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The gas-liquid(two-phase) flow pressure drop of liquid nitrogen boiling in the straight section downstream of U-bend is investigated experimentally. The mass flux ranges from 32 to 280 kg/(m2· s). The inlet pressure of U-tube is from 140 to 272 kPa. And the curvature ratio is from 6.67 to 15. The tube wall including the U-bend is heated uniformly and the heat flux ranges from 0 to 22 kW/m2. The tube with higher inlet pressure has higher pressure drop in the downstream section of the bend. The bended degree of the U-bend influences the pressure drop in the downstream straight section of U-bend. A new correlation taking the effect of the secondary flow into account is proposed for the two-phase slip speed ratio. The pressure drop in the straight section downstream of U-bend calculated by the new correlation agrees well with experimental measurements.
The gas-liquid (two-phase) flow pressure drop of liquid nitrogen boiling in a straight section downstream of U-bend is investigated experimentally. The mass pressure ranges from 32 to 280 kg / (m2 · s). The inlet pressure of U -tube is from 140 to 272 kPa. And the curvature ratio is from 6.67 to 15. The tube wall includes the U-bend is heated uniformly and the heat flux ranges from 0 to 22 kW / m2. higher pressure drop in the downstream section of the bend. The bended degree of the U-bend influences the pressure drop in the downstream straight section of the U-bend. A new correlation taking the effect of the secondary flow into account is proposed for the two -phase slip speed ratio. The pressure drop in the straight section downstream of U-bend calculated by the new correlation agrees well with experimental measurements.