EXPERIMENTAL INVESTIGATION OF FLOW BOILING HEAT TRANSFER IN VERTICAL NARROW ANNULAR CHANNELS

摘要

The intention of this paper is to survey the features of frictional pressure drop and heat transfer in vertical narrow annular channels. In the first half of this study, different factors which have influence on frictional pressure drop in narrow annular channels are analyzed based on experimental data. The two-phase frictional multiplier Φ_L is expressed using Lockhart-Martinelli type correlation with modification of Chisholm's parameter C in which the effects of the mass flux, the gap size and system pressure are considered. The correlation with the modified C successfully predict the two-phase frictional multiplier Φ_L with the deviation of +-10%.In the last half, the main factors concerning the characteristics of flow boiling heat transfer in narrow annular channels are figured out. The desirable correlation of dimensionless numbers which used to calculate heat transfer coefficient of flow boiling in narrow annular channels in similar conditions is given here. The calculation results of this correlation are compared with the experimental data and agree well with it while the deviation is less than +-15%.