Autonomous Sensor System With Power Harvesting for Telemetric Temperature Measurements of Pipes

In this paper, an autonomous sensor system, with low-power electronics for radio-frequency (RF) communication, incorporating a thermoelectric energy-harvesting module for unattended operation is presented. A target application is proposed for temperature measurement of walled-in pipes. When the autonomous sensor is placed on the heat source, a thermoelectric module harvests energy, powering the autonomous sensor. In this condition, no external power source is necessary, the temperature measurement is performed, and the data are saved into a nonvolatile memory. When the external readout unit is active, the electromagnetic field is used to power the autonomous sensor system and to communicate the data. An experimental setup has been arranged and characterized by measuring the temperature along the pipe, the voltage that can be generated by thermoelectric generators, and the influence of different materials on RF communication. The temperature data of the heat source, which are collected by the autonomous sensor, are compared with that of a reference thermistor. The measurement results show good agreement between the two measured temperature data sets. The experimental data demonstrate that the autonomous system works correctly for a temperature gradient that is higher than 9degC, within a readout distance of a few centimeters. The presented autonomous sensor system can be effectively used for measurements into a close environment in which a temperature difference is present.     

Thermoelectric cooling of microelectronic circuits and waste heat electrical power generation in a desktop personal computer

Thermoelectric cooling and micro-power generation from waste heat within a standard desktop computer has been demonstrated. A thermoelectric test system has been designed and constructed, with typical test results presented for thermoelectric cooling and micro-power generation when the computer is executing a number of different applications. A thermoelectric module, operating as a heat pump, can lower the operating temperature of the computer's microprocessor and graphics processor to temperatures below ambient conditions. A small amount of electrical power, typically in the micro-watt or milli-watt range, can be generated by a thermoelectric module attached to the outside of the computer's standard heat sink assembly, when a secondary heat sink is attached to the other side of the thermoelectric module. Maximum electrical power can be generated by the thermoelectric module when a water cooled heat sink is used as the secondary heat sink, as this produces the greatest temperature difference between both sides of the module.     

三维脉动热管耦合相变材料的传热与节能特性研究

为研究三维脉动热管与相变材料耦合系统的传热与节能特性,本文搭建了三维脉动热管/相变材料耦合模块实验台,使用甲醇、乙醇和丙酮3种工质对充液率为34％、44％的三维脉动热管进行研究,建立了耦合模块的热阻模型,定义了耦合模块的热阻变化率;研究了在变送风温度(3～9 m/s)和速度(20～26℃)条件下耦合模块的热阻变化规律和...     

采用相变蓄热模块多联式空调（热泵）系统除霜过程的试验研究

空调采用传统除霜方法对系统性能带来不利影响。本文通过试验研究采用相变蓄热模块的多联式空调（热泵）系统除霜过程的动态特性,并与常规的逆循环除霜方法进行对比。试验结果表明：在除霜、大湿度除霜和低温制热3种工况下,蓄热除霜的制热量比常规除霜时略高,整机的消耗功率基本相同,室内换热器的制热周期基本一致,但除霜期间室内机停机时间缩短一半;蓄热除霜除霜期间室内换热器盘管温度比常规逆循环除霜高20-25℃,蓄热除霜除霜期间室内换热器出风口温度比常规逆循环除霜高13-17℃,大大提高室内环境的舒适性。这表明相变蓄热除霜空调（热泵）系统除霜性能优于传统逆循环除霜空调（热泵）系统。     

A study of accurate latent heat measurement for a PCM with a low melting temperature using T-history method

When the latent heat of a phase change material (PCM) with a lower melting point than ambient temperature was assessed according to the standard T-history method using a vertically oriented test tube, a temperature gradient occurred in the longitudinal direction of the tube due to natural convection. This led to a decrease in the accuracy of the latent heat of fusion measurement. In this study, the accuracy of the measurement with the original T-history method was improved without decreasing the test's simplicity and convenience by setting the test tube horizontally. The heat transfer to the vapor-layer of the tube under volume change during melting was assumed to be negligible and the results were calculated using the two inflection points of temperature as the start and end of latent heat period. Under these assumptions, the results agree closely with other reference data. And, the new method proposed in this study showed a remarkable reduction in data scattering.     

