Enhanced Thermal Performance of Roofing Materials by Integrating Phase Change Materials to Reduce Energy Consumption in Buildings

This work focused on characterizing and improving the thermal behavior of metal sheet roofing.To decrease the heat transfer from the roof into a building,we investigated the efficiency of four types of phase change materials,with different melting points:PCMІ,PCM II,PCM III and PCM IV,when used in conjunction with a sheet metal roof.The exterior metal roofing surface temperature was held constant at 50℃,60℃,70℃and 80℃,using a thermal source(halogen lights)for 360 min to investigate and compare the thermal performance of the metal sheet roofing with and without phase change materials for each condition.The thermal behaviors of the phase change materials were analyzed by differential scanning calorimeter(DSC).The results showed the melting points of PCMІ,PCM II,PCM III and PCM IV were around 45℃,50℃,55℃and 59℃,respectively.The integration of PCM IV into the metal roofing sheet increased the thermal performance by reducing the room temperature up to 2.8%,1.4%,1.0%and 0.7%when compared with the normal metal roof sheet,at the controlled temperatures of 50℃,60℃,70℃and 80℃,respectively.The thermal absorption of the phase change materials also caused a time delay in the model room reaching a steady temperature.The integration of phase change materials with metal roofing sheets resulted in better thermal performance and conservation of electrical energy by reducing the demand for cooling.

Simulation of the Hygrothermal Behavior of a Building Envelope Based on Phase Change Materials and a Bio-Based Concrete

Phase Change Materials(PCMs)have high thermal inertia,and hemp concrete(HC),a bio-based concrete,has strong hygroscopic behavior.In previous studies,PCM has been extensively combined with many materials,however,most of these studies focused on thermal properties while neglecting hygroscopic aspects.In this study,the two materials have been combined into a building envelope and the related hygrothermal properties have been studied.In particular,numerical studies have been performed to investigate the temperature and relative humidity behavior inside the HC,and the effect of adding PCM on the hygrothermal behavior of the HC.The results show that there is a high coupling between temperature and relative humidity inside the HC,since the relative humidity changes on the second and third days are different,with values of 8%and 4%,respectively.Also,the variation of relative humidity with temperature indicates the dominant influence of temperature on relative humidity variation.With the presence of PCM,the temperature variation inside the HC is damped due to the high thermal inertia of the PCM,which also leads to suppression of moisture evaporation and thus damping of relative humidity variation.On the second and third days,the temperature changes at the central position are reduced by 4.6%and 5.1%,compared to the quarter position.For the relative humidity change,the reductions are 5.3%and 5.4%on the second and third days,respectively.Therefore,PCM,with high thermal inertia,acts as a temperature damper and has the potential to increase the moisture buffering capacity inside the HC.This makes it possible for such a combined envelope to have both thermal and hygric inertia.

Study on Phase Change Material in Grooved Bricks for Energy Efficiency of the Buildings

Phase change materials(PCMs)are an interesting technology due to their high density and isothermal behavior during phase change.Phase change material plays a major role in the energy saving of the buildings,which is greatly aided by the incorporation of phase change material into building products such as bricks,cement,gypsum board,etc.In this study,an experiment has been conducted with three identical small chambers made up of normal,grooved and PCM-treated grooved bricks.Before the inclusion of PCM in grooved bricks,PCM material behavior has been studied by different techniques such as DSC,TG/DTA,SEM,and XRD.Thermal properties and thermal stability were investigated by differential scanning calorimeter(DSC)and thermogravimetric analyzer(TGA)respectively.Scanning electron microscopy(SEM)and X-ray diffraction(XRD)were used to determine the microstructure and crystalloid phase of the PCM before and after the accelerated thermal cycling test(0,60,120).These three identical model rooms built were exposed at a temperature just above 40°C with a heater.When the maximum outdoor temperature was 40-41°C,then the temperature of the PCM-treated grooved chamber was 32-33°C.The PCM-treated wall was tested and compared with a conventional and grooved wall.The difference between the PCM-treated grooved chamber and the untreated one was 8-9°C.PCM-treated bricks provided more efficient internal heat retention in summer when the outside temperature increased.

