The Research Of Heat Transfer Characteristics Of Nano Porous Surface Under High Heat Flux

With the rapid development of microelectronics technology, electronic frequency and integration has become higher and higher, which devote to the increasing of power consumption and the produced heat per unit area of electronic components. If the heat can’t be dissipated in time, the devices’ temperature will increase dramatically and affect its performance and service life. Thus, the thermal barrier brought from the increased temperature has blocked the development of high-integrated electronic components technology seriously. Nowadays, the traditional cooling methods can’t meet the demands of heat dissipation of microelectronic components under high heating flux. In this paper, some surfaces, i.e. nano porous surface(N), microgrooves surface(M), and N-M coupled surface were formed on aluminum by anodic oxidation and micromachining technology successfully. Moreover, the pool boiling heat transfer performance of these surfaces were studied and compared with that of smooth surface. The results showed that:The morphology of the nano porous surface will vary with the anodic oxidation technology and finally affect its heat transfer performance. In this article, nano pore arrays surface whose pore diameter is about 80 nm was formed by anodic oxidation with oxidation voltage 40 V, work temperature 10℃and in oxalic acid. However, nano pores with diameter of 200 nm were formed when the electrolyte was replaced by phosphoric acid and voltage was turned to 85 V. Furthermore, through SEM images of the surface, cross-linking of the bigger holes was observed. The existence of the pores, on one hand, can act as the nucleus of boiling, on the other hand, can improve heat transfer area. So the smaller bubbles, the higher departure frequency can be seen in the experiment, and as a result, the higher heat transfer coefficient of the nano porous surface was get. Especially, under the high flux, the character is more outstanding. Compared with microgrooves surface, it can be seen the coefficient was lower in the lower heat flux, and with the increasing of the heat flux, it was upside down. So in the paper, a new surface, N-M coupled surface was put forward for further improving the critical heat flux. Experiments show that it has more heat transfer performance than single nano porous or microgrooves surface and the heat transfer coefficient was double that of smooth with the same conditions.