Integration of dye-sensitized solar cells, thermoelectric modules and electrical storage loop system to constitute a novel photothermoelectric generator

This study self-develops a novel type of photothermoelectric power generation modules. Dye-sensitized solar cells (DSSCs) serve as the photoelectric conversion system and a copper (Cu) heat-transfer nanofilm coating on both sides of the thermoelectric generator (TEG) acts as a thermoelectric conversion system. Thus module assembly absorbs light and generates electricity by DSSCs, and also recycles waste heat and generates power by the TEG. In addition, a set of pulsating heat pipes (PHP) filled with Cu nanofluid is placed on the cooling side to increase cooling effects and enhance the power generation efficiency. Results show that when the heat source of thermoelectric modules reaches 90 degrees C, TEG power output is increased by 85.7%. Besides, after thermoelectric modules are heated by additional heat source at 80 degrees C, the electrical energy generated by them can let a NiMH cell (1.25 V) be sufficiently charged in about 30 minutes. When photothermoelectric modules is illumined by simulated light, the temperature difference of two sides of TEG can reach 7 degrees C and the thermoelectric conversion efficiency is 2.17%. Furthermore, the power output of the thermoelectric modules is 11.48 mW/cm2, enhancing 1.4 % compared to merely using DSSCs module.     

Measuring the Electrothermal Efficiency of a 50-Hz Plasma Torch

This study concerns the measurement of electrothermal efficiency in an ac plasma torch. It was found that the best method of measuring arc input power was an electronic system involving multiplication and integration although thermal wattmeters could be used with a slight loss of accuracy. A self-jacketed parallel flow calorimeter was found best for measuring the heat content of the torch output. The flow-dependent thermal efficiency of this torch was found to exceed 60 percent. For established designs of torch the electrode losses can be used to establish the input power to the arc, and thus eliminate the need for an electrical measurement.     

无引线温度测量模块设计

针对温度场测量中使用常规温度传感器引线不方便的缺点,设计了一套无引线温度测量模块。该模块具有测量精度高、无需引线、使用方便的特点。测量模块配接热电阻传感器,利用参考电阻比例测量技术,大大提高了测量稳定性。测量模块采用真空隔热蓄热技术,在-65~200℃温度范围内正常工作不少于2 h,可满足该温区真空试验罐、热压罐,或其他密闭试验装置、大空间实验装置等温度场均匀性测量的需求。     

Modelling Strategies for Property Identification Based on Full‐Field Surface Displacement Data

Abstract: The use of full‐field displacement measurements in mechanical testing provides detailed response information that can be used, in conjunction with modelling and optimisation, for precise material property identification. One limitation of this technique is that the collection of response data and the sectioning of a specimen to reveal the material microstructure are both destructive tests and mutually exclusive, as the displacement measurement occurs only on the exposed surface. Therefore, modelling of an experiment to interpret a full‐field experiment requires assumptions about the structure of the material below the visible surface. This study evaluates the effects of several possible modelling assumptions on the errors in model‐predicted response and on the resulting material property estimates. A 3‐D microstructural model, for which the subsurface grain geometry and orientations are known, provides the basis for comparison of several common modelling assumptions based on the grain geometry and orientations on the visible surface of a specimen.     

Strain‐induced crystallization in rubber: A new measurement technique

The crystallinity of stretched crystallizable rubbers is classically investigated using X‐ray diffraction. In this study, we propose a new method based on temperature measurement and quantitative calorimetry to determine rubber crystallinity during mechanical tests. For that purpose, heat power density are first determined from temperature variation measurements and the heat diffusion equation. The increase in temperature due to strain‐induced crystallization is then deduced from the heat power density by subtracting the part due to elastic couplings. The heat capacity, the density, and the enthalpy of fusion are finally used to calculate the crystallinity from the temperature variations due to strain‐induced crystallization. The characterization of the stress–strain relationship and the non‐entropic contributions to rubber elasticity is not required. This alternative crystallinity measurement method is therefore a user‐friendly measurement technique, which is well adapted in most of the mechanical tests carried out with conventional testing machines. It opens numerous perspectives in terms of high speed and full crystallinity field measurements.     

Effects of modelling assumptions on the rating calculation for externally forced cooled high-voltage cables

To increase the rating of a high-voltage cable circuit the cable group can be externally forced cooled, using additional coolant pipes in proximity to the buried cable group. This complicates modelling of the heat transfer problem to obtain ratings as coolant temperature and therefore heat transfer coefficient varies along the cable route. The most common approach for obtaining the circuit rating is the finite difference (FD) method outlined in Electra 66. This method is computationally efficient and quick to solve. To investigate the assumptions underlying this approach and provide confidence over a range of model parameters, this paper presents the development of an extended 2-D heat-transfer finite element method (FEM) model. The ratings of two cable circuits have been modelled using this approach and are compared with results from Electra 66. Cable ratings from the two methods are consistent in trend but offset favourably by 2.6% using the FEM model for all burial depths tested. With the FEM model verified for standard assumptions the model provides a useful tool for rapid investigation of sensitivity to model assumptions. A sensitivity analysis to changes in AC resistance, burial depth, dielectric loss, soil thermal resistivity and surface boundary condition is presented.     

