Recently I have been modeling the HotCat in an effort to better understand the dynamic operation of the device. After a number of attempts I was able to construct a computer simulation that exhibits interesting characteristics.
There have always been questions concerning how a device that is driven by a power input signal, which integrates into heat energy, can be used to control the output heat power generated by the device. I have discussed that issue on several occasions and felt that now would be an excellent time to continue that dialogue. My latest simulation runs suggest that Rossi can deliver a product which has a decent COP provided he carefully implements the important parameters of his HotCat. The first criteria is to ensure that the internal power generation process is limited so that it never supplies more power at any temperature than is naturally conducted, convected and radiated away as determined by the geometry of his device. Radiation of power is proportional to the forth order of the absolute temperature of the surface area so it is not too difficult for this term to limit the high temperature regions of operation. I do not know the functional relationship between the power generated and temperature for one of his CATs, but must assume that the radiation ultimately will dominate the behavior. If this is not true then thermal run away will destroy the device. Earlier models apparently were subject to this problem, but the most recent third party testing implied that it is now under control. We also are aware that low temperature operation of a HotCat does not result in the generation of significant extra thermal power within the unit. Operation in the very low temperature region is the same as with a dummy system and that is fairly easy to demonstrate. Most groups attempting to replicate an LENR device can attest to the trouble proving that excess heat is being generated at the low end! The middle temperature region of operation allows for the most interesting conditions to occur. It is here that the internally generated power battles with the conduction, convection, and radiation paths in order to obtain the final operating point. Stable operation in this region can be achieved provided the geometry of the device is sound. Rossi can adjust the powder charge in both quantity and quality in his attempt to achieve his goals. If he adds more powder to the tube, then more heat power will be generated at a given temperature. Also, a better quality of mix that is more efficient will lead to additional power that needs to be handled by the design. The best combination appears to be established when the internally generated power comes very close to matching the escaping power at a temperature that is close to the point where the forth order radiation power component begins to dominate. There the magnitudes of the convection and radiation powers can be within the same ballpark. The convection power path ensured stability throughout the lower regions and finally the radiation takes over as the main path. Of course, for the task to be handled off it is necessary that the internal power generation term must exceed a linear function of temperature but remain less than the forth order dominance of the radiation. It would be great to have actual data that defines this power generation function, but it is not too difficult to understand why Rossi would not want to release that valuable information. I can adjust my simulation to handle a reasonable range of functions once it is released. The title of this posting was derived when I noticed that the simulated Rossi CAT follows a curve that is quite similar to what is seen during operation of a tunnel diode. You can substitute current in the diode for heat power of the HotCat. Diode voltage is substituted for temperature along the horizontal axis. The negative resistance region that the tunnel diode is famous for can be found in the HotCat curves provided the internally generated heat comes close to the thermal exit paths as discussed above. Of course it is entirely possible to design a HotCat that does not have this special region of operation but that would be at the expense of COP. My simulation demonstrates that this tradeoff is of enormous consequence where a COP of 10 or more rapidly deteriorates to being in the 2 to 3 range without the added boost. Perhaps that is what was intentionally done to the third party testing to keep the device stable and also to keep from revealing trade secrets. The effect is very sensitive to the output power per kilogram and quantity of the powder. It is important to realize that operation within the negative resistance region will take place naturally provided the design supports that behavior. This operation is indicated by the observation of a rapid increase in temperature with respect to time as the region is passed through. Charge reduction could easily be used to eliminate the dominance of this passage and that appears to be what was done to the third party test device at the expense of COP. The tunnel diode equivalence can be further expanded if one considers the thermal capacity of the HotCat as being simulated by adding a parallel capacitor across the diode terminals. My model includes this type of component which is required to handle the dynamic time domain behavior. There is plenty of information remaining to share but this report is become too long. I will continue to add results of my computer model and simulations in the future as time permits. Dave
