Advanced Fundamental Studies on Supercritical Fluids

超临界流体是压力高于临界压力的流体(临界压力和温度是临界点的特征，在该临界点，液体和汽相之间的区别消失，即两相具有相同的温度、压力和体积)。水的临界参数为22.1兆帕，温度为374摄氏度；二氧化碳的临界参数为-7.4摄氏度和31摄氏度；R-134a-4.1和101摄氏度。超临界流体表现出一套独特的性质，允许在加热过程中储存大量能量，并在冷却或通过涡轮机膨胀过程中回收这些能量，这使它们成为各种工业和实验室应用中的理想工作液或冷却剂。超临界流体最大的工业应用是在超临界压力燃煤电厂的电力工业中广泛使用超临界水，与其他电厂相比，这些电厂具有相当高的热效率(高达55%)。然而，这些流体还有许多其他应用领域，如第四代核反应堆概念中的冷却剂(超临界水和氦)；这些反应堆的动力循环(超临界水、氦和二氧化碳)等。

Supercritical fluids are fluids at pressures above a critical pressure (critical pressure and temperature are characteristics of a critical point in which the distinction between the liquid and vapour phases disappears, i.e., both phases have the same temperature, pressure and volume). Critical parameters for water are pressure of 22.1 MPa and temperature of 374 C; for carbon dioxide - 7.4 and 31 C; and for R-134a - 4.1 and 101 C; respectively. Supercritical fluids exhibit a unique set of properties, which allow to store a lot of energy during heating and retrieve this energy during cooling or during expansion through a turbine, which make them ideal working fluids or coolants for use in a variety of industrial and laboratory applications. The largest industrial application of supercritical fluids is the extensive use of supercritical water in power industry in supercritical-pressure coal-fired power plants, which have quite high thermal efficiency (up to 55%) compared to other power plants. However, there are many other areas of application for these fluids such as coolants in Generation-IV nuclear-reactor concepts (supercritical water and helium); in power cycles of these reactors (supercritical water, helium and carbon dioxide); etc.