# Heat conduction

1. Jan 12, 2008

### PPMC

If heat is applied to one side of a cube, how can the temperature at different distances into the cube be calculated after different amounts of time have elapsed?

2. Jan 12, 2008

### mda

Have you tried looking at the wikipedia entry for heat conduction?

3. Jan 12, 2008

### PPMC

but the flow of heat isn't linear it will escape from the sides of the cube

4. Jan 12, 2008

### PPMC

well? how can i solve?

5. Jan 12, 2008

### rewebster

There's a lot of unknown variables:

What material is the 'cube' made from?

what is the temperature starting?--how much is applied?

is it in a vacuum?

is the heat applied to a side? (where on the side?) or to a corner of the side?

how big is the cube?

What is the method of applying the heat?

Last edited: Jan 12, 2008
6. Jan 12, 2008

### PPMC

its not in a vacuum, its in air, it starts at the same temperature as the surroundings, the heat is applied to one full square side of the cube. If the sides of the cube were insulate then i could use Fourier's law however they are not so heat will be lost as it spreads throughout the cube at a different rate as the heated surface area will increase. It should be possible to calculate but I can't figure it out....

7. Jan 12, 2008

### siddharth

Since you're building a mathematical model for this,

- What's the differential which governs the temperature of the cube as a function of time and distance?
- What is the boundary condition at each of the faces of the cube? Is the heat influx constant at one face, or is the temperature kept constant?

Check the relevant chapters in your text. It should have what you're looking for.

Last edited: Jan 12, 2008
8. Jan 13, 2008

### rewebster

I just tried heating a cube of butter....

9. Jan 13, 2008

### Staff: Mentor

I agree with siddarth. This is the basic heat conduction differential equation with some specified material properties and boundary conditions. Refer to your textbook on how to set up the problem.

My guess is that the resulting partial differential equation won't have an analytical solution and you will need to use a numerical solver. If you are familiar with matlab or mathematica they should be able to meet your needs.

Last edited: Jan 13, 2008
10. Jan 18, 2008

### TVP45

And, if you can accept an approximate answer, FEA is the easy way to do this.