Determining the heat flux absorbed by satellite surfaces with temperature data

This study aims to determine the heat flux absorbed by satellite surfaces with the use of temperature data acquired from the satellite. This process is the first step in the development of an attitude determination method, which is currently being conducted by the authors. The principles of heat flux determination and its limitations are explained. A simple heat flux sensor is proposed in this study to address such limitations. With sufficient temperature data, an inverse solution of the energy equation can be used to determine the heat fluxes absorbed by heat flux sensors. The accuracy of the method depends on the resolution of the sensors used to acquire temperature data. The effects of temperature sensor resolution on the accuracy of the results are discussed in this paper.     

热沉冷却式薄壁量热计设计及分析

为满足大当量战斗部热毁伤威力评估的需求,弥补传统薄壁量热计在爆炸场环境中易变形、易烧蚀的不足,采用在热敏元件后壁面添加热沉体的方式,设计一种新型热沉冷却式热流密度传感器,以间接测量的方式,通过热敏元件后壁面温度,获得入射热流密度。建立传感器理论模型,推导响应时间表达式,并对传感器响应特性进行数值仿真,仿真结果显示:传感器响应时间只与热敏元件的尺寸和材料有关,与热沉体无关。以0.5 mm紫铜作为热敏元件的传感器响应时间可达1.2 ms左右;热沉体吸热系数越大,热敏元件温升越小,同时,随着时间的增加,温升速率逐渐减小。验证试验显示,热沉体的加入可有效降低热敏元件温升,所设计传感器可正确反映入射热流变化。     

Characterization of a heat flux sensor using short pulse laser calibration

A method to calibrate classical heat flux sensors is presented. The classical approach to measure the temperature inside a known material by using a thermocouple fails when the measurement time is very short. In this work the surface heat flux is determined by solving the inverse heat conduction problem using a noninteger identified system as a direct model for the estimation process. Using short pulse laser calibration measurements the crucial design aspects of the sensor that play a significant role when assuming one-dimensional, semi-infinite heat transfer have been accounted for. The theoretical approach as well as the calibration results are presented and comparisons to the classical approach and results from finite element modeling are shown. It is concluded that the new method ameliorate the heat flux sensor significantly and extend its application to very short measurement times.     

流动沸腾条件下微通道壁面温度的红外特征

设计并搭建了沸腾换热试验台,采用TH5104红外热像仪测量微通道壁面温度来研究混合制冷工质在微通道内的沸腾换热特性.测量试件是一外径为1.22 mm,内径为0.86 mm,长为200 mm的不锈钢单圆管.实验利用红外热像仪测量并记录下质量流量为1 726～8 635 kg/m2·s,热流密度为65～231 kW/m2时壁面温度的变化情况.实验分析和讨论结果显示:微通道壁面的温度分布沿着轴向变化有明显的规律性;水平微尺度通道内流动沸腾过程中,试件前后段有较大的温差效应,温差的正负与热流密度的大小有关;壁面温度的变化与热流密度、管内工质的流型和换热形式关系密切,流型越复杂,壁面温度变化越剧烈.     

Agilent34972A在温度传感器检测系统中的应用

为了解决批量生产热量表温度传感器并对其进行配对的问题,在深入研究其特性的基础上,应用Agillent 34972A数据采集器建立了温度传感器检测系统.该系统基于VC语言环境,应用VISA库编程驱动仪器进行测量并读取数据,并且编制了对检测温度传感器获得的数据进行处理和配对的应用程序.研究结果证明,使用Agilent 34...     

Gardon型热流传感器隔热技术的优化

在无法向外散热的情况下,采用Gardon型热流传感器测量火焰强度的热流密度时,传感器对于热量的处理只能选择用储热体来吸收,故该类型的传感器有了工作时间的限制.为增加Gardon型热流传感器的工作时间,对其隔热技术加以改进,效果较为明显.     

On the contribution of primary deformation zone-generated chip temperature to heat partition in machining

In machining, the percentage of heat flux that enters the cutting tool can have a critical impact on tool wear especially in dry cutting or high speed machining. In previous work, heat partition was evaluated by iteratively reducing the secondary deformation zone heat flux to the tool until the finite element simulated temperatures matched the experimental measured rake face temperatures. This follow-on work quantifies the contribution of primary zone heat flux to heat partition in machining. In this study, an analytical model was used to evaluate the rise in chip temperature due to primary deformation zone heat source. The heat partition and thermal modelling on the rake face was then conducted with an appropriate initial rake face temperature. Thus primary zone heat loads and shear-force-derived secondary zone heat flux were applied in finite element transient heat transfer analysis to evaluate heat flux into the cutting tool. External dry turning of AISI/SAE 4140 with tungsten carbide-based multilayer TiCN/Al₂O₃-coated tools was conducted for a wide range of cutting speeds between 314 and 879 m/min. Results further support the dominance of secondary zone heat flux on heat partition. The contribution of primary zone heat generation to the cutting tool heat flux in machining was less than 9.5 %. These findings suggest that, to address the thermal problem in machining, research and development should also focus on reducing friction on the rake face (e.g. coating innovations) and reducing contact areas (e.g. rake face design) in addition to the modification of shear angle and hence primary zone heat intensity.     

