【作者】 万伟军；

【导师】 方玉堂；

【作者基本信息】 华南理工大学 ， 化学工程， 2010， 硕士

【摘要】 随着化石能源价格的不断上涨和环保意识的增强,节能降耗成为了人们的关注焦点。相变储能技术能解决能量供求在时间和空间上不匹配的矛盾,是提高能源利用效率的有效手段之一。将相变材料应用于普通流体中形成的潜热型功能热流体,是一种特殊的固-液两相流体,由于胶囊化的相变材料融化时能释放大量潜热,增大了有效比热容,且相变颗粒间的微对流效应,强化了管路壁面的热传导性能,与普通流体相比,它可明显强化流体的传热能力,是一种集储热与强化传热功能于一身的新颖材料。本文以正十四烷(Tet)为芯材,聚苯乙烯(PS)为壁材,采用超声乳化、原位细乳液聚合的方法,制备了蓄冷型纳米胶囊相变乳液。系统考察了超声功率、超声时间,亲水性共聚单体、乳化剂、助乳化剂、引发剂、链转移剂(或交联剂)以及芯壳比等因素对纳米胶囊形态、粒径以及热性能的影响。应用纳米粒度仪、透射电子显微镜(TEM)、傅立叶红外光谱(FTIR)、差示扫描量热(DSC)以及热失重(TG)等分析手段对纳米胶囊的形貌、蓄热性能以及热稳定性进行了表征。研究表明:苯乙烯聚合链具有强疏水性,不易相分离而形成包囊,添加亲水性单体,可改善胶囊的稳定性;复合乳化剂有助于形成大小均一、稳定的胶囊乳液;适量链转移剂的加入使相分离更容易,促进胶囊化;油溶性引发剂有助于形成形状规则、大小均匀的胶囊,水溶性引发剂容易形成聚合物实心粒;核壳配比影响胶囊的热性能及壳层强度,进一步影响着胶囊的相变焓值。适宜的纳米胶囊相变材料乳液制备条件为:超声功率调整值为50%(额定功率900W);超声乳化时间为10min;反应时间为5h;Tet与St的比例为1:1;亲水型共聚单体丙烯酸乙酯(EA)为2.5%(油相质量百分比,下同);链转移剂正十二硫醇(DDT)为0.1%;复合乳化剂(十二烷基硫酸钠(SDS)和辛烷基酚聚氧乙烯醚-10(OP-10))配比为1:1,总用量为3%;引发剂偶氮二异庚腈(ABVN)0.4%。制备的纳米胶囊平均粒径为132nm,相变焓能达到98.71 kJ/kg,具有较好的储能能力。乳液的性能测试表明,制备的纳米胶囊乳液(胶囊质量含量15%)具有较小粘度(25℃时粘度为8.3cP),导热性能(导热系数为0.8467 W/m·K)和比热容(7℃左右比热容能达到4.8 J/g·℃)均优于水,乳液经过多次冷热循环后热性能基本不变,且具有很高的机械稳定性,可作为蓄冷用功能热流体使用。更多还原

【Abstract】 Due to the rising cost of fossil fuels and environmental concerns, more and moreattention has been paid to energy conservation lately. Thermal energy storage (TES) usingphase change materials (PCM) can solve the problem in time and spatial mismatch betweenthe energy supply and the consumption of energy, and play an important role in increasingefficiency of energy utilization. Latent functionally thermal fluid (LFTF), which encapsulatedphase change material dispersed in heat transfer fluid, is a solid-liquid two-phase fluid.Because the latent heat released from phase change materials can enlarge heat capacity offluid, and the existence of micro-convection around the PCM capsules can enhance heattransfer efficiency, therefore, the LFTF is novel multifunctional fluid which can combine thethermal storage and the thermal transmission in one.In this paper, the nanoencapsulated phase change materials (NEPCMs) with polystyrene(PS) as shell and n-tetradecane (Tet) as core were synthesized by ultrasonic technique andminiemulsion in-situ polymerization. The influence of polymerization factors such asultrasound power and time, hydrophilic co-monomer, emulsifier, co-emulsifier, initiator, chaintransfer agent, and the ratio of n-tetradcane and styrene on the morphology, particle size andthermal property of nanocapsules were systematically investigated. The samples werecharacterized by particle size analyzer, transmission electron microscope (TEM), fouriertransform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC) andthermogravimetric analyzer (TG). The results showed that, due to the strong hydrophobicityof polystyrene chain, it isn’t easy to separate and encapsulate, while adding hydrophilicco-monomer, it is easy to form steady capsules; the composite surfactants contribute to formuniform and steady nano-latex; the proper amount of chain transfer agent might facilitatephase separation and form regular capsules; using 2,2′-azobisisoheptonitrile (ABVN) as initiator, the capsules with good encapsulation can be obtained, while using potassiumpersulfate (KPS), the solid bead is easy to form; the ratio of Tet and St has a great effect onthe themal property and the strength of polmer shell, which change phase change enthalpy.The optimized experimental conditions were that 50% (rated power is 900w) poweradjusted value of ultrasonic, 10 min ultrasonic time, 5hr reaction time, 1:1 ratio of Tet and St, 2.5% hydrophilic ethyl acrylate (EA) co-monomer, 0.1% dodecanethiol (DDT) chain transferagent, 3% composite surfactants which composed sodium dodecyl sulfate(SDS) andpoly-(ethylene glycol) monooctylphenyl ether(OP-10) by 1:1 in weight ratio and 0.4%2,2′-azobisisoheptonitrile(ABVN). Under this conditions, the average particle size of prepared nanocapsules was 132 nm and the phase change enthalpy was 98.71 kJ?kg-1.The test result forlatex showed that the nanocapsule emulsion (15% mass fration) has low viscosity (8.3cP at25℃), good thermal conductivity(0.8467 W/m·K at 25℃) and excellent specificheat(4.8J/g·℃at 7℃). After more than forty times freezing-melting circulation, the latexhas well thermal property and mechanical stability which is suitable as cool storage media.更多还原