某小区地源热泵地埋管换热器的测试与计算

地源热泵系统的关键部分在于地下换热系统,由于地下岩土热物性参数的不同,使得地埋管换热器的换热能力有较大差异,这将直接影响到整个系统的使用效果和工程造价。文章以线热源理论为依据,对某实际工程项目进行岩土热响应测试,并计算相关的热物性参数,同时提出了一种工程简化算法,该算法综合考虑了岩土热物性测试结果与建筑物的负荷特点,其计算结果可以作为工程设计的依据。     

地源热泵地下岩土热物性的测定方法

提出了可用于现场测量计算地下岩土综合热物性参数的方法。垂直埋设在地下的换热器与周围岩土换热过程可以近似地看作半无限大介质中常热流边界条件下的非稳态导热过程来处理。这种方法克服了其他常用研究模型对钻孔中埋管的具体位置、上升管及下降管之间的距离、换热器材料和回填材料的物性参数的要求,相应地消除了上述各个参数所带来的误差。通过测量地埋换热器的循环水流量、进出水口温度,加热器的加热功率等数据确定地下岩土综合的热物性参数。     

现场测试地下岩土平均热物性参数方法

平均热物性参数的大小对钻孔的数量及钻孔的深度具有显著的影响,进而影响地源热泵系统的初投资。为了能够在现场测量地下岩土的平均热物性参数,利用一套现场测量设备测量了对地下埋管回路施加的热流与回路中循环水温度随时间的变化,使用自行开发的软件,采用参数估计方法,计算并确定了地下岩土的平均热物性参数。     

地下蓄能体多孔介质传热及其热湿迁移分析

蓄能技术是实现能源可再生和高效利用的一个有效途径。能量通过短期或长期蓄存,提高其综合利用率和实现能源的实时补充。地下蓄能过程是一个受岩土特征影响的复杂多变的传热过程。着重论述地下蓄能技术发展状况和面临的研究问题,并通过模型分析和模拟计算对多孔特征下蓄能体传热作用进行了分析和探讨,考察了几种典型工况下的温度分布。     

地下岩土能量传输动态控制特性实验研究

针对地下蓄能和地源热泵地下高效传热和有效能量传输控制问题开展研究,通过阵列多热源岩土槽传热实验,分析比较3种典型的岩土蓄能传热动态控制模式,探索不同动态负荷控制的岩土传热过程温度变化形态,分析能量蓄存、扩散及保持各阶段的温变特性和影响规律。结果表明,热源排列负荷交变和间歇周期对地下岩土传热具有重要作用,其振幅和相位是寻求最佳能量传输的主要影响因素。合理的热源间负荷调节有利于地下换热能量的区域性保存和传输扩散。     

大石桥地区地源热泵地埋管换热器测试与计算研究

地埋管热泵运行效果的关键是地埋管换热效率,由于在不同地区的地下土壤与岩石的热物性的不同,使得地埋管换热器的换热效率在不同地区有较大差别,会直接影响地埋管热泵的实际运行效果和大幅度增加工程的造价。以线热源理论作为理论依据来对大石桥公安局业务技术用房项目进行岩土热响应测试并计算土壤的热物性参数。与此同时,改进了一种工程简化计算公式,公式综合考虑了岩土热物性和建筑冷热负荷以及地埋管铺设形式,用该简化的公式得出的地埋管换热器的长度与原有的计算公式得出的结果基本一致,该公式可以作为工程运用的依据。     

基于圆柱热源模型的现场测量地下岩土热物性方法

在埋地换热器圆柱热源模型的基础上采用参数估计法建立了一套可用于现场确定土壤热物性的方法。结合地源热泵系统单井热响应测试实验,计算了地下岩土热物性参数,模拟了管内流体平均温度随时间变化规律,与实验值比较,发现该方法较线热源法更加接近实际。     

电热冷联产的新压缩空气蓄能系统

提出一个将压缩空气直接在空气透平中膨胀做功发电,并产出热量和冷量的新压缩空气蓄能方法。分析了该新压缩空气蓄能系统工作的不可逆循环,并建立了仅忽略所有换热器流动阻力损失的该蓄能系统之能量转换利用率（η）计算方程式。用该方程分析研究了空气透平膨胀机与压缩机等熵效率、压缩机排气热能度、空气透平排气冷量度、换热器传热温差和空气压缩比等参数对系统η值的影响,发现空气透平等熵效率提高对η值的贡献大于压缩机效率同样提高的功效;在其它参数确定时,存在最佳压比,可使系统的能量转换利用率在该条件下达极值。分析表明：电热冷联产新压缩空气蓄能系统的能量转换利用率可达0．8左右。     