Comparative Study of Two Materials Combining a Standard Building Material with a PCM

Phase change materials(PCMs)have the ability to store thermal energy and make it available at a later stage to keep indoor temperature within a specific range and achieve better thermal comfort in buildings.This study focuses on the performances of materials obtained by combining a standard building material with a PCM.In particular,two different materials mixed with the same PCM are considered under the same climatic conditions.The related thermal behavior is assessed in the framework of numerical simulations conducted with ANSYS Fluent assuming parameters representative of a city located in Europe.The results show that the addition of PCM to concrete and bricks can improve the thermal inertia of the resulting material.

Preparation and Properties of Paraffin/PMMA Shape-stabilized Phase Change Material for Building Thermal Energy Storage

The composite phase change material(PCM) consisting of phase change paraffin(PCP) and polymethyl methacrylate(PMMA) was prepared as a novel type of shape-stabilized PCM for building energy conservation through the method of bulk polymerization. The chemical structure, morphology, phase change temperature and enthalpy, and mechanical properties of the composite PCM were studied to evaluate the encapsulation effect of PMMA on PCP and determine the optimal composition proportion. FTIR and SEM results revealed that PCP was physically immobilized in the PMMA so that its leakage from the composite was prevented. Based on the thermo-physical and mechanical properties investigations, the optimal mass fraction of PCP in the composite was determined as 70%. The phase change temperature of the composite was close to that of PCP, and its latent heat was equivalent to the calculated value according to the mass fraction of PCP in the composite. For estimating the usability in practical engineering, thermal stability, reliability and temperature regulation performance of the composite were also researched by TG analysis, thermal cycling treatments and heating-cooling test. The results indicated that PCP/PMMA composite PCM behaved good thermal stability depending on the PMMA protection and its latent heat degraded little after 500 thermal cycling. Temperature regulation performance of the composite before and after thermal cycling was both noticeable due to its latent heat absorption and release in the temperature variation processes. The PCP/PMMA phase change plate was fabricated and applied as thermal insulator in miniature concrete box to estimate its temperature regulation effect under the simulated environmental condition. It can be concluded that this kind of PCP/PMMA shape-stabilized PCM with the advantages of no leakage, suitable phase change temperature and enthalpy, good thermal stability and reliability, and effective temperature regulation performance have much potential for thermal energy storage in building energy conservation.

Performance analysis of thermal storage unit with possible nano enhanced phase change material in building cooling applications

The heat transfer performance of the phase change materials used in free cooling and air conditioning applications is low,due to the poor thermal conductivity of the materials.The recent phenomenal advancement in nano technology provides an opportunity for an appreciable enhancement in the thermal conductivity of the phase change materials.In order to explore the possibilities of using nano technology for various applications,a detailed parametric study is carried out,to analyse the heat transfer enhancement potential with the thermal conductivity of the conventional phase change materials and nano enhanced phase change materials under various flow conditions of the heat transfer fluid.Initially,the theoretical equation,used to determine the time for outward cylindrical solidification of the phase change material,is validated with the experimental results.It is inferred from the parametric studies,that for paraffinic phase change materials with air as the heat transfer fluid,the first step should be to increase the heat transfer coefficient to the maximum extent,before making any attempt to increase the thermal conductivity of the phase change materials,with the addition of nano particles.When water is used as the phase change material,the addition of nano particles is recommended to achieve better heat transfer,when a liquid is used as the heat transfer fluid.

