Numerical Simulation of Heat and Fluid Flow Behavior in a Pipe Flow with Sinusoidal Boundary Condition

Abstract -In this investigation a two-dimensional airflow and heat transfer wit

Investigating of environmental traffic noise modelling by using FHWA TNM in Tehran township

There are several noise modeling software packages in order to predict noise level, each of them has different accuracy in different country. The present study was undertaken to analyze Traffic Noise Model software package (TNM) for two large highway in Tehran township. Firstly, field measurement for equivalent noise level (Leq) was carried out by sound level meter(SLM), then Leq prediction by the software was done. Finally, the results of the two previous steps were compared. the mean deviation of the results for sound levels below 80 dB was 0.33 dB, but for values further than 80 dB, the deviation was high. due to the obsolescence of a large number of the trucks inside Iran, new trucks instead of using software-defined trucks, were defined. With this change, the modeling and measurement results were more coordinated. The coefficient of determination (R2) increased from 0.4915 to 0.7312

Energy, Exergy, and Economic Analysis of Cryogenic Distillation and Chemical Scrubbing for Biogas Upgrading and Hydrogen Production

Biogas is one of the most important sources of renewable energy and hydrogen production, which needs upgrading to be functional. In this study, two methods of biogas upgrading from organic parts of municipal waste were investigated. For biogas upgrading, this article used a 3E analysis and simulated cryogenic separation and chemical scrubbing. The primary goal was to compare thermoeconomic indices and create hydrogen by reforming biomethane. The exergy analysis revealed that the compressor of the refrigerant and recovery column of MEA contributed the most exergy loss in the cryogenic separation and chemical scrubbing. The total exergy efficiency of cryogenic separation and chemical scrubbing was 85% and 84%. The energy analysis revealed a 2.07% lower energy efficiency for chemical scrubbing. The capital, energy, and total annual costs of chemical absorption were 56.51, 26.33, and 54.44 percent lower than those of cryogenic separation, respectively, indicating that this technology is more economically feasible. Moreover, because the thermodynamic efficiencies of the two methods were comparable, the chemical absorption method was adopted for hydrogen production. The biomethane steam reforming was simulated, and the results indicated that this method required an energy consumption of 90.48 MJkgH2. The hydrogen production intensity equaled 1.98 kmoleH2kmolebiogas via a 79.92% methane conversion

Increasing Biomethane Production in MSW Anaerobic Digestion Process by Chemical and Thermal Pretreatment and Process Commercialization Evaluation

One of the methods of municipal waste disposal and energy production is anaerobic digestion. This study investigates the effect of thermal and chemical pretreatment on the anaerobic digester’s biomethane production. The optimal condition was evaluated using RSM in two modes: maximum and minimum use of H2O2. The optimal state was obtained in the first case under 110.8 °C, 4.63% NaOH, 8% H2O2, and 111.9 °C, 4.47% NaOH, 2% H2O2 in the second case. Experimental results obtained 77%, 76.6% VS (volatile solid) reduction, and 89.1%, 88.7% SCOD (soluble chemical oxygen demand) reduction in the two optimum conditions, respectively. Experiment results were extrapolated to dry industrial digesters using a factor of 0.89% and durations including 30 days and 25 days. Then, the processes of biogas improvement were simulated. After biogas improvement, the economic analysis of the process was conducted with the definition of various scenarios. It was determined that, at current prices, pretreatment is not economically viable and that, with an increase in electricity prices to 0.09 $/kWh and 0.145$/kWh, the digestion process with a NaOH 4.47% 112 °C pretreatment, chemical scrubbing, and digestion with NaOH 4.47% 112 °C, 2% H2O2 are sequentially economically viable

Design of an optimal idle speed controller for a turbocharged diesel engine using fuzzy logic method

Idle Control of Internal Combustion Engines (ICEs) is one of the most important modules of Engine Management Systems (EMS) due to its effects on fuel consumption (FC) and pollutions produced in urban traffics. PID controllers are usually used for idle speed regulation. In this paper a PID like fuzzy controller is used to control the idle speed. The aim of this research is to introduce the selection method of membership functions for nonlinear processes which have unsymmetrical behaviors around working point. Also a simple yet useful graphical base approach to optimize fuzzy like PID controller is introduced. In order to design the controller a mean value model of a 1.6 turbocharged diesel engine is applied. In this model the effects of injection timing, injected fuel mass, ambient conditions and cycle by cycle torque generation variations are taken into account. The model also predicts the engine behavior in warm-up period. Two main manipulated variables of injection timing and injected fuel mass per cycle are handled to control the engine speed under different sources of engine speed variation such as external loads made by A/C, steering hydraulic pump or alternator and also the internal loads e.g. variable internal friction. The designed controller shows high robustness in response to change in ambient conditions

CFD Modeling of a Stirred Anaerobic Digestion Tank for Evaluating Energy Consumption through Mixing

The anaerobic digestion process is an effective means to eliminate the detrimental impacts of cattle manure discharge into the environment, i.e., biochemical contamination and substantial methane emissions, the latter leading to global warming. For proper operation of anaerobic digesters, an efficient mixing provides a relatively homogenous mixture of the feedstock within the tank. This study aims to investigate the mixing process and the total energy consumption needed for stirring by using an asymmetrical mixer. A further objective is to analyze the formation of stagnant volume and the velocity gradient in the digester in order to assure the mixing efficiency of the mixer type. The computational model is implemented as the finite volume method, and the rheological properties of the feedstock are considered. The results are validated by comparing the on-site power consumption of the mixer with the values obtained by the numerical torque. At various mixer speeds, the dead volume does not exceed 0.5% of the digester tank; however, with the increase of the mixer rotation speed, the energy consumption of the mixer increases drastically