# Specific Heat vs Thermal Conductivity

1. Apr 8, 2009

### Physics_Kid

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

2. Apr 8, 2009

### Bob S

Is there a relationship? Factoid: How about the The Wiedemann-Franz Law for electrical and thermal conductivity. The ratio of the thermal conductivity to the electrical conductivity of a metal is proportional to the temperature. Qualitatively, this relationship is based upon the fact that the heat and electrical transport both involve the free electrons in the metal.

3. Apr 9, 2009

### maverick_starstrider

The answer to that question is highly dependent on the substance we're talking about. It depends if we're talking about a metal, semi-metal, insulator, semiconductor, etc and whether we're interested in the electronic contribution, phonon contribution, etc.

4. Apr 9, 2009

### Physics_Kid

i just mean in general, for any substance.

such question relates to "what makes a good heatsink".

for me, a good heatsink is one that can move heat well two times. 1st it should be able to pull heat away from object A, and 2nd it should be able to transfer that energy to a second medium (typically air, but can be anything that carries heat away from the heatsink itself).

so the main characteristic for choosing the best heatsink would be thermal conductivity. but what is TC? for solids a measurement of energy conduction from atom to atom, there is no net movement of atoms in solids. for liquids TC involves both conduction and convection.

in all cases TC is directly related to temp differences between two areas, which causes a energy flux (a net movement of energy through such area).

so a good heatsink must facilitate a temp difference to get energy to flow. so how does specific heat play a role? a high specific heat means the heat sink can absorb lots of energy with little temp rise. is this good for a heat sink? to me it looks good for the 1st step, but doesnt look so good for the 2nd step (getting heat away from the heat sink, etc). if the heatsink has high specific heat this means the temp diff between the source (object A) and heatsink itself remains high while the heatsink absorbs energy, but conversely the temp diff between the heatsink and air remains low thus little heat flow out of the heat sink.

what i have found from documentation is that TC varies widely when compared to specific heat. why is this?

copper Cp is about three times less than aluminum, yet copper k is about double that of aluminum.

beryllium Cp is about double that of aluminum, yet the Beryllium k is only slightly higher than aluminum.

Last edited: Apr 9, 2009