采用定形相变材料墙体节能效果分析

基于Ansys软件建立数学模型,计算分析不同厚度、不同结构和布局的定形相变材料与混凝土组成墙体的节能效果。结果表明,定形相变材料越厚,墙体内表面温度随外界温度变化幅度越小,能够有效降低室内空调设备能耗;定形相变材料厚度一定时,不同的定形相变材料结构和布局对墙体内表面温度的波动影响较小,在节能降耗上差别不大。     

相变墙体在建筑中的应用研究

利用相变储能建筑材料,可以减小室内温度波动,提高热舒适度,并在一定程度上降低了建筑采暖空调能耗,提高了能源利用效率。本文应用ENERGYPLUS软件对采用相变材料作为墙体的某交通建筑的热舒适性进行数值模拟。研究在不同地区交通建筑墙体和柱子中加入相变材料后,对室内热舒适性的影响。并通过改变相变墙体层的结构、厚度和相变温度,分析不同的参数值对于室内能耗的影响。通过分析和比较,得出如何在不同地区的交通建筑中合理有效的利用相变材料,以促进建筑节能和节资。     

一种新型双层定型相变墙体节能效果分析

目前常见的单层定型相变材料,在室内或者室外使用往往只能在夏季或冬季发挥作用,为改善全年室内热环境,降低全年建筑运行能耗,且减少墙体改装面积,本项目提出一种新型的双层定型相变墙体,具体做法为在建筑物外墙内外表面均添加定型相变材料板,外层相变板具有较高的相变温度,在夏季发挥作用,内层相变板具有较低的相变温度,在冬季发挥作用。本文中的双层定型相变墙板用于建筑南外墙,该研究主要分析了相变材料厚度、相变温度对建筑运行能耗和建筑室内热环境的影响,最后根据节能率性及经济性因素得出了相变墙板的推荐使用厚度及其对应的相变温度,为该结构在建筑节能中的应用提供技术支持。     

轻质建筑中相变蓄能石膏板热性能研究

现代轻质建筑由于热惯性较小,室内温度昼夜波动较大。相变蓄能具有温度变化小、蓄能密度大的特点。将相变材料（PCM）掺入轻质建材中,制成相变蓄能建筑构件,可以有效增加建筑围护结构热惯性,提高室内热舒适度,节约采暖空调能耗。本文研究了相变蓄能石膏板在北京地区轻质建筑中的冬季使用效果,从相变温度、相变材料含量和相变石膏板厚度三个方面对相变蓄能石膏板的使用进行了优化,并比较了普通石膏板和混凝土隔墙的使用效果。研究表明相变蓄能石膏板能有效抑制室内温度波动,提高室内热舒适度。     

北非地区大空间相变屋面联合夜间通风节能策略

博物馆作为大空间公共建筑,因其空间体积大、人流量大、室内环境要求高的特征导致空调能耗过高,节能减排潜力巨大。在北非地区,夏季气候干热、太阳辐射高、气温日较差大的特点,为相变屋面联合夜间通风的节能技术提供应用条件。将相变屋面联合夜间通风技术应用于大空间博物馆建筑,建立考虑温度分层的建筑能耗仿真模型,研究了不同相变因素和通风参数对空调能耗的影响。结果表明,在热带沙漠气候下,当相变层厚度小于15 mm时,宜采用高相变温度的PCM(RT35HC);当相变层厚度超过15 mm时,宜采用低相变温度的PCM(RT27),可以保证相变材料的完整相变循环,随着厚度的增加,其节能率也逐渐增加;通风时间段取1:00-8:00,换气次数取9次/h时节能效果最佳。在地中海气候下,当相变层厚度为5 mm时,宜采用高相变温度的PCM(RT31);当相变层厚度超过5 mm时,宜采用低相变温度的PCM(RT27),但设计厚度超过20 mm之后节能率增加不再显著;通风时间段取1:00-8:00,换气次数取6次/h时节能效果最佳。研究成果为北非地区两种典型气候下大空间建筑应用相变屋面联合夜间通风技术提供节能设计策略。     

夏热冬冷地区外墙保温特性对公共建筑空调能耗的影响

以上海地区某模型建筑为研究对象,利用能耗模拟软件计算在不同内热源强度、不同冬夏空调室内设定温度条件下,建筑空调能耗随外墙传热系数Kw的变化特性。软件计算结果表明,存在使建筑全年空调能耗最小的外墙传热系数Kw的值,在此情况下,进一步减小外墙传热系数Kw,会造成建筑全年空调能耗增大,出现外墙过度保温的现象。建筑物外墙保温性能的确定应综合考虑建筑物的内热源强度和冬夏空调室内设定温度。     

基于Ansys的相变墙体传热特性计算分析

基于Ansys软件建立数学模型,计算分析了不同厚度相变储能材料、不同相变墙体结构的传热特性.计算结果表明,相变储能材料越厚,相变墙体内层与室内环境界面温度随外界温度变化幅度越小,能够有效降低室内空调设备的能耗;相变储能材料厚度一定时,不同结构的相变墙体从节能降耗角度差别不大:相变储能材料位于墙体中心位置时节能效果较好.     

