Comparative Analysis of Reaction to Fire and Flammability of Hemp Shives Insulation Boards with Incorporated Microencapsulated Phase Change Materials

Nowadays buildings contain innovative materials,materials from local resources,production surpluses and rapidly renewable natural resources.Phase Change Materials(PCM)are one such group of novel materials which reduce building energy consumption.With the wider availability of microencapsulated PCM,there is an opportunity to develop a new type of insulating materials,combinate PCM with traditional insulation materials for latent heat energy storage.These materials are typically flammable and are located on the interior wall finishing yet there has been no detailed assessment of their fire performance.In this research work prototypes of low-density insulating boards for indoor spaces from hemp shives using carbamide resin binder and cold pressing were studied.Bench-scale cone calorimeter tests were conducted to evaluate fire risk,with a focus on assessing material flammability properties and the influence of PCM on the results.In this research,the amount of smoke,heat release rate,effective heat of combustion,specific extinction coefficient,mass loss,carbon dioxide yield,specific loss factor,ignition time of hemp straws samples and samples of hemp straws with 10%and without PCM admixture were compared.There is a risk of flammability for PCM and their fire reaction has not been evaluated when incorporating PCM into interior wall finishing boards.The obtained results can be used by designers to balance the potential energy savings of using PCM with a more complete understanding and predictability of the associated fire risk when using the proposed boards.It also allows for appropriate risk mitigation strategies.

Heat transfer enhanced inorganic phase change material compositing carbon nanotubes for battery thermal management and thermal runaway propagation mitigation

Developing technologies that can be applied simultaneously in battery thermal management(BTM)and thermal runaway(TR)mitigation is significant to improving the safety of lithium-ion battery systems.Inorganic phase change material(PCM)with nonflammability has the potential to achieve this dual function.This study proposed an encapsulated inorganic phase change material(EPCM)with a heat transfer enhancement for battery systems,where Na_(2)HPO_(4)·12H_(2)O was used as the core PCM encapsulated by silica and the additive of carbon nanotube(CNT)was applied to enhance the thermal conductivity.The microstructure and thermal properties of the EPCM/CNT were analyzed by a series of characterization tests.Two different incorporating methods of CNT were compared and the proper CNT adding amount was also studied.After preparation,the battery thermal management performance and TR propagation mitigation effects of EPCM/CNT were further investigated on the battery modules.The experimental results of thermal management tests showed that EPCM/CNT not only slowed down the temperature rising of the module but also improved the temperature uniformity during normal operation.The peak battery temperature decreased from 76℃to 61.2℃at 2 C discharge rate and the temperature difference was controlled below 3℃.Moreover,the results of TR propagation tests demonstrated that nonflammable EPCM/CNT with good heat absorption could work as a TR barrier,which exhibited effective mitigation on TR and TR propagation.The trigger time of three cells was successfully delayed by 129,474 and 551 s,respectively and the propagation intervals were greatly extended as well.

Fatty Acid/Expanded Graphite Encapsulating Form-Stable Phase Change Materials for Energy Storage

The lauric-myristic-palmitic acid( LA-MA-PA) ternary eutectic mixtures/expanded graphite( EG) composite phase change materials( PCMs) were prepared by absorbing LA-MA-PA into the porous network of EG. The optimum ratio of ternary eutectic mixtures to EG was determined to be 93∶7 without liquid LA-MA-PA leakage from the composite PCMs. In order to make the structure more stable, the composite PCMs were encapsulated by surface treatment agent to prepare LA-MA-PA/EG encapsulating form-stable PCMs which were characterized by scanning electron microscope( SEM),Fourier transformation infrared spectroscope( FT-IR),differential scanning calorimetry( DSC) and thermal treatment. The results showed there was no chemical reaction between surface treatment agent and LA-MA-PA,and the samples were compactly encapsulated which left almost no imprint on the filter paper after thermal treatment. The phase change temperature and latent heat of LA-MA-PA/EG encapsulating form-stable PCMs were tested to be29. 32 ℃ and 96. 20 J/g,respectively. Additionally,the heat transfer efficiency of heat storage was improved by the addition of EG.

