NH_Wood said:
I'm with you on the above. But, wouldn't the radiant heat hitting the object in front of the glass warm the object and the object would then radiate that heat back into the room? Wouldn't this be the same for the dirty glass? The heat energy isn't magically disappearing when the glass is dirty. If the window were completely replaced with more cast or steel, would the heat output in the home drop dramatically? Again, what I'm saying is could cleaning the glass contribute to noticeable heat increase in the home? Still don't buy it. I need BK to run some numbers! :cheese:
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Radiant heat hitting the object then be re-radiated would be greatly diminished because that heat would also be radiating back into the fire as well so it's really not a direct comparison.
woodgeek said:
Dude, give me a break. If you think the radiant energy from the fire goes through the window, then the expt is to compare radiant heat with the doors open and closed! And I think we all know the radiant flux we feel is WAY higher with the doors open than closed. The radiant heat you feel sitting in front of the window is b/c the window itself is hot, so it radiates too. To a first approximation, if you put steel plate in place of your windows, you would feel pretty much the same thing.
Along the same lines, point an IR therm at the doors when closed, and then at the fire with the doors open. Then point the IR through the hot, open window at a cold wall. Does it now read the temp of the wall, or the same hot window temp? The huge diff in readings will suggest that the radiation the IR thermo measures sure doesn't get through. Of course, the stove puts out energy at different wavelengths that the IR therm reads as well, but basically, the window blocks radiant energy, and is engineered to do that.
Absolutely nothing that you have suggested is logical or proper in determining if the glass is allowing radiation to pass.
It is absolutely not possible for any glass to pass 100% radiation. If glass passed 100% radiation then it wouldn't ever heat up from radiation hitting it. If you have a stove with an air-wash to keep hot convective currents off the glass then this means your glass will never get hot.But guess what, even with the air wash the glass gets hot. So we have now established that the glass at least partially absorbs radiant heat. However, with suggestion #1 above you illogical concluded that bc your glass absorbs some radiant heat it must absorb it all.
Did it occur to you that maybe it is only absorbing some radiant heat? When I shoot the temp of my glass it normally shows around 1000 degrees. Do you think my glass is really that hot or do you think maybe there is also some radiation passing through and throwing off the temp? I think the temp and/or radiant feeling you get is a combination of both.
next you illogically concluded that because your IR thermo says the fire is hotter than the doors that they aren't passing radiation is along the same lines. It doesn't at all prove that no radiation is coming through the doors, it just proves that not all of it is coming through.
Lastly we come to the final very, very wrong conclusion that when the IR thermo is pointed through the door at a cold wall the radiation doesn't pass if the temp doesn't read similar to the cold wall. If you think that will tell you anything then you clealry don't understand radiation. The IR thermo is basically just "adding up" all the radiation it is seeing. The hot door is still radiating heat itself, the radiation of the wall is so small compared to the door that you will, in all reality, just be "seeing" the door.
A better comparison to determine if you're seeing any radiation through the glass is to point the IR thermo at the closed, hot door with a good, hot fire going, note the reading. Then open the door and point the IR thermo through the door at a cool wall. If the second reading is any lower than the first then you are, in fact, seeing radiation through the glass.
No need to let me know your results, I already know the answer.
BTW, to the OP, yes, I also notice an increase in radiant heat after cleaning the glass.