What’s the ratio?
Does the heating component have to exceed, say, 300 F, in order to heat the incoming passing air to 150 F?
I’m not sure of the temperature, but I had to replace the heating element in mine a few years ago. With the cover off I noticed that it would glow red hot. It was made out of nichrome wire. The same kind of wire that is used to make those small space heaters.
Assuming we’re talking about immediately after the air passes the element, wouldn’t the element have to be the same temperature as the air that’s gone through it? The air cools the element just as much as the element heats the air. I wish I had the calculations to back that up, though.
I recently replaced a stuck thermostat in my dryer. Before it was fixed, I measured the air coming out of an (empty) dryer was about 190F. The thermostat is designed to cycle between 150-130 degrees.
Interestingly (at least to me), that’s measured after the air has gone through the clothes. Put a lot of wet clothes in there, and initially the exhaust temperature will struggle to break 90 degrees, slowly warming up as the water is evaporated.
I thought this might be an airflow issue, but I tried running my dryer with the door closed, and I could still see the heating element glowing for several seconds after I opened it. Maybe it is hotter than 190 after all? Hmm.
I’d say the elements get to around 1400F.
It takes about 1200F to glow a dull red in a darkened room. In “normal” room lighting, 1200 will usually appear black (or sliver, depending on the material*), perhaps a deep black red. Bright red, as you would normally see in a space heater, is somewhere around 1400F. By 1600F, the red will begin to show some orange.
*It really doesn’t matter what the material is in a darkened room. In school, I “recycled” some aluminum cans by melting them down in a furnace and making aluminum “Ingots” by casting them in plaster of Paris molds (for an “Engineering Day” exhibit). While the molten aluminum appeared silver under ambient light, I showed my audience that it was just reflection and by turning off the lights, you could see the dull red (the melting point of can-grade aluminum is around 1200F).
Interesting point about aluminium. I used to deliver to an aluminium smelter. At the gatehouse, I had to listen to a lecture and look at a card on safety. The most important was to stay well clear of any ingots that might be in the yard. They look cold but retain their heat for a long time. Driving past, maybe 6 or 8 feet away, I could feel the radiated heat through the open window.