Back to the Parallel Plates
This scenario has come up again several times in the past few weeks, and so I think that I should write a post to address it.
I was sent this annotation of a figure from my book In the Cold Light of Day, by a Kevin Richardson on FB.
KR said:
“You should try thinking purely in terms of Energy flows and move away from the Heat flows. Radiation from the Atmosphere adds to the Surface Energy balance.
I do qualify it that Heat (aka Net Energy between objects) must always be positive down T gradient. What happens to the 1000W/m2 emitted by the plate towards the wall?
And then how do you square your circle of conservation of energy not being correct for the plate, and the wall as well with that extra 1000W/m2 impinging on it? In the absence of conservation of energy, a body is not in equilibrium.
The plate is loosing 1000W/m2 out the right, and 1000W/m2 out the left. While only receiving 1000W/m2. You are not obeying conservation of energy on the plate.
You make the error that Radiative heat transfer somehow is not based on bidirectional emission Energy (which it is).
You fail to realize that your flaw in thinking starts with a narrow view of heat transfer as a 1-way street for everything”
First, note the request to not analyze the situation in terms of heat flow, and to discard that and move away from the definitions of heat flow, and to only think about “energy balance” instead.
This is a sophistical attempt to skirt around and redefine the First Law of Thermodynamics, i.e., the Law of Conservation of Energy.
The First Law does not say that we should add up energy balances. That’s not what it says at all. It says that to change temperature, an object must have heat or work performed upon it: dU = Q + W = mCpdT.
And it is in that process, in which energy is conserved.
So then, if you want to know what heat is, that is a separate equation, and for plane parallel radiative it looks like this: Q = sigma(Thot4 – Tcool4). There are lots of summaries of the definition of heat, and they reduce to the concept that heat flows from hot to cool.
This new concept which has been invented by flat Earth climate alarm pseudoscience, that, again:
“You should try thinking purely in terms of Energy flows and move away from the Heat flows”
and
“Heat (aka Net Energy between objects) must always be positive down T gradient”
is an attempt to have backradiation increase temperature but without calling it heat, and thereby, it is actually an attempt to conserve heat flow, rather than conserve energy.
But, heat is not what is conserved, and, heat must go to zero in thermal equilibrium given the definition of the 1st Law (dU = Q = dT = 0 in thermal equilibrium), and so that new statement is not consistent with the First Law, which is why there is an attempt to redefine the First Law along with the definition of heat.
Of course heat transfer is about bi-directional energy flows. That is the very equation which is shown: Q = sigma*(Thot4 – Tcool4). Heat is the difference between the Stefan-Boltzmann emission terms.
Heat is one way: Q = sigma*(Thot4 – Tcool4). From hot to cool; heat is the difference of emission between a warm body and cool body, with the heat acting by the warm body upon the cool body to raise its temperature.
Every thermodynamic textbook ever made, outside of climate flat Earth theory, identifies this property of heat.
It is a violation of the First Law to claim that the radiation from the cooler object will raise the temperature of the warmer object. dU = Q = mCpdT. Heat is what is required to raise temperature, and the radiation energy from the cool object contains no heat.
The energy from the cool object does not increase the temperature of the warm object, due to the First Law of Thermodynamics, which is the Law of Conservation of Energy.
Nothing happens to the 1000W/m2 emitted by the plate towards the wall. The net transfer of energy is zero, as per the definition of thermal equilibrium where dT = 0, which means that Q = 0.
What we do know, from the First Law of Thermodynamics or Law of Conservation of Energy, which tells us how temperature can increase, is that the radiation intensity from the passive plate cannot increase the temperature of the source wall, because to increase temperature, we require heat.
This is where the new language of “energy balance” has created such confusion by attempting to get around the First Law and definition of heat, so that flat Earth theory could be supported by climate alarmism pseudoscience.
The figure as originally depicted without the annotations defines thermal equilibrium, which via the First Law is dU = Q = mCpdT = 0, between two bodies. Thermal equilibrium requires Q (and therefore dT) to be zero, between the view factors of two body’s interaction with each other.
In the suggested annotation, Q > 0 between the two bodies’ view of each other, and therefore dT > 0, which violates the premise that there is thermal equilibrium between them.
The 1000 W/m2 emitted by the plate back toward the source is not lost by the plate, because the source gives it right back. To add it back in to the source wall, for “energy balance”, instead of via the First Law and heat definitions, implies that the radiant energy of ice-cubes should be able to add to each other to increase temperature.
Temperature simply does not behave that way. Temperatures simply do not add together. One can add more and more ice-cubes together in a space, but their compounding mass simply will not increase in temperature, and their compounded radiant intensity will likewise NOT add all up and create a more intense field than each original ice cube.
The suggested annotation has Q > 0, because 2000 W/m2 are impinging upon the surface of the passive plate from the source wall, but only 1000 W/m2 is the energy density produced by the plate itself.
