Surface Temperature Of Objects Research Articles

Error analysis on measurement temperature by means dual-color thermography technique

Dual color thermography is a non-contact measurement temperature technique used mainly when the emissivity of surface is unknown; it is based on ratio of monochromatic emissive power calculated by means Planck’s radiation equation and allows measuring the temperature of gray body surface objects without being assigned their emissivity and without approximations.For real surfaces, the emissivity varies with the temperature of surface as well as the wavelength and the direction of radiation. In this case, the dual color thermometry is executed by equipping the IR camera of two narrow band pass filters, so as to consider the surface emissivity of a quite constant value. This allows calculating the ratio between the radiative fluxes of the two different emission wavelengths that is almost independent to the surface emissivity.One of the crucial factor in this technique is the choice of the two narrow filter wavelengths. In fact the measurement errors depends directly on the two wavelengths and the variation of spectral emissivity related to the wavelength chosen and it also depends inversely on distance between central value of filters.In this paper, the authors have developed and validated a mathematical model of experimental setup to measure object surface temperature by means IR thermo-camera. This mathematical model was used to quantify the temperature measurement error in the dual-color technique. A novel correlation to estimate temperature measurement error was provided.

STAND FOR TEMPERATURE SURFACE EVALUATION OF FRAGMENTS OF NATURAL ENVIRONMENTS AND ITS IMITATORS

Research in the field of development of natural environments imitators that used for thermal cloaking of military machinery always connected with high material costs due to big sizes of cloaking objects. In this way we decided to create laboratory stand and methodic for obtaining data about temperature surface of fragments of natural environments and its imitators affected by the electromagnetic radiation of the optical wavelength range. We proposed to use a thermal imaging camera instead of the traditionally used spectrophotometric equipment for obtaining spectral characteristics of the objects under study affected by the optical radiation. This method allows us to evaluate the surface temperature of the object at different angles of lighting and viewing. Obtained data allows us to estimate the degree to which the imitator corresponds to a natural environment by the temperature and it’s dynamic of change.The construction of the stand allows to select angles of source of radiation and thermal detector in range 25–75 degrees from normal to the surface of object under study. The source of radiation consists of halogen lamps of MR16 type. The number of selected lamps and its power were chosen taking into account of imitation of intensity of sun radiation.The thermal camera MobIR M4 was used as infrared detecting unit in the range of 8–12 μm. This device has a matrix with a resolution of 160 × 120 pixels and its optical field of view, both vertically and horizontally is 25 to 19 degrees. Special remotely controlled device was created to automate the process of obtaining thermal images. Proposed methodic of measuring surface temperature of objects under study consists in obtaining thermal images at equal time intervals, their analysis using special software and plotting graphs. Thus we can use the developed laboratory stand and the methodic not only for temperature surface evaluation of fragments of natural environments but for its imitators.

Exploring the effect of neighboring land cover pattern on land surface temperature of central building objects

Increased temperatures in urban landscapes bring about a variety of problems and exacerbating thermal discomfort. Many studies have focused on detecting the effects of land cover patterns, including composition and configuration, on land surface temperature (LST) using remote sensing images. This study focused on distinct land cover feature, buildings, in center of Beijing, China, exploring the relationship between the LST of central building objects and land cover patterns in their neighboring areas. Classifying buildings into three groups (low-rise, mid-rise, and high-rise) allowed the effects of neighboring land cover patterns on building LST to be analyzed independently. We found that the composition of land cover features has a stronger impact on low-rise building LST than mid-rise and high-rise building LST. Moreover, low-rise building LST is highly related to the composition of neighboring vegetation and pavement. This relationship is limited for mid-rise buildings and high-rise buildings. Finally, LST can be mitigated not only by balancing the amount of vegetation and buildings, but, for low-rise buildings, can also be mitigated by optimizing their spatial configuration. This study enhances our understanding of the degree to which LST of different height buildings are affected by neighboring land cover patterns. In addition, important insights can be provided to urban planners on how to mitigate the impact of urbanization on UHI through urban design and vegetation management.

A method for improving temperature measurement precision on the uncooled infrared thermal imager

In order to improve temperature measurement precision of the uncooled infrared thermal imager, aiming at the influence of the thermal imager internal radiation, a method is proposed based on voltage compensation in this paper. Firstly, combining the principle of uncooled infrared thermal imager, radiation of tested object is converted to voltage values, the voltage values are converted to grey value can be measured, and thus the relationship between radiation of tested object and grey value is established. Secondly, according to the relationship between radiation and grey value, a model about uncooled infrared thermal imager temperature measurement is established. A formula for computing the true surface temperature of objects is given. Coefficients are acquired in the temperature measurement formula by collecting the infrared image data of standard blackbody. Finally, in order to verify the correctness of the compensation method, an experiment about blackbody is conducted in this paper. The experiment results show that this method can effectively reduce the relative error of the thermal imager temperature measurement.

