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Fengrui Sun - One of the best experts on this subject based on the ideXlab platform.
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Performance optimization of a linear Phenomenological Law system Stirling engine
Journal of the Energy Institute, 2015Co-Authors: Zemin Ding, Lingen Chen, Fengrui SunAbstract:Abstract The power and efficiency performance analyses and optimization of a Stirling engine with heat resistance, heat leakage, regeneration loss and mechanical losses are carried out in this paper by using the combination of Senft's mechanical efficiency model with finite time thermodynamics analysis method. The analytical formulae for indicated power, shaft power, thermal efficiency and brake thermal efficiency for the Stirling engine are derived by assuming that the heat transfer at finite temperature difference between the heat reservoirs and the working fluid obeys the linear Phenomenological heat transfer Law. The optimal operating regions for shaft power and break thermal efficiency are obtained and the influences of heat leakage, regeneration loss and mechanical friction losses on cycle performance are investigated through numerical calculations. The obtained results are expected to provide theoretical guidelines for the optimal design and operation of practical Stirling engines.
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Engine performance improved by controlling piston motion: Linear Phenomenological Law system Diesel cycle
International Journal of Thermal Sciences, 2012Co-Authors: Shaojun Xia, Lingen Chen, Fengrui SunAbstract:Abstract A Diesel cycle engine with internal and external irreversibilities of finite combustion rate of the fuel, friction and heat leakage is investigated in this paper. The heat transfer between the working fluid and the environment obeys the linear Phenomenological heat transfer Law [ q ∝ Δ ( T − 1 ) ] . Under the conditions of the fixed total cycle time and fuel consumed per cycle, the optimal piston motion trajectories for maximizing the work output per cycle of the cases with unconstrained and constrained piston accelerations are derived on each stroke by applying optimal control theory. The optimal distribution of the total cycle time among the strokes is also obtained. The piston motion along the optimal power stroke with constrained acceleration consists of three segments including the initial motion delay, the middle motion and the final maximum deceleration segments. Numerical example for the case with constrained acceleration is given, and the obtained results are also compared with those obtained with Newtonian heat transfer Law. The results show that optimizing the piston motion can improve both the net work output per cycle and the net efficiency of the standard engine by more than 12%, which is mainly due to increase the average temperature of the working fluid during the initial segment of the power stroke.
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Effect of heat transfer Law on the finite-time exergoeconomic performance of a Carnot refrigerator
Exergy An International Journal, 2001Co-Authors: Lingen Chen, Fengrui SunAbstract:The operation of a Carnot refrigerator is viewed as a production process with exergy as its output. The economic optimization of the endoreversible refrigerator is carried out in this paper. The Coefficient of Performance (COP) of the refrigerator is a secondary consideration of the practical engineering effort of maximizing cooling rate and exergy whose goodness is constrained by economical considerations. Therefore, the profit of the refrigerator is taken as the optimization objective. Using the method of finite-time exergoeconomic analysis, which emphasizes the compromise optimization between economics (profit) and the appropriate energy utilization factor (Coefficient of Performance, COP) for finite-time (endoreversible) thermodynamic cycles, this paper derives the relation between optimal profit and COP of an endoreversible Carnot refrigerator based on a relatively general heat transfer Law q ∝ �(T n ). The COP at the maximum profit is also obtained. The results obtained involve those for three common heat transfer Laws: Newton's Law (n = 1), the linear Phenomenological Law in irreversible thermodynamics (n =− 1), and the radiative heat transfer Law (n = 4). 2001 Editions scientifiques et medicales Elsevier SAS
T Melin - One of the best experts on this subject based on the ideXlab platform.
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doped semiconductor nanocrystal junctions
Journal of Applied Physics, 2013Co-Authors: łukasz Borowik, Thuat Nguyentran, Roca P I Cabarrocas, T MelinAbstract:Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (ND≈1020−1021cm−3) silicon nanocrystals (NCs) in the 2–50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple Phenomenological Law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as ND−1/3, and depleted charge linearly increasing with the NC diameter and varying as ND1/3. We thus establish a “nanocrystal counterpart” of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.
