HEAT TRANSFER TO MULTIPHASE FLOW IN COILED PIPES
Data on heat transfer coefficients, quality, void fractions and frictional multipliers for water boiling in helical coils of curvature ratios 0.037 and 0.056 are presented and analysed in the light of the various models available in literature for single and two phase flows. A generalised design correlation which can predict the circumferential and boiling heat transfer coefficients at high and low pressure helical steam generators is obtained.
The mechanisms of heat transfer and flow patterns of two phase flow prevailing in different sections of the helical steam generator are explained in the light of the sectional heat transfer data and compared with the various reported data. The local void fractions and quality of steam are observed to be much higher than those in vertical steam generators, which indicate that helical coils are more advantageous to be used as efficient steam generators.