Collector Diameter Research Articles

Optimizing of solar chimney performance using electrohydrodynamic system based on array geometry

The effect of the electrohydrodynamic system with various electrode layouts on a solar chimney pilot is investigated experimentally. A pilot setup was constructed which consisted of a chimney with 3m height and 3m collector diameter. The purpose of this research was to enhance the solar chimney performance with the electrohydrodynamic system for the parallel, radial, and symmetric layouts. By using of corona wind, the outlet fluid temperature is increased, and the outlet absorber is decreased. For the three layouts, the most growth in the outlet fluid temperature is 14°C, which is observed in the parallel layout. Also, in the parallel array, the most outlet absorber temperature drop is 7°C. The results show that parallel layout with six electrodes and 3cmspacing between the electrodes has the best performance. Also, various hours of the day are studied and the best time for turning on the electrohydrodynamic system is 1:00p.m. The electrohydrodynamic system makes an increase in the fluid velocity from 1.7 to 2.3ms−1, and this growth improves the performance about 28%.

On the Influence of Collector Size on the Solar Chimneys Performance

Performance of solar chimney power plant system is highly influenced by the design geometries. The collector size is logically enhances the solar chimney performance, but the trend of enhancement is not yet investigated. In the present work, experimental and numerical investigations have been carried out to ascertain, in terms of qualitative and quantitative evaluation, the effect of the collector diameter. Daily thermal efficiency has been determined at four different collector diameter. Two different collector diameters, 3.0 and 6.0 m, have been investigated experimentally, and then scaled up, to 9.0 and 12.0 m, by numerical simulation using ANSYS-FLUENT®15 software. Results demonstrated that collector diameter has effectively influenced the system performance. Larger collector diameter imposed increase in the velocity, temperature and the daily average thermal efficiency of the system. From the experimental results, increasing the collector diameter from 3.0 to 6.0 m has increased the daily average thermal efficiency of the collector from 9.81 to 12.8. Simulation results at 800 W/m 2 irradiation revealed that the velocity in the chimney have increased from 1.66 m/s at 3.0 m collector diameter to 2.34, 2.47 and 2.63 m/s for 6.0, 9.0 and 12.0 m collector diameters, respectively.

Experimental and Theoretical Investigation of Performance of a Solar Chimney Model Part II: Model Development and Validation

A mathematical model based on the momentum, continuity, and energy balance equations was developed to simulate the behavior of the airflow inside the solar chimney system. The model can estimate the power output and performance of solar chimney systems. The developed mathematical model is validated by the experimental data that were collected from a small pilot solar chimney; (the experiment was presented in part I(. Good agreement was obtained between the experimental results and that from the mathematical model. The model can be used to analyze the solar chimney systems and to determine the effect of geometricalparameters such as chimney height and collector diameter on the power output and the efficiency of the system.

Modeling of the deep granular bed clogging by nanoparticles

Abstract Nanoparticle aerosols are a potential health hazard and are increasingly used in industry. Effective means for their filtration to avoid occupational exposure are necessary. Granular bed filtration exhibits interesting properties in terms of ultrafine particle collection efficiency or retention capacity, which could make them a good alternative to the fiber filters commonly used in industry today. Being able to predict changes to their collection efficiency and pressure drop during clogging appears essential for the design, optimization and control of the filtration process. To meet these needs, this study presents a predictive model for the different phases of deep-bed clogging. The model developed successfully describes changes to collection efficiency and pressure drop using equivalent collector diameters. Microscopic observations showed these equivalent diameters to be compatible with considering the deposit as a uniform spherical layer all over the collector’s surface. The predictions of the model agreed well with data from several clogging experiments for which various operating conditions were used, i.e., different collector’s diameters, particulate materials or superficial velocities.

