Experimental study for pressure drop and flow instability of two-phase flow in the PCHE-type steam generator for SMRs

Experiments have been carried out to apply PCHE as a steam generator in Small Modular Reactors. KAIST designed the straight-type PCHE for the application of the steam generator, and constructed a high-pressure test facility. We investigated the effects of system pressure, inlet water temperature and heat input on the thermal-hydraulic characteristics of PCHE. For each case, we varied the water flow rate over a wide range in order to identify the pressure drop characteristic curve of PCHE. In order to predict the pressure drop caused by PCHE, we compared and analyzed various existing correlations. In addition on the steady-state characteristic curve, the occurrence of instability at each point and the criteria of DWO and Ledinegg instability were experimentally determined. The super-heated steam test at low flow rate resulted in severe DWO with high fluctuation. Since the stable operation in the super-heated region is crucial for the PCHE-type steam generator, we conducted a stabilization experiment using an inlet throttling valve to verify such possibility.