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Doped semiconductor nanocrystal junctions studied by Kelvin probe and non-contact atomic force microscopy
2013Co-Authors: Lukasz Borowik, Thuat Nguyen-tran, Dominique Deresmes, Heinrich Diesinger, Pere Roca I Cabarrocas, T MelinAbstract:Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (ND~10^20-10^21 cm-3) hydrogen-passivated silicon nanocrystals (NCs) in the 2-50nm size range, using non-contact atomic force microscopy coupled to Kelvin probe force microscopy experiments with single charge sensitivity, in ultra-high vacuum. We first describe the energy equilibrium associated with the charge transfer, as measured from Kelvin probe microscopy measurement. It reveals the NC quantum confinement (blue-shift of the silicon NC conduction band edges as a function of the nanocrystal size, typically up to the eV range), in good quantitative agreement with tight-binding calculations for hydrogen-passivated silicon nanocrystals. We also show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple Phenomenological Law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. These feature lead to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as ND-1/3, and depleted charge linearly increasing with the NC diameter and varying as ND1/3. This analytical model establishes a "nanocrystal counterpart" of conventional semiconductor planar junctions, valid in regimes of strong electrostatic and quantum confinements.
I. V. Shchetinin - One of the best experts on this subject based on the ideXlab platform.
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Phenomenological description of strain relief in step-graded metamorphic buffer layers based on In x Al1 − x As ternary solutions
Bulletin of the Russian Academy of Sciences: Physics, 2017Co-Authors: A. N. Aleshin, A. S. Bugaev, O. A. Ruban, Nikolay Andreev, I. V. ShchetininAbstract:Spatial distributions of the residual elastic strains in layers of step-graded metamorphic buffers of two different designs, grown via molecular beam epitaxy on the basis of In x Al1 − x As ternary solutions, are obtained by means of reciprocal space mapping. It is shown that with allowance for work hardening, which affects strain relief in buffer layers and increases the strain in dislocation-free layers, the mechanism of strain relief in the final buffer steps, and the residual elastic strain in a buffer dislocation-free layer, are governed by the same Phenomenological Law as in a single-layer heterostructure.
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Phenomenological description of strain relief in step-graded metamorphic buffer layers based on In_ x Al_1 − x As ternary solutions
Bulletin of the Russian Academy of Sciences: Physics, 2017Co-Authors: A. N. Aleshin, A. S. Bugaev, O. A. Ruban, N. V. Andreev, I. V. ShchetininAbstract:Spatial distributions of the residual elastic strains in layers of step-graded metamorphic buffers of two different designs, grown via molecular beam epitaxy on the basis of In_ x Al_1 − x As ternary solutions, are obtained by means of reciprocal space mapping. It is shown that with allowance for work hardening, which affects strain relief in buffer layers and increases the strain in dislocation-free layers, the mechanism of strain relief in the final buffer steps, and the residual elastic strain in a buffer dislocation-free layer, are governed by the same Phenomenological Law as in a single-layer heterostructure.
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Comparative analysis of strain fields in layers of step-graded metamorphic buffers of various designs
Physics of the Solid State, 2017Co-Authors: A. N. Aleshin, A. S. Bugaev, O. A. Ruban, N. Yu. Tabachkova, I. V. ShchetininAbstract:Spatial distribution of residual elastic strain in the layers of two step-graded metamophic buffers of various designs, grown by molecular beam epitaxy from ternary In_xAl_1–xAs solutions on GaAs(001) substrates, is obtained using reciprocal space mapping by three-axis X-ray diffractometry and the linear theory of elasticity. The difference in the design of the buffers enabled the formation of a dislocation-free layer with different thickness in each of the heterostructures, which was the main basis of this study. It is shown that, in spite of the different design of graded metamorphic buffers, the nature of strain fields in them is the same, and the residual elastic strains in the final elements of both buffers adjusted for the effect of work hardening subject to the same Phenomenological Law, which describes the strain relief process in single-layer heterostructures.