相变墙体与夜间通风改善轻质建筑室内热环境

将自制复合有机相变材料,与EPS保温材料相粘和,制作成轻质建筑用墙体材料,结合夜间通风技术,在重庆地区进行了含相变材料层和不含相变材料层轻质房间的室内热环境对比实验,以分析相变材料用量、相变温度及相变墙体结构等因素对相变墙体的蓄热、放热性能及对室内热环境的影响。实验结果表明：相变材料应用于轻质房间,能显著增强围护结构的热惰性,提高室内的热舒适性,采取夜间通风技术,可以有效地将日间蓄积的热量散至室外;含相变墙体材料房间与普通房间相比较,室内温度最高降低11℃左右,节能效果显著;室内平均温度符合《野营住房空间与环境参数限值》(GJB 4306 2002)中6.2条规定的3级要求;相变材料用量及相变温度对室内温度的控制效果较为明显,采用不同的相变温度,并将相变墙体房间相变材料用量提高1倍,两轻质房间室内温差最大值从3℃增大至11℃左右;进行相变墙体结构设计时,采取不同相变温度的材料搭配使用可以大幅提高其使用效果。     

基于自然通风和蓄热耦合作用下的节能分析

本文采用CFD软件对西安地区某一居住建筑室内流场进行数值模拟,通过模拟结果优化室内空间布局从而增大自然通风量。利用DeST-h软件对优化前后的全年累计冷/热负荷进行动态模拟,分析通风量对能耗的影响;在通风次数一定的情况下,模拟分析复合墙体的材料和结构类型对能耗的影响。结果表明,在利用自然通风和蓄热耦合原理降低建筑能耗的过程中,增大通风量的节能效果优于改变墙体的材料;外保温的节能效果优于内保温;在优化墙体的材料方面,重型墙体结构的节能效果优于轻型墙体结构,其中,内隔墙材料的优化对节能效果最为显著。     

某工程实训中心不同空调冷热源能耗模拟分析

本文以某实训中心数控机床大空间建筑为对象,运用动态能耗模拟软件分析了全年逐时动态空调负荷特性,并模拟了水冷冷水机组加电锅炉、空气源热泵机组、地源热泵机组三种常见的空调冷热源系统的全年能耗,模拟结果显示,方案二较方案一减少7.8％,方案三较方案一减少19.4％,从节能与舒适性角度分析表明方案二和方案三组合使用可以达到较好的效果.     

Novel concept of composite phase change material wall system for year-round thermal energy savings

A new type of composite wall system incorporating phase change materials (PCMs) was proposed and its potential for air conditioning/heating energy savings in continental temperate climate was evaluated. The novelty of the wall system consists of the fact that two PCM wallboards, impregnated with different PCMs are used. The structure of the new wall system is that of a three-layer sandwich-type insulating panel with outer layers consisting of PCM wallboards and middle layer conventional thermal insulation. The PCM wallboard layers have different functions: the external layer has a higher value of the PCM melting point and it is active during hot season and the internal layer with a PCM melting point near set point temperature for heating is active during cold season. A year-round simulation of a room built using the new wall system was carried out and the effect of PCM presence into the structure of the wall system was assessed. It was found that the new wall system contributes to annual energy savings and reduces the peak value of the cooling/heating loads. The melting point values for the two PCMs resulting in the highest value of the energy savings were identified.     

