相变储能在建筑供暖空调领域的应用前景

介绍储能相变材料及其分类,讨论相变材料在建筑供暖空调领域的应用研究。详细介绍作为相变墙体材料和系统相变材料的研究进展,同时对相变材料在建筑供暖空调系统中的应用前景进行展望。     

Design of optimum compressed air energy-storage systems

Compressed air energy storage (CAES) power systems are being considered by electric utilities for load-leveling application. Their economic benefit and the extent of premium fuel conservation is dependent on their design. An optimum design approach for CAES is presented in this paper. It is based on decomposition of the overall CAES plant/utility grid system into three partially-decoupled sybsystems. Technical and economic models of the subsystems are used in a constrained optimization procedure. The constraints are imposed by the physical characteristics of the subsystems, by interaction among the subsystems and by the interfacing requirements imposed by the utility.To illustrate the concepts, models for the system comprising the compressor train, piping, and an aquifer reservoir have been used in the optimization procedure. Results from these studies show that substantial reductions in capital cost and total operating cost can be achieved using optimization techniques.     

Thermal modeling for thermophotovoltaic systems adopting the radiation network method

The radiation heat transfer model for thermophotovoltaic (TPV) system is constructed by adopting a total-spectrum radiation network. However, no consideration of the wavelength shift in the optical filter will lead to the discrepancy between the evaluated spectral emissive power of the optical filter and the Planck law result. Therefore, a modified spectral radiation network in which the wavelength shift effect is expressed as the form of spectral heat source is developed. The modified spectral radiation network is applied in the thermal analysis of a realistic TPV system in which a quartz envelope takes the place of the optical filter, while the optical filter is combined with the cell array. Several important design parameters are figured out, including spectral radiation power density and spectral efficiency of the system, as well as the equivalent radiative temperature of the quartz envelope.     

三水合乙酸钠复合相变材料的循环特性研究

三水合乙酸钠单位体积潜热约为同熔点下石蜡的2倍,但是具有严重的相分离和高过冷度,限制了其使用.本工作设计了一种使用半导体热电制冷片的循环测试装置,大幅缩短了循环实验周期,以用来研究三水合乙酸钠的循环特性.在过冷度稳定性探究中,通过添加十二水合磷酸氢二钠和纳米氧化铝为成核剂,以及羧甲基纤维素钠为增稠剂,进行了 0～500...     

Plasma—Particle Transfer Process with Phase—Change and Chemistry Effects

INTaoDUCTIONDuetohighenthalPychemicalactivityandcon-tr0llableatmophere,thermalplasmajetreactorshavebeenextensivelyutilizedinmodernindustrysuchasmetallurgy,materialsprocessing,aerospace,electron-ics,autom0bile,biomedicine,wastemanagementandsoon.Il-3]PowdermaterialproductiQnisatypicalexampleofplasmatechnologyaPplications.Inthiscase,mass,momentumandenergytransferprocessesbetweentheplasmagasandinjectedparticlesarethedominatmechwhsmswhichgovernthemixing,mov-ingandheating0fthematerialparticlesb…     

Properties optimization for phase-change energy storage in air-based solar heating systems

A parametric study has been conducted to determine the optimum physical properties of phase-change energy storage materials for solar air-heating systems. Simulation techniques are used to determine the system performance over the entire heating season. Variations of the solar fraction of the load with melting temperature, latent heat, load characteristics, and control strategy have been determined. Air-heating systems with a wide range of hot water and space heating loads have been examined. The effect of semicongruent melting of the phase change material on system performance has also been investigated.     

Thermal radiation effects and lifetime assessment of first wall materials

Thermal radiation problems of the first wall of fusion reactors are becoming an important factor in the design, cost, and reliability of these reactors, and will strongly affect their prospects for economical operation and future commercialisation. In this study, the thermal radiation effects of first wall fusion reactors were studied experimentally under an externally applied magnetic field. The plasma temperature was measured using the Langmuir probe technique with OA4G electron tubes.

