共查询到18条相似文献,搜索用时 78 毫秒
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固-液相变潜热蓄热技术是一种极具前景的工业废热回收方式,通过管壳式换热器可利用相变材料(PCM)吸收工业废热加以储存再用于加热水,从而实现了工业废热的回收利用.对填充高导热多孔筛网的管壳式潜热蓄热单元(LHSU)建立了二维数学模型,并对填充与未填充筛网的蓄热容器一同进行了相变蓄热实验.实验结果表明,填充筛网能够有效改善PCM的传热性能;实验数据和计算值吻合的较好,证明了计算模型的有效性.利用计算模型,对3种PCM(石蜡P116、硬脂酸和软脂酸)蓄热系统进行了数值计算.结果表明,采用软脂酸的蓄热系统热性能最佳,能很好地满足供应生活热水的设计要求.研究结论对蓄热系统的设计和性能优化有一定的指导作用. 相似文献
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含相变材料的壁板的潜热蓄热试验 总被引:5,自引:0,他引:5
含相变材料的壁板具有潜热蓄热能力。本文研究安装含相变材料的壁板的房间做了蓄热试验,并将试验结果与安装普通壁板的主心间进行了比较。 相似文献
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为分析相变蓄热装置在充热和放热过程中的热性能,设计并搭建一套相变蓄热供热装置中试实验系统,研究主要运行参数对相变蓄热装置热性能的影响;在此基础上,结合项目案例,对相变蓄热供热系统经济性进行分析。结果表明:相变材料(Phase Change Material, PCM)凝固过程中的传热主要受相变介质内部导热控制;而在其熔化过程中自然对流对传热起重要控制作用;蓄热装置充热速率快于放热速率。提高传热流体流量有助于增强PCM中的热传递,缩短充/放热时间,但蓄热装置内PCM温度分布均匀性有所降低;为降低系统能耗,提高储放热效率,优先选用小流量进行充/放热。该相变蓄热供热项目的动态投资回收期为3.55年,具有良好的经济性。研究结果可对相变蓄热供热系统的设计及应用推广提供参考依据。 相似文献
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良导热、形状保持相变蓄热材料的制备及性能 总被引:43,自引:0,他引:43
将石蜡与一热塑弹性体SBS复合制备了在石蜡熔融状态下仍能保持形状稳定的复合相变蓄热材料,复合材料保持了石蜡的相变性,相变潜热可高达纯石蜡潜热的80%,在复合相变材料中加入膨胀石墨后,热传导性有了显著提高,其放热时间比纯石蜡缩短了61%。 相似文献
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M. El-Kotb A. El-Sharkawy N. M. El Chazly N. M. Khattab S. El-Deeb 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2013,35(12):1113-1126
A thermal energy storage medium must meet the requirements of a stable storage material with high heat capacity. Heat storage based on the sensible heating of media such as water, rock, and earth represents the first generation of solar energy storage subsystems and technology for their utilization is well developed. However, recently the heat storage based on the latent heat associated with a change in phase of a material offers many advantages over sensible heat storage. The most important characteristic of such a subsystem is its sufficient storage capacity. The PCM (phase change material) behavior is visualized by constructing an idealized model thermal capacitor subjected to simulated solar system environmental conditions which include thermal cycling utilizing the latent heat of paraffin for heating and cooling. The proposed model of the capacitor is of a flat plate geometry consisting of two panel compartments forming the body of the capacitor containing the paraffin, leaving at their inner surfaces a thin passage allowing the water flow. The whole structure is assumed to be insulated to minimize heat loss. Analysis solution is used to generate data about the temperature distribution, the melt thickness, and the heat stored in the PCM under two conditions of: (a) constant mass flow rate tests for various water inlet temperatures, and (b) constant water inlet temperature for various mass flow rates. A FORTRAN computer program is constructed to perform the analysis. It is found that water outlet temperature increases with time until it becomes nearly equal to the inlet temperature. Increasing the mass flow rate for a given inlet temperature, decreases the time required for outlet temperature to reach a given value. Increasing inlet temperature for a given mass flow rate gives a very rapid decrease in the time required for the outlet water temperature to reach a given value. Instantaneous rate of heat storage is determined from the inlet-to-exit temperature differential and measured flow rate. This rate is then integrated numerically to determine the cumulative total energy stored as a function of time. It is found that the instantaneous rate of heat storage decreases till reaching a nearly constant value. The total or cumulative heat storage as a function of time, showed a nearly linear trend in the mid-range time, and it increased with increasing inlet temperature. 相似文献
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为探究方腔内相变石蜡的储热性能,基于等效热容法和Boussinesq假设,建立相变石蜡融化储热计算模型,并针对加热方向及约束形式等因素对相变石蜡的储热性能的影响进行研究,并开展相变石蜡融化试验,验证计算模型的正确性。结果表明:相变石蜡融化储热过程是由热传导和自然对流传热综合决定的,其中自然对流传热在相变石蜡融化储热过程中起着极为显著的促进作用;不同加热方向下,相变石蜡表现出截然不同的融化储热效率,其中顶、底、侧边单独加热下的自然对流传热效应依次使储热效率提升了0.01,27.9和13.1倍,即底部热源的储热效率最高;在四面加热下,固相因无约束而下沉至底部,并抑制底部热壁面的自然对流传热效应,此时顶、底、侧热壁面的储热贡献率分别为17.3%,37.3%和22.7%;当固相运动被预埋热电偶等因素限制时,将形成钟型融化前缘,该形态包含了各热壁面单独加热下的融化储热特征,此时顶、底、侧热壁面的储热贡献率分别为19.2%,29.8%和25.5%。 相似文献
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The exhaust gas from an internal combustion engine carries away about 30% of the heat of combustion. The energy available in the exit stream of many energy conversion devices goes as waste. The major technical constraint that prevents successful implementation of waste heat recovery is due to intermittent and time mismatched demand for and availability of energy. The present work deals with the use of exergy as an efficient tool to measure the quantity and quality of energy extracted from a diesel engine and stored in a combined sensible and latent heat storage system. This analysis is utilized to identify the sources of losses in useful energy within the components of the system considered, and provides a more realistic and meaningful assessment than the conventional energy analysis. The energy and exergy balance for the overall system is quantified and illustrated using energy and exergy flow diagrams. In order to study the discharge process in a thermal storage system, an illustrative example with two different cases is considered and analyzed, to quantify the destruction of exergy associated with the discharging process. The need for promoting exergy analysis through policy decision in the context of energy and environment crisis is also emphasized. 相似文献
