Use of the microscopic parabolic heat conduction model in place of the macroscopic model validation criterion under harmonic boundary heating

Parabolic heat conduction models are considered. The validity of using a microscopic under harmonic fluctuating boundary heating source is investigated. It is found that using the microscopic parabolic heat conduction model is essential when . The phase-shift between the electron gas and solid lattice temperatures is found to be . This phase-shift reaches a fixed value of 1.5708 rad at very large values of . It is found that using the microscopic parabolic heat conduction model is essential when rad/s for most metallic layers regardless of their thickness.     

Nucleation site interaction in pool boiling on the artificial surface

The present work aims at studying the physical mechanisms of nucleation site interaction in pool boiling. A series of experiments have been carried out to investigate the average bubble departure frequency of two artificial cavities on the thin silicon surface for different dimensionless cavity spacing , that is the ratio of the cavity spacing to the average bubble departure diameter. Based on the comprehensive observation and analysis, three significant effect factors of nucleation site interaction are found out: hydrodynamic interaction between bubbles; thermal interaction between nucleation sites; horizontal and declining bubble coalescences. The intensity, competition and dominance relations of these three factors determine four different interaction regions: ‘I’ region , ‘H’ region , ‘H+T’ region and ‘H+T+C’ region . In the ‘I’ region, the bubble departure frequency is similar to that in the single cavity condition as a result of the negligible effect of all the three factors. For the ‘H’ region, the stronger influence of factor results in a higher bubble departure frequency. Within the ‘H+T’ region, the co-existence and competition relation occurs between factors and . The dominance of factor causes the lower bubble departure frequency. As for the ‘H+T+C’ region, although all the three factors are strong and compete simultaneously, the promotive effect becomes dominant finally and the bubble departure frequency increases again. Through the present study, some essential aspects of the nucleation site interaction in pool boiling have been revealed, which is significant for better understanding the boiling mechanisms.