2007-11-02
the former preferred for high-temperature collectors since it is opaque in the longer wavelength region and hence improves the efficiency by reducing re...different temperature regions . The analyses show that collectors equipped with Lexan honeycomb are more cost ef- fective than comparable nonhoneycomb...Contract E(04-3)- 1081. " REFERENCES 1. Francia , G., "A New Collector of Solar Energy -- Theory and Experimental Verification -- Calculation of the
Design optimization of sinusoidal glass honeycomb for flat plate solar collectors
Mcmurrin, J. C.; Buchberg, H.
1980-01-01
The design of honeycomb made of sinusoidally corrugated glass strips was optimized for use in water-cooled, single-glazed flat plate solar collectors with non-selective black absorbers. Cell diameter (d), cell height (L), and pitch/diameter ratio (P/d) maximizing solar collector performance and cost effectiveness for given cell wall thickness (t sub w) and optical properties of glass were determined from radiative and convective honeycomb characteristics and collector performance all calculated with experimentally validated algorithms. Relative lifetime values were estimated from present materials costs and postulated production methods for corrugated glass honeycomb cover assemblies. A honeycomb with P/d = 1.05, d = 17.4 mm, L = 146 mm and t sub w = 0.15 mm would provide near-optimal performance over the range delta T sub C greater than or equal to 0 C and less than or equal to 80 C and be superior in performance and cost effectiveness to a non-honeycomb collector with a 0.92/0.12 selective black absorber.
Energy Technology Data Exchange (ETDEWEB)
Srithar, K. [Department of Mechanical Engineering, Thiagarajar College of Engineering, Madurai 625 015 (India); Mani, A. [Department of Mechanical Engineering, Indian Institute of Technology, Madras, Chennai 600 036 (India)
2007-12-15
Presently, tanneries in Tamilnadu, India are required to segregate the effluent of soaking and pickling sections from other wastewater streams and send it to shallow solar pans for evaporation to avoid land pollution. A large area of solar pans is required for evaporating the water in the effluent at salt concentration in the range of 4-5%. An experimental study has been made by using fibre reinforced plastic flat plate collector (FRP-FPC) and spray system in a pilot plant with a capacity to handle 5000 l per day, which increases the evaporation rate. After increasing the salt concentration level to near saturation limit, the concentrated liquid was sent to conventional solar pans for its continued evaporation and recovery of salt. In this improved system, the rate of evaporation was found to be 30-40% more than that in the conventional solar pans. The performance is compared with the theoretically simulated performance. (author)
High Performance Flat Plate Solar Thermal Collector Evaluation
Energy Technology Data Exchange (ETDEWEB)
Rockenbaugh, Caleb [National Renewable Energy Lab. (NREL), Golden, CO (United States); Dean, Jesse [National Renewable Energy Lab. (NREL), Golden, CO (United States); Lovullo, David [National Renewable Energy Lab. (NREL), Golden, CO (United States); Lisell, Lars [National Renewable Energy Lab. (NREL), Golden, CO (United States); Barker, Greg [National Renewable Energy Lab. (NREL), Golden, CO (United States); Hanckock, Ed [National Renewable Energy Lab. (NREL), Golden, CO (United States); Norton, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States)
2016-09-01
This report was prepared for the General Services Administration by the National Renewable Energy Laboratory. The Honeycomb Solar Thermal Collector (HSTC) is a flat plate solar thermal collector that shows promising high efficiencies over a wide range of climate zones. The technical objectives of this study are to: 1) verify collector performance, 2) compare that performance to other market-available collectors, 3) verify overheat protection, and 4) analyze the economic performance of the HSTC both at the demonstration sites and across a matrix of climate zones and utility markets.
High performance flat plate solar collector
Lansing, F. L.; Reynolds, R.
1976-01-01
The potential use of porous construction is presented to achieve efficient heat removal from a power producing solid and is applied to solar air heaters. Analytical solutions are given for the temperature distribution within a gas-cooled porous flat plate having its surface exposed to the sun's energy. The extracted thermal energy is calculated for two different types of plate transparency. Results show the great improvement in performance obtained with porous flat plate collectors as compared with analogous nonporous types.
Measurements of Flat-Plate Milk Coolers
Directory of Open Access Journals (Sweden)
Vlastimil Nejtek
2014-01-01
Full Text Available Measuring in laboratory conditions was performed with the aim to collect a sufficient quantity of measured data for the qualified application of flat-plate coolers in measuring under real operating conditions. The cooling water tank was filled with tap water; the second tank was filled with water at a temperature equivalent to freshly milked milk. At the same time, pumps were activated that delivered the liquids into the flat-plate cooler where heat energy was exchanged between the two media. Two containers for receiving the run-out liquid were placed on the outputs from the cooler; here, temperature was measured with electronic thermometer and volume was measured with calibrated graduated cylinder. Flow rate was regulated both on the side of the cooling fluid and on the side of the cooled liquid by means of a throttle valve. The measurements of regulated flow-rates were repeated several times and the final values were calculated using arithmetic average. To calculate the temperature coefficient and the amount of brought-in and let-out heat, the volume measured in litres was converted to weight unit. The measured values show that the volume of exchanged heat per weight unit increases with the decreasing flow-rate. With the increasing flow-rate on the throttled side, the flow-rate increases on the side without the throttle valve. This phenomenon is caused by pressure increase during throttling and by the consequent increase of the diameter of channels in the cooler at the expense of the opposite channels of the non-throttled part of the circuit. If the pressure is reduced, there is a pressure decrease on the external walls of opposite channels and the flow-rate increases again. This feature could be utilised in practice: a pressure regulator on one side could regulate the flow-rate on the other side. The operating measurement was carried out on the basis of the results of laboratory measurements. The objective was to determine to what extent the
Studies on solar flat plate collector evaporation systems for tannery effluent (soak liquor)
Institute of Scientific and Technical Information of China (English)
SRITHAR K.; MANIA.
2006-01-01
Heat and mass transfer analysis of an incompressible, laminar boundary layer over solar flat plate collector evaporation systems for tannery effluent (soak liquor) is investigated. The goveming equations are solved for various liquid to air velocity ratios. Profiles of velocity, temperature and concentration as well as their gradients are presented. The heat transfer and mass transfer coefficients thus obtained are used to evaluate mass of water evaporated for an inclined fibre-reinforced plastic (FRP)solar flat plate collector (FPC) with and without cover. Comparison of these results with the experimental performance shows encouraging trend of good agreement between them.
A bubble column evaporator with basic flat-plate condenser for brackish and seawater desalination.
Schmack, Mario; Ho, Goen; Anda, Martin
2016-01-01
This paper describes the development and experimental evaluation of a novel bubble column-based humidification-dehumidification system, for small-scale desalination of saline groundwater or seawater in remote regions. A bubble evaporator prototype was built and matched with a simple flat-plate type condenser for concept assessment. Consistent bubble evaporation rates of between 80 and 88 ml per hour were demonstrated. Particular focus was on the performance of the simple condenser prototype, manufactured from rectangular polyvinylchlorid plastic pipe and copper sheet, a material with a high thermal conductivity that quickly allows for conduction of the heat energy. Under laboratory conditions, a long narrow condenser model of 1500 mm length and 100 mm width achieved condensate recovery rates of around 73%, without the need for external cooling. The condenser prototype was assessed under a range of different physical conditions, that is, external water cooling, partial insulation and aspects of air circulation, via implementing an internal honeycomb screen structure. Estimated by extrapolation, an up-scaled bubble desalination system with a 1 m2 condenser may produce around 19 l of distilled water per day. Sodium chloride salt removal was found to be highly effective with condensate salt concentrations between 70 and 135 µS. Based on findings and with the intent to reduce material cost of the system, a shorter condenser length of 750 mm for the non-cooled (passive) condenser and of 500 mm for the water-cooled condenser was considered to be equally efficient as the experimentally evaluated prototype of 1500 mm length.
REVIEW OF PERFORMANCE AND ANALYSIS ISI FLAT PLATE COLLECTOR WITH MODIFIED FLAT PLATE COLLECTOR
Directory of Open Access Journals (Sweden)
MR.Y.Y.NANDURKAR
2012-03-01
Full Text Available The market of solar water heater of natural circulation type (thermo-siphon is fast growing in India. Initial cost of the solar water heater system at present is high because of store type design. It is necessary to make the product more popular by reducing the cost. This is possible by reducing area of liquid flat plate collector by increasing tube diameter and reducing riser length. Hence it is essential to make solar water heater in affordable range of the general public class. Present work is based on review of comparative performance and analysis of ISI flat plate collector with modified flat plat collector. The paper will be helpful for those who are working in the area of solar water heating system and their use in domestic areas.
Flexural Behavior of Posttensioned Flat Plates Depending on Tendon Layout
Directory of Open Access Journals (Sweden)
Min Sook Kim
2016-01-01
Full Text Available This paper discusses the experimental results on the flexural behavior and deflections of posttensioned concrete flat plates depending on tendon layout. One reinforced concrete flat plate and two posttensioned concrete flat plates were manufactured and tested. One-way posttensioning layout and two-way posttensioning layout were considered in this paper. The load-deflection behavior and modes of crack are presented from the test results. Posttension systems effectively controlled crack and deflection. One-way and two-way posttensioning layouts both showed similar maximum load. However, serviceability improved with two-way posttensioning layout compared to one-way posttensioning layout. Also, the yield-line theory was applied to predict the ultimate load for the posttensioned flat plates. The comparison between the test results and estimation by yield-line analysis generally showed good agreement.
Analysis of Flat-Plate Solar Array and Solar Lantern
Directory of Open Access Journals (Sweden)
P. L. N. V. Aashrith
2014-05-01
Full Text Available A very detailed theortical analysis of a solar array has been carried out based on established values of solar radiation data to predict the performance of solar lamp . The analysis is based on established theory about flat-plate collectors. Top heat loss coefficient (Ut, Bottom heat loss coefficient (Ub, Overall heat loss coefficient (Ul, Useful energy (Qu, efficiency (hp of the flat-plate solar array and efficiency (hl of the solar lantern has been calculated.
Investigation of Shear Stud Performance in Flat Plate Using Finite Element Analysis
Directory of Open Access Journals (Sweden)
T.S. Viswanathan
2014-09-01
Full Text Available Three types of shear stud arrangement, respectively featuring an orthogonal, a radial and a critical perimeter pattern, were evaluated numerically. A numerical investigation was conducted using the finite element software ABAQUS to evaluate their ability to resist punching shear in a flat plate. The finite element analysis here is an application of the nonlinear analysis of reinforced concrete structures using three-dimensional solid finite elements. The nonlinear characteristics of concrete were achieved by employing the concrete damaged plasticity model in the finite element program. Transverse shear stress was evaluated using finite element analysis in terms of shear stress distribution for flat plate with and without shear stud reinforcement. The model predicted that shear studs placed along the critical perimeter are more effective compared to orthogonal and radial patterns.
Laminar film boiling on inclined isothermal flat plates.
Nagendra, H. R.
1973-01-01
Laminar film boiling from an inclined flat plate has been investigated analytically. Using the singular perturbation scheme, the complete set of Navier-Stokes equations is solved. The zeroth-order perturbation coinciding with the boundary-layer equations for vertical flat plates governs the problem. The higher-order perturbations become important near the leading edge and for large values of the inclination angle from the vertical. The assumption of zero interfacial velocity shows that, except for fluids having large (rho x mu) ratios, the results can be predicted using the vertical flat plate results by defining a modified Grashof parameter containing a cos phi term. When the interfacial shear is considered, the solutions indicate that for fluids having large (rho x mu) ratios, the heat transfer rates will be larger (approximately 15% maximum) than those predicted by the simplified model using zero interfacial velocity. In general, the inclination decreases the rate of heat transfer as well as the rate of evaporation.
Shear flow past a flat plate in hydromagnetics
Directory of Open Access Journals (Sweden)
S. R. N. Sastry
1980-01-01
Full Text Available The problem of simple shear flow past a flat plate has been extended to the hydromagnetic case in which a viscous, electrically conducting, incompressible fluid flows past an electrically insulated flat plate with a magnetic field parallel to the plate. For simplicity all physical parameters are assumed constant. A series solution for the velocity field has been developed for small values of a magnetic parameter. The equations governing this flow field were integrated numerically It is found that the effect of the magnetic field is to diminish and increase respectively, the first and second order contributions for the skin friction.
Numerical 3-D heat flux simulations on flat plate solar collectors
Energy Technology Data Exchange (ETDEWEB)
Villar, N. Molero; Lopez, J.M. Cejudo; Munoz, F. Dominguez; Garcia, E. Rodriguez; Andres, A. Carrillo [Grupo de Energetica, Escuela Tecnica Superior de Ingenieros Industriales, UMA, Plaza El Ejido s/n, 29013 Malaga (Spain)
2009-07-15
A transient 3-D mathematical model for solar flat plate collectors has been developed. The model is based on setting mass and energy balances on finite volumes. The model allows the comparison of different configurations: parallel tubes collectors (PTC), serpentine tube collectors (STC), two parallel plate collectors (TPPC), and other non-usual possibilities like the use of absorbent fluids with semitransparent or transparent plates. Transparent honeycomb insulation between plate and cover can also be modelled. The effect of temperature on the thermal properties of the materials has also been considered. The model has been validated experimentally with a commercial PTC. The model is a useful tool to improve the design of plate solar collectors and to compare different configurations. In order to show the capabilities of the model, the performance of a PTC collector with non-uniformity flow is analysed and compared with experimental data from literature with good agreement. (author)
Certification and verification for calmac flat plate solar collector
Energy Technology Data Exchange (ETDEWEB)
1978-01-27
This document contains information used in the certification and verification of the Calmac Flat Plate Collector. Contained are such items as test procedures and results, information on materials used, Installation, Operation, and Maintenance Manuals, and other information pertaining to the verification and certification.
The structure of subsonic air wakes behind a flat plate
Energy Technology Data Exchange (ETDEWEB)
Barreras, F.; Dopazo, C. [Centro Politecnico Superior de Ingenieros Area de Mecanica de Fluidos, Zaragoza (Spain); Lozano, A.; Yates, A.J. [LITEC/CSIC, Maria de Luna 3 E-50015-Zaragoza (Spain)
1999-04-01
Acetone vapor planar laser-induced fluorescence has been used to visualize the structure of a subsonic air wake behind a flat plate. Longitudinal and transversal wavelengths have been directly measured from the acquired images. The ratio between them has been calculated to be 2/5. (orig.) With 3 figs., 1 tab., 10 refs.
COMPARATIVE FIELD EXPERIMENTAL INVESTIGATIONS OF DIFFERENT FLAT PLATE SOLAR COLLECTORS
Directory of Open Access Journals (Sweden)
Guangming Chen
2015-12-01
Full Text Available Full-scale traditional metal solar collectors and solar collector specimens fabricated from polymeric materials were investigated in the present study. A polymeric collector is 67.8% lighter than a traditional metal solar collector, and a metal solar collector with transparent plastic covering is 40.3% lighter than a traditional metal solar collector. Honeycomb multichannel plates made from polycarbonate were chosen to create a polymeric solar collector. A test rig for the natural circulation of the working fluid in a solar collector was built for a comparative experimental investigation of various solar collectors operating at ambient conditions. It was shown experimentally that the efficiency of a polymeric collector is 8–15% lower than the efficiency of a traditional collector.
Detailed Modeling of Flat Plate Solar Collector with Vacuum Glazing
Directory of Open Access Journals (Sweden)
Viacheslav Shemelin
2017-01-01
Full Text Available A theoretical analysis of flat plate solar collectors with a vacuum glazing is presented. Different configurations of the collector have been investigated by a detailed theoretical model based on a combined external and internal energy balance of the absorber. Performance characteristics for vacuum flat plate collector alternatives have been derived. Subsequently, annual energy gains have been evaluated for a selected variant and compared with state-of-the-art vacuum tube collectors. The results of modeling indicate that, in the case of using advanced vacuum glazing with optimized low-emissivity coating (emissivity 0.20, solar transmittance 0.85, it is possible to achieve efficiency parameters similar to or even better than vacuum tube collectors. The design presented in this paper can be considered promising for the extension of the applicability range of FPC and could be used in applications, which require low-to-medium temperature level.
A dynamic simulation of a flat-plate collector system
Annino, A.
1983-04-01
A numerical model for the performance of a flat plate solar collector array is presented, with account taken of thermal transients and calculation on a microcomputer. The system modeled consists of a flat plate array, the heat transfer fluid, an insulated storage tank, an exchange loop for heating a secondary fluid, and a load maintained by a pump. The one-dimensional analysis includes equations for the energy balances, with consideration given to heat losses to the outside. A function is defined for the total incident solar radiation, and behavior is simulated over the entire 24-hr day, weighted by the highest and lowest recorded temperatures. Good agreement has been found with experimental data.
Flat Plate Reduction in a Water Tunnel Using Riblets
1987-05-01
II ~Ci +c SE- 2 8 0Lg E (D so (wwI) 10 DRAG CALCULATIONS The drag on the flat plate was calculated using D = bpU 20 The drag reduction over the...described in the previous section, are used so that bpU 2. is a constant, and that the drag upstream of the leading edge of the test surface is the same
EM Scattering from Conducting Flat Plates Coated with Thin RAM
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
According to the equivalence principles, high frequency approximation and boundary conditions, a method has been developed to deal with the EM scattering by a rectangular conducting flat plate coated with uniaxial anisotropic radar absorbing material (RAM). The simple and effective method is available to the system of RCS prediction in which the large complex targets modeled by facets and wedges. Numerical results show some properties of EM scattering by conducting plate coated with thin uniaxial anisotropic RAM.
Unsteady Reversed Stagnation-Point Flow over a Flat Plate
Sin, Vai Kuong; Chio, Chon Kit
2012-01-01
This paper investigates the nature of the development of two-dimensional laminar flow of an incompressible fluid at the reversed stagnation-point. ". In this study, we revisit the problem of reversed stagnation-point flow over a flat plate. Proudman and Johnson (1962) first studied the flow and obtained an asymptotic solution by neglecting the viscous terms. This is no true in neglecting the viscous terms within the total flow field. In particular it is pointed out that for a plate impulsivel...
Unsteady Reversed Stagnation-Point Flow over a Flat Plate
Sin, Vai Kuong
2013-01-01
This paper investigates the nature of the development of two-dimensional laminar flow of an incompressible fluid at the reversed stagnation-point. ". In this study, we revisit the problem of reversed stagnation-point flow over a flat plate. Proudman and Johnson (1962) first studied the flow and obtained an asymptotic solution by neglecting the viscous terms. This is no true in neglecting the viscous terms within the total flow field. In particular it is pointed out that for a plate impulsively accelerated from rest to a constant velocity V0 that a similarity solution to the self-similar ODE is obtained which is noteworthy completely analytical.
Calculating the Solar Energy of a Flat Plate Collector
Directory of Open Access Journals (Sweden)
Ariane Rosario
2014-09-01
Full Text Available The amount of solar energy that could be obtained by a flat plate solar collector of one square meter dimension is calculated in three different locations: Tampa FL, Fairbanks AL, and Pontianak Indonesia, considering the varying sunset time for each day of the year. The results show that if the collectors are placed near the equator, more total energy could be obtained. In fact, by placing a solar collector in Pontianak, Indonesia 12.42% more solar energy can be obtained than by placing it in Tampa and 96.9% more solar energy than Alaska.
Efficiencies of flat plate solar collectors at different flow rates
DEFF Research Database (Denmark)
Chen, Ziqian; Furbo, Simon; Perers, Bengt;
2012-01-01
Two flat plate solar collectors for solar heating plants from Arcon Solvarme A/S are tested in a laboratory test facility for solar collectors at Technical University of Denmark (DTU). The collectors are designed in the same way. However, one collector is equipped with an ETFE foil between...... the absorber and the cover glass and the other is without ETFE foil. The efficiencies for the collectors are tested at different flow rates. On the basis of the measured efficiencies, the efficiencies for the collectors as functions of flow rate are obtained. The calculated efficiencies are in good agreement...
Pure and aerated water entry of a flat plate
Ma, Z. H.; Causon, D. M.; Qian, L.; Mingham, C. G.; Mai, T.; Greaves, D.; Raby, A.
2016-01-01
This paper presents an experimental and numerical investigation of the entry of a rigid square flat plate into pure and aerated water. Attention is focused on the measurement and calculation of the slamming loads on the plate. The experimental study was carried out in the ocean basin at Plymouth University's COAST laboratory. The present numerical approach extends a two-dimensional hydro-code to compute three-dimensional hydrodynamic impact problems. The impact loads on the structure computed by the numerical model compare well with laboratory measurements. It is revealed that the impact loading consists of distinctive features including (1) shock loading with a high pressure peak, (2) fluid expansion loading associated with very low sub-atmospheric pressure close to the saturated vapour pressure, and (3) less severe secondary reloading with super-atmospheric pressure. It is also disclosed that aeration introduced into water can effectively reduce local pressures and total forces on the flat plate. The peak impact loading on the plate can be reduced by half or even more with 1.6% aeration in water. At the same time, the lifespan of shock loading is prolonged by aeration, and the variation of impulse is less sensitive to the change of aeration than the peak loading.
Experiments to investigate lift production mechanisms on pitching flat plates
Stevens, P. R. R. J.; Babinsky, H.
2017-01-01
Pitching flat plates are a useful simplification of flapping wings, and their study can provide useful insights into unsteady force generation. Non-circulatory and circulatory lift producing mechanisms for low Reynolds number pitching flat plates are investigated. A series of experiments are designed to measure forces and study the unsteady flowfield development. Two pitch axis positions are investigated, namely a leading edge and a mid-chord pitch axis. A novel PIV approach using twin laser lightsheets is shown to be effective at acquiring full field of view velocity data when an opaque wing model is used. Leading-edge vortex (LEV) circulations are extracted from velocity field data, using a Lamb-Oseen vortex fitting algorithm. LEV and trailing-edge vortex positions are also extracted. It is shown that the circulation of the LEV, as determined from PIV data, approximately matches the general trend of an unmodified Wagner function for a leading edge pitch axis and a modified Wagner function for a mid-chord pitch axis. Comparison of experimentally measured lift correlates well with the prediction of a reduced-order model for a LE pitch axis.
Unsteady Aerodynamics on a Pitching Plunging Flat Plate
Hart, Adam; Ukeiley, Lawrence
2010-11-01
Biology has shown that natural fliers utilize unsteady flow mechanisms to enhance their lift characteristics in low Reynolds number flight regimes. This study will investigate the interaction between the leading edge vortices (LEVs) and tip vortices over a low aspect ratio flat plate being subjected to a pitch-plunge kinematic motion. Previous studies have shown the creation of stable vortices off the leading edge at the three quarter span location between times 0.25 and 0.50 in the kinematic motion. This study furthers previous knowledge by mapping the flow field around these vortex cores. This will allow for an understanding into the interaction of the LEV with tip vortices and how the LEVs convect downstream. Specifically we look to validate the interactions between these vortex systems leading to enhanced lift as has been demonstrated in very low Reynolds number numerical simulations. A combination of two dimensional and stereo Particle Image Velocimetery (PIV) is used to measure the flow field around the flat plate at various spanwise and chordwise locations. The PIV measurements are triggered by the dynamic motion rig allowing for phase averaging at key locations throughout the motion cycle.
Modal characterization of composite flat plate models using piezoelectric transducers
Oliveira, É. L.; Maia, N. M. M.; Marto, A. G.; da Silva, R. G. A.; Afonso, F. J.; Suleman, A.
2016-10-01
This paper aims to estimate the modal parameters of composite flat plate models through Experimental Modal Analysis (EMA) using piezoelectric transducers. The flat plates are composed of three ply carbon-epoxy fibers oriented in the same direction. Five specimens with different unidirectional fiber nominal orientations θk (0o, 30o, 45o, 60o and 90o) were tested. These models were instrumented with one PZT (Lead Zirconate Titanate) actuator and one PVDF (Polyvinylidene Fluoride) sensor and an EMA was performed. The natural frequencies and damping factors estimated using only a single PVDF response were compared with the estimated results using twelve measurement points acquired by laser doppler vibrometry. For comparison purposes, the percentage error of each natural frequency estimation and the percentage error of the damping factor estimations were computed, as well as their averages. Even though the comparison was made between a SISO (Single-Input, Single-Output) and a SIMO (Single-Input, Multiple-Output) techniques, both results are very close. The vibration modes were estimated by means of laser measurements and were used in the modal validation. In order to verify the accuracy of the modal parameters, the Modal Assurance Criterion (MAC) was employed and a high correlation among mode shapes was observed.
A high performance porous flat-plate solar collector
Lansing, F. L.; Clarke, V.; Reynolds, R.
1979-01-01
A solar collector employing a porous matrix as a solar absorber and heat exchanger is presented and its application in solar air heaters is discussed. The collector is composed of a metallic matrix with a porous surface which acts as a large set of cavity radiators; cold air flows through the matrix plate and exchanges heat with the thermally stratified layers of the matrix. A steady-state thermal analysis of the collector is used to determine collector temperature distributions for the cases of an opaque surface matrix with total absorption of solar energy at the surface, and a diathermanous matrix with successive solar energy absorption at each depth. The theoretical performance of the porous flat plate collector is shown to exceed greatly that of a solid flat plate collector using air as the working medium for any given set of operational conditions. An experimental collector constructed using commercially available, low cost steel wool as the matrix has been found to have thermal efficiencies from 73 to 86%.
The Effect of the Configuration of the Absorber on the Performance of Flat Plate Thermal Collector
Yan, Moyu; Qu, Ming; Peng, Steve
2016-01-01
In this study, a numerical thermal analysis for a new designed flat plate thermal collector was conducted through modeling. The new flat plate thermal collector has ellipse shaped tubes inside a wavy shaped absorber, which is made of stainless steel. For the comparison, the conventional flat plate thermal collector with circular copper tubes served as a base case was also modeled. Hottel-Whillier equations were utilized to formulate thermal networks for both models developed in Engineering Eq...
System Advisor Model: Flat Plate Photovoltaic Performance Modeling Validation Report
Energy Technology Data Exchange (ETDEWEB)
Freeman, J.; Whitmore, J.; Kaffine, L.; Blair, N.; Dobos, A. P.
2013-12-01
The System Advisor Model (SAM) is a free software tool that performs detailed analysis of both system performance and system financing for a variety of renewable energy technologies. This report provides detailed validation of the SAM flat plate photovoltaic performance model by comparing SAM-modeled PV system generation data to actual measured production data for nine PV systems ranging from 75 kW to greater than 25 MW in size. The results show strong agreement between SAM predictions and field data, with annualized prediction error below 3% for all fixed tilt cases and below 8% for all one axis tracked cases. The analysis concludes that snow cover and system outages are the primary sources of disagreement, and other deviations resulting from seasonal biases in the irradiation models and one axis tracking issues are discussed in detail.
Wind loads on flat plate photovoltaic array fields (nonsteady winds)
Miller, R. D.; Zimmerman, D. K.
1981-01-01
Techniques to predict the dynamic response and the structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence were analyzed. Guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays are presented. The dynamic response and the loads dynamic magnification factor of the two array configurations are similar. The magnification factors at a mid chord and outer chord location on the array illustrated and at four points on the chord are shown. The wind tunnel test experimental rms pressure coefficient on which magnification factors are based is shown. It is found that the largest response and dynamic magnification factor occur at a mid chord location on an array and near the trailing edge. A technique employing these magnification factors and the wind tunnel test rms fluctuating pressure coefficients to calculate design pressure loads due to wind turbulence is presented.
Validation of CFD simulation for flat plate solar energy collector
Energy Technology Data Exchange (ETDEWEB)
Selmi, Mohamed; Al-Khawaja, Mohammed J.; Marafia, Abdulhamid [Department of Mechanical Engineering, University of Qatar, P.O. Box 2713, Doha, State of Qatar (Qatar)
2008-03-15
The problem of flat plate solar energy collector with water flow is simulated and analyzed using computational fluid dynamics (CFD) software. The considered case includes the CFD modeling of solar irradiation and the modes of mixed convection and radiation heat transfer between tube surface, glass cover, side walls, and insulating base of the collector as well as the mixed convective heat transfer in the circulating water inside the tube and conduction between the base and tube material. The collector performance, after obtaining 3-D temperature distribution over the volume of the body of the collector, was studied with and without circulating water flow. An experimental model was built and experiments were performed to validate the CFD model. The outlet temperature of water is compared with experimental results and there is a good agreement. (author)
Increasing thermal efficiency of solar flat plate collectors
Pona, J.
A study of methods to increase the efficiency of heat transfer in flat plate solar collectors is presented. In order to increase the heat transfer from the absorber plate to the working fluid inside the tubes, turbulent flow was induced by installing baffles within the tubes. The installation of the baffles resulted in a 7 to 12% increase in collector efficiency. Experiments were run on both 1 sq ft and 2 sq ft collectors each fitted with either slotted baffles or tubular baffles. A computer program was run comparing the baffled collector to the standard collector. The results obtained from the computer show that the baffled collectors have a 2.7% increase in life cycle cost (LCC) savings and a 3.6% increase in net cash flow for use in domestic hot water systems, and even greater increases when used in solar heating systems.
Initial stage of flat plate impact onto liquid free surface
Iafrati, Alessandro; Korobkin, Alexander A.
2004-07-01
The liquid flow and the free surface shape during the initial stage of flat plate impact onto liquid half-space are investigated. Method of matched asymptotic expansions is used to derive equations of motion and boundary conditions in the main flow region and in small vicinities of the plate edges. Asymptotic analysis is performed within the ideal and incompressible liquid model. The liquid flow is assumed potential and two dimensional. The ratio of the plate displacement to the plate width plays the role of a small parameter. In the main region the flow is given in the leading order by the pressure-impulse theory. This theory provides the flow field around the plate after a short acoustic stage and predicts unbounded velocity of the liquid at the plate edges. In order to resolve the singular flow caused by the normal impact of a flat plate, the fine pattern of the flow in small vicinities of the plate edges is studied. It is shown that the initial flow close to the plate edges is self-similar in the leading order and is governed by nonlinear boundary-value problem with unknown shape of the free surface. The Kutta conditions are imposed at the plate edges, in order to obtain a nonsingular inner solution. This boundary-value problem is solved numerically by iterations. At each step of iterations the "inner" velocity potential is calculated by the boundary-element method. The asymptotics of the inner solution in both the far field and the jet region are obtained to make the numerical algorithm more efficient. The numerical procedure is carefully verified. Agreement of the computed free surface shape with available experimental data is fairly good. Stability of the numerical solution and its convergence are discussed.
General Observations of the Time-Dependent Flow Field Around Flat Plates in Free Fall
DEFF Research Database (Denmark)
Hærvig, Jakob; Jensen, Anna Lyhne; Pedersen, Marie Cecilie
2015-01-01
The free fall trajectories of flat plates are investigated in order to improve understanding of the forces acting on falling blunt objects. The long term goal is to develop a general applicable model to predict free fall trajectories. Numerically the free fall of a flat plate is investigated usin...
On the rotation and pitching of flat plates
Jin, Yaqing; Ji, Sheng; Chamorro, Leonardo P.
2016-11-01
Wind tunnel experiments were performed to characterize the flow-induced rotation and pitching of various flat plates as a function of the thickness ratio, the location of the axis of rotation and turbulence levels. High-resolution telemetry, laser tachometer, and hotwire were used to get time series of the plates motions and the signature of the wake flow at a specific location. Results show that a minor axis offset can induce high-order modes in the plate rotation under low turbulence due to torque unbalance. The spectral decomposition of the flow velocity in the plate wake reveals the existence of a dominating high-frequency mode that corresponds to a static-like vortex shedding occurring at the maximum plate pitch, where the characteristic length scale is the projected width at maximum pitch. The plate thickness ratio shows inverse relation with the angular velocity. A simple model is derived to explain the linear relation between pitching frequency and wind speed. The spectra of the plate rotation show nonlinear relation with the incoming turbulence, and the dominating role of the generated vortices in the plate motions.
Wind loads on flat plate photovoltaic array fields
Miller, R. D.; Zimmerman, D. K.
1981-01-01
The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads. The arrays located at the outer boundary of an array field have a protective influence on the interior arrays of the field. A significant decrease of the array wind loads were recorded in the wind tunnel test on array panels located behind a fence and/or interior to the array field compared to the arrays on the boundary and unprotected from the wind. The magnitude of this decrease was the same whether caused by a fence or upwind arrays.
Experimental Modal Analysis of a Flat Plate Subjected To Vibration
Directory of Open Access Journals (Sweden)
Owunna Ikechukwu
2016-07-01
Full Text Available Modal analysis is significant in evaluating the mode shapes generated by a component under vibrational excitation, as the mode shapes can be used to determine the displacement or response of the component under the influence vibration in real life application. Result obtained from the modal analysis will generate a number of resonances which the frequency and damping effect can be determined by measurement. However, determining the accuracy of modal analysis result is somewhat difficult as the experimental results and the results generated by Finite Element Analysis (FEA solvers can be affected by a number of factors pointed out in this paper. In this study, a flat plate was mounted on an electromagnetic shaker which enabled the excitation of the plate, while results of the response were measured using a transducer attached to the plate. The plate was also modelled using CATIA software and the files transferred to the different FEA solvers such as HYPERMESH, ANSYS 6 Degree of Freedom (DOF as well as ANSYS 5 degree of freedom, in which the same analysis was carried out to obtain a set of results other than the experimental results. Each FEA solver generated results that were in close proximity with the experimental results, particularly the results generated by ANSYS 5 Degree of freedom. Hence, to ascertain the accuracy of the results obtained from modal analysis experimental procedure, it is important to match up the results generated from different FEA solvers with the experimental results.
Spatially developing turbulent boundary layer on a flat plate
Lee, J H; Hutchins, N; Monty, J P
2012-01-01
This fluid dynamics video submitted to the Gallery of Fluid motion shows a turbulent boundary layer developing under a 5 metre-long flat plate towed through water. A stationary imaging system provides a unique view of the developing boundary layer as it would form over the hull of a ship or fuselage of an aircraft. The towed plate permits visualisation of the zero-pressure-gradient turbulent boundary layer as it develops from the trip to a high Reynolds number state ($Re_\\tau \\approx 3000$). An evolving large-scale coherent structure will appear almost stationary in this frame of reference. The visualisations provide an unique view of the evolution of fundamental processes in the boundary layer (such as interfacial bulging, entrainment, vortical motions, etc.). In the more traditional laboratory frame of reference, in which fluid passes over a stationary body, it is difficult to observe the full evolution and lifetime of turbulent coherent structures. An equivalent experiment in a wind/water-tunnel would requ...
Start-up vortex flow past an accelerated flat plate
Xu, Ling
2014-01-01
Viscous flow past a finite flat plate moving in direction normal to itself is studied numerically.The plate moves with velocity $at^p$, where $p=0,0.5,1,2$. We present the evolution of vorticity profiles, streaklines and streamlines, and study the dependence on the acceleration parameter $p$. Four stages in the vortex evolution, as proposed by Luchini & Tognaccini (2002), are clearly identified. The initial stage, in which the vorticity consists solely of a Rayleigh boundary layer, is shown to last for a time-interval whose length shrinks to zero like $p^3$, as $p \\to 0$. In the second stage, a center of rotation develops near the tip of the plate, well before a vorticity maximum within the vortex core develops. Once the vorticity maximum develops, its position oscillates and differs from the center of rotation. The difference between the two increases with increasing $p$, and decreases in time. In the third stage, the center of rotation and the shed circulation closely satisfy self-similar scaling laws f...
Natural convection characteristics of flat plate collectors. Progress report
Energy Technology Data Exchange (ETDEWEB)
Randall, K.R.; Wl-Wakil, M.M.; Mitchell, J.W.
1977-09-01
The results of an experimental investigation into the convective heat losses in large aspect ratio flat-plate solar collectors are described. An experimental study has been undertaken on a specially designed test cell using a 3 inch Mach-Zehnder interferometer. Air at atmospheric pressure was used as the heat-transfer fluid. The experimental results include interferograms which show the thermal boundary layer formations and the temperature profiles. Local temperature profiles have been analyzed through the use of an optical comparator to determine local Nusselt number profiles, which have, in turn, been integrated to give average heat-transfer results. Angles of inclination from the horizontal of 45, 60, 75 and 90 degrees have been investigated. Aspect ratios from 9 to 36 were examined over a Rayleigh number range of 4,000 to 310,000. Finally, heat-transfer correlations have been developed for the prediction of local Nusselt numbers in the starting and departure corners and for the average heat-transfer results as a function of collector tilt angle.
The High-Frequency Dielectric Properties of Glass Fibre Reinforced Plastic and Honeycomb Layers
1989-06-29
The dielectric constant and the dielectric loss angle tangent of glass fibre reinforced plastic are both relatively small; it is a good wave...practical value. This paper introduces the work we have done in this area. The dielectric properties of glass fibre reinforced plastic have a close
A dynamic performance simulation model of flat-plate solar collectors for a heat pump system
Energy Technology Data Exchange (ETDEWEB)
Arinze, E.A.; Schoenau, G.J.; Sokhansanj, S. (Saskatchewan Univ., Saskatoon, SK (Canada). College of Engineering); Adefila, S.S.; Mumah, S.M. (Ahmadu Bello Univ., Zaria (Nigeria). Dept. of Chemical Engineering)
1993-01-01
Flat-plate collectors are inherently exposed to time-varying meteorological and system parameters. Thus, dynamic modeling, rather than the commonly used steady-state models, is a more accurate approach for the design and performance evaluation of flat-plate solar collectors. The dynamic model presented in this study describes the fluid, plate and cover temperatures of the collector by three different differential equations. Taylor series expansion and the Runge-Kutta method are used in the solution of the differential equations. The accuracy of the dynamic model was tested by comparing the results predicted by the model with experimental performance data obtained for a liquid-cooled flat-plate solar collector with a corrugated transparent fiberglass cover. The predicted results by the dynamic model agreed favorably with the measured experimental data for the flat-plate solar collector. Experimentally determined collector temperatures varied by a maximum of [+-]3[sup o]C from values predicted by the model. (Author)
On the instability of hypersonic flow past a flat plate
Blackaby, Nicholas; Cowley, Stephen; Hall, Philip
1990-01-01
The instability of hypersonic boundary-layer flows over flat plates is considered. The viscosity of the fluid is taken to be governed by Sutherland's law, which gives a much more accurate representation of the temperature dependence of fluid viscosity at hypersonic speeds than Chapman's approximate linear law; although at lower speeds the temperature variation of the mean state is less pronounced so that the Chapman law can be used with some confidence. Attention is focussed on the so-called (vorticity) mode of instability of the viscous hypersonic boundary layer. This is thought to be the fastest growing inviscid disturbance at hypersonic speeds; it is also believed to have an asymptotically larger growth rate than any viscous or centrifugal instability. As a starting point the instability of the hypersonic boundary layer which exists far downstream from the leading edge of the plate is investigated. In this regime the shock that is attached to the leading edge of the plate plays no role, so that the basic boundary layer is non-interactive. It is shown that the vorticity mode of instability of this flow operates on a significantly different lengthscale than that obtained if a Chapman viscosity law is assumed. In particular, it is found that the growth rate predicted by a linear viscosity law overestimates the size of the growth rate by O(M(exp 2). Next, the development of the vorticity mode as the wavenumber decreases is described, and it is shown that acoustic modes emerge when the wavenumber has decreased from it's O(1) initial value to O(M (exp -3/2). Finally, the inviscid instability of the boundary layer near the leading edge in the interaction zone is discussed and particular attention is focussed on the strong interaction region which occurs sufficiently close to the leading edge. It is found that the vorticity mode in this regime is again unstable, and that it is concentrated in the transition layer at the edge of the boundary layer where the temperature
EVALUATION OF FLAT-PLATE PHOTOVOLTAIC THERMAL HYBRID SYSTEMS FOR SOLAR ENERGY UTILIZATION.
Energy Technology Data Exchange (ETDEWEB)
ANDREWS,J.W.
1981-06-01
The technical and economic attractiveness of combined photovoltaic/thermal (PV/T) solar energy collectors was evaluated. The study was limited to flat-plate collectors since concentrating photovoltaic collectors require active cooling and thus are inherently PV/T collectors, the only decision being whether to use the thermal energy or to dump it. it was also specified at the outset that reduction in required roof area was not to be used as an argument for combining the collection of thermal and electrical energy into one module. Three tests of economic viability were identified, all of which PV/T must pass if it is to be considered a promising alternative: PV/T must prove to be competitive with photovoltaic-only, thermal-only, and side-by-side photovoltaic-plus-thermal collectors and systems. These three tests were applied to systems using low-temperature (unglazed) collectors and to systems using medium-temperature (glazed) collectors in Los Angeles, New York, and Tampa. For photovoltaics, the 1986 DOE cost goals were assumed to have been realized, and for thermal energy collection two technologies were considered: a current technology based on metal and glass, and a future technology based on thin-film plastics. The study showed that for medium-temperature applications PV/T is not an attractive option in any of the locations studied. For low-temperature applications, PV/T appears to be marginally attractive.
EVALUATION OF FLAT-PLATE PHOTOVOLTAIC THERMAL HYBRID SYSTEMS FOR SOLAR ENERGY UTILIZATION.
Energy Technology Data Exchange (ETDEWEB)
ANDREWS,J.W.
1981-06-01
The technical and economic attractiveness of combined photovoltaic/thermal (PV/T) solar energy collectors was evaluated. The study was limited to flat-plate collectors since concentrating photovoltaic collectors require active cooling and thus are inherently PV/T collectors, the only decision being whether to use the thermal energy or to dump it. it was also specified at the outset that reduction in required roof area was not to be used as an argument for combining the collection of thermal and electrical energy into one module. Three tests of economic viability were identified, all of which PV/T must pass if it is to be considered a promising alternative: PV/T must prove to be competitive with photovoltaic-only, thermal-only, and side-by-side photovoltaic-plus-thermal collectors and systems. These three tests were applied to systems using low-temperature (unglazed) collectors and to systems using medium-temperature (glazed) collectors in Los Angeles, New York, and Tampa. For photovoltaics, the 1986 DOE cost goals were assumed to have been realized, and for thermal energy collection two technologies were considered: a current technology based on metal and glass, and a future technology based on thin-film plastics. The study showed that for medium-temperature applications PV/T is not an attractive option in any of the locations studied. For low-temperature applications, PV/T appears to be marginally attractive.
Hiroshi Tanaka
2015-01-01
Augmentation of solar radiation absorbed on a flat plate solar thermal collector by a flat plate bottom reflector was numerically determined when there was a gap between the collector and reflector. The inclination of both the collector and reflector was assumed to be adjustable according to the season. A mirror-symmetric plane of the collector to the reflector was introduced, and a graphical model was proposed to calculate the amount of solar radiation reflected by the reflector and then abs...