Infrared Thermography Assessment of Thermal Bridges in Building Envelope: Experimental Validation in a Test Room Setup

Thermal infrared imaging is a valuable tool to perform non-destructive qualitative tests and to investigate buildings envelope thermal-energy behavior. The assessment of envelope thermal insulation, ventilation, air leakages, and HVAC performance can be implemented through the analysis of each thermogram corresponding to an object surface temperature. Thermography also allows the identification of thermal bridges in buildings’ envelope that, together with windows and doors, constitute one of the weakest component increasing thermal losses. A quantitative methodology was proposed in previous researches by the authors in order to evaluate the effect of such weak point on the energy balance of the whole building. In the present work, in-field experimental measurements were carried out with the purpose of evaluating the energy losses through the envelope of a test room experimental field. In-situ thermal transmittance of walls, ceiling and roof were continuously monitored and each element was characterized by its own thermal insulation capability. Infrared thermography and the proposed quantitative methodology were applied to assess the energy losses due to thermal bridges. The main results show that the procedure confirms to be a reliable tool to quantify the incidence of thermal bridges in the envelope thermal losses.

Detection of Singularities and Subsurface Defects in Wood by Infrared Thermography

Infrared thermography (IRT) is a technique that allows the visualization of the surface temperature of objects from the radiation that they emit without any kind of contact. This non-destructive technique (NDT) is used worldwide for locating and identifying internal defects in materials from the thermal anomalies that these defects generate on the surface of the materials, among other applications. Two types of irregularities are found in wood: singularities and defects, which are regions of disorder that affect the quality of the wood and decrease its resistance capacity. Based on the local density variations caused by these irregularities that alter the thermodynamic behavior of the wood, the present investigation analyzed the capacity and performance of IRT for the exploration and detection of these subsurface singularities and defects in wood. The results establish the true scope of this technique in detecting subsurface defects in wood and verifying the complexity inherent in the analysis.

On-Site Identification of Zero Resistance Insulator Based on Infrared Thermal Image and Weights-Direct-Determination Neural Network

A method using infrared thermal images and weights-direct-determination neural network (WDDNN) to identify the zero resistance insulators on-site is presented. The basic procedures were as follows: the infrared thermal image were denoised, intensified, segmented, and a rectangular which was regarded as object was intercepted in the insulators chain; in view of the relationship between gray value of infrared thermal images and temperature of object surface, four parameters which stand for standard deviation, absolute deviation, quartiles and range of gray value, were extracted directly; these four parameters were used as the input of WDDNN to train the model, which could be used identifing the zero resistance insulators after being trained. This method can effectively avoid the interference of transmission lines, and can meet the real-time require when identifying on-site. Experimental results verify the feasibility and effectiveness of this method.

Design of an Intelligent De-Icing System for Offshore Structures

The offshore activities in cold waters have moved from shallow to deep sea waters, which require different operations as compared to activities in hot sea water. Such offshore operations in cold regions like arctic may be effected by the ice accretion on deck and other areas of structure. Ice mainly accretes from both sea spray and atmospheric icing, which can create problems for operational environment and safety of people working on offshore structures in cold regions. In this research a lab based experimental study has been carried out to preliminary design and test an intelligent thermal anti/de-icing system. The experimental study was carried out in cold room chamber of Narvik University College, where temperature can be well controlled between +10 to-30 °C. The proposed intelligent thermal based deicing system can be used to control the communication between icing sensors, weather station, heating devices and central control unit. In this preliminary design phase, a simple surface temperature control method has been developed and tested that can further provides an efficient thermal deicing method and will also be capable to control the surface temperature of objects of interest in cold regions

Temperature and emissivity determination of small-size long-range object’s using staring Thermovision Cameras

The possibilities and limitations of remote temperature and emissivity coefficient determination of small-size distant objects in the condition of spatially distributed background illumination using measurements of the electronic signals of infrared images formed by Thermovision Cameras with staring FPA’s have been studied. It is shown that the expression for the total video signal amplitude measured from a “point” image of the object in the presence of a background consists of several components, of which the decisive role is played by the signals from the object and the illuminating background. The conditions and constraints providing an analytical solution of obtained four equations have been defined and the expressions for determination of the absolute thermodynamic temperature and emissivity coefficient of a small-size object surface have been obtained.

