Experimental investigation of the thermal-hydraulic characteristics of a printed circuit heat exchanger in the helium-xenon Brayton cycle

Micro nuclear reactors have a wide range of applications. The printed circuit heat exchanger is considered well-suited as a heat exchanger type for reheaters and pre-coolers in the Brayton cycle of such micro nuclear reactors, due to its high compactness, high heat transfer efficiency, and ability to operate at high temperatures and pressures. This work focuses particularly on the experimental analysis of a heat exchanger for a micro-transportable gas-cooled thermal reactor. The research investigated the thermal-hydraulic performance of a helium-xenon (He-Xe) gas mixture with an 8.69 % helium mass fraction in a printed circuit heat exchanger (PCHE). Various experimental parameters, such as inlet temperatures, pressures, and mass flow rates on the hot side, are studied within the range of 400–600 K, 1–2 MPa, and 5–45 kg/h, respectively. The work evaluated the influence of mass flow rate, inlet temperature, and pressure on the thermal-hydraulic performance of the PCHE with the He-Xe gas mixture. Results demonstrated that increased mass flow rates and inlet temperatures significantly enhance the heat transfer capabilities on the He-Xe side. Besides, based on the experimental data, a method integrating genetic algorithms with the median wall temperature method is proposed to separate the thermal resistances on the hot and cold sides of the PCHE. A Nusselt number correlation is established based on the Reynolds number and the Prandtl number. Additionally, a Fanning friction factor correlation is proposed.