A novel method using infrared thermography for hot fluid leakage detection on surfaces with uneven emissivities

2021 ◽  
Vol 63 (5) ◽  
pp. 273-279
Author(s):  
Xiao Zhao ◽  
Qi Zhang ◽  
Xiang Xu ◽  
Zhibin Shen ◽  
Bo Zhang
Keyword(s):  
Infrared Thermography ◽  
Negative Temperature ◽  
Temperature Gradients ◽  
Heating Process ◽  
Positive Temperature ◽  
Leakage Detection ◽  
Surface Emissivity ◽  
Uneven Surface ◽  
Transient Heating ◽  
Fluid Leakage

Uneven surface emissivity will cause illusory temperature variation in infrared surface temperature mapping. For this reason, most of the detailed reviews on the use of infrared thermography (IRT) for leakage detection have mainly focused on surfaces with homogeneous emissivity or the recognition of negative temperature gradients, while reports on sensing hot fluid leakage for uneven surface emissivity are very rare. In this study, a hypothesis is put forward and a new leakage detection method is proposed that uses a transient heating-cooling-heating process in association with a subtraction method of infrared images to eliminate the disturbance of inhomogeneous valve surface emissivities. A theoretical analysis is established that is experimentally tested as a case study. The results shows that the hypothesis is clear and the effect of the uneven emissivity is suppressed for the recognition of positive temperature gradients (hot fluid leakage) on a metal valve sample. The current work provides new insights on the modification of the surface emissivity under certain conditions, which has been a major limitation of passive IRT in the past.

Analysis of Concrete Pavement Responses to Temperature and Wheel Loads Measured from Intrumented Slabs

1998 ◽  
Vol 1639 (1) ◽  
pp. 94-101 ◽  
Author(s):  
H. Thomas Yu ◽  
Lev Khazanovich ◽  
Michael I. Darter ◽  
Ahmad Ardani
Keyword(s):  
Structural Response ◽  
Plain Concrete ◽  
Negative Temperature ◽  
Concrete Pavement ◽  
Temperature Gradients ◽  
Critical Conditions ◽  
Test Analysis ◽  
Longitudinal Edge ◽  
Critical Edge ◽  
Using Data

The structural response of jointed plain concrete pavement slabs was evaluated using data obtained from instrumented slabs. The instrumented slabs were a part of newly constructed jointed plain concrete overlay that was constructed on existing asphalt concrete pavement on I–70 in Colorado, near the Kansas–Colorado border. The instrumentation consisted of dial gauges for measuring curling deflections at the slab corner and longitudinal edge and surface-mounted strain gauges for measuring load strains at the longitudinal edge at midslab. The through-thickness temperature profiles in the pavement slabs were also measured at 30-min intervals during the field test. Analysis of the field data showed that the instrumented slabs had a considerable amount of built-in upward curling and that concrete slabs on a stiff base can act completely independent of the base or monolithically with the base, depending on the loading condition. The built-in upward curling of the slabs has the same effect as negative temperature gradients. These findings suggest that the effects of temperature gradients on the critical edge stresses may not be as great as previously thought and that the corner loading, in some cases, may produce more critical conditions for slab cracking. Another important finding of this study is that a physical bond between pavement layers is not required to obtain a bonded response from concrete pavements.

CFD-based optimization of a transient heating process in a natural gas fired furnace using neural networks and genetic algorithms

2018 ◽  
Vol 138 ◽  
pp. 217-234 ◽  
Author(s):  
Rene Prieler ◽  
Markus Mayrhofer ◽  
Christian Gaber ◽  
Hannes Gerhardter ◽  
Christoph Schluckner ◽  
...  
Keyword(s):  
Neural Networks ◽  
Genetic Algorithms ◽  
Natural Gas ◽  
Heating Process ◽  
Transient Heating

