Optimization of Focusing Solar-Collector Design

1963 ◽  
Vol 85 (3) ◽  
pp. 221-228 ◽  
Author(s):  
G. O. G. Lo¨f ◽  
J. A. Duffie
Keyword(s):  
Optical Properties ◽  
Radiation Intensity ◽  
Solar Collector ◽  
Loss Rate ◽  
Incident Radiation ◽  
Area Ratio ◽  
Thermal Loss ◽  
Economic Optimization ◽  
Useful Heat ◽  
Incident Radiation Intensity

A set of general graphical relationships has been developed for establishing the receiver-reflector area ratio which will provide the maximum useful heat delivery from a focusing collector. The method, applied to paraboloids and parabolic cylinders, gives the optimum area ratio in terms of incident radiation intensity, optical properties (including precision of reflector), and thermal loss rate. Use of the method for design and for evaluation of existing reflectors is illustrated; its use in economic optimization will be dependent on availability of adequate cost data.

Saturation characteristics of SF6 absorption at the 10.4 μm band of CO2

1977 ◽  
Vol 55 (10) ◽  
pp. 849-854 ◽  
Author(s):  
B. K. Garside ◽  
R. S. Taylor ◽  
E. A. Ballik
Keyword(s):  
Nonlinear Absorption ◽  
Radiation Intensity ◽  
Pulse Shaping ◽  
Incident Radiation ◽  
Absorption Properties ◽  
Molecular Parameters ◽  
Distinctive Features ◽  
P 16 ◽  
Level Model ◽  
Incident Radiation Intensity

Measurements were made of the saturation characteristics of the SF6 absorption at the 10.4 μm band of CO2, using a pulsed CO2 laser. It is shown that the observed nonlinear absorption properties can be divided into three characteristic regions, namely P(12)–P(16), P(18)–P(22), and P(24)–P(30), each of which has distinctive features in the measured transmission as a function of incident radiation intensity. In each region, this transmission behaviour, together with associated dynamical effects such as pulse shaping, are amenable to interpretation by means of a four-level model for the SF6 absorption. The relevant molecular parameters are determined by comparison of theory with experiment.

scholarly journals Модификация спектров фотопроводимости в композитных структурах ZnO-квантовые точки CdSe под действием дополнительного фотовозбуждения

2018 ◽  
Vol 52 (7) ◽  
pp. 763
Author(s):  
К.А. Дроздов ◽  
И.В. Крылов ◽  
А.С. Чижов ◽  
М.Н. Румянцева ◽  
Л.И. Pябова ◽  
...  
Keyword(s):  
Radiation Intensity ◽  
Spectral Region ◽  
Incident Radiation ◽  
Visible Spectral Region ◽  
Cds Nanocrystals ◽  
Incident Radiation Intensity ◽  
Wavelength Distribution

AbstractThe incorporation of CdS nanocrystals into a porous ZnO matrix results in sensitization of the composite in the visible spectral region. Studies of the photoconductivity spectra upon variable external illumination show that the spectra undergo reversible transformations. It is shown that the shape of the peak and the position of the local photoconductivity maximum corresponding to nanocrystals depend on the wavelength distribution of the incident radiation intensity. The mechanisms responsible for the process are discussed.

scholarly journals The Effect of Cooling Water Mass Flow Rate Variations on the Heat Pipe Solar Collector Performance

2017 ◽  
Vol 5 (2) ◽  
pp. 31-41
Author(s):  
Abdulsalam D. M. Hassan ◽  
Rwaa Alaa Hussein
Keyword(s):  
Flow Rate ◽  
Solar Collector ◽  
Experimental Studies ◽  
Cooling Water ◽  
Percentage Increase ◽  
Cover Glass ◽  
Language Version ◽  
Theoretical Predictions ◽  
Useful Heat ◽  
Water Mass Flow Rate

The thermal performance of FPHPSC has been studied experimentally and theoretically. The collector consists of copper absorber plate, single glass cover, glass wool insulation and aluminum case. Ten wickless heat pipes of 12.7 mm inner diameter. The experimental studies of collector performance have been performed on four different CWMFR (0.03, 0.04, 0.05 and 0.06) kg/s. The relation between the amount of useful heat, instantaneous collector efficiency and solar intensity is discussed. The collector are tested under the climate condition of Kut city (32.6 latitude and 45.7 longitude). It is investigated that the increasing of CWMFR increase the efficiency of the collector. The percentage increase in the efficiency of the solar collector is in order of (13%), when the cooling water mas flow rate changes from 0.03 kg/sec to 0.06 kg/sec at (45o) collector tilt angle. A computer program based on VISUAL BASIC language (version 6) used for the theoretical analysis. The experimental results are in agreement reasonably with the theoretical predictions.

scholarly journals О рассеянии света двухслойными эллипсоидами с несофокусными границами

