液体窒素蒸発器の不安定流動 : 第1報,並列らせん管の核沸騰域

概要

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Flow instabilities in a nitrogen evaporator are studied experimentally and analytically to investigate the characteristics of the cryogenic flow instabilities and to confirm that the previous stability analysis can be applied to them. The nitrogen evaporator consists of two parallel spiral tubes. Two types of periodical oscillations are observed, one is the oscillation in phase for two tubes and the other is out of phase. The period of he oscillation in phase is independent to the heat flux of the tube and is considered to be caused by boiling at the upstream of heating area. The oscillation out of phase is considered to be a density wave oscillation as its periocd is almost equal to the residence time and occurs in the region where the slope of pressre drop to mass flux is positive. Stability maps are obtained and the stability criteria show that the exit quality is smaller than 0.6. Linear stability analysis for he density wave oscillation using a drift flux model predicts the experimental results fairly well.
1989-08-25