The Clark method is one of the most applicable techniques for development of instantaneous unit hydrograph whose efficacy depends upon the accuracy in estimating storage coefficient. The present study was conducted in Kasilian watershed in Mazandaran Province to determine the efficiency of developed hydrograph using Clark's method and to compare the Muskingum storage coefficients obtained through graphical, Clark, Linsley, Mitchell, Johnstone-Cross and Eaton methods. To this aim, the time-area histogram of the study watershed was initially developed. The 3h-unit hydrograph was then derived using the data collected in Sangedeh climatological and Valikbon hydrometric stations. The efficiency of Clark’s instantaneous unit hydrograph developed based on 6 methods for calculation of Muskingum storage coefficient was ultimately compared with the observed average 3h-unit hydrograph of the study area. The results of the study revealed that the Clark’s instantaneous unit hydrograph obtained from graphical method for estimation of storage coefficient with estimation error of less than 33.33% and efficiency coefficient of 83% could suitably simulate different components of the observed average unit hydrograph for the study watershed.

Simulation of process units in order to optimize them has long been considered in the chemical industry. Limited sources of energy supply and their increasing consumption in various industries have made optimization and subsequent energy integration important. There are many alternatives to designing a new process or optimizing an existing one, all of which can waste a lot of time and energy and increase costs. But with simulation software, the speed of estimating alternatives has increased. On the other hand, the optimization features in this type of software have caused the comparison of different processes to be done in the best possible way. Because the comparison of different alternatives should be compared and selected in optimal conditions. Aspen Plus software has process optimization features that the user can easily optimize the simulated unit by defining the objective function and existing constraints as well as free optimization variables. The user must first extract the variables contained in the objective and constraint function from flow Sheet 1 and define the objective function and constraints by combining these variables. Also, free optimization variables should be introduced from the available variables selected for optimization. In this project, optimization is done in order to produce 6 MW power.

The condensate stabilization unit is one of the most important operational units in gas processes. In this unit, the raw condensate is stabilized through a distillation system. This research has investigated the energy, exergy and economic costs by simulating and analyzing the process. In this study, the effect of parameters such as feed flow rate and temperature on energy and exergy performance has been evaluated. The process simulation has been performed using Span Hysys software and the Peng-Robinson equation of state. In order to optimize, the feed preheating method has been used instead of air cooling in the lower part of the column, which has reduced the exergy destruction by 57.91 kW. Also, a heat exchanger has transferred heat by 333.2 kW between the hot and cold streams. The results show that the total process energy consumption has decreased from 1502.98 kW to 1003.94 kW and the exergy efficiency of the stabilization column has increased from 66.11% to 88.21%. In the optimized structure, the total irreversibility of the system has decreased from 257.4 kW to 165.83 kW. This reduction is equivalent to 103.4 kW of exergy destruction of the stabilization tower, which has led to energy storage and improved quality of its consumption.

Groundwater modeling is widely used as a management tool to understand the behavior of aquifer systems under different hydrological stresses. Eyvanekey alluvial aquifer, which is 126 square kilometers flow budget boundaries, is one of the main aquifer in Semnan province. Indiscriminate exploitation of groundwater in recent years led to a water table shortage in this aquifer. In this study to acquire the aquifer hydraulic parameters, prediction the water table and the flow budget of the aquifer, the modeling approach was used by GMS interface. Model calibrated for steady state in a period of one month (Sep. 2008), and for a period of 12 months (2008-2009 water year) for the transient state, using a hydraulic load for the existing wells in plain view, and calibrating in this way, S, and K values were optimized. The verification process, confirms the validity of the results for unsteady conditions. After the model calibration and verification, water table of the pizometers to September 2013 was predicted. The results show that the current trend of declining aquifer will be continued and at the end of the forecast (Sep. 2013), the water level of the hydrograph represents nearly 898.5 m and in proportion to September 2008 will be decrease 8.3 m. The flow budget result shows that most with drawal is done by extraction wells in spring and summer. The aquifer reservoir deficit is about five million cubic meters during simulation period (87-88).

In this paper, design and simulation of fuel control unit (FCU) for a widespread turbojet engine is presented. For this purpose, a brief review on importance of control strategy and engine control modes is firstly presented. Next, the steady state and transient modeling flowchart for the engine is explained and a dynamic model for prediction of engine behavior is developed based on the described flowchart. Then, In order to confirm the ability and effectiveness of the used approaches, the engine simulation results are compared with the experimental results and the good agreement between them illustrates the effectiveness of the steady state and transient modeling. After that, the designed strategy for the engine fuel control unit is described in details and the mathematical equations of FCU parts are presented. Moreover, the mathematical modeling is used for development of a simulation model in SimHydraulic software and the FCU behavior is studied using the developed model. Finally, integration between engine and FCU simulation is done and the simulation results are presented in order to confirm the design and simulation process. The proposed design in this paper can be used for other similar case studies as a regular approach.

Integrating MED-TVC unit with gas turbine cycle (GTC) and organic Rankine cycle (ORC) can be an effective way to take advantage of the hot exhaust gas of gas turbines. In this study, a multi-product system consisting of GTC, MED-TVC, and ORC is investigated. The energy and exergy analysis is carried out and influences some design variables such as inlet air temperature of air compressor, air compressor pressure ratio, high pressure in ORC, pinch point temperature difference, the pressure of motive steam, and TVC compression ratio on the developed system are examined. Calculation shows that the developed unit can produce 39.6 MW of power and 137.3 kg/s of fresh water with a gain output ratio of 4.41 and energy efficiency of 21.5%. According to the result, precooling the air at the entrance of the air compressor and decreasing the pinch point temperature can lead to enhancement exergy and energy efficiency of GTC and the gain output ratio of MED unit, respectively. In addition, the highest exergy destruction takes place in the combustion chamber and desalination unit.

Nowadays, membrane processes are widely used for high purity Nitrogen production. Separation of air by membranes is a flexible process in which the investment and operational costs are lower than for example adsorption or cryogenic processes. Such processes are based on relative permeability of air components which are transported by the pressure difference between two sides of the membrane. Mathematical equations for modeling and simulation of membrane air separation were solved by both HYSYS simulator without any need of external programming out of the simulator environment, and linking Excel to ASPEN PLUS without any need for compile or multiple processes. Countercurrent flow conditions through the membrane, and hollow fiber type membrane were assumed to be applicable. By doing such simulation, the separation percentage of air components in two product streams, and also purity percentage of each stream could be determined. Results of simulations by these two industrial simulators were compared with experimental data and a good consistency was reached. The proposed method can be used for simulation of non-ideal systems successfully.