Collector Concentration Research Articles

Control strategy and thermal inertia influence on evacuated tube solar water heating systems

The main objective of this article is to investigate the effect of a control scheme on the behavior of a solar domestic hot water system, consisting of two evacuated tubes with compound-parabolic concentrator (CPC) collectors and a storage tank. In this regard, a transient thermal analysis of the system was performed using an original mathematical model. The developed model was validated by comparing the results with the data provided by the manufacturer. Simulations were conducted during a 48-h period in the meteorological conditions of Bucharest, Romania (latitude 44°24′N, longitude 26°05′E). The second objective of the present work relates to the working fluid thermal inertia. An analysis was made to determine whether the solar collectors’ fluid thermal inertia has an impact on the storage tank water temperature. Three different working fluids have been considered. The results showed that for the entire 2-day period in which simulations have been conducted, differences between the useful energy delivered to the storage tank water in the case with mass flow rate adjusted depending on the incident solar radiation and the cases with constant mass flow rate were approximately 1 kWh in summer and 0.72 kWh in winter. In addition, it has been concluded that the time required to heat the storage tank water from 30 to 60 degrees centigrade is approximately an hour less when the system is working with water compared to the propylene glycol case.

Enhancement in energy metrics of double slope solar still by incorporating N identical PVT collectors

In this paper, double slope solar still has been analyzed by incorporating N identical partially covered photovoltaic thermal (PVT) collectors under optimized condition to assess the enhancement in energy metrics. Number of collectors, mass flow rate and water depth of N identical partially covered PVT flat plate collector (N-PVT-FPC-DS) have been optimized for climatic condition of New Delhi. Subsequently, annual distillate output, energy, exergy, energy metrics, cogeneration efficiency and cost of distillate output have been computed for the proposed N-PVT-FPC-DS at 0.14m water depth. Results obtained have been compared with results reported by previous researchers and it has been concluded that the proposed N-PVT-FPC-DS performs better than double slope solar still incorporated with N identical PVT compound parabolic concentrator collectors (N-PVT-CPC-DS) and conventional double slope solar still (CDSSS) on the basis of energy metrics and cost of distillate output. The exergy based energy payback time is lower by 74.66% and 62.62%; energy production factor is higher by 43.30% and 38.14%; life cycle conversion efficiency is higher by 48.57% and 48.57% and cost of distillate output is lower by 35.37% and 4.88% for the proposed N-PVT-FPC-DS than N-PVT-CPC-DS and CDSSS respectively.

Exergoeconomic, enviroeconomic and productivity analyses of basin type solar stills by incorporating N identical PVT compound parabolic concentrator collectors: A comparative study

This paper presents exergoeconomic, enviroeconomic and productivity analyses of basin type solar stills by incorporating N identical photovoltaic thermal (PVT) compound parabolic concentrator (CPC) collectors commonly known as PVT-CPC active solar distillation systems. In this work, the mass flow rate and the number of collectors have been optimized and values of yearly distillate output, energy, exergy and cogeneration efficiency have been computed for the proposed solar distillation systems at 0.14m water depth for the same basin area under composite climatic conditions of New Delhi. The exergoeconomic parameter, enviroeconomic parameter, productivity and cogeneration efficiency for double slope PVT-CPC active solar distillation system have been found to be higher by 16.22%, 21.48%, 8.56% and 5.73% respectively than obtained from a similar single slope set up at a water depth of 0.14m for the same basin area under similar climatic condition. The proposed system can meet the potable water needs on a commercial scale and generate DC electrical power during sunshine hours.

Sulfur reduction in Sangan iron ore by flotation

in this study the flotation of pyrite as the main sulfide impurity of Sangan iron ore in Iran, was investigated. For this purpose the effect of collector type, pH, collector concentration and stage dosing on reverse flotation of iron sulfide ore from magnetite ore was investigated. Two type of thiol collectors include xanthates (sodium isopropyl xanthate (SIPX) and potassium amyl xanthate (PAX)) and dithiocarbamate (di-ethyl dithiocarbamate (DTC)) and the mixture of collectors was studied. The highest sulfur removal was obtained with potassium amyl xanthate. Stage dosing had a significant effect in sulfide flotation and the best recovery was obtained when the collector was added in 4 stages. The acidity had a positive effect on sulfide floatability and the best result was obtained at pH 3.5-4. Investigation about collector concentration showed that increasing the SIPX concentration enhanced the sulfur removal but this factor was not effective for PAX.

