فهرست مطالب ابراهیم جهانشاهی جواران

In the present study, energy and exergy analysis of a hybrid system including concentrating photovoltaic thermal module, organic Rankine cycle, single-effect water / lithium-bromide adsorption cooling and membrane distillation desalination at transient conditions is performed. The combined energy and exergy analyzes of the system were performed by a computer program written in EES software. The results showed that the annual electrical power generated by concentrating photovoltaic thermal modules and organic Rankine cycle are 81.74 MWh and 13.84 MWh, respectively. In addition, the cooling capacity of the refrigeration cycle is 32.91 MWh and the membrane distillation desalination plant produces fresh water at a rate of 0.3025 kg/s.m2. The degraded exergy of the concentrating photovoltaic system and organic Rankin cycle is 35.36 MWh and 11.43 MWh, respectively. The exergy efficiency of the absorption cooling cycle is 17.57%. Also, in membrane distillation desalination, the total degradation rate is 6.32 MWh. In addition, the obtained results prdedicts thermal efficiency and exergy efficiency of 75% and 72.93% for the combined system, respectively.

In this paper, with the aid of thermodynamic modeling of Organic Rankin Cycle (ORC), the effect of some parameters on the thermal efficiency and input heat of ORC is examined using design of experiment method. By this technique, along with the Backward Elimination Regression model, the values of thermal efficiency and input heat of ORC are introduced as a function of effective parameters. For this purpose, first, by comparing the two methods of surface response and selecting the central composite design procedure, the values of response functions were computed based on the input variables. The numerical values derived from these functions resulting from RSM central composite design are in good agreement with published theoretical results in literatures. The results show that among the effective parameters, turbine inlet temperature values, turbine isentropic efficiency , and mass flow ratio have most significant effect on thermal efficiency and also for input heat to ORC the most effective parameters are flow rate of working fluid, condenser temperature and input temperature of ORC's turbine. In order to numerical optimization according to the operating conditions of real cycles based on the desirability function and the central composite design procedure, it was revealed that the thermal efficiency is close to 36% for the heat input of 130 kW.

In this study, the thermodynamic and thermoeconomic analysis of an Absorption Heat Transformer (AHT), Organic Rankine Cycle (ORC) and Reverse Osmosis (RO) desalination combined system was performed. The performance of the system was examined with the objective of generating electricity and fresh water from low temperature heat sources. All analyses are carried out based on the thermodynamic and thermoeconomic laws by programming in the EES software. The results have shown that the AHT with increase temperature to 105°C, is produced 494.7 kW thermal energy in absorber, having the Coefficient of Performance (COP) of 0.4372. By applying the AHT produced thermal energy; it is possible to produce 63.15 kW of electricity in the ORC. By using this amount of electricity in the reverse osmosis system, 216.2 m3/day of freshwater are produced where the cost of this amount of water produced achieved 2.374 $/m3. Also, in thermoeconomic analysis, the unit cost of the exergy for all points of the system and the unit cost of the electricity and fresh water were calculated. The levelized cost of electricity at different heat rates was determined, according to the results, the levelized cost of electricity is reduced when the heat rate increases. Also the effects of interest and inflation rate changes on the unit cost of the fresh water were studied.

In gas power plants, a lot of energy is lost in the form of heat more than the electricity produced. In the present research, techno-economic evaluation of combined power, desalination and cooling systems running by the exhaust flue gases of a gas turbine in Iran is performed. In addition to using power generated by the gas turbine, attempts were made to use Organic Rankine Cycle to recover the heat dissipated from gas turbine in order to reproduce power. In fact, choosing the appropriate technology for the combined system of simultaneous production of power, fresh water and cooling based on energy and economic analysis is investigated. Results showed that multiple-effect distillation system with fresh water price of 1 $ per m3 should be used in order to produce high tonnage fresh water, and to achieve the proper price of fresh water, Reverse Osmosis by giving priority to ORC power, and then, GT application is suggested. According to the calculated price of power sale, the sale of gas turbine power is approximately 0.1 $ per kW/h. Regarding cooling systems, the results showed that the absorption system has a lower initial cost and produces a greater cooling load than the compression system, and if necessary, the compression cooling system can be used only to achieve very low temperatures.

