36. Phase Transitions
A. Use phenomena occurring during phase transitions (e.g., volume changes, loss of absorption of heat, etc.).
Example:
• To control the expansion of ribbed pipes, they are filled with water and cooled to a freezing temperature.
• Water expands when frozen, unlike other liquids. Hannibal is reputed to have used this when he marched on Rome a few thousand years ago. Large rocks blocked passages in the Alps. He poured water on them at night. The overnight cold froze the water, and the expansion split the rocks into small pieces that could be pushed aside.
• Heat pumps use the heat of vaporization and heat of condensation of a closed thermodynamic cycle to do useful work.
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