Pool Boiling Heat Transfer Characteristics of HFO 1234yf on Plain and Microporous Enhanced Surfaces

Abstract

This study characterizes the pool boiling performance of HFO1234yf (hydrofluoroolefin 2,3,3,3tetrafluoropropene). HFO1234yf is a new, environmentally friendly refrigerant likely to replace HFC134a in automotive airconditioning systems. Pool boiling experiments were conducted at system pressures ranging from 0.7 to 1.7 MPa using horizontally oriented 1cm2 heated surfaces. Test results for pure (oilfree) HFO1234yf and HFC134a were compared. The results showed that the boiling heat transfer coefficients of HFO1234yf and HFC134a were nearly identical at lower heat fluxes. HFO1234yf yielded lower heat transfer coefficients at higher heat fluxes and lower critical heat flux (CHF) values as compared with HFC134a. To enhance boiling heat transfer, a copper microporous coating was applied to the test surfaces. The coating enhanced both the boiling heat transfer coefficients and CHF for both refrigerants at all tested pressures. Increasing pressure decreased the level of heat transfer coefficient enhancements and increased the level of CHF enhancements. The experimental data were then used to develop a correlation for predicting the CHF for a smooth/plain heated surface.