scholarly journals An Equivalent Heat Transfer Model Instead of Wind Speed Measuring for Dynamic Thermal Rating of Transmission Lines

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4679
Author(s):  
Zhao Liu ◽  
Honglei Deng ◽  
Ruidong Peng ◽  
Xiangyang Peng ◽  
Rui Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Wind Speed ◽  
Transmission Lines ◽  
Measurement Techniques ◽  
Weather Data ◽  
Transfer Model ◽  
The Real ◽  
Low Wind Speed ◽  
Ieee Standard ◽  
The Impact

With the increase in electricity demand, the ampacity calculation based on the dynamic thermal rating (DTR) technology is increasingly significant for assessing and improving the power transfer capacity of the existing overhead conductors. However, the DTR models now available present some inadequacies in measurement techniques related to wind speed. Therefore, it is essential to propose a new model instead of wind speed measuring in DTR technology. In this paper, the influence analysis of various weather parameters on the conductor ampacity is carried out by using the real weather data. Based on the analysis, it is confirmed that the impact of wind speed is significant, especially in the case of the low wind speed. Moreover, an equivalent heat transfer (EHT) model for DTR technology is proposed instead of wind speed measuring. For this EHT model, the calculation of conductor ampacity is realized through investigating the correlation of heat losses between the heating aluminum (Al) ball and conductor. Finally, combined with the finite element method (FEM), the EHT model proposed in this paper is verified by the Institute of Electrical and Electronic Engineers (IEEE) standard. The results indicate that the error of the EHT model is less than 6% when employing the steady thermal behavior of the Al ball to calculate the ampacity. The EHT model is useful in the real-time thermal rating of overhead conductors. It can increase the utilization of overhead conductors while also avoiding the limitation of the existing measurement techniques related to wind speed.

scholarly journals The Protect Air Film of an Exterior Window

2021 ◽  
Author(s):  
Sanaz Dianat
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Speed ◽  
Glass Temperature ◽  
Experimental Procedure ◽  
Wind Speeds ◽  
Computational Fluid Dynamics Cfd ◽  
Air Film ◽  
The Impact

The research paper investigates the impact of a window’s exterior air film on the assembly temperature. The exterior air film constitutes a vital portion of a window’s insulating values. The air film increases the temperature of the window exterior pane to a temperature above ambient temperature. The air film also rises the interior glass temperature and reduces the heat transfer from the interior surface. According to computational fluid dynamics (CFD), the air film is removed in windy conditions, decreasing the window temperature on the outside as well as on the inside. The idea behind the project is to carry out an experimental procedure on three different windows to validate the CFD results, which indicates the effect of various wind speeds. Keyword: Exterior air film, computational fluid dynamics, window assembly, wind speed

scholarly journals The Protect Air Film of an Exterior Window

2021 ◽  
Author(s):  
Sanaz Dianat
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Wind Speed ◽  
Glass Temperature ◽  
Experimental Procedure ◽  
Wind Speeds ◽  
Computational Fluid Dynamics Cfd ◽  
Air Film ◽  
The Impact

The research paper investigates the impact of a window’s exterior air film on the assembly temperature. The exterior air film constitutes a vital portion of a window’s insulating values. The air film increases the temperature of the window exterior pane to a temperature above ambient temperature. The air film also rises the interior glass temperature and reduces the heat transfer from the interior surface. According to computational fluid dynamics (CFD), the air film is removed in windy conditions, decreasing the window temperature on the outside as well as on the inside. The idea behind the project is to carry out an experimental procedure on three different windows to validate the CFD results, which indicates the effect of various wind speeds. Keyword: Exterior air film, computational fluid dynamics, window assembly, wind speed

Overall Effectiveness of a Blade Endwall With Jet Impingement and Film Cooling

2013 ◽  
Vol 136 (3) ◽  
Author(s):  
Amy Mensch ◽  
Karen A. Thole
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Jet Impingement ◽  
Heat Transfer Analysis ◽  
Transfer Model ◽  
Convective Cooling ◽  
Impingement Cooling ◽  
Internal Impingement ◽  
The Impact ◽  
Overall Effectiveness

Ever-increasing thermal loads on gas turbine components require improved cooling schemes to extend component life. Engine designers often rely on multiple thermal protection techniques, including internal cooling and external film cooling. A conjugate heat transfer model for the endwall of a seven-blade cascade was developed to examine the impact of both convective cooling and solid conduction through the endwall. Appropriate parameters were scaled to ensure engine-relevant temperatures were reported. External film cooling and internal jet impingement cooling were tested separately and together for their combined effects. Experiments with only film cooling showed high effectiveness around film-cooling holes due to convective cooling within the holes. Internal impingement cooling provided more uniform effectiveness than film cooling, and impingement effectiveness improved markedly with increasing blowing ratio. Combining internal impingement and external film cooling produced overall effectiveness values as high as 0.4. A simplified, one-dimensional heat transfer analysis was used to develop a prediction of the combined overall effectiveness using results from impingement only and film cooling only cases. The analysis resulted in relatively good predictions, which served to reinforce the consistency of the experimental data.