应用于道路融雪中太阳能集热蓄能和地下换热器影响作用研究

针对新型道路融雪化冰技术的太阳能路面集热和地下蓄能过程进行模型分析,研究逐年长期地能利用和热泵循环过程的基本性能。研究表明:运行5a后,有、无蓄能过程的热泵系统间COP相差达10%。其中,非蓄能条件下,地下均衡温度降低,热泵耗能增加,COP降低;采用集热蓄能,补偿地下热量缺失,可以达到地温恢复或增高,提升运行效能。此外,比较四孔和七孔地下换热器设置规模,两者间的流体最低温度相差2倍以上,孔数规模对地下温度、吸热量和热泵效能影响较大。因此,在地下换热器系统设计中,即要考虑孔数规模的经济性,又要保证热力性能。     

北方地区岩土导热系数及换热量的测试研究

岩土导热系数是地源热泵地埋管换热器的重要设计参数;测井单位深度换热量是地埋管换热器系统的设计依据。掌握工程区域岩土的热物性及换热性能,是保证地源热泵系统高效、稳定运行的关键。文章建立了现场测试岩土导热系数及换热量的方法,并结合沈阳浑南高新技术产业开发区某地源热泵工程,测试分析了岩土导热系数和测井单位深度换热量。结果表明,该区域的岩土具有较好的导热能力,适合采用地埋管地源热泵系统;在特殊地理条件下设计地源热泵系统方案前,应对拟建区域的地质条件进行全面勘探,以优选工程区域,为岩土热响应测试结果的可靠性提供保障。     

Solar Thermal Power Towers

The solar thermal central receiver technology, known as solar power towers, is rapidly evolving to a state of near-term energy availability for electrical power generation and industrial process heat applications. The systems consist of field arrays of heliostat reflectors, a central receiver boiler, short term thermal storage devices, and either turbine-generators or heat exchangers. Fluid temperatures up to 550°C are currently achievable, and technology developments are underway to reach 1100°C. Six solar power towers are now under construction or in test operation in five countries around the world.     

Thermal Energy Storage and Phase Change Materials: An Overview

The storage of thermal energy in the form of sensible and latent heat has become an important aspect of energy management with the emphasis on efficient use and conservation of the waste heat and solar energy in industry and buildings. Latent heat storage is one of the most efficient ways of storing thermal energy. Solar energy is a renewable energy source that can generate electricity, provide hot water, heat and cool a house, and provide lighting for buildings. Paraffin waxes are cheap and have moderate thermal energy storage density but low thermal conductivity and, hence, require a large surface area. Hydrated salts have a larger energy storage density and a higher thermal conductivity. In response to increasing electrical energy costs and the desire for better lad management, thermal storage technology has recently been developed. The storage of thermal energy in the form of sensible and latent heat has become an important aspect of energy management with the emphasis on the efficient use and conservation of the waste heat and solar energy in the industry and buildings. Thermal storage has been characterized as a kind of thermal battery.     

Review on solar thermal energy storage technologies and their geometrical configurations

Because of the unstable and intermittent nature of solar energy availability, a thermal energy storage system is required to integrate with the collectors to store thermal energy and retrieve it whenever it is required. Thermal energy storage not only eliminates the discrepancy between energy supply and demand but also increases the performance and reliability of energy systems and plays a crucial role in energy conservation. Under this paper, different thermal energy storage methods, heat transfer enhancement techniques, storage materials, heat transfer fluids, and geometrical configurations are discussed. A comparative assessment of various thermal energy storage methods is also presented. Sensible heat storage involves storing thermal energy within the storage medium by increasing temperature without undergoing any phase transformation, whereas latent heat storage involves storing thermal energy within the material during the transition phase. Combined thermal energy storage is the novel approach to store thermal energy by combining both sensible and latent storage. Based on the literature review, it was found that most of the researchers carried out their work on sensible and latent storage systems with the different storage media and heat transfer fluids. Limited work on a combined sensible-latent heat thermal energy storage system with different storage materials and heat transfer fluids was carried out so far. Further, combined sensible and latent heat storage systems are reported to have a promising approach, as it reduces the cost and increases the energy storage with a stabilized outflow of temperature from the system. The studies discussed and presented in this paper may be helpful to carry out further research in this area.     

