New experimental results on steady-state and transient pool boiling heat transfer

Abstract:
The paper presents a summary of results found in the author's laboratories during recent years. First an experimental technique suitable for precise and systematic measurements of entire boiling curves under steady-state and transient conditions is described. The experimental results for a well wetting fluid (FC72) and a fluid with a larger contact angle (water) show no evidence of a hysteresis in the transition region if the heater surface is clean. For a surface with contamination, however, the boiling curves are not reproducible. The situation is different under transient conditions: heating and cooling transients yield different curves. Measurements with a micro-optical probe give a detailed insight in the behavior of the macrolayer in the different boiling regimes. Temperature signals from microthermocouples very near the heater surface and the optical probe data lead to some conclusions on the physics of boiling in the different boiling regimes. In particular it was found that convective effects in the boundary layer are probably responsible for the deviations between transient and steady-state boiling heat transfer.

Keywords:
Pool Boiling, Transient, Optical Probe, FC-72, Water, Hysteresis, Microthermocouples.

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