纳米粒子热力学性质及纳米流体强化传热研究

【作者】 董丽娜；

【导师】 段树林；

【作者基本信息】 大连海事大学 ， 轮机工程， 2005， 硕士

【摘要】 随着对热交换设备换热表面强化传热技术研究的深入,换热工质的传热性能已成为影响热交换设备高效紧凑性能的一个主要因素,低导热系数的换热工质已成为研究新一代高效冷却技术的主要障碍。 纳米材料科学的迅速发展给强化传热领域带来了新的机遇,有学者提出了一个崭新的概念-纳米流体:即以一定的方式和比例在液体中添加纳米级金属或非金属氧化物粒子,形成一类新的传热冷却工质。 本文综合应用纳米材料技术和传热理论,为了研究纳米颗粒的加入如何改变工质的热力学参数,对不同的纳米颗粒进行了实验测定,给出了各纳米颗粒样品的表征;测定了各纳米颗粒样品的热容并用最小二乘法拟合出其摩尔热容与温度系数的多项方程。 本文将各个纳米颗粒样品实验测定的热容与其对应的粗晶热容和其它文献中的纳米颗粒实验热容对比,得出:在110K～390K的温区,纳米颗粒的比热容地随纳米颗粒尺寸的减小而递增的结论。 本文分别从晶格振动理论和点阵动力学理论,来研究纳米颗粒比热容,建立了纳米颗粒比热容的理论模型,给出了相应的公式,并计算了纳米颗粒的热容;将其与实验热容进行比较分析,得出了晶格振动理论模型比点阵动力学理论模型更加精确的结论。 为了研制新型高效纳米流体传热工质,研究纳米流体强化传热机理和性能,采用了不同种类、不同粒径的纳米颗粒来配置的纳米流体来进行实验研究。本文针对所配置的不同种类、不同质量浓度的纳米流体,进行热重测试和热量扫描测试,将实验结果进行对比,得出了纳米粒子属性、质量浓度、粒径以及纳米流体悬浮稳定性等因素对纳米流体的相变速率等热物性的影响规律。 本文通过理论分析和实验研究,为研制新型高效纳米流体传热工质,研究纳米流体强化传热机理和性能,提供了有效的实验方法和可靠的实验数据。更多还原

【Abstract】 With the progress of thermodynamics and thermal engineering, many efforts have been devoted to the heat transfer enhancement. Although a variety of techniques are available to enhance heat transfer, major improvements in heat transfer capabilities have been held back because of the low thermal conductivity of conventional heat transfer fluids. Improvement of the thermal properties of energy transmission fluids is becoming a promising method of heat transfer enhancement.Modern nanotechnology provides new challenges and opportunities for thermodynamics. Some scholars put forward the brand-new conception of nanofluids which is a kind of heat transport carriers by appending nanoscaled metallic or nanometallic particles in basic fluids. Nanofluids are expected to exhibit heat transfer properties because nanofluids is superior to those of conventional heat transfer fluids.The nanotechnology and the heat transfer theory are applied in this dissertation. In the interest of investigating how the accession of nanoparticles changes the thermodynamics parameter, different nanoparticles have been mensurated. The token and heat capability of nanoparticles were provided, heat capability of nanoparticles are mensurated and the equation of heat capability and temperature quotiety is gained by lease quadric multiply method.The heat capability of nanoparticles mensurated is compare with that of corresponding coarse crystal and others in this dissertation and draw a conclusion.during the temperature section of 110K-390K, the heat capability of nanoparticles is increase by degrees along with the devrease of nanoparticles’ size.By using both of the crystal lattice vibrant theory and lattice kinetic theory, the heat capability of nanoparticles is researched in this dissertation. The theoretical model of the nanoparticles is founded, and the relevant formulas are listed, then the heat capacity of nanoparticles is calculated out, and by comparing with the experimental heat capacity the result is drawed: the crystal lattice vibrant theory is accurater than lattice kinetic theory.In the interest of developing new type and effective heat transfer nanofluids and investigating mechanism and performance of heat transfer enhancement, nanofluids of different kinds and different particle sizes have been investigate throught experiment.Tests of heat weightlost and quantity of heat are done on nanofluids which collocated by different kinds and different particle sizes with different quality chroma and compare the experiment result, then find infection rule of nanoparticles property , quality chroma ,size,and suspend stability on nanofluids.Through the theoretic analysis and the experiment, this dissertation provide effective experiment method and credible experiment date for developing new high effect heat transfer intermedium of nanofluids and research of the mechanism and performance of nanofluids heat transfer enhancement.更多还原