Chemical looping combustion (CLC) is a promising candidate for cost-effective CO2 capture and better power plant performance. The CLC process uses an oxygen carrier for the separation of oxygen from air. The oxygen is then used for fuel combustion. In this paper, the technical and economic performance of a power plant using CLC with two methods of waste heat utilization from the plant exhaust gas streams is studied. The plant studied is a natural gas-powered plant of 50MWth gross energy. The waste heat is utilized either a steam turbine or absorption chilling. The economic analysis shows a higher economic value of the waste utilization for cooling purpose compared to additional power generation. For the absorption chilling system, the cost of electricity (COE) is about 5.5 cents/kWh and has a payback period of about 6.4 years.
The thermal efficiency of open-tank volumetric solar receivers is limited by the excessive thermal losses consequent to high temperature operation. A transparent floating cover which limits the thermal losses by radiation and convection can be considered to substantially improve the thermal efficiency of the receiver. Herein, we describe the optical efficiency of a particular cover design. A ray-tracing tool is used on a solid model to determine the transmission though the elements of the cover. Optical efficiencies over 90% are reported.
Solar Rankine refrigeration systems can be driven using low-grade heat from solar thermal collectors. In this paper the development and validation of a thermodynamic model of a coupled organic Rankine cycle-vapor compression refrigeration system (ORC-VCR) is documented. Good agreement is obtained with previously published reference data. Parametric system performance analyses to key design and operating parameters are presented.
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.
