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Turbulent mixing of multi-phase compressible jets formed within steam ejectors requires further investigation so that reliable models can be developed to aid in the ejector design process. As a step towards the non-intrusive measurement of the flow conditions in such a jet, tunable diode laser absorption spectroscopy (TDLAS) is used to investigate the development of an axisymmetric subsonic jet of air containing a high concentration of water vapour (with a relative humidity around 70%), and a co-flowing stream of dry nitrogen. The radius of the jet nozzle was 14 mm and the measurements were made at distances of 5, 10, and 15 mm downstream of the nozzle exit. At each downstream distance, TDLAS measurements of water vapour features at around 1392 nm were made using a discrete mode laser. At each measurement location, the absorbance was recorded and the water vapour concentration was determined by using an Abel inversion and by fitting spectral results from the HITRAN 2012 database to the measured spectra using custom MATLAB scripts. Simulation of the experimental jet conditions was used to assess the accuracy of analysis method, and results indicate an accuracy of better than ± 5 % in the water vapour concentration can be achieved using the method proposed in this paper

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Ejectors have no moving parts and are preferable to mechanical compressors in many applications, but ejectors typically have a relatively low efficiency. To aid in the ejector design process, thorough understanding of the turbulent mixing of multi-phase compressible jets is beneficial. This paper reports experimental results for Tunable Diode Laser Absorption Spectroscopy (TDLAS) measurements derived from an axisymmetric supersonic steam jet apparatus. In this experimental work, a supersonic steam jet nozzle exit of a diameter 13.6 mm was surrounded by a low-speed flow of dry nitrogen. The TDLAS system was traversed through the flow at three different planes downstream from the ejector nozzle exit: 15, 20, and 30 mm distance. At each of the three planes, line-of-sight measurements were made with the laser passing through locations between 0 and 15 mm from the jet centreline. Through the analysis of the TDLAS data and application of the Abel inversion method, the radial distribution of the pressure, temperature, and the concentration of the water-vapour were obtained. The key findings are that it is possible to determine key physical parameters using experimental TDLAS measurements when combined with a suitable numerical optimization approach

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Ejectors have no moving parts and are preferable to mechanical compressors in many applications, but ejectors typically have a relatively low efficiency. Efforts to understand the dominant factors which control the mixing-induced entrainment of the low pressure stream inside ejectors are on-going. In the case of steam ejectors, additional complexity in the mixing process arises because the steam expansion in the supersonic nozzle typically causes condensation. The mixing between the high speed and low speed flows in a steam ejector involves the supersonic turbulent mixing of two phase flow in the presence of pressure gradients which provides substantial challenges for modelling and simulation. This thesis demonstrates the application of a tunable diode laser absorption spectroscopy (TDLAS) technique in the study of a supersonic steam jet within the mixing chamber of an ejector-like apparatus. It is expected that the TDLAS data can provide useful information for future modelling efforts. The TDLAS method was first assessed within a non-flowing experiment using a gas cell with a 100 mm optical path length containing saturated water vapour at a pressure of 2.2 kPa. The TDLAS measurements for the temperature and pressure were then compared with reference values measured using independent instrumentation. The results demonstrated that temperature could be measured from the TDLAS data with an error between 0.34 and 0.44 %, and the pressure within error between 2 and 12% at the flow pressure saturation conditions in the gas cell. Before attempting the supersonic steam jet measurements, the TDLAS method was further tested through application in a simplified flow configuration involving a low-speed (subsonic) jet of moist air with a co-flow of dry nitrogen. The flow was nominally axisymmetric, so an Abel inversion method was developed to obtained the radial distribution of the absorption coefficient from the TDLAS data. Based on an assessment of the methods using simulated jet concentration data, the method should be capable of yielding concentration to within 6% for the conditions considered in this work. TDLAS measurements were obtained within an axisymmetric supersonic steam jet apparatus that was developed for this work. The supersonic steam jet nozzle exit diameter was 13.6 mm, and a low-speed flow of dry nitrogen surrounding jet. The nitrogen was used in the apparatus to provide a non-absorbing co-flowing stream that enabled the supersonic wet steam jet absorption to dominate the line-of-sight TDLAS measurements. The TDLAS was traversed through the flow at three planes downstream of the supersonic nozzle exit: 15, 20, and 30 mm. At each of the three planes, the line-of-sight TDLAS measurements were made with the laser passing through locations between 0 and 20 mm from the jet centreline. Through the analysis of the TDLAS data and application of the Abel inversion method, the radial distribution of the pressure, temperature, and the concentration of the water-vapour were obtained. Results were compared to CFD simulations using a non-equilibrium wet-steam model and the average error between the CFD simulations and the TDLAS measurements was between 4 and 24% in the case of the pressure and between 1.5 and 5% in the case of the temperatures. Suggestions for improvement to the TDLAS technique and computational simulation methods are offered.