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The exhaust gas from an internal combustion engine carries away about 30% of the heat of combustion. The energy available in the exit stream of many energy conversion devices goes as waste, if not utilized properly. The major technical constraint that prevents successful implementation of waste heat recovery is due to its intermittent and time mismatched demand and availability of energy. In the present work, a shell and finned tube heat exchanger integrated with an IC engine setup to extract heat from the exhaust gas and a thermal energy storage tank used to store the excess energy available is investigated in detail. A combined sensible and latent heat storage system is designed, fabricated and tested for thermal energy storage using cylindrical phase change material (PCM) capsules. The performance of the engine with and without heat exchanger is evaluated. It is found that nearly 10–15% of fuel power is stored as heat in the combined storage system, which is available at reasonably higher temperature for suitable application. The performance parameters pertaining to the heat exchanger and the storage tank such as amount of heat recovered, heat lost, charging rate, charging efficiency and percentage energy saved are evaluated and reported in this paper. 相似文献
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Thermal performance of myristic acid as a phase change material for energy storage application 总被引:1,自引:0,他引:1
Thermal performance and phase change stability of myristic acid as a latent heat energy storage material has been studied experimentally. In the experimental study, the thermal performance and heat transfer characteristics of the myristic acid were tested and compared with other studies given in the literature. In the present study is included some parameters such as transition times, temperature range, and propagation of the solid–liquid interface as well as heat flow rate effect on the phase change stability of myristic acid as a phase change material (PCM). The experimental results showed that the melting stability of the PCM is better in the radial direction than the axial direction. The variety of the melting and solidification parameters of the PCM with the change of inlet water temperature is also studied. The results show that the better stability of the myristic acid was accomplished at low inlet water temperature compared with the obtained results at high inlet water temperature. We also observed that while the heat exchanger tube is in the horizontal position, the PCM has more effective and steady phase change characteristics than in the vertical position. The heat storage capacity of the container (PCM tube) is not as good as we expected in this study and the average heat storage efficiency (or heat exchanger effectiveness) is 54%. It means that 46% of the heat acrually lost somewhere. 相似文献
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The heat storage potential of ethylenediammonium ditetramethoxyborate, a white crystalline compound with a melting point of 82°C and a density of 0.86 g/cm3, has been examined. Experimental data give a value of 344 J/g for the heat of transition from solid to liquid. The potential of this compound as a heat storage material is discussed. 相似文献
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基于熔融浸渗法和黏结封装法,以多孔基作为基体材料,分别采用无机玻璃粉与熔盐作为相变材料开展实验,探究储热样本的最佳制备工艺流程。考察了复合相变蓄热体的显微结构及物相组成特征,分析了复合相变蓄热材料的质量损失率,并对蓄热体进行蓄热性能分析及高温抗压强度测试。实验结果表明,采用黏结封装法,以氯化钠作为相变材料,加盖圆柱形三角孔蜂窝陶瓷基体作为载体,设定6.5℃/min的升温速率,烧结温度至800℃,保温30 min,可制备蓄热性能较为优异的复合相变蓄热材料。复合相变蓄热材料的蓄热密度为445.5 kJ/kg,该蓄热体在800℃条件下高温抗压强度达到75.9 MPa,具有良好的蓄热性能和力学性能。 相似文献
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An experimental analysis is presented to establish the thermal performance of a latent heat thermal storage (LHTS) unit. Paraffin is used as the phase change material (PCM) on the shell side of the shell and tube‐type LHTS unit while water is used as the heat transfer fluid (HTF) flowing through the inner tube. The fluid inlet temperature and the mass flow rate of HTF are varied and the temperature distribution of paraffin in the shell side is measured along the radial and axial direction during melting and solidification process. The total melting time is established for different mass flow rates and fluid inlet temperature of HTF. The motion of the solid–liquid interface of the PCM with time along axial and radial direction of the test unit is critically evaluated. The experimental results indicate that the melting front moves from top to bottom along the axial direction while the solidification front moves only in the radial direction. The total melting time of PCM increases as the mass flow rate and inlet temperature of HTF decreases. A correlation is proposed for the dimensionless melting time in terms of Reynolds number and Stefan number of HTF. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21120 相似文献