And so, at the surface of the plate, it experiences Q = 1000 W/m2 from the source, which means it must increase in temperature, because Q is defined between the view factors of two bodies. The correct solution for thermal equilibrium is as originally depicted.
Q = 0 between the plate and source wall themselves, and the required energy is emitted by the plate to space. This is conservation of energy in thermal equilibrium, as it is defined by the 1st Law.
The plate is not losing 1000 W/m2 on the left toward the source plate, but is losing 0, because 1000 W/m2 is coming from the source plate to replace whatever might be lost.
The only direction the plate loses energy is 1000 W/m2 on the right, away from the source wall, out to space. The suggested annotation has a positive heat flow from the wall into the plate, which therefore, via the Law of Conservation of Energy, which is the First Law of Thermodynamics, the plate would have to increase in temperature, which violates the premise that this is an equilibrium with dT = Q = 0.
The very definition of the Law of Conservation of Energy, which is dU = Q = mCpdT, requires that the energy density from the source wall must equal the energy density at the surface of the plate, and therefore they must both be 1000 W/m2, so that Q = 0, so that dT = 0.
Obeying conservation of energy means obeying the First Law, and the Law of Conservation of Energy which is the First Law of Thermodynamics is defined as dU = Q + W = mCpdT, or with no work then dU = Q = mCpdT.
To obey the law of conservation of energy, when there is thermal equilibrium, therefore means that dT = 0 (no temperature change), which requires Q = 0 (no heat flow), which means no temperature differential between the panes in plane-parallel geometry.
The Law of Conservation of Energy is not about this idea of “energy balance” which has been created for flat Earth climate alarm pseudoscience. The Law of Conservation of Energy is the First Law of Thermodynamics, which is defined as dU = Q + W = mCpdT, or with no work then dU = Q = mCpdT.
This is how you obey the law of conservation of energy. When there is thermal equilibrium, then dT = Q = dU = 0 between each pair of bodies, and Q can only equal zero when the energy densities are equal in plane-parallel geometry, which means that the panes must have the same temperature.
Thermal equilibrium is not defined by “the sum of heat flows equaling zero”. That is not at all what the First Law says. The First Law, the Law of Conservation of Energy, is about the exchange of energy between two bodies in the form of heat and work, dU = Q + W = mCpdT, and thermal equilibrium between two bodies is when dU = Q = dT = 0 for both bodies.
Q is defined between two bodies only: Q = sigma*(Thot4 – Tcool4), in plane-parallel. What you want to know, for thermal equilibrium, is when one body will stop changing the temperature of another body, and that happens only when heat between them is zero.
There is simply no way in which flat Earth theory can justify these reinterpretations of the laws of thermodynamics.
Every example brought forth only reinforces the fact that flat Earth theory has attempted to redefine thermodynamic laws and principles for the sake of climate alarmist pseudoscience.
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Herb Rose
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Joe’s wrong.
When an object radiates heat/energy it decreases with distance. Two objects with different temperatures (T1 > T2) will radiated heat/energy in all directions and that energy will decrease as the square of the distance. When the two temperatures become equal, the flow of energy ceases. Say T1 = 2T2. At a distance, d, between the two objects T1 will equal T2 and no heat/energy will flow to object 2, even though its temperature is lower than object 1’s temperature. It is only when T1/d^2 is greater than T2 that energy can be added to T2 and that added energy will then increase the heat/energy being radiated by object 2 shifting the equilibrium point towards object 1 and stopping the flow of heat energy to object 2 before T2 = T1. Radiated energy cannot cause the temperature of the two objects to equalize.
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Zippy
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I’m more inclined to believe Joe Postma, having been proved right on numerous occasions, and been engaged by numerous scientific bodies, than a…well, nobody.
Show us your credentials, and, more importantly, that you have been heavily cancelled and shadow banned, then I may give you credence,
(Rescued from the Spam Folder) SUNMOD
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Penguinite
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From my non-scientific lived experience! When I take a frozen object out of my freezer and place it on a metal surface the frozen object gets warm (thaws) and the metal surface cools. Heat transference?!
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Herb Rose
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Hi Penguinite,
That energy/heat transfer (like most we experience) is due to conduction/convection, not radiation. The molecules in the metal tray (and the air) are colliding with the molecules of the frozen object, transferring energy according to the conservation of momentum (M1V1 + M2V2 > M1V3 + M2V4). In this type of energy transfer the energy flow from the object with greater energy(V^2)/unit mass to the object with less energy(V^2)/unit mass instantaneously. With radiated energy transfer the rate of energy flow depends on the difference in temperature and slows as the temperatures approach equilibrium.
Herb
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Jerry Krause
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Hi Herb.
“That energy/heat transfer (like most we experience) is due to conduction/convection, not radiation.” Have you forgotten about the Sun?
