It is a bit more complicated than what your initial thoughts are Bob. If you consider that the total power that must be radiated, convected, and conducted away from the device is equal to the sum of the input plus the internally generated power, you will realize that if the input is eliminated then it is equivalent to adding another sink that extracts that much away. The input can be rapidly reduced and it takes time for something like a fan to come into serious play. I suspect that both approaches would be nearly equally effective.
The main issue of importance is how long is the time available for effective action and that depends upon several factors. The rate of increase in temperature leading toward melt down is not clearly known at this time since there was little indication that anything was going wrong in the latest test that I have seen. The rate should depend upon the effective loop gain of the positive feedback system as well as the thermal time constant through which it acts. The thermal time constant can be somewhat adjusted by the system mass. The heater wire is a part of that mass and therefore any heat energy remaining at the time that the input drive power is removed does not contribute to additional heating of the total mass but instead becomes part of the initial state that exists just prior to the turn off transient. My earlier models suggested that when the negative resistance region is breached much of the input power and core generated power are being absorbed by the thermal capacity of the system as the internal temperature rises. It takes a lot of joules of total heat to carry this rate of rise forward and that is the weakness that we can exploit. As soon as the input no longer makes a contribution to that net heating, the process ceases to proceed. The characteristic curve that I harp upon shows why this is so effective. If you take a system snapshot at the point in time at which the input drive ceases you will see that the output being radiated, etc. away remains the same. Since no more input power is included in that total, it must all come from the core generated power. This process causes the thermal capacity to become starved of the extra heat energy that it needs to continue to rise. As a consequence the temperature stops rising altogether and begins to fall toward ambient. The positive feedback works in both directions. When the negative resistance region was entered, the positive feedback reinforced the rising system temperature as it grew ever higher. Now, the positive feedback works in a direction that causes the temperature to fall ever faster with time. And, of course, this is exactly what is needed to save the device from melt down. The main trick I uncovered is to choose wisely the best time to cut off the drive power. Cut it off too soon and the COP suffers greatly. Cut it off too late and you risk serious melt down conditions unless you have a type 2 design. That is where the real engineering is going to take place. My suspicion is that it is very easy to go from a type 1 system that does not have any negative resistance region at all to worry about into a type 3 system that will latch or melt down once control is lost. This appears to be what we have witnessed so far in the MFMP melt down as well as when Parkhomov added the extra insulation. I am counting upon someone discovering a method of poisoning the reaction at a defined temperature or finding the ideal geometry to eventually come up with a type 2 ideal device. The generation of a type 2 LENR device will be among our greatest achievements. It has the negative resistance region, but that is followed by a second positive resistance region below the thermal meltdown temperature. The input power is much reduced when compared to the type 1 devices such as seen in Parkhomov's first report. The COP of one of these type 1 units is not going to be adequate to have a major impact upon the world. If instead a type 2 system can be designed then operation at very high levels of COP will be obtained. I would prefer to operate a type 2 device under stepped drive conditions. It is not necessary to use a PWM driver since we want and need it to enter the negative resistance region. So, initially apply the amount of input drive that causes the device to heat up until it reaches the negative resistance threshold. Wait while the temperature rises rapidly with that constant drive applied. Once the device stabilizes again within the second positive resistance region you can back the drive down. This reduction can continue until just prior to entering the negative resistance region from the high temperature side. Continue to apply the reduced drive power for as long as you want with a COP of 10 or more. Another advantage of a type 2 device is that once you eliminate the drive power it returns to ambient under its own power. There are not requirements to add extra coolant and no special precautions needed to enter or exit the negative resistance region. Some might say I am dreaming but I say that I am just making an engineering request that will one day come into being. So far Rossi has demonstrated a type 1 Hotcat design in public and so has Parkhomov in his first report. MFMP apparently came up with a type 3 on their first attempt. Parkhomov then began to show us type 3 behavior due to additional gain applied to a type 1 device just as expected. Jack appears to have a type 1 at this time, but he is increasing the gain as he progresses with his design. One day soon he might see type 3 action to join the melt down crowd. Bob, it is entirely too soon to declare that something is not possible unless you want to take a serious chance of having to retract it in the near future. Now is the time to keep an open mind and expect good engineering to move forward as is generally the case. Perhaps my expectations are too great and that may become true but it is much too soon for anyone to come to that conclusion. That is not intended to suggest that you should not ask probing questions about