本研究為探討奈米流體於迴路式虹吸熱管之熱性能影響。奈米流體為平均粒徑30nm銀奈米顆粒混合於水溶液中。 虹吸熱管蒸發室之尺寸為內徑25mm、高25mm；並於內部製作兩種的沸騰結構來研究其影響。第一種為平滑的沸騰表面，第二種為長寬17mm×17mm、厚度1mm、粒徑大小183.5μm、孔隙率53.7%的銅粉燒結結構。實驗元件為使用恆溫水槽進行冷卻，並固定流量與溫度20度之條件來進行實驗。實驗將以量測迴路式虹吸熱管之溫度分佈與溫差，來比較奈米流體與純水充填於迴路式虹吸熱管之性能。 實驗結果顯示使用平滑的沸騰表面時，在260W的輸入功率，濃度30ppm銀奈米流體的整體效能比純水提昇13.82%。當使用增強沸騰結構時，濃度20ppm銀奈米流體的整體體效能比純水提昇0.12%。 The purpose of this thesis is to study the effects of silver nano-fluids on loop thermosyphon thermal performance. The nano-fluid used in this study is an aqueous solution 30nm diameter silver nanoparticles. The evaporator chambers of thermosyphon used in this study has an inside diameter of 25 mm and a height of 25 mm. Two types of boiling structures in evaporator chambers have fabricated to investigate the influence. The first type of boiling structures is flat with smooth boiling surface. The second one is 17.3mm square, 1mm thickness of sintered copper powder structure. The average diameter of copper powder and the porosity is 185.5μm and 53.7%, respectively. The tested device was condensed by the thermal bath with constant flow rate at 20℃. The experiment was performed to measure the temperature distribution and the temperature difference to compare the thermal performance of nano-fluid and DI-water. Based on the smooth boiling surface of evaporator chambers, the experimental result of 30ppm silver nanofluid showed that thermal resistance enhanced 13.82% compared to DI-water at an input power of 260W. While the loop thermosyphon were with copper powder structure in the evaporator chamber, the thermal performance improved 0.12% at 20ppm silver nanofluid compare with DI-water.