Research on the Mechanic Performance of Honeycomb Plastic Tire%蜂巢式塑料轮胎力学性能研究
Institute of Scientific and Technical Information of China (English)
王若云; 贺建芸; 丁玉梅; 刘肖英; 杨卫民; 焦志伟
2014-01-01
基于聚氨酯弹性体优异的性能，建立了3种不同密度的蜂巢式塑料轮胎模型，并以ABAQUS软件为工具，以同型号的传统橡胶轮胎为参照，对比分析了稳态滚动工况下轮胎的接地性能和应力分布。分析结果表明，与传统橡胶轮胎相比，蜂巢式塑料轮胎的等效应力分布更加均匀。因此，蜂巢式塑料轮胎局部发生过度磨损的可能性降低。此外，蜂巢式塑料轮胎支撑板的受力情况与蜂巢密度密切相关。%Based on superior performance of polyurethane elastomer,three different density of honeycomb plastic tires models were established,the same model of the traditional rubber tires were taken as reference,and ABAQUS software was used as analysis tool to compare and analyze the grounding performance and stress distribution of the plastic tires under the steady rolling conditions. The results show that the equivalent stresses of honeycomb plastic tires distribute more uniformly than that of the traditional rubber tires. Therefore, the possibility of excessive wear of honeycomb plastic tires gets smaller. In addition, the stress conditions of support plates of the tires are closely related to honeycomb density.
Phenomenological model for torsional galloping of an elastic flat plate due to hydrodynamic loads
Institute of Scientific and Technical Information of China (English)
FERNANDES Antonio Carlos; ARMANDEI Mohammadmehdi
2014-01-01
This study investigates the torsional galloping phenomenon, an instability type flow-induced oscillation, in an elastic stru-cture due to hydrodynamic loads into the water current. The structure applied here is a rectangular flat plate with an elastic axis in its mid-chord length. The elasticity is provided by torsion spring. The flat plate has only one degree of freedom which is rotation in pure yaw about its axis. It is observed that as the current speed is higher than a critical velocity, the flat plate becomes unstable. The instability leads to torsional galloping occurrence, as a result of which the flat plate begins to yaw about the elastic axis. By testing two different chord lengths each with several torsion spring rates, the flat plate behavior is investigated and three different responses are recognized. Then, a phenomenological model is developed with the original kernel in the form of the van der Pol-Duffing equa-tion. The model explains these three responses observed experimentally.
Hollands, K. G. T.; Wright, J. L.
1983-01-01
This paper presents an efficient algorithm for solving the set of nonlinear equations governing the total heat transfer across an arbitrary number of parallel flat plate solar collector covers, each of which can be partly transparent to longwave thermal radiation. The governing equations are sufficiently general to permit each cover to have asymmetric radiative properties and to account for absorption of solar energy on the individual covers. This theory is shown to be in good agreement with the approximate equations of Whillier (provided certain interpretations are placed on his quantities) and with experiments using a plastic inner cover and bounding plates of various emissivities. Using this theory, it is demonstrated that if the absorber plate has a selective surface, an inner cover transparent to long wave radiation is to be preferred over one which is opaque.
The Flat Plate Solar Array Project, focuses on advancing technologies relevant to the design and construction of megawatt level central station systems. Photovoltaic modules and arrays for flat plate central station or other large scale electric power production facilities require the establishment of a technical base that resolves design issues and results in practical and cost effective configurations. Design, qualification and maintenance issues related to central station arrays derived from the engineering and operating experiences of early applications and parallel laboratory reserch activities are investigated. Technical issues are examined from the viewpoint of the utility engineer, architect/engineer and laboratory researcher. Topics on optimum source circuit designs, module insulation design for high system voltages, array safety, structural interface design, measurements, and array operation and maintenance are discussed.
Performance of streamlined bridge decks in relation to the aerodynamics of a flat plate
DEFF Research Database (Denmark)
Larose, Guy; Livesey, Flora M.
1997-01-01
The aerodynamics of three modern bridge decks are compared to the aerodynamics of a 16:1 flat plate. The comparisons are made on the basis of the analytical evaluation of the performance of each cross-section to the buffeting action of the wind. In general, the closed-box girders studied in this ...... in this paper showed buffeting responses similar to a flat plate with the exception of the multi-box girder which performed much better aerodynamically.......The aerodynamics of three modern bridge decks are compared to the aerodynamics of a 16:1 flat plate. The comparisons are made on the basis of the analytical evaluation of the performance of each cross-section to the buffeting action of the wind. In general, the closed-box girders studied...
A diagram for defined solar radiation absorbed per unit area of flat plate solar collectors
Energy Technology Data Exchange (ETDEWEB)
Tekin, Y.; Altuntop, N. [Erciyes University, Dept. of Mechanical Engineering (Turkey); Cengel, Y.A. [Nevada Reno University, Dept. of Mechanical Engineering, NV (United States); Cengel, Y.A. [Nevada University, Dept. Mechanical Engineering, Reno, NV (United States)
2000-07-01
In Erciyes University, the Solar House (28.75 m{sup 2}) is heated from the floor by using flat plate liquid solar collectors. Required solar radiation for heating and heat losses are calculated. In this work, the required calculations for Erciyes Solar House were generalized and required calculation were done to evaluate absorbed solar radiation per unit surface of the flat plate liquid collector. At the end, three generalized diagrams for nine different months are obtained using obtained numerical values. The goal of preparing diagrams is to determine absorbed solar radiation per unit surface area of flat plate liquid collector at any instant at any latitude, In this work, the diagram is explained by means of sample calculations for November. This diagram was prepared to find out absorbed solar radiation per unit area of black surface collector by means obtained equations. With this diagram, all instant solar radiation can be evaluated in 19 steps. (authors)
Interacting wakes of a narrow and a wide flat plate in tandem arrangement
Energy Technology Data Exchange (ETDEWEB)
Hacışevki, H; Teimourian, A, E-mail: hasan.hacisevki@emu.edu.tr [Department of Mechanical Engineering, Eastern Mediterranean University, Mağusa, North Cyprus, Mersin 10 (Turkey)
2016-02-15
Flow structures behind two different sized flat plates in tandem arrangement normal to flow at high Reynolds number have been investigated experimentally. A narrow flat plate, as a control plate, has been placed upstream of a wide plate to investigate the interacting wakes behind the wide flat plate. The near wake downstream of the wide plate has been measured by employing constant-temperature hot wire anemometer, quantitatively. The effects of different width ratio (h/D) range from 0.1 to 1.0 together with gap ratio (g/D) ranging from 0.5 to 2.0 have been probed. It was found that Strouhal number variation is directly proportional to gap ratio between the plates. Moreover, it was observed that turbulent kinetic energy production is mostly contributed by transverse normal turbulent stress and therefore follows the transverse stress pattern rather than the stream wise stress. (paper)
Vairamani, K.; Venkatesh, K. Arun; Mathivanan, N.
2011-01-01
Computing the efficiency of flat-plate collector is vital in solar thermal system testing. This paper presents the design of ZigBee enabled data acquisition system for instantaneous flat-plate collector efficiency calculation. It involves measurement of parameters like inlet and outlet fluid temperatures, ambient temperature and solar radiation intensity. The designed system has a base station and a sensor node. ZigBee wireless communication protocol is used for communication between the base station and the sensor node for wireless data acquisition. The wireless sensor node which is mounted over the collector plate includes the necessary sensors and associated signal-conditioners. An application program has been developed on LabVIEW platform for data acquisition, processing and analysis and is executed in base station PC. Instantaneous flat-plate collector efficiency is computed and reported.
Study on characteristics of double surface VOC emissions from dry flat-plate building materials
Institute of Scientific and Technical Information of China (English)
WANG Xinke; ZHANG Yinping; ZHAO Rongyi
2006-01-01
This paper sets up an analytic model of double surface emission of volatile organic compound (VOC) from dry, flat-plate building materials. Based on it, the influence of factors including air change rate, loading factor of materials in the room, mass diffusion coefficient, partition coefficient, convective mass transfer coefficient, thickness of materials, asymmetric convective flow and initial VOC concentration distribution in the building material on emission is discussed. The conditions for simplifying double surface emission into single surface emission are also discussed. The model is helpful to assess the double surface VOC emission from flat-plate building materials used in indoor furniture and space partition.
A Numerical Study on the Performance of an Open-type Flat-plate Solar Collector
Song, Baoyin; Inaba, Hideo; Horibe, Akihiko
1999-01-01
A set mathematical models was developed for predicting the performance of an open-type flat-plate solar collector, and solved numerically through an implicit difference method. The effects of various parameters on the absorption of solar energy for the collector were investigated. The results showed that the solar energy absorptance of the open-type flat-plate collector was relatively high especially for the region where the weather was humid and hot, and there were an optimum length and an o...
Experimental study on flat plate air solar collector using a thin sand layer
Lati, Moukhtar; Boughali, Slimane; Bouguettaia, Hamza; Mennouche, Djamel; Bechki, Djamel
2016-07-01
A flat plate air solar collector was constructed in the laboratory of New and Renewable Energy in Arid Zones LENREZA, Ouargla University-South East Algeria. The absorber of the flat plate air solar collector was laminated with a thin layer of local sand. This acted as a thermal storage system (packed bed) with a collecting area of 2.15 m2 (0.86 m × 2.5 m). It was noticed that the solar heater integrated with the thermal storage material delivered comparatively higher temperatures; thus, giving a better efficiency than the air heater without the thermal storage system.
Directory of Open Access Journals (Sweden)
R. Sivakumar
2016-07-01
Full Text Available Flat Plate Solar Water Heater (FPSWH is commonly used to harvest solar energy. Solar concentration techniques help to achieve higher temperatures of energy. The aim of this article is to compare the performance of a Fresnel lens glazed Flat Plate Solar Water Heater with Phase Change Material (PCM with that provided with an ordinary glazing. The effect of solar concentration using Fresnel lens on energy storage in PCM and heat gained by water are studied and compared with that having an ordinary glazing. Experiments showed 47% improvements in the heat gained by water.
A figure of merit for selective absorbers in flat plate solar water heaters
CSIR Research Space (South Africa)
Roberts, DE
2013-12-01
Full Text Available We derive from first principles an analytical expression for a figure of merit (FM) for a selective solar absorber in a single glazed flat plate water heater. We first show that the efficiency of a collector with an absorber with absorptance α...
Production of fatty acids and protein by nannochloropsis in flat-plate photobioreactors
Hulatt, Chris J.; Wijffels, René H.; Bolla, Sylvie; Kiron, Viswanath
2017-01-01
Nannochloropsis is an industrially-promising microalga that may be cultivated for alternative sources of nutrition due to its high productivity, protein content and lipid composition. We studied the growth and biochemical profile of Nannochloropsis 211/78 (CCAP) in optimized flat-plate photobioreact
Internal (Annular) and Compressible External (Flat Plate) Turbulent Flow Heat Transfer Correlations.
Energy Technology Data Exchange (ETDEWEB)
Dechant, Lawrence [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Smith, Justin [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2016-01-01
Here we provide a discussion regarding the applicability of a family of traditional heat transfer correlation based models for several (unit level) heat transfer problems associated with flight heat transfer estimates and internal flow heat transfer associated with an experimental simulation design (Dobranich 2014). Variability between semi-empirical free-flight models suggests relative differences for heat transfer coefficients on the order of 10%, while the internal annular flow behavior is larger with differences on the order of 20%. We emphasize that these expressions are strictly valid only for the geometries they have been derived for e.g. the fully developed annular flow or simple external flow problems. Though, the application of flat plate skin friction estimate to cylindrical bodies is a traditional procedure to estimate skin friction and heat transfer, an over-prediction bias is often observed using these approximations for missile type bodies. As a correction for this over-estimate trend, we discuss a simple scaling reduction factor for flat plate turbulent skin friction and heat transfer solutions (correlations) applied to blunt bodies of revolution at zero angle of attack. The method estimates the ratio between axisymmetric and 2-d stagnation point heat transfer skin friction and Stanton number solution expressions for sub-turbulent Reynolds numbers %3C1x10 4 . This factor is assumed to also directly influence the flat plate results applied to the cylindrical portion of the flow and the flat plate correlations are modified by
Analysis of Blasius Equation for Flat-Plate Flow with Infinite Boundary Value
DEFF Research Database (Denmark)
Miansari, M. O.; Miansari, M. E.; Barari, Amin;
2010-01-01
This paper applies the homotopy perturbation method (HPM) to determine the well-known Blasius equation with infinite boundary value for Flat-plate Flow. We study here the possibility of reducing the momentum and continuity equations to ordinary differential equations by a similarity transformatio...
Analytical Solution of Forced-Convective Boundary-Layer Flow over a Flat Plate
DEFF Research Database (Denmark)
Mirgolbabaei, H.; Barari, Amin; Ibsen, Lars Bo
2010-01-01
In this letter, the problem of forced convection heat transfer over a horizontal flat plate is investigated by employing the Adomian Decomposition Method (ADM). The series solution of the nonlinear differential equations governing on the problem is developed. Comparison between results obtained...
Energy Technology Data Exchange (ETDEWEB)
NONE
1998-03-01
The bibliography contains citations concerning the design and thermal efficiency of air and liquid type flat plate solar collectors. Topics include convection characteristics, methods to reduce heat loss, optical coatings, and corrosion prevention. Emphasis is on research and modeling. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)
Energy Technology Data Exchange (ETDEWEB)
NONE
1997-05-01
The bibliography contains citations concerning the design and thermal efficiency of air and liquid type flat plate solar collectors. Topics include convection characteristics, methods to reduce heat loss, optical coatings, and corrosion prevention. Emphasis is on research and modeling. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)
Flat plate solar collector design and performance. Citations from the NTIS data base
Hundemann, A. S.
1980-09-01
Federally funded research on the design and thermal efficiency of air and liquid type flat plate collectors is discussed. Topic areas cover convection characteristics, methods to reduce heat loss, optical coatings, and corrosion control. Emphasis of the bibliography is on basic research studies. This updated bibliography contains 196 citations, 36 of which are new entries to the previous edition.
Three-dimensional flow structures and unsteady forces on pitching and surging revolving flat plates
Percin, M.; Van Oudheusden, B.W.
2015-01-01
Tomographic particle image velocimetry was used to explore the evolution of three-dimensional flow structures of revolving low-aspect-ratio flat plates in combination with force measurements at a Reynolds number of 10,000. Two motion kinematics are compared that result in the same terminal condition
Hasheminejad, S. M.
2016-01-05
A series of flow visualizations were conducted to qualitatively study the development of streamwise counter-rotating vortices over a flat plate induced by triangular patterns at the leading edge of a flat plate. The experiments were carried out for a Reynolds number based on the pattern wavelength (λ) of 3080. The results depict the onset, development and breakdown of the vortical structures within the flat plate boundary layer. Moreover, the effect of one spanwise array of holes with diameter of 0.2λ (=3 mm) was examined. This investigation was done on two different flat plates with holes placed at the location x/λ = 2 downstream of the troughs and peaks. The presence of holes after troughs does not show any significant effect on the vortical structures. However, the plate with holes after peaks noticeably delays the vortex breakdown. In this case, the “mushroom-like” vortices move away from the wall and propagate downstream with stable vortical structures. The vortex growth is halted further downstream but start to tilt aside.
A Didactic Experiment and Model of a Flat-Plate Solar Collector
Gallitto, Aurelio Agliolo; Fiordilino, Emilio
2011-01-01
We report on an experiment performed with a home-made flat-plate solar collector, carried out together with high-school students. To explain the experimental results, we propose a model that describes the heating process of the solar collector. The model accounts quantitatively for the experimental data. We suggest that solar-energy topics should…
Analytical Solution of Forced-Convective Boundary-Layer Flow over a Flat Plate
DEFF Research Database (Denmark)
Mirgolbabaei, H.; Barari, Amin; Ibsen, Lars Bo;
2010-01-01
In this letter, the problem of forced convection heat transfer over a horizontal flat plate is investigated by employing the Adomian Decomposition Method (ADM). The series solution of the nonlinear differential equations governing on the problem is developed. Comparison between results obtained...
Lift Enhancement of a Vortex-Sink Attached to a Flat Plate
Xia, Xi; Mohseni, Kamran
2012-01-01
As observed in natural fliers, stabilized vortices on the surface of an airfoil or wing could provide lift enhancement. Similar concept can be applied in fixed lifting surfaces. Potential flow theory is employed to model lift enhancement by attaching a vortex-sink pair to the top surface of a flat plate in a pseudo-steady flow. Using this flow model, a parametric study on the location of the vortex-sink pair is performed in order to optimize lift enhancement. Lift coefficient calculations are presented for a range of vortex-sink positions, vortex-sink strengths, and flat-plate angles of attack. It is shown that beyond the lift contribution terms due to the vortex-sink strength, lift enhancement could be also achieved by a translating velocity of the vortex-sink in a non-equilibrium position. This vortex-sink velocity term is more pronounced when the vortex-sink is placed close to the top surface of the flat-plate near the leading or the trailing edges of the flat plate. It is concluded that increasing the vor...
Hot-air flat-plate solar collector-design package
1979-01-01
Report contains design data, performance specifications, and drawings for hot-air flat-plate solar-energy collector. Evaluation consists of tests on thermal performance time constance, and incidence angle modifier test. Results are presented in table and graph form and are analyzed in detail.
Three-dimensional flow structures and unsteady forces on pitching and surging revolving flat plates
Percin, M.; Van Oudheusden, B.W.
2015-01-01
Tomographic particle image velocimetry was used to explore the evolution of three-dimensional flow structures of revolving low-aspect-ratio flat plates in combination with force measurements at a Reynolds number of 10,000. Two motion kinematics are compared that result in the same terminal condition
Simulation techniques for spatially evolving instabilities in compressible flow over a flat plate
Wasistho, B.; Geurts, B.J.; Kuerten, J.G.M.
1997-01-01
In this paper we present numerical techniques suitable for a direct numerical simulation in the spatial setting. We demonstrate the application to the simulation of compressible flat plate flow instabilities. We compare second and fourth order accurate spatial discretization schemes in combination w
Hot-air flat-plate solar collector-design package
1979-01-01
Report contains design data, performance specifications, and drawings for hot-air flat-plate solar-energy collector. Evaluation consists of tests on thermal performance time constance, and incidence angle modifier test. Results are presented in table and graph form and are analyzed in detail.
Repair of R/C flat plates failing in punching by vertical studs
Directory of Open Access Journals (Sweden)
Hamed S. Askar
2015-09-01
Test results showed that using the proposed system on repairing damaged flat plates due to punching shear is very efficient. Theoretical results obtained based on the formulas adopted by different codes and from the critical shear crack theory (CSCT, showed a satisfactory agreement with test results.
Craft-Joule Project: Stagnation proof transparently insulated flat plate solar collector (static)
Energy Technology Data Exchange (ETDEWEB)
Oliva, A; Cadafalch, J; Perez-Segarra, C.D. [Universitat Politecnica de Catalunya, Barcelona (Spain)] (and others)
2000-07-01
The STATIC (STAgnation proof Transparently Insulated flat plate Solar Collector) project is a Craft-Joule Project within the framework of the Non Nuclear Energy Programme Joule III coordinated by the Centre Technologic de Transferencia de Calor (CTTC). The core group of SMEs involved in the project has its main economical activity in the field of solar thermal systems at low temperature level (domestic hot water, solar heating, etc.). Beyond this, a large application potential exists for solar heating at medium temperature level (from 80 to 160 Celsius degrees) : industrial process heat, solar cooling and air conditioning, solar drying , distillation and desalination. Three of the four SME proposers are located in Southern Europe and in the Caribean, where a continuos increase of the demand for air conditioning and cooling has been demonstrated in the last years. The recent development of flat plate solar collectors with honeycomb-type transparent insulation cover has shown that this type of collectors can become a low cost alternative to evacuated tube and high concentrating CPC collectors in the medium temperature range from 80 to 160 Celsius degrees. With the expected reduction of collector cost, that forms 30%-50% of total system cost, a decisive break-through of solar thermal systems using heat in the medium temperature range can be achieved. The feasibility and good performance of these solar collectors has been proved in several prototypes. Nevertheless, up to now no commercial products are available. In order to reach this, the following developments of new concepts are necessary and are being carried out within this project: solution of the problem of overheating: development of collector versions for different working temperatures: optimization of the design with the support of high level numerical simulation. Several prototypes of the new solar collectors are being tested. System tests will also be carried or for two test arrays of optimized collector
Hydrodynamics of the interceptor on a 2-D flat plate by CFD and experiments
Institute of Scientific and Technical Information of China (English)
MANSOORI M; FERNANDES A C
2015-01-01
Nowadays, the use of interceptor by both partial and total dynamic lift crafts is quite common. In this article, a lot of evidence is given regarding the effectiveness of interceptor. The interceptor, when placed at the stern region, changes the pressure distribution around the craft. Its presence affects drag force, lifting force and the position of pressure’s center leading to a new trim. This study focuses on hydrodynamic effects of interceptors on a 2-D flat plate based on both computational fluid dynamic (CFD) and experimental approaches. The Reynolds average Navier-Stokes (RANS) equations are used to model the flow around a fixed flat plate with an interceptor at different heights and attack angles. Based on finite volume method and SIMPLE algorithm which uses static structures, this model can be analyzed and the RANS results can be compared with the experimental data obtained in the current channel of the laboratory of waves and current of COPPE/UFRJ (LOC in Portuguese acronym). According to the results, the increase of pressure at the end of the flat plate was proportional to the interceptor height. In addition, the existence of interceptors can significantly increase the lift force coefficient at high angles of attack also proportional to the interceptor height. The presence of interceptor at the end of the flat plate increased both the lift coefficient and the drag coefficient but hydrodynamic drag did not grow as fast as the lift coefficient did. The lift coefficient increased much more. Furthermore, the results showed that the interceptor effectiveness is proportional to the boundary layer thickness at the end of the flat plate. As the interceptor was inside the boundary layer alterations of flow speed led to changes in boundary layer thickness, directly affecting interceptor’s efficiency. Optimum choice of interceptor height had a great effect on its efficiency, and in choosing it the flow speed and length of the boat must be taken into
Energy Technology Data Exchange (ETDEWEB)
None
1983-01-01
The Flat-Plate Solar Array Project, managed by the Jet Propulsion Laboratory for the US Department of Energy, has focused on advancing technologies relevant to the design and construction of megawatt-level central-station systems. Photovoltaic modules and arrays for flat-plate central-station or other large-scale electric power production facilities require the establishment of a technical base that resolves design issues and results in practical and cost-effective configurations. The Central Station Research Forum addressed design, qualification and maintenance issues related to central-station arrays derived from the engineering and operating experiences of early applications and parallel laboratory research activities. Technical issues were examined from the viewpoint of the utility engineer, architect-engineer and laboratory researcher. The forum included presentations on optimum source-circuit designs, module insulation design for high system voltages, array safety, structural interface design, measurements and array operation and maintenance. The Research Forum focused on current capabilities as well as design difficulties requiring additional technological thrusts and/or continued research emphasis. Session topic summaries highlighting major points during group discussions, identifying promising technical approaches or areas of future research, are presented.
Flat plate vs. concentrator solar photovoltaic cells - A manufacturing cost analysis
Granon, L. A.; Coleman, M. G.
1980-01-01
The choice of which photovoltaic system (flat plate or concentrator) to use for utilizing solar cells to generate electricity depends mainly on the cost. A detailed, comparative manufacturing cost analysis of the two types of systems is presented. Several common assumptions, i.e., cell thickness, interest rate, power rate, factory production life, polysilicon cost, and direct labor rate are utilized in this analysis. Process sequences, cost variables, and sensitivity analyses have been studied, and results of the latter show that the most important parameters which determine manufacturing costs are concentration ratio, manufacturing volume, and cell efficiency. The total cost per watt of the flat plate solar cell is $1.45, and that of the concentrator solar cell is $1.85, the higher cost being due to the increased process complexity and material costs.
Influences of the Twisted Strips Insertion on the Performance of Flat Plate Water Solar Collector
Directory of Open Access Journals (Sweden)
Jafar M. Hassan
2015-09-01
Full Text Available In order to enhance the efficiency of flat plate solar water collectors without changing in its original shape and with low additional cost, twisted strips are inserted inside its riser pipes. Three flat plate collectors are used for test. Family of twisted strips are inserted inside each collector risers with different twisted ratios (TR=3,4,5. The collectors are connected in parallel mode (Z-Configuration and are exposed to the same conditions (solar radiation and ambient temperature .The experimental results show that, the highest heat transfer rate occurs at twisted ratio (3 .Consequently, for the same twisted ratio the daily efficiencies for the solar collector at different flow rate used (60,100 and 150 ℓ /hr. were 49 %, 57% and 63% respectively.
Recommendations for the performance rating of flat plate terrestrial photovoltaic solar panels
Treble, F. C.
1976-01-01
A review of recommendations for standardizing the performance rating of flat plate terrestrial solar panels is given to develop an international standard code of practice for performance rating. Required data to characterize the performance of a solar panel are listed. Other items discussed are: (1) basic measurement procedures; (2) performance measurement in natural sunlight and simulated sunlight; (3) standard solar cells; (4) the normal incidence method; (5) global method and (6) definition of peak power.
Simon, F.
1975-01-01
A Soltex flat plate solar collector was tested with a solar simulator for inlet temperatures of 77 to 201 F, flux levels of 240 and 350 Btu/hr-sq ft, a collant flow rate of 10.5 lb/hr sq ft, and incident angles of 0 deg, 41.5 deg, and 65.2 deg. Collector performance is correlated in terms of inlet temperature, flux level, and incident angle.
Energy Technology Data Exchange (ETDEWEB)
None
1983-11-15
A Photovoltaic Metallization Research Forum, under the sponsorship of the Jet Propulsion Laboratory's Flat-Plate Solar Array Project and the US Department of Energy, was held March 16-18, 1983 at Pine Mountain, Georgia. The Forum consisted of five sessions, covering (1) the current status of metallization systems, (2) system design, (3) thick-film metallization, (4) advanced techniques and (5) future metallization challenges. Twenty-three papers were presented.
A DC corona discharge on a flat plate to induce air movement
Magnier, Pierre; Hong, Dunpin; Leroy-Chesneau, Annie; Pouvesle, Jean-Michel; Hureau, Jacques
2007-01-01
International audience; This paper describes a DC surface corona discharge designed to modify the airflow around a flat plate. The electrode configuration consisted of two thin copper layers placed on each side of the plate's attack edge. Discharge optical measurements with a photomultiplier tube indicated that the light emitted by the plasma is pulsating, at a frequency that increases with applied voltage. Moreover, with voltage higher than a threshold value, the electric discharge changes r...
Thermal performance optimization of a flat plate solar air heater using genetic algorithm
Energy Technology Data Exchange (ETDEWEB)
Varun; Siddhartha [Department of Mechanical Engineering, National Institute of Technology, Hamirpur 177 005 (H.P.) (India)
2010-05-15
Thermal performance of solar air heater is low and different techniques are adopted to increase the performance of solar air heaters, such as: fins, artificial roughness etc. In this paper an attempt has been done to optimize the thermal performance of flat plate solar air heater by considering the different system and operating parameters to obtain maximum thermal performance. Thermal performance is obtained for different Reynolds number, emissivity of the plate, tilt angle and number of glass plates by using genetic algorithm. (author)
Flat Plate Wake Velocity Statistics Obtained With Circular And Elliptic Trailing Edges
Rai, Man Mohan
2016-01-01
The near wake of a flat plate with circular and elliptic trailing edges is investigated with data from direct numerical simulations. The plate length and thickness are the same in both cases. The separating boundary layers are turbulent and statistically identical. Therefore the wake is symmetric in the two cases. The emphasis in this study is on a comparison of the wake-distributions of velocity components, normal intensity and fluctuating shear stress obtained in the two cases.
A graphical approach to the efficiency of flat-plate collectors
Selcuk, M. K.
1978-01-01
A nomogram is described which can be used to determine the thermal performance of flat plate solar collectors, resulting in two performance factors: the net absorptance and the net heat loss coefficient. The nomogram takes into account angle of incidence, collector slope, absorber plate design, insulating materials, thicknesses, optical properties of absorbing surfaces and glazing materials, and flow factors. A case example is given to illustrate the use of the nomogram.
A Dynamic Multinode Model for Component-Oriented Thermal Analysis of Flat-Plate Solar Collectors
Reiter, Christoph N.; Christoph Trinkl; Wilfried Zörner; Hanby, Vic I.
2015-01-01
A mathematical model of a flat-plate solar collector was developed on the basis of the physical principles of optics and heat transfer in order to determine collector’s component temperatures as well as collector efficiency. In contrast to many available models, the targeted use of this dynamic model is the detailed, theoretical investigation of the thermal behaviour of newly developed or adjusted collector designs on component level, for example, absorber, casing, or transparent cover. The d...
Semicoarsening and Implicit Smoothers for the Simulation of a Flat Plate at Yaw
2001-05-01
Semicoarsening and Implicit Smoothers for the Simulation of a Flat Plate at Yaw Ruben S. Montero and Ignacio M. Llorente Universidad Complutense , Madrid...yDepartamento de Arquitectura de Computadores y Automatica, Universidad Complutense , 28040 Madrid, Spain zDepartamento de Arquitectura de Computadores...y Automatica, Universidad Complutense , 28040 Madrid, Spain xICASE, Mail Stop 132C, NASA Langley Research Center, Hampton, VA 23681-2199 1
Design and performance of tubular flat-plate solid oxide fuel cell
Energy Technology Data Exchange (ETDEWEB)
Matsushima, T.; Ikeda, D.; Kanagawa, H. [NTT Integrated Information & Energy Systems Labs., Tokyo (Japan)] [and others
1996-12-31
With the growing interest in conserving the environmental conditions, much attention is being paid to Solid Oxide Fuel Cell (SOFC), which has high energy-conversion efficiency. Many organizations have conducted studies on tubular and flat type SOFCs. Nippon Telegraph and Telephone Corporation (NTT) has studied a combined tubular flat-plate SOFC, and already presented the I-V characteristics of a single cell. Here, we report the construction of a stack of this SOFC cell and successful generation tests results.
Tahavvor, Ali Reza
2016-06-01
In the present study artificial neural network and fractal geometry are used to predict frost thickness and density on a cold flat plate having constant surface temperature under forced convection for different ambient conditions. These methods are very applicable in this area because phase changes such as melting and solidification are simulated by conventional methods but frost formation is a most complicated phase change phenomenon consists of coupled heat and mass transfer. Therefore conventional mathematical techniques cannot capture the effects of all parameters on its growth and development because this process influenced by many factors and it is a time dependent process. Therefore, in this work soft computing method such as artificial neural network and fractal geometry are used to do this manner. The databases for modeling are generated from the experimental measurements. First, multilayer perceptron network is used and it is found that the back-propagation algorithm with Levenberg-Marquardt learning rule is the best choice to estimate frost growth properties due to accurate and faster training procedure. Second, fractal geometry based on the Von-Koch curve is used to model frost growth procedure especially in frost thickness and density. Comparison is performed between experimental measurements and soft computing methods. Results show that soft computing methods can be used more efficiently to determine frost properties over a flat plate. Based on the developed models, wide range of frost formation over flat plates can be determined for various conditions.
Tahavvor, Ali Reza
2017-03-01
In the present study artificial neural network and fractal geometry are used to predict frost thickness and density on a cold flat plate having constant surface temperature under forced convection for different ambient conditions. These methods are very applicable in this area because phase changes such as melting and solidification are simulated by conventional methods but frost formation is a most complicated phase change phenomenon consists of coupled heat and mass transfer. Therefore conventional mathematical techniques cannot capture the effects of all parameters on its growth and development because this process influenced by many factors and it is a time dependent process. Therefore, in this work soft computing method such as artificial neural network and fractal geometry are used to do this manner. The databases for modeling are generated from the experimental measurements. First, multilayer perceptron network is used and it is found that the back-propagation algorithm with Levenberg-Marquardt learning rule is the best choice to estimate frost growth properties due to accurate and faster training procedure. Second, fractal geometry based on the Von-Koch curve is used to model frost growth procedure especially in frost thickness and density. Comparison is performed between experimental measurements and soft computing methods. Results show that soft computing methods can be used more efficiently to determine frost properties over a flat plate. Based on the developed models, wide range of frost formation over flat plates can be determined for various conditions.
Performance Study of a Double-Pass Thermoelectric Solar Air Collector with Flat-Plate Reflectors
Lertsatitthanakorn, C.; Rungsiyopas, M.; Therdyothin, A.; Soponronnarit, S.
2012-06-01
In this paper the results of the influence of flat-plate reflectors made of aluminum foil on the performance of a double-pass thermoelectric (TE) solar air collector are presented. The proposed TE solar collector with reflectors was composed of transparent glass, an air gap, an absorber plate, TE modules, a rectangular fin heat sink, and two flat-plate reflectors. The flat-plate reflectors were placed on two sides of the TE solar collector (east and west directions). The TE solar collector was installed on a one-axis sun-tracking system to obtain high solar radiation. Direct and reflected incident solar radiation heats up the absorber plate so that a temperature difference is created across the TE modules to generate a direct current. Only a small part of the absorbed solar radiation is converted to electricity, while the rest increases the temperature of the absorber plate. Ambient air flows through the heat sink located in the lower channel to gain heat. The heated air then flows to the upper channel, where it receives additional heating from the absorber plate. Improvements to the thermal energy and electrical power outputs of the system can be achieved by the use of the double-pass collector system with reflectors and TE technology. It was found that the optimum position of the reflectors is 60°, which gave significantly higher thermal energy and electrical power outputs compared with the TE solar collector without reflectors.
REVIEW ON POROUS AND NON-POROUS FLAT PLATE AIR COLLECTOR WITH MIRROR ENCLOSURE
Directory of Open Access Journals (Sweden)
M. PRADHAPRAJ,
2010-09-01
Full Text Available In solar air heater, flat plat collectors are the best heat transferring devices. But the effectiveness of these collectorsis very low because of lack of technology. Solar assisted heated air is successfully used for drying applications and space heating under controlled conditions. From the solar flat plate air heater the hot air is transferred to a conventional dryer or to the combined heater and drying chamber directly. Hence, solar assisted air heaters arecheaper and reliable. The important factors affecting these systems are the solar radiation, mechanical loading, temperature and leakage. The air heater efficiency depends on the design of the system as well as the construction materials and the assembly. The solar air heating systems has acceptable life span of 15 to 20 years. The addition ofside mirror enclosures is to increase the amount of solar radiation absorption at the collector plate so that the collector increases the yield and operate in a higher temperature range. Therefore with the addition of side mirrors one can able to maximize the output of fixed flat plate collectors. A flat plate air collector will be more efficient if it is made up of porous medium when comparing it with the non porous collectors according to the study. In this paper, the performances of porous and non-porous absorber plates are discussed. Also the possible methods of finding out air leakages and the methodology adopted for the performance and efficiency calculations are also discussed.
Shaw, C. S.; Margason, R. J.
1973-01-01
The induced static pressures due to a highly underexpanded sonic jet ejecting normally from a flat plate into a subsonic crosswind have been investigated. These pressure data have been recorded on the flat plate for a range of nominal jet-to-free-stream dynamic-pressure ratios from 0 to 1000 at free-stream Mach numbers of 0.1, 0.2, 0.4, and 0.6. The static pressure data measured on the flat plate are presented and correlated based upon the Riemann shock geometry in the jet plume. This data correlation improves with increasing free-stream Mach number.
Optimization of a flat plate glass reactor for mass production of Nannochloropsis sp. outdoors.
Richmond, A; Cheng-Wu, Z
2001-02-23
The relationships between areal (g m(-2) per day) and volumetric (g l(-1) per day) productivity of Nannochloropsis sp. as affected by the light-path (ranging from 1.3 to 17.0 cm) of a vertical flat plate glass photobioreactor were elucidated. In general, the shorter the length of the light-path (LP), the smaller the areal volume and the higher the volumetric productivity. The areal productivity in relation to the light-path, in contrast, yielded an optimum curve, the highest areal productivity was obtained in a 10 cm LP reactor, which is regarded, therefore, optimal for mass production of Nannochloropsis. An attempt was made to identify criteria by which to assess the efficiency of a photobioreactor in utilizing strong incident energy. Two basic factors which relate to reactor efficiency and its cost-effectiveness have been defined as (a) the total illuminated surface required to produce a set quantity of product and (b) culture volume required to produce that quantity. As a general guide line, the lower these values are, the more efficient and cost-effective the reactor would be. An interesting feature of this analysis rests with the fact that an open raceways is as effective in productivity per illuminated area as a flat-plate reactor with an optimal light path, both cultivation systems requiring ca. 85 m(2) of illuminated surface to produce 1 kg dry cell mass of Nannochloropsis sp. per day. The difference in light utilization efficiency between the two very different production systems involves three aspects - first, the open raceway requires ca. 6 times greater volume than the 10 cm flat plate reactor to produce the same quantity of cell-mass. Second, the total ground area (i.e. including the ground area between reactors) for the vertical flat plate reactor is less than one half of that occupied by an open raceway, indicating the former is more efficient, photosynthetically, compared with the latter. Finally, the harvested cell density is close to one order of
On the Design of an Optimal Waveform to Maximize Scattering from a Flat Plate and a Cone
2007-11-02
direction. This report examines such a possibility. To simplify the problem, the edge effect and creeping waves are neglected. We first review the general scattering problem of a flat plate and a cone.
Digital Repository Service at National Institute of Oceanography (India)
Murty, T.V.R.
Thermal boundary layer on a continuously moving semi-infinite flat plate in the presence of transverse magnetic field with heat flux has been examined. Similarity solutions have been derived and the resulting equations are integrated numerically...
Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.
2015-01-01
This work describes the development of an improved vacuum compatible flat plate radiometric source used for characterizing and calibrating remote optical sensors, in situ, throughout their testing period. The original flat plate radiometric source was developed for use by the VIIRS instrument during the NPOESS Preparatory Project (NPP). Following this effort, the FPI has had significant upgrades in order to improve both the radiometric throughput and uniformity. Results of the VIIRS testing with the reconfigured FPI are reported and discussed.
Application of the Heat Pipe in Flat-Plate Solar Collectors%热管在平板式太阳能集热器中的应用研究
Institute of Scientific and Technical Information of China (English)
黄婷婷; 杜娜; 卿湛媛; 陈新; 牛宝联
2014-01-01
从集热器结构、传热效率、工艺、优缺点等方面详细介绍了3种常见的热管平板式太阳能集热器，它们包括蜂窝热管平板式、真空玻璃盖板热管平板式、CPC热管平板式太阳能集热器。与普通热管平板式集热器相比，3种改良方式均可降低集热器热损失，有效提高集热效率。通过对不同种类热管平板式太阳能集热器的热管种类、工作温度、结构参数等分析，发现随着温度升高，集热器集热效率下降，以及热管蒸发段长度普遍大于冷凝段长度等现象。%Three common heat pipe flat-plate solar collectors are introduced in details from the con-figuration of the collector such as heat transfer efficiency, crafts, merits, and so on, including the flat plate solar collector of honeycomb and heat pipe(HHCHP), flat plate solar collector of vacuum glass-cover board and heat pipe(HVGHP) and a compound parabolic concentrator heat pipe type solar collector(CPC). Com-pared with common heat pipe flat-plate solar collectors, these three improved programs can reduce heat loss, and effectively improve efficiency of the collector. From the analysis of different heat pipe types, oper-ating temperature, structure parameters, a phenomenon is discovered that whatever which type of heat pipe flat-plate solar collector is, as temperature goes up, the efficiency of the collectors drops and the length of evaporation is longer than the length of condensation.
A SIMILARITY METHOD FOR LAMINAR WAKE OF POWER-LAW FLUID FLOW AROUND A FLAT PLATE
Institute of Scientific and Technical Information of China (English)
Liu Cun-fang; Wang Mei-xia
2003-01-01
Based on the characteristic equation for power-law fluid and the Prandtl boundary layer equation, using the similarity method similar to that of Newtonian fluids, two similarity variables were given and a normal differential equation was derived for the laminar wake of power-law fluid flow produced by a flat plate. And numerical results were obtained. The results show that the power-law index n has evident influence on the velocity distribution in the wake. In the wake, velocity gradient is larger, and the wake is narrower for larger n.
Heat transfer from impinging jets to a flat plate with conical and ring protuberances
Hrycak, P.
1984-01-01
An experimental investigation of heat transfer from round jets, impinging normally on a flat plate with exchangeable, heat transfer enhancing protuberances, has been carried out, and the pertinent literature surveyed, for Reynolds numbers ranging from 14,000 to 67,000, and nozzle diameters from 3.18 to 9.52 mm. The experimental data at the stagnation point indicated laminar flow, and a significant enhancement of heat transfer there, due to the introduction of the spike protuberance; the ring protuberance reduced the local heat flux somewhat. Data have also been correlated by means of dimensional analysis and compared with the conical flow theory.
Stall flutter and nonlinear divergence of a two-dimensional flat plate wing
Dugundji, J.; Aravamudan, K.
1976-01-01
Tests were conducted in a small wind tunnel to study the torsional stall flutter behavior of a two-dimensional flat-plate wing pivoted about the midchord. The nonlinear static divergence equilibrium properties of the wing were well predicted from the measured static moment characteristics. Large amplitude limit cycles ranging from plus or minus 11 degrees to plus or minus 100 degrees were observed. Stall flutter occurred above a critical value of a reduced frequency of about 2. Self-excitation occurred for initial angles of attack between 0 and 8 degrees. Nondimensional harmonic coefficients were extracted from the free transient vibration tests for amplitudes up to 80 degrees.
Evaluation of All-Day-Efficiency for selected flat plate and evacuated tube collectors
1981-01-01
An evaluation of all day efficiency for selected flat plate and evacuated tube collectors is presented. Computations are based on a modified version of the NBSIR 78-1305A procedure for all day efficiency. The ASHMET and NOAA data bases for solar insolation are discussed. Details of the algorithm used to convert total (global) horizontal radiation to the collector tilt plane of the selected sites are given along with tables and graphs which show the results of the tests performed during this evaluation.
Monitoring of a flat plate solar thermal field supplying process heat
Directory of Open Access Journals (Sweden)
Cozzini Marco
2016-01-01
Full Text Available The article reports the performance data of a flat plate collector field installed in Austria and supplying process heat to a meat factory, up to a temperature of about 95 °C. The presented data span an entire year, thereby including seasonal effects and allowing for a full characterization of the system performances. Sensor uncertainty is also discussed in detail. Finally, a bin method analysis of the field efficiency is provided. To this purpose, different operating conditions are concisely represented by the so-called reduced temperature, typically used in solar collector applications.
Merges, V.; Klippel, E.
1983-12-01
A solar plant with 21 sq m of highly efficient flat plate collectors and which requires no electricity is described. Heat transport is provided by saturated steam that condenses in a four cubic meter storage tank. The operation temperature is set by the buffer gas pressure between 100 and 140 C, and an absorption chiller is simulated as a heat consumer. The solar collectors were observed to exhibit high performance. Heat transport and temperature control offered high reliability and the thermal stratification in the tank was satisfactory. The positive result permits the design and construction of larger solar plants following the same technical principles.
DEFF Research Database (Denmark)
Hosseinzadeh, Elham; Taherian, Hessam
2012-01-01
On an average about 40% of world energy is used in residential buildings and the largest energy consumption is allocated to the cooling and air-conditioning systems. So every attempt to economize energy consumption is very valuable. In this research a nocturnal radiative cooling system with flat...... as a guideline to derive the governing equations of a night sky radiator. Then, a cooling loop, including a storage tank, pump, connecting pipes, and a radiator has been studied experimentally. The water is circulated through the unglazed flat-plate radiator having 4 m2 of collector area at night to be cooled...
