红外热像术与节能

<正> 1.什么是红外热像术红外热像术就是通过红外传感器接收处在一定距离的目标发出的红外辐射,再通过电子线路、光学转换变成目标的视频热图像,对这种热图像可以录像或摄制成照片,这种技术简称红外热像术。所制成录像或照片称为热像图。对于黑白热像图来讲,色调亮的地方表明温度高,越亮温度越高,相反,较暗的地方温     

点加热稳态导热系数测量方法研究

针对稳态导热系数测量方法测量过程时间较长、测量装置复杂、以及样品制备和加工工艺复杂等现状,提出了一种新型的点加热稳态导热系数测量方法,构建相应的三维稳态传热物理模型,使加热面温升只与热流密度、样品导热系数和测温点位置相关。通过聚焦连续激光加热样品,缩短样品达稳态时长至分钟量级;建立对照光路消除表面发射率和激光稳定性对温度测量的影响;红外热像仪测量加热表面稳态温度分布,结合物理模型实现导热系数测量。采用多种已知导热系数的标准材料和线性法对测量方法进行验证,并应用该方法测量硅藻土导热系数为0.49～0.60 W/(m·K),误差为6.06%。该方法的测量迅速及非接触特性使其可应用于工程实地测量。     

离散孔气膜冷却效果的红外热像测量方法

基于红外测温技术,建立了常温环境中的平板气膜冷却性能试验台,设计了 一种离线红外测温的标定方法,解决了实验中红外测量窗口,即红外玻璃受热后的辐射对标定的影响.通过与热敏液晶测量结果对比,证明测量窗口自身热辐射造成的测量误差正比于测量温度与气流温度的偏差,通过标定可以消除该误差,达到与热敏液晶一致的精度.     

变温变粘度小工质流量的测量

本文介绍用半导体硅力敏器件测量小工质流量的方法及装置。这种测量不受工质温度、粘度等状态的影响,可用于太阳能平板和聚光集热器的热性能试验,测量各种介质在不同状态下的流量。     

平板类零件平面度平行度的测量

本文以阀板为例介绍了一种平板类零件平面度平行度的测量方法，着重介绍了其测量原理以及相适应的机械测量装置。本测量系统可一次装夹同时测量出平板类零件的两个平面度参数和两平面互为基准的平行度参数，具有被测参数测量值显示、超差警示、测量结果显示等功能。     

热管式均热平板的研究与应用

本文描述了热管技术在均热平析牟温度场控制中的应用，利用数值计算方法均热平析有效工作表面的温度进行了传热计算，得到了均热平板有效工作表面内的最大温差随平板工作温度、平板厚度方向上的圆孔直径和孔间距等影响因素的变化关系，为实际应用提供了可靠的理论依据。     

优化FET-Raman的数值分析法以快速测量界面热导

使用稳态拉曼光谱测量纳米材料的热特性，往往需要精确校准拉曼位移温度系数和测量激光吸收系数，使用瞬态拉曼光谱方法可以避免这两个步骤的误差。使用了一个新的非线性拟合方法，可以显著加快频域能量传输状态分辨拉曼(FET-Raman)的数据处理。为模拟不同热特性材料的传热过程，结合有限元分析(FEA)和非线性拟合过程取代了多个耗时的有限元分析，以获得与测量数据相比较的理论值。使用这种方法测定了多层MoS₂和石英玻璃之间的界面热导，结果表明，这种测量方法准确、快速且易于实施。     

太阳辐射下不同地表覆盖物的热反应及对城市热环境的影响

该文利用红外热像仪等设备研究了建筑物表面、绿地、柏油路面、水泥砖地面等城市地表覆盖物对太阳辐射的热反应，指出在同一天中，柏油路面温度最高，水泥砖和建筑物表面次之，绿地温度最低。通过分析各种覆盖物在城市中所占比例，得出建筑物对城市热环境影响较大的结论，并提出了改善城市热环境的几种方法。     

磷酸铁锂电池内阻连续动态测量与分析

磷酸铁锂电池内阻测量目前大多存在耗时长、测量结果不连续等问题。文章提出一种新型的内阻测量方法——双倍率曲线法。基于该方法,对不同温度下电池内阻进行测量并进行误差分析。结合误差分析结果发现,该测量方法的适用放电状态（state of discharge, SoD）区间为5% ~ 90%。对该区间内平均内阻与温度之间的关系进行定量分析,得到平均内阻随温度变化的关系式。相比于以往的其他测量方法,该方法的提出能够有效缩短内阻测量时耗,可为在线内阻测量的实现提供一定的研究基础。     