Performance analysis of a solar chimney power plant for rural areas in Nigeria

Diverse renewable energy technologies are urgently needed, especially for developing countries. This paper aims to create awareness of solar chimney power plants (SCPP) as a viable and sustainable alternative in rural communities with limited or no access to the grid. The study considers site-specific hourly meteorological data in assessing the feasibility of SCPP in seven selected regions in Nigeria. A theoretical model was established for power output, levelized cost of electricity (LCOE) and avoided carbon emission predictions. Additionally, the effects of seasonality on solar radiation, ambient temperature, and power output were examined. The results show that SCPP with a collector diameter of 600 m and a chimney height of 150 m would produce an average power of 154–181 kW on a typical day under Nigeria conditions. Considering a lifetime of 40 years, LCOE varies from 0.216 to 0.254 €/kWh compared to 0.563 €/kWh for the widely-utilized diesel generators, and the annual carbon emissions mitigated varies from 162 to 191 tons. Moreover, the analysis suggests that the proposed SCPP would improve the social, economic and environmental development in the regions. Overall, the study shows that SCPP could be utilized to enhance energy access in the rural areas of Nigeria.

Performance optimization of evacuated tube collector for solar cooling of a house in hot climate

ABSTRACTEvacuating the space connecting cover and absorber significantly improves evacuated tube collector (ETC) performance. So, ETCs are progressively utilised all over the world. The main goal of current study is to explore ETC thermal efficiency in hot and severe climate like Kuwait weather conditions. A collector test facility was installed to record ETC thermal performance for one-year period. An extensively developed model for ETCs is presented, employing complete optical and thermal assessment. This study analyses separately optics and heat transfer in the evacuated tubes, allowing the analysis to be extended to different configurations. The predictions obtained are in agreement with experimental. The optimum collector parameters (collector tube length and diameter, mass flow rate and collector tilt angle) are determined. The present results indicate that the optimum tube length is 1.5 m, as at this length a significant improvement is achieved in efficiency for different tube diameters studied. Finally, the heat generated from ETCs is used for solar cooling of a house. Results of the simulation of cooling system indicate that an ETC of area 54 m2, tilt angle of 25° and storage tank volume of 2.1 m3 provides 80% of air-conditioning demand in a house located in Kuwait.

Multi-Objective Optimization of a Solar Chimney Power Plant with Inclined Collector Roof Using Genetic Algorithm

This paper presents an optimization of a solar chimney power plant with an inclined collector roof using genetic algorithms. Five design parameters that affect the system performance are the collector radius, collector inlet height, collector outlet height, chimney height and diameter. A multi-objective design to simultaneously optimize three conflicting objectives including system efficiency, power output and expenditure is used. Based on this approach, obtaining the best combination of the possible geometrical parameters, performance of two built pilot power plants in Kerman (Iran) and Manzanares (Spain) are optimized thermo-economically. The heights of the zero-slope collectors of the Kerman and Manzanares systems are 2 m and 1.85 m, respectively. The results show that in the Kerman pilot the optimal collector inlet and outlet heights are 1.5 m and 2.95 m, respectively, while those optimal heights in the Manzanares prototype are 1.5 m and 4.6 m, respectively. It is found that selecting the optimal collector roof configuration in addition to the other design parameters has a significant effect in the system optimization process.

Optimization of rotating-jet electrospinning process using response surface methodology

Rotating-jet electrospinning method is one of the efficient techniques for producing aligned nanofibers. This paper reports an accurate investigation on the influence of collector diameter (CD), voltage, polymer concentration (PC), and insulator length (IL) of spinneret on the degree of fiber alignment (DFA), production rate of fiber, and fiber diameter. The polymer solution was a mixture of polyacrylonitrile and N,N-dimethylformamide. The ranges of independent variables were 20–50 cm for CD, 10–22 kV for voltage, 13–19 wt% for PC, and 0.5–3 cm for IL. To minimize the number of required experiments for a complete evaluation, response surface methodology (RSM) and central composite rotatable design were applied by means of Expert Design Software. After defining the upper and lower bounds of the above independent variables in the software, 30 unique experiments were delivered. The recommended operating conditions by the software were exactly applied in the laboratory and the corresponding values for the DFA, production rate, and fiber diameter were measured. The nanofiber morphology was examined by scanning electron microscopy (SEM). By applying the least-squares method in the DX7.0.0 software, well-fitting polynomial correlations to the experimental results were obtained, and using these correlations, the influence of independent variables and responses was comprehensively studied. Finally, the best values of independent variables for optimizing the responses were determined using RSM.

