Parabolic Concentration Research Articles

Exact analysis of hydromagnetic non‐Gray optically thick heat absorbing fluid with nonlinear parabolic ramped conditions

AbstractThe article presents a solution to a complex problem involving a transient MHD‐free convective chemically reactive flow. The flow involves a viscous incompressible electrically conducting non‐Gray optically thick fluid moving past a semi‐infinite vertical plate that has suddenly started but is temporarily accelerated. The plate has nonlinear parabolic ramped conditions, and the flow is exposed to thermal radiation, heat absorbing sink, and diffusion‐thermo effect. For the current study, the model fluid being used is moist air. The governing equations are obtained using the Laplace transform technique with the help of the Heaviside step function. This study is the first to consider parabolic ramped motion, temperature and concentration simultaneously. Effects of the pertinent parameters on the Sherwood number and Nusselt number are visualized using 3D surface plotting. Findings of the problem manifest that concentration, temperature, and velocity profiles in case of ramped conditions are less than in isothermal conditions. The rate of heat transfer of mercury is less than oxygen, air, water, and ethanol at a room temperature of 22°C–25°C. The ramped plate has the tendency to augment the heat transfer rate. The present study is of great interest in numerous fields of industry and machine‐building applications.

Study of an unsteady magnetohydrodynamic‐free convective flow under parabolic ramped temperature and concentration in the presence of Soret and heat sink

AbstractThe purpose of this paper is to investigate the effects of Soret, thermal radiation, and chemical reaction on an unsteady magnetohydrodynamic free convective flow past an impulsively initiated semi‐infinite vertical plate with heat sink under parabolic ramped temperature and parabolic ramped concentration. Using some nondimensional parameters, the flow boundary equations in this case are first converted to dimensionless equations. The closed‐form Laplace transform technique is employed here to solve the partial differential equations and get the solutions for fluid velocity, temperature, and concentration. The velocity, temperature, and concentration of the fluid tend to vary with the effect of various flow factors. These changes are graphically represented and analyzed. Differences in skin friction, Nusselt number, and Sherwood number for the different relevant parameters are also recorded. The Soret number hikes the fluid velocity and concentration. The rate of heat transfer, mass transfer, and momentum transfer improves due to the application of parabolic ramped conditions.

Methodology for obtaining instantaneous thermal performance curves for a parabolic trough solar by experimental data and projections based on a ray tracing model

Parabolic Trough Concentration (PTC) systems represent the best alternative for implementing solar energy in different sectors due to their reachable temperatures and maturity levels. However, there is a notably lack of normativity for evaluating the experimental thermal performance curves of these systems. For this reason, a new methodology is proposed to solve problems arising in the thermal characterization of them. This methodology allows to evaluate the system at any time of year without a two-axis tracking system, using experimental data and projections based on a ray tracing model. To validate the methodology, a PTC system was evaluated during solstices and equinoxes. Variations in experimental thermal performance response along the year caused by solar declination; were observed, reaching a maximum loss of 45% of received power and 22% in efficiency for the lowest solar altitude conditions. The ray tracing model methodology was applied to the experimental thermal performance curves obtained along the year to get the best efficiency curve. The good approximation of the projections made with this methodology helped us to consider it validated. With this method, it is also possible to easily obtain a family of curves describing the power and performance of the system throughout the year and wherever it is installed.

Theoretical study of a mathematical approach of a modeling of the solar collector with a parabolic cylindrical type concentration effect

Theoretical study of a mathematical approach of a modeling of the solar collector with a parabolic cylindrical type concentration effect

Fabrication of Parabolic-trough concentration for solar water heating

This paper presents the design fabrication Parabolic-trough solar water heating is a well-proven technology that directly substitutes renewable energy for conventional energy in water heating. In Two meters parabolic solar concentration has been fabricated to produce boiled water up to 100oC for the purpose of central heating services. The concentration is toward the sun light during the day time; by using a control circuit, The amount of the portable water was much dependent on the accurate focusing of the system which increases according to preheating. This system could therefore be used for heating water at home via increasing the temperature in hot tank by covering the hot water and isolating the tank from the surroundings.

