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Civil Engineering

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Fluid Properties

Vapor Pressure and Boiling Behavior

Description

Vapor pressure and boiling behavior are closely linked in fluids. Vapor pressure is the pressure a vapor exerts when it is in thermodynamic equilibrium with its liquid at a given temperature. It shows how strongly molecules tend to leave the liquid surface and move into the vapor phase.

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Transcript

蒸气压是指在给定温度下,蒸气与其液体处于平衡状态时所产生的压力,它反映了分子从液体表面逸出的倾向,并影响沸腾和空化现象。

在密闭的真空容器中,液体分子会逸散到空间中,使压力升高,直至达到平衡状态,即逸出的分子速率等于返回的分子速率。此平衡压力即为蒸气压。

蒸气压取决于温度。随着温度升高,分子获得动能,更容易克服分子间作用力而进入气相,从而导致蒸气压升高。

例如,100°C 的水具有 101.3 kPa 的蒸气压, 该压力与海平面处的大气压相等,因此水会沸腾。在较高海拔地区,由于大气压较低,水在更低的温度下就会沸腾,因为其蒸气压能更快地达到降低后的大气压。

监测蒸气压对于设计和运行泵与涡轮机以防止气蚀至关重要。

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