Thermal performance of a lightweight building with phase change material under a humid subtropical climate

The use of phase change materials(PCMs)in building enclosures is an efficient way to reduce the heat gain and/or loss in summer and winter.It was evident that the thermal performance of buildings with PCMs was affected by the outdoor air temperature significantly.However,the influence of humidity,which was serious in the humid subtropical climate was unclear.To explore the effect of PCMs under a humid subtropical climate,the thermal performance of a lightweight building outfitted with PCMs with a melting temperature of 25°C was investigated.The actual outdoor air temperature with a humidity of 40-90 RH%and wind velocity of 2-6 m/s blowing from the east,west,south,and north was assumed for the performance assessment.A simulated model was developed using EnergyPlus and verified against experimental data.The energy savings by using PCMs was reduced from 3.9%to 2.6%when the outdoor humidity increased from 40 to 90 RH%in summer.However,the savings was not obvious in winter.Annual energy savings decreased from 1.64%to 1.32%with humidity increasing from 40 to 90 RH%.For annual condition,the average energy savings was reduced from 1.43%to 0.92%when the wind speed increased from 2 m/s to 6 m/s.From an economic point of view,the investment payback period was less than 10 years when the PCM price was lower than 18.0 Yuan/kg.

Investigation of heat transfer of a building wall in the presence of phase change material(PCM)

The energy consumption in buildings for heating,ventilation,and air-conditioning is increasing with the in-creasing demand for thermal comfort.Thermal energy storage with phase change material(PCM)has attracted growing attention for its role in achieving energy conservation in buildings with thermal comfort.This paper investigates the effect of PCM on the heat transfer rate in a building wall and the role of PCM on the indoor thermal comfort of the building.Two models of building wall fragments were developed for the experimental study.In one model,tests were conducted for different positions of the PCM layer in the building wall to identify the optimal position of the PCM layer inside the wall.In another model,tests were carried out integrating PCM,air gap,and other conventional building materials(brickbat and sand),one at a time,to investigate the role of PCM on the heat transfer rate in the building wall fragment.The results show that placing the PCM layer closer to the heat source gives a low-temperature gain of the cold water bath(indoor state)as compared with the PCM layer near the heat sink.With PCM,the temperature rise of the cold water bath(indoor state)of the building wall fragment was the lowest,and the slope of the temperature rise of the cold water bath becomes steadier with time i.e.,fewer temperature fluctuations.There was a significant time delay for the cold water bath to reach a given temperature.The heat required for a unit degree increase in the temperature of the cold water bath was higher and the peak heat flux of the wall was lower relative to the other building materials.

Review on thermal performance of phase change energy storage building envelope

Improving the thermal performance of building envelope is an important way to save building energy consumption. The phase change energy storage building envelope is helpful to effective use of re-newable energy, reducing building operational energy consumption, increasing building thermal com-fort, and reducing environment pollution and greenhouse gas emission. This paper presents the con-cept of ideal energy-saving building envelope, which is used to guide the building envelope material selection and thermal performance design. This paper reviews some available researches on phase change building material and phase change energy storage building envelope. At last, this paper pre-sents some current problems needed further research.

相变储能材料在建筑工程建设中的应用

相变储能材料能与建筑材料复合实现节能效果。合理开发利用相变储能材料是优化居住空间、推动建筑领域绿色发展的有效途径。本文综述了相变储能材料的概念、分类及应用价值,介绍了相变储能材料在建筑中的节能原理,并具体阐释了相变储能材料的应用领域。

基于DesignBuilder的相变保温墙体节能特性及经济性分析

运用DesignBuilder软件对沈阳地区某办公楼夏冬两季的室内平均温度及夏季空调和冬季采暖的能耗进行模拟,对比研究在不同基层外墙(混凝土墙体和砖墙体)保温材料中加入相变材料的作用,并对相变保温建筑进行了经济性分析。结果表明,在保温材料中加入相变材料能有效控制室内温度,增加室内舒适度,同时也能明显降低夏季空调和冬季采暖的耗电量。经济性分析表明,虽然加入相变材料后会增加建筑造价,但随着使用年限的增加这种成本会得到回收,在不超过建筑物使用年限的情况下使用年限越长收益越大。

