The shell of the steam jet pump is cold
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The steam jet pump I use for vacuum creation uses 10 kilograms of steam at 250 degrees Celsius as the pumping medium; logically, the casing should be hot during operation, right? Why is the outer shell actually cold, while both ends are hot?
Throttling expansion is endothermic; during steam throttling expansion, internal energy and kinetic energy undergo conversion.
The throat tube was cold at first, and then it gradually warmed up. Before reaching the throat, the thermal energy of the steam is converted into kinetic energy, and the speed increases gradually until it reaches supersonic levels; thereafter, the kinetic energy is transformed back into thermal energy, causing the temperature to rise.