Thermovision Technique Research Articles

Moisture Determination for Fine-Sized Copper Ore by Computer Vision and Thermovision Methods.

The moisture of bulk material has a significant impact on the energetic efficiency of dry grinding, resultant particle size distribution and particle shape, and conditions of powder transport. This research aims to develop computer vision and thermovision techniques for the on-site estimation of moisture content in copper ore, for use, e.g., in dry grinding installations. The influence of particle size on the results of moisture estimation is also studied. The tested granular material was copper ore of particle size 0-2 mm and relative moisture content of 0.5-11%. Both vision and thermovision images were taken at standard and macro scales. The results suggest that median-intensity vision images monotonically reflect copper ore moisture in the range of about 0.5-5%. Suitable models were identified and cross-validated here. In contrary, thermograms should not be analyzed simply for their mean temperature but treated with computer vision processing algorithms.

Excited State Absorption for Ratiometric Thermal Imaging.

Luminescence thermometry, an alternative to thermal imaging using the thermovision technique, requires the development of new approaches and a thorough understanding of the physical phenomena involved, in order to improve the temperature readout parameters. A phenomenon that has recently been shown to cause an extremely strong increase in the emission intensity for the temperature elevation is the thermally induced excited state absorption. This work demonstrates that taking advantage of the strong thermal dependence of the thermally induced excited state absorption process, the limitation associated with the two thermally coupled excited levels usually involved in the ratiometric temperature readout can be overcome, improving the thermometric properties of the luminescent thermometer. The same excitation wavelength was used to induce the emission resulting from the thermally induced excited state absorption of the Tb3+ ions and ground-state absorption of the other type of co-dopant ions causing the opposite nature of the thermal dependence of their emission intensities. Moreover, thanks to the strong color changes exhibited by the phosphors, it was possible to demonstrate the applicability of the proposed approach for through-object 2D thermal imaging of a microelectronic printed circuit board covered with a glass plate using an ordinary commercial digital camera, where the thermovision camera fails.

Measurement of Temperature Distribution Within Steel Box Girder of Vistula River Bridge in Central Europe

Uneven temperature distribution in a structural element constitutes one of its load factors. Temperature fields occurring in structural elements lead to stresses and strains. The values of internal stresses are directly related to temperature distribution and degree of freedom for element deformation. The best way to get information about temperature distribution in an element is to take measurements on a real object. Such measurements have been run or are still taken over decades in various parts of the world, e.g. in Western Europe, USA, China, South America. In a number of cases, such examinations were carried out for objects constructed in warm or hot climate. It is a lot harder to find the results of measurements made in the countries with moderate and transitional climate, like in the Central or East-Central Europe. This paper presents measurement methodology and results gained for a large steel bridge located in the East European Plain, about 52.5° N northern latitude. Permanently installed contact sensors, temporary sensors, as well as pyrometry and thermography were used. An attempt was made to determine temperature distribution in a steel box girder of a bridge using thermovision technique. Approximate temperature distribution patterns in the main span girder were determined from thermal photographs taken. The most important results of examinations are the images of temperature fields in the main span girder related to solar radiation that first and foremost directly affects the bridge deck.

Experimental investigation of thermal bridges in building at real conditions

In recent time the energy consumption of buildings may be reduced by the application of modern technologies in the construction industry. Modern building materials ensure a reduction of heat losses. However, studies show that thermal bridges may cause up to 30% of the additional heat losses through the building envelope. Therefore, a one key aspect in assessing the real thermal state of buildings is the identification of the heat losses through thermal bridges. The analytical, experimental and numerical methods are used for the assessment of thermal transmittance value of building. In the paper the authors present the experimental research on heat losses through the building under real winter conditions. Infrared thermovision technique has been used to the thermal bridges assessment in situ. IR thermography technique allowed the determination of the influence of thermal bridges on the additional heat losses. For the obtaining the surface emissivity the measurements have been also performed with the use of thermocouples system. Numerical validation of the experimental results has been performed.

Validation of quantitative IR thermography for estimating the U-value by a hot box apparatus

Energy saving plays a key role in the reduction of energy consumption and carbon emission, and therefore it is essential for reaching the goal of the 20-20-2020 policy.In particular, buildings are responsible of about 30% of the total amount of Europe energy consumption; the increase of their energy efficiency with the reduction of the thermal transmittance of the envelope is a point of strength with the actions and strategies of the policy makers.Currently, the study of energy performance of buildings is based on international standards, in particular the Italian one allows to calculate the U-value according the ISO 6946 or by in-situ measurements, using a heat flow meter (HFM), following recommendations provided in ISO 9869.In the last few years, a new technique, based on Infrared Thermography (IRT) (also referred to as Infrared Thermovision Technique - ITT), has been proposed for in situ determination of the thermal transmittance of opaque building elements. Some case studies have been reported.This method has already been applied on existing buildings, providing reliable results, but also revealing some weaknesses.In order to overcome such weak points and to assess a systematic procedure for the application of IRT, a validation of the method has been performed in a monitored environment.Infrared camera, the heat flow meter sensors and a nearby meteorological station have been used for thermal transmittance measurement. Comparison between the U-values measured in a hot box with IRT as well as values calculated following international standards and HFM results has been effected. Results give a good description of the advantages, as well as of the open problems, of IR Thermography for estimating the U-value.Further studies will help to refine the technique, and to identify the best operative conditions.