The Effect of Flotation Reagents Addition (MIBC and PAX) on the Relative Permittivity Value Using 2-Electrode Capacitance Sensor

In general, frother and collector are used as reagents to obtain an optimum condition in flotation processes. In this study, the effect of methyl isobutyl carbinol (MIBC) frother and potassium amyl xanthate (PAX) collector on the relative permittivity value using 2-electrode capacitance sensor was conducted. The objective of this study is to know the relative permittivity value of the material affected by MIBC and PAX additions. Permittivity obtained from this study would be used as basic data which is used to analyze the metallurgical performance of flotation process based on the 3-dimensional images (permittivity distribution) using electrical capacitance volume tomography (ECVT) in the further researches. Signal generator, oscilloscope, and 2-electorde capacitance sensor (electrode dimension of 40 x 40 mm) were used to measure the relative permittivity of sample which the samples were measured by using a frequency of 2.5 MHz at room temperature. Frother and collector concentration used in this study were 0.006; 0.085; 0.113; 0.169; and 0.226 Molar of MIBC, and 0.004; 0.007; 0.011; and 0.015 Molar of PAX, respectively. Based on this study, it can be concluded that the relative permittivity value decreases with increasing of MIBC frother and increases with increasing of PAX collector. Minimum and maximum relative permittivity values obtained in this study were 9.70 and 9.72for the frother addition, and 11.12 and 11.17 for the collector addition.

Sulfur reduction in Sangan iron ore by flotation

in this study the flotation of pyrite as the main sulfide impurity of Sangan iron ore in Iran, was investigated. For this purpose the effect of collector type, pH, collector concentration and stage dosing on reverse flotation of iron sulfide ore from magnetite ore was investigated. Two type of thiol collectors include xanthates (sodium isopropyl xanthate (SIPX) and potassium amyl xanthate (PAX)) and dithiocarbamate (di-ethyl dithiocarbamate (DTC)) and the mixture of collectors was studied. The highest sulfur removal was obtained with potassium amyl xanthate. Stage dosing had a significant effect in sulfide flotation and the best recovery was obtained when the collector was added in 4 stages. The acidity had a positive effect on sulfide floatability and the best result was obtained at pH 3.5-4. Investigation about collector concentration showed that increasing the SIPX concentration enhanced the sulfur removal but this factor was not effective for PAX.

Exergoeconomic and enviroeconomic analyses of N identical photovoltaic thermal integrated double slope solar still

This paper deals with the enhancement in exergoeconomic and enviroeconomic parameters for double slope solar still by incorporating N identical partially covered photovoltaic thermal (PVT) collectors. The energy, exergy, exergoeconomic and enviroeconomic parameters and productivity have been computed for double slope solar still incorporated with N identical PVT flat plate collectors (N-PVT-FPC-DS). The analysis has been done at 0.14 m water depth, optimum values of mass flow rate and a number of collectors considering four climatic conditions of New Delhi for each month of the year. The result obtained for the proposed system has been compared with the result of earlier researchers. It has been concluded that kWh per unit cost based on exergy gain is higher by 40.73% and 54.63%; environmental cost is higher by 59.70% and 92.55%; however, the output per unit input based on productivity is higher by 9.25% and lower by 25.13% for N-PVT-FPC-DS than double slope solar still integrated with N identical PVT compound parabolic concentrator collector and conventional double slope solar still, respectively.

Performance analysis of basin type solar stills integrated with N identical photovoltaic thermal (PVT) compound parabolic concentrator (CPC) collectors: A comparative study

In the present study, performance analysis of basin type solar stills integrated with N identical partially covered photovoltaic thermal (PVT) compound parabolic concentrator (CPC) water collectors known as PVT-CPC active solar distillation systems have been carried out by incorporating the effect of water depth. Two Indian climatic conditions namely January (winter) and June (summer) have been considered for numerical computation. The average daily thermal, exergy, electrical, overall exergy, overall thermal efficiencies and average daily productivity have been evaluated for optimum number of collectors and mass flow rate and the results obtained have been compared. It has been concluded that single slope performs better than double slope PVT-CPC active solar still on the basis of average daily thermal efficiency, overall thermal efficiency and productivity if depth of water in the basin is more than 0.31m and vice versa.