Current-transport mechanism in Au/V-doped PVC+TCNQ/p-Si structures

2015 ◽  
Vol 29 (13) ◽  
pp. 1550076 ◽  
Author(s):  
H. Tecimer ◽  
Ö. Vural ◽  
A. Kaya ◽  
Ş. Altındal
Keyword(s):  
Temperature Coefficient ◽  
Transport Mechanism ◽  
Forward Bias ◽  
Thermionic Emission ◽  
Negative Temperature ◽  
Positive Temperature ◽  
Current Transport ◽  
Insulator Layer ◽  
Zero Bias ◽  
Current Transport Mechanism

The forward and reverse bias current–voltage (I–V) characteristics of Au/V-doped polyvinyl chloride+Tetracyanoquino dimethane/porous silicon (PVC+TCNQ/p-Si) structures have been investigated in the temperature range of 160–340 K. The zero bias or apparent barrier height (BH) (Φ ap = Φ Bo ) and ideality factor (n ap = n) were found strongly temperature dependent and the value of n ap decreases, while the Φ ap increases with the increasing temperature. Also, the Φ ap versus T plot shows almost a straight line which has positive temperature coefficient and it is not in agreement with the negative temperature coefficient of ideal diode or forbidden bandgap of Si (α Si = -4.73×10-4 eV/K ). The high value of n cannot be explained only with respect to interfacial insulator layer and interface traps. In order to explain such behavior of Φ ap and n ap with temperature, Φ ap Versus q/2kT plot was drawn and the mean value of (Φ Bo ) and standard deviation (σs) values found from the slope and intercept of this plot as 1.176 eV and 0.152 V, respectively. Thus, the modified ( ln (Io/T2)-(qσs)2/2(kT)2 versus (q/kT) plot gives the Φ Bo and effective Richardson constant A* as 1.115 eV and 31.94 A ⋅(cm⋅K)-2, respectively. This value of A*( = 31.94 A⋅( cm ⋅K)-2) is very close to the theoretical value of 32 A ⋅(cm⋅K)-2 for p-Si. Therefore, the forward bias I–V–T characteristics confirmed that the current-transport mechanism (CTM) in Au/V-doped PVC+TCNQ/p-Si structures can be successfully explained in terms of the thermionic emission (TE) mechanism with a Gaussian distribution (GD) of BHs at around mean BH.

Thermal Fluid Interaction in a Periodically Heated Capillary

2007 ◽  
Author(s):  
X. Y. Huang ◽  
Z. J. Jiao ◽  
N. T. Nguyen
Keyword(s):  
Ccd Camera ◽  
Temperature Gradients ◽  
Heating Process ◽  
Glass Capillary ◽  
Liquid Plug ◽  
Periodic Temperature ◽  
Fluid Interaction ◽  
Measured Liquid ◽  
Heated Capillary ◽  
Heated Glass

This paper reports an experimental study on reciprocating thermocapillary motion of a liquid plug in an externally heated glass capillary. The results were qualitatively compared with that from an analytical modeling. In the experiments, a liquid plug in a glass capillary was positioned between two heaters which were activated alternatively. The liquid plug was driven by the surface tension difference generated by the temperature gradients. The periodic temperature gradients generated by the two heaters made the liquid plug to move back and fort. This method has a potential in manipulating not only the plug motion but also the flow field inside the plug. The position of the plugs was captured and evaluated using a CCD camera. The plug position and maximum traveling distance were measured under various switching frequencies, and the results were recorded as time series for the dynamic analysis. The temperature variation between the heaters depended on the heating process, also depended on the liquid plug motions. An infra thermal camera was used to observe and record the capillary surface temperature when the liquid plug oscillated. A simple model was established for the liquid plug oscillation in the capillary under the periodical heating. The measured liquid plug motion and the temperature variations were compared with predicted results from the model.