Virtual welding equipment for simulation of GMAW processes with integration of power source regulation

A two dimensional transient numerical analysis and computational module for simulation of electrical and thermal characteristics during electrode melting and metal transfer involved in Gas-Metal-Arc-Welding (GMAW) processes is presented. Solution of non-linear transient heat transfer equation is carried out using a control volume finite difference technique. The computational module also includes controlling and regulation algorithms of industrial welding power sources. The simulation results are the current and voltage waveforms, mean voltage drops at different parts of circuit, total electric power, cathode, anode and arc powers and arc length. We describe application of the model for normal process (constant voltage) and for pulsed processes with U/I and I/I-modulation modes. The comparisons with experimental waveforms of current and voltage show that the model predicts current, voltage and electric power with a high accuracy. The model is used in simulation package SimWeld for calculation of heat flux into the work-piece and the weld seam formation. From the calculated heat flux and weld pool sizes, an equivalent volumetric heat source according to Goldak model, can be generated. The method was implemented and investigated with the simulation software SimWeld developed by the ISF at RWTH Aachen University.     

Isothermal calorimetry: impact of measurements error on heat of reaction and kinetic calculations

Heat flow and power compensation calorimetry measures the power generation of a reaction via an energy balance over an appropriately designed isothermal reactor. However, the measurement of the power generated by a reaction is a relative measurement, and calibrations are used to eliminate the contribution of a number of unknown factors. In this work the effect of the error in the measurement of temperature of electric power used in the calibrations and the heat transfer coefficient and baseline is assessed. It has been shown that the error in all aforementioned quantities reflects on the baseline and it can have a very serious impact on the accuracy of the measurement. The influence of the fluctuation of ambient temperature has been evaluated and a means of a correction that reduces its impact has been implemented. The temperature of dosed material is affected by the heat loses if reaction is performed at high temperature and low dosing rate. An experimental methodology is presented that can provide means of assessment of the actual temperature of the dosed material. Depending on the reacting system, the heat of evaporation could be included in the baseline, especially if non-condensable gases are produced during the course of the reaction.     

A Laser Microcalorimeter

A new type of microcalorimeter as the laser power standard in Japan has been developed at the Electrotechnical Laboratory. This is a double calorimeter in which the laser power is measured by a dc substitution method using the thermopile unit, and simultaneous measurement is also made using the Peltier cooling-type calorimeter by dc substitution. The CW power of the gas laser (He-Ne) is controlled with high stability (±0.05 percent) by the automatic power control system using the Faraday rotation component. By this method and equipment, the "effective efficiency" of the standard thermopile unit is determined precisely. The errors in this microcalorimetric technique are investigated with the aid of heat flow analysis and auxiliary experiments. As a result, the absolute accuracy of the CW power measurement of laser beams (6328?, 1.15?) is evaluated with high accuracy better than 0.5 percent. The experiments have been successful at 6328? and 1.15 ?, and this method is considered to be available at the region of infrared and far-infrared wavelength.     

Simultaneous Measurement of Thermal Conductivity and Specific Heat in a Single TDTR Experiment

Time-domain thermoreflectance (TDTR) technique is a powerful thermal property measurement method, especially for nano-structures and material interfaces. Thermal properties can be obtained by fitting TDTR experimental data with a proper thermal transport model. In a single TDTR experiment, thermal properties with different sensitivity trends can be extracted simultaneously. However, thermal conductivity and volumetric heat capacity usually have similar trends in sensitivity for most materials; it is difficult to measure them simultaneously. In this work, we present a two-step data fitting method to measure the thermal conductivity and volumetric heat capacity simultaneously from a set of TDTR experimental data at single modulation frequency. This method takes full advantage of the information carried by both amplitude and phase signals; it is a more convenient and effective solution compared with the frequency-domain thermoreflectance method. The relative error is lower than 5 % for most cases. A silicon wafer sample was measured by TDTR method to verify the two-step fitting method.     

