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Mathematical Modeling of Heat Effect on Cable Insulation

100%
Eroglu E., Guney I., Gunes I., Sener E.
Acta Physica Polonica A
|
2017
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vol. 131
|
issue 3
539-541
EN
In the electric power industry, the cost of energy, its longevity and safety of transferring are important problems. Security problems, environmental effects, discharging occurrences and the endurance of the transporters are the problems that exist as a consequence of the high voltage necessity for the transmission of big amounts of energy and which need to be solved. ADSS (all dielectric self-supporting) cables are generally installed on high voltage transmission lines. They are mostly used in such situations, as high temperature, strong winds and direct sunshine and, as the effect, the UV radiation, etc. The solid materials are in use more frequently than gas or liquid ones. Decent dielectric materials need to be sturdy to puncturing and highly invulnerable for mechanical issues. Moreover, they have to perform and resist well the chemical reactions and high temperature, so that they would not be easily effected by the environmental factors. In this study, the mathematical modeling of heat effects on ADSS cables is investigated by using dry band arcing (IEEE 1222 Electrical surface degradation) test method. A heat source is introduced into the test setup, to evaluate the performance of poly-ethylene cable jackets on ADSS cables at different temperatures. Test results indicate that the endurance of the ADSS cables decreases with the increasing temperature.
2
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Power Optimization of a Miller Thermal Cycle with respect to Residual Gases and Equivalence Ratio

80%
Ebrahimi R.
Acta Physica Polonica A
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2013
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vol. 124
|
issue 1
6-10
EN
The performance of an air standard Miller cycle is analyzed using finite-time thermodynamics. The relations between the power output and the compression ratio and between the power output and the thermal efficiency are derived by detailed numerical examples. The results show that, throughout the compression ratio range, the power output decreases with increasing residual gases. The results also show that if compression ratio is less than certain value, the power output decreases with increasing equivalence ratio, while if compression ratio exceeds certain value, the power output first increases and then starts to decrease with increasing equivalence ratio. The conclusions of this investigation are of importance when considering the designs of actual Miller engines.
3
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The Effects of Cycle Temperature and Cycle Pressure Ratios on the Performance of an Irreversible Otto Cycle

80%
Ust Y., Sahin B., Safa A.
Acta Physica Polonica A
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2011
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vol. 120
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issue 3
412-416
EN
This paper reports the thermodynamic optimization based on the maximum mean effective pressure, maximum power and maximum thermal efficiency criteria for an irreversible Otto heat engine model which includes internal irreversibility resulting from the adiabatic processes. The mean effective pressure, power output, and thermal efficiency are obtained by introducing the compression ratio, cycle temperature ratio, specific heat ratio and the compression and expansion efficiencies. Optimal performance and design parameters of the Otto cycle are obtained analytically for the maximum power and maximum thermal efficiency conditions and numerically for the maximum mean effective pressure conditions. The results at maximum mean effective pressure conditions are compared with those results obtained by using the maximum power and maximum thermal efficiency criteria. The effects of the cycle temperature ratio and cycle pressure ratio on the general and optimal performances are investigated.
4
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Effect of Expansion-Compression Ratio on Performance of the Miller cycle

80%
Ebrahimi R.
Acta Physica Polonica A
|
2012
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vol. 122
|
issue 4
645-649
EN
The objective of this study is to analyze the effect of expansion-compression ratio on the performance of dual cycle. Using finite-time thermodynamics, the relations between thermal efficiency, power output and compression ratio for an air standard Miller cycle have been derived. In the model, the nonlinear relation between the specific heats of working fluid and its temperature, the frictional loss computed according to the mean velocity of the piston, and heat transfer loss are considered. The results show that the power output first increases with the increasing expansion-compression ratio and then starts to decrease. Comparisons of the power output of the Miller, Otto, and Atkinson cycles show that if compression ratio is less than certain value, the power output for Otto cycle is higher, while if compression ratio exceeds certain value, the power output for the Miller cycle is higher. With further increase in compression ratio, the power output for Atkinson cycle is higher. In high compression ratio, the power output of the Miller cycle is higher. The results obtained in the present study provide guidance to the performance evaluation and improvement for practical internal combustion engines.
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