Gulf States are mostly arid and with little water precipitation and ground water that hardly supports 5% of the intense urbanization which have been developed and boomed in the last half century. Taking the advantage of having ten hours of sun in such regions, desalination by low energy membrane distillation (MD) can take a huge lead if hybridization with solar power takes place. In this work, we propose a small-scale applied solution by the low-energy solar-driven MDbased portable desalination unit. The hybrid system consists mainly of desalination unit, solar PV panel, and a solar collector. Moreover, a dual channel configuration of the DCMD is adopted, this will increase the apparent working area and thus increases the fresh water productivity. In ideal case, results show that the portable system is capable to produce 6.35 L/day of fresh water when feeding at 40?C. This high efficient energy-extensive design can serve as a prefect mobile survival kit for emergencies.
In this research experimental investigations have been carried out to study the effect of winglet vortex generator pairs on heat transfer and flow behavior. The delta winglet vortex generator (DWVG) pairs mounted on the inner wall of the tube with attack angle ?=10?, three different winglet heights (h=5, 7.5 and 10mm), and three spacings between leading edges (s=10, 15 and 20mm) are studied in terms of the Nusselt number and friction factor for the range of Reynolds numbers 5000-25000. The experimental results indicate that DWVG pairs result in a considerable enhancement in heat transfer rate (Nu) with some pressure penalty. It is observed that Nusselt number increases with Re and winglet's height. Friction factor decreases with Re but increases with winglet height. Middle spacing (s=15mm) yields highest heat transfer rate and pressure drop. The Highest thermal performance enhancement (TPE) was noticed for s=15mm, h=5mm at lower Reynolds number (Re=5000).
This paper aims to present exergy/energy analysis of the VRF technology to investigate its performance in tropical region. VRF is an advanced air conditioning system that is developed to manage the load variability by controlling the compressor speed and the expansion valve. The system is proposed to be implemented in Masdar city that is located in Abu Dhabi. Parametric studies were done after modelling the system on EES, where both the high and low pressures in the cycle were varied to obtain the corresponding COP range. It was noticed that COP increases non-linearly with reducing the difference between the evaporator and the condenser pressures.
Oil-infused surface is recently developed and widely studied for its promising droplet shedding capability and low surface energy to promote dropwise condensation for low-surface-tension fluids. Due to low surface tension of the infusing oil, it can spread on the condensate and form a cloaking layer, which will affect growth of the droplet. In this work, growth dynamics of condensed water droplets is studied both experimentally and theoretically. Water vapor condensation experiments on both oil-infused and un-infused superhydrophobic surfaces are carried out in environmental scanning electron microscopy (ESEM). A thermal resistance model for a water droplet system is demonstrated as well. Both experimental and predicted results show that droplets on oil-infused surface grows faster than that on un-infused nano-textured surface because the infusing oil replaces the vapor pocket beneath the droplet and increases thermal conductivity.
Swirling flows in pipes can be found in many industrial applications for separation or mixing purposes. Turbulent swirling flow generated using a new swirl generator with multi-radial holes which is located inside a larger cylindrical housing, is studied. The swirling flow exiting from the Swirl Cage supplies a long pipe where the Reynolds number based on the pipe diameter and average velocity is equal to 40836.67. Velocity measurements were conducted using Laser Doppler velocimetry. The results are discussed in relation with the mean fluid velocity. It indicated the inflow was transformed successfully into a symmetrical swirling flow from the velocity profiles. Profiles of the mean tangential velocity reveal a Rankine vortex swirling flow structure along the pipe. Backflow flow occurred in the mean axial velocity when the swirl number was equal to 1.5.
Phase separation using swirling flows is a technique used in inline separators. In the present study, an existing separator device uses swirling flow that interacts with a conical hollow bluff body to eliminate the air core. We use SST k-? turbulence model to simulate and investigate the characteristics of unsteady single-phase turbulent swirling flow interaction with a solid conical bluff body on a laboratory model. The numerical results show good agreement with experimental data. The results show the interaction with the bluff body increases the flow oscillation, especially at near the bluff body region.
A novel negative-dielectrophoresis based approach for switching of microparticles in microdevices is reported. Two sets of electrodes piercing the microchannel from both sides are used to generate an electric field that controls the location of the microparticles inside the microdevice. The microfluidic device consists of a glass substrate and a PDMS layer. The microfluidic device was fabricated using standard microfabrication. Several parameters that affect the switching of cells were numerically studied using FEM. Experiments were carried out using red blood cells to demonstrate the effectiveness of the microdevice in switching of cells to three sub-channels.
The main aim of this investigation is to design and implement a novel fluidic injection based jet noise suppressor for high speed flows. Contrary to previous studies which injected fluid either inside the nozzle or just at the nozzle exhaust, this injection scheme injects multiple microjets perpendicular to the jet axis at an axial location downstream from the nozzle exhaust via a coaxial injector tube. Microjet injection closer to the jet axis leads to the formation of counter rotating vortex pair (CVP) close to the injection location which further beaks down into stream-wise vortices as the microjet bends and follows core flow direction. Isothermal jet-injector configuration is tested for a Mach 0.9 single stream nozzle with continuous injection. Instantaneous aerodynamic fields are obtained using Large Eddy Simulation (LES) and the results are validated with previous experimental data. The results suggests that the presence of coaxial injector tube significantly alters the flow field leading to shorter jet core and a reduction in the far field noise. When the fluid injection is activated there is a decrease in the far field mixing noise due to the decrease in the turbulence in the jet resulting from enhanced mixing. The study involves analyzing the effect of multiple design and operating parameters on the mixing characteristics and far field noise.
Preform compaction and resin impregnation are two major steps in composite manufacturing by liquid composite molding processes. Understanding of the preform compaction and permeability characteristics is important for the process characterization and optimization. Existing methods either require a number of tedious experiments, at the cost of material and labor, or numerical simulations using geometric models of the reinforcement preform. Geometric modeling approaches of the preforms fail to capture the real architecture as well as the effect of the compaction of the reinforcements. This study presents numerical computation of through thickness permeability of two types of 3D woven fabrics by in-situ compaction characterization using micro X- ray computed tomography (?XCT). The study focuses on obtaining fiber deformations during compaction and converting them into computational mesh for flow analysis using ANSYS FLUENT. The real-time 3D images were obtained by in-situ compaction at four different fiber volume fractions. The ?XCT analysis revealed significant microstructure changes at high compaction levels. The flow field analysis revealed three dimensional flow paths within the preform. The computed through thickness permeability values agree well with the experimental data.
To improve students' achievement, the ADEK (Abu Dhabi Authority for Education and Knowledge) focuses more on improving policies, teaching practices, as well as curricula and focuses less on adolescents' developmental needs. Unfortunately, students in Al Ain schools are far from being ranked the best in the international exams. This could be explained in that the change did not consider changing different school climate practices that could satisfy the students' developmental need of belonging. This need is so crucial as it helps in increasing students' motivation to work harder and then to achieve more. Therefore, the main purpose of the study is to explore school climate factors and their influences on adolescents' sense of school belonging in Al Ain schools. A useful framework for exploring the school climate factors is Bronfenbrenner's ecological system theory (1979, 1993). This study will follow a sequential exploratory research design.
