Impact of phase change wall room on indoor thermal environment in winter

Through combining gypsum boards with phase change materials (PCM), the compound phase change wallboards are formed. The transition temperature and latent heat of these phase change wallboards are tested by differential scanning calorimetry (DSC). The results indicate that these phase change wallboards can be applied in buildings to save energy cost and electric power. Then, the thermal properties of phase change wallboards are analyzed. The phase change wall room and the ordinary wall room are experimented and compared under the climatic conditions in winter in the northeast of China. The impact on the indoor temperature, surface temperature of wallboards and thermal flow through wall are achieved. Finally, it can be got that the phase change wallboards can improve indoor thermal environment.     

Experimental study and evaluation of latent heat storage in phase change materials wallboards

Phase change materials (PCM) can be applied in building envelops to conserve heat energy. Wallboards incorporated with PCM can automatically absorb indoor redundant heat, which can greatly reduce the load of HVAC systems and save electric energy. In experiments, a PCM wallboard room was constructed by attaching PCM wallboards, developed by incorporating about 26% PCM by weight into gypsum wallboards, to the surface of an ordinary wall. The transition temperature and latent heat of these PCM wallboards were tested by differential scanning calorimetry (DSC). The room testing was conducted to determine the latent heat storage of PCM wallboards. Through experiments, it could be proved that DSC can effectively predict the performance of a full-scale installation of PCM wallboards. Compared with an ordinary room, it was found that the PCM wallboard room could greatly reduce the energy cost of HVAC systems and transfer electric power peak load to valley.     

用于墙体和地板的相变材料性能

利用差示扫描量热仪研究了分别由48#石蜡和液态石蜡、癸酸和硬脂酸组成的2种二元混合物的相变温度和相变潜热,并选取其中6种试样进行5 000次热循环试验,旨在寻找适合于建筑围护结构中使用的相变储能材料.结果表明:2种二元混合物的相变温度和相变潜热随配制比例的不同发生了较为明显的变化;它们的热稳定性均较好,且脂肪酸混合物的热稳定性优于石蜡混合物.同时给出了适用于被动式相变墙体和主动式相变供暖地板或墙板中使用的相变材料混合物配比.     

使用泡沫铜增强相变材料换热性能的实验研究

针对有机相变材料(PCM)导热系数较低的缺点,通过实验研究了添加通孔泡沫铜金属材料增强相变材料导热系数的方法。选择脂肪酸二元低共熔混合物相变材料作为蓄热介质,通过对其进行DSC测试分析,得到其相变温度和相变潜热。对壳管式潜热蓄热系统填充介质为纯PCM与PCM/泡沫铜复合相变材料两种工况下的熔化过程进行对比实验研究。实验数据表明,与纯PCM蓄热系统相比,添加泡沫铜的蓄热系统换热性能得到增强,整个蓄热器内PCM达到相变温度的时间仅为纯PCM系统的22.5%。     

Thermal performance of caprylic acid/1-dodecanol eutectic mixture as phase change material (PCM)

Differential scanning calorimetry (DSC) is used to investigate the thermal properties of caprylic acid, 1-dodecanol and their binary system. The experimental results show that the caprylic acid/1-dodecanol binary system presents eutectic point. The eutectic melting temperature (T_em) is 6.52 °C, and the latent heat of melting of eutectic mixture (ΔH_em) is 171.06 J g⁻¹. The corresponding mass fraction of 1-dodecanol in eutectic mixture is 30%. The eutectic melting temperature and the latent heat of phase change of eutectic mixture have not obvious variations after 60 and 120 thermal cycles, which proves that the eutectic mixture has good thermal stability.     

新型相变储能建筑材料的制备试验研究

通过实验得出了石蜡复合体系的相变温度、相变潜热值;对比了陶粒、高性能吸附剂对石蜡的吸附能力;测试了掺入相变储能骨料的水泥试件的强度、导热性能。结果表明：经过比较,低熔点的52号石蜡与27号液体石蜡的复合体系的相变温度低．热焓值更大;高性能吸附剂对石蜡的吸附性比陶粒更好;掺入适量的相变储能骨料对水泥试件的导热性没有很大影响,但在一定程度上会降低试件的强度。     

