A comparative analysis of a CO2 evaporator model using experimental heat transfer correlations and a flow pattern map

This work analyses and compares two approaches to evaluate the boiling heat transfer of CO2 in a real evaporation process: classical empirical correlations and flow pattern maps. We develop a finite-volume mathematical model of an evaporator to contrast both approaches and simulate it with four empirical correlations, not developed for CO2 but tested successfully with it, and a flow pattern map specific for CO2. We contrast the results of the simulation with 73 experimental steady-states performed with a transcritical CO2 refrigeration plant that incorporates a concentric counter current evaporator. We observe that both approaches can predict the evaporation process of CO2, nonetheless, in spite of the more complex mathematical formulation, the considered flow pattern map allows to obtain more precision.