The performance of an actual free piston free displacer (FPFD) Stirling miniature cryocooler has been simulated based on the parameters affecting the performance of the cryocooler. The processes of compression and expansion in the cryocooler have been assumed to be polytropic with variable ratio of specific heats for the working fluid, i.e., helium. The effect of design parameters like piston spring stiffness, displacer spring stiffness, mass of the piston, displacer mass and frequency of operation on the cooling power of the cryocooler has been calculated. The parameters thus obtained with polytropic processes have been compared with the parameters obtained by assuming the compression and expansion processes to be isothermal. The amplitude of the piston and the displacer is not constant in the case of free piston free displacer cryocooler with linear motors. Linear motor drives have been used for eliminating the side forces on the cylinder walls and wear and tear of the reciprocating parts of the cryocoolers giving them a very long life. A computer program named CRYOJIN which was developed for the isothermal case has been modified for analyzing the real-time performance of the cryocooler for polytropic processes. The physical dimensions of Philips 1 W FPFD cryocooler have been taken for study and comparison.

中文翻译：

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考虑多变过程的FPFD微型斯特林低温冷却器性能参数预测

基于影响低温冷却器性能的参数，对实际的自由活塞自由置换器 (FPFD) 斯特林微型低温冷却器的性能进行了模拟。已假设低温冷却器中的压缩和膨胀过程是多方的，工作流体（即氦）的比热比可变。计算了活塞弹簧刚度、置换器弹簧刚度、活塞质量、置换器质量和运行频率等设计参数对低温冷却器冷却功率的影响。通过多变过程获得的参数与通过假设压缩和膨胀过程为等温获得的参数进行了比较。在带有线性电机的自由活塞自由置换器低温冷却器的情况下，活塞和置换器的振幅不是恒定的。直线电机驱动器已被用于消除气缸壁上的侧向力以及冷却器往复部件的磨损和撕裂，从而使它们具有很长的使用寿命。为等温情况开发的名为 CRYOJIN 的计算机程序已被修改，用于分析多变过程的低温冷却器的实时性能。飞利浦 1 W FPFD 低温冷却器的物理尺寸已用于研究和比较。为等温情况开发的名为 CRYOJIN 的计算机程序已被修改，用于分析多变过程的低温冷却器的实时性能。飞利浦 1 W FPFD 低温冷却器的物理尺寸已用于研究和比较。为等温情况开发的名为 CRYOJIN 的计算机程序已被修改，用于分析多变过程的低温冷却器的实时性能。飞利浦 1 W FPFD 低温冷却器的物理尺寸已用于研究和比较。