Effects of wallboard design parameters on the thermal storage in buildings

The phase change material (PCM) could be added to the wallboard to increase the thermal mass to decrease in indoor temperature fluctuation and improve thermal comfort. In this study, experimentally validated simulation was performed to investigate the effects of various parameters of PCM including the nominal average phase change temperature, its range, the convective heat transfer coefficients and the wallboard thickness on the thermal storage performance of the wallboard such as the thermal energy storage and the time shift.It was found that the average phase change temperature should be close to the average room temperature to maximize the thermal heat storage in the wallboards. The phase change temperature should be narrow to maximize the thermal heat storage in the PCM wallboards. The thermal heat storage increased with the convective heat transfer coefficient, and the optimal average phase change temperature to maximize the storage shifted a bit to a higher temperature with it. The time shift was found to decrease with the convective heat transfer coefficient and the phase change temperature range.     

Effect of double layer phase change material in building roof for year round thermal management

Efficient and economical technology that can be used to store large amounts of heat or cold in a definite volume is the subject of research for a long time. Latent heat storage in a phase change material (PCM) is very attractive because of its high-energy storage density and its isothermal behavior during the phase change process. Thermal storage plays a major role in building energy conservation, which is greatly assisted by the incorporation of latent heat storage in building products. Increasing the thermal storage capacity of a building can enhance human comfort by decreasing the frequency of internal air temperature swings so that the indoor air temperature is closer to the desired temperature for a longer period of time. However, it is impossible to select a phase change material to suit all the weather condition in a given location. The PCM that reduces the internal air temperature swing during the winter season is not suitable for the summer season as the PCM remains in the liquid state at all the times during these months and hence the system cannot exploit the latent heat effect. This paper attempts to study the thermal performance of an inorganic eutectic PCM based thermal storage system for thermal management in a residential building. The system has been analyzed by theoretical and experimental investigation. A double layer PCM concept is studied in detail to achieve year round thermal management in a passive manner.     

Energiespeicherbeton – ein Beton mit integriertem Latentwärmespeichermaterial

Energy storage concrete – a concrete with integrated latent heat storage material. In times of solar architecture and increased utilisation of renew‐able energy, building components with high thermal heat storage capability are becoming increasingly important. One of the areas future research in building physics and building services will focus on is the development of energy storage units. A particularly interesting research area is latent heat storage. This essay describes the development of a concrete with integrated latent heat storage material (phase change material, PCM) as part of a thesis. This innovative concrete offers significantly improved thermal characteristics. For example, it was possible to more than double the heat capacity within a temperature range of 10 Kelvin around the melting point of the PCM. The PCM has a melting point between approx. 22 °C and 35 °C, depending on application. A highly versatile material such concrete offers a wide range of application options. In principle, it is possible to use latent heat storage concrete to supplement heating systems, to extend the scope of passive solar systems, or to protect against overheating in summer.     

Periodic heat transfer and load levelling of heat flux through a PCCM thermal storage wall/roof in an air-conditioned building

This communication presents an investigation of the thermal behaviour of a phase changing component material (PCCM) wall/roof which is exposed on one side to periodic solar radiation and atmospheric temperature and on the other side is in contact with room air at constant temperature. A periodic heat transfer analysis for PCCM slab has been developed (assuming effective thermal properties of PCCM) to assess the load levelling of the periodic heat flux and thermal storage characteristics of a PCCM wall/roof. It is found that a PCCM wall of thickness which is even less than that of an ordinary masonry concrete wall is more desirable for providing efficient thermal energy storage and maximum load levelling and hence is suitable for providing excellent thermal comfort in an air-conditioned building. Both the load levelling and storage duration increase with the decrease of melting temperature and increase of the latent heat of fusion of the PCCM.     

脱硫石膏基相变储能墙体材料的制备及表征

通过步冷曲线法及差示扫描量热法对不同配比的癸酸-棕榈酸二元复合相变材料的热物性进行了试验研究,确定了癸酸-棕榈酸二元复合相变材料的最佳配合比;经测试其质量损失率,选择了最佳吸附材料和封装材料。以脱硫建筑石膏为胶凝材料制备相变储能石膏。性能测试分析结果表明,当癸酸和棕榈酸质量比为7∶3时,二元复合相变材料形成低共熔体系,温度最低点为26℃。相变储能石膏的比热容约为普通石膏的2倍,具有更好的储热性能。     

