Study in steam-water two-phase flow heat transfer at high mass velocity of flow in vertical helical coiled tube

Experiments were conducted to further understand the heat transfer in two-phase flow in vertical helically-coiled tubes. The experiments covered a wide range of pressure 8.0-15.0 MPa, mass flow rate 2500-4000 kg/(m²s), heat flux 200-800 kW/m². The experimental segment is 2.335 meter long and made by φ14 × 2 mm steel tube. The diameter ratio D/d is 30.1. Through analyzing the influence of heat flux, mass velocity on average heat transfer coefficient, we acknowledge the activities of nucleate boiling and forced convection two mechanism on steam-water two-phase heat transfer in helical coils tubes at high mass flow rate. The average and local heat transfer coefficient correlations were obtained. At high mass flow rate conditions, the effect of heat transfer in the steam-water two-phase flow in helically coils is inclined to that of straight tube at same conditions and the results are compared.