In this study, techno-economic comparison of monocrystalline and concentrating photovoltaic power plants for the selected cities of Kerman province was carried out. After modeling the implied photovoltaic systems and validating the modeling results of the monocrystslline photovoltaic system with the measured data of an installed 5kW monocrystalline photovoltaic power plant at the Graduate University of Advanced Technology, daily and yearly electrical energies production analysis for both plants was presented. Then, the electrical efficiency and the performance factors, including capacity factor, final yield, reference yield and the performance ratio were determined. The economic analysis results showed that the northern cities of Kerman province had more favorable economic indicators, so internal rate of return, balanced cost of electricity, net present value, and benefit-cost ratio for the monocrystal photovoltaic plant were 21-22.1%, 13.3-13.9 dollars per kilowatt, 2-4.2 thousand dollars, and 1.04-1.09, respectively and for the concentrating photovoltaic plant were 24.9-28.6%, 8.8-10.2 dollars per kilowatt, 17.1-30.5 thousand dollars, and 1.24-1.43, respectively. Finally, a comprehensive comparison was made between the conventional PV systems and the CPV system for two scenarios: the same capital investment cost and the same nominal installed power. Results showed that at both scenarios, the concentrating photovoltaic is superior to the monocrystalline PV plant, in a way that Kerman and Jiroft cities, as the best cities, had the net present value of 30.5 thousand dollars and 21 thousand dollars, respectively.

In the present study, the combination of concentration lattice Boltzmann method with a smoothed profile method was used to simulate the dissolution of solid circular particles between parallel plates that are moving in opposite directions. The hydrodynamic simulation was performed based on the single relaxation time lattice Boltzmann method and the convection-diffusion equation was used to determine the concentration of the solute in the liquid phase. Additionally, the smoothed profile method was used to calculate the no-slip boundary condition at the liquid-solid interface and concentration forces. To evaluate the accuracy of the proposed model, the simulation results were compared with the empirical data in the literature. The difference between the simulation results and the empirical data for the Sherwood number at different Peclet numbers was less than 2%. The results show that the smallest dissolution time in systems with different volume fractions is in a system with the least volume fraction. As the volume fraction increases, the solid-liquid mass transfer driving force is decreased in the system. The simulation results showed that by increasing the Reynolds number from 0.05 to 0.38, the time required to reach the normalized volume fraction to 0.05 of its initial value reduced from 0.36 s to 0.17 s. Also, by increasing the Peclet number from 5.5 to 115, the Sherwood number increased from 1.74 to 4.06. In addition, the increase in the Schmidt number in the system leads to a slower dissolution time. Finally, the polydispersity in the system was studied.

The application of solar energy for space cooling has been increasingly considered in Iran and other countries in the last two decades. In this study, two different configurations of a solar assisted refrigeration system have been studied. The first system is the combination of a lithium bromide vapor absorption refrigeration system and flat plate collectors. The other system is consisted of a compression refrigeration system and thermal photovoltaic panels. For this purpose, 32% of the roof area of the building has been covered with 105 flat plate collectors, each with a total area of 1.591 m2, or 288 photovoltaic panels each with an area of 0.556 m2. Both systems have been compared in terms of energy, exergy, and economic viewpoints. This comparison has been conducted for providing the 70 kW cooling capacity system required for an office building with an area of 500 m2. The results of this study showed that at an evaporator temperature of 5°C and the ambient temperature of 27°C, the coefficient of performance of the compression chiller is 3.5 and the absorption chiller is 0.71. Also, the total energy efficiency and the total exergy efficiency in the compression chiller system combined with thermal photovoltaic panels are 7.43% and 8.25% respectively. Those two parameters for the absorption chiller combined with flat plate collectors are 9.16% and 6.66%, respectively. In the economic analysis, the annual life cycle cost for the compression chiller system combined with thermal photovoltaic collectors is 9710 $ and this cost for the absorption chiller system combined with flat plate collectors is estimated 7649 $.

Scheffler fixed focus concentrator is used for domestic and industrial applications in various parts of the world. This concentrator has an elliptical frame and designed in such a way that can provide fixed focus during a year with proper rotation. In this research, design and manufacturing principles of a Scheffler standing concentrator with an area of 2.7 m2 is presented. To this end, concentrator and its receivers were designed using Solidworks software.. Thermal efficiency of a manufactured concentrator was obtained from its operation for many days with different conditions. The results show that a concentrator with an area of 2.7 m2 can provide incident radiation up to 9.82 times that on the horizontal surface at the focal point. In addition, results of the experiment show that this concentrator can provide enough heat for boiling of 12 liters of water in less than 2 hours. A thermal efficiency of 37% was obtained for a receiver with surface of black color and glass cover. Finally, the standing concentrator was used to heat 100 lit of water resulting in an increase of water temperature to 60 °C.

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) has been widely used in recent decades due to operating at low temperature with high energy density. Water management is one of the main challenges for the development and commercialization of PEMFCs, which has a significant impact on their performance. The behavior of liquid water in the PEMFCs is very important. In this study a pore scale model is used to investigate liquid water transport in the gas diffusion layer (GDL) of PEMFCs. The GDL layer generated by randomly placing circular solid particles. The pseudo-potential lattice Boltzmann (LB) proposed by shan and chen is used to simulate two phase flow. The code was validated in three modes and is verified correctly then, the effect of three pore size particles, porosity coefficient and hydrophobicity of the GDL on the water transfer has been investigated. The results show that, over time, the amount of saturation in the GDL increases and ultimately reaches a constant value. In addition to by reducing the diameter of the particles, the amount of saturation and the number of breakthrough sites decreased, which increases the oxygen penetration.Also, the amount of local water saturation in the catalyst layer (CL) interface and the GDL tends toward one, indicating that oxygen molecules in these regions should be dissolved in water and then fed to the CL. In addition to, the amount of liquid water inside the porous layer decreases with increasing hydrophobicity

