Steady and Transient CHF in Subcooled Pool Boiling of Water under Sub-atmospheric Pressures

抄録

The steady and transient pool boiling experiments were performed on a horizontal cylinder in a pool of ion-exchange-distilled water at pressures of 20 kPa to 101.6 kPa. The steady state Critical Heat Flux (CHF) data under one atmosphere and sub-atmospheric pressures for the subcoolings ranging from zero up to 40 K were compared with conventional correlations such as Kutateladze and Zuber’s ones both of which are based on hydrodynamic instability. The results showed that CHF data for one atmosphere matched conventional correlations but CHF data for sub-atmospheric pressures showed higher values. The transient CHF due to exponentially increasing heat inputs, Q₀exp(t/τ), with the exponential periods (τ) ranging from 20 s down to 10 ms were measured at one atmosphere and sub-atmospheric pressures for the subcoolings ranging from zero up to 40 K. It was observed that the transient pool boiling CHF values first increased with a decrease in period up to a maximum CHF, then decreased down to a minimum one and again increased with a decrease in period. The transient CHF values under sub-atmospheric pressures could be divided into two groups based on periods of exponential heat generation.