Re: [Vo]:If 2 heat engines are placed in series their efficiency is lower, and the second law breaks according to Carnot if that can occur!
Oh I missed the end: "Heatpumps are reverse Carnot engines and have a much higher COP in respect to heat gained but *not to current gained!!!"* Current? I'm not sure what you mean by this, you might be talking about the volume of thermal energy moved, or you might be talking about the electrical current, neither makes sense to me so I'll pass. But I will agree that heatpumps as reverse Carnot engines have a much higher COP as in they produce a large "current" of thermal energy at a low "potential" very efficiently, as the thermal hill grows the efficiency as a heat pump drops. Requiring more electrical current input. Nope, no idea what you are talking about. "Even more interesting are quantum level processes in nano particles where one could achieve the doubling of IR photon energy by suppressing some emission bands. This could be used in solar panels." Well there is also a picowatt LED that makes the air colder and emits more light energy than electrical energy put into it. On Fri, 10 May 2024 at 13:49, Jonathan Berry wrote: > Not sure why but this isn't forming into proper paragraphs... > > > *"Youtube physics usually is self satisfaction of people that have no clue > of the simplest things. So I almost never watch this garbage."* > The video is covering the work of a company cascading heat pumps. > As such the temperature differential over each heat pump is a fraction of > the total over all the heatpumps, there is a potential feedback instability > effect they have resolved. > > But cascaded heatpumps are an accepted thing with improved COP over a > given total temperature difference and the video isn't making claims about > the second law, that's me, and well Carnot... > > *"A heatpump is not a Carnot process as you obviously supply additional > energy!"* > > It is a carnot process though and the carnot process gives us the > efficiency limit. > > A reversible heat engine if you supply it with kinetic energy can generate > a temperature differential, this is why it is called reversible, you don't > get energy from it, you reverse it and put energy in to move heat. > > To do this you obviously need to supply it with energy just as we do with > a heat pump. > > *"You must calculate in the Carnot conversion rate of energy gained --> > electricity to get the proper conversion factor as the current for the > heatpump must be produced too and subtracted!"* > > Yes, however the COP of a heat pump (electrical power in .vs heat energy > gain on the hot side) over a low temperature differential can be 5, 10, or > 30 or potentially more if the temperature differential is low enough. > > Note that in a single stage heatpump we can actually double that COP by > just counting both the hot and cold outputs as both being beneficial > outputs! > > If a heatpump can deliver four times more thermal energy than the power > going in (and for now assuming the heat from the input power is not seeping > inside) then wit has a COP of 4, but we ignore the cooling COP of 4 on the > other side, that is "free cold" and in terms of a temperature differential > to put a heat engine on both are sources of energy, but between the hot and > cold sides is a higher conversion efficiency than between the hot and > ambient and the cold and ambient. > > Which is the point I am making, if you divide the heat potential the COP > of the heat moving ability of a heat engine or heat pump it improves > relative to the energy it takes to drive it. > > > *"The best Carnot process (multi stage turbines) today delivers a > conversion rate of about 61% always target is current."* > > 61% is a fine conversion of heat to to energy since heatpumps can manage a > COP of 30! > > https://www.sciencedirect.com/topics/engineering/recompression COP > 30 "typically COP of 10–30 can be achieved" with a MVR heatpump. > > https://www.gea.com/en/assets/304829/ COP 20 > > You can have 30 times more heat energy moved and that's just looking at > the heat energy gain, ignoring the energy below ambient on the cold side, > so with that a COP of 60!... > > Now granted my whole point is not that this if done with a single heatpump > it would not be efficient when you run steam turbines over 1C, 10C or so, > so it does not matter how well it was design, because to gain efficiency > for conversion of thermal energy we need as great a temperature difference > as possible, but there is no reason we can't put multiple heat pumps in > series each working over a small temperature range just as we put batteries > in series. > > And we can do the same with heat engines which are just Carnot heat > engines under a different name not designed to be reversible but > conceivably can be redesigned to be reversible. > > > And again, the point of this post is to point it out from the other > direction, according to Carnot if a reversible heat engine can be made more > or less efficient (while still not having frictional losses, poor thermal > insulation etc) then the
Re: [Vo]:If 2 heat engines are placed in series their efficiency is lower, and the second law breaks according to Carnot if that can occur!
