This paper reports the use of artificial neural network (ANN) to predict the thermal performance of a parallel flow (PF) condenser with R134a as working fluid. The ANN predictions were compared with the distributed pa...
详细信息
This paper reports the use of artificial neural network (ANN) to predict the thermal performance of a parallel flow (PF) condenser with R134a as working fluid. The ANN predictions were compared with the distributed parameter model (DPM) calculation data, which had been validated by experiments at steady-state conditions while varying the air inlet temperature and velocity, refrigerant inlet temperature, pressure and mass flow rate. Based on the data deduced from DPM, ANN was built to predict heat exchange capacity, outlet refrigerant temperature and pressure drop for both air side and refrigerant side. The ANN was optimized for 6-9-5 configuration with Lavenberg-Marquardt (L-M) algorithm, which showed good performance with the root mean square error (RMSE) in the range of 0.00149 -0.00605, correlation coefficient (R-2) in the range of 0.99989-0.99999 and mean relative error (MRE) in the range of 0.24143-1.31947%. (C) 2013 Elsevier Ltd. All rights reserved.
This work presents a distributed parameter model of the anaerobic digestion process. The model is based on the Anaerobic digestion model no. 1 (ADM1) and was developed to simulate anaerobic digestion process in high-r...
详细信息
This work presents a distributed parameter model of the anaerobic digestion process. The model is based on the Anaerobic digestion model no. 1 (ADM1) and was developed to simulate anaerobic digestion process in high-rate reactors with significant axial dispersion, such as in upflow anaerobic sludge bed (UASB) reactors. The model, which was named ADM1d, combines ADM1's kinetics of biomass growth and substrate transformation with axial dispersion material balances. ADM1d uses a hyperbolic tangent function to describe biomass distribution within a one compartment model. A comparison of this approach with a two-compartment, sludge bed - liquid above the bed, model showed similar simulation results while the one-compartment model had less equations. A comparison of orthogonal collocation and finite difference algorithms for numerical solution of ADM1d showed better stability of the finite difference algorithm. (C) 2007 Elsevier Ltd. All rights reserved.
This paper presents the application of a Nonlinear model Predictive Controller (NMPC) to a distributed solar collector field. The control technique is basically similar to Dynamic Matrix Control (DMC) but in the propo...
详细信息
This paper presents the application of a Nonlinear model Predictive Controller (NMPC) to a distributed solar collector field. The control technique is basically similar to Dynamic Matrix Control (DMC) but in the proposed approach a nonlinear model of the process is directly used without linearization of the process model involved in the control strategy. Moreover, a modified Practical Nonlinear model Predictive Controller (PNMPC) algorithm adapted to solar plant is developed in this work. To include robustness of stability against uncertainties in the NMPC algorithm, a candidate Lyapunov function is included in the cost function. The main purpose of the controller is to manipulate the oil flow rate to maintain the field outlet temperature in the desired reference value and attenuate the disturbances effects. The simulated process used is a distributed parameter model, while for the prediction a lumped parametermodel with time delay was considered. (C) 2013 Elsevier Ltd. All rights reserved.
Precise fault location (FL) is definitely important for fast fault clearance and restoration of energy transmission. The single-terminal FL is mostly met in applications because of its easy implementation, but the acc...
详细信息
Precise fault location (FL) is definitely important for fast fault clearance and restoration of energy transmission. The single-terminal FL is mostly met in applications because of its easy implementation, but the accuracies of all-type impedance FL algorithms are not good because of the effects of fault resistance and variation of an opposite terminal equivalent system impedance. The recently developed and assembled FL algorithm presented in this study, combining the stability of the impedance FL and precision of the travelling waves FL, is an expected good solution. However, the key point to achieve accurate FL is to naturally couple these two algorithms. As is known, the distributedparameters model is also the research base of these two algorithms. Hence, the impedance FL algorithm in line with distributedparameters is proposed in this study. It is achieved on the discovery that the negative sequence current at relay location maintains precisely the same phase to the voltage at fault point. The proposed algorithm is immune to shunt capacitance because of modelling with distributedparameters, and is not disturbed by ground resistance when calculated at zero-crossing moment of voltage at fault point. Simulations and tests prove its good performance.
This paper aims to simulate transient characteristics of distributed parameter model by one-section lumped-circuit model (lumped-II, lumped-T and lumped-Gamma models). Based on error analysis of equivalent impedance i...
详细信息
ISBN:
(纸本)9781479913039
This paper aims to simulate transient characteristics of distributed parameter model by one-section lumped-circuit model (lumped-II, lumped-T and lumped-Gamma models). Based on error analysis of equivalent impedance in the lowest resonant frequency band of distributed parameter model and lumped circuits, a parameter calculation method of lumped circuits was proposed in this paper. The first simplification principle is to ensure power-frequency equivalent impedances equal. Secondly, be sure the first resonant frequency equal and comprehensive error of equivalent impedance in the lowest frequency band minimum. Contrast with traditional one-section lumped circuits, the applicable frequency band of one-section lumped-II, lumped-T and lumped-Gamma models raised in this paper is extended. Obtained results can be used for the establishment of transient equivalent circuit.
