Improvement of numerical tool for calculating thermodynamic and physical properties and its application to sliding vane compressors modelling

This works presents the development of a practical and fast numerical tool for calculating thermodynamic and physical properties of pure fluids and mixtures applying two different approaches referred as the indirect method (ideal gas and liquid modeling) and the direct method (real fluids based on cubic equations of state modeling). It is implemented on Matlab R with a fully vectorized architecture. A validation is performed against the reference commercial software REFPROP using five study cases with the following fluids: industrial solvent, natural gas, humid air, saturated steam and freon. The results show a relative error lower than 7% which tends to decrease as the fluid approaches ideal gas conditions, this is a positive result considering that the reference software is highly more sophisticated. The numerical tool is then integrated with a global design tool for sliding vane compressors and expanders which are designed by Ing. Enea Mattei, allowing it to describe with increased detail the thermodynamic and heat transfer processes occur- ring inside the machine. This upgrade also allows to model any working fluid. A final validation is performed against experimental data of a 75kW air com- pressor and the results show an overestimation of the fluid pressure up to 6% which is linked to the limitations of the heat transfer model, specially regard- ing oil properties and air to oil ratios. The higher fluid pressure is also linked to the presence of leakages that were not accounted. The future work for the properties tool is adding more sophisticated EOS and improve the routines related to vapor liquid equilibrium; instead for the compressor design tool is necessary to improve the prediction of oil properties and to include empirical correlations for leakages flows into the thermodynamic model.