Determination of the Emissivity of Wood for Inspection by Infrared Thermography

Infrared thermography (IRT) is a non-contact technique for visualizing the surface temperature of objects based on the radiation emitted. Recently, this non-destructive technique (NDT) has begun to be used for the diagnosis and evaluation of wood structures. In the process of transforming radiant energy into temperature, which is performed by thermographic devices, one of the most significant properties that affects the calculation of temperature is the emissivity of the material being analyzed. Prior knowledge of the emissivity is essential for a thermographic inspection because it quantitatively determines the amount of energy that is actually produced by the material. In this research study, the emissivity of different types of wood has been determined, and the influences of temperature and surface finish of the samples on the emissivity values have been analyzed.

Temperature Grid Sensor for the Measurement of Spatial Temperature Distributions at Object Surfaces

This paper presents results of the development and application of a new temperature grid sensor based on the wire-mesh sensor principle. The grid sensor consists of a matrix of 256 Pt1000 platinum chip resistors and an associated electronics that measures the grid resistances with a multiplexing scheme at high speed. The individual sensor elements can be spatially distributed on an object surface and measure transient temperature distributions in real time. The advantage compared with other temperature field measurement approaches such as infrared cameras is that the object under investigation can be thermally insulated and the radiation properties of the surface do not affect the measurement accuracy. The sensor principle is therefore suited for various industrial monitoring applications. Its applicability for surface temperature monitoring has been demonstrated through heating and mixing experiments in a vessel.

Research on the Method of Working-Out near Ground Air Temperature Based on Low Altitude Remote Sensing Aerial Data

In the thermal environment which influences people's life, air temperature 1.5m high is the most important and direct. Through remote sensing we can quickly get the object surface temperature. But the air temperature can’t be got through it directly. [1]If we can excogitate the method of working-out the air temperature 1.5m high from the altitude remote sensing aerial data, the relate research on the urban thermal environment will be convenient and efficient. This paper is written to research this method and analyze the feasibility by means of analysing the relationship between the radiation brightness temperature, the underlay surface temperature and the air temperature 1.5m high.

Acoustothermometrical control during hyperthemia of biological objects

A number of acoustothermometrical experiments modelling hyperthermia of biological objects was carried out. After that the first preliminary acoustothermometrical measurement of laser hyperthermia of human tissues was conducted. In all experiments the changes of the thermal acoustic radiation intensity in 1.4-2.2 MHz region were controlled during both the heating and the cooling of the object (about 8-10 minutes) with the help of set of acoustothermometers. As model objects we used the beef liver and glycerin water solution in which plasticine was placed. We reconstructed the 2-D inner temperature distribution by using acoustothermometrical experimental data, i.e. we calculated position, size and temperature of thermal source. The object surface temperature was controlled with the help of IR-thermograph. Acoustothermometrical measurements were carried out during laser hyperthemia of mammary and thyroid glands for seven patients. Obtained data allowed us to estimate inner temperature changes which were a result of laser hyperthemia.

Three‐band temperature extraction from airborne imagery with imprecise atmospheric knowledge

The accurate estimation of an object's surface temperature from airborne imagery is complicated by several factors, including the effects of the atmosphere and surface emissivity variations. Several methods have been proposed to handle specific cases where some of the unknowns can be eliminated. Typically, these methods use one or two spectral bands or viewing geometries and are applied to large, homogeneous surfaces where the surface emissivity may be approximated as a blackbody. In particular, a method using two spectral bands for sea surface temperature estimation with the advanced very high resolution radiometer (AVHRR) sensor has shown success while removing the need for an estimate of the atmospheric upwelling radiance. Here this method is extended to include a third spectral band and is applied to terrestrial targets. The algorithm has been tested against a synthetically generated scene containing a wide variety of targets. Temperature estimation capabilities are modestly improved (∼1 K) by inclusion of the third spectral band, particularly for materials with low emissivity and when using midwave infrared measurements. Sensitivity studies demonstrate that the inclusion of the third band slightly decreases the sensitivity of the algorithm to knowledge of the atmospheric transmission and downwelling radiance. This is true even for stressing cases such as hot targets and man‐made materials with low emissivity. It is also shown, for both methods, that precise knowledge of the downwelling radiance is the least significant input parameter for accurate surface temperature estimation for targets with high emissivities, resulting in errors less than 1 K for errors in downwelling radiance of up to 35%.

On the applicability of Kirchoff’s law and the principle of heat balance in thermal infrared remote sensing: A non-isothermal system

This paper proposes a basic equation of thermal radiation interaction between surface objects on the basis of the principle of heat balance in the interface. The solution of this equation takes account of the contribution of sensible heat flux and latent heat flux more completely, compared with traditional solution for surface cooling and heating processes. By the aid of the experimental data conducted in the Xiaotangshan experimental site, Beijing, both the non-applicability of Kirchoff’s law and the measurability of surface emissivity in a non-isothermal system have been highlighted. Two methods called ventilation and time-delay compensations have been proposed to reduce the error induced by change of surface temperatures of non-isothermal objects during the measurement of emissivity. Based on the solution of the basic equation, this paper has analyzed and pointed out the misunderstanding in comprehension and application of Kirchoff’s law published in literature.