Lingen Chen - One of the best experts on this subject based on the ideXlab platform.
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Local stability of a generalized irreversible heat engine with linear Phenomenological heat transfer Law working in an ecological regime
Thermal Science and Engineering Progress, 2018Co-Authors: Lingen Chen, Xiaowei LiuAbstract:Abstract This paper takes a Carnot heat engine which is generalized irreversible as research object and studies its local stability as it operating in ecological regime. The heat transfer in the heat engine abides linear Phenomenological Law. The influences of several factors on local stability are analyzed. Behavior of solutions are presented qualitatively by plotting their phase portraits.
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Performance optimization of a linear Phenomenological Law system Stirling engine
Journal of the Energy Institute, 2015Co-Authors: Zemin Ding, Lingen Chen, Fengrui SunAbstract:Abstract The power and efficiency performance analyses and optimization of a Stirling engine with heat resistance, heat leakage, regeneration loss and mechanical losses are carried out in this paper by using the combination of Senft's mechanical efficiency model with finite time thermodynamics analysis method. The analytical formulae for indicated power, shaft power, thermal efficiency and brake thermal efficiency for the Stirling engine are derived by assuming that the heat transfer at finite temperature difference between the heat reservoirs and the working fluid obeys the linear Phenomenological heat transfer Law. The optimal operating regions for shaft power and break thermal efficiency are obtained and the influences of heat leakage, regeneration loss and mechanical friction losses on cycle performance are investigated through numerical calculations. The obtained results are expected to provide theoretical guidelines for the optimal design and operation of practical Stirling engines.
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Engine performance improved by controlling piston motion: Linear Phenomenological Law system Diesel cycle
International Journal of Thermal Sciences, 2012Co-Authors: Shaojun Xia, Lingen Chen, Fengrui SunAbstract:Abstract A Diesel cycle engine with internal and external irreversibilities of finite combustion rate of the fuel, friction and heat leakage is investigated in this paper. The heat transfer between the working fluid and the environment obeys the linear Phenomenological heat transfer Law [ q ∝ Δ ( T − 1 ) ] . Under the conditions of the fixed total cycle time and fuel consumed per cycle, the optimal piston motion trajectories for maximizing the work output per cycle of the cases with unconstrained and constrained piston accelerations are derived on each stroke by applying optimal control theory. The optimal distribution of the total cycle time among the strokes is also obtained. The piston motion along the optimal power stroke with constrained acceleration consists of three segments including the initial motion delay, the middle motion and the final maximum deceleration segments. Numerical example for the case with constrained acceleration is given, and the obtained results are also compared with those obtained with Newtonian heat transfer Law. The results show that optimizing the piston motion can improve both the net work output per cycle and the net efficiency of the standard engine by more than 12%, which is mainly due to increase the average temperature of the working fluid during the initial segment of the power stroke.
