第一部份是將二種不同濃度(100ppm及450ppm)之銀奈米流體，充填於內徑2.4mm的銅管中，以作震盪式熱管性能之測試；其填充率各為20%、40%、60%及80%四種，功率從5W加熱至85W，比較不同濃度及填充率之熱管性能為何；最後實驗結果顯示，濃度相同之最佳填充率是為60%，填充率相同之最佳濃度則為100ppm；如加熱功率與填充率相同(85W、60%)， 則100ppm之銀奈米流體，其加熱段與冷凝段之溫差較純水低7.79°C、熱阻值亦較純水少0.092°C /W。
This dissertation has three parts. The first part describes the nano-fluid applicable to the study of PHP with copper tubes. The second part discusses the materials used in PDMS applying to PHP research and finally a discussion of observations made in the research project.
The first part presents preliminary experimental results on using copper tube having internal and external diameter with 2.4mm and 3mm respectively to carry out the experimental pulsating heat pipe. The working fluids include the silver nano-fluid water solution and pure water.
In order to study and measure the efficiency, we compare with 20nm silver nano-fluid at different concentration (100ppm and 450ppm) and various filled ratio (20%, 40%, 60%, 80% respectively), also applying with different heating power (5W, 15W, 25W, 35W, 45W, 55W, 65W, 75W, 85W respectively). According to the experimental results in the midterm value (i.e. 40%, 60%) of filled ratio shows better performance results. In the majority 60% of efficiency is considered much better. The heat dissipation effect is analogous in sensible heat exchange, where 60% has more liquid slugs that will carry more sensible heat, so in 60% of filled ratio, the heat dissipation result is better than 40%, and the best filled fluid is 100ppm silver nano-fluid.
We observed through the measurement comparison in thermal performance with pure water. When the heating power is 85W, the average temperature difference and the thermal resistance of evaporator and condenser are decreased by 7.79ºC and 0.092ºC /W respectively.
The second part reports on preliminary experimental results of using polydimethylsiloxane (PDMS) to manufacture a visual pulsating heat pipe with length, width and internal diameter are 56mm, 49mm and 2mm respectively, including the manufacturing process and the vacuuming management for filling and packaging. The experiment used methanol and ethanol as the working fluid. A fix filled ratio (about 60%) and different heating power values (3W to 8W) were used to test thermal performance. A high-speed video camera was used to record the working situation of the working fluid inside the channel. The results are discussed and analyzed.
The experiment discussed in the third part shows that methanol, in a vertical orientation, shows the most efficient results. When the heating power is 3W, the thermal resistance is more than 4.5ºC/W below the value for ethanol as the working fluid. For a heating power of 4W, the average temperature decreases to 15ºC in the evaporator. Also gravity will have impact on the PHP performance: The vertical orientation is the better one, as compared to the horizontal orientation.
Inside the channel of the PDMS PHP, different heating powers were employed to observe the working situation, flow direction of the vapor plug, liquid slug and the structure form of the flow. A high speed video camera was used to record the formation, combination, collapse, flow direction and the different kinds of flow of the bubble. At the same time, we can find out the vapor plug and liquid slug are unstable and uneven in growth and distribution which caused the PDMS PHP to oscillate and work.