Stefan-Boltzmann’s law has to do with black body radiation, Wein’s law and other concepts related to thermal radiation (infrared) and other types of electromagnetic radiation, among other very abstract concepts. All this is very well documented and can be consulted on the Internet.
This article is about a very simple and totally new app used to keep your enchiladas (I mean your food) warm:
A microwave-safe ceramic HEAT RETENTIVE PLATE or a heat retention plate, what do you prefer?
What happens if you enclose a disk of highly efficient microwave absorbent material in a microwave-transparent airtight cavity like ceramic and preheat it in a 1200 Watt microwave oven for say … one minute ?:
That hypothetical disk will get very hot and radiate in the infrared wavelength (if it gets too hot (like red hot) it will even radiate in the visible part of the electromagnetic spectrum. Fortunately we can regulate the warm-up time.
Now let’s say that this disk that I will call a heater is in minimal physical contact with the walls of the cavity (separated by pointed protrusions), if the cavity is heat sealed it will form a semi-vacuum, so the heat losses will be mainly due to radiation since the semi-vacuum will also minimize heat losses by convection.
Now, since the cavity is very tight, some of the radiation from the heater will be reflected and the interior of the cavity (or space in the cavity) will reach a temperature very close to the temperature of the “hot body” (the heater).
According to the Stefan-Boltzmann formula, the net radiated power is equal to the emissivity multiplied by the Stefan constant, multiplied by the area, multiplied by – here comes the good part – the temperature difference of the heater minus the surrounding temperature, both to the fourth power (in degrees Kelvin).
Bottom line:
The difference in temperatures has a great weight (or weight) in the formula, since they are in the fourth power. Radiation from the heater will be limited. If this heat storage device is incorporated into the design of a ceramic plate, your food will stay warm.
The emissivity of the heater and the absorption coefficient of the cavity walls can also be manipulated for better control.
How to prevent the board from breaking due to thermal shock is another story. I have solved the problem. For more information, search for HEAT RETENTIVE PLATES on the internet.
By the way, I made them up.
Juan J. Ramirez
El Paso, Texas
