Research On Design Optimization Technology Of Loop Heat Pipe Radiator In Space Reactor

The cold end temperature of Stirling engine in integrated space nuclear reactor is low(about 450K),so high-performance radiator design is required to meet the heat emission requirements.The gas-liquid pipelines of the loop heat pipe are separated from each other,enabling efficient heat transfer over long distances,making it an ideal choice for the design of space radiator.Currently,there is limited research on design evaluation models for space reactor loop heat pipe radiators,and performance constrained optimization design methods still need to be improved,making it impossible to provide safe,lightweight,and efficient space reactor radiator designs.In this paper,based on the radiator system with loop heat pipe coupled with radiant fins,an overall analysis model is established for design evaluation.On this basis,the operation characteristics of the radiator system are analyzed.Combined with the polynomial response surface surrogate model and genetic algorithm,the design optimization method of space reactor loop heat pipe radiator is realized with the design performance evaluation as the constraint.Firstly,starting from the overall design of the space reactor loop heat pipe radiator,research is conducted on the flow and heat transfer characteristics of the working fluid inside the loop heat pipe and the heat transfer characteristics of the radiation heat dissipation wing.Considering the coupled heat transfer process between the loop heat pipe and the radiation heat dissipation wing,a numerical model of each component of the loop heat pipe radiator is established based on the heat balance idea,and a heat balance calculation method based on energy coupling iteration solution is proposed.Furthermore,the finite difference method and the finite volume method are used to numerically difference the control equations of the fintype and the panel-type radiator,and the Newton’s method and the two-way alternating implicit line iterative method are used to solve the equations.By comparing experimental data with different heat loads,the effectiveness of the loop heat pipe design evaluation model was verified,indicating that the model can accurately reflect the operational characteristics of the loop heat pipe radiator system and provide reference for the design evaluation of space loop heat pipe radiator.Taking the heat dissipation system of the integrated space nuclear reactor with Stirling machine as the research object,the performance of the loop heat pipe radiator under different thermal design parameters was studied using the developed performance evaluation program.The results showed that the heat dissipation capacity of the radiator under different power was limited by the evaporation temperature,and the rise of the evaporation temperature caused the nonlinear growth of the system operating temperature.The operating limit was determined by the difference between the evaporation temperature and the heat sink temperature.The performance comparison results of different types of radiant fins show that the panel-type is better than the fin-type in terms of temperature uniformity,and the uneven temperature distribution characteristics of panel-type radiator under different cooling areas are further analyzed.Finally,the optimization objectives and constraints for the design of space reactor loop heat pipes are studied to solve the problem of minimizing the quality of heat sinks with performance evaluation constraints.In the optimization process,a polynomial response surface surrogate model was constructed to replace the developed design evaluation program,which solved the problem of long calculation time for multiple calls of the program,and formed an optimization design method combining the surrogate model and genetic algorithm.The mass of the optimized overall panel-type radiator was reduced by 0.89 kg(about 5.08%),and the optimized structural design value could still meet the index requirements of the system operating temperature.