共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
Phase change materials (PCMs) contributed to building energy‐saving and thermal comfort through increasing the thermal capacity of building envelopes. In this study, a phase change material composite was developed by using the PCMs mixture of capric acid (CA) and lauric acid (LA) as the primary phase change energy storage agent and using the solid waste fly ash as a carrier material. The results showed that for Guangdong, the ideal PCMs mixture should have a transition temperature of 25.5oC, which could be obtained by using a mass ratio of CA/LA of 4:6. Then, experiment results also indicate that the optimum adsorption ratio of 2:1 (FA/PCMs) was detected for the synthesis of this FA/PCMs composite, which has the latent heat of 45.38 J/g and exists excellent thermal reliability. Moreover, simulation results by using EnergyPlus show that the proposed composite has a good building energy‐saving effect. 相似文献
4.
5.
Heat transfer behaviour of thermal energy storage components using composite phase change materials 下载免费PDF全文
对基于复合相变材料储热单元的储热性能进行了研究。建立了复合材料和储热单元体内部的二维传热模型,考察了复合材料物性和结构尺寸及传热流体操作条件(流体流速)对单元体储热性能的影响,对比了两种不同结构单元体的储热性能,并搭建实验平台进行了实验对比研究。对比结果表明,模型结果与实验结果趋于一致,验证了模型的准确性。复合材料物性和结构尺寸及传热流体操作条件对单元体储热性能有较大的影响。相比较单管储热单元体,同心管储热单元体有着更优的储热特性,在相同的操作条件下,同心管储热单元体的储热、放热时间较单管储热单元体分别减少10%和15%。 相似文献
6.
7.
In the present study, encapsulated phase change materials (PCMs) were used for the storage of thermal energy. Both experiments and simulation were performed to evaluate the characteristics of encapsulated PCMs. Tests were conducted in a packed bed to determine the performance of the encapsulated PCM. In the preparation of encapsulated PCMs, the coacervation technique was used. The performance of the encapsulated PCM was evaluated in terms of encapsulation ratio, hydrophilicity, and energy storage capacity. The experiments were designed, based on surface response method, to optimize the processing conditions. It was found that a higher coating to paraffin ratio led to a higher paraffin encapsulation ratio. The hydrophilicity value of encapsulated paraffin depended mainly on the ratio of paraffin to coating. The higher the ratio, the lower was its product hydrophilicity. When the paraffin to coating ratio was constant, the higher concentration of HCHO led to a lower hydrophilicity of the product. The encapsulated paraffin has shown large energy storage and release capacity (20–90 J g?1) during its phase changes depending on different ratios of paraffin to coating. Thermal cyclic test showed that encapsulated paraffin kept its geometrical profile and energy storage capacity even after 1000 cycles of operation. In the experiments and simulation of fluid heating process in encapsulated PCM charged packed bed, results showed that Eulerian granular multiphase model in FLUENT 4.47 is suitable for simulation of such a system. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
8.
相变储能墙体面临着相变温度不适宜、储能能力低、构建形式多但缺乏性能对比分析等问题。以相变砂浆、相变板墙体为对象,对其性能进行优化和对比研究。采用固、液石蜡、高密度聚乙稀(HDPE)按比例熔融混合制备出相变温度约为34.000℃的定形相变材料,该材料无泄漏、形状稳定,潜热为现有文献的2.00倍多。基于该材料制备出相变砂浆、相变板材,并构建两类相变-混凝土墙体结构,研究在相同边界条件和初始条件下两者的传热特性及节能效果。结果表明,以普通砂浆墙体为对照,相变砂浆、定形相变板可将内壁面最高温降低0.730、1.760℃,定形相变板保温隔热性能最优。定形相变板可将空调热负荷降低21.9%,高于相变砂浆;但其原料成本为普通砂浆的3.38倍;成本增幅较相变砂浆高出32.8%,而成本回收周期低33.3%。 相似文献
9.
10.
