两级填充床蓄热器式绝热压缩空气储能系统变工况特性研究

利用压缩机和透平的变工况模型及填充床蓄热器的非稳态模型,对两级填充床蓄热器式绝热压缩空气储能系统一次完整的充放电循环过程进行模拟,分析系统的热力学性能和各个部件的变工况特性.结果表明,系统的充放电效率可达62.4％.储能时,受洞穴内压力变化影响,两级压缩机压比、效率不断改变,从而引起下游填充床蓄热器进口温度变化;释能时...     

光热吸储系统填充床多孔结构参数研究

为了对基于二次反射式聚光集热系统的光热吸储系统的建设提供理论支持,针对带有循环风机的光热吸储系统开展数值模拟和参数化分析研究。根据能量守恒方程,建立了岩石填充床的一维二相瞬态传热模型,通过MATLAB软件模拟了一个月的储热放热过程,以储热、放热、吸收效率,太阳能-〖HT5”,7”〗火〖KG-*3〗用〖HT5”〗转换比和平均出口空气温度作为系统热性能的评价指标,分析岩石颗粒直径和孔隙率对系统热性能的影响。结果表明：在30次循环结束后,系统达到稳定运行状态;岩石颗粒直径的变化对系统热性能影响较小,颗粒直径从0.03 m增至0.05 m,孔隙率、储热效率、放热效率和太阳能〖HT5”,7”〗火〖KG-*3〗用〖HT5”〗转换比下降幅度均在2%以内,平均出口空气温度由1 120 K降至1 100 K;岩石孔隙率的变化对系统热性能影响较大,孔隙率从0.8降至0.4,储热效率由96%增至98.8%,放热效率由97.9%降至92.7%,但吸收效率和太阳能-〖HT5”,7”〗火〖KG-*3〗用〖HT5”〗转换比变化幅度在0.9%内,平均出口空气温度由1 131 K降低至1 122 K。     

岩石填充床蓄热性能试验研究

储能系统可以有效地提高能源利用率,是解决能量供需不平衡以及可再生能源不稳定问题的重要方式,近些年来已经成为国内外的研究热点。填充床是热能存储的主要形式之一,它是一个充满填充材料的热量存储装置,岩石和鹅卵石是最常用、最可靠的填充材料。文章分析了以高压空气作为传热流体的岩石填充床的蓄热特性,讨论和研究了不同试验参数对蓄热效率的影响。结果表明,岩石填充床的蓄热效率随空气压力的升高而降低,随空气质量流量的增大而增大,因而在较大的空气质量流量和较低的空气压力条件下可以得到较高的蓄热效率。     

填充型U型管式真空集热管的热性能分析

通过理论分析方法对一种新型的填充型U型管式真空集热管的热性能进行研究,建立U型管内流体的能量平衡方程,分析U型管两支管内流体沿轴向的温度变化,对热损失系数和填充层导热系数等影响集热管热性能的关键参数进行分析。并以石墨作为填充材料,对石墨填充U型管式和铝翼U型管式真空集热管进行试验研究。结果表明:理论分析和试验研究的结果吻合较好,填充U型管式真空集热管具有良好的热性能,其集热效率可较现有铝翼型U型管式真空集热管提升12%。     

多区相变材料填充床储热性能数值分析

为进一步提高相变储能填充床储热性能,运用计算流体力学软件Fluent采用DEM-CFD数值模拟方法对轴向填充不同熔点颗粒的填充床进行了储热过程的数值分析.在分别填充了 240和480个相变材料颗粒的直径为200 mm的相变储能填充床内,探究沿热流体流动方向分层逐级排布更低熔点相变材料的排布方式对填充床的储能速率、储能效率、热流体和相变储热材料温度分布的影响.研究表明:在轴向分层排布不同相变点的相变材料会对床内轴向温度场有显著影响;分层排布的方式使填充床的储能速率、储能效率均得到了提高,240和480颗粒填充床平均储能速率分别提升约31.0％和25.1％.     