Koller, Anja Pia; Löwe, Hannes; Schmid, Verena; Mundt, Sabine; Weuster-Botz, Dirk
2017-02-01
Light-dependent growth of microalgae can vary remarkably depending on the cultivation system and microalgal strain. Cell size and the pigmentation of each strain, as well as reactor geometry have a great impact on absorption and scattering behavior within a photobioreactor. In this study, the light-dependent, cell-specific growth kinetics of a novel green algae isolate, Scenedesmus obtusiusculus, was studied in a LED-illuminated flat-plate photobioreactor on a lab-scale (1.8 L, 0.09 m(2) ). First, pH-controlled batch processes were performed with S. obtusiusculus at different constant incident photon flux densities. The best performance was achieved by illuminating S. obtusiusculus with 1400 μmol photons m(-2) s(-1) at the surface of the flat-plate photobioreactor, resulting in the highest biomass concentration (4.95 ± 0.16 gCDW L(-1) within 3.5 d) and the highest specific growth rate (0.22 h(-1) ). The experimental data were used to identify the kinetic parameters of different growth models considering light inhibition for S. obtusiusculus. Light attenuation within the flat-plate photobioreactor was considered by varying light transfer models. Based on the identified kinetic growth model of S. obtusiusculus, an optimum growth rate of 0.22 h(-1) was estimated at a mean integral photon flux density of 1072 μmol photons m(-2) s(-1) with the Beer-Lambert law and 1590 μmol photons m(-2) s(-1) with Schuster's light transfer model in the flat-plate photobioreactor. LED illumination was, thus, increased to keep the identified optimum mean integral photon flux density constant in the batch process assuming Schuster's light transfer model. Compared to the same constant incident photon flux density (1590 μmol photons m(-2) s(-1) ), biomass concentration was up to 24% higher using the lighting profile until a dry cell mass concentration of 14.4 ± 1.4 gCDW L(-1) was reached. Afterward, the biomass concentration remained
A Study of Under-expanded Moist Air Jet Impinging on a Flat Plate
Institute of Scientific and Technical Information of China (English)
Yumiko OTOBE; Shigeru MATSUO; Masanori TANAKA; Hideo KASHIMURA; Heuy-Dong KIM; Toshiaki SETOGUCHI
2005-01-01
When a gas expands through a convergent nozzle in which the ratio of the ambient to the stagnation pressures is higher than that of the critical one, the issuing jet from the nozzle is under-expanded. If a flat plate is placed normal to the jet at a certain distance from the nozzle, a detached shock wave is formed at a region between the nozzle exit and the plate. In general, supersonic moist air jet technologies with non-equilibrium condensation are very often applied to industrial manufacturing processes. In spite of the importance in major characteristics of the supersonic moist air jets impinging to a solid body, its qualitative characteristics are not known satisfactorily. In the present study, the effect of the non-equilibrium condensation on the under-expanded air jet impinging on a vertical flat plate is investigated numerically in the case with non-equilibrium condensation, frequency of oscillation for the flow field becomes larger than that without the non-equilibrium condensation, and amplitudes of static pressure become small compared with those of dry air. Furthermore, the numerical results are compared with experimental ones.
Relaminarization of the boundary layer over a flat plate in shock tube experiments
Hinckel, J. N.; Nagamatsu, H. T.
1986-01-01
The relaminarization of the boundary layer over a flat plate in the shock tube was investigated by using the partially reflected shock wave technique. The flow Mach number was approximately 0.14, which corresponds to the inleft flow Mach number for the first row of vanes in a gas turbine. The thin film platinum heat gauges were used to measure the heat transfer rate and the Stanton number was calculated from the oscilloscope voltage traces. The Reynolds number was varied by changing the operation pressure of the shock tube and the values varied from 2.3 x 10 to the 4th to 5.3 x 10 to the 5th. For a Reynolds number range of 7 x 10 to the 4th to 3.5 x 10 to the 5th, the relaminarization of the boundary layer was observed. This phenomenon is due to the decay of the turbulence level in the flow as the reflected shock wave moves upstream from the flat plate. As the Reynolds number increased, the relaminarization was delayed and the delay was related to the turbulence generated by the reflected shock wave.
Experimental testing of various heat transfer structures in a flat plate thermal energy storage unit
Johnson, Maike; Fiß, Michael; Klemm, Torsten
2016-05-01
For solar process heat applications with steam as the working fluid and varying application parameters, a novel latent heat storage concept has been developed using an adaptation of a flat plate heat exchanger as the storage concept. Since the pressure level in these applications usually does not exceed 30 bar, an adaptation with storage material chambers arranged between heat transfer medium chambers is possible. Phase change materials are used as the storage medium, so that the isothermal evaporation of steam during discharging of the storage is paired with the isothermal solidification of the storage material. Heat transfer structures can be inserted into the chambers to adjust the power level for a given application. By combining the required number of flat plate heat exchanger compartments and inserting the appropriate heat transfer structure, the design can easily be adjusted for the required power level and capacity for a specific application. Within this work, the technical feasibility of this concept is proven. The dependence of the operating characteristics on the geometry of the heat exchanger is identified. A focus is on varying the power density by integrating conductive heat structures in the PCM.
Haney, Michael W.
2015-12-01
The economies-of-scale and enhanced performance of integrated micro-technologies have repeatedly delivered disruptive market impact. Examples range from microelectronics to displays to lighting. However, integrated micro-scale technologies have yet to be applied in a transformational way to solar photovoltaic panels. The recently announced Micro-scale Optimized Solar-cell Arrays with Integrated Concentration (MOSAIC) program aims to create a new paradigm in solar photovoltaic panel technology based on the incorporation of micro-concentrating photo-voltaic (μ-CPV) cells. As depicted in Figure 1, MOSAIC will integrate arrays of micro-optical concentrating elements and micro-scale PV elements to achieve the same aggregated collection area and high conversion efficiency of a conventional (i.e., macro-scale) CPV approach, but with the low profile and mass, and hopefully cost, of a conventional non-concentrated PV panel. The reduced size and weight, and enhanced wiring complexity, of the MOSAIC approach provide the opportunity to access the high-performance/low-cost region between the conventional CPV and flat-plate (1-sun) PV domains shown in Figure 2. Accessing this portion of the graph in Figure 2 will expand the geographic and market reach of flat-plate PV. This talk reviews the motivation and goals for the MOSAIC program. The diversity of the technical approaches to micro-concentration, embedded solar tracking, and hybrid direct/diffuse solar resource collection found in the MOSAIC portfolio of projects will also be highlighted.
Three-Dimensional Stress and Stress Intensity for Tensioned Flat Plates with Edge Cracks
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The stress in the thickness direction is an important factor influencing the fracture behavior of structural members. A stress бy tensioned flat plate with edge cracks is widely used as an analysis model. The stresses бx and бy for the plate model can be acquired from Neuber's solution. However, the solution is applicable only for a perfect plane stress or plane strain state. As a consequence of the thickness of the plate a three-dimensional (3-D) stress state will arise near the crack tip, resulting in a variation of the distribution of бx and бy stresses. A full analysis for the 3-D stress fields for a tensioned flat plate with edge cracks has been therefore carried out. The results show that the 3-D stress field near the crack tip is mainly determined by two factors: the thickness of the plate and the curvature radius at the crack tip. A further analysis has been carried out for the stress intensity near the crack tip. In this paper we give some equations matching to the 3-D stress and stress intensity, which describe precisely the stress state near the crack tip, and which can be applied effectively in engineering analysis.
Development of electromagnetic welding facility of flat plates for nuclear industry
Kumar, Rajesh; Sahoo, Subhanarayan; Sarkar, Biswanath; Shyam, Anurag
2017-04-01
Electromagnetic pulse welding (EMPW) process, one of high speed welding process uses electromagnetic force from discharged current through working coil, which develops a repulsive force between the induced current flowing parallel and in opposite direction. For achieving the successful weldment using this process the design of working coil is the most important factor due to high magnetic field on surface of work piece. In case of high quality flat plate welding factors such as impact velocity, angle of impact standoff distance, thickness of flyer and overlap length have to be chosen carefully. EMPW has wide applications in nuclear industry, automotive industry, aerospace, electrical industries. However formability and weldability still remain major issues. Due to ease in controlling the magnetic field enveloped inside tubes, the EMPW has been widely used for tube welding. In case of flat components control of magnetic field is difficult. Hence the application of EMPW gets restricted. The present work attempts to make a novel contribution by investigating the effect of process parameters on welding quality of flat plates. The work emphasizes the approaches and engineering calculations required to effectively use of actuator in EMPW of flat components.
MHD Boundary Layer Slip Flow and Heat Transfer over a Flat Plate
Institute of Scientific and Technical Information of China (English)
Krishnendu Bhattacharyya; Swati Mukhopadhyay; G.C.Layek
2011-01-01
An analysis of magnetohydrodynamic (MHD) boundary layer flow and heat transfer over a flat plate with slip condition at the boundary is presented. A complete self-similar set of equations are obtained from the governing equations using similarity transformations and are solved by a shooting method. In the boundary slip condition no local similarity occurs. Velocity and temperature distributions within the boundary layer are presented. Our analysis reveals that the increase of magnetic and slip parameters reduce the boundary layer thickness and also enhance the heat transfer from the plate.%@@ An analysis of magnetohydrodynamic (MHD) boundary layer flow and heat transfer over a flat plate with slip condition at the boundary is presented.A complete self-similar set of equations are obtained from the governing equations using similarity transformations and are solved by a shooting method.In the boundary slip condition no local similarity occurs.Velocity and temperature distributions within the boundary layer are presented.Our analysis reveals that the increase of magnetic and slip parameters reduce the boundary layer thickness and also enhance the heat transfer from the plate.
Flat-plate solar-collector performance data base and user's manual
Kirkpatrick, D. L.; Kolar, W. A.
1983-07-01
The reader is provided with a thorough understanding on the type of collector thermal performance information which is required in active system design and analysis. Thermal performance test data on 109 commercially available solar collectors which were evaluated in a single, uniform test program, the Interim Solar Collector Test (ISCT) Program are given. In addition to recounting the ISCT program and its results, the an introduction is given on the engineering and physics of a flat-plate solar collector operation. A step-by-step analysis of heat gains and losses is provided to help the reader understand both the source and applicability of the parameters used to describe collector thermal performance. A brief description of the engineering basis for the ASHRAE Standard 93-77 test procedure and the method are included. To demonstrate the sensitivity to variations of collector performance parameters of the annual output of representative solar heating systems, three sets of F-Chart (4.0) system performance predictions are given. Finally, a sensitivity analysis study is presented which considers the heat loss and optical gain parameters of flat-plate collectors, in terms of how they affect the overall solar heating system solar fraction.
Directory of Open Access Journals (Sweden)
Hiroshi Tanaka
2015-11-01
Full Text Available Augmentation of solar radiation absorbed on a flat plate solar thermal collector by a flat plate bottom reflector was numerically determined when there was a gap between the collector and reflector. The inclination of both the collector and reflector was assumed to be adjustable according to the season. A mirror-symmetric plane of the collector to the reflector was introduced, and a graphical model was proposed to calculate the amount of solar radiation reflected by the reflector and then absorbed on the collector. The performance was analyzed for three typical days at a latitude of 30°N. Solar radiation absorbed on the collector can be increased by the bottom reflector even if there is a gap between the collector and reflector. The optimum inclinations of both the collector and reflector are almost the same while the gap length is less than the lengths of the collector and reflector. However, the range of inclination of the reflector that can increase the solar radiation absorbed on the collector decreases with an increase in gap length, and the solar radiation absorbed on the collector rapidly decreased with an increase in the gap length when the reflector and/or collector were not set at a proper angle.
Directory of Open Access Journals (Sweden)
Mohamed Hassan
2017-03-01
Full Text Available Flat plates are favor structure systems usually used in parking garages and high-rise buildings due to its simplicity for construction. However, flat plates have some inherent structural problems, due to high shear stress surrounding the supporting columns which cause a catastrophic brittle type of failure called "Punching Shear Failure". Several solutions are used to avoid punching shear failure, including the use of drop panels or punching shear reinforcement. The latter is being a more sophisticated solution from the structural ductility, the architectural and the economical point of view. This study aims at investigating the effect of stirrups as shear reinforcement in enhancing the punching strength of interior slab-column connections. A total of four full-scale interior slab-column connections were tested up to failure. All slabs had a side length of 1700 mm and 160 mm thickness with 200 mm x 200 mm square column. The test parameters were the presence of shear reinforcement and stirrups concentration around the supporting column. The test results showed that the distribution of stirrups over the critical punching shear zone was an efficient solution to enhance not only the punching shear capacity but also the ductility of the connection. Furthermore, the concentrating of stirrups shear reinforcement in the vicinity of the column for the tested slabs increases the punching shear capacity by 13 % compared to the uniform distribution at same amount of shear reinforcement.
Edwards, D. K.; Rhee, S. J.
1984-05-01
An analysis is presented comparing Teflon film with glass for the inner glazing of a double-glazed selective-black, flat-plate solar collector. The effect of spacing between glazings and between the inner glazing and absorber plate is examined. It is shown that a 12.5-micron Teflon film is superior to glass for the inner glazing of a selective-black collector, because the advantage of its high solar transparency overwhelms the disadvantage of its infrared transparency. A too-small spacing between a selective-black absorber and its inner cover short-circuits the desirable thermal radiation resistance offered by a selective-black absorber plate. Account is taken of spectral variations in the radiation properties of glass, Teflon, and the absorber plate. Allowance is made for the fact that critical Rayleigh number is lower for a plastic film inner glazing than for a glass one.
Schwarz, Mark A.; Kent, Craig J.; Bousquet, Robert; Brown, Steven W.
2016-09-01
In this work, we describe an improved thermal-vacuum compatible flat plate radiometric source which has been developed and utilized for the characterization and calibration of remote optical sensors. This source is unique in that it can be used in situ, in both ambient and thermal-vacuum environments, allowing it to follow the sensor throughout its testing cycle. The performance of the original flat plate radiometric source was presented at the 2009 SPIE1. Following the original efforts, design upgrades were incorporated into the source to improve both radiometric throughput and uniformity. The pre-thermal-vacuum (pre-TVAC) testing results of a spacecraft-level optical sensor with the improved flat plate illumination source, both in ambient and vacuum environments, are presented. We also briefly discuss potential FPI configuration changes in order to improve its radiometric performance. Keywords: Calibration, radiometry, remote sensing, source.
Institute of Scientific and Technical Information of China (English)
Zhongmin WAN; Wei LIU; Zhaoqing ZHENG; A. Nakayama
2007-01-01
An overall two-dimensional numerical model of the miniature flat plate capillary pumped loop (CPL) evaporator is developed to describe the liquid and vapor flow, heat transfer and phase change in the porous wick structure,liquid flow and heat transfer in the compensation cavity and heat transfer in the vapor grooves and metallic wall.The entire evaporator is solved with SIMPLE algorithm as a conjugate problem. The effect of heat conduction of metallic side wall on the performance of miniature flat plate CPL evaporator is analyzed, and side wall effect heat transfer limit is introduced to estimate the performance of evaporator. The shape and location of vapor-liquid interface inside the wick are calculated and the influences of applied heat flux, liquid subcooling, wick material and metallic wall material on the evaporator performance are investigated in detail. The numerical results obtained are useful for the miniature flat plate evaporator performance optimization and design of CPL.
DSMC simulations of leading edge flat-plate boundary layer flows at high Mach number
Pradhan, Sahadev, , Dr.
2017-01-01
The flow over a 2D leading-edge flat plate is studied at Mach number Ma = (Uinf /√{kBTinf / m }) in the range Boltzmann constant. The variation of streamwise velocity, temperature, number-density, and mean free path along the wall normal direction away from the plate surface is studied. The qualitative nature of the streamwise velocity at high Mach number is similar to those in the incompressible limit (parabolic profile). However, there are important differences. The amplitudes of the streamwise velocity increase as the Mach number increases and turned into a more flatter profile near the wall. There is significant velocity and temperature slip at the surface of the plate, and the slip increases as the Mach number is increased. It is interesting to note that for the highest Mach numbers considered here, the streamwise velocity at the wall exceeds the sound speed, and the flow is supersonic throughout the flow domain.
Numerical analysis on thermal hydraulic performance of a flat plate heat pipe with wick column
Lu, Longsheng; Liao, Huosheng; Liu, Xiaokang; Tang, Yong
2015-08-01
A simplified thermal hydraulic model is developed to investigate the influence of wick column on the performance of a flat plate heat pipe (FPHP). The governing equations of the FPHP are solved by using the computational fluid dynamics package FLUENT. The temperature, velocity and pressure fields are obtained. The validity of the model is confirmed by comparing the present solutions with the open literature data. The numerical results show that with the increase of the wick column size, the maximum velocity of the liquid and vapor decreases while the total thermal resistance and capillary heat transfer limit of the FPHP increases gradually. The performance of the FPHP may degrade if the wick column is placed inside the vapor core asymmetrically.
Analytical and Numerical Solutions of Vapor Flow in a Flat Plate Heat Pipe
Directory of Open Access Journals (Sweden)
Mohsen GOODARZI
2012-03-01
Full Text Available In this paper, the optimal homotopy analysis method (OHAM and differential transform method (DTM were applied to solve the problem of 2D vapor flow in flat plate heat pipes. The governing partial differential equations for this problem were reduced to a non-linear ordinary differential equation, and then non-dimensional velocity profiles and axial pressure distributions along the entire length of the heat pipe were obtained using homotopy analysis, differential transform, and numerical fourth-order Runge-Kutta methods. The reliability of the two analytical methods was examined by comparing the analytical results with numerical ones. A brief discussion about the advantages of the two applied analytical methods relative to each other is presented. Furthermore, the effects of the Reynolds number and the ratio of condenser to evaporator lengths on the flow variables were discussed.Graphical abstract
Slip effects on MHD flow and heat transfer of ferrofluids over a moving flat plate
Ramli, Norshafira; Ahmad, Syakila; Pop, Ioan
2017-08-01
In this study, the problem of MHD flow and heat transfer of ferrofluids over a moving flat plate with slip effect and uniform heat flux is considered. The governing ordinary differential equations are solved via shooting method. The effect of slip parameter on the dimensionless velocity, temperature, skin friction and Nusselt numbers are numerically studied for the three selected ferroparticles; magnetite (Fe3O4), cobalt ferrite (CoFe2O4) and Mn-Zn ferrite (Mn-ZnFe2O4) with water-based fluid. The results indicate that dual solutions exist for a plate moving towards the origin. It is found that the slip process delays the boundary layer separation. Moreover, the velocity and thermal boundary-layer thicknesses decrease in the first solution while increase with the increase of the value of slip parameters in second solution.
Simulation and Experimental Investigation of Thermal Performance of a Miniature Flat Plate Heat Pipe
Directory of Open Access Journals (Sweden)
R. Boukhanouf
2013-01-01
Full Text Available This paper presents the results of a CFD analysis and experimental tests of two identical miniature flat plate heat pipes (FPHP using sintered and screen mesh wicks and a comparative analysis and measurement of two solid copper base plates 1 mm and 3 mm thick. It was shown that the design of the miniature FPHP with sintered wick would achieve the specific temperature gradients threshold for heat dissipation rates of up to 80 W. The experimental results also revealed that for localised heat sources of up to 40 W, a solid copper base plate 3 mm thick would have comparable heat transfer performances to that of the sintered wick FPHP. In addition, a marginal effect on the thermal performance of the sintered wick FPHP was recorded when its orientation was held at 0°, 90°, and 180° and for heat dissipation rates ranging from 0 to 100 W.
Experimental and numerical investigation of a flat-plate solar collector
Energy Technology Data Exchange (ETDEWEB)
Alvarez, A. [Departamento de Construcciones Navales, E.U. Politecnica, Universidade da Coruna, 15405 Ferrol (Spain); Cabeza, O. [Departamento de Fisica, Universidade da Coruna, 15072 A Coruna (Spain); Muniz, M.C. [Departamento de Matematica Aplicada, Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain); Varela, L.M. [Departamento de Fisica de la Materia Condensada, Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain)
2010-09-15
In the present paper we present an experimental analysis and a thermal and hydrodynamic modelling of a newly designed flat-plate solar collector characterized by its corrugated channel and by the high surface area directly in contact with the heat transport fluid. The thermal and hydrodynamic modelling of the collector has been performed by means of the Finite Element Method (FEM), validated with analytical results for a well-known fin-and-tube type solar collector. The thermodynamic efficiency of the collector is analyzed by means of its experimental heating curves. The yield of the new collector has been compared to a previously existing commercial collector of related geometry but with less area in direct contact with the heat transport fluid. The experimental results are seen to adequately fit the simulation predictions, and a methodology to use in order to compute the parameters characterizing the thermal behavior of the collector is introduced. (author)
Boundary Layer Flow and Heat Transfer of FMWCNT/Water Nanofluids over a Flat Plate
Directory of Open Access Journals (Sweden)
Mohammad Reza Safaei
2016-09-01
Full Text Available In the present study, the heat transfer and flow of water/FMWCNT (functionalized multi-walled carbon nanotube nanofluids over a flat plate was investigated using a finite volume method. Simulations were performed for velocity ranging from 0.17 mm/s to 1.7 mm/s under laminar regime and nanotube concentrations up to 0.2%. The 2-D governing equations were solved using an in-house FORTRAN code. For a specific free stream velocity, the presented results showed that increasing the weight percentage of nanotubes increased the Nusselt number. However, an increase in the solid weight percentage had a negligible effect on the wall shear stress. The results also indicated that increasing the free stream velocity for all cases leads to thinner boundary layer thickness, while increasing the FMWCNT concentration causes an increase in the boundary layer thickness.
Flat plate heat transfer for laminar transition and turbulent boundary layers using a shock tube
Brostmeyer, J. D.; Nagamatsu, H. T.
1984-01-01
Heat transfer results are presented for laminar, transition, and turbulent boundary layers for a Mach number of 0.12 with gas temperatures of 425 K and 1000 K over a flat plate at room temperature. The measurements were made in air for a Reynolds number range of 600 to 6 million. The heat transfer measurements were conducted in a 70-ft long, 4 in. diameter shock tube. Reflecting wedges were used to reflect the incident shock wave to produce a flow Mach number of 0.12 behind the reflected shock wave. Thin film platinum heat gages were mounted on the plate surface to measure the local heat flux. The laminar results for gas temperatures of 425 K to 1000 K agree well with theory. The turbulent results are also close to incompressible theory, with the 1000 K flow case being slightly higher. The transition results lie between the laminar and turbulent predictions.
Oki, Sae; Suzuki, Ryosuke O.
2016-09-01
The performance of a flat-plate thermoelectric (TE) module consisting of square truncated pyramid elements is simulated using commercial software and original TE programs. Assuming that the temperatures of both the hot and cold surfaces are constant, the performance can be varied by changing the element shape and element alignment pattern. When the angle between the edge and the base is 85° and the small square surfaces of all n-type element faces are connected to the low-temperature surface, the efficiency becomes the largest among all the 17 examined shapes and patterns. By changing the shape to match the temperature distribution, the performance of the TE module is maximized.
Flat-plate techniques for measuring reflectance of macro-algae (Ulva curvata)
Ramsey, Elijah W.; Rangoonwala, Amina; Thomsen, Mads Solgaard; Schwarzschild, Arthur
2012-01-01
We tested the consistency and accuracy of flat-plate spectral measurements (400–1000 nm) of the marine macrophyte Ulva curvata. With sequential addition of Ulva thallus layers, the reflectance progressively increased from 6% to 9% with six thalli in the visible (VIS) and from 5% to 19% with ten thalli in the near infrared (NIR). This progressive increase was simulated by a mathematical calculation based on an Ulva thallus diffuse reflectance weighted by a transmittance power series. Experimental and simulated reflectance differences that were particularly high in the NIR most likely resulted from residual water and layering structure unevenness in the experimental progression. High spectral overlap existed between fouled and non-fouled Ulva mats and the coexistent lagoon mud in the VIS, whereas in the NIR, spectral contrast was retained but substantially dampened by fouling.
Near Continuum Velocity and Temperature Coupled Compressible Boundary Layer Flow over a Flat Plate
He, Xin; Cai, Chunpei
2017-04-01
The problem of a compressible gas flows over a flat plate with the velocity-slip and temperature-jump boundary conditions are being studied. The standard single- shooting method is applied to obtain the exact solutions for velocity and temperature profiles when the momentum and energy equations are weakly coupled. A double-shooting method is applied if these two equations are closely coupled. If the temperature affects the velocity directly, more significant velocity slip happens at locations closer to the plate's leading edge, and inflections on the velocity profiles appear, indicating flows may become unstable. As a consequence, the temperature-jump and velocity-slip boundary conditions may trigger earlier flow transitions from a laminar to a turbulent flow state.
Fixed flat plate collector with a reversible vee-trough concentrator
Selcuk, M. K.
1976-01-01
An asymmetrical-reversible vee-trough concentrator for use both with nonevacuated and evacuated receivers is proposed in order to improve the performance of a fixed flat plate collector. The device is capable of maintaining a year-round concentration factor of about 2 while eliminating the complications of the tilt adjustments of the collector box assembly. Efficiency improvements and cost reductions for temperatures of about 100 and 200 C are offered for the nonvacuum and vacuum tube versions, respectively. A major advantage of the vee-trough is the enhancement of the incident flux, thus extending the collection period. The vacuum collector is suitable for supplying heat to solar Rankine systems, while the nonvacuum version can be used for air conditioning purposes via an absorption air conditioner.
Wake interference behind two flat plates normal to the flow - A finite-element study
Behr, M.; Tezduyar, T. E.; Higuchi, H.
1991-01-01
A finite-element model of the Navier-Stokes equations is used for numerical simulation of flow past two normal flat plates arranged side by side at Reynolds number 80 and 160. The results from this simulation indicate that when the gap between the plates is twice the width of a single plate, the individual wakes of the plates behave independently, with the antiphase vortex shedding being dominant. At smaller gap sizes, the in-phase vortex shedding, with strong wake interaction, is favored. The gap flow in those cases becomes biased, with one of the wakes engulfing the other. The direction of the biased flow was found to be switching at irregular intervals, with the time histories of the indicative flow parameters and their power spectra resembling those of a chaotic system.
Comparison of DAC and MONACO DSMC Codes with Flat Plate Simulation
Padilla, Jose F.
2010-01-01
Various implementations of the direct simulation Monte Carlo (DSMC) method exist in academia, government and industry. By comparing implementations, deficiencies and merits of each can be discovered. This document reports comparisons between DSMC Analysis Code (DAC) and MONACO. DAC is NASA's standard DSMC production code and MONACO is a research DSMC code developed in academia. These codes have various differences; in particular, they employ distinct computational grid definitions. In this study, DAC and MONACO are compared by having each simulate a blunted flat plate wind tunnel test, using an identical volume mesh. Simulation expense and DSMC metrics are compared. In addition, flow results are compared with available laboratory data. Overall, this study revealed that both codes, excluding grid adaptation, performed similarly. For parallel processing, DAC was generally more efficient. As expected, code accuracy was mainly dependent on physical models employed.
Characterizing a burst leading-edge vortex on a rotating flat plate wing
Jones, Anya R.; Medina, Albert; Spooner, Hannah; Mulleners, Karen
2016-04-01
Identifying, characterizing, and tracking incoherent vortices in highly separated flows is of interest for the development of new low-order models for unsteady lift prediction. The current work examines several methods to identify vortex burst and characterize a burst leading-edge vortex. Time-resolved stereoscopic PIV was performed on a rotating flat plate wing at Re = 2500. The burst process was found to occur at mid-span and is characterized by axial flow reversal, the entrainment of opposite-sign vorticity, and a rapid expansion of vortex size. A POD analysis revealed that variations in certain mode coefficients are indicative of the flow state changes characteristics of burst. During burst, the leading-edge vortex evolves to a region of inhomogeneous vorticity distributed over a large area. Several methods of defining the vortex size and circulation are evaluated and a combination of these can be used to characterize the leading-edge vortex both pre- and post-burst.
Coherent Structures in Transition of a Flat-Plate Boundary Layer at Ma=0.7
Institute of Scientific and Technical Information of China (English)
ZHOU Ying; LI Xin-Liang; FU De-Xun; MA Yan-Wen
2007-01-01
@@ Direct numerical simulation (DNS) of a spatially evolving flat-plate boundary layer transition process at free stream Mach number 0.7 is performed. Tollmien-Schlichting (T-S) waves are added on the inlet boundary as the disturbances before transition. Typical coherent structures in the transition process are investigated based on the second invariant of velocity gradient tensor. The instantaneous shear stress and the mean velocity profile in the transition region are studied. In our view, the fact that the peak value of shear stress in the stress concentration area increases and exceeds a threshold value during the later stage of the transition process plays an important role in the laminar breakdown process.
MHD Natural Convection with Convective Surface Boundary Condition over a Flat Plate
Directory of Open Access Journals (Sweden)
Mohammad M. Rashidi
2014-01-01
Full Text Available We apply the one parameter continuous group method to investigate similarity solutions of magnetohydrodynamic (MHD heat and mass transfer flow of a steady viscous incompressible fluid over a flat plate. By using the one parameter group method, similarity transformations and corresponding similarity representations are presented. A convective boundary condition is applied instead of the usual boundary conditions of constant surface temperature or constant heat flux. In addition it is assumed that viscosity, thermal conductivity, and concentration diffusivity vary linearly. Our study indicates that a similarity solution is possible if the convective heat transfer related to the hot fluid on the lower surface of the plate is directly proportional to (x--1/2 where x- is the distance from the leading edge of the solid surface. Numerical solutions of the ordinary differential equations are obtained by the Keller Box method for different values of the controlling parameters associated with the problem.
Multi-objective genetic algorithm for the optimization of a flat-plate solar thermal collector.
Mayer, Alexandre; Gaouyat, Lucie; Nicolay, Delphine; Carletti, Timoteo; Deparis, Olivier
2014-10-20
We present a multi-objective genetic algorithm we developed for the optimization of a flat-plate solar thermal collector. This collector consists of a waffle-shaped Al substrate with NiCrOx cermet and SnO(2) anti-reflection conformal coatings. Optimal geometrical parameters are determined in order to (i) maximize the solar absorptance α and (ii) minimize the thermal emittance ε. The multi-objective genetic algorithm eventually provides a whole set of Pareto-optimal solutions for the optimization of α and ε, which turn out to be competitive with record values found in the literature. In particular, a solution that enables α = 97.8% and ε = 4.8% was found.
Waksman, D.; Thomas, W. C.
1984-12-01
The results of studies, by the National Bureau of Standards, of the reliability and durability of eight different types of flat plate solar collectors representative of equipment available in 1977 are reported. The installations were made in four sites believed to typify various U.S. climates. The stability of the thermal performance and material properties was tracked, and measured again after moving the units inside for exposure to artificial sunlight. The stagnation measurement techniques employed to evaluate the collectors were judged adequate, provided the tests are made on-site and out of doors. It is noted that the instrumentation used to gather sufficient data for valid analyses may experience performance decrements due to the necessarily long monitoring intervals, i.e., several years.
Exergy efficiency analysis of a flat plate solar collector using graphene based nanofluid
Said, Z.; Alim, M. A.; Janajreh, Isam
2015-10-01
The thermal efficiency of a flat plate solar thermal collector is largely affected by the thermal conductivity of the fluid used. In this paper, we theoretically analyzed the heat transfer performance, the entropy generation rate, and the exergy efficiency of the two different graphene based nanofluids (graphene/Acetone and graphene/water). From the analyses, it is revealed that by inserting a small amount of graphene nanoparticles in water, exergy efficiency could be enhanced by 21%, comparing to conventional fluids and entropy generation is decreased by 4%. However, the graphene/water nanofluid shows a lower entropy generation. This characteristic suggests that graphene/water nanofluid is a better candidate for flat solar thermal application.
Potential of size reduction of flat-plate solar collectors when applying MWCNT nanofluid
Faizal, M.; Saidur, R.; Mekhilef, S.
2013-06-01
Flat-plate solar collector is the most popular type of collector for hot water system to replace gas or electric heater. Solar thermal energy source is clean and infinite to replace fossil fuel source that is declining and harmful to the environment. However, current solar technology is still expensive, low in efficiency and takes up a lot of space. One effective way to increase the efficiency is by applying high conductivity fluid as nanofluid. This paper analyzes the potential of size reduction of solar collector when MWCNT nanofluid is used as absorbing medium. The analysis is based on different mass flow rate, nanoparticles mass fraction, and presence of surfactant in the fluid. For the same output temperature, it can be observed that the collector's size can be reduced up to 37% of its original size when applying MWCNT nanofluid as the working fluid and thus can reduce the overall cost of the system.
Direct numerical simulation of laminar-turbulent flow over a flat plate at hypersonic flow speeds
Egorov, I. V.; Novikov, A. V.
2016-06-01
A method for direct numerical simulation of a laminar-turbulent flow around bodies at hypersonic flow speeds is proposed. The simulation is performed by solving the full three-dimensional unsteady Navier-Stokes equations. The method of calculation is oriented to application of supercomputers and is based on implicit monotonic approximation schemes and a modified Newton-Raphson method for solving nonlinear difference equations. By this method, the development of three-dimensional perturbations in the boundary layer over a flat plate and in a near-wall flow in a compression corner is studied at the Mach numbers of the free-stream of M = 5.37. In addition to pulsation characteristic, distributions of the mean coefficients of the viscous flow in the transient section of the streamlined surface are obtained, which enables one to determine the beginning of the laminar-turbulent transition and estimate the characteristics of the turbulent flow in the boundary layer.
Xiao, Lan; Wu, Shuang-Ying; Zhang, Qiao-Ling; Li, You-Rong
2012-07-01
Based on the heat transfer characteristics of absorber plate and the heat transfer effectiveness-number of heat transfer unit method of heat exchanger, a new theoretical method of analyzing the thermal performance of heat pipe flat plate solar collector with cross flow heat exchanger has been put forward and validated by comparisons with the experimental and numerical results in pre-existing literature. The proposed theoretical method can be used to analyze and discuss the influence of relevant parameters on the thermal performance of heat pipe flat plate solar collector.
Batubara, Fatimah; Misran, Erni; Dina, Sari Farah; Heppy
2017-06-01
Research on potato drying using the indirect solar dryer with flat-plate finned collector and forced convection has been done. The research was conducted at the outdoor field of Laboratory of Institute for Research and Standardization of Industry on June 14th-23rd, 2016 from 9:00 am to 4:00 pm. This research aims to obtain the drying kinetics model of potato (Solanumtuberosum L.) using an indirect solar dryer's (ISD) with flat plate-finned collector and forced convection. The result will be compared to the open sun drying (OSD) method. Weather conditions during the drying process took place as follows; surrounding air temperature was in the range 27 to 34.7 °C, relative humidity (RH) 29.5 to 61.0% and the intensity of solar radiation 105.6 to 863.1 Watt/m2. The dried potato thicknesses were 1.0 cm, 1.5 cm and 2.0 cm, with the average initial water content of 76.46%. The average temperature in the collector chamber ranged from 42.2 to 57.4 °C and the drying chamber was at 46.2 °C. The best drying result was obtained from a sample size of 1 cm thickness using the IDS method with an average drying rate of 0.018 kg H2O per kg dry-weight.hour and the water content was constant at 5.02% in 21 hours of drying time. The most suitable kinetics model is Page model, equation MR = exp (-0.049 t1,336) for 1.0 cm thickness, exp (-0.066 t1,222) for 1.5 cm thickness and exp (-0.049 t1,221) for 2.0 cm thickness. The quality of potato drying using ISD method is better than using OSD which can be seen from the color produced.
Sensitivity analysis of thermal performances of flat plate solar air heaters
Njomo, Donatien; Daguenet, Michel
2006-10-01
Sensitivity analysis is a mathematical tool, first developed for optimization methods, which aim is to characterize a system response through the variations of its output parameters following modifications imposed on the input parameters of the system. Such an analysis may quickly become laborious when the thermal model under consideration is complex or the number of input parameters is high. In this paper, we develop a mathematical model to analyse the heat exchanges in four different types of solar air collectors. When building this thermal model we show that for each collector, at quasi-steady state, the energy balance equations of the components of the collector cascade into a single first-order non-linear differential equation that is able to predict the thermal behaviour of the collector. Our heat transfer model clearly demonstrates the existence of an important dimensionless parameter, referred to as the thermal performance factor of the collector, that compares the useful thermal energy which can be extracted from the heater to the overall thermal losses of that collector for a given set of input parameters. A sensitivity analysis of our thermal model has been performed for the most significant input parameters such as the incident solar irradiation, the inlet fluid temperature, the air mass flow rate, the depth of the fluid channel, the number and nature of the transparent covers in order to measure the impact of each of these parameters on our model. An important result which can be drawn from this study is that the heat transfer model developed is robust enough to be used for thermal design studies of most known flat plate solar air heaters, but also of flat plate solar water collectors and linear solar concentrators.
VERIFICATION OF HYBRID NUMERICAL SCHEME FOR THE CASE OF COMPRESSIBLE JET IMPINGIMENT ON FLAT PLATE
Directory of Open Access Journals (Sweden)
2016-01-01
Full Text Available The article deals with the questions of mathematical modeling of compressible jet outflow from model nozzle and jet impingiment on flat plate at various values of n. pisoCentralFoam solver which is based on the Kurganov-Tadmor hy- brid numerical scheme, PISO algorithm and finite volume method, is used for the solution of this problem. The model, based on unsteady Reynolds equation and K-omega SST turbulence model with boundary functions is used for compressi- ble jet calculation. The problem definition for calculation of jet impingiment on flat plate is given. The simulation domainwas selected as a rectangle. Only a half of the nozzle was considered for simplification. The mixed boundary condition for pressure setting in case of free jet was used on the outlet of simulation domain. The special condition for the pressure with table data, allowed to increase the value of pressure gradually, was used on the inlet of simulation domain. The value of the jet pressure degree was selected as n = 2.5 and n = 5.0. The results of distribution of the velocity magnitude, field pressure, upon symmetry axes were received. The simulations were done with grids 100 000-500 000 cells. The average value of y+ was equal to 270. The calculations were done for the end time Tend = 0.01 s. Comparison of the results of pressure distribution calculation based on nozzle length on different grids with the results of the experiment is carried out. The coin- cidence to engineering accuracy of 5 % is received.
Kegerise, Michael A.; Rufer, Shann J.
2016-08-01
In this paper, we report on the application of the atomic layer thermopile (ALTP) heat-flux sensor to the measurement of laminar-to-turbulent transition in a hypersonic flat-plate boundary layer. The centerline of the flat-plate model was instrumented with a streamwise array of ALTP sensors, and the flat-plate model was exposed to a Mach 6 freestream over a range of unit Reynolds numbers. Here, we observed an unstable band of frequencies that are associated with second-mode instability waves in the laminar boundary layer that forms on the flat-plate surface. The measured frequencies, group velocities, phase speeds, and wavelengths of these instability waves are consistent with data previously reported in the literature. Heat flux time series, and the Morlet wavelet transforms of them, revealed the wave-packet nature of the second-mode instability waves. In addition, a laser-based radiative heating system was used to measure the frequency response functions (FRF) of the ALTP sensors used in the wind tunnel test. These measurements were used to assess the stability of the sensor FRFs over time and to correct spectral estimates for any attenuation caused by the finite sensor bandwidth.
Film Condensation with and Without Body Force in Boundary-Layer Flow of Vapor Over a Flat Plate
Chung, Paul M.
1961-01-01
Laminar film condensation under the simultaneous influence of gas-liquid interface shear and body force (g force) is analyzed over a flat plate. Important parameters governing condensation and heat transfer of pure vapor are determined. Mixtures of condensable vapor and noncondensable gas are also analyzed. The conditions under which the body force has a significant influence on condensation are determined.
Johnson, S. M.
1976-01-01
Basic test results are reported for a flat plate solar collector whose performance was determined in a solar simulator. The collector was tested over ranges of inlet temperatures, fluxes and one coolant flow rate. Collector efficiency is correlated in terms of inlet temperature and flux level.
Heat Loss Mechanisms In Transparent Insulation With Honeycomb Structures
Wittwer, V.; Stahl, W.; Pfluger, A.; Goetzberger, A.; Schmid, J.
1983-12-01
The development of highly transparent insulation materials is an important step in raising the efficiency of flat plate collectors and for passive use of solar energy in buildings. The problem in combining selective absorbers and honeycomb structures is that the radiation losses due to thermal emission of the material of the structure may be larger than the losses due to convection which are present without the structure. Therefore a thorough analysis of the different loss mechanisms has been made. There are two possibilities for overcoming these difficulties. The first is the use of materials with low absorptance in the infrared or with selective surfaces for the honeycomb structure. The second possibility is the use of highly IR-absorbing materials. In the latter case a selective absorber is not needed. Results from both approaches will be presented.
Lance, Blake W.
Simulations are becoming increasingly popular in science and engineering. One type of simulation is Computation Fluid Dynamics (CFD) that is used when closed forms solutions are impractical. The field of Verification & Validation emerged from the need to assess simulation accuracy as they often contain approximations and calibrations. Validation involves the comparison of experimental data with simulation outputs and is the focus of this work. Errors in simulation predictions may be assessed in this way. Validation requires highly-detailed data and description to accompany these data, and uncertainties are very important. The purpose of this work is to provide highly complete validation data to assess the accuracy of CFD simulations. This aim is fundamentally different from the typical discovery experiments common in research. The measurement of these physics was not necessarily original but performed with modern, high-fidelity methods. Data were tabulated through an online database for direct use in Reynolds-Averaged Navier-Stokes simulations. Detailed instrumentation and documentation were used to make the data more useful for validation. This work fills the validation data gap for steady and transient mixed convection. The physics in this study included mixed convection on a vertical flat plate. Mixed convection is a condition where both forced and natural convection influence fluid momentum and heat transfer phenomena. Flow was forced over a vertical flat plate in a facility built for validation experiments. Thermal and velocity data were acquired for steady and transient flow conditions. The steady case included both buoyancy-aided and buoyancy-opposed mixed convection while the transient case was for buoyancy-opposed flow. The transient was a ramp-down flow transient, and results were ensemble-averaged for improved statistics. Uncertainty quantification was performed on all results with bias and random sources. An independent method of measuring heat flux was
DEFF Research Database (Denmark)
Tian, Zhiyong; Perers, Bengt; Furbo, Simon
2017-01-01
in large solar heating plants for a district heating network, a hybrid solar collector field with 5960 m2 flat plate collectors and 4039 m2 parabolic trough collectors in series was constructed in Taars, Denmark. The design principle is that the flat plate collectors preheat the return water from...... for this type of hybrid solar district heating plants with flat plate collectors and parabolic trough collectors in the Nordic region, but also introduce a novel design concept of solar district heating plants to other high solar radiation areas.......Flat plate collectors have relatively low efficiency at the typical supply temperatures of district heating networks (70–95 °C). Parabolic trough collectors retain their high efficiency at these temperatures. To maximize the advantages of flat plate collectors and parabolic trough collectors...
