Entropy Generation of Two-Phase Flow Boiling in Elliptical U-Bend Tube Heat Exchanger

Abstract

In this research paper, the entropy generation was used as a criterion to measure the quality level of energy transfer for two-phase flow boiling of R134a in the elliptical U-bend tube. The eccentricities of the elliptical cross-section ranging from 0 to 0.904, were constrained to the same hydraulic diameter of 8 mm. The input parameters utilized in the numerical computations were mass velocities of 100 and 200 kg/m2 s for the inlet vapor qualities of 0.1 and 0.2 and a constant uniform heat flux of 10 kW/m2 imposed on the outer surface of the tube. The calculations were performed using the volume of fluid multiphase model coupled with the phase change model. The findings demonstrated that when the eccentricity of the U-bend tube increases, the quality of energy transfer in the heat exchanger improves as entropy generation reduces. The numerical calculations were validated and found to be consistent with what has been published in the open literature. The results of this paper are important for the development of heat exchangers for air conditioners and refrigerators.