> Well, I have done some more digging around on the internet and found a
> bit of information, but nothing that leads me to find the holy grail for
> my setup.  It seems that I have 2 options:
>
> 1) heat a to the temperature I want b to be heated up to and then keep a
> constant there until b reaches the same temperature
> 2) heat b to a higher temperature than I want b to be at and then let it
> cool down while b heats up with the heat given off by a until eventually
> both reach the same temperature
>
> For whatever reason (maybe the wrong one) I think that the second
> approach will be faster than the first, but also a lot harder to do
> without some magic formula to get some ball park values to play with.
>
> I am willing to experiment, as this should be quite fun to do just like
> physics class in high school (I never got to go to college).  But before
> I embark on a fun filled Saturday, are there any other ways to do this
> (better or worse)?
>
> Thanks.
>
>
> -Mario

In method 1, if you keep the outside fluid at the desired temperature, the
inside fluid would eventually reach that temperature. The amount of time
it takes is based on the thermal resistance of the container of the inside
material and the heat capacity of the inside fluid. You also have to
consider the heat capacity of the container around the inside fluid,
though this may be small compared to the heat capacity of the inside
fluid.

I'm assuming this double fluid method is so you don't have "hot spots" in
the inside fluid where the temperature is non-uniform due to hot spots on
its container. It seems this could be avoided by using a container that is
highly conductive (copper) and spreading a heater around it. A thin
plastic coating could protect the inner fluid from contamination from the
copper while having minimal thermal resistance.

Back on the two fluid approach, can you put a temperature sensor on the
inside fluid? If so, you can then tune a PID control loop to quickly get
the temperature where you want it to be without overshoot. Again...
experimentation!

Good luck!

BTW, my junior high science fair project was about heat capacity. I ran a
submersed electric heater of a known wattage for a certain number of
seconds and observed how much the water temperature increased. That was
something like 45 years ago...

Harold

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