Comparison of Cooling Rates Observed by Mizuno & Ohmori and EarthTech

Comparison of Cooling Rates Observed by Mizuno and EarthTech - 30DEC99

This plot shows the cooling rates observed by Mizuno (data from recent private communication) and Earthtech on similar electrolysis cells. The horizontal axis is cell temperature minus room temperature. Mizuno's cell cools approximately 2.7 times faster than Earthtech's does in still air. When a fan (producing an air speed at the cell of approximately 3 m/sec) is employed, the Earthtech cell cools substantially faster but still about 20% slower than Mizuno's cell. The physical data for these cells is given in the table below:

Cell Parameter	Mizuno	EarthTech
stirrer	?	yes (9 Hz)
material	quartz	quartz
diameter	56 mm	54 mm
height	150 mm	113 mm
wall thickness	3 mm	1.8 mm
total cylindrical surface area	313 cm²	237 cm²
electrolyte volume	150 ml	142 ml

The larger surface area of Mizuno's cell may increase its cooling rate somewhat. However, the depth of the liquid in both cells is about the same so the additional area in Mizuno's cell is mostly in the unfilled portion of the vessel above the liquid. The wall thickness difference should make Mizuno's cell cool slower.

This photo shows the experimental setup for the Earthtech cooling experiments. The cell is on the right, held in a three-fingered ring stand clamp. Immediately below the cell is the stirrer motor and magnet. The stirbar used in this experiment is 2.5 cm long and was rotated 9 times per second by the magnetic coupling and motor below.

The cell is heated to the boiling point by low voltage (below the plasma threshold) electrolysis. Once the cell has begun boiling, the electrolysis power is suddenly removed and the cooling curve data is subsequently recorded.

The fan is an ordinary household cooling fan. It was operated on HIGH speed for the fan-cooled test. As mentioned above the observed air speed was about 3 meters per second.