Enhancing pool boiling with separated liquid-vapor pathways on perforated micromesh surface

Abstract

Boiling heat transfer has been utilized in many industrial applications, including thermal power plants, air conditioners, and thermal management of electronics and data centers. Micro/nano-structured surfaces have been developed to enhance the key performance metrics of boiling, including heat transfer coefficient (HTC) and critical heat flux (CHF). Porous structures, such as sintered micromesh and packed micropowders, show great promise in promoting bubble nucleation. However, the conflicting requirements of HTC and CHF for surface structures make it challenging to simultaneously enhance both CHF and HTC on porous surfaces. In this work, stacked micromesh surfaces are perforated to enhance bubble nucleation, and facilitate bubble escape and liquid delivery through separated liquid and vapor pathways. Nucleated bubbles within the micromesh pores can easily escape through perforations due to low flow resistance, significantly augmenting HTC. Liquid supply is improved due to decreased obstruction of vapor bubbles in liquid pathways, leading to enhancement of CHF. Both visualization of bubble dynamics and theoretical analysis of liquid-vapor transport are conducted to demonstrate the effectiveness of perforation design for the separation of liquid and vapor transport. Significant enhancements are demonstrated on the perforated micromesh surface with a perforation spacing of 2 mm compared to a smooth copper surface, with HTC and CHF increasing by 598 % and 136 %, respectively.