Geometric analysis and optimization of a parabolic concentrator for production at both thermal receivers at its focal point

The exploitation of solar energy for the production of electricity through a thermodynamic cycle is done according to several methods. The parabolic concentration method remains the best because of its high thermal efficiency (about 68%) but the least used because of difficulties related to the storage of its energy. Our work concerns a parabolic reflector with two receivers at its focal point. These two receivers are a boiler and a Stirling engine. The boiler and the Stirling engine receive the energy concentrated by the reflector. In the presence of the Sun it is the Stirling engine that produces the electricity. During the periods when the solar energy is insufficient or absent it is the thermal tank that will send the heat to the fluid that will turn the blades of a turbine to produce electricity. To meet the thermal needs of these two receivers, the efficiency of the reflector's heat production must be improved. To this end, we have studied the possibilities of optimizing the geometric parameters of the parabolic concentrator. For a surface of 12.56 m2 of the reflector, the use of standard geometric parameters allowed us to obtain a daily energy of 824.474 kWh when the solar power is 1104.938 kWh. For the same surface, using the optimized parameters, the production increased to 975.937kWh; a gain of 13.7%. This study allowed us to discover that the geometric and optical parameters strongly influence the thermal production of a reflector.

Stochastic elliptic–parabolic system arising in porous media

We prove the existence of a pathwise weak solution to the single-phase, miscible displacement of one incompressible fluid by another in a porous medium with random forcing. Our system is described by a parabolic concentration equation driven by an additive noise coupled with an elliptic pressure equation. We use a pathwise argument combined with Schauder’s fixed point theorem.

Performance Analysis of Compound Parabolic Concentration Photothermal and Photoelectricity Device for Soil Heating in Facility Agriculture

It is difficult for solanum crops to grow continuously during winter in severe cold regions. Thus, a soil heating system for facility agriculture based on solar concentration technology was proposed, and a novel compound parabolic concentration photothermal and photoelectricity device (CTPV) equipped in the system was designed to address this problem. In accordance with the structure of the device, LightTools optical software was selected to analyze the variation trend of the light escape rate of the device with the different incident angles. On the basis of the calculation results, an experimental test system was used to investigate the relationship of the air temperature of the inlet and the outlet, total output power of the solar cells, and photothermal and photoelectricity efficiency of the device with the operation time during a sunny day. Research results reveal that the light escape rate of the device is 5.36% at an incidence angle of 12°. At a velocity of 1.5 m/s, the maximum air temperature of the outlet can reach 55.6 °C, and the total output power of the solar cells is 474.4 W. The variation of the total power of the solar cells is consistent with the simulation results. The maximum instantaneous heat collection and the maximum photothermal and photoelectricity efficiency of the device are 306 W and 60.4%, respectively, and the average efficiency is 44.9%. This study can serve as a reference for compound parabolic concentration technology applied for soil heating in facility agricultural soil heating systems.

Design and development of a low‐cost solar parabolic dish concentrator system with manual dual‐axis tracking

SummarySolar parabolic dish attracts most of the researchers with its higher concentration ratio and its modular ability. Parabolic dish concentration can be employed in many applications which falls under solar thermal and solar electricity production. This article presents a novel approach of designing and development of a low‐cost solar parabolic dish concentrator of 12.6 m2 aperture area with dual‐axis manual tracking, which can be utilized for process heating and electrical power generation simultaneously. The same set up has been fabricated in National Institute of Technology, Puducherry and ready for investigation and analysis on different prospective. The design concept of solar parabolic dish concentrator and dual‐axis tracking system and its economic analysis are elaborately discussed in this article. The complete procedure followed for the fabrication of the entire system is also highlighted. Based on the economic analysis it was found to be more economical than the other existing dish concentrators in the literature, which costs ₹6877.00 per square meter.