Experimental Investigation of the Operating Characteristics of a Pulsating Heat Pipe with Ultra-Pure Water and Micro Encapsulated Phase Change Material Suspension

The specific heat capacity of working fluid is an important influence factor on heat transfer characteristic of the pulsating heat pipe(PHP).Due to the relatively large specific heat capacity of micro encapsulated phase change material(MEPCM) suspension,a heat transfer performance experimental facility of the PHP was established.The heat transfer characteristic with MEPCM suspension of different mass concentrations(0.5% and 1.0%) and ultra-pure water were compared experimentally.It was found that when the PHP uses MEPCM suspension as its working fluid,operating stability is impoverished under lower heating power and the operating stability is better under higher heating power.At the inclination angle of 90°,the temperature at heating side decreases compared to ultra-pure water and the temperature at heating side decreases with the raising of MEPCM suspension mass concentration.The heat transfer characteristic of the PHP is positively correlated with the inclination angle and the 90° is optimum.The unfavorable effect of the inclination angle decreases with heating power increasing.When the inclination angle is 90°,the PHP with MEPCM suspension at 1.0% of mass concentration has the lowest thermal transfer resistance and followed by ultra-pure water and MEPCM suspension at 0.5% of mass concentration has the highest thermal transfer resistance.When the inclination angles are 60° and30°,the effect of gravity on the flow direction is reduced to 86.6% and 50% of that on the inclination angle of 90°,respectively,and the promoting effect of gravity on the working fluid is further weakened as the inclination angle further decreases.Due to the high viscosity of MEPCM suspension,the PHP with ultra-pure water has the lowest heat transfer resistance.When the inclination angles is 60°,the thermal resistance with MEPCM suspension at0.5% of the mass concentration is lower than that at 1.0% at the heating power below 230 W.The thermal resistance of MEPCM suspension tends to be similar for heating power of 230-250 W.At the heating power above 270 W,the thermal resistance with MEPCM suspension at 1.0% of the mass concentration is lower than that at 0.5%.

Preparation and phase change performance of Na_2HPO_4·12H_2O@poly(lactic acid) capsules for thermal energy storage

Micro-encapsulated phase-change materials(micro PCMs) with Na_2 HPO_4·12 H_2 O encapsulated in poly(lactic acid)(PLA) shell were prepared by a solvent evaporation–precipitation method that involves the use of a coaxial needle. The effects of PLA concentration, stirring speed, injection rate of core and shell solutions, and polyvinyl alcohol(PVA) concentration on phase change properties were investigated. The thermal properties of microP CMs were characterized by differential scanning calorimetry(DSC). The capsules prepared under the optimal conditions are about 2 mm in diameter and show a latent heat of up to 122.2 J·g^(-1).

Hierarchical Ni-plated melamine sponge and MXene film synergistically supported phase change materials towards integrated shape stability,thermal management and electromagnetic interference shielding

Along with the integrated and miniaturized development of advanced electronic devices,phase change materials(PCMs)simultaneously with efficient thermal management and high electromag-netic interference(EMI)shielding effectiveness(SE)are ungently demanded.Herein,the shape-stabilized MXene/Ni-platted melamine sponge/Regenerated cellulose/Graphene nanoplate/Polyethylene glycol(MX/Ni@MS/RCG/PEG)composite PCMs comprising hierarchical Ni@MS/RCG and MXene film were fabricated via a facile encapsulation approach.Hierarchical Ni@MS/RCG hybrid aerogel was prepared by electroless plating and sol-gel methods,and MXene film was obtained using vacuum-assisted filtra-tion procedure.The synergistic effect of conductive Ni@MS/RCG networks and tight MXene film endows MX/Ni@MS/RCG/PEG composite PCMs with good shape stability,high cyclic reliability,large latent heat of phase change(154.3 J g^(–1)),excellent thermal conductivity(TC,0.47 W m^(–1)K^(–1))and favorable EMI shield-ing performance(32.7 dB).The TC of acceptable 0.47 W m^(–1)K^(–1)is observed for MX/Ni@MS/RCG-5/PEG at a rather low GNP content of merely 0.39 wt%.In addition,the temperature variation of MX/Ni@MS/RCG-5/PEG is a lot faster than that of pure PEG in the heating/cooling process,revealing the remarkable energy storage and release efficiency for the composite PCMs.This investigation has taken an important step to-wards shape-stabilized composite PCMs with both effective thermal management and high EMI SE for promising applications in electronic packaging and advanced energy.

