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Go to Editorial ManagerIn this proposed study, all environmental factors affecting the aboveground and buried pipes, such as solar radiation and temperature, and soil temperature, have been studied on the characteristics of flow inside the aboveground and underground pipelines by building a mathematical model using MATLAB based on energy balance equations. From the mathematical model, the effect of solar radiation on the aboveground section of the pipeline is significate. During March and an inlet temperature of 34 °C, the pipeline outlet fluid temperature will rise to 50 °C. Other parameters affecting the aboveground section of the pipeline, such as ambient temperature and wind speed, have a much smaller effect on the fluid temperature, and the temperature difference is approximately 4 °C between the highest and lowest pipeline outlet fluid temperature. The result for the underground section of the pipeline showed that the main affecting parameter on the fluid temperature is the burry depth of the pipeline, the deeper the pipeline depth the lower the temperature variation and the lower fluid temperature can be seen, at 1 meter of bury depth the minimum and maximum fluid temperature was 18 °C and 36 °C respectively, and at 5 meters of bury depth, the minimum and maximum fluid temperature was 26 °C and 31 °C respectively. This study also checks different process parameters. Some of these are fluid flow, pipe diameter, and pipe material. The effect of the fluid flow and pipe diameter has a similar impact on the fluid temperature (while fixing all the other parameters), the higher the fluid flow or the smaller the pipe diameter resulted in a better heat transfer and more considerable temperature difference, and vice versa. The final process parameter, pipe material, had little to no effect on the fluid temperature variation.
A two-dimensional mathematical model has been constructed by using finite difference method for representation the groundwater flow in both steady and unsteady states at the upper aquifer of Dibdibba formation. The hydraulic characteristics of this aquifer have been redistributed based on observed data for the period (1988• l 989). A verification test is added to check the model correctness by matching the calculoted levels with the ones observed for the year 2000.A model was set to predict the groundwater levels up to the year 2010. Results of prediction show a reduction in groundwater level about (Im) in the central parts of the study area compared to the level of this groundwater in the year 2000.0n the other hand, this decrease is reaches (0.5m) in the western parts of this area.
This research studied the critical load of composite columns theoretical and numerical by using ANSYS14 package depended on experimental tensile properties of composite specimens. The composite specimens were prepared by hand lay-up technique made from unsaturated polyester reinforced with glass fibers with different fiber volume fraction V f , aspect ratio (L/T), and angle of fibers for coarse and fine woven fibers. The critical load that obtained by using program (ANSYS 14) have also shown a good agreement with results that were obtained theoretically and the maximum difference was (0.7%). The results show that the maximum value of the critical load can be observed at V f =11%, L/T = (3.5) and θ = (0 º /90 º ) for fine woven fibers was (622.115N). Also its found the maximum critical load for coarse woven fibers can be observed at V f %=8%, L/T=(3.5) and θ = (0 º /90 º ) was (486.887N). Also the observed values of tensile properties and predicated values are scattered close to the (45 ˚ ) line.
The prediction of the concentration fields of pollutants released to the atmosphere is a key factor in assessing possible environmental damages caused by industrial emissions. To solve the concentration equation for gaseous or particulate effluents it is necessary to know as accurately as possible the velocity field and turbulence intensities at the atmospheric boundary layer in the region of interest. A two dimensional mathematical model based on the equations of fluid mechanics along with a modified non- isotropic k-ε turbulence model are employed to calculate the flow and dispersion at the atmospheric micro scale (distances of the order of kilometers). Results of investigation are obtained by using the finite volume method (FVM) to solve the average Navier Stock equations coupling with turbulent k- ε model. The calculation was carried out for plume flow from the industrial chimney with different plume velocities, wind velocities and heights of stack. The equations of model are solved with SIMPLE schemes. FLUENT program used to show the results of the plume flow at the variable parameters of wind and plume velocities and heights of stack, the code is applied to simulate several cases of flow and dispersion. Comparisons against experimental results show that the non-isotropic turbulence model has better ability to foresee the plume dispersion than the standard k- ε, in which the non-isotropic character of turbulence is relevant. The computational results show that the plume path and concentrations are correctly predicted by the numerical model.
In the present research, a Matlab program with a graphical user interface (GUI) has been established for studying the performance of a solar tower power plant (STPP). The program gives the ability for predicting the performance of STPP for different tower dimensions, ambient operating conditions and locations. The program is based on the solution of a mathematical model derived from the heat and mass balance for the tower components. The GUI program inputs are; tower dimensions, solar radiation, ambient temperature, pressure, wind velocity, turbine efficiency, emissivity and absorptivity for collector and ground and thermal conductivity and thickness for ground. However, the GUI program outputs are; temperature and pressure differences across the collector and tower, velocity in the tower, density of air in collector outlet, mass flowrate of air, efficiency for collector and tower, the overall efficiency and output power of STPP. The effect of the geometrical dimensions of STPP and some climatic variables on the plant performance was also studied. The results show that the output power increases with increasing the collector diameter, chimney diameter and solar radiation by an increasing of 0.282 kW/m, 0.204 kW/m and 0.046 kW/(W/m2) respectively.