2020 ◽  
Vol 128 (8) ◽  
pp. 1144
Author(s):  
В.Б. Ильин ◽  
В.Г. Фарафонов ◽  
М.С. Прокопьева ◽  
В.И. Устимов
Keyword(s):  
Optical Properties ◽  
Incident Radiation ◽  
Analytical Approximation ◽  
New Approaches ◽  
Dielectric Particles ◽  
Diffraction Parameter

New approaches to calculate the optical properties of small nonspherical layered particles whose layer boundaries are nonconfocal concentric coaxial ellipsoids are considered. A simple analytical approximation is suggested and substantiated for the case when the size of similar layer particles is much less than the wavelength of the incident radiation. It is found that this approximation provides the results with the accuracy of about 0.003 when the diffraction parameter x < 0.1. An approach to calculate the optical properties of nonconfocal ellipsoids by using a substitute of the nonconfocal boundaries with the confocal ones with keeping the layer volumes constant is justified. It is shown that for dielectric particles such an approach has the accuracy of a few percent for x < 1 and about 20% for x < 5. It is noted that both approximations are easily expanded on the case of multilayered nonconfocal ellipsoids.

Thermal Radiative Properties of Vertical Graphitic Petal Arrays

2012 ◽  
Author(s):  
Bhagirath Duvvuri ◽  
Anurag Kumar ◽  
Hua Bao ◽  
Haoxiang Huang ◽  
Timothy Fisher ◽  
...  
Keyword(s):  
Optical Properties ◽  
Electric Field ◽  
Finite Difference Time Domain ◽  
Incident Radiation ◽  
Radiative Properties ◽  
Thermal Radiative Properties ◽  
Fdtd Simulations ◽  
Difference Time ◽  
Graphitic Plane ◽  
Very High

In this work, thermal radiative properties of vertical graphene petal arrays are theoretically and experimentally investigated to show that they are superior absorbers of radiation. Finite difference time domain (FDTD) simulations are first performed to calculate optical properties of vertical graphitic arrays of different configurations, namely, graphitic gratings, periodic graphitic cavities, and random graphitic cavities. The effect of polarization of incident radiation on optical properties of such structures is systematically evaluated. When the incident electric field is parallel to the graphitic plane (S polarization) in graphitic gratings, the absorptance is very high, but the reflectance low but still significant when compared to reflectance from a MWCNT array. On the other hand, when the electric field is polarized perpendicular to the graphitic plane (P polarization), the absorptance is significantly lower, as well as the reflectance. This contrast is due to the stronger optical response for the S polarization. Ordered graphitic petal cavity arrays show optical properties falling between the above two cases because of the presence of both polarizations. The random graphitic petal cavity arrays with various angles of orientation show similar properties with ordered petal arrays, and the simulated reflectance agrees very well with experimental data measured on a fabricated thin graphite petal sample.

scholarly journals Effects of internal mixing and aggregate morphology on optical properties of black carbon using a discrete dipole approximation model

2012 ◽  
Vol 12 (10) ◽  
pp. 26401-26434 ◽  
Author(s):  
B. Scarnato ◽  
S. Vahidinia ◽  
D. T. Richard ◽  
T. W. Kirchstetter
Keyword(s):  
Optical Properties ◽  
Black Carbon ◽  
Linear Polarization ◽  
Incident Radiation ◽  
Dipole Approximation ◽  
Approximation Model ◽  
Mixing State ◽  
Internal Mixing ◽  
Aggregate Morphology ◽  
Nm Range

Abstract. According to recent studies, internal mixing of black carbon (BC) with other aerosol materials in the atmosphere alters its aggregate shape, absorption of solar radiation, and radiative forcing. These mixing state effects are not yet fully understood. In this study, we characterize the morphology and mixing state of bare BC and BC internally mixed with sodium chloride (NaCl) using electron microscopy and examine the sensitivity of optical properties to BC mixing state and aggregate morphology using a discrete dipole approximation model (DDSCAT). DDSCAT predicts a higher mass absorption coefficient, lower single scattering albedo (SSA), and higher absorption Angstrom exponent (AAE) for bare BC aggregates that are lacy rather than compact. Predicted values of SSA at 550 nm range between 0.18 and 0.27 for lacy and compact aggregates, respectively, in agreement with reported experimental values of 0.25 ± 0.05. The variation in absorption with wavelength does not adhere precisely to a power law relationship over the 200 to 1000 nm range. Consequently, AAE values depend on the wavelength region over which they are computed. In the 300 to 550 nm range, AAE values ranged in this study from 0.70 for compact to 0.95 for lacy aggregates. The SSA of BC internally mixed with NaCl (100–300 nm in radius) is higher than for bare BC and increases with the embedding in the NaCl. Internally mixed BC SSA values decrease in the 200–400 nm wavelength range, a feature also common to the optical properties of dust and organics. Linear polarization features are also predicted in DDSCAT and are dependent on particle morphology. The bare BC (with a radius of 80 nm) presents in the linear polarization a bell shape feature, which is a characteristic of the Rayleigh regime (for particles smaller than the wavelength of incident radiation). When BC is internally mixed with NaCl (100–300 nm in radius), strong depolarization features for near-VIS incident radiation are evident, such as a decrease in the intensity and multiple modes at different angles corresponding to different mixing states. DDSCAT, being flexible on the geometry and refractive index of the particle, can be used to study the effect of mixing state and complex morphology on optical properties of realistic BC aggregates. This study shows that DDSCAT predicts morphology and mixing state dependent optical properties that have been reported previously and are relevant to radiative transfer and climate modeling and interpretation of remote sensing measurements.