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Flat solar collectors are extensively utilized in various domestic and industrial applications to reduce energy consumption. In this study, an-active flat plate solar collector (FPSC) with an internal absorber tube receiver was fabricated and tested in Al-Samawa city, Iraq (latitude 31.19◦N and longitude 45.17◦E). The ambient temperature and incident solar radiation at the experimental location were reached 39 ◦C and 840 W/m2 , respectively. In this study, the number of riser tubes connected to headers that are covered with a glass sheet in a conventional FPSC were replaced with a single serpentine-shaped collector tube covered with a plastic sheet. The proposed solar collector used a smooth copper tube with internal and exterior diameters of 9.5 and 12 mm, respectively, and a total length of 1000 mm. A TRNSYS model of a flat plate collector integrated with an absorber tube was developed, simulated, and validated using the experimental data. Temperature and flow rate data were obtained concurrently throughout the experiments to evaluate the performance of the fabricated solar collector. The temperature at the solar collector input stayed relatively constant at 37.7 ◦C, and the water flow rate remained constant at 0.75 L/min. The results indicated that the temperature at the solar collector output ranged from 52 to 61 ◦C, with an average of 58 ◦C. The efficiency of the proposed solar collector ranges from approximately 45% to 67%, with an average of 58%. Overall, the simulation results of the TRNSYS model are in excellent agreement with experimental data. The average discrepancy between the tests and simulations for temperature differential and collector efficiency is approximately 1%.

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A numerical study of the Buoyancy-driven flow in a porous enclosure, having a bottom heated wavy wall, filled with Cu-Al2O3/water hybrid nanofluid is performed using the local thermal non-equilibrium model. The non-dimensional governing equations of fluid flow and heat transfer are solved using the Galerkin finite element method. The state variables change in the porous enclosure is represented using the Darcy-Brinkman model. The impacts of various effective parameters which include nanoparticle volume fraction (0 ≤ Φ ≤ 0.04), Darcy number (10−5 ≤ Da ≤ 10−2), modified conductivity ratio (0.1 ≤ γ ≤ 1000), the number of undulations (1≤ N ≤ 5) and the amplitude of waviness (0.05 ≤ A ≤ 2). The results showed that the Darcy number is the first controlling parameter on the fluid flow and temperature distributions followed by A, N and γ. Additionally, the heat transfer rate is increased by increasing the thermal conductivity of the nanoparticles reaching its maximum value at Φ = 0.04. Furthermore, by comparing the temperature fields of the fluid phase and solid matrix, it is clear that the effects of the local thermal non-equilibrium are significant at a low modified thermal conductivity ratio and high Darcy number.

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Water-in-diesel (W/D) emulsion fuel is a potentially viable diesel fuel that can simultaneously enhance engine performance and reduce exhaust emissions in a current diesel engine without requiring engine modifications or incurring additional costs. In a consistent manner, the current study examines the impact of adding water, in the range of 5–30% wt. (5% increment) and 2% surfactant of polysorbate 20, on the performance in terms of brake torque (BT) and exhaust emissions of a four-cylinder four-stroke diesel engine. The relationship between independent factors, including water addition and engine speed, and dependent factors, including different exhaust released emissions and BT, was initially generated using machine learning support vector regression (SVR). Subsequently, a robust and modern optimization of the sea-horse optimizer (SHO) was run through the SVR model to find the optimal water addition and engine speed for improving the BT and lowering exhaust emissions. Furthermore, the SVR model was compared to the artificial neural network (ANN) model in terms of R-squared and mean square error (MSE). According to the experimental results, the BT was boosted by 3.34% compared to pure diesel at 5% water addition. The highest reduction in carbon monoxide (CO) and unburned hydrocarbon (UHC) was 9.57% and 15.63%, respectively, at 15% of water addition compared to diesel fuel. The nitrogen oxides (NOx) emissions from emulsified fuel were significantly lower than those from pure diesel, with a maximum decrease of 67.14% at 30% water addition. The suggested SVR-SHO model demonstrated superior prediction …

