Looking up in tables, I see that aluminum and ceramics like brick or concrete have approximately equal specific heats: about 0.21 cal/gram°C. However it occurs to me that this doesn’t necessarily equate with how fast they heat up and cool down, because they might not couple with radiant heat equally well- I would conjecture that being a metal, aluminum does so more readily than brick. So which effectively heats up and cools down faster, and what’s the technical term to describe this?
Aluminum heats and cools much faster than brick. A brick oven will stay hot for hours but takes hours to heat up. A block of aluminum will cool down rather quickly.
I don’t know the right technical term here, but heat is transferred more slowly through brick than through aluminum. It takes longer to heat the brick, and it stays hot longer.
If I understand what you are asking, the technical term is thermal conductivity. Depending on the context this can also be expressed as the heat transfer coefficient or the thermal resistance or R-value (thermal resistance is the inverse of thermal conductivity, so it’s different ways of expressing the same thing).
Here’s a table of thermal conductivity.
According to this table, aluminum is 205 while a typical brick is somewhere between 0.6 and 1. So yeah, an aluminum block will transfer heat a lot faster than a brick. A LOT faster. Exactly how much faster leads to some surprisingly complex math. Thermodynamic calculations have always given me the willies.
In my youth I worked one summer holiday in a brick factory. The bricks, after being shaped and dried, were stacked in an oven with a very tall chimney. A coke fire was lit in the middle and the door sealed for 24 hours or so. They would reach 1000 degrees C and I can tell you that they took a long time to cool down. It was part of my job to load them by hand onto lorries. We would form a chain, taking newly made bricks from a stack and passing then, four at a time, to the guy on the truck bed. We all wore a leather palm, not a glove but it just hooked on the wrist to protect the hands. Sweaty work…
On the other hand, during a more recent spell as a truck driver, I used to deliver regularly to an aluminium smelter. They had a one way system round the plant that took me past a yard where large ingots were stored. There was a safety fence and big signs to keep us away and when I stopped near one once, I could feel the heat radiating from it - It looked cold, but was probably many 100s of degrees C.
What do you mean by “couple with radiant heat”, Lumpy? What thermal conductivity will mean for the heating and cooling of “equivalent” bits of brick and aluminium is that the aluminium will conduct heat quicker throughout the volume and have less of a temperature difference. So if you turn a source of radiant heat on them the surface of the brick will heat up faster and radiate some of the heat back out while the absorbed heat slowly “soaks” through the rest.
But of course they would also have different absorption profiles, which is why we use polished metals as mirrors, so the aluminium could very well be slower to heat up than the brick.
I meant in the sense of how perfect a “black body” each might be. But after reading the responses it seems thermal conductivity is the more important factor. The exterior of a heated brick might cool faster but it will radiate heat for a longer time.
Long story short, I was checking out the specific heat of baking stones vs. cast iron, and noticed that for a metal aluminum has a rather high specific heat (per gram that is, probably due to it’s light atomic weight more than anything). And I was wondering at how different its thermal characteristics were from the otherwise comparable brick.