Two-phase heat transfer correlations in three-dimensional hierarchical tube

Development of novel enhanced surface tubes is an important way to advance two-phase flow heat transfer. To make correlations of two-phase flow heat transfer in enhanced tubes with acceptable prediction has been a challenge for many years. The paper presents a method: two-phase heat transfer correlations in enhanced tubes are directly developed through existing two-phase heat transfer smooth-tube models by introducing several modifying factors and dimensionless numbers. An enhanced heat transfer tube containing staggered arrays of three-dimensional dimples and secondary petal-shaped protrusions (EHT) is one of the most complicated internal surface-tube configurations on the market. Visualizations of flow patterns and measurements of heat transfer coefficients of two-phase flow using refrigerant R410A in smooth and EHT tube are conducted. Detailed visualization experiments during two-phase flows show good agreements between flow regimes and flow-pattern maps in smooth and EHT tube. The equation of continuity is adopted to provide understanding of the mechanism of the agreements. Both theoretical analysis and experimental studies support the method. As a result of using it, new two-phase heat transfer correlations are developed in enhanced tubes as the EHT tube is an example. Flow boiling correlation can predict data points within + 10% to-20% and flow condensation correlation can predict data points within +/- 10% in the EHT tube. (c) 2022 Elsevier Ltd. All rights reserved.

Automated summary

Developing novel enhanced surface tubes is an important approach to improve two-phase flow heat transfer. However, accurately predicting the heat transfer correlations in enhanced tubes has been a challenging task. This paper presents a method to directly develop two-phase heat transfer correlations in enhanced tubes based on existing smooth tube models, by introducing modifying factors and dimensionless numbers. The method is supported by theoretical analysis and experimental studies, and new correlations are successfully developed in an enhanced heat transfer tube as an example.