جستجوی مقالات مرتبط با کلیدواژه "تحلیل ترمواکونومیک" در نشریات گروه "مکانیک"

Increasing energy consumption has led to the use of renewable energy sources to reduce environmental pollution and prevent global warming. The present work has been carried out with the aim of presenting and investigating a new combined cycle based on the gas turbine with biogas fuel and due to the high outlet temperature of the gas turbine, a steam Rankine cycle equipped with open feed water heater and the thermoelectric generator has been combined with it as the bottom cycle. The system is studied based on the variables of air compressor pressure ratio and air preheater temperature efficiency and analyzed from the viewpoint of the first and second laws of thermodynamics and thermo-economics. Also, to find the best-operating conditions, the system is optimized using the genetic algorithm in EES software by employing single and multi-objective optimization. The results showed that the thermal and exergy efficiencies in the base condition are 44.58 and 42.38%, respectively, and in the optimum thermo-economic condition are 49.45 and 47.01%, respectively. In addition, the LCOE in the multi-objective optimization condition was calculated at 17.50 $/GJ, which is 5.1% lower than the baseline.

In the present paper, a comparison was made among four carbon dioxide (CO2) horizontal direct-expansion ground source heat pumps by using the thermo-economic analysis. For four study cycles, the unit cost of heat (LCOH, $/kWhth) was determined for two cases with constant a) Space Heating (SH) and b) Domestic Hot Water (DHW) loads with the peak of 8kW. Upon the obtained results, the (EVC+HE) and (EC+IHE) were found to have the lowest unit cost of heat and the highest COP, respectively. Also, it was shown that for the SH/DHW loads, 19% /11% increase in the COP results in 11% /7.5% increase in the LCOH for the electricity cost of 0.025$/kWh. Also, for the mentioned percentages increase in the COP and considering the electricity cost of 0.25$/kWh, LCOH is increased by about 6% for the SH and DHW cases, respectively. It was also concluded that the configuration with the highest COP is not that with the lowest unit cost of heat.

Exergy and thermoeconomic analysis is an effective method for determining thermodynamic characteristics and optimizing thermodynamic-economic performance of refrigeration systems. The present study deals with exergy and thermoeconomic analysis of a variable refrigerant flow system with four evaporators used in the dairy industry. A computer code written in EEs software was used for system simulation. Impact of three refrigerants, R502, R1234ze and R134a, on thermodynamic-economic parameters of the system was investigated. In addition to calculation of exergy efficiency of refrigeration cycle for three mentioned refrigerants, effect of evaporation and distillation temperature on system exergy degradation and exergy efficiency of was also investigated. Results showed that R1234ze gas can be appropriate alternative for R502 and R134a gases. Results show that exergy destruction in compressor in reference temperature from 3.974kW for R134a refrigerant increases to 4.221 kW for refrigerant R502. Exergy destruction in the condenser in second level was calculated for all refrigerants. In thermoeconomic analysis, costs of components of variable refrigerant flow system were investigated and total costs for R134a-R502-R1234ze refrigerants were studied. It was observed that a lowest cost is related to R502 refrigerant and total annual cost for or R134a and R1234ze refrigerants are in the next ranks.

A solar electric-vapor compression refrigeration (SE-VCR) system has been proposed in this study. The SE-VCR system was investigated for different evaporating temperatures and months in Isfahan city. The system is simulated by software TRNSYS. the hourly cooling load capacities (heat gain) of a sample building during the different days were determined by using meteorological data such as hourly average solar radiations and atmospheric temperatures. The hourly total heat gain of the sample building and the hourly variations of various parameters such as coefficient of the performance, condenser capacity and compressor power consumption were calculated. the minimum photovoltaic panel surface area was determined to meet the compressor power demand according to the hourly average solar radiation data. also the economic calculations were performed for various sizes of solar system and It was found that adding solar system, is economically. also the annual consumption of carbon in the amount of 1241 kg for cooling saves.

In this work, a comparative study has been presented for the most common configurations of the CO2 supercritical single stage refrigeration cycle from energy, exergy, economic and environmental points of view. In order to find out the effects of degree of superheating, using an internal heat exchanger and using an expander instead of expansion valve on the performance of the supercritical CO2 refrigeration cycle, a thermo-economic analysis has been performed. The results show that the increasing of coefficient of performance of the cycle with dual expansion process is not considerable. Also, the use of an internal heat exchanger in a cycle by an expander is not beneficial. Moreover, using expander in basic cycle leads to an increase of 27.3 % in thermodynamic performance and a decrease of 16.1% in total cost rate. This cycle has the lowest penalty cost due to emission of CO2.

A once-through cooling water system is a major source of water and energy loss in power plants located in coastal areas of the Persian Gulf; the relatively high temperature discharged water causes some operational problems in these power plants. In addition, the once-through cooling system is a major source of environmental pollution in power plants located along the south coastline of Iran. On the other hand, Persian Gulf coastal areas suer from a shortage of natural fresh water; therefore, water treatment (natural fresh water production), and heat recovery from the discharged cooling water to the Persian Gulf is essential. In this research, heat recovery from the discharged cooling water to the Persian Gulf was studied, and application of the recovered energy for water treatment (fresh water production) using a multi-stage ash desalination system in thermal power plants was also investigated. For this purpose, a multistage ash desalination system was thermodynamically modeled, and then, a thermoeconomic model )based on exergy and economic analysis( was studied to determine the water cost. In the next step, a two-objective genetic algorithm was applied as a suitable optimization approach to obtain the optimal values of the decision variables (number of stages, top brine temperature, last stage temperature, terminal temperature dierence of brine heater and condenser). Exergetic eciency and the cost of water were considered the objective functions of the optimization procedure. By applying the optimization technique, the cost of water was minimized, while exergetic eciency was maximized. In addition, the eects of heat recovery on the cost of the water desalination process were studied, and results demonstrated that the cost of water desalination was reduced by 13% using heat recovery from the discharged cooling water. Also, a sensitivity analysis was performed in order to show the relationship between the cost of water and some important parameters of desalination systems.