Multiobjective Optimal Method for Carbon Dioxide Removal Assembly in Manned Spacecraft

Carbon dioxide removal assembly (CDRA) is an essential subsystem in an air revitalization system (ARS) to control CO2 concentration in a long-term manned spacecraft cabin. At the same time, it is a main power consumption subsystem. CO2 concentration control performance and power consumption are both key factors that need to be considered. To design this subsystem reasonably, some basic processes are analyzed carefully in this paper, such as mass and heat transfer processes in CO2 adsorption beds, power consumption for fan and electric heater, and entropy generation in heat transfer process. The relationship between CDRA and other subsystems are also analyzed carefully. Based on these analyses, a multiobjective optimal method is developed in this paper. Its objective functions are specified as cabin CO2 concentration level, power consumption, and entropy generation. The optimal parameters are air velocity, absorption bed length, adsorption time (half cycle time), and molecular sieve mass loaded in the absorption bed. An improved genetic algorithm, Nondominated Sorting Genetic Algorithm-II (NSGA-II), is adopted to obtain the final optimal solution set. Furthermore, a CDRA for a space station with three astronauts is taken as an example to show the implementation of the proposed method. Optimal results show that the presented optimal method can obtain the design solution set for the CDRA. The optimal parameter combination is recommended as the final optimal design solution by analyzing the global pareto optimal front of the solution set. This multiobjective optimal method can realize an optimization process for a complex system design by taking a comprehensive consideration of various factors and running performances. (C) 2016 American Society of Civil Engineers.