Energy savings potential by integrating Phase Change Material into hollow bricks: The case of Moroccan buildings

The building sector in Morocco represents 25% of the country’s total energy consumption. The poor thermal performance of the building envelopes is one of the principal reasons for this consumption rate. In this study, the efficiency of integrating Phase Change Materials (PCM) into hollow bricks used in three typical housing types in the six climate zones in Morocco is investigated. The numerical model is based on the heat transfer equation and the apparent heat capacity formulation to model the phase change. A heat flux analysis is performed at the internal surface of the wall, giving a good understanding of the thermal behavior of hollow bricks with PCMs compared with hollow bricks with air. The results show that the heat flux density at the internal face of the wall is constant when the PCM is partially solid/liquid, and follows the outdoor conditions when the PCM is fully solid or fully liquid. Irrespective of the climate zone, the PCM with a 32 °C median melting temperature reduces the heat flux peak value in the hotel housing while the PCM with a 37 °C median melting temperature is better for the individual and collective housing. On the other hand, the PCM with a 27 °C median melting temperature is able to save up to 25% and 40% of energy consumption in the Saharan climate and oceanic climate, respectively.     

相变通风屋顶的供热节能优化设计研究

提出太阳能相变屋顶系统(主要由太阳能空气集热系统、相变通风屋顶组成),将两种相变材料(PCM1、PCM2,PCM1用于供冷期蓄冷,相变温度在35℃左右。PCM2用于供暖期蓄热,相变温度在18℃左右)及风道(预制在钢筋混凝土板内,供冷期利用夜间低温空气冷却屋顶与PCM1,供暖期利用太阳能空气集热器出口热空气加热屋顶与PCM2)预制在屋顶内,形成相变通风屋顶(由上至下的基本结构为保护层、防水层、找坡层、保温层、找平层、PCM1、钢筋混凝土板),实现供冷期夜间蓄冷日间吸热、供暖期日间蓄热夜间放热。针对供暖工况,采用模拟方法,结合评价指标,对相变通风屋顶中相变材料(由于供暖工况PCM1不发生相变,因此研究对象为相变材料PCM2)的相变温度、结构(即相变材料位置)、相变材料厚度进行优化选取。A型相变通风屋顶将PCM2设置在PCM1与钢筋混凝土板之间,B型相变通风屋顶将PCM2设置在钢筋混凝土板下面,C型相变通风屋顶将PCM2设置在预制风道外圈。PCM2的最佳相变温度为18~20℃,最优结构为B型相变通风屋顶,PCM2最佳厚度为30 mm。与无相变通风屋顶(将B型相变通风屋顶中的30 mm厚PCM2相变材料替换成相同厚度的水泥砂浆,保留预制风道,其他各层材料及厚度均保持不变)相比,最佳相变通风屋顶(PCM2相变温度为18~20℃、厚度为30 mm的B型相变通风屋顶)的各项评价指标均更优。     

Thermal response of brick wall filled with phase change materials (PCM) under fluctuating outdoor temperatures

Based on the enthalpy-porosity technique, a model of thermal conduction accompanied with solidification and melting processes is developed and numerically analyzed to investigate the thermal response of the brick wall filled with phase change materials (PCM). The thermal response, which is represented by indoor wall surface temperature response, of brick wall filled with PCM is evaluated and compared with that of solid brick wall. The effects of PCM filling and its filling amount on thermal response of brick wall are investigated and discussed. It is indicated that, compared to the common solid brick wall, the thermal storage of brick wall filled with PCM is elevated by the alternate process of melting and solidification under fluctuating outdoor temperatures. The use of PCM in the brick walls is beneficial for the thermal insulation, temperature hysteresis and thermal comfort for occupancy. In addition, with the increasing filling amount of PCM, the fluctuation of indoor wall surface temperature is significantly smoothed. Correspondingly, the hysteresis in response to the outdoor temperature fluctuation is enhanced. Moreover, the present model is verified by experimental data available in the literature.     

Positioning of an isothermal heat storage layer in a building wall exposed to the external environment

The paper presents an idea for the enhancement of a building's thermal insulation component by adding into the structure a thin layer of a phase-change material (PCM). The proposed solution can be dedicated, for example, to an external partition of lightweight construction. The capacity for latent heat storage allowed it to stabilize the temperature inside the insulation layer in a daily cycle and to minimize the temperature difference between the internal and external surfaces. In this paper, different positions of a PCM layer in the thermal insulation of an external wall were analysed. The main goal of this work was to find the best position of the PCM layer, taking into account the indoor temperature and the meteorological conditions. The authors propose two parameters: the amount of stored energy and the dynamism of the charging/discharging processes. Taking into account large temperature fluctuations on the external surface during summer and winter, it was concluded that, for this specific case, the most appropriate solution would be an external position of the PCM with a melting temperature of 20°C.     

