Palmitic Acid-Lauric Acid/Expanded Graphite as Form-Stable Composite Phase Change Material for Low-Temperature Energy Storage Applications

Low thermal conductivity of binary fatty acid mixture of palmitic and lauric acids(PA-LA) within the value range of 0.15-0.17 W/(m·K) restricts its wide utilization as thermal energy storage material in the active regime of solar heating applications at low operating temperatures. Nevertheless, this mixture as phase change material(PCM) has a suitable phase-change temperature and heat of 36 ℃ and 176.3 J/g, respectively. Hence, the objective of this study is to formulate a novel form-stable comp...     

Melting of PCM in a thermal energy storage unit: Numerical investigation and effect of nanoparticle enhancement

The present paper describes the analysis of the melting process in a single vertical shell‐and‐tube latent heat thermal energy storage (LHTES), unit and it is directed at understanding the thermal performance of the system. The study is realized using a computational fluid‐dynamic (CFD) model that takes into account of the phase‐change phenomenon by means of the enthalpy method. Fluid flow is fully resolved in the liquid phase‐change material (PCM) in order to elucidate the role of natural convection. The unsteady evolution of the melting front and the velocity and temperature fields is detailed. Temperature profiles are analyzed and compared with experimental data available in the literature. Other relevant quantities are also monitored, including energy stored and heat flux exchanged between PCM and HTF. The results demonstrate that natural convection within PCM and inlet HTF temperature significantly affects the phase‐change process. Thermal enhancement through the dispersion of highly conductive nanoparticles in the base PCM is considered in the second part of the paper. Thermal behavior of the LHTES unit charged with nano‐enhanced PCM is numerically analyzed and compared with the original system configuration. Due to increase of thermal conductivity, augmented thermal performance is observed: melting time is reduced of 15% when nano‐enhanced PCM with particle volume fraction of 4% is adopted. Similar improvements of the heat transfer rate are also detected. Copyright © 2012 John Wiley & Sons, Ltd.     

复配石蜡/膨胀珍珠岩相变颗粒的热性能研究

通过固体石蜡与液体石蜡熔融混合复配制成低熔点相变石蜡,其中以固液比1:1制备的相变石蜡熔点为25.1℃,潜热为104.3kJ/kg.500次冷热相变循环后石蜡的热物性仅轻微衰减,热化学稳定性好.利用多孔膨胀珍珠岩吸附熔融石蜡可以制备石蜡,膨胀珍珠岩相变颗粒,其中石蜡:珍珠岩质量比为3.5:1.0的相变颗粒不团聚,石蜡含量最高为77.78%.通过SEM、FT-IR、DSC等表征手段测得:该相变颗粒熔点为25.6℃,潜热为80.3k/Ag,具有优良的热物性;相变颗粒仅仅是石蜡和膨胀珍珠岩的嵌合,可以加入到墙体材料中用于建筑节能.     

PCM设备的故障处理

PCM（脉冲编码调制）设备作为常用的终端设备，对其故障快速判别处理是非常重要的。根据实际维护经验，介绍了2M、二线、四线等故障的分析处理，包括一些特殊故障的定位分析，具有通用性，可作为维护工作的参考。     

VOIP软件结构和分组传输分析

本文简要介绍了VOIP的基本概念和软件结构，重点分析了VOIP的分组传输过程，并对VOIP通信中的网络问题及解决方法进行了探讨。     

Liquid-phase theoretical antioxidant activity trend of some cinnamic acid antioxidants

The trend in antioxidant activity of four cinnamic acid antioxidants, derived on the basis of their liquid-phase phenolic O H bond dissociation enthalpies, is determined theoretically, with the aid of the polarizable continuum model at the density functional theory level. Three solvents, differing in their hydrogen-bonding ability and polarity—n-heptane, acetonitrile, and ethanol—were used to model different environmental situations. The trends in solution-phase antioxidant activity appeared different in each solvent; still, the theoretical antioxidant activity trend derived in n-heptane was in excellent agreement with the experimental one in the lipid systems and the gas-phase system. Different ortho substituents show notably different solvent effects. These results could lead to the determination of reliable antioxidant activity trends in real-solution environments of interest in food or biological science frameworks.     

用VHDL设计PCM采编器

介绍了通信技术中PCM采编器的工作原理，用VHDL设计了PCM采编器，并给出了仿真波形图，最后用CPLD器件实现了PCM采编器。     

Experimental tile with phase change materials (PCM) for building use

The use of phase change materials (PCM) and their possible architectural integration is a path in the search for optimizing energy efficiency in construction. As part of this path, a pavement has been designed which, in combination with the PCM, serves as a passive thermal conditioning system (new patent n°. ES2333092 A1) [1]. The prototype has been tested experimentally and the results proved that it is a viable constructive solution improving the energy performance of sunny locals.     

Temperature reduction due to the application of phase change materials

Overheating is a major problem in many modern buildings due to the utilization of lightweight constructions with low heat storing capacity. A possible answer to this problem is the emplacement of phase change materials (PCM), thereby increasing the thermal mass of a building. These materials change their state of aggregation within a defined temperature range. Useful PCM for buildings show a phase transition from solid to liquid and vice versa. The thermal mass of the materials is increased by the latent heat. A modified gypsum plaster and a salt mixture were chosen as two materials for the study of their impact on room temperature reduction. For realistic investigations, test rooms were erected where measurements were carried out under different conditions such as temporary air change, alternate internal heat gains or clouding. The experimental data was finally reproduced by dint of a mathematical model.     

基于GPU 的PCM/FM 信号非相干鉴频解调算法

面向未来任务日益多样化,试验环境日趋复杂化,传统基于FPGA 的脉冲编码调制/调频(pulse code modulation/frequency modulation,PCM/FM)遥测系统存在软硬件紧耦合、研发周期长、升级维护困难等缺点,无法 满足未来遥测系统大规模部署对弹性、灵活和敏捷的需求。针对以上问题,设计基于GPU 的PCM/FM 信号非相干 鉴频解调实现方法。根据算法原理和GPU 并行方法设计出基于GPU 的并行解调实现方法,分别从并行数字下变频、 并行FIR 滤波和并行差分鉴频3 部分分析具体模块的并行化实现方法。实验结果表明：在码速率为10 Mbps、每处 理1 s 数据的条件下,基于GPU 的非相干鉴频过程消耗的时间约为426.867 ms,满足解调的实时性要求;解调增益 稍优于传统基于FPGA 的PCM/FM 遥测基带,有约0.1 dB 的解调增益。