جستجوی مقالات مرتبط با کلیدواژه "parametric study" در نشریات گروه "مکانیک"

In this paper, a new system is proposed for the hydrogen liquefaction based on geothermal energy, in which, the nitrogen is first converted to liquid, and then, is used as to temperature decrease the gas hydrogen, in the hydrogen liquefaction cycle. This system includes four sub-systems; an Organic Rankine Cycle (ORC), an ammonia-water absorption chiller, and two Claude cycles for hydrogen and nitrogen liquefaction. The geothermal fluid at a temperature of 200 ℃ and a mass flow rate of 100 kg/s is considered as the energy source of the system. The proposed system is assessed from the thermodynamics and economic viewpoints. Then, the effects of the compressor outlet pressure, the geothermal fluid inlet temperature, the evaporator temperature, and the generator temperature on the exergy efficiency, the cost of the produced liquid hydrogen, and the hydrogen liquefaction ratio are investigated through a parametric study. Also, increasing the compressor outlet pressure increases the power consumption of the system. Also, at the geothermal fluid temperature of 430 K, the exergy efficiency of the system is determined as 69%. Moreover, the results of the economic analysis show that the production cost of 6.629 (kg/s) liquid hydrogen will be 1.39 $/kg (7.79 $/GJ).

In recent years, the limitations of the non-renewable energy sources and the rising pollution of their overuse have led the attention to renewable and clean energy sources such as the potential energy in water resources. Because of vastly used water transportation pipelines and the existing extra pressure in these pipes, it has a high potential for generating electrical power using the in-pipe turbines. In this research, the designing, simulation, and power optimization of a particular kind of these turbines (lift type) are studied. The numerical simulation is performed by Ansys Fluent commercial package software using a 3D solver for unsteady and incompressible flow in conjunction with a proper turbulence model. After introducing the turbine's effective design parameters, the simulation of the in-pipe turbine with different geometry conditions and rotational speeds is performed and discussed. Then it is tried to enhance the generated power of the turbine using trial and error by changing the geometry conditions of the rotor. Lastly, by numerical simulation of different geometries and improving the generated power, the best turbine geometry is tested for experimental validation.

Lead (Pb) is one of the heavy metals having high and long-term toxicity even at very low concentrations which limits the reusability and recyclability of industrial wastewaters. In this study, the removal and recovery of Pb from synthetic wastewater by a new form of precipitation method named crystallization process in a batch system was investigated. This process has gained increasing attention in recent years because of being in access, low cost, high efficiency and no need to recover the used materials. The efficacy of removal was dependent on the factors such as pH, initial lead concentration, carbonate: lead molar ratio and amount of seed crystals. The results of the experiments performed in this study showed that when the pH is in the range between 8-9, the initial concentration of lead is 100 mg /L, the molar ratio of carbonate to lead is 3:1 and the amount of seed particles is 0.25 g dissolved in 100 ml, the lead removal efficiency is obtained as 99%. AAS, SEM and EDS analyzes were used to confirm and justify the above results.

Exergy analysis is a method for recognizing the value and type of system availability variation with regard to the surrounding environment. It also helps to find how macroscopic properties of the system change during a process. By exergy analysis, the proportion of each process in the internal availability transmission and the places of useful energy loss in the system can be determined. In this research, the energy and exergy analysis and the parametric study of a gas to liquid compact heat exchanger (737/0-32/11–SR type) in various working conditions are accomplished, based on experimental findings. For this purpose, the appropriate model for the heat exchanger is achieved by means of theoretical and experimental thermodynamic relations, based on geometrical characteristics.  The estimation of heat exchanger’s performance in the presented model is based on the ε-Ntu method. In this study, various working conditions are determined by changing some parameters like temperature, pressure and volumetric flow rate of air and mass flow rate of water. The variation range of these parameters is chosen to manifest an intercooler working conditions. For the assessment of system performance, energy analysis is performed by definition and evaluation of parameters such as effectiveness and pressure drop coefficient. Also, for exergy analysis parameters such as exergic efficiency and irreversibility coefficient are considered. The presented results focus on how the variation of working conditions affects the characteristic parameters of the compact heat exchanger.