Jack Cole <[email protected]> wrote:
> I think my standard might be a bit lower than 2 for a COP. I'd be > convinced with 1.5 (say 135W out vs. 90 in). Kind of hard for the > measurements to be that far off, because in the current setup, that would > be something like a 150C temp difference. > That sounds reasonable. Let me just clarify that you are using the term COP in the conventional sense that an HVAC installer would: output power divided by input power. Strictly speaking, this should be energy out/in, but they actually refer to BTU/hour divided by kilowatts. The former they compute with a anemometer and thermometer with forced air systems. This works because HVAC systems produce a stable ratio. See, for example: http://www.engineeringtoolbox.com/heat-pump-efficiency-ratings-d_1117.html (See example below.) Because cold fusion output tends to be erratic people often use COP to mean total energy out/energy in. As Beene pointed out, the instantaneous power COP is not meaningful when output fluctuates. Today, here for the first time that I know of, Beene used "COP" to mean energy out/potential chemical energy. That is not what you meant when you reported a 1.1 COP. Note that with air conditioners and heat pumps the COP is higher than one, because heat is moved, not generated. This causes endless confusion. Many people think this is a violation of thermodynamics, and some try to use it to make perpetual motion machines. The Engineering Tool Box web site I linked to above is excellent, but note that they freely mix up units of power and energy. Quote: COP can be expressed as *COP = hh / hw (1)* *where* *COP = Coefficient of Performance* *hh = heat produced (Btu/h)* *hw = equivalent electric energy input (Btu/h) = 3413 Pw* *where* *Pw = electrical input energy (W)* If a heat pump delivers *3 units* of heat for every unit of energy input - the COP is *3*. - *1 kW = 1000 W = 3413 Btu/h* That should say "*Pw = electrical input POWER (W)"* Beene accused me of mixing up power and energy. I did not, in fact, mix them up, but HVAC people and engineers often do, as they did in this case. Of course they actually know better. They use an instantaneous reading of power to compute the COP because there would be no point to sitting there for an hour measuring energy. You would get the same answer. Because the COP is stable at a given temperature difference between the indoors and outdoors. - Jed
