1

Flat 1x1 meter plate. Heat source indicated by red arrow. The rest is in space. No sun exposure at all.

Parallel plates

Some of the photons will exit through the gaps between plates. No problem. My question is about the photons that do make it from plate to plate.

One photon leaves the first plate and is received by the second. Is this transfer of heat 100% efficient? If not, why? If the energy does not go into heat, where does it go?

A variant of this question would be a hypothetical sphere heat source inside a much larger hollow sphere in space. Is heat transfer through radiation from the small sphere in the center to the larger outer sphere 100% efficient?

Let's define the term: "100% efficient" is taken to mean that one unit of energy carried away by a photon from the source delivers one unit of energy to the destination.

martin's
  • 549
  • 4
  • 5
  • It depends on what the plate is made of and its thickness. It can block or reflect infrared photons or just pass through depending on the material. – Star Man May 21 '20 at 16:31
  • What material would allow 100% of IR to pass through? – martin's May 21 '20 at 19:48
  • Nothing will allow 100% of IR to pass through but different materials will block more and other will block less. – Star Man May 21 '20 at 22:10
  • If there is a continuous source of heat X then temperatures will rise until equilibrium is established and thermal radiation to space equals X. Each layer has a temperature and produces its own thermal radiation in addition to transmitting and reflecting thermal radiation from the source and from other layers. This has to be set up as a mildly complicated set of equations and solved carefully to find the equilibrium or steady-state inter-layer fluxes and temperatures. – uhoh May 21 '20 at 22:37
  • Heat is energy. Photons, phonons, whatever. Your question doesn't reallly make sense, because photon absorption is a statistical process. If a photon is absorbed, all its energy goes into electron level jumps and/or momentum transfers to atoms. If a photon is reflected, there's the standard momentum transfer based on the relative mass (or energy) of the photon and the object – Carl Witthoft May 22 '20 at 13:27
  • I'm of the mind that energy must be conserved according to First Law so if some portion of the input energy doesn't make it to the other side, there must have been a physical change of state in the material that required some energy input. I can't think of how else energy might not be conserved. – aranedain May 22 '20 at 15:17
  • If you don't get answers here, you migth try on physics.SE – Manu H May 22 '20 at 16:21
  • 2
    I’m voting to close this question because it belongs in the physics SE. While it is vague, it could be edited to be more focused. Regardless, it doesn't belong here. – Anton Hengst May 22 '20 at 22:11
  • I’m voting to close this question because it is not about Space Exploration. It's a physics problem and might be suitable for Physics SE if clarified. – uhoh May 22 '20 at 23:31

0 Answers0