Showing papers by "National Institute of Technology, Silchar published in 2006"

Thermoeconomic evaluation and optimization of an aqua-ammonia vapour-absorption refrigeration system

Abstract: In this paper, the thermoeconomic concept is applied to the optimization of an aqua-ammonia vapour-absorption refrigeration (VAR) system—aimed at minimizing its overall product cost. The thermoeconomic concept based simplified cost minimization methodology calculates the economic costs of all the internal flows and products of the system by formulating thermoeconomic cost balances. The system is then thermoeconomically evaluated to identify the effects of design variables on costs and thereby enables to suggest values of design variables that would make the overall system cost-effective. Based on these suggestions, the optimization of the system is carried out through an iterative procedure. The results show a significant improvement in the system performance without any additional investment. Finally, sensitivity analysis is carried out to study the effect of the changes in fuel cost to the system parameters.

Optimal Design of Open Channel Section Incorporating Critical Flow Condition

Abstract: The flow at critical condition of an open channel is unstable. At critical condition, a small change in specific energy will cause abrupt fluctuation in water depth of the channel. This is because the specific energy curve is almost vertical at critical state. Therefore, if the design depth of the channel is near or equal to critical depth of the channel, the shape of the channel must be altered to avoid a large fluctuation in water depth. In the present study, a nonlinear optimization model is presented for designing an optimal channel section incorporating the critical flow condition of the channel. The optimization model derives the optimal channel section at a desirable difference from the critical condition of the channel so that a small change in the specific energy of the channel will not cause an abrupt change in flow depth. The objective of the optimization model is to minimize the total construction costs of the channel. Manning’s equation is used to specify the uniform flow condition in the cha...

3D flow field in a scour hole at a wing-wall abutment

Abstract: Experiment was conducted in a laboratory flume to measure the 3D turbulent flow field by an acoustic Doppler velocimeter in a scour hole at a 45? wing-wall abutment under a clear water regime. The profiles of time-averaged velocity components, turbulence intensity components, turbulent kinetic energy and Reynolds stresses at different azimuthal planes are presented. In the upstream, vector plots of flow field at azimuthal and horizontal planes show the presence of a large primary vortex associated with a downflow within the scour hole. In the downstream, the flow is upward. The bed shear stresses within the scour hole are estimated from the Reynolds stresses and the velocity gradients. The data presented in this study would be useful to the researchers for the future development and validation of theoretical models of flow field in a scour hole at bridge abutments

Meta Heuristic Search Algorithms for Short-Term Hydrothermal Scheduling

Abstract: This paper presents the performances of meta heuristic search algorithms in solving short-term hydro thermal scheduling problems. Meta heuristic search algorithms like GA, CEP, FEP, IFEP and PSO have been developed for hydrothermal scheduling problems. The performances of the algorithms are demonstrated on a test case. It has been observed that all the algorithms are capable of finding very nearly global solutions within a reasonable time but PSO algorithm was found to be the most efficient amongst them in terms of convergence rate, solution time and success rate.

Design of HV transmission line protection and control system using wavelet transform for microcontroller application

Abstract: The increasing complexity of the modern power system makes the transient as an important phenomenon. It required the fast fault detection. The fault has the fundamental components and higher order harmonics and time domain information. Analysis of these higher frequencies and noise are very helpful for the detection of the fault. For the proper planning and the operation of digital computation and simulation is necessary. These computer programs include short-circuit analysis, transients program, stability analysis, and power flow study. The extraction of the frequency component of voltage & current with the help of wavelet is presented. This frequency component directly gives the faulty transmission line resistance & reactance. The Mho relay characteristic is utilized for the analysis purpose. Calculated values of resistance & reactance are plotted in the graph. This paper proposed wavelet theory and its application in the development of transmission line protections. The proposed paper simulates a power system network in the PSCAD-a transient simulation and microcontroller program. The simulation of the protective relays under power disturbance is of particular interest in this work.

Utility of Paratransit Modes in Cities of Assam, India

Abstract: This paper investigates paratransit modes available in cities of the Assam region of India, with the purpose of determining the utility of the modes. Three cities—Barpeta, Dibrugarh, and Guwahati—were examined in detail. Information was collected from both primary and secondary sources. The revealed modal split was obtained from a traffic survey. The stated modal choice was obtained from data collected through a home interview survey. The utility function of a particular paratransit mode was estimated with a logit model. The weighted least squares method and maximum likelihood method were used for estimates of the model. Eleven variables, five quantitative and six qualitative, were considered. After an estimation was made of the utility function for each mode in a city, a multinomial logit model was used to estimate the relative utility of each mode in that city. The logit models were estimated with the statistical tool SHAZAM. The predicted modal utility, stated modal choice, and revealed modal split wer...

Performance Evaluation of Analog Circuits with Deep Submicrometer MOSFETs in the Subthreshold Regime of Operation

Abstract: In addition to its attractiveness for ultra-low power applications, analog circuits based on the subthreshold operation of the devices can have significantly higher gain as compared to their superthreshold counterparts In this paper, we systematically study the analog performances in terms of gm, gm/Id etc of conventional deep submicrometer MOSFETs in the subthreshold region We also predict such performances with the help of an improved drift-diffusion based current model The circuit performances (gain, output current etc) are also studied and a very good agreement between the simulation results and the corresponding model prediction is obtained