فصلنامه مهندسی و مدیریت انرژی
سال هشتم شماره 3 (پیاپی 29، پاییز 1397)

Abstract : The long run incremental and marginal pricing are two different approaches for pricing of transmission and distribution networks usage. The main difference between these two methods is how to calculate the cost of using the network. In the first approach simulations are used, and in the latter, sensitivity analysis methods are used to determine the cost. In this paper, a novel analytical method based on long run marginal pricing with a new sensitivity analysis is presented that can show the effect of power injections on the buses over the long-term costs of the network reinforcement. Sensitivity analysis consists of three partial derivatives including 1) the sensitivity of network power flow due to increased power injection at the bus, 2) the sensitivity of the network reinforcement time according to the power lines change, and 3) the sensitivity of the present value of future reinforcement with respect to changes in time to reinforce. A practical distribution network, which is part of the transmission network, is used to illustrate the theoretical and practical principles of the proposed method. The results of the incremental and marginal approaches are compared in different system conditions. The results show that the proposed method can produce forward-looking charges that reflect the extent of network utilization level, as well as the distance between generation and consumption. The proposed method will also illustrate the factors that affect network tariffs.

 The purpose of this study is to evaluate Electricity consumption over the business cycles of industrial production of Iran during 1967- 2013. In this paper, the existence of co-integration between electricity consumption and industrial production is checked using ARDL approach and causal relationship between electricity consumption and industrial production is investigated. The results indicate a dual causality between electricity consumption and industrial production. Moreover trend cycle component of industrial production and power consumption is separated using Hedrick - Prescott (HP) filter. Assessment of the causality between components of trend variable and cycle variable shows a long-term relationship. Results indicated that in 2011 the industrial sector has the highest and in 2013, the lowest value-added. Despite of periods of sharp downturn in the industrial sector, during this periods, the power consumption is not reduced accordingly. Even in some periods electricity consumption was high, and it could be due to low price levels and corporation not paying enough attention to the energy costs in production. But after the approval of law of optimization of subsides, some industrial sectors reduced their electricity consumption.

Usually it is common to use the internal heat exchanger subcooler-superheater after the condenser and before the expansion valve in the compression refrigeration cycles. In this study, the effect of the heat exchanger is evaluated by using recovery heat exchanger after the compressor and before the condenser. For this purpose, the vapor compression refrigeration cycle with conventional heat exchanger and recovery heat exchanger by using R134a, R1234ze, R1234yf and isotropic R507A as refrigerants is studied by thermodynamic, heat transfer and economic analysis. The low capacity compression refrigeration cycle is simulated and the condenser and the evaporator heat exchangers is considered air-cooled by natural convection of air such as household refrigerators. The results showed that by using the recovery heat exchanger in the compression refrigeration cycle a significant reduction occurred in the total amount of heat exchangers area and the total cost function in the cycle. Also R1234yf has the highest decrease in the total heat exchangers area required in the cycle and greatest reduction in the total system cost and it is recommended to use in compression refrigeration cycles instead of R134a as refrigerant.

 In this study, the effects of turbulators as a passive method for heat transfer increment on performance of the heater of Mokhtar City gate station of Yasouj City has been evaluated. To analyze the performance and the effects of turbulators on the efficiency of heaters, steady state and incompressible flow of gas were simulated through ANSYS CFX 14.5. Turbulence model of shear stress transport (SST) has been used for modeling turbulated flow regime besides the wall. Also, by using simulation results, the important performance parameters such as friction factor, Nusselt number, and thermal performance factor were calculated. Furthermore, wire coil tube insert was used as a common turbulator. The results show that wire coil turbulator with a diameter of 10 mm in heaters with elliptical tubes and diameter ratio of 0.95 have the best performance.

Low radiation intensity heat transfer from methane blue flame becomes a challenge in the industry. The addition of soot into the flame can enhance the radiation. But the effect of adding soot on chain reaction of methane combustion and NO & CO emission has not been reviewed. In between, one of the most important factor is the size of the fine particles. So, the chemical kinetics study of adding soot and effect of particles size on of methane combustion was studied by EPM method and GRI3.0 mechanism. The results indicated that adding the fine particle leads to increase in adiabatic temperature and NO and CO pollutants. But large particle vaporize first in preheat zone and their effects are lower than fine particles. Also, equivalence ratio is an effective parameter on temperature variation caused by soot addition and very fine soot particles bring increase in temperature for all equivalence ratios.

Turbo expanders are rotary machine that recover energy by expanding of gas or steam and transfer it to electrical energy. Before application of these machines were in reducing pressure stations of power plants and big cities. By developing knowledge the possibility usage of turbo-expanders in other industries such as gas well is available. At first the conditions of gas well are studied then related process is simulated with HYSYS software. Regarding to software calculations it is observed that it is possible to use 3 turbo-expanders with power generation totally 12000 kw and then economic analysis is performed and results show the payback period is around seven years.

solid-state energy conversion technologies such as thermoelectric refrigeration and power generation require materials with low thermal conductivity but high electrical conductivity and Seebeck coefficient. Although semiconductors are the best thermoelectric materials, they rarely have the mentioned properties. Nanostructures such as superlattices, quantum wires and quantum dots provide novel methods to improve the solid-state energy conversion efficiency through electron and phonon transport engineering. In this work a semiconducting superlattice has been studied consisting of periodic nano layers of sillicon and germanium. Due to nano scale effects, conductive heat transfer does not satisfy Fourier's law of thermal conduction. The equation of phonon radiative transfer has been solved numerically. The results show that the thermal conductivity of the nano structure is much lower than the macro suructures with the same aspect ratio. It is also noticed that with constant ratio of layers thickness, more reduction in layers thickness causes more temperature jump at interfaces and consequently more reduction in effective thermal conductivity that finally improves the thermoelectric properties. The results show that the effective thermal conductivity depends on the density of interfaces per unit length.