Simulation study on bubble growth and boiling heat transfer characteristics of R170/R1234ze(E) zeotropic mixture

For guiding the design and optimization of heat exchangers, bubble growth and heat transfer characteristics are significant. The mixed refrigerant R170/R1234ze(E) has the advantages of low GWP, large volume cooling capacity and low flammability. It holds significant potential for applications in the refrigeration field. Hence, it is necessary to conduct comprehensive research on the heat transfer properties and bubble growth dynamics of R170/R1234ze(E). In this paper, the numerical simulations of R170, R1234ze(E) and their mixtures were carried out by FLUENT with the heat flux of 10.6-75.0 kW m-2 and pressure of 0.2-0.415 MPa. The bubble growth time, bubble departure diameter as well as heat transfer are analyzed in detail. The findings indicate that the bubble growth time decreases with increasing heat flux and increases with the rise of saturation pressure. The departure diameter of bubble both mixtures and pure fluids increases with increasing heat flux and decreases with increasing saturation pressure. In addition, bubble size, bubble growth time increase first, and then decrease with the R170 concentration, but they exhibit different change trends. Moreover, pure heat transfer coefficient is always higher than the mixture.