Showing 6 results for Energy Analysis
Rohollah Talebitooti, Ali Akbar Torbaty,
Volume 13, Issue 14 (3-2014)
Abstract
In this paper, viscoelastic insulators are employed into an automotive brake system to improve the vibration stability. Thus, the system stability has been considered with hypothesis of couple modes. Therefore, the originality of the paper includes the complex eigenvalue analysis of viscoelastic model in brake squeal phenomenon. Accordingly, the brake system is simulated in a FEM code and then, the viscoelastic materials are applied using Negami-Havriliak model. Comparing the eigenvalue results in both cases, in which the viscoelastic material is treated as an absorber at the first case and without treatment for another case, indicates an improvement in instability mode at 12 kHz. In addition, applying these absorbers has no significant effects in low frequency. Furthermore, comparison of the results presented here with experimental ones done by other author, indicates the reliability of the presented model. Finally, with applying the strain energy analysis, the location of absorber treatment as well as its optimum thickness is concluded.
Roohollah Talebi, Mohamad Hassan Shojaeefard, Reza Ahmadi, Behzad Ranjbar,
Volume 14, Issue 6 (9-2014)
Abstract
In this paper, the sound behavior of a double walled composite with an intermediate porous layer has been conducted using the classical laminated plate theory (CLPT). The main objective of the paper is devoted to considering the analytical study of various boundaries on porous layers as well as parameter study on power transmission through the structure. Thus, viscous and inertia coupling in a dynamic equation, as well as stress transfer, thermal and elastic coupling of porous material are considered based on Biot theory. In addition, the equation of wave propagation are extracted according to vibration equation of composite layers. Then, with applying the various boundaries on the structures along with solving these equations simultaneously, the Transmission Loss (TL) is calculated. The analytical results are compared with both numerical ones obtained from Statistical energy Analysis (SEA) as well as empirical results and an excellent agreement is observed. The parametric studies are presented to investigate the effects of boundary conditions on TL. The results indicate that the interface of porous-composite layers as well as stacking sequences of the composite layers would play an important role in reduction of power transmission through the structure.
Aida Farsi, Mehran Ameri, Seyed Mohammad Hojjat Mohammadi,
Volume 16, Issue 12 (2-2017)
Abstract
Supercritical carbon dioxide refrigeration is a proposed system to provide extremely low temperatures. The waste heat from the gas-cooler is noticeable. So, it can be used as a promising heat source in other systems like multi-effect-desalination system (MED), in order to provide cooling and fresh water, simultaneously; as well as reduction of power consumption. In this paper, the energy analysis and comparison of two novel combined systems are carried out. The combined systems consist of CO2 refrigeration system and two MED's models, the Boosted model and the water preheaters (PH) model. The effect of operating parameters such as evaporator temperature, ambient temperature and compressor outlet pressure on system performances are studied. Results showed that for both combined systems, by decreasing the evaporator temperature or increasing the ambient temperature, the coefficient of performance (COP) and the distilled water flow rate, decreases and increases, respectively. On the other hand, increasing the compressor outlet pressure would increase COP and decrease distilled water flow rate up to an optimum point. Also, MED-Boosted could produce more fresh water compared to MED-PH. In order to decrease the power consumption of the combined system two methods are presented. In two compressors method the COP enhances 6.2% compared to the base system (consists of one compressor and an expansion valve). However, the produced fresh water would be reduced by 60%. On the other hand, the expander method could improve the COP by 23.4%, compared to the base system, while the amount of distillated water decreases less than 8%.
Mohammad Hosseinzadeh, Ali Salari, Mohammad Sardarabadi, Mohammad Passandideh-Fard, Alireza Akbarzadeh,
Volume 17, Issue 8 (10-2017)
Abstract
In this study, the performance of a photovoltaic thermal system (PVT) is investigated in a numerical and experimental study. In the numerical part, the Taguchi method is applied to determine the optimum place and time of the PVT system. Moreover, the optimum parameters that are independent of the design of the PVT system are obtained to improve the performance of the system in a specific place and time. Using the specified optimum parameters, the performance of the system is investigated from the energy and exergy viewpoints, experimentally. In the experimental study, using the designed setup, the performance of a water based PVT system is compared with that of a conventional photovoltaic unit (PV). The experiments are performed on a selected day in August at the Ferdowsi University of Mashhad, Mashhad, Iran (Latitude: 36° and Longitude: 59°). The numerical results indicate that the most effective parameter on the performance of the PVT system is the coolant inlet temperature and its optimal value is 20 °C. Moreover, the total energy efficiency of the PVT system in the optimum working condition is 69.02 %. The experimental results reveal that the average output electrical energy of the PVT system is 6.27 % more than that of the PV unit. In addition, the average thermal energy and exergy efficiencies of the PVT system are 34.12 % and 0.72 %, respectively.
S. Jhandydied, H. Hassanzadeh, S.e. Shakib,
Volume 19, Issue 11 (11-2019)
Abstract
In this study, a hybrid system of fuel cell/gas turbine was designed and simulated with the aim of coupling with desalination systems. This system was analyzed from the viewpoints of the first and second law of thermodynamics. A parametric analysis was also performed to the determination of the system optimal performance. The studied parameters are fuel utilization factor, compressor pressure ratio, pre-reforming percentage, and the steam to carbon ratio. The results show that for the design parameters, the net power is 1215kW, the overall efficiency is 81.65% and the exergy efficiency is 60.7%. Also, by analyzing the rate of exergy destruction, it has been determined that the stack of fuel cells, combustion chamber, and pre-reforming have the most part in the destruction of exergy. Parametric analysis results show that increases in pressure, pre-reforming percentage, and fuel utilization factor have a positive effect on the system performance to a certain extent and the suitable ranges of the fuel utilization factor are from 0.8 to 0.85. On the other hand, by analyzing the effect of pressure and temperature on the system, it is determined that the temperature of the fuel cell cannot be constant. It was also shown that the efficiency of the system decreases with increasing steam to carbon ratio.
M. Hosseinzadeh, H. Zamani, S.m. Mirzababaee, A. Faezian, F. Zarrinkalam,
Volume 20, Issue 6 (6-2020)
Abstract
In this study, a portable parabolic solar cooker is designed and fabricated, and the daily performance of the solar cooker is investigated from the energy and exergy viewpoints. One of the important challenges of the parabolic solar cookers is the reduction of their performance in the windy conditions. In order to evaluate this issue, the effect of 0.2, 2, 4 and 6m/s wind speeds on the energy and exergy efficiencies of the solar cooker is studied. Based on the results, the energy efficiency of the parabolic solar cooker is 34.52-46.19% and the exergy efficiency is 2.11-5.60% during the experiment. The experimental results indicate that water can boil in the windy conditions using the fabricated solar cooker although the time required to boil water increases by rising the wind speed. According to the results, in the wind speed of 6m/s, the time taken to boil 2 liters of water is about 40min. Furthermore, the energy and exergy efficiencies of the parabolic solar cooker in the wind speed of 6m/s are 20.08% and 1.99%, respectively, lower than those in the wind speed of 0.2m/s.
