Heat Transfer During Subcooled Boiling in Tubes (A Review)

Abstract

This article provides a review of the correlations and models for determining the intensity of heat transfer during subcooled boiling in pipes. As a rule, correlations are based on dimensionless similarity numbers, while heat exchange models with subcooled boiling use the principle of superposition of the components of heat transfer during forced convection and developed nucleate boiling. Various authors propose different approaches to the implementation of the principle of superposition. This article presents an analysis of the advantages and disadvantages of the correlations and models. These advantages and disadvantages were determined both by analyzing the physical laws of subcooled boiling and by comparing the results that were obtained by the authors of this article by means of various models of subcooled boiling with the experimental data obtained during the study of heat transfer during the subcooled boiling of ammonia in a cylindrical heated tube. The tube diameter d was 6.9 mm, length L was 150 mm, inlet subcooling was 5 K, saturation temperature range was 61...65 °C, mass flow rate was 7.5 g/s, and heat flux density range was 5...18 W/cm2. As a result of the review and comparison with the experimental data, it was determined that the existing correlations and models describe the subcooled boiling of ammonia with insufficient accuracy, especially in the area of the combined effect of forced convection and nucleate boiling. Therefore, it is necessary either to refine the existing correlations and models, or develop new models for a more precise description of the subcooled boiling heat transfer of ammonia in heated tubes in the parameter range specified above.

Keywords

• subcooled boiling
• nucleate boiling
• forced convection
• models of subcooled boiling
• principle of superposition
• ammonia