Numerical simulation of geothermal-PVT hybrid system with PCM storage tank

As the increase in greenhouse emissions, climate changes, and other irreversible repercussions stems from environmentally destructive energies such as fossil fuels, exploiting solar and geothermal energy as unlimited clean sources of energy in the renewable energy technologies can survive the planet earth, which is facing a catastrophe on a global scale. The main purpose of this research is to study Techno analysis of the combined ground source heat pump (GSHP) and photovoltaic thermal collectors (PVTs) with a “phase-change material” (PCM) storage tank to fulfill the energy demands of a residential building. In the first step of this study, in order to model the heat pump behavior in multi-usage operation modes (heating and cooling), a numerical transient simulation of a water-to-water GSHP, which includes a vertical U-type ground source heat exchanger (GSHX) and a variable speed drive (VSD) compressor, was conducted by developing a numerical code in Engineering Equation Solver software. To study the thermodynamic aspect of the hybrid system in terms of exergy and energy, a transient numerical simulation was accomplished using the TRNSYS program. Also, the impact of effective characteristics of ingredients such as areas of PVT panels and the volume of the storage tank of PCMs on the performance of the hybrid system are investigated. On top of that, the two types of the GSHP-PVT-PCMs and GSHP-PV from the energy and exergy points of view are compared. The obtained results demonstrate that the irreversibility of the solar modules of the GSHP-PVT-PCMs is 6.6% lower than that of the GSHP-PV. Furthermore, the calculation of the annual required load of the building for these two kinds of hybrid systems shows that the use of collectors in this combined system has reduced the total load of the building by 6.5%. The use of collectors in the GSHP-PVT-PCM gives rise to a difference in the value of solar factor (SF) of this system by 1.4% more than the one for the hybrid system without thermal collectors.     

Expansion characteristics of thermally expandable microcapsules for dismantlable adhesive under hydrostatic pressure or in resin

ABSTRACT

The expansion characteristics of thermally expandable microcapsules (TEMs) under hydrostatic pressure or in resin were experimentally investigated. For the experiments, the expansion of the microcapsules was observed in high-pressure nitrogen at high temperature utilizing optical microscopy with a digital camera installed. The TEMs used for the experiments were expanded by heating under hydrostatic pressure up to 3 MPa, but the expansion degree decreased with increasing pressure. A cured bulk specimen of epoxy resin containing the microcapsules was made, and the expansion of the microcapsules was again observed with the microscope. It was found that the expansion of the microcapsules in the resin was saturated at a certain temperature. The stress distribution in the resin produced by the expansion of the microcapsules was calculated by the finite-element method. It was found that normal stress occurred, but it was mainly compressive. Tensile stress was also generated, although the maximum value was smaller than that of shear stress. It was observed that the expansion of the microcapsules was limited when there were many microcapsules in the vicinity of the interface. In other words, a complicated stress state occurred, inducing interfacial failure along the interface.     

六氟化硫PVT关系测定实验教学体会与思考

纯流体PVT关系测定及临界状态观察实验对于学生理解问题的本质,提高理论教学效果具有不可替代的作用。本文介绍了六氟化硫临界状态观察及PVT关系测定仪的制造及使用情况,重点介绍实验数据记录处理等细节上的一些经验体会和我们的建议。     

莺歌海盆地LD8-1构造古压力热动力学模拟

莺歌海盆地LD81构造流体包裹体资料分析结果表明,该构造发生过6期热流体活动,其中有2期为天然气充注,分别对应第2期和第3期热流体活动。依据流体包裹体流体成分、气液比及均一温度,运用PVT热动力学模拟软件(VTFLINC)模拟得到该构造天然气充注时期的古流体压力;结合地层测试资料对LD81构造天然气成藏条件进行了分析。     

Performance evaluation of low concentrating photovoltaic/thermal systems: A case study from Sweden

Some of the main bottlenecks for the development and commercialization of photovoltaic/thermal hybrids are the lack of an internationally recognized standard testing procedure as well as a method to compare different hybrids with each other and with conventional alternatives. A complete methodology to characterize, simulate and evaluate concentrating photovoltaic/thermal hybrids has been proposed and exemplified in a particular case study. By using the suggested testing method, the hybrid parameters were experimentally determined. These were used in a validated simulation model that estimates the hybrid outputs in different geographic locations. Furthermore, the method includes a comparison of the hybrid performance with conventional collectors and photovoltaic modules working side-by-side. The measurements show that the hybrid electrical efficiency is 6.4% while the optical efficiency is 0.45 and the U-value 1.9 W/m² °C. These values are poor when compared with the parameters of standard PV modules and flat plate collectors. Also, the beam irradiation incident on a north-south axis tracking surface is 20-40% lower than the global irradiation incident on a fixed surface at optimal tilt. There is margin of improvement for the studied hybrid but this combination makes it difficult for concentrating hybrids to compete with conventional PV modules and flat plate collectors.     