Evaluation of temperature values in mental foramen area in case of patients using removable partial dentures

The purpose of the research was an evaluation of removable partial dentures (RPDs) influence on temperature values registered in the area of mental foramen. Initial assumption was made that temperature is proportional to blood flow in mental artery. Additionally, the research objective was an assessment of application of infrared thermovision technique in the field of dental prosthodontics. Two independent groups of patients were examined. Test group consisted of 30 patients using RPD, and control group was composed of 33 patients partially edentulous in mandibular dental arch. The mean age in the test group was 68.8 years, standard deviation (SD) = 10.6, whereas in control group 62.3, SD = 11.9. Temperature values were recorded with thermovision camera. Test group patients underwent two examinations (with denture and 45 min after denture removal), and control group patients were examined once. Results showed decreased temperature values in case of test group patients. The differences were statistically significant (p < 0.05); however, the dentures negative influence was transient as 45 min after RPD removal temperature values were similar in both groups.

Use of infrared camera in energy diagnostics of the objects placed in open air space in particular at non-isothermal sky

The important task of the energy sector is to look for the ways of increasing energy efficiency of energy installations. This can be achieved by reducing heat losses. The thermovision technique is a very useful tool in this area. Owing to thermovision inspections it is possible to find the places with excessive heat losses as well as to determine them quantitatively. During the thermovision measurements it is necessary to know the temperature of the surroundings of considered object. A considerable group of energy installations are the objects placed in open air space. In such a case the surroundings constitute the ground and sky which are usually of different temperatures. During infrared inspections only one ambient temperature has to be entered into the camera system. The aim of this work was to develop a method for determination of equivalent ambient temperature representing thermally the surroundings of the object exposed to open air space. The use of long-wave infrared camera for sky temperature measurement has been proposed to carry out this task. Additionally, it has been proposed to use the aforementioned measurement results for the determination of total sky radiation temperature which is useful for radiative heat losses calculation.

A comprehensive experimental approach for the validation of quantitative infrared thermography in the evaluation of building thermal transmittance

Quantitative thermography is now mostly accepted as a reliable method to measure energy performance of existing buildings, in particular the thermal transmittance U-values of opaque elements. Some researches have been conducted in this field, each presenting a different procedure verified by the application on simple case studies. Anyway, a comprehensive approach, based on a parametric analysis of walls with different typologies and exposure, but same boundary conditions, is still missing. This study proposes a systematic approach to the problem, based on a three years research activity carried on an experimental building where timber (light) and brick (heavy) structures were tested simultaneously with Infrared Thermovision Technique (ITT), also equipped with heat flow meter (HFM) sensors and a nearby meteo station. Standard deviation of U-values measured with ITT is given as well as absolute deviation against values calculated following international standards and measured with HFM method. Parameters having high significance for the achievement of good results compared to the expected U-values are assessed through a sensitivity analysis. Influence of weather conditions during the survey are also considered and a repeatable procedure is finally set up. The findings presented in the study show that the method gives good results for heavy constructions, while further studies are still needed for light and super-insulated walls.

Validation and Test-Retest Reliability of New Thermographic Technique Called Thermovision Technique of Dry Needling for Gluteus Minimus Trigger Points in Sciatica Subjects and TrPs-Negative Healthy Volunteers.

The aim of this study was to assess the validity and test-retest reliability of Thermovision Technique of Dry Needling (TTDN) for the gluteus minimus muscle. TTDN is a new thermography approach used to support trigger points (TrPs) diagnostic criteria by presence of short-term vasomotor reactions occurring in the area where TrPs refer pain. Method. Thirty chronic sciatica patients (n=15 TrP-positive and n=15 TrPs-negative) and 15 healthy volunteers were evaluated by TTDN three times during two consecutive days based on TrPs of the gluteus minimus muscle confirmed additionally by referred pain presence. TTDN employs average temperature (T avr), maximum temperature (T max), low/high isothermal-area, and autonomic referred pain phenomenon (AURP) that reflects vasodilatation/vasoconstriction. Validity and test-retest reliability were assessed concurrently. Results. Two components of TTDN validity and reliability, T avr and AURP, had almost perfect agreement according to κ (e.g., thigh: 0.880 and 0.938; calf: 0.902 and 0.956, resp.). The sensitivity for T avr, T max, AURP, and high isothermal-area was 100% for everyone, but specificity of 100% was for T avr and AURP only. Conclusion. TTDN is a valid and reliable method for T avr and AURP measurement to support TrPs diagnostic criteria for the gluteus minimus muscle when digitally evoked referred pain pattern is present.