Parametric Influence on Thermal Performance of Flat Plate Closed Loop Pulsating Heat Pipes
Institute of Scientific and Technical Information of China (English)
YANG Hong-hai; KHANDEKAR Sameer; GROLL Manfred
2006-01-01
This paper presents an experimental study on a flat plate closed loop pulsating heat pipes. It consisted of total 40 channels with square cross section (2 × 2 mm2, 165 mm long) machined directly on an aluminum plate(180× 120×3mm3 ), which was covered by a transparent plate. The working fluid employed was ethanol. As the results, the influence parameters of thermal performance were investigated, such as filling ratio, heat load and operational orientations etc. Filling ratio was found to be a critical parameter, and its effect was rather complicated. According to its values the PHP plate could have four distinct working zones with different operational characteristics and heat transfer performance. The effect of heat load on thermal performance was found to be positive, and in general,increasing the heat load would improve heat transfer performance. In order to analyze the effect of gravity on thermal performance, three different heat modes and total seven tilt angles were tested and compared. Successful operation at all orientations with respect to gravity was also achieved.
Vortex Formation, Shedding and Energy Harvesting from a Cyber-Physical Pitching Flat Plate
Onoue, Kyohei; Breuer, Kenneth
2014-11-01
We examine the dynamics and energy harvesting capabilities of an elastically mounted flat plate undergoing large amplitude limit cycle oscillations in a uniform flow. All experiments are performed using a cyber-physical system, wherein the structural inertia, stiffness and damping are numerically simulated using a position-following feedback algorithm. The cyber-physical system also allows for implementation of nonlinear spring and damping coefficients, which control the plate dynamics and subsequent energy harvesting characteristics. Analysis of the plate kinematics and the fluid flow over the plate and in the wake (measured using PIV) are used to understand the interplay between structural motion and vortex formation at the sharp leading and trailing edges of the plate. By varying the structural properties of the system we systematically analyze the formation, strength, stability and separation of the leading edge vortex, as well as the dependence on kinematic parameters and Reynolds number. Connections to previous results on vortex formation time and bluff body aerodynamics are discussed. This research is funded by the Air Force Office of Scientific Research (AFOSR).
A Dynamic Multinode Model for Component-Oriented Thermal Analysis of Flat-Plate Solar Collectors
Directory of Open Access Journals (Sweden)
Christoph N. Reiter
2015-01-01
Full Text Available A mathematical model of a flat-plate solar collector was developed on the basis of the physical principles of optics and heat transfer in order to determine collector’s component temperatures as well as collector efficiency. In contrast to many available models, the targeted use of this dynamic model is the detailed, theoretical investigation of the thermal behaviour of newly developed or adjusted collector designs on component level, for example, absorber, casing, or transparent cover. The defined model is based on a multinode network (absorber, fluid, glazing, and backside insulation containing the relevant physical equations to transfer the energy. The heat transfer network covers heat conduction, convection, and radiation. Furthermore, the collector optics is defined for the plane glazing and the absorber surface and also considers interactions between them. The model enables the variation of physical properties considering the geometric parameters and materials. Finally, the model was validated using measurement data and existing efficiency curve models. Both comparisons proved high accuracy of the developed model with deviation of up to 3% in collector efficiency and 1 K in component temperatures.
NUMERICAL INVESTIGATIONS INTO THE FRICTION REDUCTION BY MICROBUBBLES FOR FLAT PLATES
Institute of Scientific and Technical Information of China (English)
Zhan De-xin; Wang Jia-mei; Lin Li-ming
2003-01-01
The two-dimensional flow on the flat plate with injected microbubbles is simulated using the software, PHOENICS (V3.2), usually used in the CFD (Computational Fluid Dynamics).A set of formulas for K-ε turbulence model modified with the presence of microbubbles, is employed.With considering the effect of gravity, interfacial lift, interphase friction, virtual mass force and interfacial pressure on the flow with microbubbles, numerical calculations for the influence of variable air volume fracton as well as distribution, injecting speed, microbubble diameter and position of introducing microbubbles on the friction reduction are presented.Results show that the friction reduction increases with increasing volume fraction and microbubble diameter within the range of 100μm, and that the velocity in the boundary layer with microbubbles is greater than that without microbubbles.The order of magnitude and trends of the experimental skin-friction are reproduced well.The uniform free-stream speed in all cases is 4m/s, giving Reynolds number of up to 20 million.
Crust behavior in simultaneous melting and freezing on a submerged flat plate
Energy Technology Data Exchange (ETDEWEB)
Ganguli, A.; Bankoff, S.G.
1978-12-01
A theoretical and experimental investigation of the solidification of a flowing liquid onto a melting wall was carried out. In particular, the experimental work involved open channel laminar flow of water over a flat plate of n-decane. The point of interest is the dynamic behavior of the solidified crust, which forms a leading edge by melting. The motion of this leading edge was determined as a function of the water temperature, velocity, decane temperature and outlet weir height. This melting rate was found to be very sensitive to the water temperature and less dependent upon the other parameters. An approximate numerical method, using polynomial temperature profiles with time dependent coefficients, was used to solve the one-dimensional heat conduction model. From this, the dynamic behavior of the crust was predicted as a function of the experimental parameters and the local heat transfer coefficient on the freezing surface, which was later estimated. There is reasonable agreement between the predicted and experimentally observed motions of the leading edge.
A method for measuring skin friction drag on a flat plate in contaminated gas flows
Oetting, R. B.; Patterson, G. K.
1984-01-01
A technique for measuring friction drag in turbulent gas and gas/particle flows over flat plates is presented, and preliminary results are reported. A 0.25-in.-thick 72 x 6-in. Al plate is suspended by six horizontal support air bearings and four vertical alignment air bearings between fixed dummy plates and leading-edge and trailing-edge fairings in the 32-in.-high 48-in.-wide 11-ft-long test section of a closed-circuit atmospheric wind tunnel operating at 50-150 ft/sec. Particles of Fe and Al oxides of diameter 20-150 microns and density up to 0.3 lb particles per lb air are injected via a 6 x 0.167-in. nozzle; turbulence is induced by a roughened section of the leading-edge fairing; and friction drag is measured using a load-cell pressure transducer. Sample results are shown in a graph, demonstrating good agreement with theoretical drag calculations.
Production of Fatty Acids and Protein by Nannochloropsis in Flat-Plate Photobioreactors.
Hulatt, Chris J; Wijffels, René H; Bolla, Sylvie; Kiron, Viswanath
2017-01-01
Nannochloropsis is an industrially-promising microalga that may be cultivated for alternative sources of nutrition due to its high productivity, protein content and lipid composition. We studied the growth and biochemical profile of Nannochloropsis 211/78 (CCAP) in optimized flat-plate photobioreactors. Eighteen cultivations were performed at two nutrient concentrations. The fatty acid, protein content and calorific values were analyzed after 8, 12 and 16 days. Neutral lipids were separated and the changes in fatty acids in triglycerides (TAGs) during nutrient depletion were recorded. The maximum cell density reached 4.7 g∙L-1 and the maximum productivity was 0.51 g∙L-1∙d-1. During nutrient-replete conditions, eicosapentaneoic acid (EPA) and total protein concentrations measured 4.2-4.9% and 50-55% of the dry mass, respectively. Nutrient starvation induced the accumulation of fatty acids up to 28.3% of the cell dry weight, largely due to the incorporation of C16:0 and C16:1n-7 fatty acyl chains into neutral lipids. During nutrient starvation the total EPA content did not detectibly change, but up to 37% was transferred from polar membrane lipids to the neutral lipid fraction.
Lipid accumulation and growth of Chlorella zofingiensis in flat plate photobioreactors outdoors.
Feng, Pingzhong; Deng, Zhongyang; Hu, Zhengyu; Fan, Lu
2011-11-01
Culturing microalgae using natural sunlight is an effective way to reduce the cost of microalgae-based biodiesel production. In order to evaluate the feasibility of culturing Chlorella zofingiensis outdoors for biodiesel production, effects of nitrogen limitation and initial cell concentration on growth and lipid accumulation of this alga were investigated in 60 L flat plate photobioreactors outdoors. The highest μmax and biomass productivity obtained was 0.994 day(-1) and 58.4 mg L(-1)day(-1), respectively. The lipid content was much higher (54.5% of dry weight) under nitrogen limiting condition than under nitrogen sufficient condition (27.3%). With the increasing initial cell concentrations, the lipid contents declined, while lipid concentrations and productivities increased. The highest lipid content, lipid concentration, and lipid productivity obtained was 54.5%, 536 mg L(-1) and 22.3 mg L(-1)day(-1), respectively. This study demonstrated that it was possible to culture C. zofingiensis under outdoor conditions for producing biodiesel feedstock.
Directory of Open Access Journals (Sweden)
Md. Mamun Molla
2014-01-01
Full Text Available The purpose of this study is to investigate the natural convection laminar flow along an isothermal vertical flat plate immersed in a fluid with viscosity which is the exponential function of fluid temperature in presence of internal heat generation. The governing boundary layer equations are transformed into a nondimensional form and the resulting nonlinear system of partial differential equations is reduced to a convenient form which are solved numerically using an efficient marching order implicit finite difference method with double sweep technique. Numerical results are presented in terms of the velocity and temperature distribution of the fluid as well as the heat transfer characteristics, namely, the wall shear stress and the local and average rate of heat transfer in terms of the local skin-friction coefficient, the local and average Nusselt number for a wide range of the viscosity-variation parameter, heat generation parameter, and the Rayleigh number. Increasing viscosity variation parameter and Rayleigh number lead to increasing the local and average Nusselt number and decreasing the wall shear stress. Wall shear stress and the rate of heat transfer decreased due to the increase of heat generation.
Effect of Localized Heating on Three-Dimensional Flat-Plate Oscillating Heat Pipe
Directory of Open Access Journals (Sweden)
S. M. Thompson
2010-01-01
Full Text Available An experimental investigation was conducted, both thermally and visually, on a three-dimensional flat-plate oscillating heat pipe (3D FP-OHP to characterize its performance under localized heat fluxes while operating in the bottom heating mode and charged with acetone at a filling ratio of 0.73. The cooling area was held constant and three heating areas of 20.16 cm2, 11.29 cm2, and 1.00 cm2 were investigated, respectively. It was found that as the heating area was reduced and higher heat fluxes were imposed, the thermal resistance increased and the amplitude of thermal oscillations in the evaporator increased and became more chaotic. Using neutron radiography, it was observed that fluid oscillations did not occur in outer channels located away from the region of local heating. Although the thermal resistance increased during localized heating, a maximum heat flux of 180 W/cm2 was achieved with the average evaporator temperature not exceeding 90∘C.
Design, construction and testing of a liquid-heating flat-plate solar collector
Energy Technology Data Exchange (ETDEWEB)
Tuttle, R E
1980-02-01
The purpose of this study was to design, construct, and test a liquid-heating flat-plate solar collector. From the literature search, information was gathered concerning the basic components of the collector, the different processes and materials that can be used in the construction of these components, and their advantages and disadvantages. The literature search also revealed a method used to measure the performance of the collector in terms of efficiency and heat output. Design considerations were then listed for each of the major components as well as the collector as a single unit. Then, each component was designed, taking into consideration the final assembly of the completed unit. Detailed designs were required for the absorber plate and the box and frame assembly because of their complexity in construction and assembly. Once the components were designed, the construction details were arranged in a logical sequence, again considering the final assembly of the unit. The collector was then carefully constructed and assembled following the design details. After the solar collector was assembled completely, tests were made, data were obtained and recorded, and a collector performance curve was developed.
Design of a novel flat-plate photobioreactor system for green algal hydrogen production
Energy Technology Data Exchange (ETDEWEB)
Tamburic, B.; Zemichael, F.W.; Maitland, G.C.; Hellgardt, K. [Imperial College London (United Kingdom)
2010-07-01
Some unicellular green algae have the ability to photosynthetically produce molecular hydrogen using sunlight and water. This renewable, carbon-neutral process has the additional benefit of sequestering carbon dioxide during the algal growth phase. The main costs associated with this process result from building and operating a photobioreactor system. The challenge is to design an innovative and cost effective photobioreactor that meets the requirements of algal growth and sustainable hydrogen production. We document the details of a novel 1 litre vertical flat-plate photobioreactor that has been designed to accommodate green algal hydrogen production at the laboratory scale. Coherent, non-heating illumination is provided by a panel of cool white LEDs. The reactor body consists of two compartments constructed from transparent Perspex sheets. The primary compartment holds the algal culture, which is agitated by means of a recirculating gas flow. A secondary compartment is filled with water and used to control the temperature and wavelength of the system. The reactor is fitted with instruments that monitor the pH, pO{sub 2}, temperature and optical density of the culture. A membrane-inlet mass spectrometry system has been developed for hydrogen collection and in situ monitoring. The reactor is fully autoclaveable and the possibility of hydrogen leaks has been minimised. The modular nature of the reactor allows efficient cleaning and maintenance. (orig.)
Wavenumber resonance in nonlinear wave interactions in the wake of a flat plate
Davila, Jose Benigno
The spatial traits of nonlinear wave interactions in transitioning flow in the symmetric wake of a flat plate were studied. The study combines the use of hot wire anemometry and digital analysis techniques for extracting frequency and wavenumber information from velocity fluctuation time series measurements. The linear spatial coherence was computed from velocity fluctuation data in order to determine if the frequency modes behave as waves, that is, spatially coherent fluctuations with a well defined dispersion relation. A new method was used to compute the mode triad wavenumber mismatch. The results were used to determine to what extent wavenumber resonance is present among quadratically interacting frequency resonant modes, as predicted by resonant wave interaction theory. The results show that, in the early part of the transition, instability modes interact nonlinearity to generate spatially coherent modes at frequencies above the instability range. Quadratically interacting, frequency resonant mode triads involve the transfer of energy to the harmonics of the fundamental instability exhibit good wavenumber resonance, as predicted by resonant wave interaction theory.
Directory of Open Access Journals (Sweden)
Héctor L. Otálvaro-Marín
2014-01-01
Full Text Available This study provides information to design heterogeneous photocatalytic solar reactors with flat plate geometry used in treatment of effluents and conversion of biomass to hydrogen. The concept of boundary layer of photon absorption taking into account the efficient absorption of radiant energy was introduced; this concept can be understood as the reactor thickness measured from the irradiated surface where 99% of total energy is absorbed. Its thickness and the volumetric rate of photons absorption (VRPA were used as design parameters to determine (i reactor thickness, (ii maximum absorbed radiant energy, and (iii the optimal catalyst concentration. Six different commercial brands of titanium dioxide were studied: Evonik-Degussa P-25, Aldrich, Merck, Hombikat, Fluka, and Fisher. The local volumetric rate of photon absorption (LVRPA inside the reactor was described using six-flux absorption-scattering model (SFM applied to solar radiation. The radiation field and the boundary layer thickness of photon absorption were simulated with absorption and dispersion effects of catalysts in water at different catalyst loadings. The relationship between catalyst loading and reactor thickness that maximizes the absorption of radiant energy was obtained for each catalyst by apparent optical thickness. The optimum concentration of photocatalyst Degussa P-25 was 0.2 g/l in 0.86 cm of thickness, and for photocatalyst Aldrich it was 0.3 g/l in 0.80 cm of thickness.
A diagram for defined flat plate solar collector area for solar floor heating
Energy Technology Data Exchange (ETDEWEB)
Altuntop, N.; Tekin, Y. [Erciyes University, Dept. of Mechanical Engineering (Turkey); Cengel, Y.A. [Nevada Reno University, Dept. of Mechanical Engineering, NV (United States)
2000-07-01
In winters, one of the best ways to heat living areas by using the low- temperature - water obtained from flat-plate solar collectors is the floor heating. In floor heating, low temperature-water (30 + 60 deg C) can be used and heat can be stored in water when solar radiation is not possible. In this study, it is aimed to define collector surface needed to supply heat for floor heating. It is also aimed to define and explain the diagram developed for every heating months. The calculations about the sun geometry are used to define the amount of radiation coming in to the collectors. Formulations are made about the definition of solar radiation absorbed by the collectors, the total heat loss coefficient, and the collector plate surface temperature. These formulations are transformed in to the diagram. In addition, the studies, heat transfer calculations and design parameters about the floor of the heating areas are used. A combined collector floor heating diagram is obtained. This diagram is used to define collector surface area necessary to supply heat for floor heated places. In this diagram, the collector surface area is obtained by giving the heat capacity of the place area, floor surface temperature, approximate modulation distance of the floor, the elevation of city, collector slope angle, wind speed, sun shine lime and the amount of the solar radiation obtained from the solar radiation diagram. (authors)
Calculating forces on thin flat plates with incomplete vorticity-field data
Limacher, Eric; Morton, Chris; Wood, David
2016-11-01
Optical experimental techniques such as particle image velocimetry (PIV) permit detailed quantification of velocities in the wakes of bluff bodies. Patterns in the wake development are significant to force generation, but it is not trivial to quantitatively relate changes in the wake to changes in measured forces. Key difficulties in this regard include: (i) accurate quantification of velocities close to the body, and (ii) the effect of missing velocity or vorticity data in regions where optical access is obscured. In the present work, we consider force formulations based on the vorticity field, wherein mathematical manipulation eliminates the need for accurate near-body velocity information. Attention is restricted to nominally two dimensional problems, namely (i) a linearly accelerating flat plate, investigated using PIV in a water tunnel, and (ii) a pitching plate in a freestream flow, as investigated numerically by Wang & Eldredge (2013). The effect of missing vorticity data on the pressure side of the plate has a significant impact on the calculation of force for the pitching plate test case. Fortunately, if the vorticity on the pressure side remains confined to a thin boundary layer, simple corrections can be applied to recover a force estimate.
Changes in Flat Plate Wake Characteristics Obtained With Decreasing Plate Thickness
Rai, Man Mohan
2016-01-01
The near and very near wake of a flat plate with a circular trailing edge is investigated with data from direct numerical simulations. Computations were performed for four different Reynolds numbers based on plate thickness (D) and at constant plate length. The value of ?/D varies by a factor of approximately 20 in the computations (? being the boundary layer momentum thickness at the trailing edge). The separating boundary layers are turbulent in all the cases. One objective of the study is to understand the changes in wake characteristics as the plate thickness is reduced (increasing ?/D). Vortex shedding is vigorous in the low ?/D cases with a substantial decrease in shedding intensity in the largest ?/D case (for all practical purposes shedding becomes almost intermittent). Other characteristics that are significantly altered with increasing ?/D are the roll-up of the detached shear layers and the magnitude of fluctuations in shedding period. These effects are explored in depth. The effects of changing ?/D on the distributions of the time-averaged, near-wake velocity statistics are discussed.
Experimental investigation of a large aspect ratio flat plate encountering a steam-wise gust
Mulleners, Karen; Mancini, Peter; Jones, Anya
2015-11-01
While humans are capable of mimicking, and even outperform, the kinematic capabilities of natural flyers, birds and insects are still way ahead of us when it comes to anticipating and dealing with turbulent and gusty flow conditions. To tailor and improve flight control capabilities of low Reynolds number flyers in real weather, we need to bridge this gap of knowledge. As a first step, we experimentally studied the aerodynamic influence of a simplified stream-wise gust on a large aspect ratio flat plate. The experiments were conduction in the 7 × 1 . 5 × 1 m3 towing tank at UMD which was equipped with a 4-axis computer-controlled motion system. The effect of a stream-wise gust was simulated by accelerating or decelerating the wing to a new constant velocity after an initial constant surge. A high-speed camera and light sheet optics were attached to the tow carriage allowing for time-resolved particle image velocimetry along the entire motion in addition to direct force measurements. A proper orthogonal decomposition of the flow field was carried out to study the time scales related to changes induced by the sudden acceleration or deceleration in addition to analyzing the size, position and trajectory of prominent vortices and associated forces during the gust encounter.
Transient-forced convection film boiling on an isothermal flat plate.
Nagendra, H. R.
1972-01-01
Development of a new approach for the solution of transient-forced convection film boiling on an isothermal flat plate using the boundary layer model. The similarity variables are used to convert the governing partial differential equations to ordinary ones. The results of numerical solutions of these ordinary equations indicate that the transient process can be classified as one-dimensional conduction, intermediate, and the steady-state regions. The time required for the one-dimensional conduction and the time necessary to attain a steady-state condition are obtained. The use of local similarity approximations for the intermediate regime facilitates prediction of complete boundary layer growth. Using the ratio of time at any instant to the steady-state time as abscissa, the curves representing the boundary layer growth can be merged into a single mean curve within 5%. Further, the analysis shows that the average rate of heat transfer during transient is 50 to 100% higher than those at steady state. The average rate of vapor convected away is 10 to 15% lower than at steady state while the average rate of accumulation to form the vapor layer is 1 to 14 times larger.
Earth Reflected Solar Radiation Incident upon an Arbitrarily Oriented Spinning Flat Plate
Cunningham, Fred G.
1963-01-01
A general derivation is given for the earth reflected solar radiation input to a flat plate--a solar cell paddle, for example--which is spinning about an axis coincident with the axis of symmetry of the satellite to which it is affixed. The resulting equations are written for the general case so that arbitrary orientations of the spin axis with respect to the earth-satellite line and arbitrary orientations of the normal to the plate with respect to the spin axis can be treated. No attempt is made to perform the resulting integrations because of the complexity of the equations; nor is there any attempt to delineate the integration limits for the general case. However, the equations governing these limits are given. The appendixes contain: the results, in graphical form, of two representative examples; the general computer program for the calculation is given in Fortran notation; and the results of a calculation of the distribution of albedo energy on the proposed Echo II satellite. The value of the mean solar constant used is 1.395 times 10 (sup 4) ergs per centimeters-squared per second; the mean albedo of the earth is assumed to be 0.34; and the earth is assumed to be a diffuse reflector.
Investigation into the causes of browning in EVA encapsulated flat plate PV modules
Energy Technology Data Exchange (ETDEWEB)
Holley, W.H. Jr.; Agro, S.C.; Galica, J.P.; Thoma, L.A.; Yorgensen, R.S. [Springborn Labs., Inc., Enfield, CT (United States); Ezrin, M.; Klemchuk, P.; Lavigne, G. [Univ. of Connecticut, Storrs, CT (United States). Inst of Materials Science; Thomas, H. [National Renewable Energy Lab., Golden, CO (United States)
1994-12-31
The problem of browning in a number of EVA encapsulated flat plate photovoltaic modules has led to the questioning of EVA as a suitable material for such applications. By isolating the variables that could possibly lead to EVA browning, such as module construction, types of glass superstrates, additives, and processing conditions, the authors have been able to determine those significant specific variables that seem to have the most influence on discoloration.When standard-cure EVA-based laminates were exposed to accelerated UV aging, measurable yellowing of those laminates was evident after only one to two weeks exposure, and visual discoloration was observed after four to six weeks. Some samples yellowed quickly and some not at all, and there were significant differences in the rates of discoloration between standard-cure and fast-cure EVA. This paper looks at the results of these studies, especially focusing on the effect of additives in the EVA on the rate of yellowing, and discusses how preliminary results can be used to reformulate EVA encapsulants.
Heat Transfer Analysis of a Flat-plate Solar Collector Running a Solid Adsorption Refrigerator
Directory of Open Access Journals (Sweden)
S. Thiao
2014-05-01
Full Text Available Adsorption solar cooling appears to have prospect in the tropical countries. The present study is a theoretical investigation of the performance of a solar adsorption refrigerator using a flat-plate solar collector. The values of glass cover and absorber plate temperatures obtained from numerical solutions of heat balance equations are used to predict the solar coefficient of performance of the solar refrigerator. The simulation technique takes into account the variations of ambient temperature and solar radiation along the day. The effects of optical parameters of the glass cover such as absorption and transmission coefficients on glass cover and absorber plate temperatures and consequently on the coefficient of performance are analyzed. As a result, it is found that the absorber plate temperature is less to the absorption coefficient than the cover glass temperature. Also the thermal radiation exchange has more effect on the cover glass temperature. The higher values of COP are obtained between 11 and 13 h during the morning when the temperatures of the absorber plate and the ambient temperatures increase. Moreover the COP increases with the coefficient of transmission of the glass cover but the main parameter acting on the variations of the COP remains the temperature of the evaporator.
Flowfield measurements in a separated and reattached flat plate turbulent boundary layer
Patrick, William P.
1987-03-01
The separation and reattachment of a large-scale, two-dimensional turbulent boundary layer at low subsonic speed on a flat plate has been studied experimentally. The separation bubble was 55 cm long and had a maximum bubble thickness, measured to the height of the mean dividing streamline, of 17 cm, which was twice the thickness of the inlet boundary layer. A combination of laser velocimetry, hot-wire anemometry, pneumatic probing techniques, and flow visualization were used as diagnostics. Principal findings were that an outer inviscid rotational flow was defined which essentially convected over the blockage associated with the inner, viscously dominated bubble recirculation region. A strong backflow region in which the flow moved upstream 100 percent of the time was measured near the test surface over the central 35 percent of the bubble. A laminar backflow boundary layer having pseudo-turbulent characteristics including a log-linear velocity profile was generated under the highly turbulent backflow. Velocity profile shapes in the reversed flow region matched a previously developed universal backflow profile at the upstream edge of the separation region but not in the steady backflow region downstream. A smoke flow visualization movie and hot-film measurements revealed low frequency nonperiodic flapping at reattachment. However, forward flow fraction data at reattachment and mean velocity profiles in the redeveloping boundary layer downstream of reattachment correlated with backward-facing step data when the axial dimension was scaled by the distance from the maximum bubble thickness to reattachment.
Hydrogen production by Rhodobacter sphaeroides O.U.001 in a flat plate solar bioreactor
Energy Technology Data Exchange (ETDEWEB)
Eroglu, Inci; Tabanoglu, Altan; Eroglu, Ela [Department of Chemical Engineering, Middle East Technical University, 06531 Ankara (Turkey); Guenduez, Ufuk; Yuecel, Meral [Department of Biology, Middle East Technical University, 06531 Ankara (Turkey)
2008-01-15
Rhodobacter sphaeroides O.U.001 can produce hydrogen under anaerobic conditions and illumination. The objective of this study was to investigate the performance of an 8 l flat plate solar bioreactor operating in outdoor conditions. Different organic acids were used as carbon sources (malate, lactate and acetate) and olive mill waste water was used as a sole substrate source. The consumption and the production of the organic acids were determined by HPLC. The accumulation of by-products, such as poly-{beta}-hydroxybutyrate (PHB) and carotenoid, throughout the course of hydrogen production was determined. The hydrogen production rate was highest (0.01 l/l/h) when malate was the carbon source. Formate was observed as the fermentation end product. Acetate resulted in low hydrogen gas production and high PHB accumulation. When acetate was used as the carbon source, butyrate was produced as a result of fermentation. Promising amounts of PHB and caretenoid were accumulated during hydrogen production from diluted olive mill wastewater. (author)
Sun, Yahui; Huang, Yun; Liao, Qiang; Fu, Qian; Zhu, Xun
2016-05-01
To offset the adverse effects of light attenuation on microalgae growth, hollow polymethyl methacrylate (PMMA) tubes were embedded into a flat-plate photobioreactor (PBR) as light guides. In this way, a fraction of incident light could be transmitted and emitted to the interior of the PBR, providing a secondary light source for cells in light-deficient regions. The average light intensity of interior regions 3-6cm from surfaces with 70μmolm(-2)s(-1) incident light was enhanced 2-6.5 times after 3.5days cultivation, resulting in a 23.42% increase in biomass production to that cultivated in PBR without PMMA tubes. The photosynthetic efficiency of microalgae in the proposed PBR was increased to 12.52%. Moreover, the installation of hollow PMMA tubes induced turbulent flow in the microalgae suspension, promoting microalgae suspension mixing. However, the enhanced biomass production was mainly attributed to the optimized light distribution in the PBR. Copyright © 2016 Elsevier Ltd. All rights reserved.
Production of Fatty Acids and Protein by Nannochloropsis in Flat-Plate Photobioreactors
Wijffels, René H.; Bolla, Sylvie; Kiron, Viswanath
2017-01-01
Nannochloropsis is an industrially-promising microalga that may be cultivated for alternative sources of nutrition due to its high productivity, protein content and lipid composition. We studied the growth and biochemical profile of Nannochloropsis 211/78 (CCAP) in optimized flat-plate photobioreactors. Eighteen cultivations were performed at two nutrient concentrations. The fatty acid, protein content and calorific values were analyzed after 8, 12 and 16 days. Neutral lipids were separated and the changes in fatty acids in triglycerides (TAGs) during nutrient depletion were recorded. The maximum cell density reached 4.7 g∙L-1 and the maximum productivity was 0.51 g∙L-1∙d-1. During nutrient-replete conditions, eicosapentaneoic acid (EPA) and total protein concentrations measured 4.2–4.9% and 50–55% of the dry mass, respectively. Nutrient starvation induced the accumulation of fatty acids up to 28.3% of the cell dry weight, largely due to the incorporation of C16:0 and C16:1n-7 fatty acyl chains into neutral lipids. During nutrient starvation the total EPA content did not detectibly change, but up to 37% was transferred from polar membrane lipids to the neutral lipid fraction. PMID:28103296
Leading-edge vortex burst on a low-aspect-ratio rotating flat plate
Medina, Albert; Jones, Anya R.
2016-08-01
This study experimentally investigates the phenomenon of leading-edge-vortex burst on rotating flat plate wings. An aspect-ratio-2 wing was driven in pure rotation at a Reynolds number of Re=2500 . Of primary interest is the evolution of the leading-edge vortex along the wing span over a single-revolution wing stroke. Direct force measurements of the lift produced by the wing revealed a single global lift maximum relatively early in the wing stroke. Stereoscopic particle image velocimetry was applied to several chordwise planes to quantify the structure and strength of the leading-edge vortex and its effect on lift production. This analysis revealed opposite-sign vorticity entrainment into the core of the leading-edge vortex, originating from a layer of secondary vorticity along the wing surface. Coincident with the lift peak, there emerged both a concentration of opposite vorticity in the leading-edge-vortex core, as well as axial flow stagnation within the leading-edge-vortex core. Planar control volume analysis was performed at the midspan to quantify the contributions of vorticity transport mechanisms to the leading-edge-vortex circulation. The rate of circulation annihilation by opposite-signed vorticity entrainment was found to be minimal during peak lift production, where convection balanced the flux of vorticity resulting in stagnation and eventually reversal of axial flow. Finally, vortex burst was found to be correlated with swirl number, where bursting occurs at a swirl threshold of Sw<0.6 .
Experimental Study on Performance of a Box Solar Cooker with Flat Plate Collector to Boil Water
Sitepu, T.; Gunawan, S.; Nasution, D. M.; Ambarita, H.; Siregar, R. E. T.; Ronowikarto, A. D.
2017-03-01
In this study, a flat plate type solar cooker is tested by exposing in solar irradiation. The objective is to examine the performance of solar cooker in boiling water. The solar cooker is a box type with collector area and height are 100 × 100 cm and 40 cm, respectively. Vessel for water is made of aluminum plate with diameter and height of 22 cm and 15 cm. The experiments are performed by varying mass of the water. It is 2 kg and 4 kg, respectively. Every experiment starts from 10:00 AM until the boiling temperature is reached. The parameters measured are radiance intensity, ambient and solar box cooker temperatures, and wind speed. The results show that the duration of water heating up to 100°C with water mass 2 kg within 2 hours 45 minutes and water mass 4 kg within 3 hours 17 minutes. The maximum temperatur of solar box cooker is 117°C at 12:56 PM and maximum efficiency is 46.30%. The main conclusion can be drawn here is that a simple solar box cooker can be used to boil water.
Heat transfer in a low latitude flat-plate solar collector
Directory of Open Access Journals (Sweden)
Oko C.O.C.
2012-01-01
Full Text Available Study of rate of heat transfer in a flat-plate solar collector is the main subject of this paper. Measurements of collector and working fluid temperatures were carried out for one year covering the harmattan and rainy seasons in Port Harcourt, Nigeria, which is situated at the latitude of 4.858oN and longitude of 8.372oE. Energy balance equations for heat exchanger were employed to develop a mathematical model which relates the working fluid temperature with the vital collector geometric and physical design parameters. The exit fluid temperature was used to compute the rate of heat transfer to the working fluid and the efficiency of the transfer. The optimum fluid temperatures obtained for the harmattan, rainy and yearly (or combined seasons were: 317.4, 314.9 and 316.2 [K], respectively. The corresponding insolation utilized were: 83.23, 76.61 and 79.92 [W/m2], respectively, with the corresponding mean collector efficiency of 0.190, 0.205 and 0.197 [-], respectively. The working fluid flowrate, the collector length and the range of time that gave rise to maximum results were: 0.0093 [kg/s], 2.0 [m] and 12PM - 13.00PM, respectively. There was good agreement between the computed and the measured working fluid temperatures. The results obtained are useful for the optimal design of the solar collector and its operations.
Directory of Open Access Journals (Sweden)
Rajendra Karwa
2014-01-01
Full Text Available The paper presents results of an analysis carried out using a mathematical model to find the effect of the uncertainties, variations, and tolerances in design and ambient parameters on the thermohydraulic performance of flat plate solar air heater. Analysis shows that, for the range of flow rates considered, a duct height of 10 mm is preferred from the thermohydraulic consideration. The thermal efficiency changes by about 2.6% on variation in the wind heat transfer coefficient, ±5 K variation in sky temperature affects the efficiency by about ±1.3%, and solar insolation variation from 500 to 1000 Wm−2 affects the efficiency by about −1.5 to 1.3% at the lowest flow rate of 0.01 kgs−1 m−2 of the absorber plate with black paint. In general, these effects reduce with increase in flow rate and are lower for collector with selective coating on the absorber plate surface. The tolerances in the duct height and absorber plate emissivity should be small while positive tolerance of 3° in the collector slope for winter operation and ±3° for year round operation, and a positive tolerance for the gap between the absorber plate and glass cover at nominal value of 40 mm are recommended.
Efficiency of liquid flat-plate solar energy collector with solar tracking system
Directory of Open Access Journals (Sweden)
Chekerovska Marija
2015-01-01
Full Text Available An extensive testing programme is performed on a solar collector experimental set-up, installed on a location in Shtip (Republic of Macedonia, latitude 41º 45’ and longitude 22º 12’, in order to investigate the effect of the sun tracking system implementation on the collector efficiency. The set-up consists of two flat plate solar collectors, one with a fixed surface tilted at 30о towards the South, and the other one equipped with dual-axis rotation system. The study includes development of a 3-D mathematical model of the collectors system and a numerical simulation programme, based on the computational fluid dynamics (CFD approach. The main aim of the mathematical modelling is to provide information on conduction, convection and radiation heat transfer, so as to simulate the heat transfer performances and the energy capture capabilities of the fixed and moving collectors in various operating modes. The feasibility of the proposed method was confirmed by experimental verification, showing significant increase of the daily energy capture by the moving collector, compared to the immobile collector unit. The comparative analysis demonstrates a good agreement between the experimental and numerically predicted results at different running conditions, which is a proof that the presented CFD modelling approach can be used for further investigations of different solar collectors configurations and flow schemes.
Vortex dynamics and surface pressure fluctuations on a normal flat plate
Hemmati, Arman; Wood, David H.; Martinuzzi, Robert J.; Ferrari, Simon W.; Hu, Yaoping
2016-11-01
The effect of vortex formation and interactions on surface pressure fluctuations is examined in the wake of a normal flat plate by analyzing Direct Numerical Simulations at Re =1200. A novel local maximum score-based 3D method is used to track vortex development in the region close to the plate where the major contributions to the surface pressure are generated. Three distinct vortex shedding regimes are identified by changes in the lift and drag fluctuations. The instances of maximum drag coincide with impingement of newly formed vortices on the plate. This results in large and concentrated areas of rotational and strain contributions to generation of pressure fluctuations. Streamwise vortex straining and chordwise stretching are correlated with the large ratios of streamwise to chordwise normal stresses and regions of significant rotational contribution to the pressure. In contrast at the minimum drag, the vorticity field close to the plate is disorganized, and vortex roll-up occurs farther downstream. This leads to a uniform distribution of pressure. This study was supported by Alberta Innovates Technology Futures (AITF) and Natural Sciences and Engineering Research Council of Canada (NSERC).
Effect of Glass Thickness on Performance of Flat Plate Solar Collectors for Fruits Drying
Directory of Open Access Journals (Sweden)
Ramadhani Bakari
2014-01-01
Full Text Available This study aimed at investigating the effect of thickness of glazing material on the performance of flat plate solar collectors. Performance of solar collector is affected by glaze transmittance, absorptance, and reflectance which results into major heat losses in the system. Four solar collector models with different glass thicknesses were designed, constructed, and experimentally tested for their performances. Collectors were both oriented to northsouth direction and tilted to an angle of 10° with the ground toward north direction. The area of each collector model was 0.72 m2 with a depth of 0.15 m. Low iron (extra clear glass of thicknesses 3 mm, 4 mm, 5 mm, and 6 mm was used as glazing materials. As a control, all collector performances were analysed and compared using a glass of 5 mm thickness and then with glass of different thickness. The results showed that change in glass thickness results into variation in collector efficiency. Collector with 4 mm glass thick gave the best efficiency of 35.4% compared to 27.8% for 6 mm glass thick. However, the use of glass of 4 mm thick needs precautions in handling and during placement to the collector to avoid extra costs due to breakage.
Thermal performance of solar air collector with transparent honeycomb made of glass tube
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
Transparent honeycomb structure with thin-walled glass tube as the honeycomb unit is designed and applied to a flat-plate solar air collector. Experiments are performed for solar collectors with six different honeycomb sizes. The emphasis is to study the effects of diameter and aspect ratio of the honeycomb unit on the transmittance and efficiency of the solar collector. It is shown that for the same diameter but different aspect ratios, there are large temperature differences between the collector’s exits; the smaller the aspect ratio, the larger the exit temperature, with a maximum difference of 10℃; for the same aspect ratio but different diameters, the temperature differences are small; the maximum temperature difference between the collectors with and without honeycombs is 12℃. A theoretical expression for the honeycomb transmittance is derived with a simplified method. The result shows that the honeycomb transmittance is only related with the aspect ratio and the materials’ optical properties but not the actual size of the honeycomb.
Thermal performance of solar air collector with transparent honeycomb made of glass tube
Institute of Scientific and Technical Information of China (English)
ZHANG ZhiQiang; ZUO Ran; LI Ping; SU WenJia
2009-01-01
Transparent honeycomb structure with thin-walled glass tube as the honeycomb unit is designed and applied to a flat-plate solar air collector.Experiments are performed for solar collectors with six different honeycomb sizes.The emphasis is to study the effects of diameter and aspect ratio of the honeycomb unit on the transmittance and efficiency of the solar collector.It is shown that for the same diameter but different aspect ratios,there are large temperature differences between the collector's exits;the smaller the aspect ratio,the larger the exit temperature,with a maximum difference of 10℃;for the same aspect ratio but different diameters,the temperature differences are small;the maximum temperature difference between the collectors with and without honeycombs is 12℃.A theoretical expression for the honeycomb transmittance is derived with a simplified method.The result shows that the honeycomb transmittance is only related with the aspect ratio and the materials' optical properties but not the actual size of the honeycomb.
Energy Technology Data Exchange (ETDEWEB)
Wissink, Jan G. [School of Engineering and Design, Howell Building, Brunel University, Uxbridge UB8 3PH (United Kingdom)], E-mail: jan.wissink@brunel.ac.uk; Rodi, Wolfgang [Institute for Hydromechanics, University of Karlsruhe, Kaiserstr. 12, D-76128 Karlsruhe (Germany)
2009-10-15
Direct numerical simulations (DNS) of flow over and heat transfer from a flat plate affected by free-stream fluctuations were performed. A contoured upper wall was employed to generate a favourable streamwise pressure gradient along a large portion of the flat plate. The free-stream fluctuations originated from a separate LES of isotropic turbulence in a box. In the laminar portions of the accelerating boundary layer flow the formation of streaks was observed to induce an increase in heat transfer by the exchange of hot fluid near the surface of the plate and cold fluid from the free-stream. In the regions where the streamwise pressure gradient was only mildly favourable, intermittent turbulent spots were detected which relaminarised downstream as the streamwise pressure gradient became stronger. The relaminarisation of the turbulent spots was reflected by a slight decrease in the friction coefficient, which converged to its laminar value in the region where the streamwise pressure gradient was strongest.
Institute of Scientific and Technical Information of China (English)
MIRZAEISEFAT Sina; FERNANDES Antonio Carlos
2013-01-01
This work describes investigations performed on the interaction of uniform current and freely rotating plate about a fixed vertical axis. Fluttering and autorotation are two different motions that may occur during the flow induced rotation. The dimensional analysis proves that the motion in flow induced rotation motion is governed essentially by the dimensionless moment of inertia and Reynolds number. Certain combinations define the stability boundaries between fluttering and autorotation. Fluttering is oscillation of body about a vertical axis and the autorotation is a name given to the case when the body turns continuously about the vertical axis. First, the loads and moment coefficients are calculated by experiments and streamline theory for different angles of attack for a fixed flat plate. Then for dynamic case, a bifurcation diagram is presented based on experiments to classify different motion states of flow induced rotation. Finally, a dynamical model is proposed for stability analysis of flow induced rotation of a flat plate.
American Society for Testing and Materials. Philadelphia
1986-01-01
1.1 This test method covers the determination of the resistance of flat plate solar collectors to water penetration when water is applied to their outer surfaces with a static air pressure at the outer surface higher than the pressure at the interior of the collector. 1.2 This test method is applicable to any flat plate solar collector. 1.3 The proper use of this test method requires a knowledge of the principles of pressure and deflection measurement. 1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific precautionary information is contained in Section 6.
Energy Technology Data Exchange (ETDEWEB)
Luna, N. [Direccion de Operacion Petrolera, Direccion General de Exploracion y Explotacion de Hidrocarburos, Secretaria de Energia, 03100 Mexico DF (Mexico); Mendez, F. [Facultad de Ingenieria, UNAM, 04510 Mexico DF (Mexico)
2005-07-01
The steady-state analysis of conjugated heat transfer process for the hydrodynamically developed forced convection flow on a heated flat plate embedded in a porous medium is studied. The governing equations for the fluid-saturated porous medium are solved analytically using the integral boundary layer approximation. This integral solution is coupled to the energy equation for the flat plate, where the longitudinal heat conduction effects are taken into account. The resulting equations are then reduced to an integro-differential equation which is solved by regular perturbation techniques and numerical methods. The analytical and numerical predictions for the temperature profile of the plate and appropriate local and average Nusselt numbers are plotted for finite values of the conduction parameter, {alpha}, which represents the presence of the longitudinal heat conduction effects. (authors)
Numerical analysis of flow and heat transfer behavior in fin-tube flat-plate solar collector
Institute of Scientific and Technical Information of China (English)
Namory Camara; LU Hui-lin
2007-01-01
Temperature distribution over the absorber plate of a parallel flow flat-plate solar collector is numerically analyzed. The governing differential equations with boundary conditions are solved numerically using fluent software. Effects of the inlet mass flux, inlet temperature and tube spacing on velocity and temperature distributions are discussed. Numerical results show that the distributions of velocity and temperature of fluid is unsymmetrical inside pipe.