热能储存过程的热经济学性能评价

从以热力学第二定律为基础的热经济学角度出发,对一个湿热热能储存过程进行了热经济分析,并提出了一个评价热能储存过程热经济生性能的指标－储存单位热能的净收益,讨论了传热单元数,无因次充热时间以及加热气流和被加热液体的热容量之比等参数对其性的影响,结果表明,对热能储存过程存在一最佳的传热单元数和无因次充热时间,在传热单元数较大时,还存在一最佳的加热气流与被加热液休的热容量之比。     

柱状颗粒填充床的储能性能分析

填充床储能是一种很有发展前景的热能储存技术,它具有可降低存储成本和提高太阳能热系统开发效率等优点。研究人员多采用球形的储能单元,而圆柱体在储能填充床换热中有其独特的优势,因此基于圆柱形和拉西环形两种柱状颗粒,建立了一种潜热储能填充床的三维模型,采用数值模拟的方法分别研究两种柱状颗粒组成的填充床的储能性能,分析了储能填充床的直径比对其性能的影响。研究表明,填充床直径比越大,其储能性能越好。同时研究了圆柱形储能单元高度和拉西环形储能单元孔径对储能性能的影响。结果表明,在研究范围内,由高度为3 mm的圆柱形储能单元和孔半径1.50 mm的储能单元分别组成的填充床储能速率最高。     

填充床熔盐蓄热器的动态温度与应力特性北大核心CSCD

建立了填充床熔盐蓄热器的热-力耦合数值模型,基于此模型,研究了多次蓄-放热循环下罐体壁面温度与应力的动态变化特性,并探讨了蓄热罐体产生高温蠕变与塑性屈服的失效区域。结果表明:单次蓄-放热循环中,①壁面温度呈4个阶段的变化趋势,即蓄热时的急剧温升与稳定阶段,放热时的缓慢温降与急剧下降阶段,且大部分罐壁均会产生蠕变现象;②筒节1~5的壁面处于低应力水平的弹性状态,壁板底端存在应力集中导致的塑性屈服现象,且峰值应力在蓄热时呈逐渐上升、放热时逐渐下降的变化趋势;多次蓄-放热循环中,①罐壁最高温度在631~836 K之间呈周期性变化,随着循环次数的增加,处于弹性状态的壁面在低应力与蠕变的作用下损伤累积,增加了蓄热器失效的风险;②内壁面峰值应力在275~423 MPa之间呈周期性变化,使得蓄热罐体可能会产生高应力(大于屈服强度)引起的低周疲劳断裂失效现象。本研究可为开展填充床蓄热器的动态应力疲劳寿命评估提供有效参考方法。     

填充床流动求解与基于Chimera网格的分布式并行计算

填充床是一种常见的化学和生化反应器。由于内部结构的复杂性,填充床的局部流动求解一直是个颇有挑战性的问题。传统的填充床数值模拟是在CFD软件Fluent的平台上,采用非结构化网格求解。采用非结构网格求解存在网格生成困难,网格数目过多以及计算时间长等问题。Chimera网格的应用大大减少了填充床网格的数目及网格生成的难度。PVM分布式并行计算与Chimera网格的结合,使填充床的求解效率得到很大的提高。通过对两种方法在计算使用时间、内存使用量及计算结果的具体比较,阐述了Chimera网格结合PVM分布式并行计算在填充床流动求解中的优势。     

两级填充床式压缩空气储能系统充放电行为研究

基于两级填充床式压缩空气储能系统运行原理,建立了压缩机、透平、填充床蓄热器及储气洞穴的非稳态分析模型,对两级填充床式压缩空气储能系统充放电行为进行了模拟,分析了系统在给定充电功率下的整体热力学性能和各部件的运行特性。结果表明：相比于完整充放电循环,在给定的充电功率下系统的充放电效率仅为54.33%,下降了约8.07%;受到储能功率的影响,压缩机的效率变化范围较大,仅有77.13%的电能转化为压缩空气的内能,而高/低压透平因为进口处空气温度逐渐降低而偏离设计工况导致效率下降;压缩机和透平的火用损之和占总火用损的81.51%。     

Effect of storage on thermal performance of a building

The effect of thermal storage on the thermal performance of a non-airconditioned room of size 6 × 4 × 2.7 m has been analysed. It is found that the presence of thermal storage decreases the swing in room temperature and that the increased surface area is more effective in reducing the temperature swing than large thermal capacity of the storage material.     