Surge Arrester Faults and Their Causes at EThekwini Electricity

Failures in polymeric housed surge arresters have recently increased. This has resulted in a number of studies being done in order to establish the condition of surge arresters whilst in service, the aim being to remove them from service before they failed. This paper utilizes a thermovision technique to predict potential faults allied to a visual inspection of arresters placed in eThekwini outdoor substations. Infrared analysis was valuable in obtaining sufficient information on arrester failures by detecting hotspots within the arresters while still connected to the system and comparing these test results with those performed on failed units. During the visual internal inspection of arresters evidence of punctures, treeing, tracking and moisture masks were noted on ZnO blocks and seals. 

Assessment of the thermal emissivity value of building materials using an infrared thermovision technique emissometer

Following international standards concerning energy performance of buildings, in absence of reliable data on the envelope characteristics, thermal transmittance of building elements should be measured in situ. The method commonly used, based on ISO recommendations, is the heat flow meter measurement method. An alternative approach is based on the infrared thermovision technique (ITT). In this case, actual thermal emissivity value of the surface finishing material is paramount to obtain the true value of the surface temperature. Several methods and instrumentations are available for laboratory measurement of emissivity of materials, whose values can be even retrieved in databases. In this study a novel method for a direct evaluation of the emissivity of common building finishing materials by means of ITT is presented, using a portable instrument affording a comparatively fast but still quite accurate procedure. The laboratory experimental results, referring to six different building materials, provide promising indications on the possibility of applying the methodology to on site tests, so taking into account real material conditions, like environmental pollution, aging, laying mode.

Thermovision techniques for evaluation of the effect of hippotherapy on changes in lower limb temperature in children with cerebral palsy (CP) – a pilot study

AbstractIntroduction: of the study. The elevated muscle tension in lower limbs (LL) in children with cerebral palsy (CP) results in the abnormal pressure on major blood vessels. Consequently, this leads to the disturbances in the circulatory system and a reduction in the temperature in lower limbs. This study assesses thermal effects of a single-session hippotherapy in LL in CP children by means of a non-invasive thermovision technique. Materials and methods: The study included 9 children with CP aged 11,8 ± 4,5 who were treated with hippotherapy. A thermovision camera was used for measurements of the temperature on the surface of lower limbs in anterior, posterior, lateral and medial parts before and after the hippotherapy. Results: The increase in the temperature was observed in the areas of lower limbs which remain directly in contact with the horse’s body. The Wilcoxon test (p&lt;0,01) revealed statistically significant changes in the temperature of the posterior regions in lower limbs. Conclusions: Hippotherapy causes an increase in the temperature of lower limbs in the areas directly involved in contact with the horse’s body. When continuing the study, the factors required for positive effects of the hippotherapy, such as the quality of the therapy and patient’s activation should also be taken into consideration.

Development and experimental evaluation of a thermography measurement system for real-time monitoring of comfort and heat rate exchange in the built environment

A measurement system based on infrared (IR) thermovision technique (ITT) is developed for real-time estimation of room thermal variations and comfort conditions in office-type environment as a part of a feasibility study in the EU FP7 project ‘INTUBE’. An IR camera installed on the ceiling allows thermal image acquisition and post-processing is performed to derive mean surface temperatures, number of occupants and presence of other heat sources (e.g. computer) through detecting algorithms. A lumped parameter model of the room, developed in the Matlab/Simulink environment, receives as input the information extracted from image processing to compute room exchanged heat rate, air temperature and thermal comfort (PMV). The aim is to provide in real time the room thermal balance and comfort information for energy-saving purposes in an improved way with respect to traditional thermostats. Instantaneous information can be displayed for the users or eventually used for automatic HVAC control. The system is based on custom adaptation of a surveillance low-cost IR system with dedicated radiometric calibration. Experimental results show average absolute discrepancies in the order of 0.4 °C between calculated and measured air temperature during a time period of a day. A sensitivity analysis is performed in order to identify main uncertainty sources.

Non-Destructive Method of Measurement of Radio Transmitters Antenna Systems

The paper deals with possibilities of use of thermovision technique in diagnostics of aerial systems of radio transmitters. Graphically presented: heating characteristic of the junction at the transmitter power of 60 % (slack and polluted junction); relationship between temperature of connection (feeder – line, capacitor frame) spacing collar and power; relationship between temperature rise amount of connection and feeder line upon power; thermogram of the junction feeder line – spacing collar, capacity frame; thermogram of the junction feeder line – spacing collar.