Na_(2)CO_(3)·10H_(2)O-Na_(2)HPO_(4)·12H_(2)O/SiO_(2)复合定形相变材料的制备及应用

以Na_(2)CO_(3)·10H_(2)O(SCD)、Na_(2)HPO_(4)·12H_(2)O(DHPD)为相变主体制备了共晶体系,通过绘制凝固点变化图与DSC测试共同确定在m(SCD)∶m(DHPD)=4∶6时形成共晶,FTIR和XRD结果显示,2种水合盐间没有发生化学反应,但其晶型结构发生改变。通过添加质量分数为2%的Na2SiO3·9H_(2)O作为成核剂降低体系的过冷度,且经历50次相变循环体系未出现相分离,相变焓值仅下降0.25%。进一步使用质量分数为25%的气相SiO_(2)作为支撑材料,采用浸渍法制备了相变前后形状稳定的共晶水合盐/SiO_(2)定形相变材料(SSPCM)。所得SSPCM的相变温度为24.08℃,相变焓值为146.6J/g,过冷度为0.55℃,热导率为0.4571W/(m·K)。同保温泡沫相比,其可将模拟房内部中心温度的升温时间延长了1.81倍,降温时间延长了0.39倍。

相变材料应用于建筑节能的研究状况与趋势

为了系统地分析相变材料应用于建筑节能领域的发展态势,以中国知网期刊和Web of Science核心合集引文数据库收录的2001-2021年“相变材料”及“建筑节能”为主题的文献为数据源,利用信息可视化软件Cite Space分析了相变材料应用于建筑节能的研究现状、研究热点、研究主题和发展趋势,总结并绘制了该领域知识路线图。相变材料应用建筑节能领域可总结为4个主要方面:相变材料传热性能的研究、提高相变材料热导率技术、相变材料应用技术。未来研究重点将是通过添加高导热率材料来提升和改善相变材料的传热性能及其他性能。综合分析表明,近年来相变材料在建筑节能中的应用研究呈现逐年上升趋势,研究热点主要集中于制备及方法研究、储热装置的性能研究和应用研究,其未来研究方向将更加注重降低建筑能耗,以及相变建筑构件的耐久性和稳定性。

Experimental and Numerical Analysis of a PCM-Integrated Roof for Higher Thermal Performance of Buildings

Phase change materials(PCMs) designate materials able to store latent heat.PCMs change state from solid to liquid over a defined temperature range.This process is reversible and can be used for thermo-technical purposes.The present paper aims to study the thermal performance of an inorganic eutectic PCM integrated into the rooftop slab of a test room and analyze its potential for building thermal management.The experiment is conducted in two test rooms in Antofagasta(Chile) during summer,fall,and winter.The PCM is integrated into the rooftop of the first test room,while the roof panel of the second room is a sealed air cavity.The work introduces a numerical model,which is built using the finite difference method and used to simulate the rooms' thermal behavior.Several thermal simulations of the PCM room are performed for other Chilean locations to evaluate and compare the capability of the PCM panel to store latent heat thermal energy in different climates.Results show that the indoor temperature of the PCM room in Antofagasta varies only 21.1℃±10.6℃,while the one of the air-panel room varies 28.3℃±18.5℃.Under the experiment's conditions,the PCM room's indoor temperature observes smoother diurnal fluctuations,with lower maximum and higher minimum indoor temperatures than that of the air-panel room.Thermal simulations in other cities show that the PCM panel has a better thermal performance during winter,as it helps to maintain or increase the room temperature by some degrees to reach comfort temperatures.This demonstrates that the implementation of such PCM in the building envelope can effectively reduce space heating and cooling needs,and improve indoor thermal comfort in different climates of Chile.

基于无机水合盐相变材料的相变蓄冷新风机实验研究

新风系统提高了空气质量,但其温度波动增加了空调系统的负担。相变材料能够利用低品位冷源进行蓄冷,控制新风温度波动。本研究将性能优异的无机复合相变材料与新风机耦合以搭建相变新风机,探究了18、20、22℃的冷水工况下相变新风机的蓄冷性能,发现夜间高温冷源能够满足蓄冷要求,利用相变储热的方式转移用电高峰;此外,相变蓄冷模块能够将28℃的新风温度降低2.4~3℃;基于峰谷电价政策,该装置充分利用电价差可节约54.8%的电力成本。

