Emissivity reference paints for high temperature applications

Brandt, Ruediger; Bird, C. C.; Neuer, G.

doi:10.1016/j.measurement.2007.10.007

Cited by 51 publications

(54 citation statements)

References 2 publications

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“…10 for various elevated temperatures and compared to ray tracing simulations for the same conditions. Measured effective emittance was significantly reduced with the use of the cavity, from the reference value of 0.95 (Brandt et al, 2008) to below 0.2, an almost 80% reduction in radiative losses. These results show reasonable agreement with the effective emittance of 0.125 -0.18 predicted by ray tracing simulations for the same cavity geometry and a range of realistic cavity reflectances and absorber alignments.…”

Section: Methodsmentioning

confidence: 86%

Optical cavity for improved performance of solar receivers in solar-thermal systems

et al. 2014

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Abstract:A principal loss mechanism for solar receivers in solar-thermal systems is radiation from the absorbing surface. This loss can be reduced by using the concept of directional selectivity in which radiation is suppressed at angles larger than the incident angle of the sunlight striking the absorber. Directional selectivity can achieve efficiencies similar to high solar concentration, without the drawbacks associated with large heat fluxes. A specularly reflective hemispherical cavity placed over the absorber can reflect emitted radiation back to the absorber, effectively suppressing emission losses. An aperture in the cavity will still allow sunlight to reach the absorber surface when used with point focus concentrating systems. In this paper the reduction in radiative losses through the use of a hemispherical cavity is predicted using ray tracing simulations, and the effects of cavity size and absorber alignment are investigated. Simulated results are validated with proof of concept experiments that show reductions in radiative losses of more than 75% from a near blackbody absorber surface. The demonstrated cavity system is shown to be capable of achieving receiver efficiencies comparable to idealized spectrally selective absorbers across a wide range of operating temperatures. Highlights:-A specularly reflective cavity placed over a solar absorber reduces radiative losses -Cavity performance is sensitive to cavity size and cavity-absorber alignment -Radiative loss reduction validated with proof of concept experiments -Losses from near blackbody absorber reduced by over 75% -Receiver efficiency shown to be comparable to idealized wavelength selective absorber

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Section: Methodsmentioning

confidence: 86%

Optical cavity for improved performance of solar receivers in solar-thermal systems

et al. 2014

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“…The use of thermal paints (TP) to measure, correct, and reduce the influence of surface emissivity values have been described in previous work [30]. These paints can be applied to encompass the entire specimen surface as a permanent coating.…”

Section: Introductionmentioning

confidence: 99%

“…These paints can be applied to encompass the entire specimen surface as a permanent coating. Alternatively, the paint can be applied in a single smaller location or a small spot to determine the emissivity by comparing the measured radiance temperature of this spot with that of the uncoated surface [30]. To avoid complications and inaccuracies with respect to radiation from nearby heat sources, such TPs should yield as high an emissivity value as possible, close to the emissivity of a blackbody, which is rated with a value of 1 [8].…”

Section: Introductionmentioning

confidence: 99%

“…To avoid complications and inaccuracies with respect to radiation from nearby heat sources, such TPs should yield as high an emissivity value as possible, close to the emissivity of a blackbody, which is rated with a value of 1 [8]. Rolls-Royce plc developed a variety of novel thermal indicating paints and high-emissivity thermal paints, for use with gas turbine engine development which display an array of permanent colour changes in proportion with the temperature they are exposed to, and typically encompass a temperature range of 140-1330 • C [30,31]. The emissivity of the HE23 TP was found to be stable over a wide temperature range up to 1300 • C using pyrometers.…”

Section: Introductionmentioning

confidence: 99%

“…This was maintained over a range of incidence angles as a result of its high stability and lower angular dependency on emissivity. Effectively, HE23 TP can deliver a constant, very high emissivity value across an extremely wide temperature range and has the potential to prove invaluable in delivering accurate temperature measurement over an extensive range of both high and low temperatures under non-invasive techniques [30].…”

Section: Introductionmentioning

confidence: 99%

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Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Jones

2018

Applied Sciences

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This paper describes the advantages and enhanced accuracy thermography provides to high temperature mechanical testing. This technique is not only used to monitor, but also to control test specimen temperatures where the infra-red technique enables accurate non-invasive control of rapid thermal cycling for non-metallic materials. Isothermal and dynamic waveforms are employed over a 200-800 • C temperature range to pre-oxidised and coated specimens to assess the capability of the technique. This application shows thermography to be accurate to within ±2 • C of thermocouples, a standardised measurement technique. This work demonstrates the superior visibility of test temperatures previously unobtainable by conventional thermocouples or even more modern pyrometers that thermography can deliver. As a result, the speed and accuracy of thermal profiling, thermal gradient measurements and cold/hot spot identification using the technique has increased significantly to the point where temperature can now be controlled by averaging over a specified area. The increased visibility of specimen temperatures has revealed additional unknown effects such as thermocouple shadowing, preferential crack tip heating within an induction coil, and, fundamental response time of individual measurement techniques which are investigated further.

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Fault detection and diagnosis in photovoltaic panels by radiometric sensors embedded in unmanned aerial vehicles

Ramírez

Das

Márquez

2021

Progress in Photovoltaics

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Photovoltaic solar energy is increasing its capacity in the global electric market due to its lower operating costs and higher efficiency, together with the support of the governments. Photovoltaic solar panels require high initial investments, and it is necessary to use advanced and efficient methods that lead to the maintainability and reliability of these systems, extending their life cycle and productivity. New condition monitoring systems are being applied to reduce the cost of inspections and ensure efficient data collection. The main contribution of this paper is a new efficient and low-cost condition monitoring system based on radiometric sensors. The thermal patterns of the main photovoltaic faults (hot spot, fault cell, open circuit, bypass diode, and polarization) are studied in real photovoltaic panels. Different scenarios are considered, analyzing online the main patterns of the faults by Internet of Things.The accuracies of the results are statistically analyzed and compared with fault-free scenarios. The validation of the approach is done by thermographic analysis of the experiments and employing a different radiometric sensor. The detection of faults with statistical analysis is achieved in 100% of the cases, and the identification of the specific fault in 96% of the scenarios. An artificial neural network and classification learner algorithms are employed to validate the results, obtaining similar results for fault identification, 95% and 94%, respectively, and 100% for fault detection.

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Emissivity reference paints for high temperature applications

Cited by 51 publications

References 2 publications

Optical cavity for improved performance of solar receivers in solar-thermal systems

Optical cavity for improved performance of solar receivers in solar-thermal systems

Enhancing the Accuracy of Advanced High Temperature Mechanical Testing through Thermography

Fault detection and diagnosis in photovoltaic panels by radiometric sensors embedded in unmanned aerial vehicles

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