Infrared thermovision technique for the assessment of thermal transmittance value of opaque building elements on site

Due to new regulations in the field of energy saving, international standards concerning energy requirements of buildings have been developed. In this field, during the design phase, one of the most important parameters to be considered is the value of heat losses coefficient through the envelope. Anyway, very often a great difference is experienced between predicted performance of building elements as calculated using the methods prescribed in technical standards, and the one considering as-build conditions, particularly in the field of building renovation where the envelope thermal transmittance value must be measured on site. Till now, the only method accepted by international standards is the heat flowmeter (HFM) that presents some restriction and some uncertainty in the results. In this study a faster and less invasive method is proposed, the infrared thermovision technique (ITT) whose full potentiality has never been investigated yet, in order to acquire quantitative data of real thermal transmittances of the building envelope in a quasi-steady state condition. The theoretic background is presented together with the application in three case studies. The results indicate that, following a specific methodology, it is possible to record significant data useful to perform a proper assessment of energy performance of existing buildings.

Intelligent Thermographic Diagnostic Applied to Surge Arresters: A New Approach

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper describes a methodology that aims to extract information to enable the detection and diagnosis of faults in surge arresters, using the thermovision technique. Thermovision is a non-destructive technique used in diverse services of maintenance, having the advantage not to demand the disconnection of the equipment. The methodology uses a digital image processing algorithm based on the Watershed Transform to get the segmentation of the surge arresters. By applying the methodology is possible to classify surge arresters operative condition in: faulty, normal, light, and suspicious. The computational system generated train its neuro-fuzzy network by using a historical thermovision data. During the train phase, a heuristic is proposed in order to set the number of networks in the diagnosis system. This system was validated by a database with a hundreds of different faulty sceneries. The validation error of the set of neuro-fuzzy and the automatic digital thermovision image processing was about 10%t. The diagnosis system described has been successfully used by Electric Energy Research Center as a decision making tool for surge arresters fault diagnosis. </para>

Design and Optimization of S-Type Thermal Cutoffs

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A design and optimization procedure for S-type thermal cutoffs is presented in this paper. This type of cutoff is widely used for thermal protection of windings in motors and transformers and in boiling systems. Cutoff temperature is determined by the melting point of the alloy which is used for breaking the electrical circuit. A method for obtaining phase diagrams for ternary alloys by using 3-D surface modeling was developed. Composition of the ternary alloys for the desired melting point could be obtained by using this method. Construction of the thermal cutoffs for 95 <formula formulatype="inline"> <tex Notation="TeX">$^{\circ }{\hbox {C}}$</tex></formula> and 138 <formula formulatype="inline"><tex Notation="TeX">$^{\circ }{\hbox {C}}$</tex></formula> temperatures in terms of thermal, electrical, and mechanical properties is described. Design and optimization were carried out by using finite-element analysis (FEA) method for 3-D simulation of the devices' steady-state and transient behavior in coupled thermal and electrical domains. Technology for the production of experimental samples is also described. Characterization of the devices was done by using the thermovision technique and reasonable agreement with the simulation results was found. Further optimization steps based on the experimental data are suggested. </para>

APPLICATION POSSIBILITIES OF THERMOVISION TECHNIQUE IN DIAGNOSTICS OF AERIAL SYSTEMS OF RADIO TRANSMITTERS

The paper deals with possibilities of use of thermovision technique in diagnostics of aerial systems of radio transmitters. Graphically presented: heating characteristic of the junction at the transmitter power of 60 % (slack and polluted junction); relationship between temperature of connection (feeder ‐ line, capacitor frame) spacing collar and power; relationship between temperature rise amount of connection and feeder line upon power; thermogram of the junction feeder line - spacing collar, capacity frame; thermogram of the junction feeder line ‐ spacing collar.

Application Possibilities of Thermovision Technique in Diagnostics of Aerial Systems of Radio Transmitters

Abstract The paper deals with possibilities of use of thermovision technique in diagnostics of aerial systems of radio transmitters. Graphically presented: heating characteristic of the junction at the transmitter power of 60 % (slack and polluted junction); relationship between temperature of connection (feeder ‐ line, capacitor frame) spacing collar and power; relationship between temperature rise amount of connection and feeder line upon power; thermogram of the junction feeder line ‐ spacing collar, capacity frame; thermogram of the junction feeder line ‐ spacing collar.

Thermograms of damages

This paper presents a non-destructive means of detecting small scale damage of structures with variation in thermal properties of the material. The assumption is supported by numerical calculations, which are in full agreement with experimental investigations made by means of Thermovision techniques. Experiments performed and suitable numerical simulation confirms the essential connection between the state of damage and thermal transmission properties of the investigated materials.