Radiative Heat Transfer: History

Radiative heat transfer is described in two different ways, as:

1. One-way net transfer from hot to cold.
2. Two-way transfer between hot and cold with net transfer from hot to cold.

I argue that 1. is physical obeying the 2nd law of thermodynamics, while 2. is unphysical violating the 2nd law.

The origin of 1. and 2. is traced in The Laws of Radiation and Absorption and Pictet's Experiment back to

1. Pictet:

• two-way wave theory
• one-way transfer of heat energy from hot to cold.

2. Rumford (Benjamin Thompson):

• wave theory
• radiant heat as an analog to sound
• higher frequencies excite lower frequencies: heating.

3. Prevost:

• particle theory, corpuscular fluid caloric
• matter of heat or fire
• quanta of energy
• two-way transfer with hot winning over cold.

The difference between 1. + 2. and 3 is expressed clearly in different views on the case with two bodies of equal temperature:

• Pictet/Rumford: no exchange of heat energy because of a "balance of power" as standing wave.
• Prevost: exchange of equal quanta of energy.

The difference can also be seen in the experiment by Pictet illustrated above, with an object and a thermometer placed in the foci of two concave mirrors:

Pictet observed that if the body was chilled by ice, then the thermometer initially at room temperature showed cooling, as if coldness or cold was transferred from the ice to the thermometer. If the body or thermometer was out of focus nothing happened, apparently because the radiative contact disappeared.

The experiment was initially met with surprise suggesting an exchange of something like "quanta of cold" transferred by "frigorific rays" as an analog to exchange of quanta of heat

by a stream of photons.

Pictet gave the natural explanation based on 1. that what happens is that the warm thermometer heats the ice and thus looses heat showing cooling.

Prevost gave a different explanation based on 2. as an imbalance of exchange of "fire particles"

with the effect that the warmer thermometer loses more particles than it receives and thus cools off.

Notice that 3. is similar to the phlogiston theory about a fire-like element released during combustion. Phlogiston theory is no longer part of science, but surprisingly 2. has survived with support of the idea of radiative heat transfer as streams of energy quanta or photons coming from quantum mechanics.

3. thus represents a strange mix of old phlogiston theory and modern physics, and this mix is used by CO2 alarmists to sell the idea of DLR/backradiation.

It is now time to once and for all finish the debate between 1. + 2. and 3. and put 3. into the wardrobe together with phlogiston theory.

3. violates the 2nd law by allowing transfer of heat from cold to warm and 2. serves no other role than supporting CO2 alarmism.