|
|
Forums:
Climbing Information:
Gear Heads:
Re: [patto] Worst modern belay devices:
Edit Log
|
|
petsfed
Aug 25, 2009, 1:42 AM
Views: 2605
Registered: Sep 25, 2002
Posts: 8599
|
patto wrote: You cleary have little understanding of the physics involved here. Increased mass will always result in a lower peak temperature achieved. Increased surface area will always increase the rate of cooling and thus lower peak temperature.
Lemme make sure I understand your argument here:
By increasing the mass, we decrease the maximum temperature achieved.
WHICH IS PRECISELY WHAT I SAID IF YOU'D BOTHERED TO READ IT.
I said that we can't simply compare a pyramid with fins to a pyramid without fins since a pyramid that simply lacks fins will have lower mass.
And again, the issue is not of overall heat in the system, it is heat that remains in the device.
And ANYBODY who says that a rappel device shouldn't heat up that much has NEVER done a 60m rappel on dual 10.5mm ropes, much less a fast rappel.
Should I write out the energy in/energy out equations so you can see why a fast rappel would heat up the device faster than a slow rappel? Or can you work that out yourself?
Edit: because this really pisses me off.
Heat capacity is a measure of how much energy, per gram, it takes to heat a given material a single degree Kelvin. I'm not fucking stupid, I just doubted that our audience would necessarily know what I meant when I said that. So it should be pretty apparent that, all else being equal, a higher mass object will cool or heat slower than a lower mass object. But all else is NOT equal here. We're fiddling with the surface area AND the mass. So simple experimental design says that we should keep the mass constant to isolate the variable we are testing for, namely cooling due to increased surface area. Otherwise, how could we show that the device is or isn't cooling faster due to the fins, rather than due to the fact that the cooling and heating rates are also dependent on the temperature differential between source and sink?
(This post was edited by petsfed on Aug 25, 2009, 1:59 AM)
|
|
|
Edit Log:
|
|
Post edited by petsfed
() on Aug 25, 2009, 1:59 AM
|
|
|
|
|
|