The land surface erosion is controlled by multifarious of different parameters, such as slope, soil physical properties (texture, structure, permeability, etc.), rainfall, runoff, and crop cover. However, it is impossible to develop precise simplest mathematical model that can predict the values of land surface soil erosion due to the behavior of controlled parameters. This paper presents the Neural Networks Model for assessing land surface soil erosion as amass per unit area per unit of time. The model derives from the analysis data obtained from available literature and was formulated as linear regression model and back propagation algorithm neural model. Both models were built by correlating firstly five watersheds variables with land surface erosion and secondly ten watershed variables with land surface erosion. The coefficients for independent variables were highly significant for both models. The case of correlating 10- watershed variables with land surface erosion gives R=0.978 & 0.976 for both models which is higher than that for 5- watershed variables. The mean absolute relative error (MARE%) is another procedure that used in order to evaluate the accuracy of the model and The average error % is 0.025 for (5) variables and 0.0064 for (10) variables. Both the supporting practices (P) and the slope length and slope steepness (LS) coefficients have a marked effect on the amount of land surface erosion in the case of 5- watershed variables. The amount of land surface erosion show a high level of sensitivity to the content of fine sand% in soil (FS) watershed variables on The amount of land surface soil erosion.
A mathematical model to analysis three–dimensional forced convection turbulent flow in a novel solar air heater integrated with multiple rectangular capsules filled by paraffin wax-based on phase change material PCM was implemented. The investigations were performed under three airflow speed of (0.6, 1.2, and 1.8) kg/min and average solar flux of 625 W/m 2 . The results revealed that the delaying melting time and also lower the melting temperature of PCM by increasing airflow speed during the charging process. As well as, the freezing period is dependent on the airflow speed by inverse relation. Also, the data results represent that the useful energy rate and thermal storage efficiency were a strong dependence on the airflow speed. Moreover, it can be detected that the optimal freezing time and the air temperature rise of the heater were reached about 210 minutes with (12 – 1.5 °C), 150 minutes with (7.5 – 1.4°C), and 120 minutes with (5.5 – 1.5 °C), at airflow speed of 0.6, 1.2, and 1.8 kg/min, respectively, which can be used at night to supply some applications by thermal energy such as heating buildings and drying agricultural crops.
The present study aims to investigate the influence of heat treatment and surface finish on the behavior of crevice corrosion resistance of AISI 410 and 416 martensitic stainless steels thus, to quantify the conditions at which crevice corrosion minimize as possible. The experimental work carried out during this study involves material selection, chemical composition tests, specimens preparation before heat treatments, austenitizing at temperature range (925-1010˚C) and for holding time periods of (30, 45 and 90 min), air and oil quenching followed by tempering at heating range of (205- 605 ̊C) and for 45 min, micro hardness tests, specimens grinding, surface roughness measurements, crevice corrosion tests, crevice evaluation and microstructure tests. Theoretically, empirical equations for crevice maximum depth under the effect of surface roughness and hardness for both AISI 410 and 416 steels were determined. While for microstructure analysis, carbides average area was determined by using the ImageJ analysis program and a mathematical model was also predicted. Results showed that, as hardness and surface roughness increase crevice corrosion resistance decreases. Therefore, material treated by annealing can minimize crevice corrosion rates more than that treated with hardening.
The solar chimney is a natural draft device that uses solar radiation to provide upward momentum to the in-flowing air, thereby converting the thermal energy into kinetic energy through an air turbine which in turn can be converted into electrical energy. The main parts of the solar chimney power plant are a large circular solar collector, a tall chimney, and an air turbine. In this paper, a theoretical study was performed to evaluate the performance of a solar chimney power plant system in Basrah City, where sunny days and solar radiation are high. A mathematical model was developed to study the effect of various parameters on the output power of the solar chimney. I1 was found that the output power depends strongly on the chimney tall and the difference between the collector air temperature and the ambient air temperature as well as the outside heat transfer coefficient, which essentially depends on the wind speed.
This study presents solar chimney power plant integrated with sea water desalination system. A simple mathematical model is based on the conservation of mass and energy. The results show that the integrated system of solar chimney power plant and solar still can achieve simultaneously. The analysis is performed for both summer and winter at latitude 30 o N. It’s noted that, the water layer thickness is of a significant effect on the fresh water productivity while the dimensions of solar chimney and the solar collector are of a minor effect. The productivity of fresh water and output power for summer are the highest. The present work is compared with experimental data of the other work and showed a good agreement.
This study presents a speed control design for switched reluctance motor (SRM) drive based on PID controller. The applications of Switched Reluctance Motors (SRMs) have being increased day by day, but this type of motors represents a highly nonlinear system, therefore there are a lot of difficulties in modeling and controlling them. We have proposed a non-linear mathematical model of a four phases 8/6 poles SRM then simulated it through Simulink/Matlab facilities. The whole control mechanism consists of a hysteresis current controller to minimize the torque ripple and a PID speed controller. The control design results are then validated in real-time by Simulink/Matlab software package.
This study uses intelligent techniques to regulate brushless direct current speed (BLDC) motors. After these motors solved the problem of using brushes and commutators in traditional DC motors, they succeeded in replacing brushes and commutators with electronic commutators. Due to the use of electronic switching, brushless motor algorithms are more complex than those of conventional motors. In this study, to adjust the PID controller's settings (Kp, Ki, and Kd), a trial-and-error approach was taken, and a completely new method known as the settings of known PID controllers have been modified using the new Gray Wolf algorithm. A BLDC motor's main benefit is that it has easy speed adjustment across a broad range, whereas AC motors often cannot be controlled in this way. Through the use of Matlab/Simulink, the BLDC motor's mathematical model was developed and implemented. The simulation results show that in the first case, a PID controller effectively induces the turbulent dynamic behavior of BLDC under load and no-load conditions, and in the second case, the speed shows the lowest rise time, stability, overshoot, and stability conditions, and performs at its best. The characteristics of the traditional PID controller that regulates the engine speed must be regulated online to achieve the use of intelligent technologies, and the adjustment is done online using the neural network. The results showed that this technology, or feature - online tuning - is the most effective and reliable of all.