Lauryl phosphate adsorption in the flotation of Bastnaesite, (Ce,La)FCO3

Wetting characteristics and micro-flotation responses of bastnaesite were examined as a function of pH and at different levels of lauryl phosphate adsorption. Theoretical computations for the bastnaesite-lauryl phosphate system were calculated using the universal force field (UFF) and semiempirical quantum chemical methods. The interaction energy and frontier orbital results correlate remarkably well with the experimental contact angle and micro-flotation test results. The wetting characteristics of bastnaesite with adsorbed collector were examined using both contact angle measurements and molecular dynamics simulations (MDS). The adsorption isotherm at low levels of lauryl phosphate adsorption was established. Finally, the relationship between hydrophobicity and adsorption density was examined by MDS, and compared to the results with octyl hydroxamate at low collector concentrations.

Energetic and exergetic analysis of N partially covered photovoltaic thermal-compound parabolic concentrator (PVT-CPC) collectors connected in series

This research undertook, a comparative study between the energy and exergy performance by considering four systems or cases namely: partially covered [case (i): N photovoltaic thermal - compound parabolic concentrators (PVT-CPC), case (ii): N photovoltaic thermal (PVT) collectors, case (iii): N compound parabolic concentrators (CPC) and case (iv): N flat plate collectors (FPC)] connected in series. A comparison in performance was carried out by considering the thermal performance of two fluids; water and molten salt. It was observed that N-PVT-CPC collectors (25% PV) and conventional CPC collectors are the most suitable of the investigated configurations for steam cooking using molten salt as the fluid. It was found that, the maximum net annual overall thermal energy and exergy were 1367.86kWh and 150.45kWh for the N-CPC collector [case (iii)], which was higher than for N PVT-CPC fluid collectors [case (i) (a)] by 1.6 and 1.06 times, respectively.

Evaluation of cupferron on the selective separation of gallium from aluminum by flotation: The separation mechanism

Aluminum is an impure element in acidic solutions obtained from gallium sources. Therefore, the selective separation of gallium from aluminum, using cupferron as a ligand (chelating agent) and sodium dodecyl sulfate as an anionic collector was investigated by flotation. The effect of the solution pH, the molar ratio of cupferron to gallium, the collector concentration, the impeller speed, the conditioning time and the flotation time on the selective separation of Ga(III) from Al(III) were studied. The results indicate that the chelating agent cupferron, efficiently separated gallium from aluminum, owing to the higher chelating strength of the interaction between Ga(III) and cupferron. The Ga(III)-cupferron complexes, formed in the presence and absence of SDS, were spectroscopically confirmed and characterized by Fourier transform infrared (FTIR), UV–visible spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDX). The bonding of cupferron with Ga(III) was considered to be as a bidentate ligand, and gallium formed 1:1.5 complexes with cupferron in aqueous solution. The separation mechanism of flotation was proposed owing to the formation of a physical interaction between the Ga(III)-cupferron complex and SDS.

Interplay of Particle Shape and Surface Roughness to Reach Maximum Flotation Efficiencies Depending on Collector Concentration

ABSTRACTParticle–particle and bubble–particle-interactions in flotation systems are governed by physico-chemical and hydrodynamic conditions of pulp. Shape factor and roughness of particles significantly affect these interactions, and hence both grade and recovery in flotation. Although many studies have been conducted to understand morphological features of particles, the underlying mechanism of their effect on flotation recovery have not been clearly shown. Towards this aim, acombination of grinding and abrasion processes was applied to mimic grinding in terms of shape and roughness in order to get their corresponding flotation recoveries at different collector levels. For this purpose, glass beads representing smooth spherical particles of –150+106 µm in size along with ground and abraded glass particles of different shapes and roughness were used to evaluate the flotation efficiency of these particles in the absence and presence of amine collector. The dependence of the shape and roughness on the flotation recoveries at different hydrophobicities as monitored by different amine collector concentrations is demonstrated. Finally, the results are discussed to see if morphology ofparticles can be tuned through grinding to achieve maximum flotation efficiencies.

