Prediction of onset of nucleate boiling, net vapour generation and subcooled CHF in coiled tubes

The heat transfer characteristics of a coiled steam generating tube are very different from those of a straight tube. For example, the critical heat flux (CHF) in coiled tubes is less than that in straight tubes for subcooled boiling and significantly higher at higher qualities. In this paper, predictive methods are developed for the determination of the point of onset of nucleate boiling, the point of net vapour generation and the critical heat flux condition in curved ducts. The methods are based on the assumption that these phenomena are governed by the local hydro- and thermodynamic conditions which can be predicted using computational fluid dynamics techniques. Good agreement has been obtained with available experimental data.