红外热像仪的最大测温误差分析

根据红外辐射理论和红外热像仪的测温原理，考虑环境，大气，太阳等多方面影响，得出最大测温误差的计算公式，通过分析各种因素对热像仪测温误差的影响程度，讨论了减小误差的对策。     

A technique for determining surface temperatures of geometrical objects using center temperature values during cooling

An analytical approach is proposed to determine surface temperatures of objects of various geometrical shapes (e.g., infinite slab, infinite cylinder and sphere) cooled in any medium using their measured center temperature distributions. This approach utilizes the boundary condition of the third kind in transient heat transfer which is commonly encountered when 0.1相似文献   

Theoretical investigation on the mechanism of surface temperature non-uniformity formation in spray cooling

In this study, the effects of droplet velocity non-uniformity, SMD (Sauter mean diameter) distribution non-uniformity, droplet number non-uniformity, and heating power on the fluid film thickness, fluid film velocity, and surface temperature distribution were investigated, and then the surface temperature non-uniformity correlations in non-boiling regime and nucleate boiling regime were correlated. The results show that: with the decreasing of the spray parameters non-uniformity, the fluid film thickness on the heating surface becomes more uniform, and the fluid film velocity increases, thus the surface temperature non-uniformity decreases. The highest surface temperature appears in the centre of the heating surface, and the lowest is nearby the position where the fluid film appears. The droplet number non-uniformity contributes the largest portion of impact on the surface temperature non-uniformity, followed by the droplet velocity non-uniformity. The effect of droplet SMD non-uniformity is the minimal. Finally, the surface temperature non-uniformity correlations in non-boiling regime and nucleate boiling regime were correlated with a mean absolute error of 20%.     

In-situ infrared spectroscopic study of the mechanism of the low temperature selective catalytic reduction of NO surface by Mn/ bastnaesite concentrate

The Mn/bastnaesite concentrate and Mn/Al₂O₃ catalysts were prepared by impregnation method, and their NH₃-SCR denitrification performance was tested. The results showed that the Mn/bastnaesite concentrate catalyst achieved up to 95% NO conversion rate at 150 °C, and the Mn/Al₂O₃ catalyst reached 76% at 300 °C. A series of characterisation results showed that the bastnaesite concentrate can better interact with MnOx species and promote mutual dispersion compared to Al₂O₃. The Mn/bastnaesite concentrate has a stronger redox capacity, and good NH₃ and NO adsorption capacity at low temperatures. The multi-element coexistence system of bastnaesite concentrate itself is a significant advantage of its use as a carrier. In-situ Fourier transform infrared (FTIR) results showed that the Mn/bastnaesite concentrate catalyst follows an L-H mechanism throughout the reaction, with NH₄⁺ species in the Brønsted acidic site on the catalyst surface being the main reactant species. Most of NO is converted to monodentate nitrite, which is formed by bonding with Mn³⁺ provided by the supported Mn species, rare earth elements and transition metal ions contained in the carrier itself to form O–N–O–Mn³⁺ intermediates, which participate in the reaction together, and then combined with the adsorbed NH₄⁺/NH₃ species to produce N₂ and H₂O. An E-R mechanism was also present on the catalyst surface, NO participates directly in the reaction in gaseous form, and the NO [NH₂](ads) intermediate species produced by interaction with NH₄⁺ species in the acidic position of Brønsted was further decomposed to N₂ and H₂O. By comparing the reaction mechanism with the commonly used catalyst carrier Al₂O₃ for NH₃-SCR, it can be concluded that bastnaesite concentrate as a carrier not only has the performance of conventional carriers, but also has certain catalytic activity and can interact with the active components to give it excellent performance, which provides a theoretical basis for rare earth minerals as denitrification catalysts.     

An inverse estimation of surface temperature using the maximum entropy method

The maximum entropy method (MEM) is applied to estimation of surface temperature from temperature readings. The inverse heat conduction problem is reformulated for MEM and a three-phase solution method utilizing the successive quadratic programming (SQP) is addressed. Computational results by the proposed MEM are presented and compared with results by the conventional methods.     

