# HELP! Calculating temperature change over time

1. Oct 29, 2009

### Fancy Moses

If I have a heating source that gives off constant single temperature heat which heats a mass of insulator, next to a mass of ice, next to a mass of cold water - how do I predict through calculation the temperature change over time of the water? I know the original temperatures, surface area, thickness of each mass, and the given temperature of the heating source (which is constant). Overall the goal is to change the masses/surface areas to achieve a certain end temperature for a given duration.

If you have any ideas it would be a real help!

Thanks

Last edited: Oct 29, 2009
2. Oct 29, 2009

### Fancy Moses

Any response would be nice... anyone with some good background in thermodynamics possibly. Perhaps a "It's quite difficult to do" or "Here's where to start"

Anybody?

3. Oct 29, 2009

### minger

Do a google on "thermal resistances". You can model each piece or block as a resistor. You can then place them in parallel and find the total heat flux. The heat flux through any single piece is then equal to the total via continuity. You can find temperatures that way.

If you want it as a function of time though....it will be substantially more difficult.

4. Oct 30, 2009

### ank_gl

Hi Fancy Moses,
You should start by making a neat sketch. Then assume a one dimensional(depends on the problem) heat flux, use heat transfer equations to formulate the linear equations, solve the linear equations.

Mind the bold text.

5. Nov 17, 2009

### Fancy Moses

Thanks for the help!