Comparison of Infrared Thermography and Heat Flux Method for Dynamic Thermal Transmittance Determination

Gaši, Mergim; Milovanović, Bojan; Gumbarević, Sanjin

doi:10.3390/buildings9050132

Cited by 21 publications

(13 citation statements)

References 21 publications

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“…), which would provide a proper reference for the measurement methods. Moreover, the authors are inclined to attempt to determine the total thermal resistance by the dynamic method in accordance with ISO 9869-1 [ 27 ] and to consider the way in which heat transfer coefficients h r and h c are taken into account in the thermal resistance calculations according to the approaches available in the literature, extensively presented in [ 63 ].…”

Section: Discussionmentioning

confidence: 99%

“…There are many methods of estimating radiative heat transfer coefficients, h r , and convective heat transfer coefficients, h c . A comprehensive analysis of this subject can be found in [ 63 ].…”

Section: Thermal Resistance Assessment For Building Enclosure Partsmentioning

confidence: 99%

“…Furthermore, through thermographic measurements, one can also determine the physical quantities characterizing the investigated building enclosure. Taking this into account, thermal imaging studies have been used to quantify external walls, including the U-value of walls [ 58 , 59 ], heat flux density [ 60 , 61 , 62 , 63 ] and to compare various measurement and calculation methods [ 64 , 65 ]. As part of the present study, quantitative thermographic measurements were carried out in climatic test chambers using passive ITM to determine the total thermal resistance of the investigated building enclosure elements, and therefore their thermal transmittance.…”

Section: Introductionmentioning

confidence: 99%

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Non-Destructive Possibilities of Thermal Performance Evaluation of the External Walls

Nowak

2021

Materials

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Identification of the actual thermal properties of the partitions of building enclosures has a significant meaning in determining the actual energy consumption in buildings and in their thermal comfort parameters. In this context, the total thermal resistance of the exterior walls (and therefore their thermal transmittance) in the building is a major factor which influences its heat losses. There are many methods to determine the total thermal resistance of existing walls, including the quantitative thermography method (also used in this study). This paper presents a comparison of the calculated total thermal resistance values and the measured ones for three kinds of masonry walls without thermal insulation and the same walls insulated with expanded polystyrene boards. The measurements were carried out in quasi-stationary conditions in climate chambers. The following three test methods were used: the temperature-based method (TBM), the heat flow meter method (HFM) and the infrared thermography method (ITM). The measurement results have been found to be in good agreement with the theoretically calculated values: 61% of the measured values were within 10% difference from the mean value of total thermal resistance for a given external wall and 79% of the results were within 20% difference. All of the used measuring methods (TBM, HFM and ITM) have proven to be similarly approximate in obtained total thermal resistances, on average between 6% and 11% difference from the mean values. It has also been noted that, while performing measurements, close attention should be paid to certain aspects, because they can have a major influence on the quality of the result.

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Section: Discussionmentioning

confidence: 99%

Section: Thermal Resistance Assessment For Building Enclosure Partsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Non-Destructive Possibilities of Thermal Performance Evaluation of the External Walls

Nowak

2021

Materials

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“…Experimental data contains 510 data points (heat fluxes and air temperatures) [3]. These data points are a part (HFM results) of research from [4]. The analyzed wall is located in Zagreb (on the Faculty of Civil Engineering, UNIZG) and it is oriented towards the east.…”

Section: Experimental Datamentioning

confidence: 99%

Application of Multilayer Perceptron Method on Heat Flow Meter Results for Reducing the Measurement Time

Gumbarević

Milovanović

Gaši

et al. 2020

7th International Electronic Conference on Sensors and Applications

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To reduce the impact on climate change, many countries have developed strategies for the building sector with a goal to reduce the energy demands and carbon emission of buildings. As most buildings that exist today will very likely exist in foreseeable future, many buildings will need to undergo major renovations. One of the most important parameters in determining the transmission heat losses through the building envelope is the U-value, i.e., thermal transmittance, and it is simply the rate of heat transfer per unit temperature. Since the U-value is one of the most important parameters regarding building energy performance, envelope elements that do not perform well in terms of transmission heat losses must undergo a renovation processes. The in-situ U-value of building elements is usually determined by the Heat Flux Method (HFM). One of the issues of current application of the HFM is the measurement duration. This paper explores the possibilities of reducing the measurement time by predicting the heat flux rate using a multilayer perceptron (MLP), a class of artificial neural network. The MLP uses two input layers that are the interior and exterior air temperatures, and the output layer that is the predicted heat flux rate. The predicted value is trained by comparing the predicted heat flux rates with the measured values, and by rearranging the neural network parameters (weights and biases) in corresponding neurons by minimizing the mean squared error defined for trained values (measured versus predicted heat flux rates). The use of MLP shows promising results for predicting the heat flux rates for the analyzed cases (4 days HFM results) when the training is performed on 2/3 or 1/2 of the overall measurement time. The application of the MLP could be in reducing the in-situ measurement time when determining heat losses through building elements in shorter time periods.

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“…At the time of the audit, measured reflected temperature and the air temperature was 20°C, whereas relative humidity was 50%. An example of similar complexity inspected by the means of general IRT in dynamic environmental conditions can be found in the literature 19 . The TV unit was 4.6 m away from a hot source (heater), which was completely sheltered by a couch, and the same distance away from a cold source (window), which was covered with heavy curtains.…”

Section: Ir Thermal Inspection Of An Led Lcd Tvmentioning

confidence: 99%

Infrared thermography as evaluation method of a faulty status of a LED LCD TV

et al. 2020

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The paper presents the application of infrared thermography in the detection of anomalies (hotspots) that may lead to defects of the backlight unit, which are not yet noticeable in the visible part of the electromagnetic spectrum. It is shown on a practical example of an LED LCD TV how hotspots at the maximum level of brightness led to the failure of one element of the LED backlight segments in 2 years time. Once the faulty element was detected, brightness was reduced in order to preserve the remaining LED elements. Infrared thermographic analysis of the faulty state was repeated and compared with measurements of photometric values. The thermal analysis results, before and after failure, are displayed in line at the area of the LED elements and in 3D on the screen surface. The photometric analysis was done on the full-screen area in each of the RGB channels and then followed with in-detail measurements on 200 points. As most photons emitted from the diode are dispersed to the sides of the display due to the lens mounted on top of each LED and other optical elements, data obtained by photometric means are not as precise in the positioning of faulty LEDs, as ones obtained by thermal inspection.

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Comparison of Infrared Thermography and Heat Flux Method for Dynamic Thermal Transmittance Determination

Cited by 21 publications

References 21 publications

Non-Destructive Possibilities of Thermal Performance Evaluation of the External Walls

Non-Destructive Possibilities of Thermal Performance Evaluation of the External Walls

Application of Multilayer Perceptron Method on Heat Flow Meter Results for Reducing the Measurement Time

Infrared thermography as evaluation method of a faulty status of a LED LCD TV

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