The results showed the electron temperature became higher during propagation parallel to the magnetic field than perpendicular to the same magnetic field. The rapid increase of the electron temperature in the plasma region depends on the increase of the saturation current. It is believed that there is a threshold power level for energy exchange between the electrons and the magnetic field, below which the energy conservation of cold plasma does not apply. By suitable arrangement of the armour plating, the wall cooling effect can be enhanced and wall thermal stress can be reduced to achieve an extended wall lifetime.

For lifetime assessment, Watson's model was used for calculation of thermal stress for several materials such as AISI 316 SS, HT-9, and Inconel 617. The creep stress and swelling stress is dependent on operation time under various irradiation conditions. The effects of wall thickness on lifetime for different materials is also discussed. Evidence showed HT-9 was the best resistant alloy for void swelling. Inconel 617 also performed well with regard to the swelling resistance.     

Sizing phase-change energy storage units for air-based solar heating systems

A simple method for sizing phase-change energy storage (PCES) units for air-based solar heating systems is presented. An effective heat capacity for the phase change unit is obtained as a function of its mass, latent heat, specific heat, and melting temperature. The effective heat capacity can then be used, along with any convenient design method for systems with sensible heat stores, such as the f-chart method, to estimate the thermal performance of the system utilizing PCES.     

Thermal radiation effects on oscillatory squeeze flow with a particle-fluid suspension

The study of squeezing flow has attracted considerable interest in recent years for its important applications in industrial, biomedical and engineering domains such as fibre-reinforced, cell squeeze technology. The aim of this study is to analyze the flow and heat transfer of a squeezed particle fluid with thermal radiation effects between parallel plates. The governing partial differentials are reduced to ordinary differential equations by a similarity transformation and solved numerically using the finite difference method. The effects of different physical parameters on the velocity and temperature profiles are discussed with the help of graphs coupled with comprehensive discussions. The results indicate that the thermal radiation parameter enhanced the fluid and particle temperature distribution and for the plate oscillation case, reverse flow is observed. To show the biological relevance of the analysis, the results obtained analyzed the influence of the squeezed artery wall on the suspension blood flow for normal and diseased blood using the experimental data from the published literature. Finally, a comparison between the present similarity solutions and previously published results shows the accuracy of the current results.     

Thermal response of a packed bed of spheres containing a phase-change material

A computational model of the transient thermal response of a packed bed of spheres containing a phase-change material (PCM) is presented. A one-dimensional separate phases formulation is used to develop a numerical analysis of the dynamic response of the bed which is subject to the flow of a heat transfer fluid, for arbitrary initial conditions and inlet fluid temperature temporal variations. Phase-change models are developed for both isothermal and nonisothermal melting behaviours. Axial thermal dispersion effects are modelled, including intraparticle conduction (Biot number) effects. Regenerative thermal storage applications involve flow reversals to recover the stored energy; this aspect of operation is included in the present model. Results from the model for a commercial sized thermal storage bed for both the energy storage and recovery periods are presented. Experimental measurements of transient temperature distributions in a randomly packed bed of uniform spheres containing a PCM for a step-change in inlet air temperature are reported for a range of Reynolds number.     

Evaluation of intermittent-distributed-generation hosting capability of a distribution system with integrated energy-storage systems

The penetration rate of distributed generation is gradually increasing in the distribution system concerned. This is creating new problems and challenges in the planning and operation of the system. The intermittency and variability of power outputs from numerous distributed renewable generators could significantly jeopardize the secure operation of the distribution system. Therefore, it is necessary to assess the hosting capability for intermittent distributed generation by a distribution system considering operational constraints. This is the subject of this study. An assessment model considering the uncertainty of generation outputs from distributed generators is presented for this purpose. It involves different types of regulation or control functions using on-load tap-changers (OLTCs), reactive power compensation devices, energy storage systems, and the reactive power support of the distributed generators employed. A robust optimization model is then attained It is solved by Bertsimas robust counterpart through GUROBI solver. Finally, the feasibility and efficiency of the proposed method are demonstrated by a modified IEEE 33-bus distribution system. In addition, the effects of the aforementioned regulation or control functions on the enhancement of the hosting capability for intermittent distributed generation are examined.     