Evaluating the Impact of Free-Stream Turbulence on Convective Cooling of Overhead Conductors Using Large Eddy Simulations

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Mohamed Abdelhady ◽  
David H. Wood
Keyword(s):  
Wind Speed ◽  
Real Time ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Diameter Ratio ◽  
Weather Data ◽  
Length Scale ◽  
Free Stream Turbulence ◽  
Large Eddy ◽  
The Impact

The international trend of using renewable energy sources for generating electricity is increasing, partly through harvesting energy from wind turbines. Increasing electric power transmission efficiency is achievable through using real-time weather data for power line rating, known as real-time thermal rating (RTTR), instead of using the worst case scenario weather data, known as static rating. RTTR is particularly important for wind turbine connections to the grid, as wind power output and overhead conductor rating both increase with increasing wind speed, which should significantly increase real-time rated conductor from that of statically rated. Part of the real-time weather data is the effect of free-stream turbulence, which is not considered by the commonly used overhead conductor codes, Institute of Electrical and Electronics Engineers (IEEE) 738 and International Council on Large Electric Systems (CIGRÉ) 207. This study aims to assess the effect free-stream turbulence on IEEE 738 and CIGRÉ 207 forced cooling term. The study uses large eddy simulation (LES) in the ANSYS fluent software. The analysis is done for low wind speed, corresponding to Reynolds number of 3000. The primary goal is to calculate Nusselt number for cylindrical conductors with free-stream turbulence. Calculations showed an increase in convective heat transfer from the low turbulence value by ∼30% at turbulence intensity of 21% and length scale to diameter ratio of 0.4; an increase of ∼19% at turbulence intensity of 8% and length scale to diameter ratio of 0.4; and an increase of ∼15% at turbulence intensity of 6% and length scale to diameter ratio of 0.6.

Simulation Analysis of Savonius Turbine with Self-Rotating Blades

2012 ◽  
Vol 614-615 ◽  
pp. 480-484
Author(s):  
Zhi Peng Tang ◽  
Ying Xue Yao ◽  
Liang Zhou ◽  
Jin Ming Wu ◽  
Bo Wen Yu
Keyword(s):  
Wind Speed ◽  
Simulation Analysis ◽  
Power Coefficient ◽  
Rotating Blades ◽  
Low Wind Speed ◽  
Separating Flow ◽  
Wide Range ◽  
Low Efficiency ◽  
Driving Torque ◽  
The Impact

This paper analyzed the advantages of traditional Savonius (S-type) turbine and the reasons of its low efficiency, proposed a new type of turbine with self-rotating blades and surrounded by a rectifier, and studied the aerodynamic performance by numerical simulations. The turbine is composed of a rectifier and a rotor, the rectifier consists by straight and arc segments which can accelerate the wind speed and adjust the inflow wind angle. The self-rotating blade can reduce the impacted area acting on the leeward blade by wind and arm of the impact torque, therefore reduces the resistant torque of the blade, and the driving torque acting on the windward blade is almost the same with traditional S-type turbine, which can increase the overall driving torque. The result shows that the new turbine has the advantages as below: wide range of wind speed for effective working, high power coefficient (Cp), suitable for low wind speed aera etc. Although the flow field in S-type turbine is complex separating flow, the performance of the turbine proposed in this paper is improved and is better than traditional S-type turbine in numerical simulation which is worth for spreading.