Preparation and characteristics of n-nonadecane/cement composites as thermal energy storage materials in buildings

n-Nonadecane/cement composites as thermal energy storage materials (TESM) were prepared by absorbing n-nonadecane in porous network of cement. In composite materials, n-nonadecane was used as the phase change material (PCM) for thermal energy storage, and cement acted as the supporting material. Fourier transformation infrared spectroscope (FT-IR), X-ray diffractometer (XRD) and scanning electronic microscope (SEM) were used to determine the FT-IR spectra, the crystalloid phase and microstructure of n-nonadecane/cement composites, respectively. The thermal properties and thermal stability were investigated by a differential scanning calorimeter (DSC) and a thermogravimetric analysis apparatus (TGA), respectively. The SEM results showed that n-nonadecane was well dispersed in the porous network of cement. The DSC results indicated that the n-nonadecane/cement composite material has the melting latent heat of 69.12 kJ/kg with melting temperature of 31.86 °C, and solidifying latent heat of 64.07 kJ/kg with solidifying temperature of 31.82 °C.     

相变控温砂浆用于改善建筑围护结构保温性能的研究

相变控温砂浆可以借助相变材料的相变潜热和热工性能来改善建筑围护结构的保温性能,以癸酸-月桂酸二元低共熔物/改性硅藻土定形相变材料为相变蓄热介质,采用共混搅拌法掺入水泥砂浆中,制成相变控温砂浆。利用FT-IR、DSC等测试了相变砂浆化学结构及热物性,并测试了相变控温砂浆的热工参数,通过实验模拟和DesignBuilder软件模拟研究了相变砂浆用作保温材料的建筑调温效果。     

相变材料建筑节能应用效果的实验及数值模拟研究

相变材料具有高效的能量储存功能,与建筑材料复合制成有蓄热功能的新型节能建筑材料后,可应用在建筑结构中,发挥相变蓄热功能,控制建筑室内温度波动,增强建筑舒适度,更加有效地实现建筑节能。通过介绍相变蓄热建筑材料在建筑上的应用现状,对相变材料建筑节能效果进行实验模拟,阐述借助数值模拟软件和数学建模等手段进行数值模拟的研究方法和发展现状,提出相变材料建筑节能应用效果的研究方法和研究内容所存在的不足及发展潜力。     

营造可持续建筑蓄能围护结构的新思路及新方法

随着能源供求失衡日益加剧,建筑蓄能节能的重要性不断凸显。营造具有高效蓄能及可调节能力的可持续蓄能围护结构,对于建筑节能具有重要意义。本文从居住者的热舒适需求出发,通过反问题思路,提出了被动式及主动式建筑中可持续室内环境营造的一些新思路和新方法。研究发现,被动式建筑围护结构理想热质体热性能具有相变材料的特征,即热容随温度的分布接近δ函数形式。并进一步开展了建筑用相变材料的研发及应用研究,研制了建筑用定形相变材料和微胶囊化相变材料,克服了传统相变材料易泄露和导热系数偏低等缺点。最后,提出了主被动式建筑围护结构和相变材料一体化的系统应用方案,并通过实验及模拟验证了其节能舒适效果,为相变材料和建筑蓄能围护结构一体化的设计及应用提供指导。     

Mathematical modelling of PCM air heat exchanger

In order to cool a room with a cold night air phase change material, PCM, is stored in an air heat exchanger. During night the PCM crystallises, energy is released. During daytime air is circulated in the unit, energy is absorbed and the indoor air is cooled. The characteristic of PCM is that there is an increase of the specific heat over a limited temperature span. This is the principle that is used in the design of the PCM air heat exchanger unit.The action of a PCM storage unit will act differently depending of the thermal properties of the material. In an ideal material the phase transition occurs at a given temperature. On the market, compounds containing PCM are available which, in order to create a suitable melting temperature, are mixtures of different products. In these materials, the transition from liquid to solid takes place over a temperature span, i.e. the specific heat varies with the temperature. This can be represented by a c_P(T) curve, specific heat as a function of the temperature.In this paper, the development of a mathematical model of the PCM air heat exchanger is presented. Considerations are taken to different shapes of the c_P(T) curve. The mathematical model is verified with measurement on a prototype heat exchanger.The development of the equipment is part of the CRAFT project Changeable Thermal Inertia Dry Enclosures (C-TIDE) the possibility of use of phase change materials integrated into a building is explored.     