精密注塑成型PVT最佳保压控制

阐述了PVT最佳保压控制的概念、基本原理及方法,并以精密塑料透镜注射成型为例,通过PVT状态图讨论注射成型工艺过程并制定工艺路线,选择注射-压缩工艺成型精密光学透镜,通过该工艺有效地解决了注塑中的应力问题,在制品的变形、尺寸精度及光学特性等方面大幅提高产品质量.     

Alternatives toward proton conductive anhydrous membranes for fuel cells: Heterocyclic protogenic solvents comprising polymer electrolytes

Fuel cells are gaining increasing attention as a clean and promising technology for energy conversion. One of the key benefits of fuel cells compared to other methods is the direct energy conversion that enables the achievement of high efficiency. The electrolyte membrane is the most essential parts of a fuel cell unit, and consequently has been the subject of considerable research and development. Among the various types of proton conducting electrolytes examined for fuel cell applications, polymer electrolyte membranes (PEMs) are regarded as viable candidates since they enable operation of the cells at desirably low temperatures. This review describes recent progress in the design and development of high performance proton conducting PEMs, including the analysis of the design requirements and strategies for development of advanced PEMs for operation in anhydrous conditions. Some of the most widely used types of azole heterocycles are introduced and compared, particularly in terms of their performance characteristics in polyacids containing different functional groups. In addition, the latest research studies and progress in the field of azole-containing and azole-functionalized electrolyte systems are discussed and reviewed.     

与工艺、电源电压和温度无关的低功耗振荡环设计

分析了传统片外时钟和片内时钟各自的特点和应用背景,在Chartered 0.35μm CMOS工艺下实现了一个低功耗PVT(工艺、电源电压、温度无关)振荡环,对片内时钟的稳定性和功耗进行改进。该振荡环无需精准的电压源,采用了误差补偿技术,通过偏置电压和延时单元的相互补偿,使得振荡频率对于工艺、温度和电源电压均有较大的容差能力。并且由于针对延时单元补偿的方式,令周期大小易于调整。蒙特卡罗仿真显示,工艺误差引起的偏差要比补偿前的偏差减小了60%。流片测试结果表明,在工作温度变化范围0~100°C时,振荡环输出的频率偏差为±3.22%;在电源电压变化范围为2.8~3.8 V时,振荡环输出的频率偏差为±3.36%;在电源电压3.3 V的情况下,整个芯片消耗的电流为950μA。     

物理汽相传输法生长掺钒碳化硅单晶新鲜表面的实验研究

采用SEM观察物理汽相传输(PVT)法生长掺钒SiC单晶新鲜表面时,发现有特定形状的析出相,经SIMS、SEM能谱(EDX)、XRD、台阶仪综合分析,确定析出相的主要成分是钒,且是凸起的,推断其在单晶生长降温过程中产生。     

Description of PVT behavior of an industrial polypropylene–EPR copolymer in process conditions

An experimental procedure is presented to describe the PVT behavior of multiphase polymeric materials in a wide range of cooling rates. In particular, the procedure is applied to a typical multiphase industrial polymer, that is, an industrial polypropylene–ethylene‐propylene rubber (iPP–EPR) copolymer with a small percentage of talc. The volume evolution is described combining specific volumes of different phases present in the material. All phases are described simply by thermal expansion and compressibility coefficients drawn either from the literature or from low and high temperature (i.e., below and above the iPP crystallization range) standard PVT data. Crystallization evolution of iPP is described by the Nakamura nonisothermal formulation of the Avrami–Evans crystallization kinetic model. Model parameters are identified by comparison with both standard calorimetric results and final densities of thin samples solidified during quenches conducted with cooling rates of several hundreds of K/s. It is also shown that identification of crystallization kinetic parameters by means of calorimetric data only leads to misleading results for cooling rates larger than those adopted in the calorimetric tests. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 267–278, 2001