节点文献
相变储能材料在混凝土结构抗火中的应用基础研究
Applied Fundamental Research of Phase Change Stored Energy Material in the Fire Resistance of Concrete Structure
【作者】 李娜；
【作者基本信息】 西南交通大学 ， 消防工程， 2012， 硕士
【摘要】 为了提高混凝土结构抗火性能,本论文从混凝土材料组成的角度出发,以四氯化硅为原料,采用溶胶-凝胶法制备出定形性相变储能材料,再将定形性相变储能材料添加到混凝土中制成相变储能混凝土,预期通过利用相变材料的储能能力增大混凝土比热容的方法来达到提高混凝土结构抗火性能的目的。本论文开展了定形性相变储能材料的制备与表征、相变储能混凝土的制备与性能测试以及储能混凝土构件在火灾下温度场和应力场的有限元分析等工作。主要研究结果如下：1.以四氯化硅为起始原料,采用溶胶-凝胶法制备定形性相变储能材料,并用水泥加以包覆制成改性定形性相变储能材料。对定型相变储能材料的性能进行表征。1)通过扫描电子显微镜(SEM)观察定形性相变储能材料的微观形貌,发现储能物质聚乙二醇6000完好的嵌入二氧化硅的多孔结构中,且定形性相变储能材料中聚乙二醇的最高含量达85%。二氧化硅的三维网状结构提供的毛细孔作用和表面张力使得储能材料即使在相变过程仍能保持固态,解决了固-液相变储能材料在相变过程中存在的流动性和腐蚀性问题。。2)用红外光谱分析仪(FTIR)分别对纯聚乙二醇6000、二氧化硅和定形性相变储能材料的结构进行对比分析,结果发现在定形性相变储能材料中没有新峰出现,说明了复合材料中聚乙二醇与二氧化硅之间没有化学反应,二氧化硅只起到定形的作用。3)利用差示扫描量热仪(DSC)对不同聚乙二醇含量的定形性相变储能材料进行热分析,结果显示含有80%聚乙二醇的定形性相变储能材料的储能密度高达133J/g,与理论值相近,且材料的储能密度随着聚乙二醇含量的增加而增大。4)利用热重分析仪(TG)考察含有80%聚乙二醇的定形性相变储能材料的热稳定性。结果发现定形性相变储能材料在150℃以内具有良好的热稳定性。2.用定形性相变储能材料替砂制备了两类相变储能混凝土,并对拌合物的和易性、混凝土的力学性能和高温热工性能进行分析。1)分别用定形性相变储能材料和改性定形性相变储能材料替砂制备相变储能混凝土。试验发现相变储能混凝土拌合物的和易性优于普通混凝土,但是直接用定形性相变储能材料制备的混凝土养护周期需要过长,而用水泥改性后的定形性相变储能材料制备的混凝土与普通混凝土养护条件相当。2)对不同储能密度的相变储能混凝土进行轴心抗压强度测试,结果显示,用改性定形性相变储能材料完全替砂制备出的混凝土强度均比较低,而部分替砂制备出的混凝土强度得到大幅度提升。且随着储能物质聚乙二醇含量的降低,混凝土的抗压强度不断升高,目前相变储能混凝土的强度提高至10MPa,满足《混凝土结构设计规范》中对素混凝土的最低要求,此时聚乙二醇6000在混凝土中的含量为1.5%。3)对不同储能密度的混凝土的热工性能进行测试,结果显示,随着储能物质聚乙二醇在混凝土中含量的不断增大,相变储能混凝土的储能密度和比热容都不断增大,而导热系数却不断降低。3、用ANSYS软件对相变储能混凝土构件的受火行为进行有限元分析。1)对相变储能混凝土板和普通混凝土板的温度场分别进行有限元模拟,对比发现当外部热荷载相同时,同一时间下相变储能混凝土板的内部温度低于普通混凝土板内的温度,受火10min后相变储能混凝土板背火面的温度仅为普通混凝土背火面温度的30%。对不同储能密度的混凝土板中同一点在火灾中温度变化曲线进行拟合,结果显示该点的温度随着时间的推移而不断升高,但是对于不同储能密度的混凝土板,温升速率明显不同。混凝土的储能密度越高,该点的温升速率越低。2)对高温下相变储能混凝土板和普通混凝土板的应力场进行有限元对比分析发现,发现在相同的温度荷载与应力荷载耦合作用30mmin后,普通混凝土板的等效应变接近储能混凝土的2倍,即相变储能混凝土表现出更好的本构关系,且构件内部的应力场分布相对均匀。3)从温度场和应力场的有限元分析结果看出,相变储能材料的加入提高了混凝土材料高温下的热惰性,减缓了混凝土构件的升温速率,使得混凝土构件在火灾下能够更长时间的保证绝热性、稳定性和完整性,即提高了混凝土结构构件的耐火极限,从而达到了提高混凝土的结构抗火性能的目的。
【Abstract】 In order to improve the fire resistance of concrete structures, we prepared form-stable polyethylene glycol （PEG）/silicon dioxide （SiO2） composite as thermal energy storage materials by sol-gel methods, using polysilicon byproduct, then the shape-stabilized phase change materials （PCMs） were joined concrete, expected to increase the concrete specific heat with the phase change material to achieve the purpose of concrete structural fire resistance from the view of material. In this paper, preparation and characterization of form-stable phase change material, phase change energy storage concrete preparation and performance testing, finite element analysis on temperature and stress field of energy-storage concrete members were carried out.The main work of this thesis can be summarized as follows:1. With the silicon tetrachloride a new shape-stabilized PCM was simply prepared by sol-gel methods, and the modified form-stable phase change material to be coated is made with cement. Then the performance of form-stable phase change materials were investigated.（1） By SEM it was found that the polyethylene glycol is well dispersed into the network of solid SiO2due to the effect of capillary and surface tension forces. And the maximum mass percentage of PEG dispersed into the composites was found to be85%. There was no leakage of PEG from the composites up to this mass ratio even when it melts, which solved the mobility and corrosion problems in the solid-liquid phase change transition.