raumvogel wrote:QUOTE (raumvogel @ Feb 16 2015, 07:30 PM) I know it's not on topic........
.....but my Elzam detector just wen't off.
Oh Noodle is definitely Elzam. Completely obnoxious in game and out, marginally competent at whatever he's trying to say or do at best... the only question is how P32 can stand the $#@!er.
lexaal wrote:QUOTE (lexaal @ Feb 18 2015, 12:24 PM) I wonder/ would like to know:
-if volume changing effects(=movement) at the moment of freezin are relevant or can be ignored completely.
-why convection get more relevant for ice cubes compared to bottle (smaller volume --> higher damping trough wall friction --> less convection in my theory)
-how much is typical undercooling of normal and distilled water? We made some measures at university but usually our temp sensor was the "freezing seed"
-if the PDE which is (with cooling) a highly nonlinear ("reaction*") diffusion convection nighmare is solvable.
-(slightly off-topic): I read that full freezers require less energy than empty freezers... but since interiour temperature is regulated(= constant) the surface and temperature both difference don't change...so why?
-why do some people on the internet still say hot liquids are frozen faster than cold liquids?
-Yes, volume changing effects would be relevant if they were sufficient. While liquids aren't ideal gasses by a long shot (only being somewhat compressible), it's still generally true that by compressing a body of water you'll increase the latent heat in it. After all, by compressing the water you're doing work on it
-It's the convection of the air around it which is relevant rather than the convection in the water. Water's convection isn't particularly relevant towards how the ice forms insofar as where the ice forms. It's still going to form in shallow areas that are exposed to convecting or strong conducting effects. What convection in the water *does* change is which specific water molecules freeze at what particular point but... meh.
-about 50C or so below 0 for purified water. Other than that, "normal" water is going to need a better definition
Depends on what's in your wells.
-Couldn't tell you. I suspect it is but also not worth solving.
-The reason full freezers take less energy to run is because there's more *stuff* in a full freezer. that might not make a whole lot of sense, but remember that temperature is a measurement of the average kinetic energy of every particle. In an "empty" freezer, this is a relatively small bit of gas. In a freezer stocked to the gills with frozen fish sticks and ice-cream, there's a lot more *stuff* in there. So if you add a small amount of energy (because it leaks in through the freezer's insulation, for example) it doesn't raise the internal temperature by all that much.
-Because there are a lot of morons on the internet. It's actually not a particularly unintuitive effect if you understand what "hot water freezes faster than cold" is actually saying. Here's a quick primer I found:
http://math.ucr.edu/home/baez/physics/General/hot_water.html
Basically the gist of it is, we're assuming that we have two equal volumes of water at different temperatures. Unfortunately we can't control important other things like the gas content of the water and the convection currents might end up slightly different in each of them. In this case we're more accurately comparing apples and pears than red apples and green apples.
