Performance characterization of an axial closed Brayton cycle compressor operating with helium-nitrogen gas mixture

This study evaluates the possible use of a mixture of helium-nitrogen as a working medium in axial compressors employed in terrestrial nuclear facilities. As helium in its pure form is considered to be an excellent coolant owing to its superior transport capabilities, nonetheless it poses challenges in compression. With this, the high temperature gas cooled reactor (HTGR) energy systems result in increased size, greater mass, elevated costs, and dynamic issues in turbomachinery. This research provides the detailed investigation of thermophysical and transport properties of helium and nitrogen binary gas mixture at specified conditions which demonstrate that the heat transfer coefficient enhances by 4.2 % when its molar weight equals 13 g/mole. Therefore, a new helium-nitrogen compressor is subsequently designed. The performance evaluation is done, and the results indicate that just 22.86 % of the stages in the helium compressor are necessary to attain the requisite pressure in a helium-nitrogen compressor. The HTGR operating on the closed Brayton cycle (CBC) has decreased its compressor stages from 16 to 4 only. As a result, helium-nitrogen binary gas mixture is more appropriate for use in the turbocompressors of HTGR power plants than pure helium.