（2） The chemical properties of the form-stable PCMs were studied by FTIR. No significant new peaks were observed, in another word, the main peaks are not changed but just a little shift, which proved that the reaction was physical.（3） The thermal analysis on the form-stable PCMs with different PEG content by DSC. The results showed that the energy density of composites with80%PEG was close to the theoretical value, up to133J/g, and the higher content of the polyethylene glycol, the higher the energy density of the form-stable PCMs.（4） TG was used to evaluated the thermal stability of form-stable PCMs. It showed the prepared PCMs had good heat resistant performance below150℃.2. Phase-change energy storage concrete were prepared with the form-stable PCMs, and the mixture workability, the mechanical properties and thermal performance were studied.（1） Different kinds of phase-change energy storage concrete were prepared using form-stable PCMs and modified PCMs. It showed that the mixture workability of energy storage concrete is superior to the ordinary one. It took too long to cure the energy storage concrete made by form-stable PCMs, but the curing cycle of modified one was almost the same with the ordinary concrete.（2） The compressive strength of phase-change energy storage concrete with different energy density were carried out. The results showed the concrete strength were low when the modified PCMs replaced sand completely, the strength was greatly enhanced when partly replaced. Moreover, the concrete strength rised with the increase of the PEG content. The current strength of phase-change energy storage concrete was up to1OMPa, which met the minimum requirements for plain concrete when the PEG content is1.5%.（3） The thermal performance of the energy storage concrete was tested. It showed that both the energy storage density and the specific heat of the concrete increased with the increase of PEG content, but the thermal conductivity reduced obviously.3. The general computation program （ANSYS） was utilized to make finite element analysis on the fire behavior of phase-change energy storage concrete members.（1） Analysis for the temperature field of concrete was carried out, it found that the internal temperature of phase-change energy storage concrete was lower than the ordinary one under the same heat load.10min later, the opposite side of the energy storage concrete member only reached30%the ordinary concrete member. The temperature of a certain point of concrete rised over time, and the higher the energy density, the smaller the temperature rising rate.（2） From the results of the stress field analysis we can see30min later the equivalent strain of ordinary concrete slab was close to2times the energy storage one when the load was same, which indicated that the phase-change energy storage concrete showed better constitutive relation.（3） Results showed that with the addition of phase-change energy storage material, the thermal inertia of concrete was improved, slowing the heating rate of concrete members, sothat the concrete structure could ensure integrity, adiabaticity and stability for longer time.