Fluorescence temperature sensing on rotating samples in the cryogenic range

A surface temperature measurement technique for rotating samples is proposed. It is based on the concept of fluorescence thermometry. The fluorescent and phosphorescent phenomena have been applied in thermometry for ambient and high-temperature measurement but not the cryogenic domain, which is explored using thermocouple- or platinum resistor-based thermometers. However, thermal behavior of Yb2+ ions in fluoride matrices seems to be interesting for thermometry in the range 20–120 K. We present here a remote sensing method which uses fluorescence behavior of Yb2+ ion-doped fluoride crystals. The fluorescence decay time of such crystals is related to its temperature. Since we developed a specific sol–gel process (OrMoSils) to make strongly adherent fluorescent layers, we applied the fluorescence thermometry method for rotating object surface temperature measurement. The main application is the monitoring of surface temperature of the ball bearing or turbopump axis in liquid propulsion rocket engines. Our method is presented and discussed, and we give some experimental results. An accurate calibration of the decay time of CaF2:Yb2+ versus temperature is also given.

An approach for determining surface temperature distributions of solid objects subjected to heating applications

This study presents a simple technique of determining surface temperature values and/or distributions of solid objects of various geometrical shapes (e.g. infinite slab, infinite cylinder, and sphere) during heating in a medium under natural or forced convection conditions. In the model, the boundary condition of the third kind (i.e., 0.1 < Bi < 100) in transient heat transfer, which is commonly encountered, is used. In many practical applications ranging from metallurgy to food engineering processes, the measurement of surface temperatures of such solid objects is a remarkable problem ; however, centre temperature measurements are quite easy. For this reason, simple and accurate models are required for use in practice. The proposed model depends on the centre temperature and determines the surface temperatures using the centre temperature measurements. In order to test the present analytical model, an actual example for a slab object was given and the centre and surface temperature profiles were drawn. In addition, the centre and surface temperature distributions for infinite slab, infinite cylinder, and sphere were computed for the values of 0.1, 1, 10, and 100 of the Biot number and were exhibited as reference graphics. As a result, the present model is capable of determing surface temperatures of various geometrical objects heated in any medium using their centre temperature measurements in a simple and accurate manner.

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< Bi<100 . In industrial applications, surface temperature measurements of such objects are difficult and require excessive instrumentation and operations, as well as more instrumentation time. In addition they may not be as accurate as desired. However, the measurement of center temperatures is easy and inexpensive making this technique more common. Determination of the surface temperature distribution is required for a variety of industrial applications from metal-quenching to cooling food products. This study shows that the proposed approach is capable of determining surface temperatures of various geometrical objects, subjected to cooling, using their measured center temperature data in a simple and accurate manner

Utility of the 4.6- to 4.9-um atmospheric window for remote sensing of background temperature

A field measurement program was initiated to determine the utility of the 4.6- to 4.9-μm spectral region as a remote temperature sensing channel. A spectroradiometer (covering the 1.3- to 14-μm region) was used to determine effective surface temperatures of various natural objects both in the 4.6- to 4.9-μm and the commonly used 10.5- to 12.5-μm regions. Comparisons of the effective temperatures obtained from both short-range (30 to 300 m) and long-range (3 to 10 km) measurements are presented. For measurements at short ranges, the deduced effective temperature for each region wascompared with contact temperature measurement of the surface. For measurements over long ranges, the effective temperatures were compared after having accounted for path radiance effects. Accurate path radiance corrections were made from measurements over the tail region of the 4.3-μm CO₂ absorption band.

Theoretical analysis of Heat and Mass Transfer Phenomena during Fluidized Bed Sublimation

ABSTRACT This work present. a detailed study of heat and mass transport phenomena between a large sublimable object and a gas-solid fluidized bed of either inert or adsorbent fine panicles. Heat (h) and mass (k)transfer coefficients are related to the size and adsorption capacity of the fine particles, as well as to the diameter of the spherical immersed object and to the bed temperature. Convective and conductive components are also identified, and correlations are proposed to predict all of them. The significant differences which appear for the various working conditions may be accounted for considering the particular mechanisms that prevail in every case. A simple renewal model clearly shows the leading role of the object surface temperature. For adsorbent panicles, a local overheating phenomenon at the exchange surface is demonstrated.