|摘要: ||本研究使用玻璃製震盪式熱管，內、外徑分別為3 mm及6 mm，工作流體為去離子水及90 ppm之四氧化三鐵磁性奈米流體，填充率固定50 %，冷凝端操作溫度為25°C，輸入加熱功率20、60、100、140及180 W，分別在無磁場、不同磁通密度大小(1415、935及625高斯)及不同磁場施加狀態下進行實驗，利用數位攝影機拍攝記錄，觀察管路中工作流體的作動情形以及磁性奈米流體搭配磁場下對震盪式熱管之影響，並分析其熱阻。|
The present research a pulsating heat pipe (PHP) was made of glass material with an inner and outer diameters of 3 mm and 6 mm for 50 % fill ratio was employed. The heat input was applied at 20, 60, 100, 140 and 180 W. Distilled Water and Fe3O4 nanofluid with different concentrations of 90 ppm were used as working fluid, and cooling water temperature was set at 25 °C. Experiment was conducted under no magnetic field and three different magnetic flux density (1415, 935 and 625 Gause). In order to investigate the effects of ferrofluid and magnetic field on the thermal resistance of PHP, a video camera was set to observe the motion of working fluid in PHP, and temperatures were measured.
The results showed that addition of ferrofluid can improve the performance of pulsating heat pipe, and under the magnetic field, thermal resistance reduces with an increase in magnetic flux density and heat input for all experimental parameters; When the heat input was increased from 20W to 60W, a significant drop in thermal resistance was observed. At heat inputs higher than 100W, the thermal resistance tends to be approximately same in all the tests, indicating that the ferrofluid and magnetic field have no prominent effect on PHP. In addition, particles of the ferrofluid securely deposit on the wall under the influence of magnetic field. When the magnetic field was removed at certain wattage, the deposited particles remain deposited even with increasing heat input and oscillating frequency. Once the magnetic nanoparticles are securely deposited on the wall, it was found that the thermal performance of the pulsating heat pipe also remains unchanged, irrespective of the presence of magnetic field.