Full scale thermal testing of latent heat storage in wallboard

Full scale thermal storage tests were conducted in a room lined with PCM wallboard having latent heat storage capacity. The results were compared with those obtained from tests conducted in a similar room lined with ordinary wallboard. The research showed that PCM wallboard can function efficiently as a thermal storage medium which can be applied to peak load shifting, improved use of waste and solar heat as well as more efficient operation of heating and cooling equipment.     

Thermal energy storage in building integrated thermal systems: A review. Part 2. Integration as passive system

Energy consumption trends in residential and commercial buildings show a significant increase in recent decades. One of the key points for reducing energy consumption in buildings is to decrease the energy demand. Buildings envelopes are not just a structure they also provide protection from outdoor weather conditions always taking into account the local climate. Thermal energy storage has been used and applied to the building structure by taking advantage of sensible heat storage of materials with high thermal mass. But in recent years, researchers have focused their studies on the implementation of latent heat storage materials that if well incorporated could have high potential in energy demand reduction without occupying the space required by sensible storage. The aim of this study is to review the thermal energy storage passive systems that have been integrated in building components such as walls, ceilings or floors, and to classify them depending on their component integration.     

泡沫铜强化石蜡相变蓄热特性的数值分析

通过构建泡沫金属内固液相变传热模型,对方腔蓄热单元中泡沫铜强化石蜡相变蓄热特性进行数值分析。数值模型采用考虑泡沫金属真实结构的等效导热系数通用模型,并兼顾石蜡在融化前后与金属骨架之间的热非平衡效应。通过求解模型得到方腔内石蜡固液界面演化规律与温度分布,进而对蓄热过程进行火用分析。结果表明:当前数值模型能较好地预测泡沫铜内固液相变传热;泡沫铜显著改善了石蜡相变的空间均匀性,减小了蓄热区温度梯度,使蓄热速率和火用效率得到有效提高。     

固体颗粒储热特性及热稳定性实验研究

在双碳目标下,热电解耦对提高热电联产机组调峰灵活性具有重要作用。流化床固体颗粒储热在热电解耦上的应用可解决储热水罐温度范围小的问题,同时对提高能源利用效率具有重要作用。流化床换热器具有流化换热系数高的特点,具有广阔的应用前景,但用于热电解耦的流化床换热器的储热颗粒的选择有待进一步深入研究。本文选取四种来源广泛、价格低廉的沙漠沙、石英砂、玄武岩、气化粗渣作为储热材料,并分别对四种材料的密度与比热容进行了测试,对热处理前后的样品进行了SEM、XRD与XRF的分析,试验结果表明,四种储热材料的储热能力顺序为：玄武岩>沙漠沙>石英砂>气化粗渣,对最优的玄武岩与沙漠沙热稳定性进行测试,热稳定性顺序为：玄武岩>沙漠沙,结合储热性能、热稳定性及经济性综合考虑,沙漠沙的综合储热性能最优,可以作为流态化换热器的储热材料。     

泡沫铜对相变蓄热系统蓄热性能影响的实验研究

石蜡作为一种有机固液相变材料,因其具有高潜热值、无毒、无腐蚀、性能稳定等优点被广泛应用于热蓄存、电子冷却及建筑温控等领域。但在蓄热过程中,因石蜡导热系数较低,导致蓄热时间过长、温差过大。实验按照1∶3的比例将泡沫金属铜均匀分布在石蜡箱体中,探究泡沫铜对石蜡相变速率的影响。结果显示:加入泡沫铜后,有效地提升了石蜡的相变速率,缩短了石蜡相变的时间;同时加入泡沫铜后,石蜡内部温差明显减小,温度分布更加均匀,并且有效缓解了自然对流造成的顶部过热和底部不熔化现象。     

