On Sun, 2005-03-06 at 02:20 +0100, Markus Huber wrote: > Graham Campbell wrote: > > > I am an old-timer and remember the big old mainframes, especially the > > CDC 6600 and CDC 7600. These were cooled with circulating refrigerant. > > An undisciplined power outage definitely caused problems due to spiking > > temps. CDC did a study that showed a dramatic increase in failures about > > 7 days (as I recall) after a power failure. > > I am not that expert on this one, but isn't cooling with a refrigerant > similar to a car engine? The temperature of the refrigerant is going up > because it stopped circulating? > > But most of modern PCs are air-cooled like old Porsches or VW Beatles, > and you *were* able to cool down overheated engines by switching off the > engine. > I think the key to understanding this is the difference between heat and temperature. Liquid coolants differ from gas coolants only in the magnitude of the thermal properties things like heat capacity, etc. (I never learned thermodynamics very well). However the main idea is that if you change heat flow patterns dramatically, then temperatures will also change dramatically. Eventually everything will again reach a steady state with a lower temperature. > If a modern car overheats, you should not switch it off immediatly > because of the refrigerant. > > -- > Regards > Markus Huber > -- Graham Campbell <gc1111@xxxxxxxxxxxxx>