膨胀蛭石基复合相变储热材料的制备及性能研究

文章以癸酸-棕榈酸(CA-PA)二元共晶物作为相变材料,膨胀蛭石(EVM)作为支撑材料,采用真空浸渍法制备癸酸-棕榈酸/膨胀蛭石复合相变储热材料(CA-PA/EVM)。通过FT-IR,DSC,TG,热循环等测试方法对癸酸-棕榈酸/膨胀蛭石复合相变储热材料的化学兼容性、储热性能、热稳定性及可靠性进行系统研究。结果表明:膨胀蛭石通过物理作用吸附癸酸-棕榈酸二元共晶物至其层状孔隙结构,且二者化学兼容性良好;癸酸-棕榈酸/膨胀蛭石复合相变储热材料的融化和凝固相变温度分别23.61,20.41℃,熔化和凝固相变潜热分别为67.22,64.87 J/g;膨胀蛭石中癸酸-棕榈酸的封装量可达52.22%,在工作温度下具有良好的热稳定性;癸酸-棕榈酸/膨胀蛭石复合相变储热材料经过100次热循环后仍保持良好的热可靠性,在建筑节能领域具有广阔的应用前景。

建筑用相变蓄能材料研究现状与发展趋势

利用相变材料对清洁能源进行储存和使用已成为建筑节能设计的重要措施之一。对建筑用相变材料的研究和应用现状进行了总结概况,介绍了对建筑用相变材料的要求、常见种类、封装方法和选用原则,总结了相变材料与传统建筑材料复合、与建筑设施相结合两种主要应用形式,并通过案例阐述了已有的典型应用方法,讨论了相变材料在建筑中的应用面临的挑战和应用前景。为相变材料在建筑中的应用和研究提供参考。

相变建筑围护结构材料对室内供暖设计的影响

建筑围护结构相变材料有效提高室内保温性能,研究其最佳制备方式及对供暖的影响可为工程人员提供理论依据。优选了建筑维护结构材料的配比、载体吸附工艺、封装方式,分析了材料调温性能及隔热性能对室内供暖设计的影响。结果表明,月桂酸、硬脂酸和棕榈酸的质量配比为65.9:10.5:23.6。随着吸附温度和吸附时间的升高,可膨胀石墨的容留率先升高后降低,最佳吸附温度为55℃,最佳吸附时间为50min,推荐真石漆乳液-水泥粉胶粘封装。相比普通水泥砂浆,相变水泥砂浆在受热后中心最高温度明显降低,相变水泥砂浆墙体内侧温度明显更低,达到最高温度所需的时间延长,良好的调温能力和隔热性能有效改善了建筑围护结构的蓄热量和传热量,供暖系统补充供热量降低。

基于室内热湿环境的相变材料优化设计与性能分析

相变材料在被动式建筑中的应用,既能降低室内采暖能耗需求,还能优化室内热湿环境状况。对此,选择癸酸、月桂酸相变材料,以膨胀珍珠岩为载体材料,制备了复合相变材料,并对其抗压强度、粘接强度、导热系数、蓄热系数等指标进行测试分析。结果表明,随着复合相变材料掺量的增加,建筑砂浆的力学性能有所降低,热工性能逐渐增强;当添加量达到30%时,抗压强度降低53.9%,粘接强度降低53.0%,导热系数降低22.0%,蓄热系数提升5.1%。

相变储热材料应用于建筑围护结构的研究现状和发展趋势

相变蓄热技术在建筑节能领域应用广泛,回顾了近年来相变储热材料应用于建筑围护结构的研究进展,介绍了目前围护结构用相变材料(PCMs)的筛选和优化方向,系统地阐述了PCMs应用于建筑围护结构的研究现状,分析了影响不同形式相变围护结构性能的因素,最后指出无机PCMs及其复合材料在围护结构中的应用会成为研究者未来关注的热点;建立相变围护结构的热学、力学性能综合评价指标,有利于PCMs与建筑材料的混合应用;同时掺入PCMs导致建筑材料力学性能降低的问题也有待进一步研究,旨在为相变围护结构在我国建筑节能领域的发展和应用提供参考。