Analysis of CoolProp library for the assessment of uncertainty propagation for refrigerant fluids in state diagrams and thermodynamic properties

The performance evaluation of vapor compression and Organic Rankine Cycles relies on the employment of thermophysical libraries. The evaluation of enthalpy, for example, requires the prediction of specific heat. Thermophysical properties, in turn, depend on the state of the fluid, and thus the library is needed. The actual state of the fluid can be obtained by measuring two state properties. Typically, pressure and temperature are evaluated by means of thermocouples and pressure sensors. These measurements are affected by uncertainty, that propagates when the quantities are combined. A physical quantity calculated starting from temperature and pressure is affected by an uncertainty that is a function of the one related to the measurement of the two base quantities and of the thermophysical library employed. This can indeed propagate differently the two starting uncertainty magnifying the contribution of temperature rather than pressure. In this work the propagation of temperature and pressure uncertainty in relation to the enthalpy calculation through the CoolProp library is investigated. The procedure is applied to a number of pure refrigerants and a mixture of common use in the engineering practice. The database reported can be of help to estimate the propagation of the uncertainty in the most common engineering application.