Pulse Transient Method as a Tool for the Study of Thermal Properties of Solar Cell Laminating Films

The paper reports a study on the possible influence of surroundings on thermal properties of various types of laminating films used in the design of photovoltaic (PV) modules based on crystalline silicon. The main purpose of cell encapsulation is to provide protection of PV panels against environmental damage (especially humidity). However, the laminating film can influence also the electrical behavior of the whole panel because of differences in the working temperature. It is well known that with increasing solar cell temperature the PV conversion efficiency is decreasing. Therefore, it is important to study the thermophysical properties of laminating foils which are used for PV cells encapsulation. These materials must possess low specific heat and high thermal conductivity. Therefore, by using a laminating film with low absorption, high thermal conductivity, and high emissive ability of the rear (not illuminated) side, the PV module working temperature can be lowered and thus the generated power is increased and the investment recovery time shortened. The method of measurement is relative. The goal is not to determine the thermophysical parameters of laminating foils, but only to compare the influence of selected types of laminating foils on heat flow from the PV panel. A planar heat source placed between two PMMA blocks with defined thermal properties was adopted as the model of a real PV panel. A measurement on real PV panels was carried out by thermal imaging with a thermocamera. The correlation between both measurements was found.     

Development of a modular single-phase grid-tie inverter system for fuel-cell power generation

To enhance the conversion efficiency and electrical reliability of the low-voltage fuel-cell (FC) power generation system, this paper proposes a modular single-phase grid-tie inverter system equipped with a power management and remote monitoring interface. In this system, each single power module is composed of three single-stage quasi-resonant (QR) flyback current-source inverters that are connected in parallel, and all the power modules are connected in parallel to achieve flexible power scaling and load sharing. The proposed grid-tie inverter system possesses a power management unit (PMU) and can be integrated with a home energy management system (HEMS). An experiment was conducted to verify the feasibility of the proposed concept, in which five power modules were assembled to form a 1-kW high-efficiency grid-tie inverter system, which was modulated through the PMU. The results showed satisfactory load-sharing characteristics between the parallel-connected power modules. The peak efficiency for each power module and the overall power generation system are about 94.5 and 90%, respectively. The proposed system exhibits flexible power scaling, load sharing, and high reliability.     

A simple and effective load-pull system for RF power transistorlarge-signal measurements for wireless communication power amplifierdesign

Conventional load-pull methods for RF power transistor large-signal measurements usually need complicated RF measurement instrumentation. A simple load-pull measurement setup and a test procedure with IEEE-488 GPIB control and data acquisition capability has been developed. This is used to facilitate the design of an RF power amplifier (PA) for wireless communication applications. Compared with the conventional load-pull method, it is simpler and less costly, yet effective. Measured examples of Siemens GaAs FET's CLY-2 and CLY-10, which are used to design a RF PA module for ISM-band (902-928 MHz) wireless communications, are presented     

储能锂电池模组SoE运行区间评估方法研究

为提高电池储能单元控制精度,保证储能系统高效稳定运行,研究了储能锂电池模组能量状态（state of energy,SoE）运行区间。在分析跟踪计划发电、风光功率平滑运行模拟工况,以及电池电压极差、电池电压标准差系数等评估指标的基础上,提出了储能锂电池模组SoE运行区间评估方法。然后,对实际运行的锂电池模组进行了跟踪计划发电、风光功率平滑模拟工况试验,并通过分析电池电压极差、电池电压标准差系数的变化,确定了2种运行工况下锂电池模组的SoE运行区间。研究结果表明,采用分析模拟工况试验中电池电压极差、电池电压标准差系数的方法能有效评估储能锂电池模组的SoE运行区间,为提高储能单元能量利用率提供了技术手段,对于保证锂电池储能系统高效稳定运行具有指导意义。     

新型布雷登塔式太阳能热发电系统

太阳能热发电通常以水工质吸热作为第1代,以熔盐吸热作为第2代,以空气、超临界二氧化碳或固体粒子作为介质的布雷登循环系统称为第3代太阳能热发电系统。通过采用空气或陶瓷粒子作为吸热介质,采用干热存储介质（如耐火砖和陶瓷材料等）进行规模化储热,能提高系统效率和降低成本,系统的储热能力可保证电站在任何时候都按照电网调度要求发电。采用标准化模块设计,通过工厂化制作,使电站设计、设备生产、安装、调试和运行都大为简便,储存的热量可用于食品加工、干燥、农业应用等。根据美国能源部的研究,具有储热功能的模块配备小型燃气型透平可实现快速启停,改善电网电压和频率质量。