Adiabatic demagnetization at absolute negative temperature: Generation of quantum correlations

2019 ◽  
Vol 17 (03) ◽  
pp. 1950023
Author(s):  
Gregory B. Furman ◽  
Shaul D. Goren ◽  
Victor M. Meerovich ◽  
Vladimir L. Sokolovsky
Keyword(s):  
Magnetic Field ◽  
Negative Temperature ◽  
Quantum Correlations ◽  
Zero Magnetic Field ◽  
Positive Temperature ◽  
Nuclear Spins ◽  
Adiabatic Demagnetization ◽  
Negative Temperatures ◽  
Classical Correlations ◽  
Quantum And Classical Correlations

In this paper, we study behavior of the correlations, both quantum and classical, under adiabatic demagnetization process in systems of nuclear spins with dipole–dipole interactions in an external magnetic field and in the temperature range including positive and negative temperatures. For a two-spin system, analytical expressions for the quantum and classical correlations are obtained. It is revealed that the field dependences of the quantum and classical correlations at positive and negative temperatures are substantially different. This difference most clearly appears in the case of zero magnetic field: at negative temperature, the measures of quantum correlations tend to the maximum values with a temperature increase. At positive temperature, these quantities tend to zero at a decrease of magnetic field. It is also found that, for the nearest-neighboring spins in the same field, the values of concurrence and discord are larger at negative temperatures than at positive ones.

Temperature Dependence of Impact Ionization Coefficients in 4H-SiC

2014 ◽  
Vol 778-780 ◽  
pp. 461-466 ◽  
Author(s):  
Hiroki Niwa ◽  
Jun Suda ◽  
Tsunenobu Kimoto
Keyword(s):  
Temperature Dependence ◽  
Temperature Coefficient ◽  
Breakdown Voltage ◽  
Elevated Temperatures ◽  
Phonon Scattering ◽  
Impact Ionization ◽  
Negative Temperature ◽  
Positive Temperature Coefficient ◽  
Positive Temperature ◽  
Ionization Coefficients

Impact ionization coefficients of 4H-SiC were measured at room temperature and at elevated temperatures up to 200°C. Photomultiplication measurement was done in two complementary photodiodes to measure the multiplication factors of holes (Mp) and electrons (Mn), and ionization coefficients were extracted. Calculated breakdown voltage using the obtained ionization coefficients showed good agreement with the measured values in this study, and also in other reported PiN diodes and MOSFETs. In high-temperature measurement, breakdown voltage exhibited a positive temperature coefficient and multiplication factors showed a negative temperature coefficient. Therefore, extracted ionization coefficient has decreased which can be explained by the increase of phonon scattering. The calculated temperature dependence of breakdown voltage agreed well with the measured values not only for the diodes in this study, but also in PiN diode in other literature.

Influence of CF on PTC Properties of LDPE/Carbon Fiber Composites

2014 ◽  
Vol 1056 ◽  
pp. 20-24 ◽  
Author(s):  
Wen Long Zhang ◽  
Yu Ping Wan ◽  
Ya Jie Dai ◽  
Yan Gao ◽  
Chen Wang ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Temperature Coefficient ◽  
Low Cost ◽  
Negative Temperature ◽  
Treatment Method ◽  
Positive Temperature Coefficient ◽  
Carbon Fiber Composites ◽  
Positive Temperature ◽  
Short Lifespan ◽  
Cost Characteristics

PO/CB (Polyolefin/Carbon Black) PTC (Positive Temperature Coefficient) composite with easy processing, low cost characteristics has been applied widely. But it suffered from a relatively short lifespan because of its NTC (Negative Temperature Coefficient) effect and low PTC intensity. In order to overcome this shortcoming, the CF was calcination-treated to prepare LDPE/CF (Low Density Polyethylene/Carbon Fiber) PTC composite. Influence of length, content and treatment method of CF on PTC properties of composites was investigated. Results showed that 0.5mm length CF in composites had higher PTC intensity than that of 2mm length CF. PTC intensity of the composites was enhanced more effectively by calcination treated CF compared to the untreated CF. The maximum PTC intensity was 8.1 when CF’s content was at 8wt%.

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