Performance evaluation of coaxial thermocouple against platinum thin film gauge for heat flux measurement in shock tunnel

Data on surface heat flux is critical in all hypersonic missions due to the extent of risk and the penalty associated, when it is not properly accounted for. In the present study an E-type coaxial thermocouple has been designed, fabricated, validated and benchmarked against a more established platinum thin film sensor. The study proves that coaxial thermocouples used in impulse facilities do not require cold junction compensation. The comprehensive study conducted in IIT Bombay Shock Tunnel (IITB-ST) has confirmed the performance, ruggedness and reliability of the coaxial thermocouple, ascertaining it to be an effective, impulse, heat flux sensor.     

Surface thermocouples for measurement of pulsed heat flux in the divertor of the Alcator C-Mod tokamak

A novel set of thermocouple sensors has been developed to measure heat fluxes arriving at divertor surfaces in the Alcator C-Mod tokamak, a magnetic confinement fusion experiment. These sensors operate in direct contact with the divertor plasma, which deposits heat fluxes in excess of ~10 MW/m(2) over an ~1 s pulse. Thermoelectric EMF signals are produced across a non-standard bimetallic junction: a 50 μm thick 74% tungsten-26% rhenium ribbon embedded in a 6.35 mm diameter molybdenum cylinder. The unique coaxial geometry of the sensor combined with its single-point electrical ground contact minimizes interference from the plasma/magnetic environment. Incident heat fluxes are inferred from surface temperature evolution via a 1D thermal heat transport model. For an incident heat flux of 10 MW/m(2), surface temperatures rise ~1000 °C/s, corresponding to a heat flux flowing along the local magnetic field of ~200 MW/m(2). Separate calorimeter sensors are used to independently confirm the derived heat fluxes by comparing total energies deposited during a plasma pulse. Langmuir probes in close proximity to the surface thermocouples are used to test plasma-sheath heat transmission theory and to identify potential sources of discrepancies among physical models.     

A Peltier cell calorimeter for the direct measurement of the isothermal entropy change in magnetic materials

We developed a calorimetric technique to measure the isothermal magnetocaloric entropy change. The method consists in the use of Peltier cells as heat flow sensor and heat pump at the same time. In this paper, we describe the setup, the constitutive equations of the Peltier cell as sensor and actuator, and the calibration procedure. The Peltier heat is used to keep the sample isothermal when magnetic field is changed. The temperature difference between the sample and the thermal reservoir is kept by a digital control within 5 mK for a magnetic field rate of 20 mT s(-1). The heat flux sensitivity around 1 microW. With this method, it is possible to measure the magnetocaloric effect in magnetic materials by tracing the curves of the exchanged entropy Delta(e)s as a function of the magnetic field H. The method proves to be, in particular, suitable to reveal the role of the entropy production Delta(i)s, which is connected with hysteresis. Measurement examples are shown for Gd, BaFe(12)O(19) ferrite, and Gd-Si-Ge.     

Investigation of tool-chip interface temperature in dry turning assisted by heat pipe cooling

Aiming to effectively remove the cutting heat in machining process, the cutting tool with heat pipe cooling has been developed in recent years; however, there were few reports on the quantitative investigation of temperature at the tool-chip interface of this tool. In this work, a heat pipe cooling system was used to decrease the temperature of the cutter. The temperature at defined locations of the cutter in the dry turning of an AISI-1045 steel was obtained by the cutting test. The finite difference solution and an inverse procedure were used to determine the tool-chip interface temperature. It was found that with the increase of cutting speed, the tool-chip interface temperature and effective heat flux of the cutter will increase. The tool-chip interface temperature could be reduced by the heat pipe cooling. The temperature reduction was more obvious in higher cutting speed.     