To make better use of solar energy, lauric acid/expanded graphite (LA/EG) composite phase change materials (PCMs) were synthesized to collect and store solar energy as latent heat thermal energy. The results of thermal characteristics show that when the mass fraction of EG is 5%, 10%, and 15%, the latent heat of LA/EG is 164.5, 156.9, and 148.0 J/g, and the thermal conductivity is 2.73, 7.98, and 10.54 W/(m·K). Leakage test shows that LA/EG PCMs with EG mass fraction of 10% and 15% are form stable after phase change. One thousand thermal cycles prove good thermal reliability of LA/EG. TG analysis indicates LA/EG PCMs have good thermal stability within operating temperature range. The Ultraviolet-visible spectra reveal that the absorbance of LA/EG composite PCMs would increase as the mass fraction of EG increases. Photothermal conversion experiment results indicate that the photothermal conversion efficiency of LA/EG composite PCMs increases as the mass fraction of EG increases, and the efficiency can reach 95% when the mass fraction of EG is 15%. Moreover, it was also found that the process of photothermal conversion can be accelerated with stronger illumination intensity or smaller heat transfer size. All the results show that the prepared LA/EG PCMs can convert solar energy into thermal energy and store it in the form of latent heat at the same time, which indicates it has promising prospect in the application of solar energy conversion and storage. 相似文献
11.
In hot climate, phase change material (PCM) can be incorporated into building envelopes to reduce heat gain through the building envelopes and therefore reduce its cooling demand. In this study, the energy performance of building envelopes integrated with PCM has been explored using a popular dynamic building performance simulation package, EnergyPlus, and the energy saving mechanism of PCM was investigated. The simulation results reflected that PCM could effectively help to reduce the building's annual energy consumption by 20.9% for Guangzhou, China. In addition, for the Guangzhou city, 27°C transition temperature, smaller thermal conductivity of roof, and higher amount of PCM can all help to improve the building's energy performance. Additionally, it is suggested that in real building development/retrofit projects, the selection of PCM needs to be based on both their thermal properties and the local climatic conditions of the building. 相似文献
12.
Karina Fullenkamp Macarena Montané Gustavo Cáceres Gerardo Araya-Letelier 《国际可持续能源杂志》2019,38(6):561-582
In order to improve the thermal efficiency of building thermal energy storage (TES) systems, the feasibility of using encapsulated phase change materials (EPCMs) as heat storage media is analysed in this work. Specifically, the finite element method is used to perform thermal behaviour analyses of several EPCMs. These analyses include technical and economic assessments in order to identify the best combination of PCM and shell material, using as main parameters: thermal energy storage, heat transfer rate, materials cost, among others. The results show that EPCMs composed by Na2SO4·6H2O as PCM and covered by stainless steel highlight as TES materials. 相似文献
13.
相变材料作为建筑领域重要的保温材料,具有很大的发展潜力.主要综述了相变材料的分类,制备过程,相变保温建筑材料的研究进展,主要应用技术及存在的问题等.相变材料主要包括有机相变材料,无机相变材料和复合相变材料3类.利用物理吸附,微胶囊或高分子包覆封装技术将相变材料封装定形,然后通过一定的复合工艺可将其制成不同的相变保温建筑制品应用于建筑领域,如相变石膏板,相变混凝土,相变砂浆等,并分析了相变材料作为建筑材料的不足. 相似文献
14.
总结近年来国内外相变储能材料的研究状况,包括相变储能材料的制备、传热性能、相变过程数值模拟和应用等,并对复合相变储能材料的传热性能研究方法的前景作了展望。 相似文献
15.