Institute of Scientific and Technical Information of China (English)
孟显; 潘文霞; 张文宏; 吴承康
2001-01-01
By using steady and transient methods, the total heat fluxes and the distributions of the heat flux were measured experimentally for an argon DC laminar plasma jet impinging normally on a flat plate at atmospheric pressure. Results show that the total heat fluxes measured with a steady method are a little bit higher than those with a transient method. Numerical simulation work was executed to compare with the experimental results.
A. Malvandi; Faraz Hedayati; Ganji, D.D.
2015-01-01
The falling and settling of solid particles in gases and liquids is a natural phenomenon happens in many industrial processes. This phenomenon has altered pure forced convection to a combination of heat conduction and heat convection in a flow over a plate. In this paper, the coupling of conduction (inside the plate) and forced convection of a non-homogeneous nanofluid flow (over a flat plate) is investigated, which is classified in conjugate heat transfer problems. Two-component four-equatio...
Gallagher, B.; P. Alexander; D.Burger
1986-01-01
The Flat-Plate Solar Array (FSA) Project, funded by the U.S. Government and managed by the Jet Propulsion Laboratory, was formed in 1975 to develop the module/array technology needed to attain widespread terrestrial use of photovoltaics by 1985. To accomplish this, the FSA Project established and managed an Industry, University, and Federal Government Team to perform the needed research and development. The goal of the Process Development Area, as part of the FSA Project, was to develop ...
Effect of row-to-row shading on the output of flat-plate south-facing photovoltaic arrays
Energy Technology Data Exchange (ETDEWEB)
Goswami, D.Y.; Hassan, A.Y.; Collis, J. (North Carolina Agricultural and Technical State Univ., Greensboro, NC (USA)); Stefanakos, E.K. (University of South Florida, Tampa, FL (USA))
1989-08-01
When solar arrays (photovoltaic, thermal, etc.) are arranged in multiple rows of modules, all but the first row suffer reduction in (power) output, even when sufficient spacing between rows is provided. The reduction in output power occurs because the first row prevents some of the diffuse and reflected radiation from reaching the row directly behind it. This work presents estimates of the effect of shading on the amounts of solar radiation received by consecutive rows of flat-plate arrays.
Energy Technology Data Exchange (ETDEWEB)
Ferg, E.E.; Loyson, P. [Department of Chemistry, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031 (South Africa); Poorun, A. [Willard Batteries, P.O. Box 1844, Port Elizabeth 6000 (South Africa)
2006-04-21
The study looked at the use of red lead in the manufacturing of valve regulated lead acid (VRLA) miners cap lamp (MCL) batteries that were made with either flat plate or tubular positive electrodes. A problem with using only grey oxide in the manufacture of thick flat plate or tubular electrodes is the poor conversion of the active material to the desired lead dioxide. The addition of red lead to the initial starting material improves the formation efficiency but is considerably more expensive thereby increasing the cost of manufacturing. The study showed that by carefully controlling the formation conditions in terms of the voltage and temperature of a battery, good capacity performance can be achieved for cells made with flat plate electrodes that contain up to 25% red lead. The small amount of red lead in the active cured material reduces the effect of electrode surface sulphate formation and allows the battery to achieve its rated capacity within the first few cycles. Batteries made with flat plate positive electrodes that contained more that 50% red lead showed good initial capacity but had poor structural active material bonding. The study showed that MCL batteries made with tubular positive electrodes that contained less than 75% red lead resulted in a poorly formed electrode with limited capacity utilization. Pickling and soaking times of the tubular electrodes should be kept at a minimum thereby allowing higher active material utilization during subsequent capacity cycling. The study further showed that it is beneficial to use higher formation rates in order to reduce manufacturing time and to improve the active material characteristics. (author)
Use of a rotating cylinder to induce laminar and turbulent separation over a flat plate
Afroz, F.; Lang, A.; Jones, E.
2017-06-01
An innovative and easy technique using a rotating cylinder system has been implemented in a water tunnel experiment to generate an adverse pressure gradient (APG). The strength of the APG was varied through adjustment in the rotation speed and location of the cylinder. Then the technique was used for inducing a laminar separation bubble (LSB) and turbulent boundary layer (TBL) separation over a flat plate. A theoretical model to predict the pressure variation induced on the plate consists of an inviscid flow over a reverse doublet-like configuration of two counter rotating cylinders. This model quantified the pressure distribution with changes of cylinder speed and location. The dimensionless velocity ratio (VR) of the cylinder rotation rate to the mainstream velocity and gap to diameter ratio \\tfrac{G}{D} were chosen as the two main ways of varying the strength of the APG, which affects the nature and extent of the LSB as well as TBL separation. The experimental parametric study, using time-resolved digital particle image velocimetry, was then conducted in a water tunnel. The variation in height (h), length (l), and the separation point (S) of the LSB was documented due to the variation in the APG. The similar type of experimental parametric study was used to explore the unsteady, turbulent separation bubble in a 2D plane aligned with the flow and perpendicular to the plate. The mean detachment locations of TBL separation are determined by two different definitions: (i) back-flow coefficient (χ) = 50%, and (ii) location of start of negative mean skin friction coefficient (C f). They are in good agreement and separation bubble characteristics agreed well with results obtained using different methods thus proving the validity of the technique.
Analysis of PV/T flat plate water collectors connected in series
Energy Technology Data Exchange (ETDEWEB)
Dubey, Swapnil; Tiwari, G.N. [Centre for Energy Studies, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016 (India)
2009-09-15
Photovoltaic-thermal (PV/T) technology refers to the integration of a PV and a conventional solar thermal collector in a single piece of equipment. In this paper we evaluate the performance of partially covered flat plate water collectors connected in series using theoretical modeling. PV is used to run the DC motor, which circulates the water in a forced mode. Analytical expressions for N collectors connected in series are derived by using basic energy balance equations and computer based thermal models. This paper shows the detailed analysis of thermal energy, exergy and electrical energy yield by varying the number of collectors by considering four weather conditions (a, b, c and d type) for five different cities (New Delhi, Bangalore, Mumbai, Srinagar, and Jodhpur) of India. Annual thermal and electrical energy yield is also evaluated for four different series and parallel combination of collectors for comparison purpose considering New Delhi conditions. This paper also gives the total carbon credit earned by the hybrid PV/T water heater investigated as per norms of Kyoto Protocol for New Delhi climatic conditions. Cost analysis has also been carried out. It is observed that the collectors partially covered by PV module combines the production of hot water and electricity generation and it is beneficial for the users whose primary requirement is hot water production and collectors fully covered by PV is beneficial for the users whose primary requirement is electricity generation. We have also found that if this type of system is installed only in 10% of the total residential houses in Delhi then the total carbon credit earned by PV/T water heaters in terms of thermal energy is USD $144.5 millions per annum and in terms of exergy is USD $14.3 millions per annum, respectively. (author)
1976-01-01
Basic test results of a flat-plate solar collector whose performance was determined in the NASA-Lewis solar simulator are given. The collector was tested over ranges of inlet temperature and flux level.
Min, Booki; Logan, Bruce E
2004-11-01
A microbial fuel cell (MFC) is a device that converts organic matter to electricity using microorganisms as the biocatalyst. Most MFCs contain two electrodes separated into one or two chambers that are operated as a completely mixed reactor. In this study, a flat plate MFC (FPMFC) was designed to operate as a plug flow reactor (no mixing) using a combined electrode/proton exchange membrane (PEM) system. The reactor consisted of a single channel formed between two nonconductive plates that were separated into two halves by the electrode/PEM assembly. Each electrode was placed on an opposite side of the PEM, with the anode facing the chamber containing the liquid phase and the cathode facing a chamber containing only air. Electricity generation using the FPMFC was examined by continuously feeding a solution containing wastewater, or a specific substrate, into the anode chamber. The system was initially acclimated for 1 month using domestic wastewater orwastewater enriched with a specific substrate such as acetate. Average power density using only domestic wastewater was 72+/-1 mW/m2 at a liquid flow rate of 0.39 mL/min [42% COD (chemical oxygen demand) removal, 1.1 h HRT (hydraulic retention time)]. At a longer HRT = 4.0 h, there was 79% COD removal and an average power density of 43+/-1 mW/m2. Power output was found to be a function of wastewater strength according to a Monod-type relationship, with a half-saturation constant of Ks = 461 or 719 mg COD/L. Power generation was sustained at high rates with several organic substrates (all at approximately 1000 mg COD/L), including glucose (212+/-2 mW/ m2), acetate (286+/-3 mW/m2), butyrate (220+/-1 mW/ m2), dextran (150+/-1 mW/m2), and starch (242+/-3 mW/ m2). These results demonstrate the versatility of power generation in a MFC with a variety of organic substrates and show that power can be generated at a high rate in a continuous flow reactor system.
Status of the NASA-Lewis flat-plate collector tests with a solar simulator
Simon, F. F.
1974-01-01
Simulator test results of 15 collector types are reported. Collectors are given performance ratings according to their use for pool heating, hot water, absorption A/C or heating and solar Rankine machines. Collectors found to be good performers in the above categories, except for pool heating, were a black nickel coated, 2 glass collector, and a black paint 2 glass collector containing a mylar honeycomb. For pool heating, a black paint, one glass collector was found to be the best performer. Collector performance parameters of 5 collector types were determined to aid in explaining the factors that govern performance. The two factors that had the greatest effect on collector performance were the collector heat loss and the coating absorptivity.
Influence of wire-coil inserts on the thermo-hydraulic performance of a flat-plate solar collector
Herrero Martín, R.; García, A.; Pérez-García, J.
2012-11-01
Enhancement techniques can be applied to flat-plate liquid solar collectors towards more compact and efficient designs. For the typical operating mass flow rates in flat-plate solar collectors, the most suitable technique is inserted devices. Based on previous studies from the authors, wire coils were selected for enhancing heat transfer. This type of inserted device provides better results in laminar, transitional and low turbulence fluid flow regimes. To test the enhanced solar collector and compare with a standard one, an experimental side-by-side solar collector test bed was designed and constructed. The testing set up was fully designed following the requirements of EN12975-2 and allow us to accomplish performance tests under the same operating conditions (mass flow rate, inlet fluid temperature and weather conditions). This work presents the thermal efficiency curves of a commercial and an enhanced solar collector, for the standardized mass flow rate per unit of absorber area of 0.02 kg/sm2 (in useful engineering units 144 kg/h for water as working fluid and 2 m2 flat-plate solar collector of absorber area). The enhanced collector was modified inserting spiral wire coils of dimensionless pitch p/D = 1 and wire-diameter e/D = 0.0717. The friction factor per tube has been computed from the overall pressure drop tests across the solar collectors. The thermal efficiency curves of both solar collectors, a standard and an enhanced collector, are presented. The enhanced solar collector increases the thermal efficiency by 15%. To account for the overall enhancement a modified performance evaluation criterion (R3m) is proposed. The maximum value encountered reaches 1.105 which represents an increase in useful power of 10.5% for the same pumping power consumption.
DEFF Research Database (Denmark)
Taherian, Hessam; Yazdanshenas, Eshagh
2006-01-01
Due to scarcity of literature on forced-convection heat transfer in a solar collector with rhombic cross-section absorbing tubes, a series of experiments was arranged and conducted to determine heat transfer coefficient. In this study, a typical rhombic cross-section finned tube of flat......-plate collectors used as the test section. Two correlations were proposed for the Nusselt number as a function of the Reynolds number and the Prandtl number based on hydraulic diameter for various heat fluxes. The temperature distribution along the finned tube for the fluid and the wall were also illustrated....
Christensen, Elmer
1985-01-01
The Flat-Plate Solar Array (FSA) Project, a Government-sponsored photovoltaics project, was initiated in January 1975 (previously named the Low-Cost Silicon Solar Array Project) to stimulate the development of PV systems for widespread use. Its goal then was to develop PV modules with 10% efficiency, a 20-year lifetime, and a selling price of $0.50 per peak watt of generating capacity (1975 dollars). It was recognized that cost reduction of PV solar-cell and module manufacturing was the key achievement needed if PV power systems were to be economically competitive for large-scale terrestrial use.
HEAT AND MASS TRANSFER FOR VISCO-ELASTIC MHD BOUNDARY LAYER FLOW PAST A VERTICAL FLAT PLATE
Directory of Open Access Journals (Sweden)
Rita Choudhury
2012-07-01
Full Text Available The two-dimensional free convection flow of visco-elastic and electrically conducting fluid past a vertical impermeable flat plate is considered in presence of a uniform transverse magnetic field. The governing equations are reduced to ordinary differential equation by introducing appropriate co-ordinate transformation. The analytical expressions for the velocity, temperature and species concentration fields have been obtained. The corresponding expressions for the non-dimensional rates of heat transfer and mass transfer have beenobtained. The velocity profile and the shearing stress have been illustrated graphically, for various values of flow parameters involved in the solution to observe the effect of visco-elastic parameter.
Directory of Open Access Journals (Sweden)
Dr. G. Prabhakara Rao,
2015-04-01
Full Text Available We consider a two-dimensional MHD natural convection flow of an incompressible viscous and electrically conducting fluid through porous medium past a vertical impermeable flat plate is considered in presence of a uniform transverse magnetic field. The governing equations of velocity and temperature fields with appropriate boundary conditions are solved by the ordinary differential equations by introducing appropriate coordinate transformations. We solve that ordinary differential equations and find the velocity profiles, temperature profile, the skin friction and nusselt number. The effects of Grashof number (Gr, Hartmann number (M and Prandtl number (Pr, Darcy parameter (D-1 on velocity profiles and temperature profiles are shown graphically.
Reshetova, A. I.; Poplavskaya, T. V.
2016-10-01
The problem of disturbances evolution in a hypersonic viscous shock layer on a flat plate is considered. Numerical simulation was performed by solving 2D Navier-Stokes equations using the ANSYS Fluent software package within the model of thermally perfect gas. The change of vibrational energy was simulated by the Landau-Teller equation, in which the finite time of vibrational relaxation of CO2 molecules was taken into account. The quantitative data on the effect of vibrational relaxation of CO2 molecules on the evolution of acoustic disturbances in the shock layer on a plate is obtained.
Ayompe, Lacour; DUFFY Aidan
2013-01-01
The thermal performance of a solar water heating system with 4 m2 flat plate collectors in Dublin, Ireland is presented in this paper. The experimental setup consisted of a commercially available forced circulation domestic scale system fitted with an automated sub‐system that controlled hot water draw‐offs and the operation of an auxiliary immersion heater. The system was tested over a year and the maximum recorded collector outlet fluid temperature was 70.4 oC while the maximum water temper...
Bhuiyan, A. S.; Biswas, M. R.
2011-11-01
The effects of pressure stress work and viscous dissipation in mixed convection flow along a vertical flat plate have been investigated. The results are obtained numerically by transforming the governing system of boundary layer equations into a system of non-dimensional equations. Numerical results for different values of pressure stress work parameter, viscous dissipation parameter, and Prandtl number have been obtained. The velocity profiles, temperature distributions, skin friction coefficient, and the rate of heat transfer have been presented graphically for the effects of the aforementioned parameters. Results are compared with previous investigation.
PERFORMANCE DETERIORATION OF THERMOSIPHON SOLAR FLAT PLATE WATER HEATER DUE TO SCALING
Directory of Open Access Journals (Sweden)
arunachala umesh chandavar
2011-12-01
Full Text Available 0 0 1 340 1943 International Islamic University 16 4 2279 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Times New Roman";} The performance of Flat plate Solar Water Heater deteriorates within five to twelve years of their installation due to factors related to manufacturing, operating conditions, lack of maintenance etc. Especially, problem due to scaling is significant as it is based on quality of water used. The remaining factors are system dependent and could be overcome by quality production. Software is developed by incorporating Hottel Whillier Bliss (H-W-B equation to ascertain the effect of scaling on system efficiency in case of thermosiphon system. In case of clean thermosiphon system, the instantaneous efficiency calculated at 1000 W/m2 radiation is 72 % and it drops to 46 % for 3.7 mm scale thickness. The mass flow rate is reduced by 90 % for 3.7 mm scale thickness. Whereas, the average temperature drop of water in the tank is not critical due to considerable heat content in water under severe scaled condition. But practically in case of major scale growth, some of the risers are likely to get blocked completely which leads to negligible temperature rise in the tank. ABSTRAK: Prestasi plat rata pemanas air suria merosot selepas lima hingga dua belas tahun pemasangannya disebabkan faktor-faktor yang berkaitan dengan pembuatannya, cara kendaliannya, kurangnya penyelenggaraan dan sebagainya. Terutama sekali, masalah disebabkan scaling (tembunan endapan mineral perlu diambil berat kerana ianya bergantung kepada kualiti air yang digunakan. Faktor-faktor selebihya bersandarkan sistem dan ia
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Perović Bojan D.
2017-01-01
Full Text Available The main purpose of this paper is to show how the inclination angle affects natural convection from a flat-plate photovoltaic module which is mounted on the ground surface. In order to model this effect, novel correlations for natural convection from isothermal flat plates are developed by using the fundamental dimensionless number. On the basis of the available experimental and numerical results, it is shown that the natural convection correlations correspond well with the existing empirical correlations for vertical, inclined, and horizontal plates. Five additional correlations for the critical Grashof number are derived from the available data, three indicating the onset of transitional flow regime and two indicating the onset of flow separation. The proposed correlations cover the entire range of inclination angles and the entire range of Prandtl numbers. This paper also provides two worked examples, one for natural convection combined with radiation and one for natural convection combined with forced convection and radiation. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR33046
Energy Technology Data Exchange (ETDEWEB)
Borden, C.S.; Volkmer, K.; Cochrane, E.H.; Lawson, A.C.
1984-05-01
A simple methodology to estimate photovoltaic system size and life-cycle costs in stand-along applications is presented in this document. It is designed to assist engineers at government agencies in determining the feasibility of using small stand-alone photovoltaic systems to supply ac or dc power to the load. Photovoltaic system design considerations are presented as well as the equations for sizing the flat-plate array and the battery storage to meet the required load. Cost effectiveness of a candidate photovoltaic system is based on comparison with the life-cycle cost of alternative systems. Examples of alternative systems addressed herein are batteries, diesel generators, the utility grid, and other renewable energy systems. A companion document, Flat-Plate Photovoltaic Power Systems Handbook for Federal Agencies (Reference 10), is recommended for discussion of issues for evaluating the viability of potential photovoltaic applications; descriptions of present photovoltaic system applications; synthesis of lessons learned from photovoltaic system design, installation, and operation; and identification of procurement strategies for federal agencies.
Creager, Marcus O.
1959-01-01
An investigation of the effects of variation of leading-edge sweep and surface inclination on the flow over blunt flat plates was conducted at Mach numbers of 4 and 5.7 at free-stream Reynolds numbers per inch of 6,600 and 20,000, respectively. Surface pressures were measured on a flat plate blunted by a semicylindrical leading edge over a range of sweep angles from 0 deg to 60 deg and a range of surface inclinations from -10 deg to +10 deg. The surface pressures were predicted within an average error of +/- 8 percent by a combination of blast-wave and boundary-layer theory extended herein to include effects of sweep and surface inclination. This combination applied equally well to similar data of other investigations. The local Reynolds number per inch was found to be lower than the free-stream Reynolds number per inch. The reduction in local Reynolds number was mitigated by increasing the sweep of the leading edge. Boundary-layer thickness and shock-wave shape were changed little by the sweep of the leading edge.
Long, J.; New, T. H.
2016-07-01
Vortical structures and dynamics of a Re h = 2100 elliptic jet impinging upon a flat plate were studied at H/ d h = 1, 2 and 4 jet-to-plate separation distances. Flow investigations were conducted along both its major and minor planes using laser-induced fluorescence and digital particle image velocimetry techniques. Results show that the impingement process along the major plane largely consists of primary jet ring-vortex and wall-separated secondary vortex formations, where they subsequently separate from the flat plate at smaller H/ d h = 1 and 2 separation distances. Key vortex formation locations occur closer to the impingement point as the separation distance increases. Interestingly, braid vortices and rib structures begin to take part in the impingement process at H/ d h = 4 and wave instabilities dominate the flow field. In contrast, significantly more coherent primary and secondary vortices with physically larger vortex core sizes and higher vortex strengths are observed along the minor plane, with no signs of braid vortices and rib structures. Lastly, influences of these different flow dynamics on the major and minor plane instantaneous and mean skin friction coefficient levels are investigated to shed light on the effects of separation distance on the wall shear stress distributions.
Energy Technology Data Exchange (ETDEWEB)
Toyama, Y. [Mitsui Engineering and Shipbuilding Co. Ltd., Tokyo (Japan)
1996-12-31
A slamming load generated by interactive motions between a ship body and water face is an important load in ensuring safety of the ship. A flat plate approximation developed by Wagner is used as a two-dimensional slamming theory, but it has a drawback in handling edges of a flat plate. Therefore, an attempt was made to expand the two-dimensional Wagner`s theory to three dimensions. This paper first shows a method to calculate water face slamming of an arbitrary axisymmetric body by using circular plate approximation. The paper then proposes a method to calculate slamming pressure distribution and slamming force for the case when shape of the water contacting surface may be approximated by an elliptic shape. Expansion to the three dimensions made clear to some extent the characteristics of the three-dimensional slamming. In the case of two dimensions or a circular column for example, the water contacting area increases rapidly in the initial stage generating large slamming force. However, in the case of three dimensions, since the water contacting area expands longitudinally and laterally, the slamming force tends to increase gradually. Maximum slamming pressure was found proportional to square of moving velocity in a water contacting boundary in the case of three dimensions, and similar to stagnation pressure on a gliding plate. 12 refs., 17 figs., 1 tab.
Ambarita, Himsar; Kishinami, Koki; Daimaruya, Mashashi; Tokura, Ikuo; Kawai, Hideki; Suzuki, Jun; Kobiyama, Mashayosi; Ginting, Armansyah
The present paper is a study on the optimum plate to plate spacing for maximum heat transfer rate from a flat plate type heat exchanger. The heat exchanger consists of a number of parallel flat plates. The working fluids are flowed at the same operational conditions, either fixed pressure head or fixed fan power input. Parallel and counter flow directions of the working fluids were considered. While the volume of the heat exchanger is kept constant, plate number was varied. Hence, the spacing between plates as well as heat transfer rate will vary and there exists a maximum heat transfer rate. The objective of this paper is to seek the optimum plate to plate spacing for maximum heat transfer rate. In order to solve the problem, analytical and numerical solutions have been carried out. In the analytical solution, the correlations of the optimum plate to plate spacing as a function of the non-dimensional parameters were developed. Furthermore, the numerical simulation is carried out to evaluate the correlations. The results show that the optimum plate to plate spacing for a counter flow heat exchanger is smaller than parallel flow ones. On the other hand, the maximum heat transfer rate for a counter flow heat exchanger is bigger than parallel flow ones.
Heat Loss Calculation of Compound Honeycomb Solar Collector
Institute of Scientific and Technical Information of China (English)
X.S.Ge; Y.Z.Zhang; 等
1993-01-01
A simplified technique is described for calculating the heat loss coefficient from the absorber of the solar flat-plate collector with a combined honeycomb.The problem is treated in two ways:the coupled mode and the decoupled mode.In the analysis,the cell wall and glass cover are assumed to be specularly reflecting and diffusely emitting surfaces,while the absorber is a diffusely reflecting and emitting surface.The influences of emissivities of the absorber and the cell wall as wall as well as the aspect ratio on the heat loss coefficient are predicted.The theoretical results are compared with experimental data reported in the literature,and the agreement is good.
Heat Transfer to Vertical Flat Plates in a Rectangular Gas-Fluidized Bed.
1984-06-01
it. These taps were connected by flexible plastic tubing to a manifold 6 29 61 which permitted selective connection of the taps to a Meriam Model...Spencer Turbine 550 SCFM Turbo Compressor Rotometer Fisher & Porter 34 SCFM 30-Inch Meriam 33KA35 A69513 Water Manometer Computer Hewlett-Packard HP 85
The flat-plate plant-microbial fuel cell: the effect of a new design on internal resistances
Directory of Open Access Journals (Sweden)
Helder Marjolein
2012-09-01
Full Text Available Abstract Due to a growing world population and increasing welfare, energy demand worldwide is increasing. To meet the increasing energy demand in a sustainable way, new technologies are needed. The Plant-Microbial Fuel Cell (P-MFC is a technology that could produce sustainable bio-electricity and help meeting the increasing energy demand. Power output of the P-MFC, however, needs to be increased to make it attractive as a renewable and sustainable energy source. To increase power output of the P-MFC internal resistances need to be reduced. With a flat-plate P-MFC design we tried to minimize internal resistances compared to the previously used tubular P-MFC design. With the flat-plate design current and power density per geometric planting area were increased (from 0.15 A/m2 to 1.6 A/m2 and from 0.22 W/m2 to and 0.44 W/m2as were current and power output per volume (from 7.5 A/m3 to 122 A/m3 and from 1.3 W/m3 to 5.8 W/m3. Internal resistances times volume were decreased, even though internal resistances times membrane surface area were not. Since the membrane in the flat-plate design is placed vertically, membrane surface area per geometric planting area is increased, which allows for lower internal resistances times volume while not decreasing internal resistances times membrane surface area. Anode was split into three different sections on different depths of the system, allowing to calculate internal resistances on different depths. Most electricity was produced where internal resistances were lowest and where most roots were present; in the top section of the system. By measuring electricity production on different depths in the system, electricity production could be linked to root growth. This link offers opportunities for material-reduction in new designs. Concurrent reduction in material use and increase in power output brings the P-MFC a step closer to usable energy density and economic feasibility.
Madavan, Nateri K.
1995-01-01
The work in this report was conducted at NASA Ames Research Center during the period from August 1993 to January 1995 deals with the direct numerical simulation of transitional and turbulent flow at low Mach numbers using high-order-accurate finite-difference techniques. A computation of transition to turbulence of the spatially-evolving boundary layer on a heated flat plate in the presence of relatively high freestream turbulence was performed. The geometry and flow conditions were chosen to match earlier experiments. The development of the momentum and thermal boundary layers was documented. Velocity and temperature profiles, as well as distributions of skin friction, surface heat transfer rate, Reynolds shear stress, and turbulent heat flux were shown to compare well with experiment. The numerical method used here can be applied to complex geometries in a straightforward manner.
Institute of Scientific and Technical Information of China (English)
R. TRˆIMBIT¸AS¸; T.GROSAN; I.POP
2015-01-01
An analysis is carried out to investigate the steady mixed convection bound-ary layer flow of a water based nanofluid past a vertical semi-infinite flat plate. Using an appropriate similarity transformation, the governing partial differential equations are transformed into the coupled, nonlinear ordinary (similar) differential equations, which are then solved numerically for the Prandtl number Pr = 6.2. The skin friction coeﬃ-cient, the local Nusselt number, and the velocity and temperature profiles are presented graphically and discussed. Effects of the solid volume fractionφand the mixed convection parameterλon the fluid flow and heat transfer characteristics are thoroughly examined. Different from an assisting flow, it is found that the solutions for an opposing flow are non-unique. In order to establish which solution branch is stable and physically realizable in practice, a stability analysis is performed.
Institute of Scientific and Technical Information of China (English)
SU CaiHong
2012-01-01
The transition criterion in the improved eN method is that transition would occur whenever the velocity amplitude of disturbance reaches 1％-2％ of the free stream velocity,while in the conventional eN method,the N factor is an empirical factor.In this paper the reliability of this key assumption in the improved eN method is checked by results of transition prediction by using the Parabolized Stability Equations (PSE).Transition locations of an incompressible boundary layer and a hypersonic boundary layer at Mach number 6 on a flat plate are predicted by both the improved eN method and the PSE method.Results from both methods agree fairly well with each other,implying that the transition criterion proposed in the improved eN method is reliable.
Phillips, M. J.
1986-01-01
Abstracts of final reports, or the latest quarterly or annual, of the Flat-Plate Solar Array (FSA) Project Contractor of Jet Propulsion Laboratory (JPL) in-house activities are presented. Also presented is a list of proceedings and publications, by author, of work connected with the project. The aim of the program has been to stimulate the development of technology that will enable the private sector to manufacture and widely use photovoltaic systems for the generation of electricity in residential, commercial, industrial, and Government applications at a cost per watt that is competitive with utility generated power. FSA Project activities have included the sponsoring of research and development efforts in silicon refinement processes, advanced silicon sheet growth techniques, higher efficiency solar cells, solar cell/module fabrication processes, encapsulation, module/array engineering and reliability, and economic analyses.
Rashidi, Mohammad M; Kavyani, Neda; Abelman, Shirley; Uddin, Mohammed J; Freidoonimehr, Navid
2014-01-01
In this study combined heat and mass transfer by mixed convective flow along a moving vertical flat plate with hydrodynamic slip and thermal convective boundary condition is investigated. Using similarity variables, the governing nonlinear partial differential equations are converted into a system of coupled nonlinear ordinary differential equations. The transformed equations are then solved using a semi-numerical/analytical method called the differential transform method and results are compared with numerical results. Close agreement is found between the present method and the numerical method. Effects of the controlling parameters, including convective heat transfer, magnetic field, buoyancy ratio, hydrodynamic slip, mixed convective, Prandtl number and Schmidt number are investigated on the dimensionless velocity, temperature and concentration profiles. In addition effects of different parameters on the skin friction factor, [Formula: see text], local Nusselt number, [Formula: see text], and local Sherwood number [Formula: see text] are shown and explained through tables.
Hasheminejad, S.M.
2017-04-03
Development of streamwise counter-rotating vortices induced by leading edge patterns with different pattern shape is investigated using hot-wire anemometry in the boundary layer of a flat plate. A triangular, sinusoidal and notched patterns with the same pattern wavelength λ of 15mm and the same pattern amplitude A of 7.5mm were examined for free-stream velocity of 3m/s. The results show a good agreement with earlier studies. The inflection point on the velocity profile downstream of the trough of the patterns at the beginning of the vortex formation indicates that the vortices non-linearly propagate downstream. An additional vortex structure was also observed between the troughs of the notched pattern.
Sforza, Eleonora; Calvaruso, Claudio; Meneghesso, Andrea; Morosinotto, Tomas; Bertucco, Alberto
2015-10-01
In this work, Nannochloropsis salina was cultivated in a continuous-flow flat-plate photobioreactor, working at different residence times and irradiations to study the effect of the specific light supply rate on biomass productivity and photosynthetic efficiency. Changes in residence times lead to different steady-state cell concentrations and specific growth rates. We observed that cultures at steady concentration were exposed to different values of light intensity per cell. This specific light supply rate was shown to affect the photosynthetic status of the cells, monitored by fluorescence measurements. High specific light supply rate can lead to saturation and photoinhibition phenomena if the biomass concentration is not optimized for the selected operating conditions. Energy balances were applied to quantify the biomass growth yield and maintenance requirements in N. salina cells.
On an ill-posed model of oscillations of a flat plate with a variety of mounts on opposite sides
Iskakova, Ulzada A.
2016-08-01
In this paper, we consider a model case of stationary vibrations of a thin flat plate, one side of which is embedded, the opposite side is free, and the sides are freely leaned. In mathematical modeling, there is a local boundary value problem for the biharmonic equation in a rectangular domain. Boundary conditions are given on all boundary of the domain. We show that the considered problem is self-adjoint. Herewith, the problem is ill-posed. We show that the stability of solution to the problem is disturbed. Necessary and sufficient conditions of existence of the problem solution are found. Spaces of the ill-posedness of the considered problem are constructed.
On a model of oscillations of a thin flat plate with a variety of mounts on opposite sides
Kal'menov, Tynysbek; Iskakova, Ulzada
2016-12-01
In this paper we consider a model case of stationary vibrations of a thin flat plate, one side of which is embedded, the opposite side is free, and the sides are freely leaned. In mathematical modeling there is a local boundary value problem for the biharmonic equation in a rectangular domain. Boundary conditions are given on all boundary of the domain. We show that the considered problem is self-adjoint. Herewith the problem is ill-posed. We show that the stability of solution to the problem is disturbed. Necessary and sufficient conditions of existence of the problem solution are found. Spaces of the ill-posedness of the considered problem are constructed.
Yokoyama, Tomoki; Takahashi, Kumiko; Seki, Daizaburou; Hasegawa, Akio
2002-05-01
The acoustic intensity distribution and radiation power of a flat-plate phased-array sound source consisting of Tonpilz-type transducers were measured. This study shows that the active acoustic intensity is skewed in the direction of wave propagation. In addition, it clarifies that if the measurement is carried out in the immediate vicinity of the sound source, the reactive acoustic intensity distribution is effective for identifying the positions of the individual sound source elements. Experimental values of active radiation power agree well with theoretical values. Conversely, experimental values of reactive radiation power do not agree with theoretical values; it is clear that they fluctuate significantly with distance from the radiating surface. The reason for this is explained in the case of a point sound source.
Directory of Open Access Journals (Sweden)
Norfifah Bachok
Full Text Available The steady boundary layer flow of a viscous and incompressible fluid over a moving vertical flat plate in an external moving fluid with viscous dissipation is theoretically investigated. Using appropriate similarity variables, the governing system of partial differential equations is transformed into a system of ordinary (similarity differential equations, which is then solved numerically using a Maple software. Results for the skin friction or shear stress coefficient, local Nusselt number, velocity and temperature profiles are presented for different values of the governing parameters. It is found that the set of the similarity equations has unique solutions, dual solutions or no solutions, depending on the values of the mixed convection parameter, the velocity ratio parameter and the Eckert number. The Eckert number significantly affects the surface shear stress as well as the heat transfer rate at the surface.
Directory of Open Access Journals (Sweden)
Park Dong-Woo
2015-01-01
Full Text Available Flat plate friction lines hare been used in the process to estimate speed performance of full-scale ships in model tests. The results of the previous studies showed considerable differences in determining form factors depending on changes in plate friction lines and Reynolds numbers. These differences had a great influence on estimation of speed performance of full-scale ships. This study- was conducted in two parts. In the first part, the scale effect of the form factor depending on change in the Reynolds number was studied based on CFD, in connection with three kinds of friction resistance curves: the ITTC-1957, the curve proposed by Grigson (1993; 1996, and the curve developed by Katsui et al (2005. In the second part, change in the form factor by three kinds of
An Explicit,Totally Analytic Solution of Laminar Viscous FLow over a Semi—Infinite Flat Plate
Institute of Scientific and Technical Information of China (English)
Shi－JunLIAO
1998-01-01
In this paper,a new kind of analytic technique for nonlinear problems,namely the Homotopy Analysis Method,is applied to give an explicit,totally analytic solution of the Blasius' flow.i.e.,the two dimensional (2D) laminar viscous flow over a semi-infinite flat plate.This analytic solution is valid in the whole region having physical meanings.To our knowledge,it is the first time in history that such a kind of explicit,totally analytic solution is given.This fact well verifies the great potential and validity of the Honmotopy Analysis Method as a kind of powerful analytic tool for nonlinear problems in science and engineering.
An experimental study of tip shape effects on the flutter of aft-swept, flat-plate wings
Dansberry, Bryan E.; Rivera, Jose A., Jr.; Farmer, Moses G.
1990-01-01
The effects of tip chord orientation on wing flutter are investigated experimentally using six cantilever-mounted, flat-plate wing models. Experimentally determined flutter characteristics of the six models are presented covering both the subsonic and transonic Mach number ranges. While all models have a 60 degree leading edge sweep, a 40.97 degree trailing edge sweep, and a root chord of 34.75 inches, they are subdivided into two series characterized by a higher aspect ratio and a lower aspect ratio. Each series is made up of three models with tip chord orientations which are parallel to the free-stream flow, perpendicular to the model mid-chord line, and perpendicular to the free-stream flow. Although planform characteristics within each series of models are held constant, structural characteristics such as mode shapes and natural frequencies are allowed to vary.
Borden, C. S.; Volkmer, K.; Cochrane, E. H.; Lawson, A. C.
1984-01-01
A simple methodology to estimate photovoltaic system size and life-cycle costs in stand-alone applications is presented. It is designed to assist engineers at Government agencies in determining the feasibility of using small stand-alone photovoltaic systems to supply ac or dc power to the load. Photovoltaic system design considerations are presented as well as the equations for sizing the flat-plate array and the battery storage to meet the required load. Cost effectiveness of a candidate photovoltaic system is based on comparison with the life-cycle cost of alternative systems. Examples of alternative systems addressed are batteries, diesel generators, the utility grid, and other renewable energy systems.
Directory of Open Access Journals (Sweden)
R. Venkata Rao
2015-12-01
Full Text Available This paper presents the performance of teaching–learning-based optimization (TLBO algorithm to obtain the optimum set of design and operating parameters for a smooth flat plate solar air heater (SFPSAH. The TLBO algorithm is a recently proposed population-based algorithm, which simulates the teaching–learning process of the classroom. Maximization of thermal efficiency is considered as an objective function for the thermal performance of SFPSAH. The number of glass plates, irradiance, and the Reynolds number are considered as the design parameters and wind velocity, tilt angle, ambient temperature, and emissivity of the plate are considered as the operating parameters to obtain the thermal performance of the SFPSAH using the TLBO algorithm. The computational results have shown that the TLBO algorithm is better or competitive to other optimization algorithms recently reported in the literature for the considered problem.
Institute of Scientific and Technical Information of China (English)
M.A.R.Akhanda
2000-01-01
Experimental study of natural convection heat transfer across air layers bounded by a lower hot rectangular and a square corrugated plates to an upper cold flat plate has been carried out.The surroundings of this space are adiabatic.The effect of the angle of inclination,the aspect ratio,the temperature potential and the Rayleigh number on average heat transfer coefficients are investigated within a range of 0°≤θ≤75°,2.33≤A≤6.33,10°≤ΔT≤35°，and 3.29×104≤RaL≤2.29×106,The developed correlation predicts well the experimental data within an error of ±15%.
Rashidi, Mohammad M.; Kavyani, Neda; Abelman, Shirley; Uddin, Mohammed J.; Freidoonimehr, Navid
2014-01-01
In this study combined heat and mass transfer by mixed convective flow along a moving vertical flat plate with hydrodynamic slip and thermal convective boundary condition is investigated. Using similarity variables, the governing nonlinear partial differential equations are converted into a system of coupled nonlinear ordinary differential equations. The transformed equations are then solved using a semi-numerical/analytical method called the differential transform method and results are compared with numerical results. Close agreement is found between the present method and the numerical method. Effects of the controlling parameters, including convective heat transfer, magnetic field, buoyancy ratio, hydrodynamic slip, mixed convective, Prandtl number and Schmidt number are investigated on the dimensionless velocity, temperature and concentration profiles. In addition effects of different parameters on the skin friction factor, , local Nusselt number, , and local Sherwood number are shown and explained through tables. PMID:25343360
Energy Technology Data Exchange (ETDEWEB)
Hess, S.; Oliva, A.; Di Lauro, P.; Klemke, M.; Hermann, M.; Stryi-Hipp, G. [Fraunhofer-Institut fuer Solare Energiesysteme ISE, Freiburg (Germany); Kallwellis, V.; Kramp, G.; Eisenmann, W. [Wagner und Co. Solartechnik GmbH, Coelbe (Germany); Hanby, V. [DMU Leicester (United Kingdom). Inst. of Energy and Sustainable Development
2010-07-01
In cooperation with the Fraunhofer Institute for Solar Energy Systems (Freiburg, Federal Republic of Germany), the company Wagner and Co. Solar Technology (Coelbe, Federal Republic of Germany) developed a stationary concentrated, double-covered flat plate collector with an external reflector for generating process heat up to a temperature of 150 C. This prototype has a half-CPC reflector which is approximated by three flat segments. The reflectors use the distance between the collectors and serves simultaneously as a supporting structure. The collector is designed so that the aperture is not shaded. The authors of the contribution under consideration present the WKI curves and the IAM curves as a test pattern as well as a simulation of the annual energy yield. According to the simulation, the Reflec-collector has an annual energy yield which is greater by 64 % than that of the double-covered base-collector.
Huang, Jianke; Feng, Fei; Wan, Minxi; Ying, Jiangguo; Li, Yuanguang; Qu, Xiaoxing; Pan, Ronghua; Shen, Guomin; Li, Wei
2015-04-01
A novel mixer was developed to improve the performance of flat-plate photobioreactors (PBRs). The effects of mixer were theoretically evaluated using computational fluid dynamics (CFD) according to radial velocity of fluid and light/dark cycles within reactors. The structure parameters, including the riser width, top clearance, clearance between the baffles and walls, and number of the chambers were further optimized. The microalgae culture test aiming at validating the simulated results was conducted indoor. The results showed the maximum biomass concentrations in the optimized and archetype reactors were 32.8% (0.89 g L(-1)) and 19.4% (0.80 g L(-1)) higher than that in the control reactor (0.67 g L(-1)). Therefore, the novel mixer can significantly increase the fluid velocity along the light attenuation and light/dark cycles, thus further increased the maximum biomass concentration. The PBRs with novel mixers are greatly applicable for high-efficiency cultivation of microalgae.
DEFF Research Database (Denmark)
Kong, Weiqiang; Wang, Zhifeng; Fan, Jianhua;
2012-01-01
obtain fluid thermal capacitance in data processing. Then theoretical analysis and experimental verification are carried out to investigate influencing factors of obtaining accurate and stable second order term. A flat plate and ETC solar collector are compared using both the new dynamic method......A new dynamic test method is introduced. This so called improved transfer function method features on two new collector parameters. One is time term which can indicate solar collector's inner heat transfer ability and the other is a second order term of collector mean fluid temperature which can...... and a standard method. The results show that the improved function method can accurately and robustly estimate these two kinds of solar collectors....
Jakkareddy, Pradeep S.; Balaji, C.
2016-09-01
This paper employs the Bayesian based Metropolis Hasting - Markov Chain Monte Carlo algorithm to solve inverse heat transfer problem of determining the spatially varying heat transfer coefficient from a flat plate with flush mounted discrete heat sources with measured temperatures at the bottom of the plate. The Nusselt number is assumed to be of the form Nu = aReb(x/l)c . To input reasonable values of ’a’ and ‘b’ into the inverse problem, first limited two dimensional conjugate convection simulations were done with Comsol. Based on the guidance from this different values of ‘a’ and ‘b’ are input to a computationally less complex problem of conjugate conduction in the flat plate (15mm thickness) and temperature distributions at the bottom of the plate which is a more convenient location for measuring the temperatures without disturbing the flow were obtained. Since the goal of this work is to demonstrate the eficiacy of the Bayesian approach to accurately retrieve ‘a’ and ‘b’, numerically generated temperatures with known values of ‘a’ and ‘b’ are treated as ‘surrogate’ experimental data. The inverse problem is then solved by repeatedly using the forward solutions together with the MH-MCMC aprroach. To speed up the estimation, the forward model is replaced by an artificial neural network. The mean, maximum-a-posteriori and standard deviation of the estimated parameters ‘a’ and ‘b’ are reported. The robustness of the proposed method is examined, by synthetically adding noise to the temperatures.
Large-eddy simulation of separation and reattachment of a flat plate turbulent boundary layer
Cheng, W.