Kinetic studies of cathode degradation as caused by ice formation in MEAs

This work investigated the impact of F/T- (Freeze/Thaw) and ICV- (Isothermal Constant Voltage) cycling on the kinetic and mass transport performance loss for a PEM (proton exchange membrane) fuel cell. The loss of electrochemically active surface area (ECSA) of the cathode electrode increased with an increasing amount for F/T and ICV cycles. Kinetic performance loss and mass transport loss were only observed for the wet conditioning point. For the dry and medium conditioning points, only kinetic loss was measured. The observed trend indicates that an increased amount of residual water promotes the degradation process.During ICV-cycling, kinetic and mass transport losses were observed for all three amounts of residual water. In comparison to the F/T results, the ICV results showed the opposite trend; the higher the amount of residual water, the lower the performance loss.Finally, it was demonstrated that only F/T-cycling leads to kinetic degradation and that ICV-cycling has a significant impact on mass transport.     

A borehole temperature during drilling in a fractured rock formation

Drilling in brittle crystalline rocks is often accompanied by a fluid loss through the finite number of the major fractures intercepting the borehole. These fractures affect the flow regime and temperature distributions in the borehole and rock formation. In this study, the problem of borehole temperature variation during drilling of the fractured rock is analyzed analytically by applying the approximate generalized integral-balance method. The model accounts for different flow regimes in the borehole, for different drilling velocities, for different locations of the major fractures intersecting the borehole, and for the thermal history of the borehole exploitation, which may include a finite number of circulation and shut-in periods. Normally the temperature fields in the well and surrounding rocks are calculated numerically by the finite difference and finite element methods or analytically, utilizing the Laplace-transform method. The formulae obtained by the Laplace-transform method are usually complex and require tedious numerical evaluations. Moreover, in the previous research the heat interactions of circulating fluid with the rock formation were treated assuming constant bore-face temperatures. In the present study the temperature field in the formation disturbed by the heat flow from the borehole is modeled by the heat conduction equation. The thermal interaction of the circulating fluid with the formation is approximated by utilizing the Newton law of cooling at the bore-face. The discrete sinks of fluid on the bore-face model the fluid loss in the borehole through the fractures. The heat conduction problem in the rock is solved analytically by the heat balance integral method. It can be proved theoretically that the approximate solution found by this method is accurate enough to model thermal interactions between the borehole fluid and the surrounding rocks. Due to its simplicity and accuracy, the derived solution is convenient for the geophysical practitioners and can be readily used, for instance, for predicting the equilibrium formation temperatures.     

Determining the infrared reflectance of specular surfaces by using thermographic analysis

Specular surfaces as glass, mirrors and metals are commonly used in solar devices and in building facades. Determining the temperature distribution of such kind of surfaces allows estimating their thermal losses and detecting hot spots and temperature gradients that provokes material stress and rupture. In this sense, thermography is a non-contact measurement technique that is capable to quickly scan and record these surface temperature distributions, but when specular materials are inspected the infrared reflectance becomes a crucial parameter. This work describes a methodology to measure the reflectance of specular materials for different incidence angles in the infrared range 8 μm–14 μm, by using a thermographic camera and an infrared radiation source. The methodology includes the analysis of errors in the estimation of the reflectance and how to select the temperature of the source that minimizes these errors. The method is applied to different specular surfaces commonly used in building facades and solar devices, whose infrared specular reflectances are estimated for different incidence angles. The obtained results are analyzed in order to provide valuable information for in-situ thermographic measurements of specular surfaces.     

