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Sun, 19 Nov 2017 23:06:32 +0100FeedCreatorEnergy Equipment and Systems
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Feed provided by Energy Equipment and Systems. Click to visit.Determining the optimal size of a ground source heat pump within an air-conditioning system ...
http://www.energyequipsys.com/article_27563_4077.html
One of the most challenging issues in modern-day building energy management involves equipping the buildings with more energy efficient facilities. In this paper, a hybrid system for cooling/heating for a residential building is developed and optimized. The system consists of a ground source heat pump (GSHP) as well as an electric chiller (EC) and boiler. The model is implemented in MATLAB and optimized using NSGA-II. Two economic and environmental objective functions are considered: Net Present Cost (NPC) and Carbon Emission (CE); which are minimized simultaneously. The results indicated that when the building load is completely met by GSHP, much less carbon is emitted to the environment, while when the majority of the load is provided by EC and boiler, NPC is lower and CE is much higher.Thu, 31 Aug 2017 19:30:00 +0100Electromagnetic field analysis of novel low cogging force, linear switched reluctance motor, ...
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This paper deals with electromagnetic design and 2-D (two-dimensional) magnetic field analysis of novel low force ripple linear switched reluctance (LSR) motor. The configuration that has been presented here has a higher number of rotor poles than stator poles, and the purpose of this configuration is to improve the force ripple, which is the weak point of LSRMs. In order to illustrate the conformity of the design parameter’s stage in this study, the calculated values of the magnetic field and cogging force characteristics are compared with that of their desired values. Also, the proposed configuration is compared to a 6-4 and 3-phase conventional LSRM with similar number of stator teethes, number of phases, and constraints in volume. From the numerical analysis of a proposed novel configuration, it has been observed that this machine produces higher force per unit volume and almost similar cogging force when compared to a conventional LSRM with identical number of stator teethes, number of phases, and constraints in volume. The obtained primary electric and magnetic characteristics for the proposed configuration are verified with the help of 2-D FE computations.Thu, 31 Aug 2017 19:30:00 +0100Theoretical analysis of a novel combined cooling, heating, and power (CCHP) cycle
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This study presents a theoretical analysis of a new combined cooling, heating, and power cycle by the novel integration of an organic Rankine cycle (ORC), an ejector refrigeration cycle (ERC), and a heat pump cycle (HPC) for producing cooling output, heating output, and power output simultaneously. Three different working fluids—namely R113, isobutane, and R141b—have been used in power, refrigeration, and heating sub-cycles, respectively. Energetic and exergetic analyses of the proposed cycle have been conducted to demonstrate its efficiency. The thermal and exergy efficiencies are obtained as 71.08% and 38.3%, respectively. The exergy destruction rate of each component and the overall cycle have been calculated where it is shown that among all the components, the generator has a main contribution in the cycle inefficiency. Finally, the sensitivity analysis of the different key parameters on the performance of the proposed cycle has been investigated. It has been demonstrated that the proposed cycle performs well in high generator pressure and low evaporator outlet pressure, based on the first and second laws of thermodynamics.Thu, 31 Aug 2017 19:30:00 +0100An investigation on effect of backbone geometric anisotropy on the performance of infiltrated ...
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Design of optimal microstructures for infiltrated solid oxide fuel cell (SOFC) electrodes is a complicated process because of the multitude of the electrochemical and physical phenomena taking place in the electrodes in different temperatures, current densities and reactant flow rates. In this study, a stochastic geometric modeling method is used to create a range of digitally realized infiltrated SOFC electrode microstructures to extract their geometry-related electrochemical and physical properties. Triple Phase Boundary (TPB), active surface density of particles along with the gas transport factor is evaluated in those realized models to adapt for various infiltration strategies. Recently, additive manufacturing or freeze type casting methods enable researchers to investigate the performance of directional electrodes to get the maximum electrochemical reaction sites, gas diffusivity and ionic conductivity simultaneously. A series of directional backbones with different amount of virtually deposited electrocatalyst particles are characterized in the first step. The database of microstructural parameters (inputs) and effective geometric properties (outputs) is used to train a range neural network. A microstructure property hull is created using the best neural network model to discover the range of effective properties, their relative behaviour and optimum microstructure. The characteristics of models is shown that there is not any contradiction between the high level of TPB and contact surface density of particles, but the highest amount of gas diffusivity can be found in the microstructures with lower level of reaction sites. Also increasing the contact surface density has a negative effect on gas transport but the high level of TPB density is feasible in the full range of microstructures. In the other hand, TPB density and gas diffusion into the models are inversely related, although there are a limited number of microstructures with high level of reaction sites and acceptable gas diffusivity. Finally, using a simple optimization process, the microstructures with the highest level of reaction sites and gas transport factor are identified which have the backbone porosity of about 50%, and extremely higher gain growth rate normal to the electrolyte. Additive manufacturing and 3D printing methods will enhance researchers in the future to create the real directional electrodes on the base of these proposed models.Thu, 31 Aug 2017 19:30:00 +0100Performance evaluation of trapezoidal teeth labyrinth seal