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The performance of microchannel with sidewall dimples and fillet profile in the bottom surface is investigated. Two dimple sizes of (0.5 mm and 1 mm) are systematically clustered along the channels with and without fillet are considered. The laminar flow regime is assumed with Reynolds numbers ranging from 200 to 1200. The results show that the dimples and fillet profile have a significant effect on the thermal performance of microchannel. The Nusselt number of the microchannels with 1 mm dimples is 20% higher than the plain microchannel. However, an increase in pressure drop of 10% was obtained. In addition, the fillet profile impacts the thermal performance of microchannels without pressure drop penalty increase. Combining both dimples and fillet profile causes a significant enhancement in the thermal performance. Nusselt number of microchannels heat sink with 1 mm dimple size and fillet profile is 60% higher compared to the plain microchannel.

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Renewable energy is a sustainable source of energy that never ends. Ejectors are reliable devices as they rely on solar energy to run. Ejectors can be used as an alternative to compressors in refrigeration systems or provide vacuum zones in various applications. Ejectors have no moving parts, compact, and stable operation. However, they have lower efficiency at the current time. There may be opportunities to improve ejector efficiency under some conditions and develop a thorough understanding of the impact of their design parameters. This paper presents the numerical simulations CFD study to investigate the effect of various design parameters on the flow structure inside an ejector. This was achieved by modelling a variable ejector geometry with the ideal gas flow. This is a CFD study with new approaches. The numerical model has been validated by conducting different meshing levels. Three mesh size has been suggested, and the medium size was considered. The results showed that the secondary inlet with a diameter of 90 mm resulted in a reduction with the generated vortices compared to the Model I result. Also, the effect of changing the diffuser throat to 45 mm in Model II, has shown improvement in reducing vortices.

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Ejectors are used widely in different vacuums applications. However, they still have low efficiency at the current time. Due to a lack of understanding of the ejector mixing process. This paper focuses on using Computational Fluid Dynamic (CFD) to understand the effect of condensation on the flow characterization after nozzle exit position. This was achieved by modelling a variable ejector geometry with two approaches: Ideal gas, and Wet-Steam models. The simulation outcome for both cases shows that the condensation process that occurs with the primary nozzle, led to a change in the static pressure and temperature magnitudes in comparison to the case without the condensation. The static temperature profile at NTP shows an increase within the static temperature in the Wet-Steam case with differences of approximately 180 K. In addition, the differences of static pressure after NTP for the two cases was approximately 1 K.

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The natural convection within enclosures along with entropy generation minimization plays a crucial role in various applications, particularly when they involve the utilization of nanofluids and porous media. This phenomenon plays a crucial role in enhancing heat transfer, fluid flow, and overall system performance. By understanding and optimizing the natural convection and entropy generation processes, it becomes possible to improve the efficiency and effectiveness of various thermal management systems, such as heat exchangers, electronic cooling systems, and renewable energy devices. Moreover, the integration of nanofluids and porous media introduces additional complexities and opportunities for enhancing heat transfer and fluid flow characteristics within enclosures. The current study investigates entropy generation (Sgen) and natural convection in a Z-staggered cavity filled with a porous media filled with a TiO2-water nanofluid. The symmetrical enclosures with dimensions of 0.6 L × 0.5 L are considered, and the media contain a porous material saturated with TiO2-water nanofluid. The wavy left and right vertical walls of the staggered enclosure were maintained hot and cold at temperatures (Th) and (Tc), respectively. All the straight horizontal walls were considered insulated and impermeable. The fundamental equations are solved using the Galerkin Finite Element Method (GFEM), and the results are described in detail. The key result was that raising the Rayleigh number (Ra) and nanoparticle volume fraction increased heat transmission. Specifically, increasing the Rayleigh number from (Ra = 105) to (Ra = 106) leads in an 80% increase in heat transfer. However, as the density of the nanofluid increases, the highest values of streamlines decrease. Decreasing the Darcy number (Da) educed the maximum values of the streamlines and average Nusselt number (Nu). Additionally, increasing the heat generation factor (λ) from (λ=0) to (λ=5) decreases the Nusselt number by 30%. Furthermore, the most effective streamline value was achieved at an inclination angle (γ) of 60.