Experimental investigation on a combined sensible and latent heat storage system integrated with constant/varying (solar) heat sources

The objective of the present work is to investigate experimentally the thermal behavior of a packed bed of combined sensible and latent heat thermal energy storage (TES) unit. A TES unit is designed, constructed and integrated with constant temperature bath/solar collector to study the performance of the storage unit. The TES unit contains paraffin as phase change material (PCM) filled in spherical capsules, which are packed in an insulated cylindrical storage tank. The water used as heat transfer fluid (HTF) to transfer heat from the constant temperature bath/solar collector to the TES tank also acts as sensible heat storage (SHS) material. Charging experiments are carried out at constant and varying (solar energy) inlet fluid temperatures to examine the effects of inlet fluid temperature and flow rate of HTF on the performance of the storage unit. Discharging experiments are carried out by both continuous and batchwise processes to recover the stored heat. The significance of time wise variation of HTF and PCM temperatures during charging and discharging processes is discussed in detail and the performance parameters such as instantaneous heat stored and cumulative heat stored are also studied. The performance of the present system is compared with that of the conventional SHS system. It is found from the discharging experiments that the combined storage system employing batchwise discharging of hot water from the TES tank is best suited for applications where the requirement is intermittent.     

Analysis and Calculation of Heat Storage Capacity in Drum Boilers

为解决传统的试验方法获得蓄热系数的困难,通过对锅炉水冷壁、汽包和过热器的机理分析,得出了汽包锅炉蓄热的理论计算方法,对2台不同容量机组的4种工况进行了计算,并通过实际机组运行数据对计算结果进行了验算.结果表明：水和金属的蓄热随压力的降低而增加,蒸汽的蓄热随着压力的降低而降低;各种介质的蓄热在不同负荷下占有的比例不同;运行工况改变时,锅炉蓄热也表现出不同的特征.     

Performance of indirect through pass natural convective solar crop dryer with phase change thermal energy storage

A state-of-the-art solar crop dryer was developed with thermal energy storage to maintain continuity of drying of herbs for their colour and flavour vulnerability. The dryer consists of flat plate solar collector, packed bed phase change energy storage, drying plenum with crop trays and natural ventilation system. Dryer is designed with a maximum collector area of 1.5 m², six crop trays with an effective area of 0.50 × 0.75 m², can hold 12 kg of fresh leafy herbs. The dryer is attached with a packed bed thermal energy storage having capacity of 50 kg phase change material (PCM). The drying system works in such a manner that phase change material stores the thermal energy during sun shine hours and releases the latent and sensible heat after sunset, thus dryer is effectively operative for next 5–6 h. The temperature in drying chamber was observed 6 °C higher than the ambient temperature after sunshine hours till the mid night during the month of June at Jodhpur. Economic performance of the dryer was analysed with return on capital and simple payback period as 0.65 and 1.57 year respectively on optimum cost of raw material and product sale price.     

Thermal performance of a non-air-conditioned building with PCCM thermal storage wall

This paper presents a time-dependent periodic heat transfer analysis of a non-air-conditioned building having a south-facing wall of phase-changing component material (PCCM). A rectangular room (6 × 5 × 4 m) based on the ground is considered. The effects of heat transfer through walls and roof, heat conduction to the basement ground and furnishings, heat gain through window and heat loss due to air ventilation have been incorporated in the periodic time-dependent heat transfer analysis. The time-dependent heat flux through the PCCM south-facing wall has been obtained by defining the effective thermal properties of the PCCM for a conduction process with no phase change. Numerical calculations are made for a typical mild winter day (7 March 1979) at New Delhi for heat flux entering through the wall and inside air temperature. Further, a PCCM wall of smaller thickness is more desirable, in comparison to an ordinary masonry concrete wall, for providing efficient thermal energy storage as well as excellent thermal comfort in buildings.