本研究以開發自由活塞式冷凍機為主要目標，有別於傳統機構型史特靈冷凍機，自由活塞式冷凍機，使用平面彈簧做為儲能元件，此結構無法以連桿機構限制移氣器衝程與頻率，亦無法固定活塞與移氣器間之相位差，因此難以事先掌握其動態表現，故藉由理論模型之動力與熱力模式，分析求得工作區域與元件之位移、體積、質量、壓力與溫度，並以該次所求得之數值作為下一步之計算基準，以預測冷凍機之動態變化。藉由考慮系統之能量損失對製冷溫度的影響可得瞬時溫度與能量改變量。
研究發展之模型用以討論於不同操作參數與幾何參數下，系統穩定運轉之性能表現，以建立完整的自由活塞式史特靈冷凍機之預測模型。於環境溫度為25˚C時，工作流體填充壓力為4atm時，維持馬達操作頻率為30Hz為操作條件，可得到約183K之無負載製冷壁面溫度。

Free-piston Stirling cooler (FPSC) is different from traditional Stirling cooler. In mechanism structure, the position of displacer is not restricted by crank shift but only planar spring which is made by particular steel. The piston is driven by linear motor in specific frequency and stroke. However, the dynamic behavior of the displacer is difficult to predict which is influenced by mass, damping and the stiffness of the planar spring. The aim of this study is to develop a theoretical model for practical application. In this study, the dynamic behavior and all of the physic parameters are calculated by theoretical model. The movement of the displacer, volume of working zone, mass, pressure and temperature of working fluid are analyzed by theoretical model which is consist of thermodynamic model and dynamic model. The result of theoretical model shows that the pressure of working fluid of 4 atm exhibits the best performance. Therefore, the prototype of free-piston Stirling cooler is able to reach a no-load temperature of 183 K at ambient/start temperature of 298 K, operating frequency of 30 Hz and charging pressure of 4 atm.

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