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02811 A trust region interior point algorithm for optimal power flow problems
16 Fuel science and technology (fundamental science, analysis, instrumentation) experimental data for water show smaller values than the theoretical ones. The authors consider the differences are due tO the existence of non-condensable gases in the experimental system. A non-equilibrium MD study is also included in this paper for a discussion on the inverted temperature profiles.
05/02808 A new approach using artificial neural networks for determination of the thermodynamic properties of fluid couples Sencan, A. et al. Energy Conversion and Management, 2005, 46, (1516), 2405-2418. This paper presents a new approach using artificial neural networks (ANN) to determine the thermodynamic properties of two alternative refrigerant/absorbent couples (LiCI-H20 and LiBr + LiNO3 + LiI + LiC1-H20). These pairs can be used in absorption heat pump systems, and their main advantage is that they do not cause ozone depletion. In order to train the network, limited experimental measurements were used as training and test data. Two feedforward ANNs were trained, one for each pair, using the Levenberg-Marquardt algorithm. The training and validation were performed with good accuracy. The correlation coefficient obtained when unknown data were applied to the networks was 0.9997 and 0.9987 for the two pairs, respectively, which is very satisfactory. The present methodology proved to he much better than linear multiple regression analysis. Using the weights obtained from the trained network, a new formulation is presented for determination of the vapour pressures of the two refrigerant/absorbent couples. The use of this new formulation, which can be employed with any programming language or spreadsheet program for estimation of the vapour pressures of fluid couples, as described in this paper, may make the use of dedicated ANN software unnecessary.
05/02809 A numerical exercise for turbulent natural convection and pollutant diffusion in a two-dimensional partially partitioned cavity Joubert, P. et al. International Journal of Thermal Sciences, 2005, 44, (4), 311-322. We present the results of a numerical exercise aimed at comparing the predictions of different conventional turbulent modelling approaches for natural convection at Rayleigh numbers characteristic of applications such as energy savings, fire safety or thermal comfort. A twodimensional configuration was considered that consists of two adjacent rooms separated by a lintel in which natural convection is induced through heating on their opposite sides and subjected to diffusion of a pollutant from one room to the other. Seven contributions are available. The comparison is carried out, in terms of local or global quantities, for the mean thermal and dynamic fields and for the unsteady diffusion of the pollutant from one room to the other. Characteristic differences between steady RANS and unsteady twodimensional DNS and LES approaches are observed and discussed.
05102810 A simplified model for the assessment of the impact probability of fragments Gubmelli, G. et al. Journal of Hazardous Materials, 2004, 116, (3), 175 187. A model was developed for the assessment of fragment impact probability on a target vessel, following the collapse and fragmentation of a primary vessel due to internal pressure. The model provides the probability of impact of a fragment with defined shape, mass and initial velocity on a target of a known shape and at a given position with respect to the source point. The model is based on the ballistic analysis of the fragment trajectory and on the determination of impact probabilities by the analysis of initial direction of fragment flight. The model was validated using available literature data.
05/02811 A trust region interior point algorithm for optimal power flow problems Wang, M. and Liu, S. International Journal of Electrical Power & Energy Systems, 2005, 27, (4), 293-300. This paper presents a new algorithm that uses the trust region interior point method to solve non-linear optimal power flow (OPF) problems. The OPF problem is solved by a primal-dual interior point method with multiple centrality corrections as a sequence of linearized trust region sub-problems. It is the trust region that controls the linear step size and ensures the validity of the linear model. The convergence of the algorithm is improved through the modification of the trust region sub-problem. Numerical results of standard IEEE systems and two realistic networks ranging in size from 14 to 662 buses are presented. The computational results show that the proposed algorithm is very effective to optimal power flow applications, and favours the successive linear programming method. Comparison with the predictor-corrector primal-dual interior point method is also made to demonstrate the superiority of the multiple centrality corrections technique.
408
Fuel and Energy Abstracts November 2005
05/02812 Analysis of small signal voltage stability in multimachine systems using detailed and reduced formulations Padiyar, K. R. and Bhaskar, K. International Journal of Electrical Power & Energy Systems, 2005, 27, (4), 301-317. A detailed formulation considering generator swing dynamics for small signal stability analysis of power system is presented. A reduced formulation obtained by decoupling voltage instability from angle instability is derived from the detailed formulation. The accuracy of prediction of voltage instability using the reduced formulation is investigated through the case study of a 10 machine 39 bus system. The effects of exciter gain and time constant are also examined and the results are presented. In addition, the effect of static var compensator is also analysed through eigenvalue analysis. The results are also validated by system simulation.
05/02813 Analytical expressions for the response of flatplate collector to various transient conditions Dhariwal, S. R. et al. Energy Conversion and Management, 2005, 46, (11-12), 1809-1836. The paper presents a mathematical solution of the one node transient equation for a flat-plate collector by removing approximations like mean fluid temperature and constant initial temperature used in earlier solutions of the equation. Analytical expressions have been obtained for many cases of practical interest. Test procedures for fiat-plate collectors often involve transient studies. Deconvolution of these results and extraction of the desired parameters of the collector become easier with the analytical expression obtained here as compared to the numerical methods used earlier. The theory also allows us to predict the performance of the collector under various pumping conditions and can be applied to actual field conditions when storage and load are included.
