制冷原理
Refrigeration Principle
液体汽化制冷是利用液体汽化时的吸热、冷凝时的放热效应来实现制冷的。液体汽化形成蒸汽。当液体（制冷工质）处在密闭的容器中时，此容器中除了液体及液体本身所产生的蒸汽外，不存在其他任何气体，液体和蒸汽将在某一压力下达到平衡，此时的汽体称为饱和蒸汽，压力称为饱和压力，温度称为饱和温度。
Liquid vaporization refrigeration uses the endothermic and exothermic effects of liquid vaporization and condensation to achieve refrigeration. The liquid vaporizes to form steam. When the liquid (refrigerant) is in a closed container, there is no other gas in the container except the liquid and the vapor generated by the liquid itself. The liquid and vapor will reach equilibrium under a certain pressure. At this time, the vapor body is called saturated vapor, the pressure is called saturated pressure, and the temperature is called saturated temperature.
平衡时液体不再汽化，这时如果将一部分蒸汽从容器中抽走，液体必然要继续汽化产生一部分蒸汽来维持这一平衡。 液体汽化时要吸收热量，此热量称为汽化潜热。汽化潜热来自被冷却对象，使被冷却对象变冷。
When the liquid is in equilibrium, it will not vaporize any more. If a part of the vapor is removed from the container, the liquid will continue to vaporize to produce a part of the vapor to maintain the equilibrium. When liquid vaporizes, it absorbs heat, which is called latent heat of vaporization. The latent heat of vaporization comes from the cooled object, which makes the cooled object cool.
为了使这一过程连续进行，就必须从容器中不断地抽走蒸汽，并使其凝结成液体后再回到容器中去。从容器中抽出的蒸汽如直接冷凝成液体，则所需冷却介质的温度比液体的蒸发温度还要低，我们希望蒸汽的冷凝是在常温下进行，因此需要将蒸汽的压力提高到常温下的饱和压力。
In order for this process to proceed continuously, steam must be continuously removed from the container, condensed into liquid and then returned to the container. If the vapor extracted from the container condenses directly into liquid, the temperature of the cooling medium is lower than the evaporation temperature of the liquid. We hope that the condensation of the vapor will take place at room temperature, so we need to raise the pressure of the vapor to the saturated pressure at room temperature.