Experimental investigation of PCM cold storage

This article presents an experimental analysis of cooling buildings using nighttime cold accumulation in a phase change material (PCM), otherwise known as the “free-cooling principle”. Studies of the ceiling and floor free-cooling principle, as well as passive cooling, are presented. The free-cooling principle is explained and some of the types of PCMs suitable for summer cooling are listed. An experiment was conducted using paraffin with a melting point of 22 °C as the PCM to store cold during the nighttime and to cool hot air during the daytime in summer. Air temperatures and heat fluxes as a function of time are presented for different air velocities and inlet temperatures.     

Development and testing of PCM doped cool colored coatings to mitigate urban heat island and cool buildings

In this study the performance of organic PCMs used as latent heat storage materials, when incorporated in coatings for buildings and urban fabric, is investigated. Thirty six coatings of six colors containing different quantities of PCMs in different melting points were produced. Accordingly, infrared reflective (cool) and common coatings with the same binder system and of the same color were prepared for a comparative thermal evaluation. The samples were divided in six groups of different color and eight samples each: three PCM coatings of different melting temperatures (18 °C, 24 °C, 28 °C) each one of two different PCM concentrations (20% w/w, 30% w/w), an infrared reflective and a common coating of matching color. Surface temperature of the samples was recorded at a 24 h basis during August 2008. The results demonstrate that all PCM coatings present lower surface temperatures than infrared reflective and common coatings. Analysis of the daily temperature differences showed that peak temperature differences occur between PCM and common or cool coatings from 7 am to 10 am. Investigating the temperature gradient revealed that for this time period the values for PCM coatings are lower compared to infrared reflective and common. From 10 am to 12 pm, temperature gradients for all coatings have similar values. Thus coatings containing PCMs store heat in a latent form maintaining constant surface temperatures and discharge with time delay. PCM doped cool colored coatings have the potential to enhance thermal inertia and achieve important energy savings in buildings maintaining a thermally comfortable indoor environment, while fighting urban heat island when applied on external surfaces.     

Thermal testing and numerical simulation of a prototype cell using light wallboards coupling vacuum isolation panels and phase change material

Light envelopes are more and more frequently used in modern buildings but they do not present sufficient thermal inertia. A solution to increase this inertia is to incorporate a phase change material (PCM) in this envelope. This paper presents the performance of a test-cell with a new structure of light wallboards containing PCMs submitted to climatic variation and a comparison is made with a test-cell without PCMs. To improve the wallboard efficiency a vacuum insulation panel (VIP) was associated to the PCM panel. This new structure allows the apparent heat capacity of the building to be increased, the solar energy transmitted by windows to be stored without raising the indoor cell temperature, and the thickness of the wallboard to be decreased compared with that of traditional wallboards. An experimental study was carried out by measuring temperature and heat fluxes on and through the wallboards. The indoor temperature, which has a special importance for occupants, was also measured.A numerical simulation with the TRNSYS software was carried out in adding a new module representing the new wallboard. It showed a good agreement with experimental results. This new tool will allow users to simulate the thermal behaviour of buildings having walls with PCMs.     

Correlation between the local climate and the free-cooling potential of latent heat storage

The natural cooling of energy-efficient buildings using latent heat thermal energy storage (LHTES) that is integrated into the building services makes possible energy savings and improved thermal comfort. In this article, studies of the free-cooling potential for different climatic locations are presented. Six cities from around Europe with a wide range of climatic conditions were selected. The size of the LHTES was optimized on the basis of the calculated cooling degree-hours. First, we analysed the influence of the width of the phase change temperature range and determined the optimal melting temperature of the phase change material (PCM). Then, the optimal LHTES was selected, based on the ratio of the mass of the PCM and the volume flow rate of air ventilating the building. We found that the optimum PCM has a melting temperature that is approximately equal to the average ambient air temperature in the hottest month, and that the free-cooling potential is proportional to the average daily amplitude of the ambient air's temperature swings. For all the analysed climatic conditions the PCM with a wider phase change temperature range (12 K) was found to be the most efficient. The optimal size of the LHTES for the free cooling of buildings is between 1 and 1.5 kg of PCM per m³/h of fresh ventilation air.     

相变储能建筑材料的发展

建筑墙板、天花板和顶板中掺入适当的相变材料(PcMs),能提高其表面因接受太阳光辐射而储蓄能量的能力,这样可以在一个较长的时间内,减少因空气流动造成的室内温度波动,维持室内温度接近到要求的温度,提高人体的舒适度。运用这种相变储能建材,可将电力供给峰期时的加热或制冷负荷转移到谷期,使用户降低使用费用。本文对建筑相变储能材料的研究进行了回顾,并讨论了PCMs的选择和封装所存在的问题。