三氧化二鋁奈米流體應用於板式熱交換器之性能研究

A Study on the Performance of Al2O3 Nanofluids Applied to Plate Heat Exchanger

張冠彥(KUAN-YEN CHANG)

指導教授 ： 卓清松

國立臺北科技大學/機電學院/能源與冷凍空調工程系碩士班/碩士(2009年)

摘要

本研究使用商用15nm的三氧化二鋁奈米顆粒以二階混合法分散懸浮於添加陰離子分散劑之去離子水中製備成奈米流體，以實驗研究法探討三氧化二鋁奈米流體在不同溫度條件、顆粒濃度與分散劑添加量的情況下對其熱、流性質所造成之影響，並實際應用於板式熱交換器系統，評估奈米流體應用做為板式熱交換器工作流體之可行性。由本研究結果可以發現：濃度1.0%wt的三氧化二鋁奈米流體在溫度40℃時，其熱傳導係數能夠提升11.6%，10℃與20℃的溫度條件時，熱傳導係數會與分散劑的添加量呈反比，30℃與40℃的溫度條件下熱傳導係數會與分散劑的添加量呈現正比。量測黏滯係數發現添加分散劑會造成流體的黏滯係數升高，但無論添加分散劑與否三氧化二鋁奈米流體之流變行為皆接近於牛頓流體。在沉降實驗中發現奈米顆粒濃度1.0%wt添加1.0%wt分散劑的奈米流體，經過20天的靜置後其沉降行為低於0.3%。在板式熱交換器實驗中使用濃度為1.0%wt添加1.0%wt分散劑的奈米流體，在流速為3.4 L/min工作溫度為40℃的情況下，總熱傳係數增進可達68.1%。
本研究針對三氧化二鋁奈米流體進行一系列的基礎實驗與應用實驗研究，主要貢獻在於確認添加分散劑對於奈米流體性質之影響，並實際應用於板式熱交換器性能研究中，證實奈米流體應用於板式熱交換器系統有助於提高能源使用效率。

關鍵字

奈米流體 ； 板式熱交換器 ； 沉降現象 ； 分散劑

並列摘要

The study uses two-step synthesis to disperse and suspend the 15mm aluminum oxide (Al2O3) nanoparticles in deionized water, in which anion dispersant is added to prepare nanofluids. Using experimental research method, the paper investigates how Al2O3 nanofluids under different temperature conditions, particle concentrations and added amounts of dispersants affects its thermal and rheological properties, and practically applies it to plate heat exchanger system. The study evaluates the application of nanofluids to judge the feasibility of the working fluid of plate heat exchanger. As found in the research result, the thermal conductivity coefficient of Al2O3 nanofluids at concentration 1.0%wt. can be enhanced by 11.6% under the temperature 40℃. When the temperature conditions are 10℃ and 20℃, the thermal conductivity coefficient of Al2O3 nanofluids appears to be inversely proportional to the added amount of dispersant. When the temperature conditions are 30℃ and 40℃, the thermal conductivity coefficient of Al2O3 nanofluids appears to be positively proportional to the added amount of dispersant. From the measured viscosity, it is found that adding dispersant can increase the viscosity coefficient of fluid. However, with or without the addition of dispersant, the rheological behavior of Al2O3 nanofluids is close to that of Newtonian fluid. In the sedimentation experiment, it is found that after the nanoflluid with nanoparticles at concentration 1.0%wt. added with dispersant at 1.0%wt. is placed static for 20 days, its sedimentation is lower than 0.3%. In the experiment of plate heat exchanger, when the nanofluids at concentration 1.0%wt. added with dispersant at 1.0%wt. operates under the temperature 40℃ at the flowing speed 3.4 L/min., the overall heat transfer coefficient can be enhanced by 68.1%. The study performs a series of fundamental experiments and makes applied experimental research of Al2O3 nanofluids, with the main contributions to confirm the effects of dispersant addition on the properties of nanofluids, and to practically apply it to the performance study of plate heat exchanger. It is proved that the application of plate heat exchanger is helpful to the enhancement of utility efficiency of energy.

並列關鍵字

nanofluids ； plate heat exchanger ； sedimentation ； dispersant

參考文獻

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