Not sure why but this isn't forming into proper paragraphs... *"Youtube physics usually is self satisfaction of people that have no clue of the simplest things. So I almost never watch this garbage."* The video is covering the work of a company cascading heat pumps. As such the temperature differential over each heat pump is a fraction of the total over all the heatpumps, there is a potential feedback instability effect they have resolved. But cascaded heatpumps are an accepted thing with improved COP over a given total temperature difference and the video isn't making claims about the second law, that's me, and well Carnot... *"A heatpump is not a Carnot process as you obviously supply additional energy!"* It is a carnot process though and the carnot process gives us the efficiency limit. A reversible heat engine if you supply it with kinetic energy can generate a temperature differential, this is why it is called reversible, you don't get energy from it, you reverse it and put energy in to move heat. To do this you obviously need to supply it with energy just as we do with a heat pump. *"You must calculate in the Carnot conversion rate of energy gained --> electricity to get the proper conversion factor as the current for the heatpump must be produced too and subtracted!"* Yes, however the COP of a heat pump (electrical power in .vs heat energy gain on the hot side) over a low temperature differential can be 5, 10, or 30 or potentially more if the temperature differential is low enough. Note that in a single stage heatpump we can actually double that COP by just counting both the hot and cold outputs as both being beneficial outputs! If a heatpump can deliver four times more thermal energy than the power going in (and for now assuming the heat from the input power is not seeping inside) then wit has a COP of 4, but we ignore the cooling COP of 4 on the other side, that is "free cold" and in terms of a temperature differential to put a heat engine on both are sources of energy, but between the hot and cold sides is a higher conversion efficiency than between the hot and ambient and the cold and ambient. Which is the point I am making, if you divide the heat potential the COP of the heat moving ability of a heat engine or heat pump it improves relative to the energy it takes to drive it. *"The best Carnot process (multi stage turbines) today delivers a conversion rate of about 61% always target is current."* 61% is a fine conversion of heat to to energy since heatpumps can manage a COP of 30! https://www.sciencedirect.com/topics/engineering/recompression COP 30 "typically COP of 10–30 can be achieved" with a MVR heatpump. https://www.gea.com/en/assets/304829/ COP 20 You can have 30 times more heat energy moved and that's just looking at the heat energy gain, ignoring the energy below ambient on the cold side, so with that a COP of 60!... Now granted my whole point is not that this if done with a single heatpump it would not be efficient when you run steam turbines over 1C, 10C or so, so it does not matter how well it was design, because to gain efficiency for conversion of thermal energy we need as great a temperature difference as possible, but there is no reason we can't put multiple heat pumps in series each working over a small temperature range just as we put batteries in series. And we can do the same with heat engines which are just Carnot heat engines under a different name not designed to be reversible but conceivably can be redesigned to be reversible. And again, the point of this post is to point it out from the other direction, according to Carnot if a reversible heat engine can be made more or less efficient (while still not having frictional losses, poor thermal insulation etc) then the second law would fail. And as putting two in series makes it less efficient (as Carnot would himself assert if he had thought if it and apparently he managed not to)... well then the second law fails, it CANNOT be true if this is a reversible heat engine, AKA, a heat pump, as a less efficient heat engine is a more efficient heat pump! That is the message of Carnot's theorem, but another thing of Carnot's is the equation that tells us the efficiency of a heat engine. η = 1 - Tc / Th We take the cold temp in Kelvin, divide it by the hot temp and then subtract the result from 1 then multiply by 100 to get our efficiency in percent. So at -200C on the cold side and -190C on the "hot' side we have, after adding 273.15 K 73.15 K which we divide by 83.15 = 0.8797354179194227 subtracted from 1 gives us a 0.12 which we multiply be 100 to get the percent: 12% efficiency. Interestingly if we drop the cold side to 0.0001 K and the hot side to 10 K we get 0.1 which subtracted from 1 x 100 gives us an efficiency of 99.9%! At just 10C (K) difference! Just why the cold side being almost perfectly cold skyrockets the theoretical conversion efficiency... I am not clear on. And
Re: [Vo]:If 2 heat engines are placed in series their efficiency is lower, and the second law breaks according to Carnot if that can occur!