05/02814 Buckling behaviour of imperfect ring-stiffened cone-cylinder intersections under internal pressure Zhao, Y. International Journal of Pressure Vessels and Piping, 2005, 82, (7), 553-564. Cone-cylinder intersections are used commonly in pressure vessels and piping. In the case of a cone large end-to-cylinder intersection under internal pressure, the intersection is subject to a large circumferential compressive force. While both the cone and the cylinder may be locally thickened to strengthen the intersection, it is often desirable and convenient to provide an annular plate ring at the cone-to-cylinder joint to supplement local thickening or as an alternative strengthening measure, leading to a ring-stiffened cone-cylinder intersection. Only limited work has been carried out specifically on ring-stiffened conecylinder intersections under internal pressure. This paper presents the first experimental study on such intersections. In addition to the presentation of test results including geometric imperfections, failure behaviour and the determination of buckling mode and load based on displacement measurements, results from non-linear bifurcation analysis using the perfect shape and non-linear analysis using the measured imperfect shape are presented and compared with the experimental results.
05/02815 CFD simulation of the effect of upstream flow distribution on the light-off performance of a catalytic converter Wu, G. and Tan, S. Energy Conversion and Management, 2005, 46, (1314), 2010-2031. This paper describes the evolutions of the distributions of temperature and concentration in the monolith during the cold-start period and the effects of the flow distributions in the monolith on the performance of a catalytic converter using numerical simulation. The effects of the flow distributions on the light-off, warm-up performance and the temporal variation of the solid temperature were studied through numerical simulation. The following conclusions were obtained from the predicted light-off curves and the steady conversion efficiency: (1) The light-off time increases and the total outlet conversion efficiency reduces as the flow uniformity index decreases, which is in good agreement with experimental results. (2) The conversion efficiency decreases due to the reduction of residence time caused by the increase of the velocity as the radius is reduced. The analyses on the distribution of temperature in the monolith show that the temperatures of the solid in the area near the front face of the suhstrate rise as the radius increases, and the radial gradient of the temperature of the solid becomes greater as the flow uniformity index decreases. An experiment on the flow distribution in a catalytic converter with a honeycomb spherical arc was conducted. Experimental results show that the flow distribution in the monolith can be improved greatly by installing the honeycomb spherical arc in the tapered inlet header with a penalty of a relatively small increase of pressure drop.
05/02808 A new approach using artificial neural networks for determination of the thermodynamic properties of fluid couples Sencan, A. et al. Energy Conversion and Management, 2005, 46, (1516), 2405-2418. This paper presents a new approach using artificial neural networks (ANN) to determine the thermodynamic properties of two alternative refrigerant/absorbent couples (LiCI-H20 and LiBr + LiNO3 + LiI + LiC1-H20). These pairs can be used in absorption heat pump systems, and their main advantage is that they do not cause ozone depletion. In order to train the network, limited experimental measurements were used as training and test data. Two feedforward ANNs were trained, one for each pair, using the Levenberg-Marquardt algorithm. The training and validation were performed with good accuracy. The correlation coefficient obtained when unknown data were applied to the networks was 0.9997 and 0.9987 for the two pairs, respectively, which is very satisfactory. The present methodology proved to he much better than linear multiple regression analysis. Using the weights obtained from the trained network, a new formulation is presented for determination of the vapour pressures of the two refrigerant/absorbent couples. The use of this new formulation, which can be employed with any programming language or spreadsheet program for estimation of the vapour pressures of fluid couples, as described in this paper, may make the use of dedicated ANN software unnecessary.
05/02809 A numerical exercise for turbulent natural convection and pollutant diffusion in a two-dimensional partially partitioned cavity Joubert, P. et al. International Journal of Thermal Sciences, 2005, 44, (4), 311-322. We present the results of a numerical exercise aimed at comparing the predictions of different conventional turbulent modelling approaches for natural convection at Rayleigh numbers characteristic of applications such as energy savings, fire safety or thermal comfort. A twodimensional configuration was considered that consists of two adjacent rooms separated by a lintel in which natural convection is induced through heating on their opposite sides and subjected to diffusion of a pollutant from one room to the other. Seven contributions are available. The comparison is carried out, in terms of local or global quantities, for the mean thermal and dynamic fields and for the unsteady diffusion of the pollutant from one room to the other. Characteristic differences between steady RANS and unsteady twodimensional DNS and LES approaches are observed and discussed.