发动机活塞温度测量方法综述

综述了活塞温度测量方法的两大类型:电测法(热电偶法、非接触互感式测量方法和红外遥测法)和非电测法(硬度塞法和易熔合金法)现状及其发展,分析了各种测量方法的工作原理和应用范围。热电偶法是所有现代活塞温度测量法的基础,红外遥测法和互感式测量方法适用高速发动机的活塞温度测量,硬度塞法和易熔合金法因简单可靠、成本低而得到广泛应用。     

Estimation of temperature dependent heat transfer coefficient in a vertical rectangular fin using liquid crystal thermography

This paper presents a methodology for the estimation of temperature dependent heat transfer coefficient for a vertical rectangular fin by using the inverse heat transfer method with Liquid crystal thermography (LCT) data. Steady state, laminar natural convection experiments have been done on a vertical rectangular fin of size 150 × 250 × 4, (L × w × t, all dimensions are in mm). The variation of heat transfer coefficient is considered as a power law function of temperature excess (h = a_oθ^b) and is derived from the basic Nusselt number equation used for laminar natural convection, Nu = aRa^b. With this functional form, the one dimensional fin equation in finite difference form is repeatedly solved using the Gauss–Seidel iterative method. Treating this as a one parameter estimation in ‘a’ the sum of the squares of the difference between the simulated and Thermochromic Liquid Crystal (TLC) measured temperatures is minimized with the Golden section search algorithm to retrieve ‘a’. Estimate of ‘a’ and the accompanying uncertainties are first reported for synthetically generated temperature distribution for assumed values of ‘a’. The effect of noise on the estimate of ‘a’ is discussed. This is followed by retrievals with experimentally obtained TLC temperature distribution for a range of heat inputs to the fin base. The required temperature distributions for accomplishing the retrievals over the surface are obtained using calibrated R40C5W Thermochromic Liquid Crystal (TLC) sheets. As an additional proof of the accuracy of the method, the retrieved value of ‘a’ is used to simulate the temperature distribution in the fin which is then compared with the actual TLC measured temperature distribution.     

Numerical prediction of film cooling effectiveness over flat plate using variable turbulent prandtl number closures

Numerical simulations were performed to predict the film cooling effectiveness on the fiat plate with a three- dimensional discrete-hole film cooling arrangement.The effects of basic geometrical characteristics of the holes,i.e.diameter D,length L and pitch S/D were studied.Different turbulent heat transfer models based on constant and variable turbulent Prandtl number approaches were considered.The variabiUty of the turbulent Prandtl number Pr_t in the energy equation was assumed using an algebraic relation proposed by Kays and Crawford,or employing the Abe,Kondoh and Nagano eddy heat diffusivity closure with two differential transport equations for the temperature variance kg and its destruction rate ε_θ.The obtained numerical results were directly compared with the data that came from an experiment based on Transient Liquid Crystal methodology.All implemented models for turbulent heat transfer performed sufficiently well for the considered case.It was confirmed,however,that the two- equation closure can give a detailed look into film cooling problems without using any time-consuming and inherently unsteady models.     

Utilization of the cryogenic exergy of liquid natural gas (LNG) for the production of electricity

Liquid natural gas (LNG) delivered by means of sea-ships is compressed and then evaporated before its introduction to the system of pipelines. The possibilities of the utilization of cryogenic exergy of LNG for electricity production without any additional combustion of any its portion, have been analyzed. Three variants of the plant have been investigated. A cascade system with two working fluids has been analyzed in two first of them. The economic optimization proved that the optimum temperature difference in the LNG evaporation is higher than initially assumed. Therefore, a third variant of the plant has been analyzed, with ethane as a single working fluid. Only the third variant has been analyzed in detail.     

An experimental investigation of film cooling performance of louver scheme

An experimental investigation of the film cooling performance of louver schemes using Thermochromic Liquid Crystal technique is presented in this paper. The louver scheme allows the cooling flow to pass through a bend and encroach with the blade material (impingement effect), then exit to the outer surface of the aerofoil through the film cooling hole. The cooling performance of the louver scheme was analyzed for blowing ratios ranging from 0.5 to 1.5 and for a density ratio of 0.94. The results showed that the louver scheme enhances the local and the average film cooling effectiveness, and the net heat flux reduction better than other published film hole configurations. The louver scheme also provides a wide extensive spread of the secondary flow over the outer surface, thus enhancing the lateral film cooling performance over the downstream surface area. Moreover, the louver scheme produces a lower heat transfer ratio than other film hole geometries at low and high blowing ratios. As a result, the louver scheme is expected to reduce the gas turbine airfoil’s outer surface temperature by provide superior cooling performance than other film cooling schemes hence increasing the airfoil life time.     