秸秆成型燃料燃烧过程中炉膛温度对受热面上沉积形成的影响

秸秆燃烧过程中,受热面上沉积的形成受多种因素的影响。文章重点研究了炉膛温度对沉积形成的影响。研究表明:炉膛温度不但影响沉积的性质,而且随温度的升高,沉积中的碱金属含量上升,有利于碱金属与SiO_2结合,生成低熔点的共晶体。     

冰成天然气水合物机理分析

将冰粉与石英砂均匀混合，在一定条件下形成天然气水合物。实验研究表明冰成天然气水合物没有诱导区，开始就进入水合物的成长区。从气-固反应动力学出发，研究了冰成水合物形成机理：冰成天然气水合物过程是冰晶分子对气体分子的吸附、催化和络合相互作用的过程。     

Study on the critical conditions of ice formation for a continuous ice making system in a cooling pipe

This paper deals with a continuous ice making method which could be used to provide an ice storage system using off-peak electricity during nighttime. The critical condition for an ice blockage to occur in the cooling tube has been examined in terms of the concentration of water-propylene glycol solution and thermo-hydraulic operating parameters. The results obtained show that nondimensional correlation equations for the critical condition have been derived as a function of thermo-hydraulic parameters in the laminar and the turbulent flow regions. The equations can be used to predict whether an ice making system is operating in a continuous ice making condition or is in the ice blocking phase. © 1998 Scripta Technica. Heat Trans Jpn Res, 27(1): 74–83, 1998     

Maintaining uniform surface temperature along pipes by insulation

An analytical solution is obtained for the insulation thickness variation over a pipe to maintain a uniform outer surface temperature. A high temperature fluid is considered to be flowing through the pipe. The amount of the insulation material is assumed to be limited. Heat transfer from the outer surface of the pipe is through convection and radiation. The solution of the insulation thickness is found to be independent from the outer surface convective and radiative heat transfer coefficients. In addition, the solution is found to be very close to linear variation which is very easy to implement in practice.     

Calibration and Experimental Research of a Multiple-wavelength Flame Temperature Instrumentation System

This paper presents a study on a novel instrumentation system for the measurement of temperature distribution of combustion flames. This system operates upon the three-color principle combining advanced optical sensing and digital image processing techniques. It comprises an endoscope, a light splitter assembly, a CCD camera, a frame-grabber and associated software. This system was calibrated using a blackbody furnace as standard temperature source. The relationship between flame temperatures and grey-level of the images was established through image processing and function correlation. Experimental results obtained on a gas-fired combustion rig provide flame images and temperature distributions on three different wavelengths. Based on the flame temperature distribution the combustion conditions can be analyzed. Experimental results also reveal that this system is capable of online measurement of temperature distribution in a combustion zone. This system can potentially be applied to many areas such as power generation, metallurgy, chemical engineering. It is also a powerful tool for improving the control of combustion process.     

A new method for evaluating formation equilibrium temperature in holes during drilling

The present paper describes a method for evaluating the formation equilibrium temperature during drilling breaks. The method is based on simple graphic techniques suitable for field use and for deciding the duration of the break.     

Real-time laser-based measurement of interface temperature during droplet impingement on a cold surface

This work presents a laser-based thermoreflectance technique to measure the real-time change in temperature of a liquid-solid interface when a heated liquid droplet impinges on a transparent substrate. Temperature variation at the interface results in refractive index changes in both the liquid and substrate, which, in turn, cause a reflectivity change at the interface. A 5 mW HeNe laser and a silicon photodiode are used to monitor the real-time reflectivity of the interface. The measurement is performed with two liquids, water and glycerol, impinging onto one surface of a prism made of F2 glass, with initial liquid temperatures of 0, 25, and 45 °C above room temperature. A temporal resolution of 8.8 ms and spatial resolution of 180 μm have been achieved in this work. The measurement uncertainty is ∼3.5-6.3 °C for water and 0.5 °C for glycerol. Higher temporal and spatial resolution can be readily obtained with minor modifications to the experimental apparatus. Measurement of liquid solidification and evaporation on a substrate may also be suitable for this technique, as the phase change causes an abrupt variation in reflectivity at the interface.     

