Enhanced Pool Boiling Heat Transfer on Mono and Multi-Layer Micro-Nano Bi-Porous Copper Surfaces
Boiling heat transfer is widely used in industry and aerospace, and it can be enhanced by surface structure treatment. Here, two types of Micro-Nano bi-porous copper surfaces (MNBPCS) were prepared by hydrogen bubble template method and then sintered in reducing atmosphere. The effect of surface morphology on the saturated pool boiling of ultrapure water was investigated. Results show that, both NMBPCS have superior heat transfer performance to the plain copper surface. When the heat flux is 100W/cm2, the wall superheat of the two MNBPCS are about 7 and 9 °C lower than the plain copper surface respective. When the heat flux is lower than 130W/cm2, the wall superheat of the mono-layer MNBPCS is lower than that of the multi-layer one, because the bubbles formed on the mono-layer MNBPCS can departure more easily than those on the multi-layer one. When the heat flux is higher than 130W/cm2, the multi-layer MNBPCS has lower wall superheat than that of the mono-layer one, own to its better liquid accommodation from the morphology structure. Significant hysteresis phenomenon was only found on the Multi-layer MNBPCS. Its wall superheat keeps almost the same at about 13°C for its bottom layer structure with smaller cave diameter, when the heat flux is higher than 75W/cm2. The CHF of each MNBPCS is higher than 200W/cm2, and the multi-layer one is higher than the mono-layer one own to its better liquid accommodation from the morphology structure.