ebrahim jahanshahi javaran

In this research, the performance of an asphalt solar air collector was experimentally tested and the daily thermal and exergy efficiencies of the collector were analyzed. The sun's radiant energy is absorbed by asphalt and converted into thermal energy. Then, it is transmitted to aluminum pipes buried under the asphalt and, finally, to the air passing through the pipes. A suction fan induces the ambient air to the collector. The experimental results show that the daily thermal efficiencies at mass flow rates of 0.007 (kg/s) and 0.014 (kg/s) are 11.98 % and 24.10 % and daily exergy efficiencies are 0.34 % and 0.66 %, respectively, showing the increase in daily energy and exergy efficiencies with increasing the air mass flow rate. In addition, results show that as the flow rate increases, the outlet air temperature decreases. The presence of temperature difference between the inlet and outlet of the collector in the last hours of the day, when the sun's radiation islow, indicates that asphalt acts as a thermal energy storage medium.

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 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.

This study used the lattice Boltzmann method (LBM) to evaluate water distribution in the gas diffusion layer (GDL) of cathode PEM fuel cells (PEMFCs) with porosity gradient. Due to the LBM’s capability of parallel processing with a GPU and the high volume of computing necessary, especially for small grids, the GPU parallel processing was done on a graphics card with the help of CUDA to speed up computing. The two-phase flow boundary conditions in the GDL are similar to the water transfer in the GDL of the PEMFCs. The results show that capillary force is the main cause of water transfer in the GDL, and gravity has little effect on the water transfer. Also, the use of GPU parallel processing on the graphics card increases the computation speed up to 17 times, which has a significant effect on running time. To investigate the gradient of porosity of GDLs with different porosity gradients, but the same average porosity coefficient and the same particle diameter have been evaluated. The simulation results show that the GDL with a 10% porosity gradient compared to the GDL with uniform porosity results in a 20.2% reduction in the amount of liquid water in the porous layer. Hence, increasing the porosity gradient of the GDL, further decreases the amount of liquid water in the porous layer. So, for the GDL with a porosity gradient of 14% this decrease is 29.8% and for the GDL with porosity gradient 18.5% this decrease is 38.8% compared to the GDL with uniform porosity.

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, 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.

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.