tjh290633 wrote:odysseus2000 wrote:
Higher temperatures make the transfer of heat easier. Heat pumps struggle when the reservoir is cool, as in air source heat pumps, and the room is warm, but when the reservoir is hot and the the final destination cool they work well.However, sand batteries can be used like the night storage radiators were, but instead of having to have many in a house the heat can be extracted from a single underground battery by a simple circulating water system. In this case the higher the reservoir temperature the better as you have to heat water that is already hot as needed for radiators in a warm house.
Radiation, conduction losses are all insulation dependent.
The standard equation for heat transfer q is q=Constant x (Temp of reservoir - temp of surround) x Area
This is dominated by the constant and modern insulators are good, especially if the insulation can be applied thickly which would be the case for underground storage and is not the case for example when trying to insulate house walls.
Regards,
That's odd. My Chemical Engineering colleagues used to tell me that the effect of extra insulation fall off rapidly when you get beyond 4" thick. Have the rules of nature changed?
TJH
Heat can be thought of as a fluid and insulation as an absorber. Sure you get a huge improvement with a small amount of insulation over a naked heat source, but not complete absorption, some of the heat gets out & the thicker the insulation the less heat is lost.
If you consider the earth it has a molten core that would have long ago cooled except for the heating from radioactive decay & the shell of insulation above the magma that retains most of the heat, except for the leaks such as a thermal vent & the odd volcano so that the temperature is approximately constant.
Clearly at some practical point there is no benefit to more insulation, but that point is a lot more than 4 inches. Loft insulation originally started at around 4 inches, but now 12 inch or more is standard. For space craft advanced insulators are only a few mm thick, but are equivalent to much larger amounts of conventional insulation.
It all depends on what is the needed heat retainment & for how long & from there it is possible to calculate the needed insulation to satisfy these needs.
Regards,