Experimental Performance Evaluation of a Multi-stream Heat Exchanger for Integration of High-Temperature Steam Electrolysis with Nuclear Reactor Systems

Printed-circuit type multi-stream heat exchanger was designed and fabricated to produce high-temperature steam and air simultaneously from high-temperature helium heated using the helium loop, which is simulating VHTR (Very-High Temperature gas-cooled Reactor). This study describes the design methodology and the heat transfer performance evaluation results of the multi-stream heat exchanger for stable supply of high temperature steam and air to a 30 kWe SOEC (solid-oxide electrolyzer cell) system to produce hydrogen with high-temperature nuclear reactor systems. In order to control the steam supply above 700 ℃, the steam supply control methodology was established with a pressure control valve between the multi-stream heat exchanger and a steam generator. In this study, 20 kg/hr of steam over 800 ℃ and 110 SLPM of air over 750 ℃ were supplied stably with the multi-stream heat exchanger using helium loop. The heat transfer performance evaluation for steam is 1.1% below the design condition, which meets the design value within the error range. However, for air, the heat transfer was found to be 50.6% less than the design value due to a decrease in flow rate and reduced heat transfer performance caused by the formation of a deposition layer along the flow path. This high-temperature steam and air supply system will be connected with a high-temperature steam electrolysis system to perform the integral hydrogen production test using helium loop.