A novel, high-temperature, thermally-conductive, microporous coating (HTCMC) is developed by brazing copper particles onto a copper surface. This coating is more durable than many previous microporous coatings and also effectively creates reentrant cavities by optimizing brazing conditions. A parametric study of coating thicknesses of 49 - 283 μm with an average particle size of ～25 μm was conducted using the HTCMC coating to understand nucleate boiling heat transfer (NBHT) enhancement on porous surfaces. It was found that there are three porous coating regimes according to their thicknesses. The first regime is "microporous" in which both NBHT and critical heat flux (CHF) enhancements gradually grow as the coating thickness increases. The second regime is "microporous-to-porous transition" where NBHT is further enhanced at lower heat fluxes but decreases at higher heat fluxes for increasing thickness. CHF in this regime continues to increase as the coating thickness increases. The last regime is named as "porous", and both NBHT and CHF decrease as the coating thickness increases further than that of the other two regimes. The maximum nucleate boiling heat transfer coefficient observed was ～350,000 W/m~2K at 96 μm thickness ("microporous" regime) and the maximum CHF observed was ～2.1 MW/m~2 at ～225 μm thickness ("porous" regime).
展开▼
机译：通过将铜颗粒钎焊到铜表面上，开发了一种新型的高温导热微孔涂层（HTCMC）。这种涂层比许多以前的微孔涂层更耐用，并且还通过优化钎焊条件有效地形成凹腔。使用HTCMC涂层对涂层厚度为49-283μm，平均粒径为〜25μm进行了参数研究，以了解多孔表面上核沸腾传热（NBHT）的增强。发现根据其厚度存在三种多孔涂层方案。第一种方式是“微孔”，其中随着涂层厚度的增加，NBHT和临界热通量（CHF）的增强都逐渐增长。第二种方案是“微孔到孔的转变”，其中NBHT在较低的热通量下会进一步增强，而在较高的热通量下会增加厚度而降低。在这种情况下，CHF会随着涂层厚度的增加而继续增加。最后一个方案称为“多孔”，并且与其他两个方案相比，随着涂层厚度的增加，NBHT和CHF均降低。在厚度为96μm的情况下（“微孔”状态）观察到的最大核沸腾传热系数为〜350,000 W / m〜2K，在厚度为225μm的情况下（“多孔”状态）观察到的最大CHF为〜2.1 MW / m〜2。 。
展开▼
