Abstract
Microchannel structures possess high efficiency and high boiling heat transfer coefficient of two-phase flow. In particular, the grid structure has the advantages of a simple pattern, large load capacity, and good surface adaptability. Employing the laser-based powder bed fusion (L-PBF) manufacturing technology, a new method of forming heat transfer grids with a controllable structure is proposed in this study. The formation principle, process, and the reasons for improvements in the boiling heat transfer performance were investigated with stainless steel materials. Laser scanning with varying scan spacings was used to prepare multiple structures with different grid widths and wall heights. On this basis, the porosity and pore morphology of the grid structures were analyzed, followed by pool boiling heat transfer experiments. The results revealed that the grid structure significantly affected the nucleate boiling behavior and increased the critical heat flux (CHF). It was found that the 0.5 mm sample exhibited optimum critical heat transfer performance, with an improvement of 10–27% compared to those of the other four samples (minimum of 63.3 W·cm−2 and maximum of 93.9 W·cm−2). In addition, for samples with a grid width greater than 0.5 mm, the boiling slightly decreased by <5%. When the grid width was further increased, the flow resistance effect and the bubble synapse generation effect tended to converge. In these cases, boiling heat transfer only occurred in a single phase along the direction of the medium wall thickness, thus failing to achieve two-phase heat transfer through bubble growth and collapse.
Highlights
Publisher’s Note: MDPI stays neutralImproving surface structures [1], which typically include grooves, fins, and porous surfaces of various shapes, is the main approach adopted for enhancing boiling heat transfer
Among the main factors that influence the enhancement of boiling heat transfer b Among the main factors that influence the enhancement of boiling heat transfer by the microgrid structure are its material, pore morphology, and structural parameters
To analyze the effect of the grid size on the boiling heat transfer process, the grid structure samples formed at different scan spacings were tested using the boiling heat transfer test platform mentioned in the previous section
Summary
Improving surface structures [1], which typically include grooves, fins, and porous surfaces of various shapes, is the main approach adopted for enhancing boiling heat transfer. Wong and Leong [23] studied the saturated pool boiling performance of a porous lattice structure prepared by L-PBF and found that the porous structure exhibited a significantly enhanced nucleate boiling heat transfer coefficient and a CHF delay relative to a flat surface. L-PBF technology constitutes a parameters onapproach boiling heat transfer and the enhancement discussed, new effective for manufacturing innovative boilingmechanism heat transferwere structures with providing important guidance the design of 3D structured transfer for controllable parameters, whichfor opens up a new direction for heat the study of channels boiling heat boiling transferenhancement. L-PBF technology constitutes a new effective approach for manufacturing innovative boiling heat transfer structures with controllable parameters, which opens Experimental up a new direction for the study of boiling heat transfer mechanisms
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