Have a good day
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Flann
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Testing to see if I am allowed to post
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Gary Ashe
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Thanks for the successful test.
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Gordon
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KR’s statement, “Radiation from the Atmosphere adds to the Surface Energy balance,” seems to echo the postulation of John Tyndall’s 19th century “greenhouse effect” hypothesis that “back radiation” from the ceiling of a greenhouse is what causes the air inside of the greenhouse to be warmer than the air outside of the greenhouse.
All that is actually happening is that the greenhouse structure itself prevents the air inside of it from expanding and ascending skyward to be replaced with cooler air from above, which is what is happening outside of the greenhouse.
As that warmed, outside, surface-level air ascends and expands against the cooler, lower-pressured air above, it does “work” on that cooler air and itself drops in temperature. Conversely, as the cooler air from above descends to replace the ascending higher-pressured air, it has “work” done on it, which raises its temperature.
When 15C surface-level air has ascended 5km in altitude its temperature will have dropped to -18C. When it reaches the Tropopause its temperature will have dropped to -51C. Conversely, when Tropopause air at -51C drops to 5km in altitude its temperature will have increased to -18C. When it reaches the surface it will have increased to 15C in temperature.
The average temperature of Tropospheric air is thus -18C. Where is the “greenhouse effect”?
Where is all of the extra thermal energy that “greenhouse gases” are supposedly “trapping” in the atmosphere?
In claiming the existence of a “greenhouse effect”, rather than averaging the temperature of the entire Troposphere top to bottom, they only average the temperature of the hottest part of the Troposphere–surface level air–and “Voila!” a 33C “greenhouse effect” magically appears!
That the average temperature of surface level air is 33C higher than the average temperature of the entire Troposphere should be called the “heat pump effect” and those who want to understand why there is a temperature differential between surface level air and the air at the Tropopause, should study the science behind the air conditioner/heat pump, i.e., thermal energy transfer via “work”, rather than thermal energy transfer via IR radiation.
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Herb Rose
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Hi Gordon,
You have no idea what is happening in the atmosphere. The atmosphere exist because energy has converted N2, O2, and Argon into gases and by adding energy to these gas molecules the volume of the atmosphere expands. When a gas molecule loses energy and contracts (fall) the loss of energy does not cause the molecule to gain energy. It is the molecules at the top of the atmosphere that have the greatest KE (least density) and the flow of energy is downwards to the surface not up.
Look at the graph of temperature of the atmosphere. Energy does not flow in a zig zag line or pause when it changes direction. The thermometer is not measuring the KE of the gas molecules but the momentum of those molecules. As the density of the air decreases with increasing altitude the number of collisions transferring energy to the thermometer decreases so there are two variables creating the graph. In order to get an indication of the KE of the molecules you must divide the temperature reading by the density to gat the KE of a constant number of molecules instead of a constant volume of molecules. This graph shows the KE of molecules increasing in a straight line in the troposphere (where water moderates the temperature) and in an exponential curve above the troposphere. It is the sun’s radiation (UV) that are heating the atmosphere, not the Earth. Were you taught that all matter absorbs radiated energy (LOT) except the N2, O2, and Argon in the atmosphere.
The air at the bottom of the Grand Canyon is consistently 10 F warmer than the air at the top of the canyon. If those air molecules had more KE they would expand and rise to the top, but they don’t. The reason the thermometer says the air is hotter is because the air is denser and even though those molecules have less KE their more frequent collisions transfer more energy to the thermometer.
Adiabatic heating in the atmosphere is nonsense. The “work” is done by KE counteracting gravity.
Herb
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Gordon
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Hi Herb,
What contradicts your hypothesis is the phenomenon called “free expansion”:
“Free expansion” is the expansion of a gas into a vacuum. When a gas expands into a vacuum, its volume increases and its pressure drops but its temperature remains the same because no heat is exchanged and no work is done.
Or are you suggesting that the Ideal Gas Law is errant?
PV=nRT
P = pressure
V = volume
n = amount of substance
R = ideal gas constant
T = temperature
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Herb Rose
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Hi Gordon,
The Ideal Gas law is not an equation but a statement that the macro properties (pressure volume) of a confined gas are due to the properties (number of molecules, A constant for those molecules, and the kinetic energy of the molecules) of the molecules that form it.A change in a macro property will not change the properties of the gas molecules but the other macro property. A change in the components will change the macro properties.
When the volume of a gas changes the pressure changes because the number of collisions change and there is a corresponding change in the temperature of the gas as a whole even though the kinetic energy of the molecules has not changed.
When scuba tanks are filled from a larger high pressure tank the increase in number of molecules striking the sides of the scuba tank increases the energy being transferred causing the tank to heat up. At the same time the amount of energy striking the sides of the reservoir tank decreases causing the pressure to drop and the temperature of the tank to decline.
Herb
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