Solar thermal and electricity. A state of the art

The objective of this contribution is to provide a state-of-the-art on research in solar thermal electricity systems. This objective is achieved using Scopus, and the softwears “Publish or Perish” and “VOSviewer”. The results of the research show the behavior of scientific productivity in this area. As well as the most productive thematic areas. Nations that lead the research in the generation of electric power on a large scale, using solar thermal energy. Network of scientific collaboration among nations, referring to the research of electricity generation through solar thermal energy. Correlation network among the most productive authors, in this subject within the Scopus directory. Most cited articles by each of the main journals that disseminate this theme. Conceptual bases of the generation of electricity with solar thermal energy. Properties of thermal energy storage technologies (TES) in power plants with parabolic solar concentrators or solar concentration towers. Current technologies and trends. Technological trends. Trends in the global energy market.

Design, modeling, and optimization of a dual reflector parabolic trough concentration system

Design, modeling, and optimization of a dual reflector parabolic trough concentration system

Highly efficient side-pumped solar laser with enhanced tracking-error compensation capacity

We report here a significant numerical improvement in side-pumped solar laser collection efficiency and solar-to-laser conversion efficiency, with an enhanced tracking error compensation capacity. Two side-pumped configurations, a single-rod and a dual-rod scheme were studied. The former pumped a thick laser rod with the full collection area of a parabolic mirror and the latter pumped two thin laser rods simultaneously, each rod being pumped by half of the collection area of the same concentrator. Both configurations were composed of a fused silica aspheric lens and a 2D-shaped-semicylindrical pump cavity, within which the Nd:YAG rods were mounted, allowing a tight focusing of the concentrated solar pump power from the focal spot of the heliostat–parabolic mirror solar energy collection and concentration system and an efficient pumping to the laser crystals. 42.70 W continuous-wave multimode solar laser power, corresponding to 27.37 W/m2 collection efficiency, and 3.26% solar-to-laser power conversion efficiency were numerically calculated for the single-rod scheme, being 1.55 and 1.34 times, respectively, higher than the previous state-of-the-art experimental records of side-pumped solar laser. For the dual-rod scheme, 37.72 W multimode solar laser power, corresponding to 24.18 W/m2 collection efficiency, and 2.88% solar-to-laser power conversion efficiency were numerically obtained, being 1.37 and 1.19 times, respectively, more than the previous record in side-pumping configurations. More importantly, largely enhanced brightness figure of merit, thermal performance and tracking error compensation capacity were attained by the dual-rod scheme, as compared to that of the single-rod scheme.

Flattening of Diluted Species Profile via Passive Geometry in a Microfluidic Device.

In recent years, microfluidic devices have become an important tool for use in lab-on-a-chip processes, including drug screening and delivery, bio-chemical reactions, sample preparation and analysis, chemotaxis, and separations. In many such processes, a flat cross-sectional concentration profile with uniform flow velocity across the channel is desired to achieve controlled and precise solute transport. This is often accommodated by the use of electroosmotic flow, however, it is not an ideal for many applications, particularly biomicrofluidics. Meanwhile, pressure-driven systems generally exhibit a parabolic cross-sectional concentration profile through a channel. We draw inspiration from finite element fluid dynamics simulations to design and fabricate a practical solution to achieving a flat solute concentration profile in a two-dimensional (2D) microfluidic channel. The channel possesses geometric features to passively flatten the solute profile before entering the defined region of interest in the microfluidic channel. An obviously flat solute profile across the channel is demonstrated in both simulation and experiment. This technology readily lends itself to many microfluidic applications which require controlled solute transport in pressure driven systems.