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Small-scale wind turbines are considered recently as an attractive source of renewable energy, especially at remote area with respect to city centre. The design and characterization of a small vertical wind turbine are introduced through this work. A CFD analysis has been used as a first step in design to simulate the flow around the vertical blades of the small wind turbine. Different parameters have been taken into account in this work such as blades number, shape, and existence of stator blades deflector. Three different versions depend on blade profile have been examined. The turbulence model with sliding mesh in CFD have been performed. In this paper, a performance of small-scale of vertical wind turbine represented by CFD results of power coefficient, and optimal freestream velocity of this model are presented. The results showed that using 8 blades of VAWT instead of 4 blades with the same profile of blade has enhanced VAWT performance up to 64%. Also, increasing the concave profile of the blade can rise the torque produced by approximately 8%, however more increase in concave shape cause drop down by 5.6 %. Moreover, including stator deflector to the VAWT design has ability to increase the torque produced by 70 %. The output of these results will help to choose the optimum configuration of the small vertical wind turbine to implement this design experimentally as a next step.

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The coefficient of performance (COP) and exergy efficiency of a single and double-effect ammonia-water absorption refrigeration system powered by compound parabolic concentrating collectors were analyzed under various operating situations. A novel method was proposed using support vector machine regression and particle swarm optimization to identify optimal operating parameters. The optimal pressure-temperature conditions, including evaporator pressure (Pe), generator pressure (Pg), and absorber temperature (Ta) that maximize the COP and exergy efficiency while minimizing generator temperature (Tg) and evaporator temperature (Te), were investigated. The generator temperature was the main independent variable, ranging from 370 to 470 K. The findings demonstrated that the gain in COP and exergy efficiency caused by raising the generator temperature to more than 430 K is not cost-effective. The COP increased when the evaporator temperature increased along the investigated range of generator temperatures but yielded lower exergy efficiency in all cases. The exergy destruction rate in condenser, pump, recooler, reheater, and expansion valves is insignificant compared to other components. The generator has the highest exergy destruction rate regardless of operating conditions, making it the most crucial component of the absorption system. The optimization process findings showed that, at Pe = 2.8 bar, Pg = 14.5 bar, and Ta = 303.15 K, the maximum COP and exergy efficiency were 0.8483 and 0.3605, respectively, concerning the minimization of Tg and Te, which were 408 and 267 K, respectively. The model produced an acceptable performance with a high prediction accuracy (coefficient of determination > 0.99 and mean square error < 0.0064).

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This study will focus on the Kurdistan region of Iraq. Irrigation is an essential of agriculture, and the process of irrigation takes place by transfer of water from water source to farm. However, energy is the main aspect to consider when carrying out the irrigation process. Due to shortages of electricity and the high cost of diesel, there are difficulties in meeting the demands of irrigation. In this study, solar energy is considered as one way to design a solar water pump that can be used on farms in the Kurdistan region of Iraq. Photovoltaic solar panels have been assessed as a way to provide a successful solar water pump system with a minimum cost. The weather conditions for Duhok city in Kurdistan have been analysed to assess the solar water pump system for local use. The outcome of this study revealed that the solar water pump is applicable and can provide many benefits for the use of clean and renewable energy to transfer water from a water source to farms in the Kurdistan region of Iraq. A proposed design system with cost analysis is provided as an outcome of this study.

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During the last four centuries, there have been extensive research activities looking for green and clean sources of energy instead of traditional (fossil) energy in order to reduce the accumulation of gases and environmental pollution. Natural dye-sensitized solar cells (DSSCs) are one of the most promising types of photovoltaic cells for generating clean energy at a low cost. In this study, DSSCs were collected and experimentally tested using four different dyes extracted from Mentha leaves, Helianthus annuus leaves, Fragaria, and a mixture of the above extracts in equal proportions as natural stimuli for TiO2 films. The result show that solar energy was successfully turned into electricity. Additionally, DSSCs based on mixtures of dyes showed better results than those based on single dyes. Efficiency (η) was 0.714%, and the fill factor (FF) was 83.3% for the cell area.

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This study investigates the impact of ambient pressure and temperature on the spray behaviour of diesel fuel. Spray simulation tests were conducted using Ansys Forte in a 45-degree sector of a diesel engine under different ambient pressures (1, 4 and 8 bar) and different ambient temperatures (400, 600 and 800 K). Non-reactive conditions were used as they allow calibration of the model for predicting correct spray dynamics. The simulation results of diesel fuel showed that the spray penetration decreased with increased ambient pressure. However, the spray penetration region became longer and wider for diesel fuel because of increased ambient air temperature. With higher ambient temperature the evaporation rate increased.