05102810 A simplified model for the assessment of the impact probability of fragments Gubmelli, G. et al. Journal of Hazardous Materials, 2004, 116, (3), 175 187. A model was developed for the assessment of fragment impact probability on a target vessel, following the collapse and fragmentation of a primary vessel due to internal pressure. The model provides the probability of impact of a fragment with defined shape, mass and initial velocity on a target of a known shape and at a given position with respect to the source point. The model is based on the ballistic analysis of the fragment trajectory and on the determination of impact probabilities by the analysis of initial direction of fragment flight. The model was validated using available literature data.
05/02811 A trust region interior point algorithm for optimal power flow problems Wang, M. and Liu, S. International Journal of Electrical Power & Energy Systems, 2005, 27, (4), 293-300. This paper presents a new algorithm that uses the trust region interior point method to solve non-linear optimal power flow (OPF) problems. The OPF problem is solved by a primal-dual interior point method with multiple centrality corrections as a sequence of linearized trust region sub-problems. It is the trust region that controls the linear step size and ensures the validity of the linear model. The convergence of the algorithm is improved through the modification of the trust region sub-problem. Numerical results of standard IEEE systems and two realistic networks ranging in size from 14 to 662 buses are presented. The computational results show that the proposed algorithm is very effective to optimal power flow applications, and favours the successive linear programming method. Comparison with the predictor-corrector primal-dual interior point method is also made to demonstrate the superiority of the multiple centrality corrections technique.
408
Fuel and Energy Abstracts November 2005
05/02812 Analysis of small signal voltage stability in multimachine systems using detailed and reduced formulations Padiyar, K. R. and Bhaskar, K. International Journal of Electrical Power & Energy Systems, 2005, 27, (4), 301-317. A detailed formulation considering generator swing dynamics for small signal stability analysis of power system is presented. A reduced formulation obtained by decoupling voltage instability from angle instability is derived from the detailed formulation. The accuracy of prediction of voltage instability using the reduced formulation is investigated through the case study of a 10 machine 39 bus system. The effects of exciter gain and time constant are also examined and the results are presented. In addition, the effect of static var compensator is also analysed through eigenvalue analysis. The results are also validated by system simulation.
05/02813 Analytical expressions for the response of flatplate collector to various transient conditions Dhariwal, S. R. et al. Energy Conversion and Management, 2005, 46, (11-12), 1809-1836. The paper presents a mathematical solution of the one node transient equation for a flat-plate collector by removing approximations like mean fluid temperature and constant initial temperature used in earlier solutions of the equation. Analytical expressions have been obtained for many cases of practical interest. Test procedures for fiat-plate collectors often involve transient studies. Deconvolution of these results and extraction of the desired parameters of the collector become easier with the analytical expression obtained here as compared to the numerical methods used earlier. The theory also allows us to predict the performance of the collector under various pumping conditions and can be applied to actual field conditions when storage and load are included.
05/02814 Buckling behaviour of imperfect ring-stiffened cone-cylinder intersections under internal pressure Zhao, Y. International Journal of Pressure Vessels and Piping, 2005, 82, (7), 553-564. Cone-cylinder intersections are used commonly in pressure vessels and piping. In the case of a cone large end-to-cylinder intersection under internal pressure, the intersection is subject to a large circumferential compressive force. While both the cone and the cylinder may be locally thickened to strengthen the intersection, it is often desirable and convenient to provide an annular plate ring at the cone-to-cylinder joint to supplement local thickening or as an alternative strengthening measure, leading to a ring-stiffened cone-cylinder intersection. Only limited work has been carried out specifically on ring-stiffened conecylinder intersections under internal pressure. This paper presents the first experimental study on such intersections. In addition to the presentation of test results including geometric imperfections, failure behaviour and the determination of buckling mode and load based on displacement measurements, results from non-linear bifurcation analysis using the perfect shape and non-linear analysis using the measured imperfect shape are presented and compared with the experimental results.
05/02815 CFD simulation of the effect of upstream flow distribution on the light-off performance of a catalytic converter Wu, G. and Tan, S. Energy Conversion and Management, 2005, 46, (1314), 2010-2031. This paper describes the evolutions of the distributions of temperature and concentration in the monolith during the cold-start period and the effects of the flow distributions in the monolith on the performance of a catalytic converter using numerical simulation. The effects of the flow distributions on the light-off, warm-up performance and the temporal variation of the solid temperature were studied through numerical simulation. The following conclusions were obtained from the predicted light-off curves and the steady conversion efficiency: (1) The light-off time increases and the total outlet conversion efficiency reduces as the flow uniformity index decreases, which is in good agreement with experimental results. (2) The conversion efficiency decreases due to the reduction of residence time caused by the increase of the velocity as the radius is reduced. The analyses on the distribution of temperature in the monolith show that the temperatures of the solid in the area near the front face of the suhstrate rise as the radius increases, and the radial gradient of the temperature of the solid becomes greater as the flow uniformity index decreases. An experiment on the flow distribution in a catalytic converter with a honeycomb spherical arc was conducted. Experimental results show that the flow distribution in the monolith can be improved greatly by installing the honeycomb spherical arc in the tapered inlet header with a penalty of a relatively small increase of pressure drop.