Experimental study and dynamic response analysis of thermal-hydraulic characteristics in zigzag PCHE at ultra-low temperature

The printed circuit heat exchanger (PCHE) demonstrates excellent thermal-hydraulic performance and compact structure, making it a promising candidate for use as a vaporizer in the Fuel Gas Supply System (FGSS) of Liquefied Natural Gas (LNG) ships. To investigate the thermal-hydraulic performance of a PCHE functioning as a vaporizer under ultra-low temperature conditions and to assess the impact of fluid freezing. This study conducted experimental tests on the performance of a zigzag PCHE, utilizing Liquid Nitrogen (LN) and Ethylene Glycol (EG) as the cold and hot working fluids, respectively. Firstly, the local temperature distribution within PCHE was analyzed. Secondly, the effect of varying inlet mass flow rates on the flow heat transfer performance was investigated. The thermal-hydraulic phenomena and vaporization effects under both parallel and counter flow conditions were subsequently compared. Finally, a dynamic analysis of the risk of freezing under counter flow conditions was performed. The results indicate that the internal temperature distribution of the PCHE tends to favor the hot side. Furthermore, the heat transfer performance of the PCHE improves with increasing mass flow rates, with a more pronounced enhancement observed for LN compared to EG. Under counter flow conditions, the heat transfer rate and vaporization effect increased by 6.5% and 6.1%, respectively, compared to parallel flow. When the local fluid within the PCHE approaches freezing conditions, a significant deterioration in heat transfer performance occurs. To ensure optimal heat transfer efficiency and effective vaporization, it is critical that the vaporization rate remains above 78%. This study provides a valuable reference for the structural optimization and anti-freezing measures of PCHEs when used as ultra-low temperature vaporizers, laying the foundation for their application in the FGSS field.