Performance Analysis of Closed Loop in CCMHD Single Power Generation System

Abstract

Results of numerical study on performance of closed loop in the CCMHD single power generation system are presented. The small closed loop with thermal input of 2.3MW was designed. The fluid-dynamical and thermal performance of the closed loop was calculated for the first time by one-dimensional numerical simulation. The result indicates that pressure loss and heat loss are large in the designed small closed loop. The large pressure loss was due to the wall friction or the pebble bed and it occurred at the supersonic nozzle, the MHD channel and the regenerative heat exchanger used for argon cooling. The enthalpy extraction remained low (=17.6%) owing to the large pressure loss and as a result, the thermal efficiency of the closed loop remained only 21.6%. The enthalpy extraction and the thermal efficiency became the maximum at the optimal inlet total pressure of 0.60MPa. At lower inlettotal pressure than the optimal one, the electrical conductivity, the flow velocity and the electrical efficiency became higher. However, the total pressure ratio (=exit/inlet) in the MHD channel became larger particularly at low inlet total pressure because of the increase in the pressure loss due to pebble bed and wall friction. These led to the existence of the optimal inlet total pressure.