my theory since I feel that it is fairly well founded and it only helps to look at an issue from different perspectives. I highly value your thoughts and ideas. Dave -----Original Message----- From: Bob Higgins <[email protected]> To: vortex-l <[email protected]> Sent: Tue, Feb 10, 2015 7:12 pm Subject: Re: [Vo]:Explosion May Be Out of Control LENR Having a switching control of the heater bias is not at all going to fix a reactor that is unstable once it reaches a critical temperature. Such a reactor will continue to rise in temperature with NO input at all (pulse width =0). Such devices as have been shown today have essentially a fixed thermal resistance to some temperature sink near ambient. The only thermal change that will quench such an out of control reaction is to lower the thermal resistance to the low temperature sink. One good way to do this is with having convection cooling and having a fan blow a variable amount of cool air over the reactor. There is no need for water because it is difficult to control the amount of cooling you get to such a high temperature device. Air can be really linear in thermal cooling. In fact, you could use the air flow as a temperature regulator in combination with the heater control. Also, note that Rossi does use a thermocouple control for his hotCats - it is seen in his lab photographs. He monitors the core temperature and puts that into a PID controller. Such a controller can behave in ON/OFF mode to completely turn OFF the bias heat when the temperature rises above a preset limit. There can also be alarms put in that controller that would turn on a fan to lower the thermal resistance to ambient. All with his hotCat hardware today. And Rossi does use pulse width control of the AC power he is supplying. On Tue, Feb 10, 2015 at 1:40 PM, David Roberson <[email protected]> wrote: Jones, When I first began modeling the ECAT several years ago I used exactly the concept that you are suggesting. It did in fact appear to yield a COP of 6 or in that vicinity with careful adjustment of the PWM drive waveform. I used the duty cycle that Rossi had revealed within his blog entries before the recent shut down of important data. I even applied the amount of power that he spelled out. That was how it was left to await further proof until the Swiss experiment. During that experiment I saw a behavior that did not match the negative resistance region requirements from my earlier models. I could never arrive at a COP of 6 without having one of those to boost the output power. At the time I was a bit puzzled by the device and the apparent lack of that important condition. I soon realized that either Rossi intentionally gave them a low fuel charge that guaranteed stability for their test or that he had produced a new design of the type 2 category. Had the scientists carefully increased the input drive power is small steps I could have easily determined whether or not a type 2 system was now in existence. Unfortunately this was not done so I must conclude with caution that a type 1 is what was tested. In that case the thermal feedback is limited so that a negative resistance region is not present at any operating temperature. The COP will then be limited to less than 4 under ideal conditions which is lower than most of us would like to see in the long term. Perhaps Rossi realized that even a COP of 3 would prove to the world that he had some magic. The latest replications are not limited in the same way as Rossi did and the extra insulation as well as amount of fuel can be set as desired. This is just what we needed. It appears that we are now observing the negative resistance region of operation and the thermal run away that can easily tag along. I have my fingers crossed that someone will find the magic solution that leads to a type 2 system which will be highly desired since the COP can be very large and stable in that mode of operation. This is an exciting time for all of us and what we have been waiting for. It does mean that many devices are going to melt down before the process is tamed. I hope that proper precautions are taken to ensure that no one is injured by the multitude of explosions that might well be seen in the near future. How much energy can be released during the worst case melt down event is not obvious so there may be substantial risk to the brave guys working within the labs. So far Rossi is still among us so the danger may not be too much greater than already witnessed by the MFMP crew. Dave -----Original Message----- From: Jones Beene <[email protected]> To: vortex-l <[email protected]> Sent: Tue, Feb 10, 2015 1:11 pm Subject: RE: [Vo]:Explosion May Be Out of Control LENR From: David Roberson Actually the characteristic curves suggest that the input power acts like a bias that stands behind the incremental behavior. If that bias is quickly removed then there should exist a point of operation that is located ahead of the dangerous region. Unless some strong memory exists, I can imagine that the process would reverse as we all hope. Dave, Given what you say above – what about the possibility of a higher level of control simply by use of pulsed power (at very low duty)? For instance, if we know from prior experiment that 100 watts of DC will eventually lead to large gain but at the risk of thermal runaway, and we also know that quenching begins almost immediately with removal of power (unless the system has already progressed to instability) – then it would seem that low duty pulsing with the same net power will provide better control against a runaway. (that is the premise but I have not data to back it). In effect, as an alternative to 100 watts DC, it would be possible to design and construct a pulsed power supply that will provide something like 2000 watt pulses at 5% duty. The net power in is the same, but 95% of the time there is no power. The frequency can be long but the idea is to alternate short sharp pulses with long delays. Is there any reason in your model to suggest that this approach is valid? Jones