Melting and solidification performance in two horizontal shell-and-tube heat exchangers with different structures

Recently, a critical problem of latent heat thermal energy storage remains the low thermal conductivity of phase change materials (PCMs), which can lead to low heat transfer rate. Structural optimization design is an effective solution for this problem. In this work, two horizontal shell-and-tube heat exchangers (HEs) with one inner tube (n = 1) and four inner tubes (n = 4) are designed keeping the same amount of PCM and water flow rate, and their melting and solidification thermal performance and heat transfer characteristics are compared. The results show that in comparison with one-inner-tube HE, the temperature of detected points are affected by both upper and lower inner tubes for four-inner-tube HE, thus the differences in phase change process appear. In addition, the phase change time reduction rates are 34.1%, 33.39%, 28.82% at T_in (inlet water temperature) = 75°C, 80°C, 85°C during charging process, and 17.2%, 27.69%, 36.67% at T_in = 10°C, 15°C, 20°C during discharging process, respectively. In comparison with the one-inner-tube HE, the theoretical efficiency of four-inner-tube HE is increased from 75.88% to 90.34%. Although more friction loss should be paid by four-inner-tube HE, a lower energy consumption and a higher heat-energy ratio are achieved. Based on the results of this study, the amount of cumulative heat per energy consumption is 1.52 × 10⁸ and 2.88 × 10⁸ for one-inner-tube and four-inner-tube HE, respectively.     

Thermal energy storage of phase change materials in the solidification process inside the quasi-square heat exchanger: CFD simulation

The high latent heat of phase change materials (PCMs) makes them one of the most important sources of heat energy storage systems. However, due to the slow rate of heat transfer in these materials, using conductive materials such as fins and nanoparticles could improve the thermal efficiency of these energy storage systems. So in this article, cross-shaped fins and Copper(II) oxide nanoparticles with different synthesized forms and various volume fractions have been employed to increase the thermal efficiency of paraffin PCMs. In this simulation, three fin models based on the installed size, the shape of the synthesized nanoparticles in brick, cylindrical, and platelet forms, and the nanoparticle volume fraction of the Copper(II) oxide is 1%–4% are studied. Increasing the volumetric ratio of nanoparticle and shape coefficient decrease the time of solidification, while increasing the length of the cross-shaped fins raises the solidification rate and improves heat transfer. Finally, it was found that when the inner and outer walls play a role in the solidification process at the same time, the solidification rate will increase by more than 66% as more zone of the surface is exposed to cold.     

蓄热介质对太阳能热风发电集热器性能的影响

分别以沙子、石子以及石子与充水黑色密封管的组合作为蓄热介质,搭建了太阳能集热器试验装置并进行了相应的试验研究,得出了不同蓄热介质的吸放热特性及其对集热器内空气进出口温差、集热器效率的影响规律.结果表明:在相同的平均辐射强度下,石子与充水黑色密封管组合集热器的蓄热性能好,且集热器空气进出口温差及集热器效率最大,为太阳能热风发电系统集热器地面蓄热材料的选用提供了依据.     

A review on theory and application of chemical heat pump in thermal energy storage

化学热泵是高效,环保的新型能源技术,在余热回收,储热,可再生能源等领域具有广泛的应用前景.本文综述了化学热泵系统的一般理论和在储热技术中的应用,介绍了化学热泵系统技术在反应与工质对选择,传热强化以及工业研究与应用等方面的发展.     

板式相变贮能换热器传热模型和热性能分析

建立了板式相变贮能换热器的无量纲传热模型。它对流体入口流量、入口温度随时间变化情况和需考虑入口效应及添加肋片的情况均适用。模型解和文献准稳态解吻合。作为算例,藉此模型从各时刻的流体温度、相变界面随空间的分布情况和相变蓄热比、相变传热效率、传热系数、完全相变截面位置随时间的变化情况六个角度分析了一板式相变贮能换热器的相变传热性能。该模型可为板式相变贮能换热器的结构优化设计和热性能分析提供帮助。     

热回收蓄能空调系统的应用研究

本文重点阐述了热回收技术和蓄能技术在空调系统中的应用，在工作原理、节能循环分析、经济性分析、控制和应用注意事项等多方面进行了初步研究，研究结果表明该节能技术在制冷空调系统中的运用大有前途，可以得到大力的推广。