Experimental and LBM simulation study on the effect of bubble merging on saturated pool boiling in pure water

The foaming characteristic of surfactant solution is rarely discussed in surfactant enhancing pool boiling heat transfer and the critical heat flux (CHF). In the present work, saturated pool boiling experiment using transparent heating plate of indium tin oxide (ITO) coating and lattice Boltzmann method (LBM) simulation are conducted to get further insights into the effect of bubble merging on the wettability characteristics and CHF. With a high-speed camera, the gas-liquid phase and nucleate site distribution at the heating surface are recorded. The improved Shan-Chen model is applied in LBM simulation to investigate the interaction between nucleate sites. The experimental and simulation results show that vapor film appears at CHF. The vapor film inhibits nucleate sites to be effective and other new bubbles to emerge. Bubble merging decreases the contact line of gas-liquid-solid interface. The irreversible dry spot appears in the center of large bubbles due to CHF. It implies that preventing bubble merging is another factor of surfactant enhancing pool boiling heat transfer and CHF.