Effect of Refrigerant Properties Estimation on the Prediction Capabilities of Well-Established Two-Phase Heat Transfer and Pressure Drop Models for New Refrigerants. (August 2020) - Righetti, G
Abstract: R1233zd(E) and R1224yd(Z) are two HCFO (Hydro Chloro Fluoro Olefin) low-GWP refrigerants recently proposed as substitutes of the HFC (Hydro Fluoro Carbon) fluids commonly used in air conditioning, high temperature heat pumps and ORC applications. A few experimental works regarding the two phase heat transfer in small diameter smooth and microfin tubes have already been published in the open literature. The estimations of thermophysical properties may have a remarkable impact on the prediction of the heat transfer coefficients and pressure drops, especially during two-phase heat transfer. The thermophysical properties databases and predictive tools for these refrigerants are continuously being updated and improved as additional, accurate measurements are published in the open literature. The present paper aims to highlight the impacts of thermophysical properties prediction models on the consistency of estimations of heat transfer coefficient and pressure drop using correlations published in the open literature. As a benchmark, some experimental heat transfer and pressure drop data collected for two new HCFOs, R1233zd(E) and R1224yd(Z) are used. The experimental database has been collected at the Department of Management and Engineering of the University of Padova. For the thermophysical properties estimations, different Equations of States contained in REFPROP as well as a more "simplified" approach based on group contribution methods coupled with a Peng-Robinson Equation of State, are considered.