Numerical studies of a helical coil once-through steam generator

A Thermal Hydraulic analysis code for Helical Coil once-through Steam Generator (TH-HCSG) is developed in the present study in order to predict the heat transfer process and thermal hydraulic characteristics in vertical helical coil steam generators. The numerical model is programmed using a one-dimensional four-equation drift-flux model and evaluated according to the data on HCSG published by the International Reactor Innovative and Secure (IRIS). The results achieved under full load conditions are, then, compared with the RELAP5 codes, with the results of this comparison showing that this model is both correct and reliable and can be used to investigate the instantaneous characteristics of helical coil steam generators. This model is also used to evaluate the influence of the main representative HCSG boundary parameters on HCSG operation characteristics. It was subsequently found that, when there was a ±10% step change in the boundary parameters, the length of the single-phase water region in the secondary side of the HCSG changed considerably, so that the steam flow oscillated obviously, lagging the feedwater flow at an early stage and rapidly reaching a steady state as the water capacity of the secondary side of the HCSG was changed.