A direct borohydride-peroxide fuel cell-LiPO hybrid motorcycle prototype: Investigation of short-term behavior of DBPFC stack – I

In the present study, a safer and more performance 270?W Direct Borohydride/Peroxide Fuel Cell (DBPFC) Stack has been constructed for an electrical hybrid motorbike application. Performance tests were carried out with single cell and 5–10–25?cell stacks. Performance loss has been not observed while stacking DBPFC because of the Independent Cell Liquid Distribution Network (ICLDN) system and special bipolar plate design. The power densities have been approximately 120?mWcm^?2 for a single DBPFC and 25-cell DBPFC stack without any stacking loss. Additionally, the stack temperature has been controlled by keeping the oxidant concentration low, and it has been maintained at approximately 52?°C without using a cooling system. The short-term performances of the 25-cell DBPFC stack have been tested over 25?min and 50?min, which showed that the performance and stack security of the DBPFC are highly related to the oxidant properties, such as the concentration, temperature and feed type.     

Bipolar plate research using Computational Fluid Dynamics and neutron radiography for proton exchange membrane fuel cells

This work presents the development of liquid-cooled industry-scale bipolar plates for improved water management in PEM Fuel Cells. The methods used for the design development are based on Computational Fluid Dynamics (CFD) modelling and simulation, and Neutron Radiography experiments to analyse liquid water distributions within the cell for different operating conditions.A novel 140 cm² bipolar plate was designed and manufactured on 0.1 mm thick stainless steel using pre-coated strip steel. CFD modelling carried out for the novel design predicted a significant improvement in terms of cell performance, as well as a more uniform temperature distribution within the membrane. Liquid water distributions were later analysed by neutron radiography experiments, defining a set of different operating conditions (current density, stoichiometry, inlet gases dew point, and cell temperature).Electrochemical and neutron radiography results are presented for all cases and the influence of the operating conditions is discussed. Liquid water distributions within the cell are also analysed and compared against the CFD model results obtained. The influence of the gas flow configuration (reactant gases and cooling water) is clearly observable in the results.     

Optimized Emission-based Reciprocity Monte Carlo Method to speed up computation in complex systems

An Optimized Emission-based Reciprocity Monte Carlo Method (OERM) has been developed and validated by comparison, in benchmark cases, with analytical reference results. In this method, the frequency distribution function, generally equal to the emission distribution function at the emitting cell temperature, has been replaced by a distribution function associated with the maximum temperature within the domain. The real emission distribution function of a cell at any temperature is then obtained by applying a corrective factor to each shot.     

Experimental study of heat transfer enhancement using water/ethylene glycol based nanofluids as a new coolant for car radiators

Traditionally forced convection heat transfer in a car radiator is performed to cool circulating fluid which consisted of water or a mixture of water and anti-freezing materials like ethylene glycol (EG). In this paper, the heat transfer performance of pure water and pure EG has been compared with their binary mixtures. Furthermore, different amounts of Al₂O₃ nanoparticle have been added into these base fluids and its effects on the heat transfer performance of the car radiator have been determined experimentally. Liquid flow rate has been changed in the range of 2–6 l per minute and the fluid inlet temperature has been changed for all the experiments. The results demonstrate that nanofluids clearly enhance heat transfer compared to their own base fluid. In the best conditions, the heat transfer enhancement of about 40% compared to the base fluids has been recorded.     

Temperature rise of an induction motor during plugging

The problem of three-dimensional transient heat flow in the stators of induction motors is solved using a finite-element formulation employing arch-shaped elements. The shape functions and exact solutions are derived algebraically for the utmost economy in computation. The temperature distribution has been determined considering convection from the surface and the two ends. The temperature distribution has also been determined by specifying the temperature of the surface and the ends. A simple cylinder is used as an example. The temperature at different locations in the stator of the induction motor has been computed during transients     

Analysis of the effect of viscous dissipation for laminar flow in stadium-shaped ducts

The fully-developed laminar forced convection of a Newtonian fluid in a duct with stadium-shaped cross section has been analyzed. The effect of viscous dissipation has been taken into account. Three different thermal boundary conditions have been considered: (T) uniform wall temperature distribution; (H1) axially uniform wall heat flux distribution with peripherally uniform wall temperature distribution; (H2) axially and peripherally uniform wall heat flux distribution. The adiabatic-wall boundary condition has also been analyzed as a special case of the H2 boundary condition. The velocity and temperature distributions in the fluid, as well as the Fanning friction factor and the Nusselt number, have been evaluated numerically, by employing a Galerkin finite element method. As expected, the numerical evaluation of the dimensionless temperature distribution and of the Nusselt number reveals that increasing discrepancies between the H1 and H2 boundary conditions exist if the stadium-shaped duct is gradually flattened.