Numerical analysis of coupled flow and heat transfer in primary and secondary sides of double-side heating once-through steam generator with helical tubes

The inner tubes of double-side heating once-through steam generator (OTSG) with helical tubes are spiral channels, and the secondary fluid is heated on both sides, effectively improving the heat transfer efficiency. The spiral structure makes its flow heat transfer characteristics different from straight tube type OTSG. This article establishes a numerical model of Euler two-phase flow in double-side heating OTSG with helical tubes to analyze its velocity distribution, volume fraction distribution, and temperature distribution. The results show that the fluid spirally rises in the secondary flow passage, the velocity of two phases increases rapidly after vaporization, the slip ratio is greater than 1, the steam volume fraction on the wide side is higher than that on the narrow side, and the steam volume fraction presents a spiral distribution on the wall. The non-uniform circumferential steam volume fraction leads to the wall dryout first at the wide edge, and the wall temperature also presents a spiral distribution. The dryout position temperature rises 40.13 K along the Z direction, and the temperature gradient is 5.26 K/mm. The circumferential temperature rises 44.46 K, and the temperature gradient is 15.11 K/mm.