In this research work, using the recently introduced entropic constant speed kinetic model and employing the Pseudo-Potential model of Shan and Chen (SC), two phase flow of incompressible and immiscible fluids through porous media is studied. Applications of the entropic kinetic models in simulating multi-phase and multi-component flows have been thoroughly investigated, during the past decade. Lack of an entropy function, in a kinetics based model, implies that the existence of a unique equilibrium state, under all flow conditions and for all positions and times, cannot be guaranteed by the model. Hence, simulation of two multi-phase flows with high density ratios, using the conventional kinetic models (which do not satisfy the second law of thermodynamics) may not yield proper results, due to numerical instabilities. In this research, performing numerical simulations, the accuracy and stability of the recently introduced constant speed kinetic model and the conventional lattice Boltzmann models have been compared with each other. The present simulations include the verification of the Laplace Law and the contact angles and two phase flow through simple channels. In addition to the above, two phase flow in porous media has been simulated and the relative permeability vs wettability has been reported. The obtained results are in excellent agreement with previous results reported by others researchers.

In the present study, a MATLAB computer code has been prepared for the simulation of a multi-effect desalination unit with thermal vapor compression. The first step is to obtain the parameters’ effect on the performance, including motive steam flow rate, temperatures, and dimensions of the system. Comparison of the present simulation results with the data reported for an actual desalination system shows a good consistency. System performance in two different cases of extracted secondary vapor from the last effect and all effects is investigated. It is observed that a higher performance ratio and specific heat transfer area are obtained by receiving secondary vapor from the last effect. Finally, the genetic algorithm is used to maximize the performance ratio of the system which is considered as the fitness function. Optimization results show that one can achieve a performance ratio higher than 17 and specific heat consumption less than 107 kJ/kg for a system with 10 effects.

In the present study, combustion phenomenon and heat transfer in a 3-D rectangular porous radiant burner (PRB) are numerically studied. Methane- air mixture with detailed chemical kinetics is considered to model the combustion process inside the porous matrix. Assuming the non-local thermal equilibrium between solid and gas phases, separate energy equations are considered for two phases. Porous medium is assumed as a gray medium that can absorb, scatter, and emit thermal radiation, where the gas phase is considered to be transparent. The governing equations including gas and porous energy equations, the chemical species transport equation and the radiative transfer equation are simultaneously and numerically solved. Discrete ordinates method is used to solve the radiative transfer equation in order to calculate the radiative term in the solid energy equation. The simulation results include temperature fields for the gas and solid phase, species mass fraction distributions, and radiative heat flux profiles along the burner. Finally, the effect of different parameters such as optical thickness, scattering albedo, excess air ratio (EAR) and porosity on the performance of burner are explored.

Small-scale cogeneration systems, by using the micro-turbines, have provided required electricity and heat in Hotels and residential complexes over the years. Hotels with CCHP system has higher energy efficiency compared to other energy systems, since usescogeneration waste heat for heating and cooling applications. The main advantages of cogeneration systems are reduction in fuel consumption, lower greenhouse gas emissions and environmental pollutions. In this study, it was tried to further introduce these systems, their function and economic analysis at the national level, in order to extend their usage in different places such as office, industrial, commercial and residential complexes. One method is to use solar radiation to provide part of energy required for water heating. Energy consumption pattern in a large hotel over the years was considered and economic analysis was performed for different energy consumption scenarios. Payback period were computed of each scenario, in order to make a positive attitude towards the use of cogeneration systems utilizing solar energy.

Investigation of fluid-solid interaction has been studied as an introduction to simulate a wide range of engineering problems such as fluidized beds, sediment transportation and catalyst inks in fuel cells. An efficient method for performing such simulations is a combination of Lattice Boltzmann method (LBM) and Smoothed Profile Method (SPM). In addition, the operations in the SPM are local; it can be easily programmed for parallel processing. In this approach, the flow is computed on fixed Eulerian grids which are also used for the particles. Owing to the use of the same grids for simulation of fluid flow and particles, this method is highly efficient for purpose of parallel processing by means of GPU. In this study, a combination of Lattice Boltzmann method (LBM) and Smoothed Profile method has been implemented in parallel processing on GPU. For validation purpose, the fluid flow within a channel was investigated. Results suggest that computational time can be reduced up to 80 times by means of GPU.Then, drag force exerted on a sphere in fluid flow and the sedimentation of one sphere in a quiescent fluid were studied. Results show that performance of GPU can be increased up to 6.5 million fluid nods per second by using this method.