Obtaining Solar Collector Cover-Plate Transmissivities From a Solar Simulator

1986 ◽  
Vol 108 (4) ◽  
pp. 316-319 ◽  
Author(s):  
B. W. Fintel ◽  
G. S. Jakubowski
Keyword(s):  
Optical Properties ◽  
Experimental Method ◽  
Solar Collector ◽  
Close Agreement ◽  
Float Glass ◽  
Cover Plate ◽  
Solar Collectors ◽  
Solar Simulator ◽  
Practical Tool ◽  
Solar Angle

Transmissivities, as a function of incident solar angle, were experimentally determined for various commercially available cover-plate materials using actual outdoor and indoor simulated solar conditions. The glazing materials tested were float glass, plexiglass, fiberglass, and several window films. Since the optical properties of many of these materials are not readily available, the transmissivities could not be calculated analytically. Therefore, the experimental method proved to be invaluable. Furthermore, transmissivities determined from indoor data were found to be in close agreement with outdoor results, making the simulator a practical tool. The transmissivities determined and the methods provided in this paper can be valuable in the design of solar collectors.

scholarly journals Numerical simulation of concentrating solar collector P2CC with a small concentrating ratio

2012 ◽  
Vol 16 (suppl. 2) ◽  
pp. 471-482 ◽  
Author(s):  
Velimir Stefanovic ◽  
Sasa Pavlovic ◽  
Marko Ilic ◽  
Nenad Apostolovic ◽  
Dragan Kustrimovic
Keyword(s):  
Mathematical Model ◽  
Fluid Flow ◽  
Solar Radiation ◽  
Solar Energy ◽  
Radiation Intensity ◽  
Solar Collector ◽  
Numerical Procedure ◽  
Working Fluid ◽  
Flow Rates ◽  
Solar Radiation Intensity

Solar energy may be practically utilized directly through transformation into heat, electrical or chemical energy. A physical and mathematical model is presented, as well as a numerical procedure for predicting thermal performances of the P2CC solar concentrator. The demonstrated prototype has the reception angle of 110? at concentration ratio CR = 1.38, with the significant reception of diffuse radiation. The solar collector P2CC is designed for the area of middle temperature conversion of solar radiation into heat. The working fluid is water with laminar flow through a copper pipe surrounded by an evacuated glass layer. Based on the physical model, a mathematical model is introduced, which consists of energy balance equations for four collector components. In this paper, water temperatures in flow directions are numerically predicted, as well as temperatures of relevant P2CC collector components for various values of input temperatures and mass flow rates of the working fluid, and also for various values of direct sunlight radiation and for different collector lengths. The device which is used to transform solar energy to heat is referred to as solar collector. This paper gives numerical estimated changes of temperature in the direction of fluid flow for different flow rates, different solar radiation intensity and different inlet fluid temperatures. The increase in fluid flow reduces output temperature, while the increase in solar radiation intensity and inlet water temperature increases output temperature of water. Furthermore, the dependence on fluid output temperature is determined, along with the current efficiency by the number of nodes in the numerical calculation.

Dielectric Nano-Systems with Unique Optical Properties

2013 ◽  
Vol 677 ◽  
pp. 36-41 ◽  
Author(s):  
Yurii N. Kulchin ◽  
Vladimir P. Dzyuba ◽  
Valentin A. Milichko
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Absorption Coefficient ◽  
Radiation Intensity ◽  
Optical Nonlinearity ◽  
Energy Structure ◽  
Optical Fields ◽  
Coefficient Increase ◽  
Intensity Changes ◽  
Theoretical Results

The study of optical properties of Al2O3, SiO2, TiO2, and ZnO nanoparticles in weak optical fields is presented. We found that some nanoparticles have unique optical nonlinearity: The values of portions to nanoparticle refractive index and absorption coefficient increase to maxima, and then decrease to zero when the radiation intensity changes from 1 to 500 W/cm2. We estimated electron energy structures of nanoparticles and experimentally determined that such nonlinearity is directly related to peculiarities of the energy structure. We obtained a good fitting of theoretical results to the experimental ones (e.g. absorbance spectra of nanoparticles; the dependence of nanoparticle refractive index and absorption coefficient on radiation intensity).

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