Effect of the boundary conditions around the heating surface on the formation of MEB

This study conducts experiments for two cases to demonstrate the effects of the boundary condition around the heating surface on microbubble emission boiling. For one case, the heating surface flushes with the tank bottom and for the other one, the heating surface is about 0.5 mm lower than the tank bottom. Comparison is made for the bubbling performance and flowing velocity under the above two conditions. Experimental results showed that microbubble emission boiling (MEM) occurred vigorously with 50 K subcooling in the first case, while in the second case, the MEB phenomenon did not occur. The data analysis shows that Marangoni convection near the bubble is weakened and the condensation at the vapor-liquid interface is reduced remarkably. Both of these effects cause the bubbles to form and grow up stably on the heating surface without MEB occurring. Therefore, the conclusion is made that Marangoni convection and the condensation at the interface are possibly the reason for microbubble emission boiling. ©, 2015, Editorial Board of Journal of HEU. All right reserved.