高温相变储热材料的宏封装及其热性能研究

文章以NaCl和Al-Si合金为高温相变材料,以氧化铝坩埚为封装容器,以高温陶瓷胶为密封材料,经低温固化和高温烧结制备了NaCl/Al_(2)O_(3)和Al-Si/Al_(2)O_(3)相变宏胶囊,并对样品的宏观形貌、相变特性、防泄漏性能及热循环性能进行测试与分析。结果表明,在50次熔化-凝固实验后,宏胶囊结构保持完整、蓄热性能稳定。且越接近相变温度点的温度区间,宏胶囊的潜热储热优势越明显。在熔点附近100℃温区内,相变材料为宏胶囊提供约70%的储热量。温度区间为500~900℃时,NaCl/Al_(2)O_(3)-30.0%相变宏胶囊的储热密度高达655J/g和1480J/cm^(3);同温区内,Al-Si/Al_(2)O_(3)相变宏胶囊的蓄热能力优于NaCl/Al_(2)O_(3)相变宏胶囊,其中Al-12Si/Al_(2)O_(3)-40.0%和Al-20Si/Al_(2)O_(3)-11.5%相变宏胶囊的单位体积储热密度分别为1524J/cm^(3)和1667J/cm^(3)。本研究为高温相变材料的封装提供了新的思路与参考,在高温相变储热领域具有广阔的应用前景。

Encapsulation of PCM for Thermo-Regulating Fabric Application

Polyethylene glycol (PEG) has been used as a phase change material (PCM) to create a thermo-regulating fabric. PEG-600 (Mw) was encapsulated using an in-situ polymerization technique in an oil-in water emulsion with encapsulating water-immiscible liquid by the reaction of urea with formaldehyde at acidic pH. Both FTIR analysis and DSC studies verified the formation of PEG microcapsules (MC). Melting temperature (Tm) of the microcapsules was found approximately 21°C which was the same as neat PEG. The heat storage capacity of these MCs was determined to be 12.78 J/g by DSC analysis. FTIR analysis of the MCs exhibited the peaks at 3211 cm﹣1, 1650 cm﹣1, and 1400 cm﹣1. These are the characteristic absorption peaks of -NH2, -C=O stretching and -CH bending vibrations, respectively. Fabric coated with PEG microcapsules showed a 20% higher thermal resistance, than the uncoated fabric, when heated on a Sweating Hot Plate (MTNW Corporation).

硅酸钠前体衍生SiO_(2)壳包覆高封装率相变胶囊的制备及性能

基于相变材料的热能储存技术是提升能源利用率、降低热能消耗、推动碳达峰碳中和目标实现的重要途径。以硅酸钠为二氧化硅壳前驱体,工业相变蜡材料为芯材,制备了一种高封装率相变胶囊。通过红外光谱(FT-IR)、X射线衍射(XRD)、扫描电镜(SEM)、差示量热(DSC)、热重(TG)等手段对相变胶囊的化学结构、微观形貌、相变性能以及热稳定性进行表征和测试。结果表明:制备了SiO_(2)壳包覆相变胶囊,当芯壳质量比为12∶1时,封装率高达81.5%,融化焓值和结晶焓值分别达138.0J/g和137.6J/g。而且相变胶囊具有良好的防泄漏性能和热稳定性。另外,热循环测试表明,即使经过200次循环,相变胶囊仍然表现出优异的循环稳定性。提出的相变胶囊制备技术具有成本低、封装率高和操作简便等优势,实际应用前景良好。