A new economic feasibility approach for solar chimney power plant design

Solar chimney power plants have been accepted as one of the promising technologies for solar energy utilization. The objective of this study is to propose an effective approach to simultaneously determine the optimal dimensions of the solar chimney power plant and the economic feasibility of the proposed plant. For this purpose, a two-stage economic feasibility approach is proposed based on a new nonlinear programming model. In the first stage, the proposed optimization model which determines the optimal plant dimensions that not only minimize the discounted total cost of the system, but also satisfy the energy demand within a specified reliability taking into account the stochasticity of solar radiation and ambient temperature is solved using a commercial optimization solver that guarantees finding the global optimum. In the second stage, the net present value of building the plant is computed by deducting the discounted total cost found in the first stage from the present value of revenues obtained due to selling the electricity generated by the plant. The proposed approach is novel because it determines the optimal dimensions of the plant together with its economic feasibility by taking into account the energy demand and uncertainty in solar radiation and ambient temperature. The proposed approach is applied on a study in Potiskum, Nigeria, which reveals that building a plant with a collector diameter of 1128m and chimney height of 715m to Potiskum would be profitable for investors at an annual rate of return of 3% and would provide electrification to about 7500 people with a high level of reliability. The proposed approach is benchmarked with an intuitive approach and an approach that does not consider uncertainty in solar radiation and ambient temperature. The results clearly revealed the value of the proposed approach. Managerial insights on the impact of the efficiency of the collector, the efficiency of the turbine, electricity price, electricity demand, meteorological conditions, and discount rate on the size of the plant and the net present value are obtained through detailed sensitivity analyses.

Experimental investigation of solar tower with chimney effect installed in CRTEn, Tunisia

This paper studies the performance of a solar tower power plant (STPP) with chimney effect based on renewable energy proposed for electricity production. That's way, a solar tower prototype was constructed and tested in the Research and Technology Centre of Energy (CRTEn), Borj Cédria, northern Tunisia.The design involves heating air using solar energy and the chimney effect to raise the hot air up the chimney stack. The hot air velocity increases by the use of a convergent nozzle to reach a suitable velocity which can run the wind turbine. The kinetic energy of the hot air is then converted to electricity by the wind turbine.During this study, the influence of the climatic conditions of Borj Cédria site (insulation, ambient temperature) as well as the chimney height and the collector diameter on the amount of electricity production were investigated.The distribution and the evolution of the temperature at different positions of the prototype as well as the electrical energy produced were determined.The results reveal that when the temperatures reach 45 °C, the electric power reaches an average value of about 0.3 W/m2 for a solar tower prototype with 8 m of diameter and 2 m of height chimney.

Experimental study on an indoor scale solar chimney setup in an artificial environment simulation laboratory

An artificial environment simulation laboratory (AESL) was built and successfully applied to the experimental study of a solar chimney setup for the first time. A solar simulator and a temperature control system are included in the laboratory to achieve active control of environmental parameters. An indoor scale solar chimney setup with a collector diameter of 1.22m and chimney height of 1m was constructed in the testing area of the AESL. The airflow temperature and updraft velocity were measured for the solar chimney setup with varying radiation intensities and chimney heights. The measured data were used to validate a thermal model for the collector. The thermal characteristics of the solar collector were investigated through the temperature field in the collector. The upper limitations on the collector radius and chimney height were discussed based on experimental results. The experimental work on the basic solar chimney setup performance helped in understanding the thermodynamic characteristics of the solar chimney power plant (SCPP), thereby serving as the basis for the design of large-scale commercial SCPPs.

