On Tue, Nov 22, 2011 at 11:46 AM, Joshua Cude <[email protected]> wrote: > Heat flow depends on temperature differentials, so the gradient in > temperature between the surface and the core would have to be 7 > times steeper.
and also wrote: > You would need to cover 7 times the area in a matter of minutes, also not > plausible, and it would still require 7 times the heat transport rate from > the core, which doesn't depend as simply on the area of contact. As the diagram shows, heat flow into water depends extremely non-linearly on the temperature differential. It also depends more or less linearly on area of contact. We don't know what the inner geometry of the devices, and we don't know how the water level changes. So you cannot say that an increase in power transfer of x times requires an increase in core temperature of x times, because that can be achieved by a small increase in temperature, or a proportional increase in area of contact. Also, do you know what the thermal mass of the reactor is? I don't. Thus, in principle, the area of contact can be increased easily by changing the water level as demonstrated in the following example. Consider a vertical heating element, partially in contact with water fed from a pump. Let there be a thermocouple sensing the temperature T of the heating element, and a water level sensor. Control the heating element using feedback from the thermocouple to keep T constant above the boiling point of water. By matching the flow rate to the evaporation rate using the water level sensor, you keep the water level l constant. To the first approximation, the power transfer should be proportional to the area of contact which is proportional to the water level. An electric heating element can have quite a small thermal mass. The current can be ramped up very quickly. So if you start pumping more, the water level rises, and so does the evaporation rate and the power transfer. In principle, you just have to control the pumps and provide enough power to have a dQ/dt as high as you wish (within limits, of course). -- Berke Durak
