Effect of stagger angle on capillary performance of microgroove structures with reentrant cavities

Aluminum-based microgroove surfaces with reentrant cavities (MSRCs) were fabricated by two staggered ploughing/extrusion processes to meet the requirements of lightweight phase change heat transfer devices. Five MSRCs with different stagger angles between cavities and microgrooves (MGs) were fabricated to study the effect of stagger angle on capillary performance. Capillary rise and permeability tests were performed on all MSRCs and the results were compared with MGs having the same processing parameters. It was found that MSRCs with smaller stagger angles have higher capillary height, and the maximum enhancement maintained by MSRC45 was about 54.84%. However, MSRCs with larger stagger angles were found to have higher permeability. Therefore, the capillary parameter K center dot Delta P-cap was used as a comprehensive index to evaluate these wicks. MSRC90 and MSRC75 obtained the largest K center dot Delta P-cap values without and with the effect of gravity considered, respectively. Although all MSRCs had a higher capillary rise height than MGs, smaller stagger angles (<= 60 degrees) seriously reduced the permeability of MSRCs and even resulted in smaller K center dot Delta P-cap value than that of MGs when calculated considering the effect of gravity. Therefore, MSRCs with larger stagger angles (>= 75 degrees) may be the optimum wicks due to the good balance between capillary pressure and permeability.

Automated summary

Aluminum-based microgroove surfaces with reentrant cavities were fabricated to study the effects of stagger angle on capillary performance. Results showed that smaller stagger angles led to higher capillary rise height but reduced permeability, while larger stagger angles resulted in higher permeability. Therefore, MSRCs with larger stagger angles (>= 75 degrees) may be the optimal wicks.