On Wed, Nov 30, 2011 at 3:48 AM, Robert Lynn <[email protected] > wrote:
> On 30 November 2011 06:10, Berke Durak <[email protected]> wrote: > > > > So far I haven't found anything significantly wrong with the 1 MW > > demo. Also I still don't understand your "instantaneous power > > transfer discontinuity" argument. > > It's pretty simple: you have a large quantity of water - about > 180grams per second entering the ecats, [...] The basic argument is pretty simple and the fundamental point is that the measured data are consistent with 70 kW, if you question the effectiveness or openness of the trap. However, it is possible to contrive situations where the output could be dry steam and reach as high as 470 kW without assuming any discontinuous change in the temperature of the ecat's thermal mass. One way is if the ecats start out only partly full, as has been argued. But, it occurred to me that a discontinuous change (or at least very rapid change) in the output power can also be consistent with equal input and output flow rates. The reason is that, at the boiling point , power transferred to the water stops going in to heating up the water already in the ecat, and goes entirely into the output flow. That wouldn't happen instantly, of course, because there will be temperature gradients in the water, and only part of it begins to boil at first, but it would represent an important and rapid transition in what the measured output power represents, and would not represent a change in the power transfer to the water. Before boiling, the power measured at the output (mass flow rate * c * deltaT) is not equal to the power transferred to the water if average temperature of the water is also increasing. In fact, the power transfer to the water would be: Pin = mc(Tav-dot) + m-dot c deltaT where Tav is the average temperature of the water in the ecat, and -dot represents the time derivative (so m-dot is the mass flow rate), and deltaT is the temperature difference between the input and output. The first term represents the power that goes in to heating the water already *in* the ecat, but the power coming out is represented only by the second term. In fact, in order to bring 30 L of water from 30ºC to 100ºC (assuming most of the water is at or near the bp when boiling begins) in 2 hours represents an average power of 1.25 kW per unit, or 130 kW total. (According to Lewan, the input electrical power was somewhere between 120 and 180 kW.) So, if the power transfer to the water were approximately constant, it is clear that it would have to be considerably *higher* than 70 kW, even though the power measured at the output is clearly lower than 70 kW. As soon as boiling commences, and assuming relatively homogenous water temperature, none of the power transferred to the water stays in the ecat; Tav-dot is zero and the first term disappears. All of it must come out in the form of steam. So, if the power transfer to the water were 200 kW before boiling, with 70 kW coming out in the liquid water, and 130 kW going in to heating the existing water, then after boiling, the steam would have to represent the full 200 kW. And this change would occur without any need to heat up a large thermal mass, and could happen rather quickly. An increasing power transfer during the pre-heat period would require even higher power transfer by the time boiling is reached (since of course the average would have to be the same). So, I have to concede that the sudden transition argument is much less compelling for a device that contains 30 L of water. (It is hardly weakened in the case of the smaller ecats, which contain much less water.) (Note, that this also means that the thermal mass heated in the pre-heat period is much larger than the thermal mass that needs to be heated post-boiling to increase the power transfer.) Still, the electrical input is turned off at boiling, and so, the observations remain consistent, from that point on, with power transfer between 70 kW and 470 kW. If Rossi was really producing 470 kW, the question remains why he would rely on such ambiguous measurements as the temperature at the boiling point, which do not change as the power changes 7-fold, when unambiguous measurements would be so easy to perform. Deception seems the most obvious answer.
