The flow boiling heat transfer process of R404A in small-diameter tubes is a very complex physical phenomenon. At present

research on the heat transfer characteristics of R404A is mostly focused on large-diameter tubes

and there has been little research on small-diameter tubes

despite the different mechanisms underlying the experimental phenomena. Therefore

there is a strong need for specific experimental data to support the theoretical study of the heat transfer characteristics of R404A in small-diameter tubes. An experimental platform for evaporation in small-diameter micro-fin copper tubes was constructed

and the effects of heat flux

evaporation quality

mass flux

and saturation temperature on the heat transfer coefficient in the process of R404A flow boiling heat transfer was investigated. Each factor was studied independently

with all variables other than the particular one under consideration held constant throughout the analysis. The research results shows that the heat flux

quality

mass flux

and saturation temperature all have a significant influence on the heat transfer characteristics of R404A in small-diameter tubes

with the effects of these factors varying before and after dryout. Furthermore

these factors have a direct influence on the initial quality of dryout

the main form of heat transfer

and the occurrence of dryout.