尾矿制备相变材料研究进展

我国尾矿年产量大,目前尾矿的处理方式主要有矿山回填、有价金属回收等,但难以实现尾矿的完全利用。尾矿中含有的大量石英、长石、碳酸盐矿物、硅酸盐矿物和黏土矿物等成分使其具有稳定性好、比面积大、孔隙结构丰富的特点。固-液相变材料(固-液PCMs)潜热大,但相变过程中转变为液相时易发生泄露。利用尾矿来负载固-液PCMs,既能解决其泄露问题,又能为尾矿的资源化利用提供新的途径,减轻生态环境的负担。针对尾矿资源化利用,综述了尾矿的类型及理化特性,尾矿基相变材料的封装制备、热性能提升以及应用。最后,阐述了当前尾矿制备相变材料存在的不足以及对未来研究的展望,以期为相关研究提供参考,促进尾矿在相变储热领域资源化利用的研究。

相变储能材料开发与封装技术研究进展

相变储能技术具有储热密度大、温度恒定等优点,大规模商业化潜力巨大。相变材料的开发对相变储能技术的应用至关重要,为解决相变材料传热性能差、易泄露等问题,围绕相变材料的传热和储热强化、封装开展了广泛研究。对比了热储能技术的特点,概述了潜热储能相变材料的分类与性质;并从换热面积增大以及热导率、熔化潜热和比热容提高等方面,讨论传热和储热强化研究进展;论述了相变材料的封装,对今后相变储能的发展方向进行了展望。

膨胀珍珠岩基复合相变材料研究进展

膨胀珍珠岩具有吸附能力强、稳定性好、储量丰富等优点,是相变材料的优良封装载体之一。目前,研发膨胀珍珠岩基高性能相变材料的关键在于提高其热物性性能和传热效率。综述了膨胀珍珠岩基有机、无机相变材料的封装性能、主要热物性及改善导热方面的研究进展,并展望了其未来的研究方向。

多壁碳纳米管负载银/微晶纤维素定型复合相变材料的制备及性能研究

利用相变材料储存热能是提高传统能源利用效率与开发各种新能源的有效方法。固-液相变储能材料具有成本低、凝固点调节范围宽和相变焓值大等优势,成为相变材料中应用极为广泛的相变材料之一。然而,由于相变材料在使用过程中会出现低导热率和泄漏问题,在极大程度上限制了相变材料的实际应用。为了解决以上问题,本工作将负载银纳米粒子的氧化碳纳米管(O-MWCNTs)引入到微晶纤维素(MCC)基体中制备了微晶纤维素/多壁碳纳米管负载银(MCC/Ag-MWCNTs)三维多孔骨架,利用MCC/Ag-MWCNTs复合骨架吸附棕榈酸(PA)得到了MCC/Ag-MWCNTs/PA(Ag-PMCT)复合相变材料。O-MWCNTs上丰富的银纳米粒子在碳纳米管上形成微“桥梁”,从而构筑完整的导热路径,进一步提高复合相变材料的储热性能。同时,MCC/Ag-MWCNTs复合三维骨架展示出良好的封装效果和形状稳定性。本工作所制备的Ag-PMCT复合相变材料在建筑节能领域和电子器件热管理方面具有潜在应用,同时为碳基材料和金属粒子共同增强相变材料的导热性提供了一种新的思路。