Step tracking program for concentrator solar collectors

The increasing living standards in developed countries lead to increased energy consumption. The fossil fuel consumption and greenhouse gas effect that accompany the energy production can be reduced by using renewable energy. For instance, the solar thermal systems can be used in temperate climates to provide heating during the transient period or cooling during the warmer months. Most used solar thermal systems contain flat plate solar collectors. In order to provide the necessary energy for the house cooling system, the cooling machine uses a working fluid with a high temperature, which can be supplied by dish concentrator collectors. These collectors are continuously rotated towards sun by biaxial tracking systems, process that increases the consumed power. An algorithm for a step tracking program to be used in the orientation of parabolic dish concentrator collectors is proposed in the paper to reduce the consumed power due to actuation. The algorithm is exemplified on a case study: a dish concentrator collector to be implemented in Brasov, Romania, a location with the turbidity factor TR equal to 3. The size of the system is imposed by the environment, the diameter of the dish reflector being of 3 meters. By applying the proposed algorithm, 60 sub-programs are obtained for the step orientation of the parabolic dish collector over the year. Based on the results of the numerical simulations for the step orientation, the efficiency of the direct solar radiation capture on the receptor is up to 99%, while the energy consumption is reduced by almost 80% compared to the continuous actuation of the concentrator solar collector.

Effect of energy matrices on life cycle cost analysis of partially covered photovoltaic compound parabolic concentrator collector active solar distillation system

This paper presents the life cycle cost analysis of partially covered photovoltaic thermal (PVT) compound parabolic concentrator (CPC) collector integrated solar distillation system known as PVT-CPC active solar distillation system by incorporating the effect of energy payback period. The thermal model of the system has been developed. The number of PVT-CPC collectors and mass flow rate has been optimized. The annual yield, EPF and LCCE have been found to be higher by 5%, 12.73% and 22.22% respectively for double slope than single slope PVT-CPC active solar distillation system at 0.14m depth of water. However, production cost of water at 5% rate of interest and EPBT have been found to be lower by 10.09% and 17.98% respectively for double slope PVT-CPC active solar distillation system. It is inferred that double slope performs better than single slope PVT-CPC active solar distillation system based on annual yield if depth of water is less than 0.19m and vice-versa. The proposed system is self sustainable and it can meet the daily requirement of potable water on commercial level as well as DC electrical power during sunshine hours.

On the detachment of hydrophobic particles from the froth phase

We conducted an experimental study to investigate the behaviour of hydrophobic particles in the froth phase of a laboratory column. A stable froth was formed by passing the air through a porous disk into the liquid containing frother. Individual bubbles were loaded with hydrophobic particles separately in a fluidised bed and allowed to rise into the froth layer. Particles dislodged from the froth were collected and measured. The effect of collector concentration and superficial gas velocity on the detachment of particles from the froth was studied. The results showed that fraction of particles detaching from the froth decreases exponentially with increase in the collector concentration and increases slightly with superficial gas velocity. In general, low froth dropback values were obtained for the conditions studied in the present system which are considerably lower than the previously reported values.

Flotation of quartz using ionic liquid collectors with different functional groups and varying chain lengths

