drthip4peace t1_j5qmi6i wrote on January 24, 2023 at 9:51 PM

Reply to comment by jermdizzle in Why does hot air cool? by AspGuy25

why not? Is this metal the outer layer of the system. One side at 105 the other at some other temp, such as room temp. Conduction of the material is important especially if the question is why is one thing one temp and this other thing another temp. How thick is this metal? Why would it not act as a "heat sink?" I think it applies, it is thermodynamics but the last time I thought I was wrong I was mistaken.

jermdizzle t1_j5rhyl2 wrote on January 25, 2023 at 1:23 AM

The metal housing wasn't the oven's housing, it was the housing of the part being heated, or at least that's what the OP typed grammatically. They may have meant something different. Either way the temperature delta wouldn't have anything to do with the heated air, it would just be thermal conduction if it was the interior of the oven wall that was cooler than the internal ambient air. Also, you can test this on your own very easily. Go try to use a thermal camera or IR thermometer on a shiny piece of metal. You'll receive obviously inaccurate readings. Place a piece of dark tape or paint on said metal and watch as the temperature is more accurately represented.

Edit: I'd also like to point out that this is inside of an oven. There is more heat being introduced to the system on a consistent basis to maintain a constant-ish temperature. If there was a hunk of metal inside that was still below the target temperature, it'll keep introducing heat. Preheat your kitchen oven empty and then with a cast iron skillet inside. The heat capacity is many times higher with the skillet vs just atmosphere.

drthip4peace t1_j5ud622 wrote on January 25, 2023 at 5:07 PM

ok well how is the camera accessing the part inside a container, inside a thermal chamber and why is a camera being used to measure temp and not a temp probe? If it is inside an oven and the question is why would one material in the oven not be the same temperature as other materials in the oven the conductivity of the materials is a logical answer especially since the material in question is a metal housing. Yes the reflection of light will influence measurements of light but there is no mention of light being reflected by the user I am assuming is familiar with the instrument they have chosen. Granted matter is limited but it surely within the realm of possibility that the metal housing is acting as heat sink. This is even more possible when the notion of moving air is added to the equation. Air moving over metal... what is the housing protecting the part from? The conditions should not be the same inside the housing as outside the housing because it would longer be a housing but just another part being heated returning me to my original point that the amount of energy required to raise the temp of the material will vary based upon the properties of the material. It just so happens that in this case known properties of the known materials suggest heat can and should be lost.

jermdizzle t1_j5ueeie wrote on January 25, 2023 at 5:15 PM

Hot air doesn't cool. Thermal cameras and ir thermometers give invalid readings of reflective surfaces. These are two facts that answer the op's question and they are both relevant to the scenario. I don't really have anything else to say because there isn't any more to say about the scenario.

drthip4peace t1_j5uhfkp wrote on January 25, 2023 at 5:34 PM

Hot air does cool according to the laws of thermodynamics, but sure ok the laws of the universe are suspended in this thermal chamber because of this mystical housing, that must be what it is protecting the part from, and it is a reflection that the OP fails to mention, why would it give a consistent reading of 85? SO this reflection is also amazingly consistent? The entire part on all sides has the same reflection? Wouldn't it or shouldn't it vary significantly based on anything that would impact the reflection? You are assuming that not only that this reflection exists, but that all of the variables that influence this reflection remain constant and unchanging because the result is unchanging. How improbable is that? You are welcome to make as many assumptions as you like but there is not reason that I must make the same assumptions or agree that your assumptions are correct.