关键词: 微通道, 传热, 两相流, 激光直写, 多孔结构

Abstract:

As an efficient heat dissipation device, microchannel heat sinks have been widely used to solve the problem of high heat flux dissipation in micro-electronic devices, photoelectricity, automotive, aerospace industries and energy field and so on. To solve the problems of small heat transfer area, low heat transfer performance and boiling hysteresis of traditional smooth microchannels, a porous wall microchannel structure was proposed in this paper, and laser direct writing method was used to prepare efficient and stable porous wall microchannels. The porous wall microchannel significantly increases the heat transfer area, promotes the disturbance of the fluid, and provides many stable boiling cores, thereby enhancing single-phase and two-phase heat transfer. By building a microchannel heat transfer performance test system, the single-phase and two-phase heat transfer performance of porous wall microchannels and smooth microchannels were tested and compared. Experimental results indicated that the Nu number of porous wall microchannel was increased by 21%—31% compared with the untreated rectangular microchannel. In two-phase boiling heat transfer, porous structure promoted the nucleation of boiling bubbles and reduced the onset temperature of nucleate boiling (ONB), which was 35% lower than that of the untreated rectangular microchannel. At the same time, porous structure could ensure continuous liquid supply during the boiling process, thereby greatly improving the boiling heat transfer performance and avoiding the occurrence of drying out in advance. The two-phase boiling heat transfer coefficient h_tp was up to 83% higher than that of the untreated rectangular microchannel. The two-phase heat transfer coefficient h_tp of porous wall microchannel structure at the mass flux of G=500kg/(m²·s) was increased by 30% compared with that at the mass flux of G=200kg/(m²·s).

Key words: microchannel, heat transfer, two-phase flow, laser direct writing, porous structure