# Thermal Conductivity Sum

1. Feb 28, 2007

### Xeract

I think the answer is yes, but I just wanted to check.

If you have several sheets of different material, is the total thermal conductivity the sum of the individual thermal conductivities?

2. Feb 28, 2007

### Mentz114

I think you're wrong. The conductivity of the laminate is more like the capacitance of capacitors in series. The total conductivity can't be more than the lowest value in the laminate.

3. Mar 1, 2007

### Xeract

I was modelling the conductivity on resistors instead of capacitors. Surely the higher the thermal conductivity the higher the "resistance" to heat flow so they should be modelled as resistors?

(I could be completely wrong on this)

4. Mar 1, 2007

### Mentz114

You're right about the resistors. But conductivity is the inverse of resistance,
so the addition ( for equal thickness layers) looks like,

$$\frac{1}{C_{tot}} = \sum \frac{1}{C_i}$$

which reminds me of capacitors. I could also be wrong.