Study on the Performance of Supercritical Nitrogen Brayton Cycle Power Generation Using Liquefied Natural Gas as the Cooling Source

In order to provide a new idea for liquefied natural gas (LNG) cold energy generation with the external heat source temperature as the ambient temperature, a Brayton cycle power generation system with recompression using seawater as the heat source, LNG as the cold source, and supercritical nitrogen as the circulating medium is proposed, a thermodynamic model is constructed. The results show that when the pressure ratio is 2.5, the C1 inlet pressure is 4965kPa and the shunt coefficient is 0.267, the LNG unit output work, thermal efficiency and LNG cold energy utilization rate reach the maximum under this working condition, which are 215.64kJ/kg, 26.23% and 24.1 % respectively. The heat transfer performance of the four heat exchangers in the system is good, and the exergy efficiencies are 87.3%, 94.4%, 89.6%, and 21.8%, respectively. Comparing this cycle with the Organic Rankine cycle + LNG direct expansion method using R290 as the working fluid, the thermal efficiency is increased by 16% and the exergy efficiency is increased by 11.2%.