Incipient boiling superheats and critical heat fluxes due to increasing heat inputs in subcooled He I at various pressures
- Kyoto Univ. (Japan)
Dynamic boiling heat transfer processes on a 0.2 mm diam. horizontal wire due to exponentially increasing heat inputs, Q{sub 0}e{sup t/{tau}}, with the periods, {tau}, from 0.2 ms to 25 s in subcooled He I at pressures of atmospheric, 142 kPa and 196 kPa were investigated to clarify the effect of liquid subcooling on the incipient boiling superheat and critical heat flux. The steady-state critical heat fluxes for the subcoolings ranging from 0 K to around 2.5 K at pressures of atmospheric, 142 kPa and 196 kPa were obtained by the heat input with a period of around 20 s; almost data obtained did not agree with the values derived from the existing correlations based on hydrodynamic instability model. An empirical correlation was given. The liquid temperature close to the test wire surface, T{sub lw}, is given as the difference between the wire surface temperature and the temperature corresponding to the Kapitza resistance: the Kapitza conductance was estimated based on that experimentally obtained for the same test wire in He II. It was confirmed that the boiling incipience caused by a heat input over the range from quasi-steadily increasing one to rapidly increasing one occurs due to the heterogeneous spontaneous nucleation, HSN, at the T{sub lw} lower than the corresponding theoretical value of homogeneous spontaneous nucleation temperature. The correlations for critical heat flux at which the transition to film boiling occurs due to the HSN in originally flooded cavities on the wire surface were given for the wide ranges of exponential periods, T{sub lw} pressures and subcoolings.
- OSTI ID:
- 416640
- Report Number(s):
- CONF-950722--
- Country of Publication:
- United States
- Language:
- English
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