Strategy for Chemical Analysis of Alternative Refrigerants

摘要

The chemical purity of samples of alternative refrigerants which are used in the determination of the thermophysical properties is of paramount importance. Many properties, such as vapor-liquid equilibria and transport properties such as thermal conductivity, require that measurements be performed on as pure a material as possible. Some common impurities such as water can have an extremely deleterious effect on a measurement, while the effects of other impurities are more subtle. Alternative refrigerants which are not available at purity levels that are normally considered 'research grade' must be characterized in order for the data to be properly interpreted, and for the reported results to be used appropriately. In addition, it is necessary to assess the reactivity of alternative refrigerants in the presence of many of the common construction materials used in experimental apparatus. The National Institute of Standards and Technology has evolved an analytical protocol which is applied to each system. In the paper, the various analytical methods will be discussed, and the data of general usefulness presented. In addition, some of the novel instrumental approaches employed at NIST will be described.