TAGRA 2024

Two-phase flow with boiling and the heat transfer associated with these flows are gaining increasing importance in industrial applications due to the fact that they provide higher heat transfer coefficients compared to single-phase flows. In this study, the dynamic instabilities of two-phase flow in a horizontal empty pipe with a diameter of 13.7 mm were investigated using a forced convection boiling experimental setup. No heat transfer enhancement elements were used in the experiments, only the flow conditions in the empty pipe were analyzed. As a result of the experimental studies, it was observed that the period and amplitude of the density change type oscillations were lower than the pressure drop type oscillations. With the increase in the thermal power given to the system, the pressure drop in the two-phase region increased and it was determined that the minimum point on the characteristic curve shifted to the right. However, it was determined that the boiling point shifted to lower mass flow rates in case of a decrease in the fluid inlet temperature, i.e. an increase in the subcooling level. This study has shown that the effects on heat transfer in two-phase flow with boiling in an empty tube can be analyzed without using more complex geometries (internal spring, turbulence, etc.) and has revealed that the relationship between pressure drop and heat transfer performance is important in such systems. In general, the findings of the study have provided an important basis for the effective design of two-phase flow systems, especially in industrial applications.