2015-11-11
© 2015 Cambridge University Press. We present large-eddy simulations (LES) of separation and reattachment of a flat-plate turbulent boundary-layer flow. Instead of resolving the near wall region, we develop a two-dimensional virtual wall model which can calculate the time- and space-dependent skin-friction vector field at the wall, at the resolved scale. By combining the virtual-wall model with the stretched-vortex subgrid-scale (SGS) model, we construct a self-consistent framework for the LES of separating and reattaching turbulent wall-bounded flows at large Reynolds numbers. The present LES methodology is applied to two different experimental flows designed to produce separation/reattachment of a flat-plate turbulent boundary layer at medium Reynolds number Reθ based on the momentum boundary-layer thickness θ. Comparison with data from the first case at demonstrates the present capability for accurate calculation of the variation, with the streamwise co-ordinate up to separation, of the skin friction coefficient, Reθ, the boundary-layer shape factor and a non-dimensional pressure-gradient parameter. Additionally the main large-scale features of the separation bubble, including the mean streamwise velocity profiles, show good agreement with experiment. At the larger Reθ = 11000 of the second case, the LES provides good postdiction of the measured skin-friction variation along the whole streamwise extent of the experiment, consisting of a very strong adverse pressure gradient leading to separation within the separation bubble itself, and in the recovering or reattachment region of strongly-favourable pressure gradient. Overall, the present two-dimensional wall model used in LES appears to be capable of capturing the quantitative features of a separation-reattachment turbulent boundary-layer flow at low to moderately large Reynolds numbers.
Stream-wise distribution of skin-friction drag reduction on a flat plate with bubble injection
Qin, Shijie; Chu, Ning; Yao, Yan; Liu, Jingting; Huang, Bin; Wu, Dazhuan
2017-03-01
To investigate the stream-wise distribution of skin-friction drag reduction on a flat plate with bubble injection, both experiments and simulations of bubble drag reduction (BDR) have been conducted in this paper. Drag reductions at various flow speeds and air injection rates have been tested in cavitation tunnel experiments. Visualization of bubble flow pattern is implemented synchronously. The computational fluid dynamics (CFD) method, in the framework of Eulerian-Eulerian two fluid modeling, coupled with population balance model (PBM) is used to simulate the bubbly flow along the flat plate. A wide range of bubble sizes considering bubble breakup and coalescence is modeled based on experimental bubble distribution images. Drag and lift forces are fully modeled based on applicable closure models. Both predicted drag reductions and bubble distributions are in reasonable concordance with experimental results. Stream-wise distribution of BDR is revealed based on CFD-PBM numerical results. In particular, four distinct regions with different BDR characteristics are first identified and discussed in this study. Thresholds between regions are extracted and discussed. And it is highly necessary to fully understand the stream-wise distribution of BDR in order to establish a universal scaling law. Moreover, mechanism of stream-wise distribution of BDR is analysed based on the near-wall flow parameters. The local drag reduction is a direct result of near-wall max void fraction. And the near-wall velocity gradient modified by the presence of bubbles is considered as another important factor for bubble drag reduction.
Munuswamy, Dinesh Babu; Madhavan, Venkata Ramanan; Mohan, Mukunthan
2015-12-01
To improve the efficiency of solar flat-plate collectors further, a study had been carried out wherein the conventional working fluid was replaced by nanofluids. A 25-L/day solar flat-plate water heater with collector area of 0.5 {m}^2 has been designed and fabricated. The thermosyphon system of the solar water heater was monitored at 15 locations using T-type thermocouples. Alumina and CuO nanoparticles were synthesized and characterized using Brunauer-Emmett-Teller and X-ray diffraction techniques and dispersed using ultrasonic mechanism. To stabilize the system at an optimum level, the collector is operated with volume fractions of 0.2% and 0.4% of synthesized Al2O3 and CuO nanoparticles mixed with distilled water and used in the solar flat-plate collector. The temperature profile was compared with different volume fractions of the nanoparticles in the flowing medium. Enhanced heat transfer was observed in the solar flat-plate collector using nanoparticles, and hence, it is inferred that addition of nanoparticles improves the efficiency of the solar water heaters. This paper details the temperature profile observed in the collectors, variation of insolation over the day, and change in efficiency both on the primary side (collector) and on the secondary side (storage tank) of the solar water heater.
Johnson, S.
1976-01-01
This preliminary data report gives basic test results of a flat-plate solar collector whose performance was determined in the NASA-Lewis solar simulator. The collector was tested over ranges of inlet temperatures, fluxes and coolant flow rates. Collector efficienty is correlated in terms of inlet temperature and flux level.
Adimurthy, M.; Katti, Vadiraj V.
2016-06-01
Local distribution of wall static pressure and heat transfer on a smooth flat plate impinged by a normal slot air jet is experimental investigated. Present study focuses on the influence of jet-to-plate spacing (Z/D h ) (0.5-10) and Reynolds number (2500-20,000) on the fluid flow and heat transfer distribution. A single slot jet with an aspect ratio (l/b) of about 22 is chosen for the current study. Infrared Thermal Imaging technique is used to capture the temperature data on the target surface. Local heat transfer coefficients are estimated from the thermal images using `SMART VIEW' software. Wall static pressure measurement is carried out for the specified range of Re and Z/D h . Wall static pressure coefficients are seen to be independent of Re in the range between 5000 and 15,000 for a given Z/D h . Nu values are higher at the stagnation point for all Z/D h and Re investigated. For lower Z/D h and higher Re, secondary peaks are observed in the heat transfer distributions. This may be attributed to fluid translating from laminar to turbulent flow on the target plate. Heat transfer characteristics are explained based on the simplified flow assumptions and the pressure data obtained using Differential pressure transducer and static pressure probe. Semi-empirical correlation for the Nusselt number in the stagnation region is proposed.
M, Adimurthy; Katti, Vadiraj V.
2017-02-01
Local distribution of wall static pressure and heat transfer on a smooth flat plate impinged by a normal slot air jet is experimental investigated. Present study focuses on the influence of jet-to-plate spacing ( Z/D h ) (0.5-10) and Reynolds number (2500-20,000) on the fluid flow and heat transfer distribution. A single slot jet with an aspect ratio ( l/b) of about 22 is chosen for the current study. Infrared Thermal Imaging technique is used to capture the temperature data on the target surface. Local heat transfer coefficients are estimated from the thermal images using `SMART VIEW' software. Wall static pressure measurement is carried out for the specified range of Re and Z/D h . Wall static pressure coefficients are seen to be independent of Re in the range between 5000 and 15,000 for a given Z/D h . Nu values are higher at the stagnation point for all Z/D h and Re investigated. For lower Z/D h and higher Re, secondary peaks are observed in the heat transfer distributions. This may be attributed to fluid translating from laminar to turbulent flow on the target plate. Heat transfer characteristics are explained based on the simplified flow assumptions and the pressure data obtained using Differential pressure transducer and static pressure probe. Semi-empirical correlation for the Nusselt number in the stagnation region is proposed.
Cai, Chunpei; He, Xin
2016-05-01
This paper presents two sets of analytical exact solutions for collisionless gas flows from a planar exit, impinging at an inclined flat plate. These analytical results are obtained by using gaskinetic theories. The first set of solutions are for a diffuse reflective plate surface, and the other set of solutions are for a specular reflective plate surface. A virtual nozzle exit is adopted to aid analyzing the specular reflective plate scenario. New formulas for plate surface properties, including velocity slips, pressure, shear stress, and heat flux distributions, are provided. For both problems, the flowfield exact solutions are investigated as well. Numerical simulations with the direct simulation Monte Carlo method are performed to validate these new analytical results, and good agreement is obtained for flows with high Knudsen numbers. The results consider effects from many factors, such as the plate inclination angle, geometry ratios, and exit gas and plate properties (such as exit gas bulk density, gas speed ratio, and exit gas and plate temperatures). Compared with past work, these new solutions are more comprehensive and practical. The results also illustrate that if the plate is quite close to the nozzle exit, it is improper to adopt the traditional treatments of a point source and a simple cosine function.
Directory of Open Access Journals (Sweden)
Suozhu Wang
2015-02-01
Full Text Available Reducing friction resistance and aerodynamic heating has important engineering significance to improve the performances of super/hypersonic aircraft, so the purpose of transition control and turbulent drag reduction becomes one of the cutting edges in turbulence research. In order to investigate the influences of wall cooling and suction on the transition process and fully developed turbulence, the large eddy simulation of spatially evolving supersonic boundary layer transition over a flat-plate with freestream Mach number 4.5 at different wall temperature and suction intensity is performed in the present work. It is found that the wall cooling and suction are capable of changing the mean velocity profile within the boundary layer and improving the stability of the flow field, thus delaying the onset of the spatial transition process. The transition control will become more effective as the wall temperature decreases, while there is an optimal wall suction intensity under the given conditions. Moreover, the development of large-scale coherent structures can be suppressed effectively via wall cooling, but wall suction has no influence.
Energy Technology Data Exchange (ETDEWEB)
Rhodes, R.O.; Chapman, N.J.; Chao, K.C.; Sorenson, K.F.
1980-01-01
This study investigated materials and processes for fundamental improvements in flat-plate solar collector cost and performance. The goal was to develop a process for direct conversion of inexpensive raw materials into a completed solar collector unit, without labor intensive assembly operations. It was thought that materials carefully matched to the process and end-use environment would substantially reduce collector costs, as compared to conventional industry practice. The project studied the feasibility of a cost-effective, glazed solar collector, with low labor input, utilizing a coaxial extrusion of compatible polymeric materials. This study evaluated all considered materials for the desired application. In addition, there was a trial extrusion of the leading candidate glazing and absorber materials, which resulted in successfully performing a coaxial extrusion of one cell. At the time the study was conducted, there were no materials available that met the necessary requirements for the specified utilization. It was recommended that, if potentially compatible materials become available, further investigation into the suitability of those materials be researched. Then, if a suitable material was found, proceeding into Phase II would be recommended.
Huang, Jianke; Li, Yuanguang; Wan, Minxi; Yan, Yi; Feng, Fei; Qu, Xiaoxing; Wang, Jun; Shen, Guomin; Li, Wei; Fan, Jianhua; Wang, Weiliang
2014-05-01
Novel flat-plate photobioreactors (PBRs) with special mixers (type-a, type-b, and type-c) were designed based on increased mixing degree along the light gradient. The hydrodynamic and light regime characteristic of the novel PBRs were investigated through computational fluid dynamics. Compared with the control reactor without mixer, the novel reactors can effectively increase liquid velocity along the light gradient, the frequency of light/dark (L/D) cycles, and the algal growth rates of Chlorella pyrenoidosa. The maximum biomass concentrations in type-a, type-b, and type-c reactors were 42.9% (1.3 g L(-1)), 31.9% (1.2 g L(-1)), and 20.9% (1.1 g L(-1)) higher than that in the control reactor (0.91 g L(-1)), respectively, at an aeration rate of 1.0 vvm. Correlation analysis of algal growth rate with the characteristics of mixing and light regime shows the key factors affecting algal photoautotrophic growth are liquid velocity along the light gradient and L/D cycles rather than the macro-mixing degree.
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ML CHOUGUI
2014-12-01
Full Text Available Adrar is a city in the Sahara desert, in southern Algeria known for its hot and dry climate, where a huge amount of energy is used for air conditioning. The aim of this research is to simulate a single effect lithium bromide–water absorption chiller coupled to a double-glazed flat plate collector to supply the cooling loads for a house of 200m2 in Adrar. The thermal energy is stored in an insulated thermal storage tank. The system was designed to cover a cooling load of 10.39KW for design day of July. Thermodynamic model was established to simulate the absorption cycle. The results have shown that the collector mass flow rate has a negligible effect on the minimum required collector area, but it has a significant effect on the optimum capacity of the storage tank. The minimum required collector area was about 65.3 m2, which could supply the cooling loads for the sunshine hours of the design day for July. The operation of the system has also been considered after sunset by saving solar energy.
Energy Technology Data Exchange (ETDEWEB)
Lee, Handol; Yook, Sejin; Han, Seogyoung [Hanyang University, Seoul (Korea, Republic of)
2012-10-15
The deposition velocity is used to assess the degree of particulate contamination of wafers or photomasks. A numerical model was developed to predict the deposition velocity under the combined influences of thermophoresis and electrophoresis. The deposition velocity onto a face-up flat plate in parallel airflow was simulated by varying the temperature difference between the plate's surface and ambient air or by changing the strength of the electric field established above the plate. Both attraction and repulsion by thermophoresis or electrophoresis were considered. When the plate's surface was colder than ambient air, the surface of the face-up plate could be at risk of contamination by charged particles even with a repulsive applied electric force. When the temperature of the plate's surface was higher than the ambient temperature, the degree of particulate contamination on the surface of the face-up plate could be remarkably reduced in the presence of an electric field. The effect of repulsive thermophoresis, however, is expected to be reduced for very fine particles of high electric mobility or for micrometer-sized particles with large gravitational settling speed when the charged particles are influenced by an attractive electric force.
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S.K. Parida
2015-12-01
Full Text Available This work considers the two-dimensional steady MHD boundary layer flow of heat and mass transfer over a flat plate with partial slip at the surface subjected to the convective heat flux. The particular attraction lies in searching the effects of variable viscosity and variable thermal diffusivity on the behavior of the flow. In addition, non-linear thermal radiation effects and thermophoresis are taken into account. The governing nonlinear partial differential equations for the flow, heat and mass transfer are transformed into a set of coupled nonlinear ordinary differential equations by using similarity variable, which are solved numerically by applying Runge–Kutta fourth–fifth order integration scheme in association with quasilinear shooting technique. The novel results for the dimensionless velocity, temperature, concentration and ambient Prandtl number within the boundary layer are displayed graphically for various parameters that characterize the flow. The local skin friction, Nusselt number and Sherwood number are shown graphically. The numerical results obtained for the particular case are fairly in good agreement with the result of Rahman [6].
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A. Malvandi
2015-01-01
Full Text Available The falling and settling of solid particles in gases and liquids is a natural phenomenon happens in many industrial processes. This phenomenon has altered pure forced convection to a combination of heat conduction and heat convection in a flow over a plate. In this paper, the coupling of conduction (inside the plate and forced convection of a non-homogeneous nanofluid flow (over a flat plate is investigated, which is classified in conjugate heat transfer problems. Two-component four-equation non-homogeneous equilibrium model for convective transport in nanofluids (mixture of water with particles<100nm has been applied that incorporates the effects of the nanoparticles migration due to the thermophoresis and Brownian motion forces. Employing similarity variables, we have transformed the basic non-dimensional partial differential equations to ordinary differential ones and then solved numerically. Moreover, variation of the heat transfer and concentration rates with thermal resistance of the plate is studied in detail. Setting the lowest dependency of heat transfer rate to the thermal resistance of the plate as a goal, we have shown that for two nanofluids with similar heat transfer characteristics, the one with higher Brownian motion (lower nanoparticle diameter is desired.
On the correlation between force production and the flow field around a flapping flat-plate wing
Öz, Sören; Krishna, Swathi; Mulleners, Karen
2015-11-01
One of the several sophisticated flight skills that insects exhibit is hovering, which is accomplished largely by modulating the wing kinematics and thereby the flow field around the wings. Along with the prolonged attachment of the leading edge vortex, the wing reversal mechanisms form the basis by which insects regulate the magnitude and direction of forces produced. The duration and starting point of these directional flips are studied in the current experimental investigation. Particle image velocimetry is conducted to evaluate the flow features inherent to changes in wing reversal during the stroke of a flat plate, which is modelled based on hoverfly characteristics. The duration of rotation is one-third of the total time period. A +10% phase shift is used for delayed rotation, a -10% phase shift for advanced rotation. Phase-averaged data is analysed to understand the influence of a delayed or advanced rotation on the formation and evolution of large and small scale structures, their interactions with the wing, and disintegration. Additionally, force data is used to quantify the effects of phase-shift in terms of lift and drag variation and is correlated with the vortex dynamics.
Directory of Open Access Journals (Sweden)
Andrew Y. A. Oyieke
2016-01-01
Full Text Available A flat-plate Vacuum Insulated Photovoltaic and Thermal (VIPV/T system has been thermodynamically simulated and experimentally evaluated to assess the thermal and electrical performance as well as energy conversion efficiencies under a subtropical climate. A simulation model made of specified components is developed in Transient Systems (TRNSYS environment into which numerical energy balance equations are implemented. The influence of vacuum insulation on the system’s electrical and thermal yields has been evaluated using temperatures, current, voltage, and power flows over daily and annual cycles under local meteorological conditions. The results from an experiment conducted under steady-state conditions in Durban, South Africa, are compared with the simulation based on the actual daily weather data. The VIPV/T has shown improved overall and thermal efficiencies of 9.5% and 16.8%, respectively, while electrical efficiency marginally reduced by 0.02% compared to the conventional PV/T. The simulated annual overall efficiency of 29% (i.e., 18% thermal and 11% electrical has been realised, in addition to the solar fraction, overall exergy, and primary energy saving efficiencies of 39%, 29%, and 27%, respectively.
Frankl, F.; Voishel, V.
1943-01-01
In the present report an investigation is made on a flat plate in a two-dimensional compressible flow of the effect of compressibility and heating on the turbulent frictional drag coefficient in the boundary layer of an airfoil or wing radiator. The analysis is based on the Prandtl-Karman theory of the turbulent boundary later and the Stodola-Crocco, theorem on the linear relation between the total energy of the flow and its velocity. Formulas are obtained for the velocity distribution and the frictional drag law in a turbulent boundary later with the compressibility effect and heat transfer taken into account. It is found that with increase of compressibility and temperature at full retardation of the flow (the temperature when the velocity of the flow at a given point is reduced to zero in case of an adiabatic process in the gas) at a constant R (sub x), the frictional drag coefficient C (sub f) decreased, both of these factors acting in the same sense.
The effect of aspect ratio on vortex rings within the wake of impulsively-started flat plates
Fernando, John; Rival, David
2014-11-01
Vortex pinch-off has been the focus of many studies since it was first observed for vortices produced via piston-cylinder arrangements. Minimal work has been performed on other vortex generation methods. The current study investigates vortex rings behind impulsively-started circular, square, and elliptical flat plates. Preliminary force and PIV measurements show temporal/spatial similarities between vortex growth in the wake of the circular and square plates. Forces and vortex evolution are also shown to be strongly coupled; the presence of stable wake vortex rings results in a reduction of plate drag. For all three plates, pinch-off is initiated by the formation of a positive pressure gradient on the leeward side of the plate, which terminates mass transport to the vortex. It is hypothesized that an increase in aspect ratio (AR) from unity results in isolated vortex lines with non-uniform vorticity along the leading edges. Strong spanwise velocity gradients and stretching near the plate tips facilities vortex detachment. Results from experiments on rectangular plates with varying ARs are discussed and the effect of stretching and tilting in the tip region is investigated. The United States Air Force Office of Scientific Research.
Feedback control of unstable steady states of flow past a flat plate using reduced-order estimators
Ahuja, Sunil
2009-01-01
We present an estimator-based control design procedure for flow control, using reduced-order models of the governing equations, linearized about a possibly unstable steady state. The reduced models are obtained using an approximate balanced truncation method that retains the most controllable and observable modes of the system. The original method is valid only for stable linear systems, and we present an extension to unstable linear systems. The dynamics on the unstable subspace are represented by projecting the original equations onto the global unstable eigenmodes, assumed to be small in number. A snapshot-based algorithm is developed, using approximate balanced truncation, for obtaining a reduced-order model of the dynamics on the stable subspace. The proposed algorithm is used to study feedback control of 2-D flow over a flat plate at a low Reynolds number and at large angles of attack, where the natural flow is vortex shedding, though there also exists an unstable steady state. For control design, we de...
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Flamm, H.; Lochau, R.; Maeiss, M.; Schiele, J.
1984-07-01
In a newly constructed south-west-facade 200 m/sup 2/ of flat plate collectors were integrated as construction elements to heat domestic water. The building needs 5-10 m/sup 3/ of hot water per day, i.e. 250-500 kWh/d. The solar circuit runs with a water-glycol-mixture with a specific volume flow rate of 20-40 l/m/sup 2/h. The storage capacity is 8 m/sup 3/, i.e. 40 l/m/sup 2/ collector area. The heating system is bivalent. The total cost was DM 220.000, excepting the cost of facade construction. The observation period was 2 years. The heat flow balance was measured daily using a microprocessor. As far as the construction was concerned, there were no defects during the observation period. The rooms behind solar collectors showed no additional thermal load. The most favourable season for running solar systems is from April to September. In this period the average efficiencies were 15 to 20%, the net energy yield was 76 kWh/m/sup 2/.
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Sona Kazemi
2016-01-01
Full Text Available The separator plays a key role on the performance of passive air-breathing flat-plate MFCs (FPMFC as it isolates the anaerobic anode from the air-breathing cathode. The goal of the present work was to study the separator characteristics and its effect on the performance of passive air-breathing FPMFCs. This was performed partially through characterization of structure, properties, and performance correlations of eight separators presented in Part 1. Current work (Part 2 presents a numerical model developed based on the mixed potential theory to investigate the sensitivity of the electrode potentials and the power output to the separator characteristics. According to this numerical model, the decreased peak power results from an increase in the mass transfer coefficients of oxygen and ethanol, but mainly increasing mixed potentials at the anode by oxygen crossover. The model also indicates that the peak power is affected by the proton transport number of the separator, which affects the cathode pH. Anode pH, on the other hand, remains constant due to application of phosphate buffer solution as the electrolyte. Also according to this model, the peak power is not sensitive to the resistivity of the separator because of the overshadowing effect of the oxygen crossover.
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Puvaneswari Puvaneswari
2016-01-01
Full Text Available The effect of conjugation on the enhancement of heat transfer in a liquid metal flow past a thermally conducting and sinusoidally oscillating infinite flat plate, when a constant temperature gradient is superimposed on the fluid, is investigated. The plate is made up of the materials compatible with the liquid metals used and is considered to be of finite thickness. Analytical solutions for the velocity and the temperature of the fluid and the solid are obtained. The effects of thermal conductivity and the thickness of the plate on the total time averaged heat flux transported and the thermal boundary layer thickness are investigated in detail. It is found that the effects of wall thickness and wall thermal conductivity on the heat flux transported depend on their effects on the transverse temperature gradient at any frequency. The optimum value of wall thickness at which the net heat flux transported attains the maximum value, for each fluid and for each wall material under consideration, is reported. A maximum increase of 46.14 % in the heat flux transported can be achieved by optimizing the wall thickness. A maximum convective heat flux of 1.87 × 108W/m2 is achieved using Na with AISI 316 wall. All the results obtained have been compared with the experimental and analytical results reported in the literature and are found to be in good agreement. It is believed that the new insights gained will be of significant use while designing liquid metal heat transfer systems.
Simon, F. F.
1975-01-01
A performance evaluation was made of two, black nickel coated, flat plate solar collectors. Collector performance was determined under a simulated sun for a wide range of inlet temperatures, including the temperature required for solar powered absorption air conditioning. For a basis of comparison a performance test was made on a traditional, two glass, nonselective, black paint coated, flat plate collector. Performance curves and performance parameters are presented to point out the importance of the design variables which determine an efficient collector. A black nickel coated collector was found to be a good performer at the conditions expected for solar powered absorption air conditioning. This collector attained a thermal efficiency of 50 percent at an inlet temperature of 366 K (200 F) and an incident flux of 946 watts/sq m (300 Btu/hr-sq ft).
Jiang, Caigui
2014-07-01
Motivated by requirements of freeform architecture, and inspired by the geometry of hexagonal combs in beehives, this paper addresses torsion-free structures aligned with hexagonal meshes. Since repetitive geometry is a very important contribution to the reduction of production costs, we study in detail “honeycomb structures”, which are defined as torsion-free structures where the walls of cells meet at 120 degrees. Interestingly, the Gauss-Bonnet theorem is useful in deriving information on the global distribution of node axes in such honeycombs. This paper discusses the computation and modeling of honeycomb structures as well as applications, e.g. for shading systems, or for quad meshing. We consider this paper as a contribution to the wider topic of freeform patterns, polyhedral or otherwise. Such patterns require new approaches on the technical level, e.g. in the treatment of smoothness, but they also extend our view of what constitutes aesthetic freeform geometry.
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Kovacs, Peter; Pettersson, Ulrik
2002-10-01
Two solar combisystems were mounted side by side in an outdoor test facility and continuously operated during one year. The whole year, all relevant temperatures, flow rates and environment variables were thoroughly measured. The systems were identical apart from the collectors which were a 9 m{sup 2} vacuum tube and a 12.2 m{sup 2} selective flat plate collector. A simulated space heating and tap water load of approx. 25 MWh/a was applied to each system and auxiliary heat was charged to the stores from emulated pellet boilers. Additionally, the two collectors and the store was tested separately and the systems simulated according to the CTSS principle described in ENV 12977. The aim of the project was to determine solar fractions in a solar combisystem from real measurements and to compare the two different collector types from different points of view. On the basis of the validated simulation model, the results from the long term measurements could be generalized and eight different loads were simulated. The results showed that the vacuum tubes performed 45-60% better than the flat plate per m{sup 2} depending on the load applied. The solar fractions (assuming no losses from the boiler) varied from 11% for the measured systems to approx. 30 % in a house with 25 % of the original space heating load. During the heating season, the vacuum tubes occasionally performed much worse than the flat plate due to the fact that snow and frost melted away much quicker from the flat plate. For the use of vacuum tubes in snowy regions, vertical mounting should therefore be strongly recommended.
Kaplanis, S.; Kaplani, E.
2012-01-01
This paper outlines and formulates a compact and effective simulation model, which predicts the performance of single and double glaze flat-plate collector. The model uses an elaborated iterative simulation algorithm and provides the collector top losses, the glass covers temperatures, the collector absorber temperature, the collector fluid outlet temperature, the system efficiency, and the thermal gain for any operational and environmental conditions. It is a numerical approach based on simu...
Institute of Scientific and Technical Information of China (English)
无
1996-01-01
The coupled heat and mass transfer problem of gas flow over a UHF flat plate with its wall coated with sublimable substance was been solved by local non-smimilarity method.Considerations have been given also to the effect of non-saturation of the sublimable substance in the oncoming flow and the normal injection velocity at the surface.Analytical results are given for local Noselt and Sherwood Numbers at the various locations.
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Palaniappan Chandramohan
2017-01-01
Full Text Available The aim of this work is to investigate experimentally the variation in temperature, heat transfer coefficient and Nusselt number of a hot plate subjected to multi-jet air impingement cooling to use the multi-objective optimization technique to arrive at optimum conditions. A flat plate of 15 cm x 10 cm is heated through a heating foil with a constant heat flux of 7667 W/m2. Air jets with and without swirling action are considered, fixing the distance of target surface from nozzle exit at 2D, 4D and 6D. Reynolds numbers 18000, 20000and 22000 and pipe diameters 8mm, 10mm and 12 mm have been considered for investigation. Experiments are designed and analyzed using Taguchi’s technique, coupled with principal component analysis for multi-variate optimization by calculating multi-response performance index (MRPI. Based on the observations made, it is concluded that lower H/D ratio and higher Reynolds number result in higher heat transfer coefficient, in accordance with the first principles. Heat transfer coefficient obtained for jets with swirl is compared with that of jet without swirling for the same Reynolds number and H/D ratio. Furthermore, it is concluded that introducing swirl results in increase of heat transfer coefficients for all the test conditions for 10mm and 12mm diameter jets. However for 8mm jet, introduction of swirl reduced the heat transfer rate for all the test conditions. From Analysis of Variance (ANOVA, it is found that significant contributions on outputs are due to the effect of H/D ratio and Reynolds number. Confirmation experiments with optimum condition result in improved heat transfer coefficient and Nusselt number. Numerical simulation has also been performed with the optimum condition. It is observed that the simulation results are in consistence with the experimental results.
Directory of Open Access Journals (Sweden)
Orlando Montoya-Marquez
2017-01-01
Full Text Available In this experimental work, the effects of the inclination angle β and the (Ti − Ta/G on the efficiency and the UL-value were investigated on a medium-temperature flat plate solar collector. The experiments were based on steady-state energy balance, by heat flow calorimetry at indoor conditions and considering the standard American National Standard Institute/American Society of Heating Refrigerating and Air Conditioning Engineers (ANSI/ASHRAE 93-2010. The solar radiation was emulated by the Joule effect using a proportional integral derivative (PID control considering two conditions of the absorber temperature, Case 1: (To − Ti > 0, and Case 2: (To − Ti = 0. The inclination angles were 0°–90° and the (Ti − Ta/G were 0.044–0.083 m2·°C/W and 0.124–0.235 for Case 1 and Case 2, respectively. The variations of β and (Ti − Ta/G cause efficiency changes up to 0.37–0.45 (21.6% and 0.31–0.45 (45.0%, respectively, for Case 1. Also, the UL(β reached changes up to 10.1–12.0 W/m2·°C (19.2% and 8.4–12.0 W/m2·°C (41.7%, respectively, for Case 1. The most significant changes of UL(β/UL(90° vs. β were 8.0% at the horizontal position for Case 1, while for Case 2, the maximum change was 1.8% only. Therefore, the changes of the inclination angle cause significant variations of the convective flow patterns within the collector, which leads to considerable variation of the collector efficiency and its UL value.
Meda, Adimurthy; Katti, Vadiraj V.
2017-08-01
The present work experimentally investigates the local distribution of wall static pressure and the heat transfer coefficient on a rough flat plate impinged by a slot air jet. The experimental parameters include, nozzle-to-plate spacing (Z /D h = 0.5-10.0), axial distance from stagnation point ( x/D h ), size of detached rib ( b = 4-12 mm) and Reynolds number ( Re = 2500-20,000). The wall static pressure on the surface is recorded using a Pitot tube and a differential pressure transmitter. Infrared thermal imaging technique is used to capture the temperature distribution on the target surface. It is observed that, the maximum wall static pressure occurs at the stagnation point ( x/D h = 0) for all nozzle-to-plate spacing ( Z/D h ) and rib dimensions studied. Coefficient of wall static pressure ( C p ) decreases monotonically with x/D h . Sub atmospheric pressure is evident in the detached rib configurations for jet to plate spacing up to 6.0 for all ribs studied. Sub atmospheric region is stronger at Z/D h = 0.5 due to the fluid accelerating under the rib. As nozzle to plate spacing ( Z/D h ) increases, the sub-atmospheric region becomes weak and vanishes gradually. Reasonable enhancement in both C p as well as Nu is observed for the detached rib configuration. Enhancement is found to decrease with the increase in the rib width. The results of the study can be used in optimizing the cooling system design.
The flow of a power-law fluid in the near-wake of a flat plate
Zhou, Min; Ladeinde, Foluso; Bluestein, Danny
2006-08-01
The analysis of the near-wake flow downstream of a flat plate is reported in this paper for the case of a non-Newtonian (power-law) constitutive model. To our knowledge, the present paper is the first to address this problem, as previous work on near-wakes has been limited to the use of a Newtonian model. The motivation for this work comes from the biomedical engineering problem of blood flow around the bileaflet of a mechanical heart valve. In the present paper, the series method has been used to calculate the flow near the centerline of the wake, while an asymptotic method has been used for larger distances from the centerline. The effects of power-law inlet conditions on the wake flow are reported for various values of the power-law index n, within the range 0.7≤n ≤1.3. The present analysis has been successfully validated by comparing the results for n =1 to the near-wake results by Goldstein [Proc. Cambridge Philos. Soc. 26, 1 (1930)]. We generalized the equations for arbitrary values of n, without any special considerations for n =1. Therefore, the accurate results observed for n =1 validate our procedure as a whole. The first major finding is that a fluid with smaller n develops faster downstream, such that decreasing n leads to monotonically increasing velocities compared to fluids with large n values. Another finding is that the non-Newtonian effects become more significant as the downstream distance increases. Finally, these effects tend to be more pronounced in the vicinity of the wake centerline compared to larger y locations.
Diseño de un colector solar de placa plana; Design of a Solar Flat Plate Collector
Directory of Open Access Journals (Sweden)
Jeovany Rafael Rodríguez Mejía
2015-12-01
Full Text Available En el presente artículo se integra el uso de un software de diseño mecánico y un algoritmo de simulación de la operación de un colector solar de placa plana, con el objetivo de simplificar el proceso de diseño y manufactura de este último. Se exponen los resultados de la simulación de la operación del colector solar considerando diferentes combinaciones en los parámetros de los materiales utilizados, tales como sus propiedades y características físico químicas, además de la variación de las dimensiones del sistema adiseñar. Finalmente en el artículo se evalúa la operación de un colector solar para las condiciones climatológicas típicas de la irradiancia, velocidad de viento y temperatura ambiente a partir de una serie de curvas sinusoidales, típicas de Cuba, validándose la viabilidad del algoritmo como apoyo en la etapa de diseño y selección de materiales.In this article the use of mechanical design software and an algorithm for simulating the operation of a flat plate solar collector, with the objective of simplifying the process of design and manufacture of the latter isintegrated. The simulation results of the operation of the solar collector considering different combinations in the parameters of the materials used, such as its physicochemical properties and features in addition to thevariation of the dimensions of the system design are set. The article finally evaluates the operation of a solar collector for typical climatic conditions of irradiance, wind speed and ambient temperature from a series ofsinusoidal, typical Cuba curves is evaluated, validating the feasibility of the algorithm as support in step design and material selection.
Fedoul, Faical; Parras, Luis; Del Pino, Carlos; Fernandez-Feria, Ramon
2012-11-01
Wind tunnel experiments are conducted for the flow around both a single flat plate and a cascade of three parallel flat plates at different angles of incidence to compare their lift and drag coefficients in a range of Reynolds number about 105, and for two values of the aspect ratio of the flat plates. The selected cascade configuration is of interest for a particular type of tidal energy converter. The lift and drag characteristics of the central plate in the cascade are compared to those of the isolated plate, finding that there exist an angle of incidence, which depends on the Reynolds number and the aspect ratio, above which the effective lift of the plate in the cascade becomes larger than that of an isolated plate. These experimental results, which are also analyzed in the light of theoretical predictions, are used as a guide for the design of the optimum configuration of the cascade which extracts the maximum power from a tidal current for a given value of the Reynolds number. Supported by the Ministerio de Ciencia e Innovacion (Spain) Grant no. ENE2010-16851.
Rai, Man Mohan
2017-01-01
The near wake of a flat plate is investigated via direct numerical simulations (DNS). Many earlier experimental investigations have used thin plates with sharp trailing edges and turbulent boundary layers to create the wake. This results in large theta divided by D (sub TE) values (theta is the boundary layer momentum thickness towards the end of the plate and D (sub TE) is the trailing edge thickness). In the present study the emphasis is on relatively thick plates with circular trailing edges (CTE) resulting in theta divided by D values less than one (D is the plate thickness and the diameter of the CTE), and vigorous vortex shedding. The Reynolds numbers based on the plate length and D are 1.255 x 10 (sup 6) and 10,000, respectively. Two cases are computed; one with turbulent boundary layers on both the upper and lower surfaces of the plate (statistically the same, symmetric wake, Case TT) and, a second with turbulent and laminar boundary layers on the upper and lower surfaces, respectively (asymmetric case, Case TL). The data and understanding obtained is of considerable engineering interest, particularly in turbomachinery where the pressure side of an airfoil can remain laminar or transitional because of a favorable pressure gradient and the suction side is turbulent. Shed-vortex structure and phase-averaged velocity statistics obtained in the two cases are compared here. The upper negative shed vortices in Case TL (turbulent separating boundary layer) are weaker than the lower positive ones (laminar separating boundary layer) at inception (a factor 1.27 weaker in terms of peak phase-averaged spanwise vorticity at first appearance of a peak). The upper vortices weaken rapidly as they travel downstream. A second feature of interest in Case TL is a considerable increase in the peak phase-averaged, streamwise normal intensity (random component) with increasing streamwise distance (x divided by D) that occurs nears the positive vortex cores. This behavior is
Institute of Scientific and Technical Information of China (English)
司马文霞; 马高权; 杨庆
2008-01-01
The influence of sand dust on discharge of external insulation has caused widespread concern. At present, the research results show wind-sand electricity has a remarkable effect on the discharge characteristics of insulator and has little influence on the discharge characteristics of air gap. The flashover of insulator strings occurs along the insulator surface and air gaps, and the sand dust deposited on the insulator surface may affect the flashover characteristics of insulator strings. This paper studies the flashover characteristics of flat plate model under DC voltage in wind-sand condition. The experimental results show that under positive polarity voltage, the flashover voltage of the flat plate model has a maximum value, while under negative polarity voltage, the flashover voltage of the flat plate model has a minimum value with a certain degree of sand dust deposition. The wind or sand in sand-dust weather has an important effect on the flashover characteristics of the flat plate model. In certain variation range of electric charge, electric charge of sand dust has little effect on the flashover voltage of flat plate model under DC voltage. The deposition of sand has significant influence on the flashover process of flat plate model, which is related to the deposition density and moisture content of sand particle.
Titanium honeycomb panel testing
Richards, W. L.; Thompson, Randolph C.
The paper describes the procedures of thermal mechanical tests carried out at the NASA Dryden Flight Research Facility on two tianium honeycomb wing panels bonded using liquid interface diffusion (LID) technique, and presents the results of these tests. The 58.4 cm square panels consisted of two 0.152-cm-thick Ti 6-2-4-2 face sheets LID-bonded to a 1.9-cm-thick honeycomb core, with bearing plates fastened to the perimeter of the upper and the lower panel surfaces. The panels were instrumented with sensors for measuring surface temperature, strain, and deflections to 315 C and 482 C. Thermal stress levels representative of those encountered during aerodynamic heating were produced by heating the upper panel surface and restraining all four edges. After more than 100 thermal cycles from room temperature to 315 C and 50 cycles from room temperature to 482 C, no significant structural degradation was detected in the panels.
板式脉动热管强化传热方法研究%Research on Enhancing Heat Transfer of Flat Plate Loop Pulsating Heat Pipe
Institute of Scientific and Technical Information of China (English)
陈陶菲; 徐德好; 刘向东
2011-01-01
To research the method of enhancing heat transfer of flat plate loop pulsating heat pipe,the article compares the heat transfer character of the original heat pipe and the improved one by numerical simulation.Based on the VOF（volume of fluid） method,a three-dimensional unsteady mathematical model was developed to describe the vapor-liquid two-phase flow and phase change heat transfer in the flat plate loop pulsating heat pipe.The two-phase flow pattern transition and the temperature distribution in the flat plate loop pulsating heat pipe under different heat load conditions was numerically investigated using the developed model.The result shows that the heat transfer character of the improved heat pipe can be enhanced under high heat load condition.%为了研究板式脉动热管的传热性能强化的方法,对原型和改进型两种不同板式脉动热管传热特性进行数值分析比较。基于VOF方法建立板式脉动热管汽液两相流动及相变传热三维非稳态数学模型,仿真得到不同加热功率条件下热管内流型演化和温度分布。仿真结果表明,改进型脉动热管在高功率阶段,整体等效热阻小于原型。
NUMERICAL STUDIES OF AERODYNAMIC PERFORMANCE OF NORMAL FLAT PLATES WITH GAP%垂直开缝平板气动性能的数值研究
Institute of Scientific and Technical Information of China (English)
何伟; 田德; 王永; 汪宁渤
2013-01-01
为研究开缝对太阳能光电板承受风载的影响,采用雷诺应力模型分析二维不同间隙开缝平板的垂直绕流特性.基于Fluent模拟了高雷诺数下二维方柱绕流,所得阻力系数平均值及斯特劳哈尔数与文献提供的模拟及实验结果一致,验证了模型模拟高雷诺数下钝体绕流的有效性.通过高雷诺数下平板垂直绕流的阻力系数平均值与斯特劳哈尔数的对比,得出不同间隙尺寸对平板阻力系数的影响,计算结果为太阳能光电板的工程设计提供理论支撑.%The 2D flow characteristics of flat plates with different sizes gaps normal to the incoming flow were presented with Reynolds stress equation for studying the influence of wind loads on the solar PV panel with gap. The model was effective to simulate bluff bodies with high Reynolds numbers by consistency of time averaged mean drag coefficients and Strouhal numbers between this paper and other researchers' simulated and experimental results of 2D square cylinder with high Reynolds number. The time averaged mean drag coefficients and Strouhal numbers of normal flat plate flow with different sizes gaps were compared. The influences of gap sizes on the drag coefficients of flat plates were obtained. The simulated results can support the design of solar PV panel theoretically.
Christensen, Elmer
1985-01-01
The objectives were to develop the flat-plate photovoltaic (PV) array technologies required for large-scale terrestrial use late in the 1980s and in the 1990s; advance crystalline silicon PV technologies; develop the technologies required to convert thin-film PV research results into viable module and array technology; and to stimulate transfer of knowledge of advanced PV materials, solar cells, modules, and arrays to the PV community. Progress reached on attaining these goals, along with future recommendations are discussed.
MIRI, Mohadaseh
2015-01-01
Use solar energy to provide hot water consumption, space heating and cooling in recent decades is considered. In this article a model varies with time, a solar adsorption cooling system consists of a single effect lithium bromide absorption system, a flat plate collector and a storage tank or linear or parabolic simulated separately. The system for cooling an office building for hours of operation from 7 am to 18 pm is considered.About 7 kW peak cooling load occurs in July. Results obtained s...
Shu, Jian-Jun
2015-01-01
The paper presents a theoretical study using the Karman-Pohlhausen method for describing the transient heat exchange between the boundary-layer free convection and a vertical flat plate embedded in a porous medium. The unsteady behavior is developed after the generation of an impulsive heat flux step at the right-hand side of the plate. Two cases are considered according to whether the plate has a finite thickness or no thickness. The time and space evolution of the interface temperature is evidenced.
Lee, Dorothy B; Faget, Maxime A
1956-01-01
A modified method of Van Driest's flat-plate theory for turbulent boundary layer has been found to simplify the calculation of local skin-friction coefficients which, in turn, have made it possible to obtain through Reynolds analogy theoretical turbulent heat-transfer coefficients in the form of Stanton number. A general formula is given and charts are presented from which the modified method can be solved for Mach numbers 1.0 to 12.0, temperature ratios 0.2 to 6.0, and Reynolds numbers 0.2 times 10 to the 6th power to 200 times 10 to the 6th power.
The cosmological principle and honeycombs
Energy Technology Data Exchange (ETDEWEB)
Criado, C [Departamento de Fisica Aplicada I, Universidad de Malaga, 29071 Malaga (Spain); Alamo, N [Departamento de Algebra, Geometria y Topologia, Universidad de Malaga, 29071 Malaga (Spain)
2004-05-07
We present the possibility that the gravitational growth of primordial density fluctuations leads to what can be considered a weak version of the cosmological principle. The large-scale mass distribution associated with this principle must have the geometrical structure known as a regular honeycomb. We give the most important parameters that characterize the honeycombs associated with the closed, open, and flat Friedmann-LemaItre-Robertson-Walker models. These parameters can be used to determine by means of observations which is the appropriate honeycomb. For each of these honeycombs, and for a nearly flat universe, we have calculated the probability that a randomly placed observer could detect the honeycomb as a function of the density parameters {omega}{sub 0} and {omega}{sub {lambda}}{sub 0}.