Preliminary experimental studies have shown that piezoelectric structures excited by turbulent flow can produce significant amounts of useful power. The research presented in this paper could benefit applications such...
详细信息
ISBN:
(纸本)9780819494719
Preliminary experimental studies have shown that piezoelectric structures excited by turbulent flow can produce significant amounts of useful power. The research presented in this paper could benefit applications such as powering self-sustained sensor networks in small rivers or air flow environments where turbulent fluid flow is a primary source of ambient energy. A novel prototype called piezoelectric grass was designed to be a robust solution for harvesting energy in turbulent fluid flow environments. In this paper, the authors present an experimentally validated theoretical analysis of the piezoelectric grass harvester modeled as a single unimorph cantilever beam exposed to turbulent cross-flow. Lastly, a brief parameter optimization study will be presented. This study will demonstrate how the unimorph harvester design could be modified to achieve maximum power output in a given turbulent fluid flow condition.
A comprehensive distributed parameter model for simulating the steady-state performance of a practical horizontal-tube falling-film evaporator has been developed and validated. This model is capable of predicting the ...
详细信息
A comprehensive distributed parameter model for simulating the steady-state performance of a practical horizontal-tube falling-film evaporator has been developed and validated. This model is capable of predicting the distributions of thermal parameters in the tube-side and shell-side, which provide important information of heat and mass exchange processes. The fluid flow and heat transfer characteristics in tubes are analyzed in detail. The computational time is reduced significantly in comparison with the Computational Fluid Dynamics. Based on the numerical results, it is found that the steam is not evenly distributed in the horizontal tubes of each tube pass, which is favorable for parallel channels with uneven heat fluxes. The mass and heat flux of steam are mutually matched, indicating that the self-compensation characteristic appears among the tubes. In addition, the overall heat transfer coefficient reaches the maximum value of about 3300 W/m(2) K at the entrance region of each tube pass, and then decreases gradually along the flow direction. As liquid film falls downward from tube to tube, the liquid flow rate of seawater continually decreases from 0.063 kg/ms to 0.04 kg/ms with the corresponding salinity gradually increasing from 36 g/kg to 56 g/kg. (C) 2011 Elsevier Ltd. All rights reserved.
Though distance protection has been successfully used for AC transmission line, there is no practical application of it for HVDC transmission line. For distance protection, it is essential to measure accurately at the...
详细信息
ISBN:
(纸本)9781457705472;9781457705465
Though distance protection has been successfully used for AC transmission line, there is no practical application of it for HVDC transmission line. For distance protection, it is essential to measure accurately at the zone boundary to distinguish internal fault from external correctly, and high measurement accuracy at any part of the full line is unnecessary. Besides, HVDC transmission line is generally connected with smoothing reactor at two ends and it can be regarded as the operating boundary of distance protection. Considering these features, a fast full-line tripping distance protection method for HVDC transmission line is introduced in this paper. Based on distributed parameter model, the voltage and current at the end-point are calculated accurately using those at the relay point. After that, the line between the end-point and fault point is simplified as lumped parameter RL model and the fault distance is obtained with differential equations. In this way, high calculation accuracy at the zone boundary is attained and which contributes greatly to the improvement of protection performance. Simulation results show that this method is capable of protecting the whole line with high rapidity, and can be used as primary protection for HVDC transmission.
In this paper, an exact dynamic model of manipulator handling a flexible payload is derived by Hamiton's principle. On the basis of the distributed parameter model, a position controller is designed by using Lyapu...
详细信息
ISBN:
(纸本)9781467313988
In this paper, an exact dynamic model of manipulator handling a flexible payload is derived by Hamiton's principle. On the basis of the distributed parameter model, a position controller is designed by using Lyapunov function related to the total energy of the system. The controller can achieve the given desired link angles and suppress the vibrations of flexible payload. Using the LaSalle's invariance principle and the characteristic of the differential operator, the asymptotic stability in the neighbor-hood of the desired states of the closed-loop system is proved. The effectiveness of the control strategy proposed is supported by some simulations.
In this paper, modeling and control of manipulator handling a flexible payload is considered under the parameter uncertainty and the unknown disturbance. A new sliding mode controller is proposed for manipulator handl...
详细信息
ISBN:
(纸本)9789881563811
In this paper, modeling and control of manipulator handling a flexible payload is considered under the parameter uncertainty and the unknown disturbance. A new sliding mode controller is proposed for manipulator handling a flexible payload based on a distributed-parameter dynamic model and hence is free from the so-called spillover instability, then extended to an adaptive scheme to cope with the upper bounds of the uncertainties were unknown. The controllers are designed to realize system trajectory tracking performance and suppress the elastic vibration. The sliding surface is designed as coupling the joint angle and angular velocity of link, as well as root strain and shear force of flexible payload. Stability of the system is proved by using Lyapunov theory. Numerical simulations result provided to verify the effectiveness of the approach presented.
暂无评论