Marangoni effect on microbubbles emission boiling generation during pool boiling of self-rewetting fluid

In order to clarify the Marangoni effect on microbubbles emission boiling (MEB) generation during the pool boiling of self-rewetting fluid (SRWF), a plenty of boiling experiments were carried out, which used heptanol aqueous solution as SRWF. A horizontal platinum wire was used as heated surface during the pool boiling experiments. Additionally, a high speed video camera was used to record the nucleation boiling process. The experimental results show that, the MEB phenomenon only appeared in the heptanol aqueous solution case. Due to the occurrence of MEB phenomenon, the 0.1 wt% heptanol aqueous solution shows much better critical heat flux (CHF) and heat transfer coefficient. Furthermore, the Marangoni effect was quantitatively analyzed combining dimensionless parameters of the thermal Marangoni number (Ma_T) and solutal Marangoni number (Ma_S). The results show that, the Marangoni convection along the vapor/liquid interface is the key factor to induce the MEB. Since the Marangoni number reaches about 3 × 10⁶ when the MEB appeared, the Marangoni number of 3 × 10⁶ should be the critical magnitude that induces the MEB phenomenon for 0.1 wt% heptanol aqueous solution in this case.