Simplified analysis to compare materials, for different limiting-case applications, given the same geometry:
- Want max heating ramp rate, with fixed-power electric heater -- minimize Volumetric Heat (i.e. specific heat * density)
- Want max cooling ramp rate, with fixed-temperature coolant -- minimize (VolumetricHeat / ThermalConductivity)
- Want best control performance at/near steady state -- maximize Thermal Conductivity (and possibly thermal mass, but depends on location and nature of noise in thermal load)
Aluminum 6061-T6:
- density (g/cc) = 2.7
- specific heat (J/gK) = 0.9
- volumetric heat (J/ccK) = 2.43
- thermal conductivity (W/mK) = 167
- CTE (ppm/K) = 24
Copper, pure:
- density (g/cc) = 8.9
- specific heat (J/gK) = 0.385
- volumetric heat (J/ccK) = 3.43
- thermal conductivity (W/mK) = 385
- CTE (ppm/K) = 17
Edit #1, from OP @jay
- If the volume of the pipe was the same, aluminum would be more effective delivering the heat from one end to another. If the weight of the pipe was the same, copper would be more effective.
- Since, the length/shape of the pipe is constrained by the mechanical structure, the volume matters more.
- Thus, I would choose aluminum pipe, if I have good trust in my controller.
- I would choose copper pipe for less influence from disturbance (ex. from ambient), if the performance of the controller was excluded from the considerations.
Edit #2 from OP jay
However, in practice and mechanical design perspective:
For 2, if you are building from pipe/tube, there are a finite number of specific options wall thickness. So just make a table of the bulk heat capacity in J/K for the options you have given mechanical constraints. That will inform the remaining analysis, but is not necessarily the performance limiting factor. Often not.
Regarding effect of controller, it depends on placement of heater and sensor.
If you are not sure what you are doing, then a big thermal mass with a slow response might actually be more practical than something light and aggressively tuned.