Thermoaktive Bauteilsysteme mit integrierten Phasenwechselmaterialien – eine Simulationsstudie

Thermo‐active building systems using phase‐change materials – a simulation study. The objective of this study aims at analyzing and evaluating thermo‐active building systems as well as a night ventilation concept with respect to thermal interior comfort by means of a simulation study. Preliminary experiments in a low‐energy office building facilitate the calibration of the simulation model in ESP‐r. In particular, the analysis was carried out for (i) concrete core conditioning, (ii) grid conditioning without and (iii) with 20% of micro‐encapsulated latent heat storage materials (PCM) applied to the ceiling. The central conclusions of this study are: (1) Grid conditioning provides a satisfactory room condition comparable with concrete core conditioning, (2) the application of PCM contributes to a reduced operative room temperature, and (3) in this study PCM with a melting range of 19 to 22 °C is most favorable.     

相变墙房间传热模型数学简化与求解探索

相变材料是一种高效的贮能物质,相变技术也是当前研究的热点。总结了相变材料的传热机理,以及相变材料的制备和热物理性能,并对相变墙房间模型的建立和求解的一般研究方法进行了汇总,最后针对目前的研究现状提出了急需解决和进行研究的问题。     

Stearic acid/silica fume composite as form-stable phase change material for thermal energy storage

The aim of this research is to prepare a novel form-stable composite phase change material (PCM) for the latent heat thermal energy storage (LHTES) in buildings, passive solar space heating by impregnating of stearic acid (SA) into silica fume (SF) matrix through the technique of solution impregnation. The structure, thermal properties, thermal reliability, thermal conductivity and heat storage or release performance of the composite PCM were determined by scanning electron microscope (SEM), Fourier transformation infrared (FTIR), differential scanning calorimetry (DSC) and thermal cycling test analysis technique. The results show that the form-stable composite PCM has the optimal effect, preventing the leakage of SA from the composite, emerges when the SA and SF mass ratio is 1:0.9. The SA loaded on the matrix surface by physical attraction with the mass ratio of 47% during the preparation process. The latent heat of the composite PCM is measured as 82.53 J/g for the melting process and 84.47 J/g for the freezing process, respectively, which indicate the heat storage ability of composite is connected with the mass ratio of SA in composite. The results of DSC, FTIR and thermal cycling test are all show that the thermal reliability of the composite PCM has an imperceptible change. The increase of thermal conductivity was also confirmed by comparing the melting time, freezing time and phase change time of the composite with that of SA. All of the conclusions indicate that the composite has a better thermal conductivity and good thermal and chemical stability.     

相变热回收式通风装置的研发及性能测试研究

随着建筑节能标准的提高,建筑外窗气密性要求不断提高。靠门窗渗透的自然通风量已不能满足室内空气质量的要求。采用机械通风的方式引入新风也存在着通风量的大小及通风模式会影响建筑节能的问题。为此,将相变蓄能技术应用于民用建筑的机械通风系统,研发出一种相变热回收式通风装置,以更好地解决室内空气质量和节能问题。所研发装置利用相变材料的蓄、放热性能,通过交替运行的通风模式,以及通风装置的不断循环,实现无管道式的相变热回收式建筑通风系统。主要采用实验研究的方法,在人工气候室内对研发样机进行了2个蓄、放热周期(4种工况)的测试研究。结果表明,相变热回收式通风装置的进口温度恒定、出口温度随时间不断变化,不同时间阶段呈现不同的变化趋势。第一时间阶段,即初始阶段,出口温度随时间变化剧烈,表明相变蓄能装置进入相变阶段,相变潜热量不断增大。第二时间阶段,即相变阶段,出口温度随时间呈线性变化,表明相变蓄能装置温度恒定,与空气流体发生稳定的相变传热。第三时间阶段,即完成阶段,出口温度变化小,基本接近进口温度,表明相变蓄能装置相变结束。从相变传热机理进行分析,固-液相变传热过程主要包括液态显热蓄(放)热、相变潜热蓄(放)热和固态显热(蓄)放热3个阶段,实验过程中出口温度随时间变化呈现出的几个时间阶段的不同规律,与相变传热机理有关联且相互对应。相变热回收式通风装置的风量恒定、不同进口温度工况下的对比数据表明,进口温度与相变温度的温差越大,初始阶段的出口温度变化越剧烈,相变阶段的出口温度线性变化率越大,且蓄、放热效率越高。进口温度与相变温度的温差约17℃时,蓄、放热效率分别达到56.2%(蓄)、50.8%(放)。