Directory of Open Access Journals (Sweden)
Sandeep N
2015-03-01
Full Text Available In this study we analyzed the influence of radiation and aligned magneticfield on the flow of ferrofluids over a flat plate in presence of non-uniform heat source/sink and slip velocity. We considered Fe3O4 magnetic nano particles embedded within the two types of base fluids namely water and kerosene. The governing partial differential equations are transformed into nonlinear ordinary differential equations by using similarity transformation and solved numerically using bvp5c Matlab package. The effects of dimensionless quantities on the flow and temperature profiles along with the friction factor and Nusselt number is discussed and presented through graphs and tables. It is found that present results have an excellent agreement with the existed studies under some special assumptions. Results indicate that a raise in the aligned angle enhances the skin friction coefficient and heat transfer rate.
Coumar, Sandra; Lago, Viviana
2017-06-01
This paper presents an experimental investigation, carried out at the Icare Laboratory by the FAST team, focusing on plasma flow control in supersonic and rarefied regime. The study analyzes how the Mach number as well as the ambient pressure modify the repercussions of the plasma actuator on the shock wave. It follows previous experiments performed in the MARHy (ex-SR3) wind tunnel with a Mach 2 flow interacting with a sharp flat plate, where modifications induced by a plasma actuator were observed. The flat plate was equipped with a plasma actuator composed of two aluminum electrodes. The upstream one was biased with a negative DC potential and thus, created a glow discharge type plasma. Experimental measurements showed that the boundary layer thickness and the shock wave angle increased when the discharge was ignited. The current work was performed with two nozzles generating Mach 4 flows but at two different static pressures: 8 and 71 Pa. These nozzles were chosen to study independently the impact of the Mach number and the impact of the pressure on the flow behavior. In the range of the discharge current considered in this experimental work, it was observed that the shock wave angle increased with the discharge current of +15% for the Mach 2 flow but the increase rate doubled to +28% for the Mach 4 flow at the same static pressure, showing that the discharge effect is even more significant when boosting the flow speed. When studying the effect of the discharge on the Mach 4 flow at higher static pressure, it was observed that the topology of the plasma changed drastically and the increase in the shock wave angle with the discharge current of +21 %.
1976-01-01
Basic test results are given of a flat-plate solar collector whose performance was determined in the NASA-Lewis solar simulator. The collector was tested over ranges of inlet temperatures, fluxes, and coolant flow rates. Collector efficiency is correlated in terms of inlet temperature and flux level.
1976-01-01
This preliminary data report gives basic test results of a flat-plate solar collector whose performance was determined in the NASA-Lewis solar simulator. The collector was tested over ranges of inlet temperatures, fluxes and coolant flow rates. Collector efficiency is correlated in terms of inlet temperature and flux level.
Spot Welding of Honeycomb Structures
Cohal, V.
2017-08-01
Honeycomb structures are used to prepare meals water jet cutting machines for textile. These honeycomb structures are made of stainless steel sheet thickness of 0.1-0.2 mm. Corrugated sheet metal strips are between two gears with special tooth profile. Hexagonal cells for obtaining these strips are welded points between them. Spot welding device is three electrodes in the upper part, which carries three welding points across the width of the strip of corrugated sheet metal. Spot welding device filled with press and advance mechanisms. The paper presents the values of the regime for spot welding.
Unconventional superconductivity in honeycomb lattice
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P Sahebsara
2013-03-01
Full Text Available The possibility of symmetrical s-wave superconductivity in the honeycomb lattice is studied within a strongly correlated regime, using the Hubbard model. The superconducting order parameter is defined by introducing the Green function, which is obtained by calculating the density of the electrons . In this study showed that the superconducting order parameter appears in doping interval between 0 and 0.5, and x=0.25 is the optimum doping for the s-wave superconductivity in honeycomb lattice.
Bickler, Donald B.; Callaghan, W. T.
In 1986 during the flat-plate solar array project, silicon solar cells 4.0 sq cm in area were fabricated at the Jet Propulsion Laboratory (JPL) with a conversion efficiency of 20.1 percent (AM1.5-global). Sixteen cells were processed with efficiencies measuring 19.5 percent (AM1.5 global) or better. These cells were produced using refined versions of conventional processing methods, aside from certain advanced techniques that bring about a significant reduction in a major mechanism (surface recombination) that limits cell efficiency. Wacker Siltronic p-type float-zone 0.18-ohm-cm wafers were used. Conversion efficiencies in this range have previously been reported by other researchers, but generally on much smaller (0.5 vs. 4.0 cm) devices which have undergone sophisticated and costly processing steps. An economic analysis is presented of the potential payoffs for this approach, using the Solar Array Manufacturing Industry Costing Standards (SAMICS) methodology. The process sequence used and the assumptions made for capturing the economies of scale are presented.
Sayadi, Taraneh; Hamman, Curtis; Moin, Parviz
2011-11-01
Transition to turbulence via spatially evolving secondary instabilities in compressible, zero-pressure-gradient flat plate boundary layers is numerically simulated for both the Klebanoff K-type and Herbert H-type disturbances. The objective of this work is to evaluate the universality of the breakdown process between different routes through transition in wall-bounded shear flows. Each localized linear disturbance is amplified through weak non-linear instability that grows into lambda-vortices and then hairpin-shaped eddies with harmonic wavelength, which become less organized in the late-transitional regime once a fully populated spanwise turbulent energy spectrum is established. For the H-type transition, the computational domain extends from Rex =105 , where laminar blowing and suction excites the most unstable fundamental and a pair of oblique waves, to fully turbulent stage at Rex = 10 . 6 ×105 . The computational domain for the K-type transition extends to Rex = 9 . 6 ×105 . The computational algorithm employs fourth-order central differences with non-reflective numerical sponges along the external boundaries. For each case, the Mach number is 0.2. Supported by the PSAAP program of DoE, ANL and LLNL.
Peng, Di; Chen, Yujia; Wang, Shaofei; Liu, Yingzheng; Wang, Weizhe
2016-11-01
Previous studies have shown that it is possible to reconstruct the full flow field based on time-resolved measurements at discrete locations using linear stochastic estimation (LSE). The objective of this study is to develop and apply this technique to wall pressure fluctuation measurements in low speed flows. Time-resolved wall pressure fluctuations on a flat plate in the wake of a step cylinder at low speed (V PSP). The microphone arrays are arranged properly to capture the dominant features in the flow field at 10 kHz. The PSP is excited using a continuous UV-LED, and the luminescent signal is recorded by a high-speed camera at 2 kHz. The microphone data at discrete locations are used to reconstruct the full-field wall pressure fluctuations based on LSE. The PSP results serve as basis for improvement of the LSE scheme and also for validation of the reconstructed pressure field. Other data processing techniques including proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) are also used for analyzing the unsteady flow features. This LSE technique has great potential in real-time flow diagnostics and control.
Directory of Open Access Journals (Sweden)
E.Hemalatha
2015-09-01
Full Text Available This paper analyzes the radiation and chemical reaction effects on MHD steady two-dimensional laminar viscous incompressible radiating boundary layer flow over a flat plate in the presence of internal heat generation and convective boundary condition. It is assumed that lower surface of the plate is in contact with a hot fluid while a stream of cold fluid flows steadily over the upper surface with a heat source that decays exponentially. The Rosseland approximation is used to describe radiative heat transfer as we consider optically thick fluids. The governing boundary layer equations are transformed into a system of ordinary differential equations using similarity transformations, which are then solved numerically by employing fourth order Runge-Kutta method along with shooting technique. The effects of various material parameters on the velocity, temperature and concentration as well as the skin friction coefficient, the Nusselt number, the Sherwood number and the plate surface temperature are illustrated and interpreted in physical terms. A comparison of present results with previously published results shows an excellent agreement.
Directory of Open Access Journals (Sweden)
Sona Kazemi
2016-01-01
Full Text Available Passive air-breathing microbial fuel cells (MFCs are a promising technology for energy recovery from wastewater and their performance is highly dependent on characteristics of the separator that isolates the anaerobic anode from the air-breathing cathode. The goal of the present work is to systematically study the separator characteristics and its effect on the performance of passive air-breathing flat-plate MFCs (FPMFCs. This was performed through characterization of structure, properties, and performance correlations of eight separators in Part 1 of this work. Eight commercial separators were characterized, in non-inoculated and inoculated setups, and were examined in passive air-breathing FPMFCs with different electrode spacing. The results showed a decrease in the peak power density as the oxygen and ethanol mass transfer coefficients in the separators increased, due to the increase of mixed potentials especially at smaller electrode spacing. Increasing the electrode spacing was therefore desirable for the application of diaphragms. The highest peak power density was measured using Nafion®117 with minimal electrode spacing, whereas using Nafion®117 or Celgard® with larger electrode spacing resulted in similar peak powers. Part 2 of this work focuses on numerical modelling of the FPMFCs based on mixed potential theory, implementing the experimental data from Part 1.
Directory of Open Access Journals (Sweden)
Xavier Ortiz
2015-03-01
Full Text Available To improve knowledge of the wind loads on photovoltaic structures mounted on flat roofs at the high angles required in high latitudes, and to study starting flow on low aspect ratio wind turbine blades, a series of wind tunnel tests were undertaken. Thin flat plates of aspect ratios between 0.4 and 9.0 were mounted on a sensitive three-component instantaneous force and moment sensor. The Reynolds numbers varied from 6 × 104 to 2 × 105. Measurements were made for angles of attack between 0° and 90° both in the free stream and in wall proximity with increased turbulence and mean shear. The ratio of drag to lift closely follows the inverse tangent of the angle of incidence for virtually all measurements. This implies that the forces of interest are due largely to the instantaneous pressure distribution around the plate and are not significantly influenced by shear stresses. The instantaneous forces appear most complex for the smaller aspect ratios but the intensity of the normal force fluctuations is between 10% and 20% in the free-steam but can exceed 30% near the wall. As the wind tunnel floor is approached, the lift and drag reduce with increasing aspect ratio, and there is a reduction in the high frequency components of the forces. It is shown that the centre of pressure is closer to the centre of the plates than the quarter-chord position for nearly all cases.
Martinuzzi, Robert
2016-11-01
Quasi-periodic vortex shedding in the turbulent wake of a thin-flat plate placed normal to a uniform stream at Reynolds number of 6700 is investigated based on Particle Image Velocimetry experiments. The wake structure and vortex formation are characterized using a generalized phase average (GPA), a refinement of the triple decomposition of Reynolds and Hussain (1970) incorporating elements of mean-field theory (Stuart, 1958). The resulting analysis highlights the importance of cycle-to-cycle variations in characterizing vortex formation, wake topology and the residual turbulent Reynolds Stresses. For example, it is shown that during high-amplitude cycles vorticity is strongly concentrated within the well-organized shed vortices, whereas during low-amplitude cycles the shed vortices are highly distorted resulting in significant modulation of the shedding frequency. It is found that high-amplitude cycles contribute more to the coherent Reynolds stress field while the low-amplitude cycles contribute to the residual stress field. It is further shown that traditional phase-averaging techniques lead to an over-estimation of the residual stress field. Natural Sciences and Engineering Research Council of Canada.
Gao, Baoyan; Chen, Ailing; Zhang, Wenyuan; Li, Aifen; Zhang, Chengwu
2017-10-01
The marine diatom Phaeodactylum tricornutum is a polymorphological, ecologically significant, and well-studied model of unicellular microalga. This diatom can accumulate diverse important metabolites. Herein, we cultured P. tricornutum in an internally installed tie-piece flat-plate photobioreactor under 14.5 m mol L-1 (high nitrogen, HN) and 2.9 m mol L-1 (low nitrogen, LN) of KNO3 and assessed its time-resolved changes in biochemical compositions. The results showed that HN was inductive to accumulate high biomass (4.1 g L-1). However, the LN condition could accelerate lipid accumulation in P. tricornutum. The maximum total lipid (TL) content under LN was up to 42.5% of biomass on day 12. Finally, neutral lipids (NLs) were 63.8% and 75.7% of TLs under HN and LN, respectively. The content of EPA ranged from 2.3% to 1.5% of dry weight during the growth period under the two culture conditions. Peak volumetric lipid productivity of 128.4 mg L-1d-1 was achieved in the HN group (on day 9). The highest volumetric productivity values of EPA, chrysolaminarin, and fucoxanthin were obtained in the exponential phase (on day 6) under HN, which were 9.6, 93.6, and 4.7 mg L-1d-1, respectively. In conclusion, extractable amounts of lipids, EPA, fucoxanthin, and chrysolaminarin could be obtained from P. tricornutum by regulating the culture conditions.
EXPERIMENTAL RESEARCH ON A HIGH EFFICIENT FLAT PLATE SOLAR COLLECTOR%一种高效平板太阳能集热器试验研究
Institute of Scientific and Technical Information of China (English)
李戬洪; 江晴
2001-01-01
性能良好的太阳能集热器是太阳能空调的关键设备之一。广东省江门市太阳能空调系统采用了一种高效的平板集热器，其主要技术特征是增加了一块聚碳酸脂(PC)透明隔热板。本研究通过对比试验，确定了一种高效平板太阳能集热器的技术方案，并测定了瞬时效率曲线，其热损系数仅为2.90W/(m2*℃)。%Good performance of the solar collectors is one of the important elements for solar air-conditioning system.A novel type of high efficient flat plate solar collector was applied to the solar air-condition system in Jiangmen，Guangdong Province.Tests show that adding a transparent polycarbonate sheet in gap between glazing and absorber of the collector. The coefficient of the thermal loss is reduced to 2.90W/(m2℃) and the performance of the collector is improved.
A Fully Inkjet Printed 3D Honeycomb Inspired Patch Antenna
Mckerricher, Garret
2015-07-16
The ability to inkjet print three-dimensional objects with integrated conductive metal provides many opportunities for fabrication of radio frequency electronics and electronics in general. Both a plastic material and silver conductor are deposited by inkjet printing in this work. This is the first demonstration of a fully 3D Multijet printing process with integrated polymer and metal. A 2.4 GHz patch antenna is successfully fabricated with good performance proving the viability of the process. The inkjet printed plastic surface is very smooth, with less than 100 nm root mean square roughness. The printed silver nanoparticles are laser sintered to achieve adequate conductivity of 1e6 S/m while keeping the process below 80oC and avoiding damage to the polymer. The antenna is designed with a honeycomb substrate which minimizes material consumption. This reduces the weight, dielectric constant and dielectric loss which are all around beneficial. The antenna is entirely inkjet printed including the ground plane conductor and achieves an impressive 81% efficiency. The honeycomb substrate weighs twenty times less than a solid substrate. For comparison the honeycomb antenna provides an efficiency nearly 15% greater than a similarly fabricated antenna with a solid substrate.
Capturing Gases in Carbon Honeycomb
Krainyukova, Nina V.
2017-04-01
In our recent paper (Krainyukova and Zubarev in Phys Rev Lett 116:055501, 2016. doi: 10.1103/PhysRevLett.116.055501) we reported the observation of an exceptionally stable honeycomb carbon allotrope obtained by deposition of vacuum-sublimated graphite. A family of structures can be built from absolutely dominant {sp}2-bonded carbon atoms, and may be considered as three-dimensional graphene. Such structures demonstrate high absorption capacity for gases and liquids. In this work we show that the formation of honeycomb structures is highly sensitive to the carbon evaporation temperature and deposition rates. Both parameters are controlled by the electric current flowing through thin carbon rods. Two distinctly different regimes were found. At lower electric currents almost pure honeycomb structures form owing to sublimation. At higher currents the surface-to-bulk rod melting is observed. In the latter case densification of the carbon structures and a large contribution of glassy graphite emerge. The experimental diffraction patterns from honeycomb structures filled with absorbed gases and analyzed by the advanced method are consistent with the proposed models for composites which are different for Ar, Kr and Xe atoms in carbon matrices.
Capturing Gases in Carbon Honeycomb
Krainyukova, Nina V.
2016-12-01
In our recent paper (Krainyukova and Zubarev in Phys Rev Lett 116:055501, 2016. doi: 10.1103/PhysRevLett.116.055501) we reported the observation of an exceptionally stable honeycomb carbon allotrope obtained by deposition of vacuum-sublimated graphite. A family of structures can be built from absolutely dominant {sp}2 -bonded carbon atoms, and may be considered as three-dimensional graphene. Such structures demonstrate high absorption capacity for gases and liquids. In this work we show that the formation of honeycomb structures is highly sensitive to the carbon evaporation temperature and deposition rates. Both parameters are controlled by the electric current flowing through thin carbon rods. Two distinctly different regimes were found. At lower electric currents almost pure honeycomb structures form owing to sublimation. At higher currents the surface-to-bulk rod melting is observed. In the latter case densification of the carbon structures and a large contribution of glassy graphite emerge. The experimental diffraction patterns from honeycomb structures filled with absorbed gases and analyzed by the advanced method are consistent with the proposed models for composites which are different for Ar, Kr and Xe atoms in carbon matrices.
Study of Cylindrical Honeycomb Solar Collector
Directory of Open Access Journals (Sweden)
Atish Mozumder
2014-01-01
Full Text Available We present the results of our investigation on cylindrical honeycomb solar collector. The honeycomb has been fabricated with transparent cellulose triacetate polymer sheets. Insulation characteristics of the honeycomb were studied by varying the separation between the honeycomb and the absorber plate. The optimal value of the separation was found to be 3.3 mm for which the heat transfer coefficient is 3.06 W m−2 K−1. This supports result of previous similar experiments. Further we test the honeycomb through a field experiment conducted in Delhi (28.6°N, 77°E and found that when the incident angle of the solar radiation is within 20° then the performance of the system with the honeycomb is better than the one without the honeycomb.
Nonlinear acoustics and honeycomb materials
Thompson, D. O.
2012-05-01
The scope of research activity that Bruce Thompson embraced was very large. In this talk three different research topics that the author shared with Bruce are reviewed. They represent Bruce's introduction to NDE and include nonlinear acoustics, nondestructive measurements of adhesive bond strengths in honeycomb panels, and studies of flexural wave dispersion in honeycomb materials. In the first of these, four harmonics of a 30 Mhz finite amplitude wave were measured for both fused silica and aluminum single crystals with varying lengths and amounts of cold work using a capacity microphone with heterodyne receiver with a flat frequency response from 30 to 250 Mhz. The results for fused silica with no dislocation structure could be described by a model due to Fubini, originally developed for gases, that depends upon only the second and third order elastic constants and not the fourth and higher order constants. The same was not true for the aluminum with dislocation structures. These results raised some questions about models for harmonic generation in materials with dislocations. In the second topic, experiments were made to determine the adhesive bond strengths of honeycomb panels using the vibrational response of the panels (Chladni figures). The results showed that both the damping characteristics of panel vibrations as a whole and velocity of propagation of elastic waves that travel along the surface and sample the bondline can be correlated with destructively determined bond strengths. Finally, the phase velocity of flexural waves traveling along a 1-inch honeycomb sandwich panel was determined from 170 Hz to 50 Khz, ranging from 2.2×104 cm/sec at the low end to 1.18×105 cm/sec at 40 Khz. The dispersion arises from the finite thickness of the panel and agreed with the results of continuum models for the honeycomb. Above 40 Khz, this was not the case. The paper concludes with a tribute to Bruce for his many wonderful contributions and lessons beyond his
Energy Technology Data Exchange (ETDEWEB)
Hori, M.; Yata, J. [Kyoto Inst. of Technology, Kyoto (Japan); Minamiyama, T. [Fukuyama University, Hiroshima (Japan)
1996-04-25
The effects of free stream turbulence on turbulent boundary layer were calculated using a {kappa}-{epsilon} two-equation model. The calculations were performed with respect to velocity profiles on a flat plate wall shear stress turbulence energy integral length scales of turbulence and decay of free stream turbulence and the results were compared with experimental results. The energy of free stream turbulence and the dissipation values at the leading edge of flat plate were used, as the initial conditions for calculation. These initial values of dissipation were determined from the integral length scales of free stream turbulence at the leading edge. The calculated wall shear stress increased with the free stream turbulence and integral length scales of turbulence. The velocity profiles and turbulence energy agreed well with the experimental results and the effects of free stream turbulence on the wall shear stress agreed fairly well with those observed in experiments. 15 refs., 10 figs.
Energy Technology Data Exchange (ETDEWEB)
Tavakolpour, Ali Reza; Zomorodian, Ali [Department of Mechanics of Farm Machinery Engineering, Shiraz University, Shiraz (Iran); Akbar Golneshan, Ali [Department of Mechanical Engineering, Shiraz University, Shiraz (Iran)
2008-01-15
In this research, a gamma-type, low-temperature differential (LTD) solar Stirling engine with two cylinders was modeled, constructed and primarily tested. A flat-plate solar collector was employed as an in-built heat source, thus the system design was based on a temperature difference of 80{sup o}C. The principles of thermodynamics as well as Schmidt theory were adapted to use for modeling the engine. To simulate the system some computer programs were written to analyze the models and the optimized parameters of the engine design were determined. The optimized compression ratio was computed to be 12.5 for solar application according to the mean collector temperature of 100{sup o}C and sink temperature of 20{sup o}C. The corresponding theoretical efficiency of the engine for the mentioned designed parameters was calculated to be 0.012 for zero regenerator efficiency. Proposed engine dimensions are as follows: power piston stroke 0.044 m, power piston diameter 0.13 m, displacer stroke 0.055 m and the displacer diameter 0.41 m. Finally, the engine was tested. The results indicated that at mean collector temperature of 110{sup o}C and sink temperature of 25{sup o}C, the engine produced a maximum brake power of 0.27 W at 14 rpm. The mean engine speed was about 30 rpm at solar radiation intensity of 900 W/m{sup 2} and without load. The indicated power was computed to be 1.2 W at 30 rpm. (author)
Directory of Open Access Journals (Sweden)
Olek Małgorzata
2016-01-01
Full Text Available The popularity of solar collectors in Poland is still increasing. The correct location of the collectors and a relatively high density of solar radiation allow delivering heat even in spite of relatively low ambient temperature. Moreover, solar systems used for heating domestic heat water (DHW in summer allow nearly complete elimination of conventional energy sources (e.g. gas, coal. That is why more and more house owners in Poland decide to install solar system installations. In Poland the most common types of solar collectors are flat plate collectors (FPC and evacuated tube collectors with heat pipe (ETCHP; both were selected for the analysis. The heat demand related to the preparation of hot water, connected with the size of solar collectors’ area, has been determined. The analysis includes FPC and ETCHP and heat demand of less than 10 000 kWh/year. Simulations were performed with the Matlab software and using data from a typical meteorological year (TMY. In addition, a 126–year period of measurements of insolation for Krakow has been taken into account. The HDKR model (Hay, Davis, Klucher, Reindl was used for the calculation of solar radiation on the absorber surface. The monthly medium temperature of the absorber depends on the amount of solar system heat and on the heat demand. All the previously mentioned data were used to determine solar efficiency. Due to the fact that solar efficiency and solar system heat are connected, the calculations were made with the use of an iterative method. Additionally, the upper limit for monthly useful solar system heat is resulted from the heat demand and thus the authors prepared a model of statistical solar system heat deviations based on the Monte Carlo method. It has been found that an increase in the useful solar system heat in reference to the heat demand is associated with more than proportional increase in the sizes of the analyzed surfaces of solar collector types.
Batubara, Fatimah; Dina, Sari Farah; Klaudia Kathryn Y., M.; Turmuzi, M.; Siregar, Fitri; Panjaitan, Nora
2017-06-01
Research on the effect of openings solar collector and solar irradiance to thermal efficiency has been done. Solar collector by flat plate-finned type consists of 3 ply insulator namely wood, Styrofoam and Rockwool with thickness respectively are 10 mm, 25 mm and 50 mm. Absorber plate made of aluminum sheet with thickness of 0.30 mm, painted by black-doff. Installation of 19 units fins (length x height x thickness: 1000x20x10 mm) on the collector will increase surface area of absorber so it can receive much more solar energy. The solar collector cover is made of glass (thickness of 5 mm). During the research, the solar irradiance and temperature of collector are measured and recorded every five minutes. Temperature measurement performed on the surface of the absorber plate, inside of collector, surface cover and the outer side insulator (plywood). This data is used to calculate the heat loss due to conduction, convection and radiation on the collector. Openings of collectors vary as follows: 100%, 75%, 15% and 0% (total enclosed). The data collecting was conducted from 09.00 am to 17.00 pm and triplicates. The collector thermal efficiency calculated based on the ratio of the amount of heat received to the solar irradiance absorbed. The results show that each of openings solar collector has different solar irradiance (because it was done on a different day) which is in units of W/m2: 390 (100% open), 376 (75% open), 429 (15% open), and 359 (totally enclosed). The highest thermal efficiency is in openings variation of 15% opened. These results indicate that the efficiency of the collector is influenced by the solar irradiance received by the collector and the temperature on the collector plate. The highest thermal efficiency is in variation of openings 15%. These indicate that the efficiency of the collector was influenced by solar irradiance received by the collector and openings of the collector plate.
Einstein, Thomas H.
1961-01-01
Equations were derived representing heat transfer and pressure drop for a gas flowing in the passages of a heater composed of a series of parallel flat plates. The plates generated heat which was transferred to the flowing gas by convection. The relatively high temperature level of this system necessitated the consideration of heat transfer between the plates by radiation. The equations were solved on an IBM 704 computer, and results were obtained for hydrogen as the working fluid for a series of cases with a gas inlet temperature of 200 R, an exit temperature of 5000 0 R, and exit Mach numbers ranging from 0.2 to O.8. The length of the heater composed of the plates ranged from 2 to 4 feet, and the spacing between the plates was varied from 0.003 to 0.01 foot. Most of the results were for a five- plate heater, but results are also given for nine plates to show the effect of increasing the number of plates. The heat generation was assumed to be identical for each plate but was varied along the length of the plates. The axial variation of power used to obtain the results presented is the so-called "2/3-cosine variation." The boundaries surrounding the set of plates, and parallel to it, were assumed adiabatic, so that all the power generated in the plates went into heating the gas. The results are presented in plots of maximum plate and maximum adiabatic wall temperatures as functions of parameters proportional to f(L/D), for the case of both laminar and turbulent flow. Here f is the Fanning friction factor and (L/D) is the length to equivalent diameter ratio of the passages in the heater. The pressure drop through the heater is presented as a function of these same parameters, the exit Mach number, and the pressure at the exit of the heater.
Enhancing the Heat Transfer of Flat-plate Solar Collector%平板太阳能集热器强化传热应用研究进展∗
Institute of Scientific and Technical Information of China (English)
吉佳文; 王文志; 李金凯; 段广彬; 刘宗明
2016-01-01
As the key part of the flat-plate solar water heater,the heat transfer performance of the collector is determined by the heat collector efficiency.The flat-plate solar collector with typical structure and heat transfer mode are described.Meanwhile the present technologies for enhancing heat transfer of flat-plate solar collector and the fu-ture development trend are reviewed and discussed.%集热器作为平板太阳能热水器的关键部分，其传热性能决定着热水器集热效率的高低。介绍了平板太阳能集热器的典型结构以及传热方式，综述了平板太阳能集热器目前所采用的强化传热方式及今后强化传热技术的发展趋势。
Mechanical properties of additively manufactured octagonal honeycombs.
Hedayati, R; Sadighi, M; Mohammadi-Aghdam, M; Zadpoor, A A
2016-12-01
Honeycomb structures have found numerous applications as structural and biomedical materials due to their favourable properties such as low weight, high stiffness, and porosity. Application of additive manufacturing and 3D printing techniques allows for manufacturing of honeycombs with arbitrary shape and wall thickness, opening the way for optimizing the mechanical and physical properties for specific applications. In this study, the mechanical properties of honeycomb structures with a new geometry, called octagonal honeycomb, were investigated using analytical, numerical, and experimental approaches. An additive manufacturing technique, namely fused deposition modelling, was used to fabricate the honeycomb from polylactic acid (PLA). The honeycombs structures were then mechanically tested under compression and the mechanical properties of the structures were determined. In addition, the Euler-Bernoulli and Timoshenko beam theories were used for deriving analytical relationships for elastic modulus, yield stress, Poisson's ratio, and buckling stress of this new design of honeycomb structures. Finite element models were also created to analyse the mechanical behaviour of the honeycombs computationally. The analytical solutions obtained using Timoshenko beam theory were close to computational results in terms of elastic modulus, Poisson's ratio and yield stress, especially for relative densities smaller than 25%. The analytical solutions based on the Timoshenko analytical solution and the computational results were in good agreement with experimental observations. Finally, the elastic properties of the proposed honeycomb structure were compared to those of other honeycomb structures such as square, triangular, hexagonal, mixed, diamond, and Kagome. The octagonal honeycomb showed yield stress and elastic modulus values very close to those of regular hexagonal honeycombs and lower than the other considered honeycombs.
Characterizing Facesheet/Core Disbonding in Honeycomb Core Sandwich Structure
Rinker, Martin; Ratcliffe, James G.; Adams, Daniel O.; Krueger, Ronald
2013-01-01
Results are presented from an experimental investigation into facesheet core disbonding in carbon fiber reinforced plastic/Nomex honeycomb sandwich structures using a Single Cantilever Beam test. Specimens with three, six and twelve-ply facesheets were tested. Specimens with different honeycomb cores consisting of four different cell sizes were also tested, in addition to specimens with three different widths. Three different data reduction methods were employed for computing apparent fracture toughness values from the test data, namely an area method, a compliance calibration technique and a modified beam theory method. The compliance calibration and modified beam theory approaches yielded comparable apparent fracture toughness values, which were generally lower than those computed using the area method. Disbonding in the three-ply facesheet specimens took place at the facesheet/core interface and yielded the lowest apparent fracture toughness values. Disbonding in the six and twelve-ply facesheet specimens took place within the core, near to the facesheet/core interface. Specimen width was not found to have a significant effect on apparent fracture toughness. The amount of scatter in the apparent fracture toughness data was found to increase with honeycomb core cell size.
基于动网格方法的拍动平板升力分析%Lift performance analysis of flapping flat plate using dynamic mesh method
Institute of Scientific and Technical Information of China (English)
于宪钊; 苏玉民; 曹建; 闫岱峻
2012-01-01
Aim at micro air vehicles,two-dimensional and three-dimensional flapping flat plate lift performance of advanced,synchronized and delayed rotation were numerically investigated by dynamic mesh method.The vortices and lift changes versus kinematic motions were highlighted to analyze the relationship between lift performance and kinematic motions.Numerical results show that the lift coefficients of synchronized and advanced rotation model are larger than that of delayed rotation obviously;the lift coefficients of two-dimensional and three-dimensional flapping plate decrease with increasing of angular amplitude and increase with increasing phase lag,while the influence of plunging amplitude is less relatively.The lift coefficients of three-dimensional plate are larger than two-dimensional plate in advanced rotation model with higher angular amplitude,also in delayed rotation only when lower angular amplitude and shorter plunging amplitude.The lift coefficients of two-dimensional and three-dimensional flapping plate are not changed significantly in synchronized rotation with higher angular amplitude.%针对微型飞行器,采用动网格方法计算了旋转超前、同步、滞后3种拍动模式下的平板升力性能.通过比较分析二维、三维拍动平板的升力性能以及尾涡分布变化,探讨了拍动平板升力性能与其运动规律的关系.计算表明：旋转同步和超前模式下的平板升力系数明显高于旋转滞后模式下的平板升力系数;二维、三维平板升力系数均随角振幅的增大而减小,随相位差的增大而增大,拍动振幅的影响相对较小;角振幅较大时,旋转超前模式中三维平板升力系数均明显高于二维平板升力系数,旋转同步模式中二维、三维平板升力系数变化不明显,旋转滞后模式中仅当小角振幅且小平移振幅时,三维平板升力系数增加较大.
Simon, F. F.
1975-01-01
This paper reports the measured thermal efficiency and evaluation of 23 collectors which differ according to absorber material (copper, aluminum, steel), absorber coating (nonselective black paint, selective copper oxide, selective black nickel, selective black chrome), type of glazing material (glass, Tedlar, Lexan, anti-reflection glass), the use of honeycomb material and the use of vacuum to prevent thermal convection losses. The collectors are given performance rankings based on noon-hour solar conditions and all-day solar conditions. The determination with the simulator of an all-day collector performance is made possible by tests at different incident angles. The solar performance rankings are made based on whether the collector is to be used for pool heating, hot water, absorption air conditioning, heating, or for a solar Rankine machine.
Aluminum Honeycomb Characteristics in Dynamic Crush Environments
Energy Technology Data Exchange (ETDEWEB)
Bateman, Vesta I.; Swanson, Lloyd H.
1999-07-01
Fifteen aluminum honeycomb cubes (3 in.) have been crushed in the Mechanical Shock Laboratory's drop table testing machines. This report summarizes shock experiments with honeycomb densities of 22.1 pcf and 38.0 pcf and with crush weights of 45 lb, 168 lb, and 268 lb. The honeycomb samples were crushed in all three orientations, W, L, and T. Most of the experiments were conducted at an impact velocity of {approx}40 fps, but higher velocities of up to 90 fps were used for selected experiments. Where possible, multiple experiments were conducted for a specific orientation and density of the honeycomb samples. All results are for Hexcel honeycomb except for one experiment with Alcore honeycomb and have been evaluated for validity. This report contains the raw acceleration data measured on the top of the drop table carriage, pictures of the crushed samples, and normalized force-displacement curves for all fifteen experiments. These data are not strictly valid for material characteristics in L and T orientations because the cross-sectional area of the honeycomb changed (split) during the crush. However, these are the best data available at this time. These dynamic crush data do suggest a significant increase in crush strength to 8000 psi ({approximately} 25-30% increase) over quasi-static values of {approximately}6000 psi for the 38.0 pcf Hexcel Honeycomb in the T-orientation. An uncertainty analysis is included and estimates the error in these data.
Mechanical Properties of Additively Manufactured Thick Honeycombs
Directory of Open Access Journals (Sweden)
Reza Hedayati
2016-07-01
Full Text Available Honeycombs resemble the structure of a number of natural and biological materials such as cancellous bone, wood, and cork. Thick honeycomb could be also used for energy absorption applications. Moreover, studying the mechanical behavior of honeycombs under in-plane loading could help understanding the mechanical behavior of more complex 3D tessellated structures such as porous biomaterials. In this paper, we study the mechanical behavior of thick honeycombs made using additive manufacturing techniques that allow for fabrication of honeycombs with arbitrary and precisely controlled thickness. Thick honeycombs with different wall thicknesses were produced from polylactic acid (PLA using fused deposition modelling, i.e., an additive manufacturing technique. The samples were mechanically tested in-plane under compression to determine their mechanical properties. We also obtained exact analytical solutions for the stiffness matrix of thick hexagonal honeycombs using both Euler-Bernoulli and Timoshenko beam theories. The stiffness matrix was then used to derive analytical relationships that describe the elastic modulus, yield stress, and Poisson’s ratio of thick honeycombs. Finite element models were also built for computational analysis of the mechanical behavior of thick honeycombs under compression. The mechanical properties obtained using our analytical relationships were compared with experimental observations and computational results as well as with analytical solutions available in the literature. It was found that the analytical solutions presented here are in good agreement with experimental and computational results even for very thick honeycombs, whereas the analytical solutions available in the literature show a large deviation from experimental observation, computational results, and our analytical solutions.
Aluminum honeycomb impact limiter study
Energy Technology Data Exchange (ETDEWEB)
Yaksh, M.C.; Thompson, T.C. (Nuclear Assurance Corp., Norcross, GA (United States)); Nickell, R.E. (Applied Science and Technology, Inc., Poway, CA (United States))
1991-07-01
Design requirements for a cask transporting radioactive materials must include the condition of the 30-foot free fall of the cask onto an unyielding surface. To reduce the deceleration loads to a tolerable level for all the components of the cask, a component (impact limiter) is designed to absorb the kinetic energy. The material, shape, and method of attachment of the impact limiter to the cask body comprises the design of the impact limiter. The impact limiter material of interest is honeycomb aluminum, and the particular design examined was for the NAC Legal Weight Truck cask (NAC-LWT) for spent fuel from light water reactors. The NAC-LWT has a design weight of 52,000 pounds, and it has a nominal length of 200 inches. The report describes the numerical calculations embodied in the FADE program to determine the accelerations and crush strain resulting from an arbitrary height and angle of orientation. Since the program serves as a design tool, static tests are performed to assess the effect of the shell containing the honeycomb aluminum. The static tests and their results are contained in the study. The static tests are used to demonstrate for licensing purposes the level of accelerations imposed on the cask during a 30-foot drop. 3 refs., 41 figs., 15 tabs.
Institute of Scientific and Technical Information of China (English)
杜胜华; 苏海鹏
2014-01-01
介绍了平板热管的基本结构与原理，在分析乙二醇及其混合工质的热物理学特性的基础上，建立平板热管的物理与数学模型。采用数值计算模拟方法，分析了混合工质平板热管集热器的传热性能，研究了集热器的效率、温升和启动性能随工作时间的变化规律。研究表明，乙二醇水混合工质平板热管集热器适宜于低温寒冷地区，具有较高的集热性能。%The basic structure and principle of flat plate heat pipe were introduced based on thermal physics characteristics analysis of ethylene glycol and mixtures , physical and mathematical models of flat plate heat pipe were established.By the numerical simulation method , the heat transfer performance of the flat heat pipe heat collector with mixture working fluid was analyzed , and the efficiency , temperature collector up and starting performance by time were studied.It showed that flat heat pipe heat collector with ethylene glycol water mixture was suitable for cold area , and the heat collecting performance was high.
Heisenberg Honeycombs Solve Veneziano Puzzle
Kholodenko, A L
2006-01-01
In this paper we reformulate some results obtained by Heisenberg into modern mathematical language of honeycombs. This language was developed in connection with complete solution of the Horn conjecture problem. Such a reformulation is done with the purpose of posing and solving the following problem. Is by analysing the (spectroscopic) experimental data it possible to restore the underlying microscopic physical model generating these data? Development of Heisenberg's ideas happens to be the most useful for this purpose. Solution is facilitated by our earlier developed string-theoretic formalism. In this paper only qualitative arguments are presented (with few exceptions). These arguments provide enough evidence that the underelying microscopic model compatible with Veneziano-type amplitudes is the standard (i.e. non supersymmetric!) QCD. In addition, usefulness of the formalism is illustrated on numerous examples such as physically motivated solution of the saturation conjecture, derivation of the Yang-Baxter...
Directory of Open Access Journals (Sweden)
F Nadi
2017-05-01
back propagation learning rule was used to simulate the output temperature of a solar collector. The number of neurons within the hidden layer varied from 1 to 20. The hyperbolic tan- sigmoid and pure-line were used as the transfer function in the hidden layer and output layer, respectively. Minimization of error was achieved using the Levenberg-Marquardt algorithm. To carry out the aforementioned steps, the dataset (105 observations was split into training (70 observations, and test (35 observations data. Training sets used to develop models included air velocity, solar radiation, time of the day, ambient moisture and temperature values as inputs with an associated temperature of the collector as outputs. The aim of every training algorithm is to reduce this global error by adjusting the weights and biases. Results and Discussion Compare experimental results with ANN The performance of the three-layer ANN for the prediction of output temperature of flat-plate solar collector by the Levenberg–Marquardt training algorithm was illustrated in Fig. 4. ANN predicted output temperatures with R2 and RMSE of 0.92 and 1.23, respectively. Furthermore, the maximum error in prediction of output temperature of solar collector was 3.3 K. These results are in agreement with Tripathy and Kumar, (2009 those who have predicted the output temperatures of food product in the solar drier using ANN with and RMSE of 0.95 and 0.77, respectively. Compare experimental results with CFD simulation Fig. 6 shows that over the starting length of the absorber plate, there is a variation of the velocity profile which is caused by sharp geometry and it leads to some recirculation of the air in this part of absorber plate. After this part of boundary layers, flow is fully developed and velocity profile becomes smoother and constant. Fig. 8 shows that the predicted temperature was within the experimentally measured temperature. The highest differences between simulated and experimental temperatures
Properties of honeycomb polyester knitted fabrics
Feng, A. F.
2016-07-01
The properties of honeycomb polyester weft-knitted fabrics were studied to understand their advantages. Seven honeycomb polyester weft-knitted fabrics and one common polyester weft-knitted fabric were selected for testing. Their bursting strengths, fuzzing and pilling, air permeability, abrasion resistance and moisture absorption and perspiration were studied. The results show that the honeycomb polyester weft-knitted fabrics have excellent moisture absorption and liberation. The smaller their thicknesses and area densities are, the better their moisture absorption and liberation will be. Their anti-fuzzing and anti-pilling is good, whereas their bursting strengths and abrasion resistance are poorer compared with common polyester fabric's. In order to improve the hygroscopic properties of the fabrics, the proportion of the honeycomb microporous structure modified polyester in the fabrics should not be less than 40%.
Hostetter, Megan
This thesis presents a new type of polypropylene (PP) cellular material fabricated through a simple melt-stretching process. Stochastic honeycombs have an open cell, random honeycomb structure, with webs oriented perpendicular to built-in skins. This process has the advantage that, for example, PP pellets can be turned into a sandwich panel in one step. It was demonstrated that despite the randomness in the web structure, the out-of-plane compressive strength of stochastic honeycombs was repeatable, and exceeded that of commercial PP foams and was comparable to commercial PP honeycombs. The key material properties required to produce an this architecture were shown to be a high melt strength and a high viscosity, branched polymer. The viscosity was shown to affect the total length of the webs in cross-section and the relative partitioning of material through the skin, transition region and webs. Web thickness was affected by the areal density of the polymer during fabrication. Mechanical testing methods were adapted from ASTM standards for honeycombs, and the fabrication method was advanced from a manual to a machine controlled process. Stochastic honeycombs were shown to buckle elastically, plastically, and fracture after the peak strength. Elastic and plastic buckling were dominant at lower densities, and plastic buckling and fracture at higher densities. A thin-plate buckling model for the strength of stochastic honeycombs was developed and verified experimentally. The crystallinity of the polymer affected the tensile strength and stiffness, having a linear effect on the buckling strength. The architecture was composed of webs bound on both sides and webs bound on one side and free on the other. A greater fraction of bound webs increased the strength of the structure in the buckling model. A fabrication study showed that melt-stretching the polymer at higher strain rates increased the connectivity and fraction of bound webs. Additionally, higher density led to a
Institute of Scientific and Technical Information of China (English)
邓月超; 全贞花; 赵耀华; 王林成; 叶三宝
2013-01-01
为了检验一种新型平板太阳能热水器的性能,该文对其核心部件—基于微热管阵列的集热器及其组成的热水器进行了热性能试验.集热器热性能测试结果表明,微热管阵列平板太阳能集热器瞬时效率的斜率为4.7,截距为0.80,分别优于国家标准要求值11.0%和22.3%.在满足测试要求的天气情况下,对微热管阵列平板太阳能热水器进行的多次热性能测试结果表明,热水器的日有效得热量均高于国家标准要求值,日平均集热效率均高于60%.同时,该热水器具有承压能力强、无炸裂、轻巧、成本低、无需焊接、抗冻性能好、易于建筑一体化等优势.基于微热管阵列的平板太阳能热水器由于性能优异,并能克服现有太阳能热水器的缺点,具有广阔的应用前景.%A novel flat plate solar water heater based on the micro heat pipe array (MHPA) was invented, and the experiments were carried out on the MHPA heat collector and water heater to test their thermal performance. Owing to its distinctive structure, the MHPA has good heat transfer ability, high reliability, high compressive strength and low cost. The structure and character of the novel collector with MHPA as the high-efficiency heat transfer element are as follows. First, the contact surface between the absorber and the MHPA is so large that the heat resistance is smaller than the traditional one, thus its thermal transfer capability is greatly improved. Second, the condenser section of the MHPA is connected closely to the heat exchanger with dry type. The heat pipes do not contact with water, which precludes scaling and leakage in the collector. Third, the MHPA uses low freezing points of the refrigerants, which makes the collector more suitable for extremely cold areas. Fourth, the MHPA is made of aluminum instead of copper, which could reduce the fabrication cost significantly. Fifth, the unique heat exchanger could exclude water easily
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
利用平板式光生物反应器对一种新分离的微藻 Parietochloris incisa 进行了室外放大培养研究.在最适培养条件下, 实现了对该微藻的超高密度培养,使单位培养体积和单位培养面积的细胞生物量分别达到了 7.35 g/(L·d)和 96.12 g/(m2·d).%One kind of new microalgae Parietochloris incisa is cultured in outdoor in flat plate photobioreactors. Under optimal culture conditions, the highest volumetric cell biomass output rate of 7.35 g/(L·d) and the areal cell biomass output rate of 96.12 g/(m2·d) are obtained in the photobioreactor.
