Numerical Analysis of Enhanced Subcooled Boiling Heat Transfer in a Twisted Tri-Lobed Tube

This study presents a detailed investigation of subcooled boiling phenomenon in a twisted tri-lobed tube, aiming to elucidate its role in tube design and application in thermal management systems. Integrating the Eulerian twofluid model with the RPI wall boiling model, this study examines the influence of geometric parameters and boundary conditions in a twisted tri-lobed tube on heat transfer. Following validation with experimental data, the study spans a range of mass flux G=500-800 kg/(m2 center dot s), inlet subcooling Delta Tsub,inlet=25-55 K, heat flux qw=0.3-0.6 MW/m2, and outlet pressure Poutlet=5-8 MPa. Results show that increasing the minor radius (r) and straight segment length (l) and decreasing the transition radius (R), boosts secondary and helical flows but does not significantly affect the increase in wall void fraction. Furthermore, elevating the wall heat flux and outlet pressure, coupled with decreasing the inlet subcooling degree and mass flow flux, promotes subcooled boiling, thereby enhancing the average void fraction and convective heat transfer coefficient. Significantly, reducing Delta Tsub,inlet to 25 K allows the performance evaluation criterion (PEC) of the twisted tri-lobed tube to reach 2.18. The methodologies and findings of this study contribute significantly to a deeper understanding of subcooled boiling process in a twisted tri-lobed tube.