Optical modeling and optimization of parabolic trough concentration photovoltaic/thermal system

AbstractIn this research, a genetic algorithm has been used to optimize the focal area of the parabolic trough concentration photovoltaic/thermal. First, based on the physical and thermodynamic variables, the system modeling was performed; then, by changing the variables were calculated the effect of these parameters on the electrical and thermal efficiencies. In the next step, the optimization was conducted by the mentioned algorithms. The objective function consists of two targets of electrical efficiency combined with thermal efficiency. The optimization variables include the length of the system, the pipe diameter, the collector diameter, mass flow rate, and the photovoltaic cell width. After running the program in the normal mode, the highest electrical and thermal efficiencies were 0.2063 and 0.4473 for the length of 10 m, the collector diameter of 1.2 m, the flow rate of 0.15 kg/s, the pipe diameter of 0.03 m, and the photovoltaic cell width of 0.02 m. According to the genetic algorithm, the optimal answer for the total efficiency of this system is 0.84737.

Thermal analysis of parabolic trough concentration photovoltaic/thermal system for using in buildings

In this research, a parabolic trough concentrating photovoltaic thermal (CPVT) was used to provide the energy needed for a residential building. In order to do this, the required amount of heating and cooling and electrical energy was first obtained using Carrier software, then the electrical demand was obtained according to the standard model and governing relations. In the next step, the CPVT as a source of heat and cooling, and electrical energy for the building, was simulated in TRNSYS software. In order to achieve the highest reliability in terms of heat supply and reduction of thermal losses in the whole system, phase‐change material was used as a heat storage source. Mehrabad (Tehran) was considered as the target area in simulation. For this area the highest radiation intensity is 7.79 kWh/m2·day, which shows the potential of the region. The simulation results of the studied system showed that the highest output temperature and solar fraction for total load in building from CPVT was 150°C and 0.0.2926. © 2019 American Institute of Chemical Engineers Environ Prog, 38: e13220, 2019

An effective three-marker drag model via sub-grid modeling for turbulent fluidization

The effect of meso-scale structures on hydrodynamic predictions is not considered in the classically uniform drag models when the coarse grid is used. To address this issue, this study tries to develop an effective three-marker drag correlation via straightforward sub-grid modeling, which accounts for a parabolic spatial concentration distribution within a computational grid. The reliability and accuracy of the developed model is then assessed in detail. How the uniform drag inputs affect the derived sub-grid correction is quantified for the first time. Besides, a comprehensive comparison between several typical sub-grid models and present work is implemented. Results reveal a systematic dependence of our drag modification on the concentration gradient as an additional marker. Coarse-grid hydrodynamic validation shows that the developed model yields a fairly improved agreement with experiments under various operating conditions in a 3D turbulent fluidized bed. Furthermore, results demonstrate that the present model using different uniform drag inputs still can exhibit satisfactory performance. The developed model is able to resolve the heterogeneous flow behavior both cheaply and adequately, which is potentially applied for industrial reactor design and optimization.

A tool for fast flux distribution calculation of parabolic trough solar concentrators

Parabolic trough concentration (PTC) systems are widespread technologies for the large-scale exploitation of solar energy. The flux density on the wall of the absorber of a PTC is non-uniform and complicated, and the calculation of flux distribution is key for estimating the optic performance of a PTC and analyzing the flow characteristic of the fluids in the tubular absorber. Traditional 3D ray-tracing methods for the calculation of flux distribution consume many computational resources and involve long CPU running time. This paper presents a 2D method for the fast calculation of the flux distribution of a PTC based on a descending dimension algorithm. By converting the PTC optical model from 3D space to 2D space, the calculation consumption required by the presented 2D method shrinks by two orders of magnitude compared to traditional 3D ray-tracing methods. Upon assessment, the method demonstrates a capacity to work out the flux density distribution within 0.22 s, compared to approximately 40 s required by traditional 3D ray-tracing methods, using a standard personal computer with a level of good accuracy, with a standard deviation of approximately 0.3 suns. Mathematical proof of this method was also provided. The numerical results were compared with those from the literature and a good agreement was observed, with the average standard deviation of 0.359 suns under different incident angles, proving the reliability of the method presented here. Based on this 2D method, a software tool was developed to facilitate the analysis of characteristics of solar PTC systems.

