BOILING FEATURES ON ARTIFICIAL SURFACES

摘要

The artificial surfaces with a single, twin and multiple cavities are employed to study features of nucleate pool boiling such as bubble behaviors, fluctuation of heated surface temperature, heat transfer and especially nucleate site interaction. Four sets of experiment are carried out to investigate the influences of cavity shape, cavity size, cavity spacing, thermal capacity and thickness of the heated wall on boiling phenomena. Additional boiling test for the surface with multiple cavities are also performed. Experimental results reveal that bubbling from the cylindrical as well as reentrant cavity is generally stable. The influence of cavity diameter on the bubble behaviors and the surface temperature fluctuation seems to be very weak while the effect of cavity depth is significant. From the comprehensive observation and analysis using twin cavities, it is found that nucleation site interaction differs markedly depending on cavity spacing: three significant effect factors (thermal, hydrodynamic and bubble-coalescence factors) control the nucleation site interaction, and the interaction regime can be classified into four due to the competition and the dominance among the three factors. The result of multi-cavity surface suggests that the optimum cavity spacing exists for-the best heat transfer performance.