Heat Transfer Effects During Cold Dense Gas Dispersion: Wind-Tunnel Simulation of Cold Gas Spills

1986 ◽  
Vol 108 (1) ◽  
pp. 9-15 ◽  
Author(s):  
R. N. Meroney ◽  
D. E. Neff
Keyword(s):  
Heat Transfer ◽  
Wind Speed ◽  
Wind Tunnel ◽  
Transfer Effects ◽  
Concentration Data ◽  
Gas Dispersion ◽  
Humidity Effects ◽  
Low Wind Speed ◽  
Wind Tunnel Simulation ◽  
Heat Transfer Effects

Wind-tunnel concentration data were obtained for continuous area releases of ambient temperature Freon–air mixtures, cold N2, cold CO2, and cold CH4 clouds. Heat transfer and humidity effects on model concentration distributions were significant for methane plumes when surface Richardson numbers Ri* were large (i.e., low wind speed and high boiloff rate conditions). At field scales heat transfer and humidity will still play a role in the dispersion of methane spill cases, but plume dilution and liftoff are not expected to be as exaggerated as for the model cases.

Exergetic efficiency optimization of a thermoacoustic cooler

2007 ◽  
Vol 221 (11) ◽  
pp. 1339-1343 ◽  
Author(s):  
L Chen ◽  
F Wu ◽  
Q Li ◽  
F Guo ◽  
A Su
Keyword(s):  
Heat Transfer ◽  
Imaginary Part ◽  
Optimal Performance ◽  
Transfer Model ◽  
Cooling Load ◽  
Exergetic Efficiency ◽  
The Real ◽  
Complex Exponent ◽  
Thermoacoustic Cooler ◽  
Selection Of

A heat transfer model with a complex exponent between a thermoacoustic cooler and its surrounding heat reservoirs is established in the current paper. Both the real part and the imaginary part of the heat transfer exponent strongly affect the optimal performance of the cooler. The exergetic efficiency and the cooling load decrease with an increase in the imaginary part of the complex exponent when the real part is fixed. The optimal performance zone of the thermoacoustic cooler is obtained by numerical analysis. The results obtained herein may be useful for the selection of operation parameters for a real thermoacoustic cooler.

scholarly journals A one-dimensional modeling study on the effect of advanced insulation coatings on internal combustion engine efficiency

2020 ◽  
pp. 146808742092158
Author(s):  
Alberto Broatch ◽  
Pablo Olmeda ◽  
Xandra Margot ◽  
Josep Gomez-Soriano
Keyword(s):  
Heat Transfer ◽  
Combustion Engine ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Insulation Material ◽  
One Dimensional ◽  
Engine Efficiency ◽  
Dimensional Modeling ◽  
The One ◽  
The Impact

This article presents a study of the impact on engine efficiency of the heat loss reduction due to in-cylinder coating insulation. A numerical methodology based on one-dimensional heat transfer model is developed. Since there is no analytic solution for engines, the one-dimensional model was validated with the results of a simple “equivalent” problem, and then applied to different engine boundary conditions. Later on, the analysis of the effect of different coating properties on the heat transfer using the simplified one-dimensional heat transfer model is performed. After that, the model is coupled with a complete virtual engine that includes both thermodynamic and thermal modeling. Next, the thermal flows across the cylinder parts coated with the insulation material (piston and cylinder head) are predicted and the effect of the coating on engine indicated efficiency is analyzed in detail. The results show the gain limits, in terms of engine efficiency, that may be obtained with advanced coating solutions.

Heat Transfer Correction Methods for Turbocharger Performance Measurements

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Mario Schinnerl ◽  
Joerg Seume ◽  
Jan Ehrhard ◽  
Mathias Bogner
Keyword(s):  
Heat Transfer ◽  
Predictive Accuracy ◽  
Combustion Engine ◽  
Transfer Model ◽  
Performance Measurements ◽  
One Dimensional ◽  
Matching Process ◽  
High Speeds ◽  
Work Done ◽  
The Impact

Turbocharger performance maps used for the matching process with a combustion engine are measured on test benches which do not exhibit the same boundary conditions as the engine. However, these maps are used in engine simulations, ignoring that the compressor and turbine aerodynamic performance is rated on the basis of quantities which were measured at positions which do not coincide with the respective system boundaries of the turbomachinery. In the operating range of low to mid engine speeds, the ratio between the heat flux and the work done by the turbine and the compressor is much greater than at high speeds where heat transfer phenomena on the compressor side can usually be neglected. Heat losses on the turbine side must be taken into account even at higher shaft speeds when dealing with isentropic turbine efficiencies. Based on an extensive experimental investigation, a one-dimensional heat transfer model is developed. The compressor and turbine side are treated individually and divided into sections of inlet, wheel, outlet, diffuser, and volute. The model demonstrates the capability to properly account for the impact of heat transfer, and thereby improves the predictive accuracy of temperatures relevant for the matching process.

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