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Effect of heat transfer Law on the finite-time exergoeconomic performance of a Carnot refrigerator
Exergy An International Journal, 2001Co-Authors: Lingen Chen, Fengrui SunAbstract:The operation of a Carnot refrigerator is viewed as a production process with exergy as its output. The economic optimization of the endoreversible refrigerator is carried out in this paper. The Coefficient of Performance (COP) of the refrigerator is a secondary consideration of the practical engineering effort of maximizing cooling rate and exergy whose goodness is constrained by economical considerations. Therefore, the profit of the refrigerator is taken as the optimization objective. Using the method of finite-time exergoeconomic analysis, which emphasizes the compromise optimization between economics (profit) and the appropriate energy utilization factor (Coefficient of Performance, COP) for finite-time (endoreversible) thermodynamic cycles, this paper derives the relation between optimal profit and COP of an endoreversible Carnot refrigerator based on a relatively general heat transfer Law q ∝ �(T n ). The COP at the maximum profit is also obtained. The results obtained involve those for three common heat transfer Laws: Newton's Law (n = 1), the linear Phenomenological Law in irreversible thermodynamics (n =− 1), and the radiative heat transfer Law (n = 4). 2001 Editions scientifiques et medicales Elsevier SAS
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Optimal coefficient of performance and heating load relationship of a three-heat-reservoir endoreversible heat pump
Energy Conversion and Management, 1997Co-Authors: Lingen Chen, Chih WuAbstract:The relationship between optimal COP (coefficient of performance) and heating load of a three-heat-reservoir endoreversible heat pump (including both temperature amplifier and heat amplifier cycles) with non-linear heat transfer (Phenomenological Law in irreversible thermodynamics) is derived. The results presented in this paper are different from those obtained with a linear heat transfer Law. The relationships provide a theoretical basis for developing and utilizing a variety of three-heat-reservoir heat pumps.
A. N. Aleshin - One of the best experts on this subject based on the ideXlab platform.
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Phenomenological description of strain relief in step-graded metamorphic buffer layers based on In x Al1 − x As ternary solutions
Bulletin of the Russian Academy of Sciences: Physics, 2017Co-Authors: A. N. Aleshin, A. S. Bugaev, O. A. Ruban, Nikolay Andreev, I. V. ShchetininAbstract:Spatial distributions of the residual elastic strains in layers of step-graded metamorphic buffers of two different designs, grown via molecular beam epitaxy on the basis of In x Al1 − x As ternary solutions, are obtained by means of reciprocal space mapping. It is shown that with allowance for work hardening, which affects strain relief in buffer layers and increases the strain in dislocation-free layers, the mechanism of strain relief in the final buffer steps, and the residual elastic strain in a buffer dislocation-free layer, are governed by the same Phenomenological Law as in a single-layer heterostructure.
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Phenomenological description of strain relief in step-graded metamorphic buffer layers based on In_ x Al_1 − x As ternary solutions
Bulletin of the Russian Academy of Sciences: Physics, 2017Co-Authors: A. N. Aleshin, A. S. Bugaev, O. A. Ruban, N. V. Andreev, I. V. ShchetininAbstract:Spatial distributions of the residual elastic strains in layers of step-graded metamorphic buffers of two different designs, grown via molecular beam epitaxy on the basis of In_ x Al_1 − x As ternary solutions, are obtained by means of reciprocal space mapping. It is shown that with allowance for work hardening, which affects strain relief in buffer layers and increases the strain in dislocation-free layers, the mechanism of strain relief in the final buffer steps, and the residual elastic strain in a buffer dislocation-free layer, are governed by the same Phenomenological Law as in a single-layer heterostructure.
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Comparative analysis of strain fields in layers of step-graded metamorphic buffers of various designs
Physics of the Solid State, 2017Co-Authors: A. N. Aleshin, A. S. Bugaev, O. A. Ruban, N. Yu. Tabachkova, I. V. ShchetininAbstract:Spatial distribution of residual elastic strain in the layers of two step-graded metamophic buffers of various designs, grown by molecular beam epitaxy from ternary In_xAl_1–xAs solutions on GaAs(001) substrates, is obtained using reciprocal space mapping by three-axis X-ray diffractometry and the linear theory of elasticity. The difference in the design of the buffers enabled the formation of a dislocation-free layer with different thickness in each of the heterostructures, which was the main basis of this study. It is shown that, in spite of the different design of graded metamorphic buffers, the nature of strain fields in them is the same, and the residual elastic strains in the final elements of both buffers adjusted for the effect of work hardening subject to the same Phenomenological Law, which describes the strain relief process in single-layer heterostructures.