Morphology Studies of Electrospun Lithium Iron Phosphate (LiFePO<sub>4</sub>)/Cellulose Acetate (CA) Fibers

This work was carried out as a preliminary study of electrospun LiFePO4/CA fibers. Cellulose acetate (CA) and LiFePO4 solutions were prepared separately using mixed solvent of acetone and water, prior to the electrospinning process. Then, electrospinning parameters including solution concentration, distance tip to collector, pump rate, and needle diameter size were optimized. Brunauer Emmett Teller (BET) was used to determine the surface area of CA fibers. Viscosity of CA solution was obtained by viscometer. LiFePO4/CA fibers were stabilized and carbonized at different temperature. The surface morphology and microstructure of the obtained LiFePO4/ CA fibers were then characterized using scanning electron microscope (SEM). In this work, it is shown that different electrospinning parameter, solution concentration and solution viscosity gives different fibers diameter and distribution. Moreover, the stabilization and carbonization temperature of LiFePO4/CA fibers may also affect the fibers microstructure.

An experimental study on the thermal performance of a solar chimney with different dimensional parameters

For optimizing solar chimney power plant (SCPP) and also reaching to new experimental data, a pilot setup consisting of a chimney with 3 m height and 3 m collector diameter was constructed. Two main effective parameters including absorber material and geometric dimensions were analyzed using thermal and velocity data. In this paper, the main purpose is obtaining new experimental data in these new dimensions. The obtained data will be utilized in our future after studies for achieving a structural dimensional formulation of SCPPs. In fact, there is no comprehensive formula for achieving a precise relationship between the geometric parameters of the SCPPs. The dimension analyses show that the collector entrance distance of 6 cm has the best performance and the corresponding amounts of the chimney diameter and the chimney height are 10 cm and 3 m, respectively. Also, aluminum absorber has more heat transfer rate than iron one and the maximum fluid temperature difference between the collector and the ambient is 27 °C. The maximum air velocity of 1.7 m/s was recorded inside the chimney. In comparison to the chimney with 2 m height, this was about 55.3% higher.

Melt electrospinning onto cylinders: effects of rotational velocity and collector diameter on morphology of tubular structures

Melt electrospinning writing is a direct-writing additive manufacturing process that involves depositing a continuous, viscous and electrohydrodynamically stabilised molten jet onto a collector. Here, molten threads of medical-grade polycaprolactone (PCL) are directed towards stationary/rotating cylindrical collectors (0–6600 rpm), including very slow revolutions well below the critical translation speed (approximately 600 mm min−1) of the molten jet. In this slow-rotation region, the speed of the jet is faster than the movement of the collector and buckled/coiled fibres are produced due to compressive viscoelastic forces. The results are porous PCL tubes with wall morphologies often associated with viscoelastic liquids impinging onto a surface. The curvature of the collector affects how the fibre is deposited, with preferential fibre deposition along the axis of the cylinder. When the collector rotation speed is increased to greater than the speed of the jet, then straight fibres are produced. Such tubular structures have applications in tissue engineering. © 2015 Society of Chemical Industry

Numerical simulation of flow and heat transfer characteristics in Solar Enhanced Natural Draft Dry Cooling Tower

A Solar Enhanced Natural Draft Dry Cooling Tower (SENDDCT) is a Natural Draft Dry Cooling Tower that uses solar energy to enhance the cooling performance and lower the operating cost for a power plant. In this paper, a three-dimensional numerical stimulation is developed by using FLUENT to investigate the effects of the following operating parameters on the thermal performance of the SENDDCT: the collector diameter, ambient temperature and the types of heat exchanger layout. The numerical simulation results reveal that the heat transfer rate is proportional to collector diameter, but is inversely proportional to the ambient temperature. Specifically, decreasing the ambient temperature from 305.15 K to 283.15 K has result in an increase of almost 104.2 MW in heat transfer rate. For a fixed heat exchanger area, the heat rejection of the SENDDCT decreases with an increasing coverage ratio for a given “unit coverage ratio” defined in this paper. It is found that stronger vortices are generated at the back of heat exchangers due to the introduction of the blockage units. Using smaller heat exchanger and blockage units can weaken vortices and enhance cooling performance.

