If you want the thermal mass to behave close to an isothermal body, diffusivity is very important.
For example, a large mass of still water has high heat capacity, but poor diffusivity. Much of the heat capacity is useless. -John ============== > At 04:18 PM 1/27/2011, J. Forster wrote... >>If you are considering conductivity for dynamic reasons, the correct >>figure of merit is "Thermal Diffusivity" >> >>= (Specific Heat) / (Thermal Conductivity) > > If you want a thermal mass to help control temperature swings, the more > heat capacity is good. Isn't more thermal conductivity also desired? It > seems like a substance with low conductivity wouldn't gather/release > heat well. > > If more of both is desired, shouldn't the figure of merit should then > be (specific heat * thermal conductivity), since you want more of both? > > In answer to the original question, which asked for heat capacity per > volume. One need only multiply the specific heat by the density. For > the examples given, plus iron and water: > > (substance) (specific heat) (density) (heat capacity?) > ( ) (kJ/kg K) (g/ml^3)(kJ/l K) > Al 0.91 2.7 2.5 > Cu 0.39 9.96 3.9 > Pb 0.13 11.36 1.5 > Fe 0.46 7.87 3.6 > H2O 4.2 1.0 4.2 > > So, copper is best, but iron (steel shouldn't be much different) is > pretty close and very much cheaper. Water is better and cheaper still, > but can be a bit messy. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
