Sunday, Nov 22, 2009 at 09:28
Mainey...there is some truth in your statement. If a container is sealed(assuming a 100% seal), there is no path for the vapour to escape. In fact, the vapour will condense on the cooler surface (usually the lid) and then "rain" back down into the melting pot, so to speak.
However...... and this is the clincher. If a liquid is heated under pressure, the boiling pont at which that liquid will boil and evapourate will increase significantly depending on the sealing capabilities of the pressurized vessel. Hence, it would be possible to heat
water far beyond 100 degrees C without it actually boiling off. The danger is that there will come a time when the pressure in the vessel exceeds the safe working limits and Kaboom.
These principles work all the time in engine cooling systems which often operate above 100 degrees C. The "weak" point is the radiator cap. Designed in a way that it relieves the pressure before the hoses chuck a wobbly or worse still, the radiator core.
Cooling systems need this increased pressure to be able to work efficiently. Without a controlled pressurised system, most cars would require around 150 litres + of coolant to achieve the same efficiency as a 12 litre systems.
FollowupID:
660067