用于冷中子源系统的氦制冷循环方案分析

为向冷中子源装置氢系统提供17．5K的低温冷源，设计了逆布雷顿循环的液氮预冷模式和4种膨胀机预冷模式，并对这5种循环模式进行热力分析和[火用]分析，获得了各循环模式下的主要热力参数并分析比较了各自的热力性质．结果表明：带液氮预冷和前置式并联膨胀机预冷2种模式的热力性能最好，[火用]效率最高；对于膨胀机预冷循环，并联模式优于串联模式，前置式优于后置式．循环系统[火用]损失部位主要在压缩机、膨胀机和换热器，减小这3部分[火用]损失的途径有以下方面：改善循环，减小系统氦的质量流量；提高压缩机的等温效率、膨胀机的等熵效率；改善换热器的内部温度、温差、压力分布及物流分配．本研究为中国先进研究堆冷中子源氦制冷系统的设计提供了数值基础。

Analysis of Helium Cryogenic Cycle for the Cooling of Cold Neutron Source

A reverse Brayton cycle with advance refrigeration of liquid nitrogen and four cycles with advance expander refrigeration were designed to provide 17.5 K cold source for H_2 system of cold neutron source(CNS) project.Based on thermodynamic and exergetic computation for the different cycle modes,thermodynamic parameters,exergy loss,exergy efficiency and cycle capability were obtained and analysed respectively.The results show that the capabilities and exergy efficiencies of the cycles with liquid nitrogen and with prepositive parallel connected expander are greater than those of others;for the cycle modes with advance expander refrigeration,parallel connection mode is superior to series connection mode,and prepositive mode is superior to postpositive mode.The main exergy loss of cycle occurs in the compressor,the expander and the exchanger,so there are three ways to improve exergy efficiency of cycle:(1) reducing the mass rate of helium by improving cycle;(2) improving isoenthopic efficiency of the expander and isothermal efficiency of the compressor;(3) improving distribution of temperature,pressure,temperature difference and refrigerant in the exchanger.These results provide numerical basis of the design of helium cryogenic cooling system of CNS for China advanced research reactor(CARR).