Multifunctional silicone rubber/paraffin@PbWO4 phase-change composites for thermoregulation and gamma radiation shielding

A new type of silicone rubber (SR)-based gamma radiation shielding and thermal regulation composite was developed with paraffin (Pn) @lead tungstate (PWO) phase-change microcapsules as functional fillers. These SR/Pn@PWO composites have a PWO component that not only exhibits excellent photon attenuation but also can provide a barrier to the molten phase-change material core. The thermal and mechanical properties of the composites were characterized by differential scanning calorimetry, thermal regulation experiment and mechanical tests. Thermal analysis indicated that the SR/Pn@PWO composites not only reveal reliable energy storage performance which can reach to 52.72 J g⁻¹ enthalpy values but also exhibit good thermal durability. In addition, SR/Pn@PWO composites have enhanced mechanical properties and excellent thermoregulation performance. And the more microcapsules content, the more significant enhancement effect is. A high-purity germanium gamma spectrometer to measure the attenuation coefficient of the composites for gamma radiation showed that the SR/Pn@PWO composites have good γ-ray-shielding property, which increased with the increase of the microcapsules content.     

Thermal radiation effects of a high‐temperature developing laminar flow in a tube

The thermal radiation effects of a high‐temperature developing laminar flow in a tube are investigated numerically. The two‐dimensional steady flow and heat transfer are considered for an absorbing‐emitting gray medium, whose density is dependent on the temperature. The governing equations of the coupled process are simultaneously solved by the discrete ordinate method combined with the control volume method. For a moderate optical thickness, the velocity distribution, the temperature distribution, and the radial heat flux distribution in the medium as well as the heat flux distribution on the tube wall are presented and discussed. The results show that the thermal radiation effects of a high‐temperature medium are significant under a moderate optical thickness. The flow and convective heat transfer are weakened, and the development of temperature distribution is accelerated noticeably. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 299–306, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20018     

一种与坐卧用具结合的太阳能相变蓄热采暖系统

介绍了一种将太阳能利用、相变蓄热与局部采暖技术相结合的新型太阳能相变蓄热坐卧用具采暖系统。阐述了系统的工作原理,分析了其优点,并给出其设计计算实例。     

Thermal radiation and the second law

The purpose of this paper is to collect and interrelate the fundamental concepts about second law analysis of thermal radiation. This heat transfer mode plays a leading role in solar energy utilization and in high-temperature devices, representing a significant contribution to irreversibility that is frequently omitted in engineering analysis. Entropy and exergy of thermal radiation are reviewed first. Radiative transfer processes are reviewed next, including exchange between surfaces, the presence of a participative medium, and the analysis of combined heat transfer modes. Emphasis is put on grey body radiation when treating with non-black body radiation, due to its relevance in engineering applications. The mathematical formulation of second law analysis of thermal radiation is complex, which limits its use in conventional heat transfer analysis. For this reason, numerical approaches reported to date deal with quite simple cases, leaving an open promising field of research.     

Thermal radiation modeling in multilayer thin film structures

A general technique is developed to account for the microscale heat transfer effects involved with the interaction of thermal radiation and multilayer thin films. In particular, the microscale radiation effects involved with both the emission from the multilayer structure and the reflection of incident radiation are described in detail. Considerable optical interference within the structure occurs when the film thicknesses are on the same order of magnitude as the wavelengths of the incident or emitted radiation; therefore, the net surface reflectivity and emission from the film structure are altered by slight changes in film thickness. Consequently, during high temperature thermal processing of micron thickness films, the resultant temperature profiles and the quality of the processed structure will be affected. The reflectivities and emissivities are calculated numerically using the matrix method for several different layering structures subject to thermal radiation. For the special case of equal optical film thicknesses, cross-correlation peaks are identified; these layering schemes are very sensitive to small film thickness changes. Maximum temperatures attained during thermal processing are calculated for several specific film structures to illustrate the significance of these effects.