Delay of wetting propagation during jet impingement quenching for a high temperature surface

Transient heat transfer has been investigated experimentally with a subcooled water jet during quenching of hot cylindrical blocks made of copper, brass and steel for initial surface temperatures from 250 to 400 °C. The jet velocity was from 3 to 15 m/s and jet subcooling from 5 to 80 K with a jet diameter of 2 mm. When the jet strikes the hot surface, the wetting front becomes stagnant for a certain period of time in a small central region before wetting the entire surface. This wetting delay may be described as the resident time which is a strong function of block material and jet subcooling and also a function of initial block temperature and jet velocity. New correlations for the resident time and the surface temperature at the resident time at the wetting front have been proposed.     

不同壁厚对气缸套壁面温度影响的有限元分析

以某重型柴油机的薄壁顶置湿式气缸套为研究对象,结合特定热边界条件,对气缸套的稳态温度场进行了有限元分析,气缸套三维温度场的计算结果显示气缸套最高温度为239℃,出现在气缸套活塞上止点附近。通过对比不同气缸套壁厚对壁面温度场的影响,明确了气缸套的变形分析中不同壁厚对气缸套壁面温度的影响,为气缸套结构设计改进提供理论指导和依据。     

Mathematical determination of emissivity and surface temperature of aluminum alloys using multispectral radiation thermometry

A relatively simple emissivity model has recently been shown to effectively capture the parameteric effects of wavelength, temperature, alloy and surface roughness on the emissivity of aluminum surfaces. In the present study, a mathematical method is developed for determining both the empirical constant in the emissivity model and the surface temperature based on spectral radiance measurements. This study proves the relationship between reflectance ratio and optical roughness is by no means universal, and the complex effects of wavelength, temperature, alloy and surface roughness are more accurately captured with the aid of a multispectral emissivity model.     

Measuring the impact of additional instrumentation on the skill of numerical weather prediction models at forecasting wind ramp events during the first Wind Forecast Improvement Project (WFIP)

The first Wind Forecast Improvement Project (WFIP) was a DOE and NOAA‐funded 2‐year‐long observational, data assimilation, and modeling study with a 1‐year‐long field campaign aimed at demonstrating improvements in the accuracy of wind forecasts generated by the assimilation of additional observations for wind energy applications. In this paper, we present the results of applying a Ramp Tool and Metric (RT&M), developed during WFIP, to measure the skill of the 13‐km grid spacing National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) Rapid Refresh (RAP) model at forecasting wind ramp events. To measure the impact on model skill generated by the additional observations, controlled data‐denial RAP simulations were run for six separate 7 to 12‐day periods (for a total of 55 days) over different seasons. The RT&M identifies ramp events in the time series of observed and forecast power, matches in time each forecast ramp event with the most appropriate observed ramp event, and computes the skill score of the forecast model penalizing both timing and amplitude errors. Because no unique definition of a ramp event exists (in terms of a single threshold of change in power over a single time duration), the RT&M computes integrated skill over a range of power change (Δp) and time period (Δt) values. A statistically significant improvement of the ramp event forecast skill is found through the assimilation of the special WFIP data in two different study areas, and variations in model skill between up‐ramp versus down‐ramp events are found.     

Feasibility evaluation of gas-assisted heating for mold surface temperature control during injection molding process

Dynamic mold surface temperature control has the advantage of improving molded part qualities without significant increases in cycle time. In this study, a gas-assisted heating system combined with water cooling and different mold designs to achieve dynamic mold surface temperature control was established. The feasibility of using gas-assisted heating for mold surface temperature control during the injection molding process was then evaluated from experimental results. The effect of mold design as well as heating conditions including hot gas temperature, gas flow capacity, and heating time on the heating efficiency and the distribution uniformity of mold surface temperature were also studied. Results showed that as hot gas temperature and gas flow capacity increased, as well as increasing heating times from 2 s to 4 s, mold surface temperature increased significantly. Fan shaped gas channel design exhibits better mold surface temperature distribution uniformity than tube shaped gas channel design. During gas-assisted heating/cooling, it takes 2 s to increase mold surface temperature from 60 °C to 120 °C and 34 s for mold surface to return to 60 °C. In addition, under specified heating conditions and using the best composite mold designs, the heating rate can reach up to 30 °C/s, a rate well-suited to industrial applications.