A numerical modelling study of SO2 adsorption on activated carbons with new rate equations

Modelling dynamic adsorption of sulfur dioxide (SO2) on activated carbons (ACs) is significant in guiding practical desulphurization processes and making highly efficient use of adsorbents in terms of the adsorption rate which largely depends on particle size. In this work, models derived from the Vermeulen and an improved linear driving force (LDF) rate equation were studied for the first time on SO2 adsorption over AC particles with different sizes. For larger particles (≥3 mm), breakthrough curves predicted by the Vermeulen equation showed good agreement with experimental data, demonstrating that intraparticle diffusion resistance varied with particle size, feed concentration, adsorption time and location. For smaller particles (1 mm), a correction on the volume-averaged adsorption capacity as a function of adsorption time and saturation in the rate equation was developed to avoid the underestimation of adsorption rate due to the inappropriate parabolic concentration profile inherent in the conventional LDF model. By providing a concentration gradient and adsorption rate closer to actual values, the improved LDF equation was confirmed to provide excellent prediction results on 1-mm particles. Different modelling characteristics of the two models indicates varying effects of intraparticle diffusion on adsorption rate with particle size regarding the specificity of SO2 physisorption on ACs.

Generation of Linear and Parabolic Concentration Gradients by Using a Christmas Tree-Shaped Microfluidic Network

This paper describes a simple method of generating concentration gradients with linear and parabolic profiles by using a Christmas tree-shaped microfluidic network. The microfluidic gradient generator consists of two parts: a Christmas tree-shaped network for gradient generation and a broad microchannel for detection. A two-dimensional model was built to analyze the flow field and the mass transfer in the microfluidic network. The simulating results show that a series of linear and parabolic gradient profiles were generated via adjusting relative flow rate ratios of the two source solutions (RL2 ≥0.995 and RP2 ≥0.999), which could match well with the experimental results (RL2 ≥0.987 and RP2 ≥0.996). The proposed method is promising for the generation of linear and parabolic concentration gradient profiles, with the potential in chemical and biological applications such as combinatorial chemistry synthesis, stem cell differentiation or cytotoxicity assays.

New Insights into Computational Fluid Dynamic (CFD) Modeling of Concentration Overpotential

Salinity gradient power (SGP) is a promising source of sustainable energy production involving technologies such as pressure retarded osmosis (PRO), reverse electrodialysis (RED) and capacitive mixing (CAPMIX). Coupling these technologies to their counterparts used for desalination, salinity gradient batteries can in principle be developed [1], as recently demonstrated for RED/ED [2]. Electrode and membrane processes typically involve an accumulation or depletion of specific ions compared the bulk solution, resulting in so called concentration polarization. Concentration polarization is a considerable challenge in RED/ED, effectively reducing the driving force across the membrane, hence reducing the performance of the process [3]. In addition to concentration polarization, the presence of concentration gradients will result in both Ohmic and non-Ohmic contributions to the electrical potential [3], further influencing the characteristics of the system. Different strategies have been proposed in order to mitigate the influence of concentration gradients, specifically increasing the flow velocity and introducing flow promoters – typically by optimizing the spacer geometry [3, 4] – in order to alter momentum and concentration boundary layers. The interaction between ionic species and fluid flow can be achieved by solving the coupled Navier-Stokes (NS) and Nernst-Planck (NP) equations [5,6], allowing for simultaneous prediction of flow and pressure fields, concentration and electrical potential, all of which of interest for the overall performance of the system. The current work describes a simulation framework for simulation of the NS-NP system based on the open source CFD platform OpenFOAM [7], aiming to predict the influence of flow conditions and geometry on concentration and electrical potential. Figure 1 (left) shows constant, linear and parabolic concentration profiles, corresponding to the extreme conditions of plug and Poiseuille flow in a flat channel, with the corresponding results for electrical potential in Figure 1 (right), clearly demonstrating the strong coupling between the two. The suggested framework is applied to spacer filled channels aiming to describe pros and cons of different configurations such as height and pitch of spacers. The presented approach sheds light on future concentration polarization modeling, providing better descriptions of the mass transfer and electric potential and highlighting the role of spacer-filled channel in membrane based processes.