垂直狭あい環状流路内対向気液二相流の限界熱流束(熱工学,内燃機関,動力など)

概要

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The critical heat flux of the counter-current flow in narrow-annular flow passages (δ=0.5〜10.0 mm) was examined by using R-113 vapor and liquid at 0.1 MP_a for the bottom closed and the open system. When the clearance δ≦2.0 mm, the falling liquid flow rate was restricted by the upward vapor flow in the bottom open system, which was expressed with the Wallis type flooding correlation. The heat flux at the initiation of the temperature excursion (EXC) was well predicted for both the bottom closed and the open system by considering that the EXC occurs when the falling flow rate becomes equal to the evaporation rate under the liquid falling limiting. In the case of δ=5.0 mm, the liquid penetration was also restricted, however it was much lower than the Wallis flooding velocity. It was rather predicted with the flooding by the level swell of the two-phase mixture with the falling film. After the penetration limiting, the falling flow rate became equal to the evaporation rate, and then the EXC was initiated after a further increase in the heat flux. In the case of δ= 10.0 mm, the EXC started like the pool boiling without any penetration limiting. The EXC heat flux correlation for δ=2.0〜10.0 mm was derived by considering that the EXC occurs when the mixture void fraction exceeds a critical value.
2002-11-25