Experimental investigation of thermal–hydraulic parameters on the performance of a once-through steam generator (OTSG)

Abstract

The Once-Through Steam Generator (OTSG) is a critical component in multi-purpose modular small reactor power systems. In this study, a dual-loop experimental system was established to investigate the thermal–hydraulic characteristics of OTSGs, with a focus on analyzing the effects of key parameters—primary-side average temperature, load, steam pressure, and feedwater temperature—on the steady-state thermal–hydraulic behavior. Experimental results reveal that deviations in thermal parameters significantly influence the outlet steam temperature (superheat), heat transfer power, and secondary-side pressure drop. Among these parameters, the primary-side average temperature exhibits the most pronounced impact on the outlet steam temperature, followed by steam pressure, load, and feedwater temperature. Specifically, the superheat decreases as the primary-side average temperature decreases, with a more significant reduction observed near the saturation temperature. At low loads (20%–60% of full power, FP), the superheat decreases linearly with steam pressure, whereas at high loads (60%–120% FP), the rate of decrease in steam superheat intensifies with increasing steam pressure. The superheat initially increases slowly with load, reaches a maximum, and then decreases rapidly. The maximum superheat decreases with increasing steam pressure, and the load required to achieve the maximum superheat point decreases accordingly at higher pressures. Additionally, as the feedwater temperature increases, the superheat decreases, albeit at a relatively modest rate. These findings enhance the understanding of OTSG thermal–hydraulic behavior and provide valuable insights for optimizing their design and operational performance.