Zeotropic mixtures study in plate heat exchangers and ORC systems

To our best knowledge, there are no correlations in the scientific literature to predict the twophase heat transfer coefficients of Hydrofluoroethers pure fluids and zeotropic mixtures used in plate heat exchangers. This work has allowed the development of evaporation and condensation correlations for such fluids. Correlations based on dimensionless numbers and working fluids critical properties gave promising results, with a prediction of the two-phase heat transfer coefficient around 15% for heat source and 50% for cooling source which lead respectively to a prediction of 4% and 6% for the global thermal power exchanged. The coupled operation between the heat exchangers and the organic Rankine cycle was also studied. For this purpose, the influence of the heat source variation on the performances of the hot exchanger and the overall cycle was analyzed. Results obtained showed a positive improvement simultaneously of the hot exchanger performances and the ORC performances. Regarding the use of zeotropic mixtures as working fluids in ORC system, it is often proposed in the literature as being able to significantly increase the performance of this thermodynamic cycle due to better heat transfer at the hot source. Nevertheless, the great majority of these studies are numerical and do not take into account the interactions and system effects existing within the thermodynamic cycle when using a mixture instead of a pure fluid. This work has allowed to highlight this complexity and to provide a better understanding of the use of zeotropic mixtures     «

To our best knowledge, there are no correlations in the scientific literature to predict the twophase heat transfer coefficients of Hydrofluoroethers pure fluids and zeotropic mixtures used in plate heat exchangers. This work has allowed the development of evaporation and condensation correlations for such fluids. Correlations based on dimensionless numbers and working fluids critical properties gave promising results, with a prediction of the two-phase heat transfer coefficient around 15% for h...     »