封装相变材料在道路防冰中的研究进展

固-液相变材料因液相泄露问题无法直接使用,利用封装技术包覆相变材料,可以扩展固-液相变材料应用领域。本文主要介绍了封装固-液相变材料的方法,概述了基于封装技术制备的复合相变材料的防冰机理和应用策略,为封装相变材料在道路防冰中应用提供参考,并对其未来的研究趋势进行展望。

三元脂肪酸/膨胀石墨复合相变材料的制备、包覆定形及热性能

采用癸酸、月桂酸和棕榈酸的三元共晶混合物作为相变材料,以膨胀石墨为基体,通过膨胀石墨多孔结构的毛细吸附和复合涂饰剂的包覆定形,将多元相变材料固定在膨胀石墨的孔道结构中,制备出结构稳定、密封性能优异、热稳定性好和高导热的新型三元脂肪酸/膨胀石墨复合定形相变材料.膨胀石墨具有膨胀疏松的多孔结构和良好的吸附性能;其熔融潜热为95.6 J/g,结晶焓为82.8 J/g,说明其具有很好的相变蓄热特性和热循环稳定性;材料的导热性能可增加至0.738 W/(m.K),与脂肪酸相比得到大幅度提高.

微胶囊相变材料在建筑节能领域的研究与应用

如何对固-液相变材料进行有效的封装,是阻碍其规模化应用的主要难点之一。微胶囊技术以其独特的优势,近年来得到国内外专家的广泛关注。介绍了可作为芯材的相变材料及相应的壁材、两种典型的微胶囊制备工艺,重点总结了微胶囊的表征方法,同时讨论了国内外微胶囊相变材料在建筑节能领域中的应用现状、存在的问题以及发展前景。

纳米技术在强化传热中应用的研究进展

采用纳米技术,通过改变传热流体的物性和流动特征以及传热表面的特性,能有效地强化传热。本文综述了纳米流体、纳米胶囊粒子潜热型热流体以及纳米涂层表面在强化传热中应用的研究进展,分析了各种纳米技术的强化传热机理,指出了现有研究工作存在的问题和今后研究的方向。

相变储能微胶囊的制备及其复合材料的研究进展

综述了微胶囊相变材料(MCPCM)的结构组成,重点介绍了微胶囊常见的制备方法,包括原位聚合法、界面聚合法、悬浮聚合法等,并对相变储能复合材料在节能建筑、流体强化传热、保温纺织品、军事隐身等领域中的应用研究进展进行了介绍,指出目前微胶囊相变材料在理论研究及实际应用方面存在的问题。

NaCl和分散剂对相变储能蜡微胶囊制备的影响

以常低温相变储能蜡RT31为芯材,脲醛树脂为壁材,采用原位聚合法制备了相变储能蜡微胶囊。利用傅立叶红外光谱仪、扫描电子显微镜、差示扫描量热仪等对样品进行分析和表征,讨论了助剂NaCl及两种不同类型的分散剂对微胶囊性能和形貌的影响。实验结果表明,加入一定量的NaCl能显著提高微胶囊的相变潜热,使得微胶囊的包封率由75.8%升高到92.5%,在微胶囊成型后期加入一定量的分散剂能明显改善微胶囊的表面形貌和粒径均匀度。

氧化石墨烯改性密胺树脂/石蜡相变微胶囊的制备及性能

通过原位聚合法制备了氧化石墨烯(GO)改性的密胺树脂(MF)/石蜡相变微胶囊。采用红外光谱、扫描电镜、差示扫描量热分析、热重分析等手段分析了相变微胶囊的微观结构及热性能,研究了GO含量对相变微胶囊形貌、包覆率和渗漏率的影响。研究结果表明,制备的相变微胶囊为较规则的球形,GO的加入并没有改变壁材或芯材的化学结构;GO改性使相变微胶囊的包覆率由91.39%提高至94.08%,增大了相变微胶囊的储能能力;GO改性相变微胶囊的防渗性能得到大幅提升,250h时的渗漏率由9.43%下降至2.68%,下降了71.6%,相变微胶囊的使用寿命得到提高。