جستجوی مقالات مرتبط با کلیدواژه « liquefaction » 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).

Dynamic stability and liquefaction of tailings dams are great concerns for geotechnical engineers. In this study, the seismic response of the Esphordi mine tailing dam located in Bafgh seismic region of Yazd province is investigated. A finite-difference code (FLAC2D) is used to model the seismic liquefaction applying two constitutive criteria, namely Mohr-Coulomb and Finn-Byrne. For this purpose, a fish function is implemented into the code to simulate the non-linear elasto-plastic Finn-Byrne constitutive model. Horizontal and vertical displacements (subsidence) in the dam body, additional pore pressure, failure zones, and liquefaction due to seismic load were determined using the two selected criteria under the seismic load of the 6.4 magnitude earthquake occurred in 2005. Considering the type of behavioral model, Mohr-Coulomb and Finn-Byrne, the maximum horizontal displacement of 5 and 35 cm in the dam body and downstream, and subsidence of 4 and 23 cm at the dam crest and upstream are observed, respectively. Also, the calculated ratio of excess pore pressure (Ru), for both criteria, was less than the liquefaction limit (0.9), the maximum value of which was 0.7 for the Finn-Byrne criterion and 0.2 for the Mohr-Coulomb criterion. In general, the results show that considering the cumulative effect of the seismic load cycles in the Finn- Byrne model, this criterion provides a better understanding of the liquefaction phenomenon.

Refrigerant is one of the most important parts in a refrigeration cycle. In many refrigeration cycles, especially in the natural gas processing industry, propane is used as refrigerant due to its desirable thermodynamic properties. There are two ways for transferring propane and butane gases from extraction point to the consumption site: a) Pipeline and b) liquefaction and transport in liquid form. The most profitable method for transporting large quantities of propane and butane gases is liquefaction and transport in liquid form using storage tanks. Liquefaction at atmospheric pressure is the most common method for transporting large quantities of gases using specifically designed refrigerated ships. In this paper, a gas refinery butane and propane liquefaction cycle is described first and then simulated in HYSYS software. Afterwards, Genetic Algorithm is used to minimize the total power consumption of the liquefaction cycle, through connecting HYSYS and MATLAB softwares. There are 13 variables and 13 constraints for compressors and heat exchangers in the formulation of the optimization problem. The results of this constrained optimization problem show that the power consumption can be reduced by 12.49% compared to the base case.