In reply to David Roberson's message of Fri, 25 Sep 2015 21:05:01 -0400: Hi David, [snip] >Robin, > >I think we are on the same frequency in this quest. It appears that any non >linear process that can be coaxed into converting the kinetic energy due to >thermal motion into potential energy of some type will achieve the goal.
Indeed. > >The second law must be based upon linear behavior of gasses, etc. and may fail >to cover non linear processes on occasion leading to violations. Carnot is very simple. It says that the work done is at most the difference in kinetic energy of the molecules before and after. Energy before:- Eb = k * Thigh Energy after:- Ea = k * Tlow (Eb-Ea)/Eb = (k * Thigh - k * Tlow)/(k * Thigh) the factor "k" cancels out leaving as with the Carnot expression:- (Thigh-Tlow)/Thigh. However this assumes that the only energy available is the initial kinetic energy of the molecules. IOW it assumes a closed system. If the system is open, e.g. if external thermal energy can flow into the system while it is doing work, then more work can be done than would be calculated according to Carnot. However the true nature of thermal equilibrium is that heat flows in both directions. In order to create a temperature differential, you need to introduce a bias in the flow of energy. Diodes do this for electric current. Another fairly common example is differing radiation or transparencies at different wavelengths. An example of the former is a piece of shiny metal left lying in the sun, which can become so hot you can fry an egg on it. I.e. a very clear temperature differential between the metal and the surrounding air. An example based on differing transparencies, is the greenhouse, where short wavelength light penetrates the glass easily but longer wavelength infra-red finds it more difficult to leave, leading to a temperature differential between inside and outside. (I remember one hot summers day, as a child, we had a living room with floor to ceiling curtains along the full length of a West facing wall. We went out and left the curtains open and the doors shut. When we got home in the evening the candles had "wilted" in their candle sticks.) Both of these are sorts of "optical diode". In short, spontaneous temperature differentials are actually fairly common, we just sometimes fail to recognize them for what they are. Solar cells also do this in essence. They convert incoming light to potential energy over the diode junction, which we then utilize elsewhere. Plants do it with photosynthesis. Both convert photonic energy into potential energy, electrical in the case of solar cells, chemical in the case of plants. In each of these cases the thermal equilibrium is destroyed, because energy is converted into a form from which it either doesn't, or only partially, returns. I.e. a bias in the flow is created. [snip] Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