Youtube physics usually is self satisfaction of people that have no clue of the simplest things. So I almost never watch this garbage. A heatpump is not a Carnot process as *you obviously supply additional energy*! You must calculate in the Carnot conversion rate of energy gained --> electricity to get the proper conversion factor as the current for the heatpump must be produced too*and subtracted! * The best Carnot process (multi stage turbines) today delivers a conversion rate of about 61% always target is current. But there have been some materials detected that can improve this further like thermo (Peltier-) elements. Heatpumps are reverse Carnot engines and have a much higher COP in respect to heat gained but *not to current gained!!!* Even more interesting are quantum level processes in nano particles where one could achieve the doubling of IR photon energy by suppressing some emission bands. This could be used in solar panels. J.W. On 09.05.2024 14:39, Jonathan Berry wrote: After 200 years (1824) the second law of thermodynamics is disproven. https://en.wikipedia.org/wiki/Carnot%27s_theorem_(thermodynamics) Simply Carnot argues that if the efficiency of a reversible heat engine was variable based on how it is made or the gases etc, then the second law of conservation would be broken. "A heat engine *cannot* drive a less-efficient reversible heat engine without _violating the second law of thermodynamics_." (excerpt from the Wikipedia article below the image) So what happens when you take 2 reversible heat engines and put them in series (one touches the hot side, one the cold side and they join in the middle with potentially a small thermal mass that is thermally equidistant to the hot and cold side)??? Well, we know what happens, according to Carnot! The lower the thermal potential the lower the efficiency at turning heat into mechanical energy and therefore the less mechanical energy is developed when driving heat (operating the heat engine as a heat pump)... Which is to say that with a lower temperature differential a heatpump operates with more efficiency. So a heat engine constructed to act like 2 or more reversible heat engines will break the conservation of energy. There is a company that is making cascading heatpumps which can keep a high COP over a much larger temperature differential. https://www.youtube.com/watch?v=wSgv5NwtByk The point is that it is absolutely possible to turn uniform ambient heat into electrical power and heating and or cooling with current technology... And it is easily explained in a way that cannot be denied, clearly 2 heatpumps cascading have a higher COP, same as saying clearly 2 reversible heat engines in series have a lower conversion efficiency and therefor a higher COP as a hatpump, precisely the scenario that made Carnot assert 200 years ago would destroy the second law of thermodynamics. Jonathan -- Jürg Wyttenbach Bifangstr. 22 8910 Affoltern am Albis +41 44 760 14 18 +41 79 246 36 06
[Vo]:If 2 heat engines are placed in series their efficiency is lower, and the second law breaks according to Carnot if that can occur!
After 200 years (1824) the second law of thermodynamics is disproven. https://en.wikipedia.org/wiki/Carnot%27s_theorem_(thermodynamics) Simply Carnot argues that if the efficiency of a reversible heat engine was variable based on how it is made or the gases etc, then the second law of conservation would be broken. "A heat engine *cannot* drive a less-efficient reversible heat engine without *violating the second law of thermodynamics*." (excerpt from the Wikipedia article below the image) So what happens when you take 2 reversible heat engines and put them in series (one touches the hot side, one the cold side and they join in the middle with potentially a small thermal mass that is thermally equidistant to the hot and cold side)??? Well, we know what happens, according to Carnot! The lower the thermal potential the lower the efficiency at turning heat into mechanical energy and therefore the less mechanical energy is developed when driving heat (operating the heat engine as a heat pump)... Which is to say that with a lower temperature differential a heatpump operates with more efficiency. So a heat engine constructed to act like 2 or more reversible heat engines will break the conservation of energy. There is a company that is making cascading heatpumps which can keep a high COP over a much larger temperature differential. https://www.youtube.com/watch?v=wSgv5NwtByk The point is that it is absolutely possible to turn uniform ambient heat into electrical power and heating and or cooling with current technology... And it is easily explained in a way that cannot be denied, clearly 2 heatpumps cascading have a higher COP, same as saying clearly 2 reversible heat engines in series have a lower conversion efficiency and therefor a higher COP as a hatpump, precisely the scenario that made Carnot assert 200 years ago would destroy the second law of thermodynamics. Jonathan