飞机短舱环境温度飞行试验及某飞机试飞结果分析

发动机作为热机械装置其产生的大量的热以热辐射、对流方式传递给发动机附件及其舱内的飞机附件,造成发动机舱内的热环境。如果舱内环境温度较高,会导致附件损坏或者异常。因此试飞中舱温成为必要的测量和考核参数。本文建议通过短舱中加装环境温度测量的方法进行考核,建议了传感器的选型、加改装等。最后,列举了某型飞机短舱环境温度试飞,结果表明该测量、测试方法可行、可靠。     

On a MEMS based dynamic remote temperature sensor using transverse vibration of a bi-layer micro-cantilever

In this paper a novel remote temperature sensor based on a bi-layer micro cantilever beam has been proposed, which can sense the temperature of a given heat source from a finite distance dynamically. Proposed sensor works based on radiation heat transfer and thermally induced vibration. In order to dispose a relationship between temperature of the heat source, and a sensible characteristic like as tunneling current or capacitance, thermo-mechanical behavior of such a structure has been investigated. Heat transfer equation of such a beam includes a nonlinear term due to the radiation heat transfer that has been solved numerically using Rung-Kutta explicit integration method. Galerkin based mode summation method has been utilized to solve the partial differential equation of the beam dynamics and the Houbolt implicit integrating method is used to solve obtained ordinary differential equations. Dynamic response to a step, and semi-harmonic excitations and frequency responses, for the proposed sensor with different geometrical or physical properties have been presented and discussed considering the temperature relaxation time of the sensor. In order to gain a semi explicit solution a perturbation method has been disposed and the results have been compared to the numerical direct integration ones, the accuracy and agreement are excellent.     

A study on the unsteady temperature field of combustion chamber wall in a turbocharged gasoline engine

To design and develop a turbocharged engine, it is necessary that a lot of studies should be done to find the chrracteristics of engine performance and thermal flow. To accomplish this purpose, turbocharger equipped to a naturally aspirated gasoline engine was utilized. A thin-film type temperature probe was made and installed onto the combustion chamber wall to measure unsteady temperature. The unsteady heat flux at combustion chamber wall was evaluated by one dimensional unsteady conduction equation.     

水火弯板温度场理论分析和数值模拟

水火弯板工艺是船体外板弯曲的一项关键的流程,前人对钢板的温度场已进行过相关的研究。高斯热源热流密度模型被广泛用于水火弯板的温度场的分析,其参数的选取和定义,是水火弯板数值模拟中一个关键问题。本文采用高斯热源热流密度模型对水火弯板中的气体火焰热源和钢板的温度场展开了研究,并提出了高斯热源热流密度模型的不足和改进方法。     

某型航空发动机燃-滑油热交换器模态试验中传感器布点优化策略

对某型航空发动机燃-滑油热交换器实物测量分析的基础上,在有限元软件ABAQUS中建立了其结构有限元模型并进行了模态分析。根据遗传算法原理,构造了一种基于正整数编码的改进遗传算法,利用Matlab编程完成了算法的实现,采用该方法对热交换器模态试验中传感器布点方案进行了优化,得到了传感器对应于其初始布置模式下的优化布置方案。     

热处理设备的温度测控系统设计

本文从温度测试系统设计角度介绍了传感器的选用原则。成功运用智能PID解决了结构和参数不完全掌握的被控对象问题,该智能PID同时也解决了一个不具有精确数学模型的温度控制问题。较好地解决了因热处理工艺更改而对热处理设备改造的实际问题。     

热处理设备的温度测控系统设计

本文从温度测试系统设计角度介绍了传感器的选用原则。成功运用智能PID解决了结构和参数不完全掌握的被控对象问题，该智能PID同时也解决了一个不具有精确数学模型的温度控制问题。较好地解决了因热处理工艺更改而对热处理设备改造的实际问题。     

巨磁阻传感器在管道漏磁检测中的应用

磁性传感器在无损检测中已经有了很大的应用，与传统的磁性传感器相比，巨磁阻传感器有着灵敏度高、可靠性好、测量范围宽、体积小，价格低等优点。介绍了巨磁阻传感器及其在输油管道缺陷漏磁信号检测中的应用，表明采用巨磁阻传感器的检测系统可以检测到管道壁上的微小缺陷。     

Fiber Bragg grating temperature sensor for practical use

Fiber Bragg grating (FBG) is a promising measurement technology for future sensor system applications. Little attention has been given to the FBG sensor housing, however it is important that the FBG is embedded in a conventional electrical sensor housing so that it may be installed easily in instrumentation systems. We have experimentally fabricated a practical pass-through type FBG temperature sensor which is embedded in the conventional thermocouple housing. A small radius U-turn fiber spliced to the FBG is placed inside the top of a stainless sheath. Employing a high numerical aperture fiber with polyamide recoating, we have determined that the bending loss of the small radius U-turn fiber and heat resistance is less than 0.1 dB and up to 250 degrees C respectively. The wavelength shift of this sensor due to temperature change is 10.3 pm/degrees C equal to that of general FBG. Consequently the practical use of this sensor has been confirmed.