Nonuniform Heat Transfer in Horizontal Helical Coils Tube Steam Generators

The present experiment is conducted to study the nonuniform heat transfer of single-phase water turbulent flow and two-phase steam-water flow in horizontal helical coils tubes. The inner and the outer diameter of the tube are 11mm and 15mm respectively, and the ratio of the diameter of the coil to that of the tube is 23.27. The experimental pressure ranges from 0.5 to 3.0MPa, mass flowrate from 200 to 2500 kg/m2 s, heat flux from 230 to 500kW/m2, and the maximum exit steam quality 0.86. Along both the tube axial direction and the periphery on the cross-section, the local heat transfer coefficients are not evenly distributed. The secondary flow has less contribution to the enhancement heat transfer of the coil with increasing Reynolds number to a high level. Taking the average coefficient at outlet section as that of the coil is not reasonable.