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Go to Editorial ManagerIn this paper, a universal testing machine and an impact testing apparatus have been upgraded by using a high- accuracy data acquisition and control system interfaced to a personal computer with proper sensors and actuators. The purpose of upgrade is to increase the accuracy of the measurements and to perform advanced material testing procedures that are not possible with the old configuration. The modernization process not only permits the accurate data acquisition and convenient operation but also the ability to study the effect of strain rate on the tensile properties of materials. Also, an experimental study of the response of CFRP (Carbon Fiber Reinforced Plastic) material to low and intermediate strain rates has been carried out.
The Atmospheric Water Generator (AWG) is an environmental water recovery that easily dehumidifies water vapor moisture from the air. This article presents an experiment to construct an AWG model using solar energy as a source of power. An experimental and numerical study for a device of (AWG) is performed. The experimental work is performed at Basrah city, located in the south of Iraq, during August and September of 2019 and March of 2020. The theoretical results are calculated by EES and the numerical study has been conducted by the (ANSYS19/CFD/ FLUENT) program. The experimental device is tested for different days with different climate conditions. The Maximum water production obtained is 3.4 L/day from all the testing days, for different hours of operation when the relative humidity in the range of (45 – 95 %) and the temperature range from 17 °C to 45 °C. The results shown that, the water production rate is increased with increasing humidity, temperatures, hours of operation, and model size.
Failures in the steam tubes of boiler furnaces in Najebia power plant was studied experimentally. Visual examination, mechanical tests, microscopic test and chemical analyses were performed. Visual examination showed the types of failure in the tubes. Tensile and hardness tests were performed to estimate the variation in the mechanical properties of the tubes metal and compared with the new tubes. Microscopic test for the failed tubes used to recognize the difference in the microstructure to the metal of the tubes. Chemical analyses involved chemical composition of the tubes metal, river and feed water analyses, water treatment, fuel analyses and analysis of deposits and oxides on the external and internal sides. Overheating and wall thinning of the tubes resulted from oxygen escaping to the inner side of these tubes, and presence of deposits and oxides on the external and internal sides which led to failure was studied extensively. Engineering remedies were also given to confine the problem and to prevent it in future.
In this study, a numerical investigation has been carried out for single phase flow behavior for thirty six internally finned tubes to demonstrate the effect of axial pitch to fin height ratio (p/e) for 0.8≤p/e≤6.345, helix angle of internal fins (β) for 30°≤β≤70°, apex angle of internal fins (α) for 0°≤α≤53.13°, internal fin height (e) for 0.6mm≤e≤1.0mm, internal tube diameter (di) with 14 mm and Reynolds number (Re) of single phase flow for 10000≤Re≤50000 on enhancement of forced convection heat transfer and reduction of friction factor by using ANSYS CFX program. It solves the three- dimensional Navier-Stokes equations for steady state turbulent with SST model and enhance wall treatment. The numerical analysis provided at fully developed velocity and temperature. Numerical results showed that the smallest axial pitch to fin height ratio (p/e) =0.8 and with apex angle α=10 degree provided enhancement of heat transfer of 2.8 to 3.55 times higher than of smooth tube. Finally, present numerical results are seen to be in good agreement with literature experimental correlations.
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.
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 incorporation of thermal energy storage materials (TESMs) into solar energy systems is a factor that boosts the performance of these systems. In this paper, an experimental study was addressed for enhancing the heat pipe’s thermal performance that works with an Evacuated Solar Tube Collector with Heat Pipe (ETCHP) as a solar water heater system. This is done by adding micro-zinc oxide (ZnO-MP) to the paraffin wax integrated as TESM into the evacuated tube (ET) of the system, where the evaporator section of the heat pipe is completely submerged within the micro-enhanced paraffin wax. Three experimental prototype rigs with one evacuated tube were designed, built, and tested to do the investigation. The most important parameters that have been studied in this study are the thermal resistance and the temperature distribution pattern along the heat pipe. The results show a clear indication of the decrease in the thermal resistance of the heat pipe of the proposed system compared to the system in which pure paraffin wax was incorporated. Also, it was noticed that there is a significant improvement in the temperature distribution along the heat pipe due to the improvement in the conductivity of the micro-enhanced wax compared to the pure wax.
The panel absorbed solar radiation and majority of this radiation is transform into a heat, and it is usually wasted and useless. At higher cell temperature, the current out of the cell has an unnoticeable rise, but the voltage value will drop significantly, resulting in a reduction in maximum power produced. The cooling method is therefore beneficial to keep the panel at the operation temperature. A simulation model is developed using COMSOL Multiphysics software version 3.5 software to investigate the enhancement in performance of a PV water cooling module (PVW module) based on a passive and simple cooling technique using a wetted cotton porous wick attached on the PV panel's back side and compare with uncooled PV panel (PVREF module). Unsteady, laminar and 2-D, the flow in the proposed modules is assumed. The input parameters were taken from a real weather condition was perform in Najaf-Iraq. The effect of variation of mass flow rate is also studied in the present work. Good agreement was obtained for PVREF module with previously researches.