Experimental Investigation on the Effect of Volume Flow Rates and EEV Openings on the Regeneration Process of a Solution Regenerator Unit Using Freezing Concentration

This experimental study investigates the impacts of volume flow rates (4–7 m³/h) and electronic expansion valve (EEV) openings (50–100%) on the regeneration process of a 6% dilute sodium formate solution in a solution regenerator unit using freezing concentration. Key findings reveal that latent heat exchange dominates the heat transfer process, with a stable latent heat ratio of approximately 80%, while sensible heat exchange increases slightly (by 6%) only at 50% EEV opening due to reduced refrigerant flow. Volume flow rates affect ice growth in stages: high flow rates (6–7 m³/h) accelerate initial ice formation, but low flow rates (4–5 m³/h) promote faster late-stage growth, with a 0.001 mm/s higher thickness growth rate by the experiment’s end. EEV openings significantly influence ice layer uniformity; lower openings (50%) increase ice layer slope (up to 6.57%), enhancing separation efficiency via gravity-driven melting, with the maximum separation ratio reaching 0.75. These results provide critical insights for optimizing system performance in dilute solution regeneration.