hello! I'm writing an essay on 'relationship between density and thermal conductivity'. Could anyone explain to me the relationship? e.g. is it proportional or reciprocal? I'm kind of closing to the answer by doing an experiment. I took two concrete blocks with different densities and got...

Hi all In the following link it says: http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/thercond.html "For metals, the thermal conductivity is quite high, and those metals which are the best electrical conductors are also the best thermal conductors. At a given temperature, the thermal and...

Hi all I'd like to heat up a mile of buried copper cable to roughly 100 deg C. The centre core is 80mm dia solid copper with impregnated paper insulation. Maximum spot temp is 150 deg C. I can expose the core at each end and clamp on a heating element. I've got plenty of time =...

hello! I'm investigating on thermal conductivity of concrete blocks. I've got an equation for calculating K, which is Fourier's law. Q'=-k×A× ∆T/l I have to make the experiment simple as possible as i can. My plan is to heat one side of a block of concrete and measure the temperature difference...

Hi all I want to convert thermal conductivity to thermal conductance. The problem is with the units. for thermal conductivity the units are [W/(m.K)] and for thermal conductance the units are [W/K] For E.g for copper thermal conductivity is 400[W/m.K] how can I convert it to thermal...

Help! Which has higher heat conductivity: water or air? And could you give me a proof as well? Regards, Quan Chi

Hi Everyone, I have a thousand data points that create a graph of Copper's Thermal Conductivity as it changes from a temperature of 4.5 K to 300K. These points create a somewhat bell-shaped curve, and I have been trying to find the equation to this curve so I can integrate it. I have...

a little guidance with thermal conductivity please... Homework Statement there isn't really a problem statement, as its a lab write up I'm doing. we had two blocks of the same metal, one at room temp and one at a fixed temp of almost 50 degrees. a Rod of different metal was put between...

can anyone explain the relationship between specific heat and thermal conductivity?

Homework Statement I have plate of glass pressed between a hot plate on top and a insulating surface below. The idea is to be able to predict the temperature of the glass plate and the thermal gradient through the plate as well at any time. I know the hot plate is at 400 deg F, that it is an...

hi, I would appreciate any help i could get on this, thanks. I've to estimate the heat loss from a person, immersed in water at 10ºC if he is wearing a 3mm wetsuit did anyone know how to process? thanks a lot jerem

Homework Statement One end of an insulated metal rod is maintained at 100^\circ C and the other end is maintained at 0.00 ^\circ {\rm C} by an ice–water mixture. The rod has a length of 75.0 cm and a cross-sectional area of 1.40 cm^2. The heat conducted by the rod melts a mass of 7.85 g of...

Hi, I have read that Thermal Conductivity means: “The thermal conductivity of a substance is the quantity of heat in cal/sec passing through a body 1 cm thick with a cross section of 1 sq. cm when the temperature difference between the hot and cold sides of the body is 1 deg. C.”...

Hello. As you can see, I'm new here. I have a little experience in physics and I've taken through Calc 2 in college. I'm trying to build a portable air conditioning unit. My current design consists of a tub of water with a 6" cube-shaped container of some kind submerged in it containing dry...

I 'trying to find the thermal conductivity of a silicon substrate doped with boron with known dopant concentration. Is there any way to calculate it or it has to be measured. Thanks in advance for any advice.

Strangely, this is for a Mat Sci Class. It is probably not as complicated as I am making it out to be, but the book has no suggestions on how to handle this problem. Homework Statement Calculate rate of heat loss through a fireclay refractory wall of wall with thickness .1m. Furnace...

Forgive me if I am posting in the wrong place. I have a problem dealing with thermal conductivity. I have an aluminum plate, approx. 12 in/ long, and 1.5 in. x 4 in on the end which is being applied with 200 W. What I'm interested in is how long it will take before the plate reaches a...

Homework Statement A mountain climber wears a goose down jacket 3.28 cm thick with total surface area 1.10 m2. The temperature at the surface of the clothing is -19.3°C and at the skin is 36.0°C. Determine the rate of heat flow by conduction through the jacket assuming it is dry and the...

Homework Statement A long rod, insulated to prevent heat loss along its sides, is in perfect thermal contact with boiling water (at atmospheric pressure) at one end and with an ice-water mixture at the other. The rod consists of a 1.00m section of copper (with one end in the boiling water)...

edit: not sure why this was moved to homework - it isn't. Hi :) I'm a bit embarrassed to ask this, but I hope someone can set me straight. As a second year university chem student I feel I should know this. In this question about thermal conductivity, I realize that it is a subject to itself...

Homework Statement It's not a homework problem, but an engineering problem I try to solve before I delve into experimentation :smile: I have a source of heat (SSR - a solid state relay) that's well thermally coupled to the inside of a steel box. The thermal resistance between the SSR and the...

Homework Statement A copper tube, of internal radius 6.959mm, overall radius 7.975mm, thickness 1.016mm, contains water at 68 deg Celsius, and is present in a room with an ambient temp of 26.65 deg Celsius. If the tube is 1000mm long, what will be the rate of heat transferred from the...