Development of thermal-hydraulic analysis code of a helically coiled once-through steam generator based on two-fluid model

Abstract

A thermal-hydraulic analysis model, coupling the flow and heat transfer of the primary and secondary sides, is developed to describe the thermal hydraulic behavior of OTSG (helically coiled Once-Through Steam Generator). This numerical model is developed based on the two-fluid model with distributed parameters method to predict all flow variables at each position along the tube. Correlations, validated a lot, are adopted to consider the effect of helical structure on the flow and heat transfer of both the primary and secondary sides in OTSG. The computational code THOSG (Thermal-Hydraulic analysis code of Once-through Steam Generator) for OTSG is then developed based on the numerical model with the modified SIMPLE algorithm. To benchmark the developed physic model and computer code, steady-state simulation of OTSG of IRIS reactor is conducted. Results are compared with RELAP5 code with respect to the design parameters. Comparisons indicate that the THOSG code can predict the thermal-hydraulic characteristics of OTSG well. In order to investigate the effect of changes in the input conditions on the output of the OTSG, transient analysis has been performed. Simulations of change in feedwater flow rate and temperature are conducted to assess the performance of OTSG. Both steady-state and transient results indicate that the THOSG code can be utilized for the design and performance analysis of OTSG. However, further analysis, coupling with the thermal-hydraulic behavior of the reactor core, is required to comprehensively evaluate the safety and reliability of OTSG design in nuclear power plant.