Dynamic Analysis of Bubble Attachment and Sweeping on Microwire in Subcooled Nucleate Pool Boiling

With the development of industrial technology, heat transfer at the microscale has attracted more and more attention. In this work, 200 µm platinum wire and 150 µm nickel-chromium wire were used as experimental objects, which the power was provided by DC power with the range of 15.6 W to 56.2 W. Distilled water was used as the experimental liquid. Various bubbles on the micro wire were observed and the heat mechanism was analyzed. A variety of bubble attachment phenomena were captured on the 200 µm platinum wire, including the adhesion during bubble detachment, the rotation of small attached bubbles on the surface of large bubble, multiple bubbles circling at the top of the same bubble, and different attached bubble departure phenomena. Marangoni force in the vertical direction triggered the formation of bubble attachment. In addition, the effects of surface tension, adhesion force and buoyancy force on the circling of the bubble were also considered. The analysis of the bubble sweeping on the 150 µm nickel-chromium wire was analyzed. The results showed that the static bubble would interact with the sweeping bubbles on the other side, thereby changing the heat transfer mechanism, which was not discussed in detail before. The bubble jet flow generated by thermocapillary convection on the vertical direction of the bubble surface was the main influencing factor, which would change the microlayer encountered in front of the bubble. The effects of bubble diameter and liquid subcooling on the sweeping velocity were also studied. The results showed that the larger the bubble diameter was, the lower the sweeping velocity would be achieved while the liquid subcooling temperature had less impact on the velocity of sweeping bubble.