Some excellent points.
Even a chiller may have fluctuations, it really depends on each unit.
Rads do have a predictable response, but it depends on more than one element: airflow rate, coolant flow rate and temperature differential.
So from my perspective, it would be technically possible, although admitedly very difficult, to use a rad fan combo. The largest issues with it, is that the circuit may need to have a pretty quick response time, and that response needs to fall "in tune" with the rad/fan combo's response.
So to build something like this, might require a very accurate and quick response temp probe, just to tune the thing!
Either way, the "cooling solution" must be able to maintain the same temperature, and handle a heatload of more than 70 Watts. (Are we going to test 100W?)
So I'll ask the questions now:
-What kind of temperature fluctuations are acceptable (ex: speed, shape, form)?
-What rate of fluctuation would be acceptable (ex: +/- 0.1 deg C, with +/- 0.1 deg C/second)?
-If there's a fluctuation, but the average is still maintained, are we still OK?
-What exactly is the effect of having a fluctuation?
Then I've got my own questions:
-What is the effect of "relative humidity" on the testbed?
-Could it affect a circuit, such as described above?
-Alternatively, could we use a mixing valve, to mix hot and cold water, to get to that temperature? (answer: it depends on the response time of the valve)
-Are we testing at ambient +5 deg C, regardless of the room temp, or should we require a specific room temp, or a specific range of room temps? What's the difference?
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