The objective of this study is to verify the feasibility and applicability of the PCHE-type steam generator. In order to carry out this study, we constructed a new experimental facility in KAIST and conducted boiling experiments under high pressure conditions. We have experimentally confirmed what happens in the heat exchanger consisting of thousands of mini-channels. The pressure drop characteristic curves of the flow rates were obtained under different conditions of heater output, system pressure, inlet temperature, and inlet pressure drop, and the occurrence of flow instability was compared together. A physical model that well predicts the pressure drop characteristics inside the heat exchanger was evaluated and selected. Through the experiments to verify stable superheated steam generation of PCHE, its possibility to be used as a steam generator was confirmed. By analyzing the flow instability with dimensionless parameters, the boundary of density wave oscillation was predicted and the inlet pressure drop value which enables stable flow was obtained. Previous models were first compared with the experimental results, and then the Guido model was modified and developed to apply the steam generator that generates high-quality steam. The KAIST model offers a wider operating margin than the Guido model.