Run 3 of our 2nd attempt to replicate the Mizuno-Ohmori Incandescent W Excess Heat Effect - 4JUN99
The most significant change for Run 3 was the addition of a mechanical stirrer, similar to that used by Mizuno. In this photo (taken just before Run 3 started) you can see the new stirrer hanging down into the cell near the W cathode. The stirrer itself is a 6.35 mm dia TFE rod with three 3.2 mm dia TFE rods pressed into tight holes in the larger rod. These are the only stirrer parts that contact the electrolyte.
Here you can see the rest of the stirrer. A small DC motor is mounted to the top of the cell and the TFE rod just extends down through a hole in the cell cap. A bushing made of PVDF has been pressed into the cell cap to provide a lower bearing for the TFE rod.
A satisfactory stirring action was obtained with 6.5 volts on the DC motor. At that voltage the motor drew about 60 mA. Total stirring power was therefore 0.4 watts...negligible for this experiment.
This photo shows the new cell, with stirrer, sitting in the calorimeter heat exchanger before the calorimeter was closed. You can't see much of the cell because it is hidden inside the coil of Cu tubing.
The small amount of water visible in the outer beaker serves to couple the cell to the Cu tubing. Normally the outer beaker is almost full but, for Run 3, we lowered the level to about 40% full as you can see in the photo. This reduced the coupling between the cell and the Cu tubing allowing the cell to run hotter for a given input power.
Results:
The color legend and vertical scales for this plot are as follows:
Pin
(0-200 watts)Pout
(0-200 watts)Tcell
(0-100° C)Vcell
(0-200V)Icell
(0-5A)Tin
(39-41° C)The horizontal scale covers 3 hours.
The run starts with about 1.2 hours of equilibration time. During this time Pout closely approached zero (not visible since the approach was from a negative value) to within 0.5 watts. At 1.2 hours, we began stepping up the voltage in 5 volt increments (one step every 15 seconds) to acquire the I vs V data for this cell. During this process, the
Pin (supplied by an EMI 150-10 power supply and measured by our Clarke-Hess 2330 Wide Bandwidth Power Analyzer) rose sharply and briefly exceeded 200 watts. However, once the gas sheath began to develop around the cathode, Pin dropped sharply to about 120 watts. For this run we continued stepping up the voltage (Vcell) to 140 volts and then left it there for about 25 minutes for the calorimetric measurement. As you can see from the Pout trace, the observed heat output power rose up and leveled off at a value very nearly equal to Pin, indicating no significant excess heat generation. During this time, the cell temperature (Tcell) stayed right around 90° C.NOTE: As soon as the cell temperature started rising, the stirrer began having problems. At the full operating temperature of 90° C, the stirrer was running at a small fraction of normal speed (deduced from observation of the motor current waveform). We believe that thermal expansion caused the PVDF bushing to bind on the TFE shaft. We plan to modify this bushing for the next run but this fact remains: the stirrer was hardly working on this run.
This plot shows the I vs V relationship for this cell during Run 3. Also plotted is the cell temperature for both the increasing V and decreasing V legs of this plot. This plot is closer to Mizuno's in one respect...we got up to a significantly higher current density (~5.5 A/cm2) before the decline started. Perhaps that is due to the fact that the cell temperature was only about 65° C then.
The cathode from Run 3 is on the left. A new cathode is on the right. The streaky appearance in the dark areas of the Run 3 cathode is due to the black deposit simply falling off of the cathode during rinsing with distilled water. Note that the edges of the cathode are relatively clean. That's where the majority of the spark discharge flashes occur.
The end of the TFE/FEP sleeving is charred. This is not surprising as the cathode was orange hot during Run 3. Perhaps some of the black deposit comes from the TFE/FEP sleeving.