Heat transfer of air/water two-phase flow in helicoidal pipes is experimentally investigated in this study. Three test sections were tested in axially horizontal, vertical, and inclined orientations. It has been found that the ratio of the average heat transfer coefficient to that of the water flow is affected by the water flow rate along with the Lockhart–Martinelli parameter. For a fixed water flow rate, there is a maximum heat transfer coefficient as the air fow rate increases. The results indicate that tube diameter has a significant effect on the average heat transfer coefficient ratio. For large-tube-diameter coils, average heat transfer results vary for different orientations. For small-tube-diameter coils, orientation has an insignificant effect on the average heat transfer coefficient. Based on the experimental data, a set of correlations is proposed for the average heat transfer coefficient ratio versus the liquid superficial Reynolds number and Lockhart–Martinelli parameter.

Issue Section:
Boiling and Two-Phase Heat Transfer
Keywords:
Forced Convection, Heat Exchangers, Measurement Techniques
Topics:
Heat transfer, Pipes, Two-phase flow, Water, Heat transfer coefficients, Flow (Dynamics), Forced convection, Heat exchangers, Reynolds number
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