fluent中不用nist调用，而用这个文件加载co2的物性，计算更快更准-fluent in not nist call, and use this file to load properties co2 calculate faster and more accurate

超临界二氧化碳工质调用NIST的函数代码，可以直接接入所建立模型中(The function code of the supercritical carbon dioxide working fluid calling NIST can be directly connected to the established model.)

一种通过定义一个流场类，使用CoolProp调用Nist二氧化碳真实物性的方法(A method of using coolprop to call NIST carbon dioxide physical properties by defining a flow field class)