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The present paper investigates the effects of the trapezoidal teeth labyrinth seal on the leakage amount in gas turbines. The influences of increasing the number of teeth from 1 to 6 with step 1 and the tip clearance s=0.5 to 7.5 mm on the leakage flow at different pressure ratios of PR=1.5, 2 and 2.5 are examined, comprehensively. The analysis is performed numerically using a Finite-Volume software with the k-ε turbulent model. The obtained results show a good agreement in comparison with the other research results. The results show that an increase in the number of teeth causes a decrease in the leakage flow. An increase in the tip clearance (s) from 0.5 mm to around 7.5 mm leads to a decrease in the leakage flow, like the step labyrinth behavior, while an increase beyond 7.5 mm results into a leakage increase, the behavior of the straight labyrinth.Thu, 31 Aug 2017 19:30:00 +0100Gasification of potato shoots: An experimental and theoretical investigation
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A thermodynamic equilibrium model was developed to predict the gasification process in a bench-scale fluidized bed gasifier. Potato shoot (leaves and stems) was used as the feedstock of the gasifier. The experiments were done in five different gasification zone temperatures (650, 700, 750, 800 and 850°C), with a feeding rate of 0.166 kg/hour, and two equivalence ratios (ER: 0.2 and 0.25). The produced gas was analyzed and the portion of each component was calculated from a thermodynamic equilibrium model. The data from the experiments were compared with those of the modeling in order to validate the model. For 650°C, the closest results of the model to experiment data were observed for CO2 at ER = 0.2, followed by CO at ER = 0.25 with errors of 7% and 21%, respectively. The least difference between the model data and the experimental data at 700°C was observed for N2 with the error of 26% and 22% for ER= 0.2 and 0.25, respectively. At 750°C, the predicted values conformed reasonably well to the experimental data for CO with error less than 7%. Regarding the least error, the most admissible results were seen at 800°C for N2 with ER= 0.25 with an error of 7%. In this case, the most acceptable results of the model were obtained for 850°C, in which the error in predicting the amount of CH4 at ER= 0.25 was 0. Owing to the applicability of potato shoot in the gasification process, it can play a great role in energy production.Thu, 31 Aug 2017 19:30:00 +01004E analysis and multi-objective optimization of gas turbine CCHP plant with variable ambient ...
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In this paper a gas turbine power plant including air preheater (recuperator), heat recovery steam generator and air cooler system was modeled. Eight parameters were selected as the design variables. Fast and elitist non-dominated sorting genetic algorithm (NSGA-II) was applied (to maximize the exergy efficiency and to minimize the total cost rate) for the mentioned cogeneration system. The total cost rate is included the investment cost, operational cost and environmental impact penalty cost. The presented work included Energy, Exergy, Economy and Environmental (4E) analysis in which all system design parameters were optimally estimated. The optimization problem was developed for variable ambient temperature (VAT) during a year and their results were compared with constant ambient temperature (CAT) during a year. The results for a simple gas turbine showed that at the optimum point, the exergy efficiency reduced about 5.6 percent and total cost rate increased about 4.4 percent when the results for VAT was compared with CAT situation. When the system included a gas turbine with preheater, the total cost decreased and exergy efficiency increased for 39% and 30% respectively (in comparison with a simple gas turbine system). The above percentages were 39.5% and 29.8% respectively for variable ambient temperature. Furthermore when the system included a gas turbine with both preheater and inlet cooling, the total cost decreased and exergy efficiency increased 41% and 34% respectively (in comparison with a simple gas turbine system).Thu, 31 Aug 2017 19:30:00 +0100The energy and exergy analysis of a novel cogeneration organic Rankine power and two-stage ...
http://www.energyequipsys.com/article_27570_4077.html
The energy crisis in recent years has led to the use of thermodynamic cycles that work based on renewable energies. Low-temperature cycles—such as organic cycles—are suitable strategies for the application of renewable energies. The present study proposes a novel cycle through the integration of a two-stage compression refrigeration cycle with a combined Rankine power and ejector refrigeration cycle by using the cascade condenser method. The fundamental idea of this cycle is to obtain refrigeration production at lower temperatures, and to achieve higher thermal and exergy efficiencies. The results showed that the new cycle recorded an 11.67 percent improvement in thermal efficiency and a 16.89 percent improvement in exergy efficiency compared to the basic cycle. Even though the network output of the cycle is reduced, a significant increase in the refrigeration capacity of the cycle is observed.Thu, 31 Aug 2017 19:30:00 +0100Economic optimization of solar systems in uncertain economic conditions using the Monte Carlo method
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Solar energy is an environmentally sustainable energy source as it is clean and inexhaustible. Solar systems are very common and cost-effective, thus, can be used for many home applications. In this paper, a new method is presented to optimize solar systems economically, regarding to energy cost fluctuations. In spite of conventional analyses, in which the inflation is considered constant, this method considers a probability distribution for inflation. The probability function of the life cycle solar saving (LCS) is then estimated by the Monte Carlo method. The expected value of LCS is used as the objective function. The standard domestic solar system is considered as a benchmark to show capability of the method. Three most important parameters of a solar water heating system are considered as manipulated variables. The optimal value of each parameter was found based on the proposed procedure, and employing the particle swarm optimization (PSO) algorithm as the optimization method. The results show that the collector area of 17 m2, collector angle of 42o, and storage tank of 100 l/m2 maximize LCS to the mean value of 9930 USD for the selected case study. Also, the probability distribution of LCS shows that the mean value of the payback time is 4.1138 years with standard deviation of 1.3182.Thu, 31 Aug 2017 19:30:00 +0100