The application of imidazolium, ammonium, and pyridinium based ionic liquids (ILs) as the flotation collectors of quartz has been investigated. The flotation studies have been carried out for pure quartz, quartz-hematite synthetic mixture and a low grade banded hematite quartzite (BHQ) ore while the trend of floatabilities has been explained in terms of the structural differences of the ILs. The flotation of pure quartz using the ammonium and pyridinium based IL collectors has exhibited an excellent performance; where about 100% quartz could be floated at a collector concentration of 5∗10−5M. The results are found better compared to the imidazolium ILs and conventional quartz collectors like dodecylamine (DDA) and cetyl trimethyl ammonium bromide (CTAB). The ammonium and pyridinium based collectors also show better iron grade and recovery compared to the imidazolium collectors during the reverse flotation of the synthetic hematite-quartz mixture and BHQ ore. Using these collectors, an iron ore concentrate of ∼62% Fe at ∼75% recovery could be obtained from the BHQ ore containing ∼38% Fe. In the Fourier Transform Infra Red spectroscopy (FTIR), the peak intensity at 2900cm−1 due to the presence of alkyl groups signifies the extent of adsorption of the collectors on quartz. The N/Si ratio and CC peak area as determined by the X-ray photoelectron spectroscopy (XPS) results show the relative adsorption of the IL collectors. The pyridinium based IL collector show better adsorption strength compared to all others ILs under study. The better flotation results in the case of the ammonium and pyridinium collector are attributed to the presence of higher alkyl chain length inducing better hydrophobicity.

Effect of pH on surface characteristics and flotation of sulfidized cerussite

The effect of pH on surface characteristic and flotation of sulfidized cerussite was studied by micro-flotation tests, dissolution experiments, scanning electron microscopy (SEM) energy dispersive spectrometer (EDS), and X-ray photoelectron spectroscopy (XPS). The micro-flotation tests demonstrated that higher recovery of cerussite was achieved in acidic solutions than that in alkaline solutions. Despite the addition of high collector concentrations, cerussite flotation did not improved in alkaline solutions. The dissolution performance of sulfide-treated cerussite at different pH values indicated that the lead sulfide layer on the surface of sulfide-treated cerussite could exist in acidic solutions and it was more stable at acidic pH than in alkaline solutions. This finding was proved by the SEM-EDS and XPS analyses.

Design, construction and performance test of an efficient large-scale solar simulator for investigation of solar thermal collectors

The performance of a thermal collector can be evaluated by determination of thermal efficiency in steady state test of solar simulators. This paper presents design and construction of an efficient multiple-lamp solar simulator for investigating the performance of the solar collectors for scientific and industrial purposes. Metal halid lamps are employed as source of irradiance. The uniformity of the irradiated surface was checked by simulation of the light field. This simulations are done in DIALux. The non-uniformity and instability, as factors that are described in EN 12975 standard, must be less than 15%. Also, the standard is determined, at least, 700W/m2 as average of irradiance for testing solar collectors. The amount of irradiance received by their radiated surface, which can vary from 100W/m2 to 1000W/m2, is controlled by changing the distance of testing surface from lamps and/or the number of lamps that is on. The performance of solar simulator was compared to Sun by testing a Compound Parabolic Concentrating (CPC) collector at Materials and Energy Research Center (MERC) in the city of Karaj. In the same conditions of test, the thermal efficiency of CPC collector was calculated with both sources of radiation from the solar simulator and Sun.

Electrospun silk-based nanofibrous scaffolds: fiber diameter and oxygen transfer.

In this study, silk fibroin was extracted from cocoons of silkworms and fabricated into nonwoven mats by electrospinning method. A new model based on the group method of data handling (GMDH) and artificial neural network (ANN) was developed for estimation of the average diameter of electrospun silk fibroin nanofibers. In this regard, concentration, flow rate, voltage, distance, and speed of collector were used as input parameters and average diameter of the fibers was considered as output parameter. Two models were capable to estimate average diameter of fibers with good accuracy. The average absolute relative deviation for GMDH and ANN models was equal to 3.56 and 2.28 %, respectively. Furthermore, due to importance of oxygen delivery to site of injury to promote wound healing, continuity equation for mass transport was employed for prediction of oxygen profile in the system containing wound dressing and skin. The result showed that our prepared wound dressing is capable to pass the oxygen completely to the skin layer and is not acting as a barrier for oxygen delivery to wound site. Since average nanofibers diameter can influence the mat physical, mechanical and biological properties then this model may serve as a useful guide to obtain tailor made and uniform silk nanofibers at various combinations of process variables.

Heat Transient in the Circular Finned Cylindrical pipe with the Application of an Off-feed Axis Solar Concentrating Collector

Heat Transient in the Circular Finned Cylindrical pipe with the Application of an Off-feed Axis Solar Concentrating Collector