Both cool roof and phase change thermal storage are promising technologies in decreasing building energy consumption. Combining these two technologies is likely to further enhance the thermal comfort of the building as well as reduce air condition loads. In this paper, the cooling performance and energy-saving effects of four types of roof (normal roof, phase change material [PCM] roof, cool roof, and cool PCM roof [cool roof coupled with PCM]) were investigated under a simulated sunlight. Experimental results indicate that compared with normal roof, the other three roofs are able to narrow the indoor temperature fluctuation and decrease the heat flow entering into the room. Among them, cool PCM roof gave the best energy-saving effect that can lower the indoor temperature and heat entering into rooms by 6.6°C and 52.9%, respectively. Besides, the PCM location, PCM thickness, and insulation thickness exerted great impacts on the cooling performance of the roof. Placing the PCM on the internal layer beneath the extruded polystyrene (XPS) insulation board can make the indoor temperature 1.2°C lower than that on the middle layer. Although thicker PCM panels or insulation boards can provide a better thermal insulation, 5 mm in PCM thickness and 20 mm in insulation thickness are enough to guarantee the indoor temperature of cool PCM roof system at a comfortable range (22°C-28°C) for a whole day. These findings will give guidance in designing buildings with a light and compact roof structure to decrease energy consumption and improve comfort level. 相似文献
16.
基于Ansys软件建立数学模型,计算分析不同厚度的混凝土分别与不同厚度定形相变材料组成的相变墙体的传热特性和节能效果。计算结果表明,相对于两种不同厚度混凝土墙体,增加定形相变材料起到了很好的节能效果;定形相变材料的最优厚度需要从各方面综合考虑确定;随着定形相变材料的厚度的增加,墙体内表面温度波动幅度近似呈线性减小。 相似文献
17.
In this work, stearic acid/carbon nanotubes composite phase change materials (SA/CNTs composite PCMs) were fabricated by ball milling for the first time to enhance the heat conduction of SA and prevent the delamination of SA and CNTs components. The results of suspension stability study conducted using a gravity sedimentation method showed that polyvinylpyrrolidone (PVP) used as dispersant has the best effect on the stability of composite PCMs. Then, the thermal cycling test further proved the stability of prepared composite. The SEM and FT‐IR results revealed that ball milling led to the formation of highly homogeneous composites. The thermal properties of the fabricated SA/CNTs composites with CNTs contents of 2, 6, and 10 wt.% characterized by differential scanning calorimetry (DSC) demonstrated that their phase change temperatures varied slightly while the latent heat decreased with the increased CNTs content. Furthermore, the thermal conductivity of the SA/CNTs composites were greater than that of pure SA by 61.5%, 92.3%, and 119.2%, respectively. The addition of CNTs also increased the thermal release rates of the prepared PCMs and decreased their storage rates. Therefore, the produced materials can be potentially used in thermal management. 相似文献
18.
Recent progress in diatomite based composite phase change materials for thermal energy storage 下载免费PDF全文
硅藻土是一种含量丰富的非金属矿,具有较高的孔隙率,良好的表面结构和热物理性能,因而可作为复合储热材料的载体.本文综述了复合储热材料的种类和制备工艺,并介绍了硅藻土的结构,性能和以硅藻土为载体的复合相变储热材料的研究及应用现状. 相似文献
19.
Junying Hou Yaya Wang Jingchun Liu Jianguo Zhao Sifang Long Jianjun Hao 《国际能源研究杂志》2020,44(3):1909-1919
A composite phase change material (PCM) of copper-doped polyethylene glycol (PEG) 2000 impregnated urchin-like porous titanium dioxide (TiO2) microspheres (PEG/TiO2) was successfully synthesised. The urchin-like porous TiO2 structures contain hollow cavities that can provide a high PEG loading capacity of up to 80 wt%. Copper nanoparticles were uniformly dispersed on the outer and inner surfaces of the 0.8PEG/TiO2 as additives to enhance the thermal conductivity of the composite PCM. The latent heat of the Cu/PEG/TiO2 porous composite PCM reached 133.8 J/g, and the thermal conductivity was 0.58 W/(mK), which was 152.2% higher than that of TiO2 and 38.1% higher than 0.8PEG/TiO2. Moreover, the Cu/PEG/TiO2 porous composite PCM has excellent thermal stability and reliability. 相似文献