A Modified Electro-Centrifugal Spinning Method to Enhance the Production Rate of Highly Aligned Nanofiber

In this paper, for the aim of increasing the production rate of highly aligned nanofibers, electrocentrifuge spinning (ECS) technique was modified by equipping it with two nozzles as the spinneret. This new setup obviously doubles the production rate of nanofibers relative to the conventional ECS. To investigate the effect of this modification on the degree of nanofibers alignment (DeNA), the values of DeNA were measured for 30 distinctive experiments and the results were compared with that of ECS setup with a single nozzle. The originality of this work has lain in the fact that for these 30 experiments, which were designed by Design Expert Software (DES), the DeNA of the new ECS was the same as the conventional setup. Additionally, a spinneret with four nozzles was employed to evaluate the influence of number of nozzles on the DeNA. Lastly, the optimum values of voltage, polymer concentration, spinneret rotational speed and collector diameter were determined in order to maximize the DeNA of the modified ECS setup.

The theory of parallel channels manifolds (ladder networks) revisited part 2: Design for uniform cross‐flow distribution

This article, the second of a series, is devoted to the design of U‐type ladder manifolds capable of exhibiting a close‐to‐uniform distribution of the flow between all the cross‐channels. This article builds on the analytical and numerical results of the previous part but brings the geometric properties of the network in the foreground. Two situations are considered: the first being with constant channel diameters for which the diameter ratios of distributor and collector are sought which minimize the dispersion of the cross‐flow distribution. The second situation considers tapering the distributor or collector diameter along their lengths, and the optimal tapering is sought.

Minimum Collection Efficiency Diameter during Snow Scavenging Process

The scavenging of atmospheric aerosols by below-cloud scavenging processes during rain or snow precipitation plays an important role in the removal of aerosols in the atmosphere. Because of a variety of frozen precipitation types and their physical properties, the snow scavenging is a more complicated process compared with the rain scavenging. This study determined the minimum collection efficiency and minimum collection efficiency diameter for polydispersed hydrometeor size distributions during the snow precipitation. Three types of collectors (graupel, dendrite, and column) were considered and the obtained minimum collection efficiency and the corresponding minimum collection efficiency diameter were intercompared. Results showed that the minimum collection efficiency diameters for snow were smaller than those for rain. The minimum collection efficiency diameters of graupel decreased as the collector diameter increased, whereas other collectors (i.e., dendrite and column) did not show this decreasing tendency. The minimum collection efficiencies of graupels were larger than those of dendrite and column collectors. It was also shown that column collectors had the largest scavenging coefficients.

The influences of collector diameter, spinneret rotational speed, voltage, and polymer concentration on the degree of nanofibers alignment generated by electrocentrifugal spinning method : Modeling and optimization by response surface methodology

We studied the capability of electrocentrifuge-spinning (ECS) method for generating highly aligned nanofiber. First, the degree of nanofiber alignment (DNA) produced by ECS was compared with that of rotating drum (RD) method and ECS superiority was demonstrated. Then central composite design (CCD) and response surface methodology (RSM) was used for optimization of operating conditions. The critical factors selected for the examination were voltage, polymer concentration, collector diameter and spinneret rotational speed. To design the required experiments at the settings of independent parameters, RSM was applied. A total of 30 experiments were accomplished towards the construction of a quadratic model for target variable. Using this quadratic model, the influence of aforementioned variables was discussed on DNA. The best operating condition for attaining the maximum value of DNA was the applied voltage of 20.19 kV, polymer concentration of 17.44wt%, collector diameter of 40.76 cm, and rotational speed of 2680.10 rpm.

Optimization of the Hose-Based Low-Cost Solar Collector

The performance of solar collectors based on plastic hoses is noticeably improved by using a thermal-hydraulic modeling experimentally validated. This model allows us to optimize the main parameters of collector (length and diameter of hoses, tilt angle and number of glazing covers) for different climatic conditions. This way, was proposed an innovative design that could works well in temperate locations and that costs fifty dollars for a single family selfconstruction unit.