نشریه مهندسی مکانیک و ارتعاشات
سال دهم شماره 4 (پیاپی 37، زمستان 1398)

Recently, with reducing the energy resources and increasing the energy costs (price), the energy saving has been attracted any more. Pinch analysis of an industrial process has been employed to identify pinch point and energy price together with heat exchanger network cost. To do so, we simulate the refinery process using Hysis software and analyze the results with Aspen Energy Analyzer. After validating the model using field data, simulated model was studied. The results showed with 1.7E04 $ investment, 31492$ will be returned annually using modified retrofit network. The payback time would be 180 days. In this paper, the Pinch Point is investigated and analyzed at various temperatures using Aspen Hysis software and Aspen Energy Analyzer software. In addition, economic calculations related to operating costs (energy) and total costs have been done. With the modification of the above-mentioned heat exchanger network, notable saving will be earned for the mentioned organization. So, the return period of capital will be approximately 180 days (less than one year) for the mentioned organization in this model.

One of the major challenges in the world is the need for energy resources due to its increasing demand and this demand is constantly increasing. In this regard, this paper presents a new method to determine the optimal location and size of energy storage in the micro grid by considering discrete models such as power supply and battery charge and discharge to meet technical objectives such as loss reduction and economic objectives. Battery investment and maintenance costs are provided. Based on the results, it can be stated that the batteries will continue to charge and discharge according to the target function selected for their installation and capacity determination.

In this paper, the effect of carbon nanotubes on the fracture energy, first and second modes of nanocomposite is investigated. For this purpose, a nanocomposite with 0.5 wt.% Carbon nanotubes was made experimentally in the laboratory. Using an ultramicrotome technique, cutting the nanocomposite sample and prepared it for transmission electron microscopy (TEM). Then, the diameter, length, and curvature of the carbon nanotubes were determined by transmission electron microscopy (TEM). The XFEM method investigated the crack growth in nanocomposites. Using SEM images and equations, the nanocomposite fracture energy was obtained. The results showed that by increasing the weight percentage of carbon nanotubes to the matrix, the stress intensity factor increased. Also, the fracture energy of the nanocomposite reinforced with 0.5 weight percent of carbon nanotubes increased by 29.6% compared to the matrix. The results were compared with the numerical and experimental results and were in good agreement with each other.

In gas pressure reduction stations, due to the equipment installed and the geographic location of the station, in order to maintain the safety and health of the station, appropriate measures are needed to measure noise and reduce noise. Due to the high noise pollution, the TBS gas pressure stations are compared. Therefore, in this research, an appropriate model and a mathematical program to analyze the intensity level of sound at different intervals from the source of sound and various frequencies and different sound power in a non-insulated state and in insulated mode, by changing the surface density of the insulator, it examines the effect of reducing the level of sound intensity. The most important results are: Reduces the intensity of the sound by increasing the distance from the sound source. Voice intensity increases with increasing sound power at identical intervals from the sound source. As the distance from the sound source increases, the intensity of the sound decreases with decreasing frequency. With increasing insulating surface density, the level of sound balance decreases at identical intervals.

In this work, natural convection in a two-dimensional enclosure with different shapes filled nanofluid with heat generating/absorbing in the presence of a magnetic field is simulated by LBM. The left vertical wall of the enclosure is examined in two modes: constant temperature heating and linear temperature heating and the cold wall of the enclosure in three different forms (a) diagonal, (b) curved and (c) smooth. The effect of parameters such as Hartmann number, nanoparticle volume concentration, heat generation/absorption coefficient, cold wall shape and type of wall heating on the nature of flow and heat transfer is evaluated. The results show that in all cases, increasing the Hartmann number and heat generation/absorption coefficient decrease the Nusselt number. The effect of Hartmann number in different states is different. The highest heat transfer also occurs when the vertical wall has a constant temperature. The effect of the magnetic field is greater when the cold wall is smooth. The effect of adding nanoparticles to the base fluid on decreasing or increasing the average Nusselt number depends on the Hartmann number and heat generation/absorption coefficient.

Due to the fresh water shortage crisis in all around the world, many types of desalination systems have been developed. One of the most used type of them is solar desalination system. In this paper, a parametric study has been employed for investigation of the effects of mounting a normal and porous fin on the heat transfer and water production rates of solar still desalination. A fin with different porous intensity in different positions has been put in solar desalination. For modelling the mentioned desalination, the desalination geometry has been meshed and the 3D simulation has been performed using ANSYS Fluent software. As the result of simulation, putting fin in optimum position in a solar still desalination leads to considerable increment of Nusselt number which results in increase of mass transfer and fresh water production rates. In addition, employment of porous fin will cause decrease in heat transfer and mass transfer rates. Finally, the effects of adding fin on the vortexes in the desalinator and its impacts on temperature and mass fractions differences in various zones has been also examined.