Institute of Scientific and Technical Information of China (English)
倪贝; 丁昀; 杨庆
2011-01-01
As it is difficult to solve the problem of unsteady - state heat transfer in theory, study of flat plate solar collectors in series -connected system with intermittent output is conducted by numerical simulation.Under the unsteady - state heat transfer condition, the impact of the diameter and center distance of solar collectors on the instantaneous collector efficiency and water production rate per square meter are discussed respectively.The results show that flat cartridge collector performed high effeciency.And under the same conditions, the larger the diameter of collector is, the higher efficiency will be.These can be used for optimizing design parameters of flat plate solar collectors.%由于非稳态传热问题通过理论计算得到解析解较困难,本文运用数值模拟方法研究定温放水型直流式系统中平板型太阳能集热器的工作状况,讨论了集热器的管径和管中心距在非稳态传热条件下对集热器的效率和每平方米产水量的影响.可得到结论扁盒式集热器具有较高效率;相同条件下,管径越大集热器效率越高.该结果有利于优化直流式平板集热器的设计参数.
Propagating edge states in strained honeycomb lattices
Salerno, Grazia; Ozawa, Tomoki; Price, Hannah M.; Carusotto, Iacopo
2017-06-01
We investigate the helically propagating edge states associated with pseudo-Landau levels in strained honeycomb lattices. We exploit chiral symmetry to derive a general criterion for the existence of these propagating edge states in the presence of only nearest-neighbor hoppings and we verify our criterion using numerical simulations of both uniaxially and trigonally strained honeycomb lattices. We show that the propagation of the helical edge state can be controlled by engineering the shape of the edges. Sensitivity to chiral-symmetry-breaking next-nearest-neighbor hoppings is assessed. Our result opens up an avenue toward the precise control of edge modes through manipulation of the edge shape.
Inserting Stress Analysis of Combined Hexagonal Aluminum Honeycombs
Directory of Open Access Journals (Sweden)
Xiangcheng Li
2016-01-01
Full Text Available Two kinds of hexagonal aluminum honeycombs are tested to study their out-of-plane crushing behavior. In the tests, honeycomb samples, including single hexagonal aluminum honeycomb (SHAH samples and two stack-up combined hexagonal aluminum honeycombs (CHAH samples, are compressed at a fixed quasistatic loading rate. The results show that the inserting process of CHAH can erase the initial peak stress that occurred in SHAH. Meanwhile, energy-absorbing property of combined honeycomb samples is more beneficial than the one of single honeycomb sample with the same thickness if the two types of honeycomb samples are completely crushed. Then, the applicability of the existing theoretical model for single hexagonal honeycomb is discussed, and an area equivalent method is proposed to calculate the crushing stress for nearly regular hexagonal honeycombs. Furthermore, a semiempirical formula is proposed to calculate the inserting plateau stress of two stack-up CHAH, in which structural parameters and mechanics properties of base material are concerned. The results show that the predicted stresses of three kinds of two stack-up combined honeycombs are in good agreement with the experimental data. Based on this study, stress-displacement curve of aluminum honeycombs can be designed in detail, which is very beneficial to optimize the energy-absorbing structures in engineering fields.
OUT-OF-PLANE COMPRESSIVE PROPERTIES OF HEXAGONAL PAPER HONEYCOMBS
Institute of Scientific and Technical Information of China (English)
WANG Dongmei; WANG Zhiwei
2007-01-01
The compressive behaviour of paper honeycombs is studied by means of an experimental analysis. Experiment results show how geometry aspects of hexagonal paper honeycombs, e.g. the height of paper honeycomb, the thickness and length of honeycomb cell-wall, the drawing ratio of hexagonal honeycomb, affect the compressive properties of the paper honeycombs. It is in good agreement with the theory model. The constraint factor K of the critical buckling stress is mainly determined by the length of honeycomb cell-wall. It can be described as K=1.54 for B type paper honeycombs and K=3.32 for D type paper honeycombs. The plateau stress is the power exponent function of the thickness to length ratio of honeycomb cell-wall, and the experiment results show that the constant is 13.2 and the power exponent is 1.77. The research results can be used to characterize and improve efficiently the compressive properties of paper honeycombs.
Institute of Scientific and Technical Information of China (English)
李世平; 向开根; 李雯; 罗会龙; 王霜
2015-01-01
Heat pipe has many advantages, such as higher heat transfer coefficient, lower transfer temperature-difference and a one-way heat transfer. A new flat plate heat pipe solar air collector was designed and built based on a reasonable construction. The test results indicated that the instantaneous efficiency of collector is 15.3%~74.5% under the climatic conditions of daily solar radiation being about 14.4 to19.8MJ/m2·day. Its daily average thermal efficiency is about 32.6%~53.5%with heat loss coefficient being 3.6~8.4W/(m2·K). The maximum outlet air temperature can reach 79.1℃. Compared with conventional air collectors, the new flat plate heat pipe solar air collector has higher thermal efficiency and outlet air.%热管具有传热系数高、传热温差小及单向传热等诸多优良特性。以热管为集热部件，试制了一种平板式热管太阳能空气集热器。测试结果表明，在日总太阳辐射为14.4MJ/m2～19.8MJ/m2的气候条件下，平板式热管太阳能空气集热器的瞬时集热效率在15.3%～74.5%之间，集热器出口空气温度可达79.1℃，其日平均集热效率约为32.6%～53.5%，其热损失系数约为3.6～8.4W/(m2·K)。与常规的太阳能空气集热器相比，平板式热管太阳能空气集热器具有较高的集热效率和较低的热损失系数，并且供热温度较高。
Kishan, N.; Jagadha, S.
2016-01-01
The paper presents an investigation of the influence of thermophoresis on MHD mixed convective heat and mass transfer of a viscous, incompressible and electrically conducting fluid along a vertical flat plate with radiation effects. The plate is permeable and embedded in a porous medium. To describe the deviation from the Darcy model the Forchheimer flow model is used. The Rosseland approximation is used to describe the radiative heat flux in the energy equation. The governing partial differential equations are transformed into a system of ordinary differential equations using similarity transformation. The nonlinear ordinary differential equations are linearized by using quasilinearization technique and then solved numerically by using implicit finite difference scheme. The numerical results are analyzed for the effects of various physical parameters such as magnetic parameter Ha, mixed convection parameter Ra d /Pe d , Reynolds number Red, radiation parameter R, thermophoretic parameter τ, Prandtl number Pr, and Schmidt number Sc. The heat transfer coefficient is also tabulated for different values of physical parameters.
Institute of Scientific and Technical Information of China (English)
姜孝均; 李良荣
2016-01-01
本文针对平板便携式卫星通信终端的伺服控制系统展开研究，本文提出一种根据终端设备所在位置的经纬度信息和目标卫星的经度信息，通过对终端设备的平板天线俯仰和方位的伺服控制，自动调整天线的方位和俯仰姿态，使天线指向目标卫星，并进一步对极化角进行调整，从而快速建立起稳定的卫星通信链路的算法设计方案。%The purpose of this paper is to study servosystem for Flat Plate Portable Satellite Communication Terminal. In this paper,we propose a longitude information of the latitude and longitude information and the target satellite,which is located at the location of the terminal equipment.Through the servo control of the antenna's elevation and azimuth of the terminal device to set up fast algorithm design stability of the satellite communication link. The azimuth and elevation of the antenna are adjusted automatically to make the antenna point to the target satellite,and the polarization angle is adjusted further.
Study on a Flat Plate Solar Air Collector with Baffles%扰流板型太阳能平板空气集热器集热性能
Institute of Scientific and Technical Information of China (English)
夏佰林; 赵东亮; 代彦军; 李勇
2011-01-01
对一种扰流板型太阳能平板空气集热器的集热性能进行了研究,并对各种影响集热器热性能的因素进行了分析,揭示了总热损失系数、扰流板肋片效率、流道内空气流速和扰流板的间距对效率因子和热迁移因子的影响机理.获得了扰流板型太阳能平板空气集热器的集热效率理论表达式,为此类太阳能空气集热器的设计及应用提供了参考.%A flat plate solar air collector with baffles was studied. Several factors that have influence on the thermal performance of the solar collectors were analyzed. The paper investigated the relations between the efficiency factor, the heat-removal factor of the solar air collector and the total heat loss coefficient, baffles fin efficiency, air velocity inside the flow channel, the space between baffles, and the height of baffles. Also, the time constant of the collectors was studied. The theoretical formula of the collector's thermal efficiency was obtained, which can be used for design and application of such kind of collectors.
Institute of Scientific and Technical Information of China (English)
卢郁; 于洪文; 丁海成; 张艳丽; 刘宗明
2013-01-01
以平板太阳能集热器作为研究对象,通过对平板太阳能集热器热性能进行理论推导,引入效率因子,构建更为准确、便捷的平板集热器的数学模型,进行计算机程序模拟.根据模拟数据得出吸热体板芯几何结构、板芯用材对平板太阳能集热器性能的影响.在不降低集热器效率因子的情况下,使翅片的单位面积质量降低45.8％；在材料消耗相同的情况下,集热器效率因子提高了0.03.%Taking a flat-plate solar collector as research object and introducing an efficiency factor, we establish a mathematical model for the collector after theoretically deriving out the thermal properties of it, and numerically simulate it according to this model. Simulation results show that the mass per unit area of the collector drops 45. 8% with the same efficiency factor and the efficiency factor increasesby 0.03 with the same material consumption.
Energy Technology Data Exchange (ETDEWEB)
Bracamonte-Baran, Johane Hans; Baritto-Loreto, Miguel Leonardo [Universidad Central de Venezuela (Venezuela)]. E-mails: johanehb@gmail.com; johane.bracamonte@ucv.ve; miguel.baritto@ucv.ve
2013-04-15
The dimensionless model developed and validated by Baritto and Bracamonte (2012) for the thermal behavior of flat plate solar collector without glass cover is improved by adding the entropy balance equation in a dimensionless form. The model is solved for a wide range of aspect ratios and mass flow numbers. A parametric study is developed and the distribution of internal irreversibilities along the collector is analyzed. The influence of the design parameters on the entropy generation by fluid friction and heat transfer is analyzed and it is found that for certain combinations of these parameters optimal thermodynamic operation can be achieved. [Spanish] En el presente trabajo, el modelo adimensional desarrollado y validado por Baritto y Bracamonte (2012) para describir el comportamiento termico de colectores solares de placas planas sin cubierta transparente, se complementa con la ecuacion adimensional de balance de entropia para un elemento diferencial de colector solar. El modelo se resuelve para un amplio rango de valores de relaciones de aspecto y numero de flujo de masa. A partir de los resultados del modelo se desarrolla un analisis detallado de la influencia de estos parametros sobre la distribucion de irreversibilidades internas a lo largo del colector. Adicionalmente se estudia la influencia de estos parametros sobre los numeros de generacion de entropia por friccion viscosa, por transferencia de calor y total. Se encuentra que existen combinaciones de los parametros antes mencionados, para los cuales, la operacion del colector es termodinamicamente optima para numeros de flujo de masa elevados.
Featureless quantum insulator on the honeycomb lattice
Kim, Panjin; Lee, Hyunyong; Jiang, Shenghan; Ware, Brayden; Jian, Chao-Ming; Zaletel, Michael; Han, Jung Hoon; Ran, Ying
2016-08-01
We show how to construct fully symmetric states without topological order on a honeycomb lattice for S =1/2 spins using the language of projected entangled pair states. An explicit example is given for the virtual bond dimension D =4 . Four distinct classes differing by lattice quantum numbers are found by applying the systematic classification scheme introduced by two of the authors [S. Jiang and Y. Ran, Phys. Rev. B 92, 104414 (2015), 10.1103/PhysRevB.92.104414]. Lack of topological degeneracy or other conventional forms of symmetry breaking in the proposed wave functions are checked by numerical calculations of the entanglement entropy and various correlation functions. Exponential decay of all correlation functions measured are strongly indicative of the energy gap for the putative parent Hamiltonian of the state. Our work provides the first explicit realization of a featureless quantum state for spin-1/2 particles on a honeycomb lattice.
Traffic gridlock on a honeycomb city
Olmos, L E
2016-01-01
As a clear signature of modern urban design concepts, urban street networks in dense populated zones are evolving nowadays towards grid-like layouts with rectangular shapes, and most studies on traffic flow assume street networks as square lattices. However, ideas from forgotten design schools bring unexplored alternatives that might improve traffic flow in many circumstances. Inspired on an old and almost in oblivion urban plan, we report the behavior of the Biham-Middleton-Levine model (BML) \\-- a paradigm for studying phase transitions of traffic flow \\-- on a hypothetical city with a perfect honeycomb street network. In contrast with the original BML model on a square lattice, the same model on a honeycomb does not show any anisotropy or intermediate states, but a single continuous phase transition between free and totally congested flow, a transition that can be completely characterized by the tools of classical percolation. Although the transition occurs at a lower density than for the conventional BML,...
Porous-core honeycomb bandgap THz fiber
DEFF Research Database (Denmark)
Nielsen, Kristian; Rasmussen, Henrik K.; Jepsen, Peter Uhd
2011-01-01
In this Letter we propose a novel (to our knowledge) porous-core honeycomb bandgap design. The holes of the porous core are the same size as the holes in the surrounding cladding, thereby giving the proposed fiber important manufacturing benefits. The fiber is shown to have a 0:35-THz......-wide fundamental bandgap centered at 1:05 THz. The calculated minimum loss of the fiber is 0:25 dB=cm....
Pretransitional Clusters in Multicolor Liquid Crystalline Honeycombs
Ungar, Goran; Zeng, Xiangbing; Liu, Feng; Kieffer, Robert; Nürnberger, Constance; Tschierske, Carsten; Gehring, Gillian
2012-02-01
X-shaped tetraphilic molecules consisting of a rod-like core with two hydrogen-bonding terminal groups and two mutually incompatible side-chains A and B form a range of honeycomb-like structures in which the rods act as bricks in the walls of polygonal cylinder cells containing the fluid side-chains. Some of these systems exhibit a 2nd-order transition from the high-temperature mixed (``1-color'') phase to a low-temperature phase in which the side-chains are separated in A and B cells (``2-color''). This is the situation with triangular, rectangular and square honeycombs. Strong pre-transitional 2-color domains formation is observed above the transition temperature. Particularly interesting is the case of the hexagonal honeycomb, where no fully phase-separated ground state can exist. Here the 2-color ``ordered'' phase consists of [A] cells and [A(1/4)B(3/4)] cells. The situation is similar to frustrated ferro- and antiferromagnets on a kagome lattice. Instead of the spins flipping, it is the molecules that undergo 180 degree rotations about the axis of their rod-like cores [Science 331, 1302 (2011)].
Advanced radiator concepts utilizing honeycomb panel heat pipes (stainless steel)
Fleischman, G. L.; Tanzer, H. J.
1985-08-01
The feasibility of fabricating and processing moderate temperature range heat pipes in a low mass honeycomb sandwich panel configuration for highly efficient radiator fins for the NASA space station was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts were evaluated within constraints dictated by existing manufacturing technology and equipment. Concepts evaluated include: type of material, material and panel thicknesses, wick type and manufacturability, liquid and vapor communication among honeycomb cells, and liquid flow return from condenser to evaporator facesheet areas. In addition, the overall performance of the honeycomb panel heat pipe was evaluated analytically.
Institute of Scientific and Technical Information of China (English)
张玉敏; 苏幼坡; 苏经宇
2013-01-01
The new beam-column and concrete-filled steel tubular column-flat plate composite structure is characterized by the joint with dedicated connection device ( hinged connection) between steel columns and concrete slab. The nodes bear only vertical loads while the horizontal loads are born by the shear wall and beam-column frame, and the unbalanced moment in the joint should be very small even naught to avoid the punching damage of slab when an earthquake occurs. The new structure is different from the general frame-shear wall or slab-column structure, therefore the experiment should be implemented to study the performance of the floor system. Through a model test of concrete filled steel tubular (CFST) column-flat plate structure (inter-cross with less than 3) with 1/2-scale, the mechanical performance should be studied under vertical uniform and horizontal loads. Results show that the bearing capacity of the floor system with high security reserves is 2 times higher than the vertical design load; the relative displacement of the joint can achieve 2. 25 % of storey height that is two times more of a frame structure's story drift limit in Code for Seismic Design of Building Structure before the specimens were destroyed even in high ratio of shearing force from the weight of superstructure and punching shear capacity of slabs (gravity shear ratio, GSR >0. 8) . The seismic behavior exceeds ordinary flat floor slab.%新型梁柱-钢管混凝土板柱混合结构的特点是钢管混凝土柱-板节点处只承担竖向荷载,不出现或者出现较小的不平衡弯矩,同时提高节点抗侧移能力,避免地震时楼板发生冲切破坏,水平荷载则全部由抗震墙和梁柱框架承担.通过1个1/2比例钢筋混凝土梁柱-钢管混凝土柱无梁楼盖异型板(跨数少于3跨)结构模型试验,研究其在受竖向均布荷载和水平荷载作用下结构的受力性能.试验结果表明,楼盖系统的竖向承载力超出设计荷载的2倍以上,
Effects of Key Parameters on Thermal Performance of Solar Flat-Plate Collector%太阳能平板集热器关键参数对其热性能的影响
Institute of Scientific and Technical Information of China (English)
车永毅; 厚彩琴
2016-01-01
为了提升太阳能在建筑能源供给体系中的比重，形式多样的太阳能集热设备及其系统在建筑领域得到了广泛应用。基于机理分析法，建立了具有单层玻璃盖板的管板式太阳能平板集热器的稳态传热模型。并且针对集热管间距、集热管内径、工质入口温度和工质质量流量等关键参数对集热器集热效率的影响特性进行了数值模拟与分析。结果表明，建立的该稳态传热模型是可行的；此外，在其余参数值保持不变的情况下，减小集热管间距或增加集热管内径均可使集热器瞬时效率增大；增大工质入口温度会导致集热器瞬时效率下降；而增大工质质量流量会提升集热器瞬时效率。这些结论对于太阳能平板集热器在太阳能建筑一体化的实际应用中，具有一定的参考作用。%In order to improve the proportion of solar energy in building energy supply system, various forms of solar heat collection equipment and systems in the construction field has been widely used. Based on the mechanism analysis method, one steady-state heat transfer model of the single glass cover flat-plate collector is built. The numerical simulation and analysis of the effect of the key parameters including col-lector tube spacing, collector tube diameter, and inlet temperature and inlet mass flow rate of the working fluid on heat collection efficiency of the collector is carried out. The results show that the steady-state heat transfer model is feasible;and in the case of the same parameters, either reducing the collector tube spacing or increasing the collector tube diameter can increase the instantaneous efficiency of the collector; the instantaneous efficiency of the collector decline with the increase of inlet temperature of the working fluid. However, increasing the mass flow rate at the entrance can improve the instantaneous efficiency of the collector. These conclusions have a certain
Institute of Scientific and Technical Information of China (English)
徐国宾; 王永鹏; 高仕赵; 刘昉
2011-01-01
Based on the basic principle of smoothed particle hydrodynamics ( SPH ) method, the paper gave 2 - D SPH Fortran program to make numerical simulations for Poiseuille flow and Couette flow which are Laminar Flow between two parallel flat plates after a comprehensive consideration of several kinds of settings on solution conditions. Compared SPH with theoretical analysis solution and simulation results which use Flow-3D numerical simulation software, this paper discovers that they are very anastomosis. The results realized a verification for the SPH mathematical model and 2 - D SPH Fortran program, supplied theoretical support and laid a good foundation for the use and development of SPH in the future.%基于SPH方法的基本原理,综合考虑了对各种定解条件的设置,用Fortran语言独立编写了一套用于模拟两平行平板间层流的SPH二维计算程序,并应用于泊肃叶流和库埃特流的数值模拟之中,将模拟结果与理论解析解和通过Flow -3D软件数值模拟得到的数值结果进行对比,分析表明三种方法得到的计算结果非常吻合,从而实现了对SPH数学模型和SPH计算程序的验证,为SPH方法的进一步发展和广泛应用奠定了一定的基础.
Experimental Analysis of Serpentine-flow Flat-plate Solar Collector%蛇形管平板式太阳能集热器的试验研究
Institute of Scientific and Technical Information of China (English)
李俊贤; 王辉涛; 王华; 包桂蓉
2011-01-01
A serpentine-flow flat-plate solar collector of small volume and large temperature difference is designed and developed in order to explore the fiat-plate solar collector used in high temperature situation. And experiment of stagnation and instantaneous efficiency is carried out. The results shown that stagnation temperature can reach 170.2 ℃ and heat loss coefficient is 5. 239 W/( m2 · ℃ ). Efficiency of solar collector between 52％ —55％ when inlet temperature of working fluid is 70 ℃. By comparison the temperature trend of various parts of the collector the corrective measure is proposed to improve performance of serpentine-flow fiat-plate solar collector in high temperature conditions.%为了探寻一种在中高温场合使用的平板式太阳能集热器,设计和开发了小流量、大温差的蛇形管平板式太阳能集热器,并进行了空晒试验和瞬时效率试验.试验结果表明:集热器的空晒温度可达170.2℃,热损系数为5.239 W/(m2·℃),载热工质进口温度70℃时效率52%-55%.通过对集热器各部分温度变化趋势的比较,提出改进措施,以提高蛇形管平板式集热器在中高温工况下的集热性能.
High temperature flat plate solar collector
Energy Technology Data Exchange (ETDEWEB)
Hozumi, S.; Aso, S.; Ebisu, K.; Uchino, H.
1981-04-01
Improvements in the efficiency of collectors are of great importance for extending the utilization of solar energy for heating and cooling in homes. A highly efficient collector makes the system size small and decreases the system cost effectively. From the view of the amount of energy collected, the efficient collector has a multiple effect, not only because of the high increase in instantaneous efficiency, but also because of the large usable intensity range of the insolation. On the basis of a functional analysis for a flat collector, the materials and parameters were selected and optimized, and a new high temperature flat collector was designed. The collector has 2 panes. The first pane is low iron glass and the second pane is a thin film of fluorinated ethylene-propylene copolymer. The overall solar transmittance for the two panes is 0.89. The collecting panel and its water paths were formed by means of welding and hydraulic expansion. The selective absorbing surface consists of colored stainless steel whose absorption characteristic is 0.89 and emission characteristic is 0.16. The thermal insulator preventing backward heatloss consists of double layers of urethane foam and glass wool. Furthermore, the sustained method for the second pane is contrived so as to prevent water condensation on the panes and excessive elevation of the absorber temperature during no load heating.
Operational success - Flat-plate photovoltaic systems
Risser, V. V.; Zwibel, H. S.
The performance-to-date of 20 and 100 kW peak DOE photovoltaic array demonstration projects in New Mexico and Texas are reported. An El Paso 20 kW unit feeds power to an uninterruptible power supply for a computer controlling a 197 MW generator. System availability has been 97 percent after over 800 days of operation, and has reached monthly efficiencies of 5.3-6.2 percent. The Lovington, NM 100 kW unit has operated at an average 6.7 percent efficiency, furnishing over 15.8 MWh/mo for a 2 yr period. System availability has been 99 percent, although at increased costs due to regular maintenance.
Institute of Scientific and Technical Information of China (English)
朱婷婷; 刁彦华; 赵耀华; 马骋; 李凤飞
2016-01-01
In common types of flat-plate solar air heaters, the uneven flow and heat exchange between air and an absorber plate poses a problem. To resolve this problem, this paper proposed a novel type of flat-plate solar air heater based on micro-heat pipe arrays (MHPA). An investigation was carried out on the design, thermal performance and flow resistance characteristic of the novel heater based on micro-heat pipe arrays. The new air collector consists of 15 MHPAs with V-shaped fins attached to the heat release (condenser) section, absorber film, insulation board, bottom plate, and air ventilation and heat exchange section. The components of the heater include the toughened glass cover, air layer (35 mm), MHPA-absorber plate, thermal insulation layer, and the back board. Solar energy is absorbed by the MHPA evaporator section with the organic combination of high efficiency absorber film, which formed a heat pipe effect within each micro heat pipe arrays. The heat has been released to the air in the ventilation and heat exchange section of the heater, whereas the air was eventually warmed. Simultaneously, the working medium in MHPA proceeds continuous phase transition cycle and continuously passes solar radiation heat to air in the air duct with high efficiency. The MHPA heat-absorbing plate core can realize the whole area of heat absorption, high efficient heat transmission, and large surface of heat release. The total solar energy is received by the heater, and some energy is transferred to the air flow in the air duct as useful energy; the remaining energy is lost mainly through the glass cover, frames, bottom plate, and air duct. The heat loss through the frames and the air duct can be ignored because of good heat preservation condition. So the glass cover becomes the main source of heat loss. Thermal analysis shows that heat loss through the glass cover occupies the largest proportion of the total heat loss of the heater.To test the new heater thermal efficiency and
Energy Technology Data Exchange (ETDEWEB)
Haneda, Y.; Kurasawa, H. (Nagano National College of Technology, Nagano (Japan)); Tsuchiya, Y. (Shinshu Univ., Nagano (Japan). Faculty of Engineering); Suzuki, K. (Kyoto Univ., Kyoto (Japan). Faculty of Engineering)
1994-04-25
The flow field and heat transfer around a circular cylinder is investigated experimentally when two dimensional jet is impinged on a circular cylinder mounted near two flat plates which are set at a fixed inclination against the axis of jet. Flow field varies markedly depending on whether the minimum channel width is the minimum space B between the flat plates or the space C between the cylinder and the plates. The local Nusselt number of the cylinder strongly depends on the value of space C between the cylinder and the plates. The minimum and maximum locations correspond to the locations of separation and reattachment, respectively, of the flow around the cylinder. When the ratio between the nozzle-to-cylinder distance L and the short side h of the nozzle is 3 (L/h=3), the mean Nusselt number around the cylinder becomes the maximum when C/D is 0.1 where D is the diameter of the cylinder, and increases by about 9 to 12% as compared with the case where no plate is provided. For L/h=7 and L/h=10, the mean Nusselt number does not increase distinctly as compared with the case where no flat plate is provided. 16 refs., 15 figs.
Study of Two-Dimensional Materials with Honeycomb Geometry
Boneschanscher, M.P.
2014-01-01
Honeycomb structures have already fascinated mankind since ancient times. They were observed in various natural occurring phenomena, from the structure of the beehive of the honeybee that granted the structure its name, to the inner structure of butterfly wings, bones, and insect eyes. The honeycomb
Clean Electrical-Discharge Machining Of Delicate Honeycomb
Johnson, Clarence S.
1993-01-01
Precise recesses in fragile metal honeycomb blocks formed in special electrical-discharge machining process. Special tooling used, and recesses bored with workpiece in nonstandard alignment. Cutting electrode advances into workpiece along x axis to form pocket of rectangular cross section. Deionized water flows from fitting, along honeycomb tubes of workpiece, to electrode/workpiece interface.
Institute of Scientific and Technical Information of China (English)
郑土逢; 李明; 魏生贤; 罗熙; 王炳灿
2011-01-01
The device of natural circulation flat plate solar water heater has been built.In accordance with the national testing standard methods, the efficiency of the system was tested.The transient model of NFSWH has been developed by using the TRNSYS simulation program.The effect of installation height between the bottom of the tank and the outlet of the collector on efficiency of the solar collector has been investigated both theoretically and experimentally.The data show the theoretical results are highly consistent with the experimental ones.Results indicate that the optimum value of installation height is 0.74m with the maximum efficiency of 67.5％ for the system with a total area of 1.5m2 and a storage water tank capacity of 120L.When the installation height is between 0.44 and 1.04 m, the change of thermal efficiency of the solar system is at a range of 3％.%搭建了自然循环平板式太阳能热水器(NFSWH)的实验平台,根据太阳能热水器国家测试标准方法对系统的热效率进行测试.用TRNSYS软件建立了NFSWH的瞬态模型.模拟和实际测量了水箱放置高度对热水器热效率的影响.结果显示,实验与模拟吻合较好.对于集热面积为1.5m2水箱容积为120L的系统,水箱底到集热器出口的高度(Hr)为0.74m时,系统的热效率最大(67.7%).放置高度为0.44-1.04m时,系统集热效率变化不大,在3%以内.
49 CFR 587.15 - Verification of aluminum honeycomb crush strength.
2010-10-01
... 49 Transportation 7 2010-10-01 2010-10-01 false Verification of aluminum honeycomb crush strength... Deformable Barrier § 587.15 Verification of aluminum honeycomb crush strength. The following procedure is used to ascertain the crush strength of the main honeycomb block and the bumper element honeycomb,...
Super-honeycomb lattice: A hybrid fermionic and bosonic system
Zhong, Hua; Zhu, Yi; Zhang, Da; Li, Changbiao; Zhang, Yanpeng; Li, Fuli; Belić, Milivoj R; Xiao, Min
2016-01-01
We report on transport properties of the super-honeycomb lattice, the band structure of which possesses a flat band and Dirac cones, according to the tight-binding approximation. This super-honeycomb model combines the honeycomb lattice and the Lieb lattice and displays the properties of both. The super-honeycomb lattice also represents a hybrid fermionic and bosonic system, which is rarely seen in nature. By choosing the phases of input beams properly, the flat-band mode of the super-honeycomb will be excited and the input beams will exhibit a strong localization during propagation. On the other hand, if the modes of Dirac cones of the super-honeycomb lattice are excited, one will observe conical diffraction. Furthermore, if the input beam is properly chosen to excite a sublattice of the super-honeycomb lattice and the modes of Dirac cones with different pseudospins, e.g., the three-beam interference pattern, the pseudospin-mediated vortices will be observed.
The use of COD and plastic instability in crack propagation and arrest in shells
Erdogan, F.; Ratwani, M.
1974-01-01
The initiation, growth, and possible arrest of fracture in cylindrical shells containing initial defects are dealt with. For those defects which may be approximated by a part-through semi-elliptic surface crack which is sufficiently shallow so that part of the net ligament in the plane of the crack is still elastic, the existing flat plate solution is modified to take into account the shell curvature effect as well as the effect of the thickness and the small scale plastic deformations. The problem of large defects is then considered under the assumptions that the defect may be approximated by a relatively deep meridional part-through surface crack and the net ligament through the shell wall is fully yielded. The results given are based on an 8th order bending theory of shallow shells using a conventional plastic strip model to account for the plastic deformations around the crack border.
Damping capacity in shape memory alloy honeycomb structures
Boucher, M.-A.; Smith, C. W.; Scarpa, F.; Miller, W.; Hassan, M. R.
2010-04-01
SMA honeycombs have been recently developed by several Authors [1, 2] as innovative cellular structures with selfhealing capability following mechanical indentation, unusual deformation (negative Poisson's ratio [3]), and possible enhanced damping capacity due to the natural vibration dissipation characteristics of SMAs under pseudoelastic and superelastic regime. In this work we describe the nonlinear damping effects of novel shape memory alloy honeycomb assemblies subjected to combine mechanical sinusoidal and thermal loading. The SMA honeycomb structures made with Ni48Ti46Cu6 are designed with single and two-phase polymeric components (epoxy), to enhance the damping characteristics of the base SMA for broadband frequency vibration.
Crystallography of rare galactic honeycomb structure near supernova 1987a
Noever, David A.
1994-01-01
Near supernova 1987a, the rare honeycomb structure of 20-30 galactic bubbles measures 30 x 90 light years. Its remarkable regularity in bubble size suggests a single-event origin which may correlate with the nearby supernova. To test the honeycomb's regularity in shape and size, the formalism of statistical crystallography is developed here for bubble sideness. The standard size-shape relations (Lewis's law, Desch's law, and Aboav-Weaire's law) govern area, perimeter and nearest neighbor shapes. Taken together, they predict a highly non-equilibrium structure for the galactic honeycomb which evolves as a bimodal shape distribution without dominant bubble perimeter energy.
Simulation of the honeycomb construction process
Yuanzhang, Zhang
2010-06-01
The construction process of the honeycomb by bees is an astonishing process. The original structure which the bees built is nothing more than a lot of rough cylinders. But keeping the beeswax semi-flow for a certain time, those rough structures become perfect hexahedral columns. A modified, simplified particle method was used here to simulate the semi-flow state of the material. Although the parameters used here were still rather subjective, the simulation still could demonstrate some behavior of that sort of material like beeswax. And the method that the bees used to build their honey comb, could be an efficient method to imitate when we are trying to manufacture cellular materials.
Energy Technology Data Exchange (ETDEWEB)
Lu, Wei-Yang [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials; Korellis, John S. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials; Lee, Kenneth L. [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials; Scheffel, Simon [Sandia National Lab. (SNL-CA), Livermore, CA (United States). Mechanics of Materials; Hinnerichs, Terry Dean [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Solid Mechanics; Neilsen, Michael K. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Applied Mechanics Development; Scherzinger, William Mark [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Solid Mechanics
2006-08-01
Honeycomb is a structure that consists of two-dimensional regular arrays of open cells. High-density aluminum honeycomb has been used in weapon assemblies to mitigate shock and protect payload because of its excellent crush properties. In order to use honeycomb efficiently and to certify the payload is protected by the honeycomb under various loading conditions, a validated honeycomb crush model is required and the mechanical properties of the honeycombs need to be fully characterized. Volume I of this report documents an experimental study of the crush behavior of high-density honeycombs. Two sets of honeycombs were included in this investigation: commercial grade for initial exploratory experiments, and weapon grade, which satisfied B61 specifications. This investigation also includes developing proper experimental methods for crush characterization, conducting discovery experiments to explore crush behaviors for model improvement, and identifying experimental and material uncertainties.
... Surgery? A Week of Healthy Breakfasts Shyness Plastic Surgery KidsHealth > For Teens > Plastic Surgery Print A A ... forehead lightened with a laser? What Is Plastic Surgery? Just because the name includes the word "plastic" ...
C-SiC Honeycomb for Advanced Flight Structures Project
National Aeronautics and Space Administration — The proposed project is to manufacture a C-SiC honeycomb structure to use as a high temperature material in advanced aircraft, spacecraft and industrial...
Institute of Scientific and Technical Information of China (English)
宋瞡毅
2015-01-01
Gypsum embedded filler flat plate floor,which uses precast gypsum embedded fillers as permanent formworks, is a monolithic cast-in-situ hollow concrete floor system.There are five kinds of structures.They are waffle slab,composite open-web floor,composite cross-beam and open-web floor,cross-beam floor,and nine-rectangle-grid floor.According to topology optimization of solid floor structure of two or three spans by ANSYS,72 false density distributions have been ob-tained.On the basis of the above results,a new structural model with composite hidden-prop-cap and cantilever-three-rib floor can be designed.Through the static analysis under vertical load by ANSYS,deflection and stress distribution of com-posite hidden-prop-cap and cantilever-three-rib floor are studied in detail.The results show that the stress of composite hid-den-prop-cap and cantilever-three-rib floor does not take on obvious characteristics of solid floor.So its strength of concrete and reinforcement does not been fully used and its reinforcement design will be complex.However,the composite hidden-prop-cap and cantilever-three-rib floor is suitable for those buildings which large span and whose floors under big loads be-cause of the less consumptions of concrete,good vertical rigidity and small peak tensile stress.%石膏空腔模无梁楼盖是以预制石膏空腔模为永久性施工内模的整体现浇空心楼盖，有密肋式、空腹板架式、井字－空腹板架组合式、井式、9区格式五种结构。用 ANSYS 对不同情况下的双跨、三跨楼盖做拓扑优化，得到72张单元伪密度云图并归纳伪密度分布规律，在此基础上设计一种新型结构———暗柱帽－悬挑三肋楼盖。用 AN-SYS 对暗柱帽－悬挑三肋楼盖做竖向荷载作用下的静力特性理论分析，详细研究其挠度和正应力分布。研究表明：暗柱帽－悬挑三肋楼盖的正应力分布不呈实体板特征，不利于发挥材料强度和配筋设计；
Institute of Scientific and Technical Information of China (English)
王淋淋; 尤学一
2012-01-01
The computational fluid dynamics was applied to simulate the flow field of a flat plate photobioreactor (PBR) with waved baffle panel. After the reliability of model was validated, the effects of two structural parameters of waved baffles, i.e. the ratio of waved baffles height to wave length (L/λX) and ratio of wave amplitude to wave length (A/λ) on the mass transfer and mixing performance were systematically analyzed. The results showed that when L/λ=12, better mass transfer and mixing performance were obtained and those related parameters such as the liquid volumetric mass transfer coefficient (kLa), ratio of cycle time of the downcomer to that of PBR (ff) and averaged turbulence kinetic energy (Em) were higher. Besides, the obtained liquid velocity was close to the optimum value being most favorable to microalgal growth. When L/λ12 and A/λ=0.8, the mass transfer performance was the best and the value of kLa was increased by about 10% compared with that of bioreactor with flat baffles. As L//b=l2 and A/λ0.4, the mixing performance of the reactor was the best and the value of Em was increased by 14.7% compared with that of bioreactor with flat baffles.%对带波纹隔板的平板式生物反应器,利用计算流体动力学进行流场模拟,验证模型可靠性后,系统分析波纹隔板高/波长(L/λ)和波幅/波长(A/λ)两个波纹隔板结构参数对反应器传质及流动混合特性的影响.结果表明,当L/λ=12时,传质及流动混合性能较好,液相体积传质系数(kLa)、平均湍动能(Em)、下降区停留时间占循环一周时间之比(θ)等表征传质及混合的参数值均较大,得到的液体流速在微藻生长的最佳流速附近.当A/λ=0.8时,反应器的传质性能最优,kLa比采用平直隔板时增加了约10％;当A/λ=0.4时,反应器的混合效果最佳,Em比采用平直隔板时增加14.7％.
Evaluation of Ceramic Honeycomb Core Compression Behavior at Room Temperature
Bird, Richard K.; Lapointe, Thomas S.
2013-01-01
Room temperature flatwise compression tests were conducted on two varieties of ceramic honeycomb core specimens that have potential for high-temperature structural applications. One set of specimens was fabricated using strips of a commercially-available thin-gage "ceramic paper" sheet molded into a hexagonal core configuration. The other set was fabricated by machining honeycomb core directly from a commercially available rigid insulation tile material. This paper summarizes the results from these tests.
Jackson, Karen E.; Fasanella, Edwin L.; Polanco, Michael A.
2012-01-01
This paper describes the experimental and analytical evaluation of an externally deployable composite honeycomb structure that is designed to attenuate impact energy during helicopter crashes. The concept, designated the Deployable Energy Absorber (DEA), utilizes an expandable Kevlar (Registered Trademark) honeycomb to dissipate kinetic energy through crushing. The DEA incorporates a unique flexible hinge design that allows the honeycomb to be packaged and stowed until needed for deployment. Experimental evaluation of the DEA included dynamic crush tests of multi-cell components and vertical drop tests of a composite fuselage section, retrofitted with DEA blocks, onto multi-terrain. Finite element models of the test articles were developed and simulations were performed using the transient dynamic code, LSDYNA (Registered Trademark). In each simulation, the DEA was represented using shell elements assigned two different material properties: Mat 24, an isotropic piecewise linear plasticity model, and Mat 58, a continuum damage mechanics model used to represent laminated composite fabrics. DEA model development and test-analysis comparisons are presented.
Directory of Open Access Journals (Sweden)
Weigelt C.
2012-08-01
Full Text Available Two designs of square-celled metallic honeycomb structures fabricated by a modified extrusion technology based on a powder feedstock were investigated. The strength and ductility of these cellular materials are achieved by an austenitic CrNi (AISI 304 steel matrix particle reinforced by an MgO partially-stabilized zirconia building up their cell wall microstructure. Similar to the mechanical behaviour of the bulk materials, the strengthening mechanism and the martensitic phase transformations in the cell walls are affected by the deformation temperature and the nominal strain rate. The microstructure evolution during quasi-static and dynamic impact compression up to high strain rates of 103 1/s influences the buckling and failure behaviour of the honeycomb structures. In contrast to bending-dominated quasi-isotropic networks like open-celled metal foams, axial compressive loading to the honeycomb’s channels causes membrane stretching as well as crushing of the vertical cell node elements and cell walls. The presented honeycomb materials differ geometrically in their cell wall thickness-to-cell size-ratio. Therefore, the failure behaviour is predominantly controlled by global buckling and torsional-flexural buckling, respectively, accompanied by plastic matrix flow and strengthening of the cell wall microstructure.
Cahyono, Sukmaji Indro; Widodo, Angit; Anwar, Miftahul; Diharjo, Kuncoro; Triyono, Teguh; Hapid, A.; Kaleg, S.
2016-03-01
The carbon fiber reinforced plastic (CFRP) composite is relative high cost material in current manufacturing process of electric vehicle body structure. Sandwich panels consisting polypropylene (PP) honeycomb core with hybrid carbon-glass fiber composite skin were investigated. The aim of present paper was evaluate the flexural properties and bending rigidity of various volume fraction carbon-glass fiber composite skins with the honeycomb core. The flexural properties and cost of panels were compared to the reported values of solid hybrid Carbon/Glass FRP used for the frame body structure of electric vehicle. The finite element model of represented sandwich panel was established to characterize the flexural properties of material using homogenization technique. Finally, simplified model was employed to crashworthiness analysis for engine hood of the body electric vehicle structure. The good cost-electiveness of honeycomb core with hybrid carbon-glass fiber skin has the potential to be used as a light-weight alternative material in body electric vehicle fabricated.
Edge states in polariton honeycomb lattices
Milićević, M.; Ozawa, T.; Andreakou, P.; Carusotto, I.; Jacqmin, T.; Galopin, E.; Lemaître, A.; Le Gratiet, L.; Sagnes, I.; Bloch, J.; Amo, A.
2015-09-01
The experimental study of edge states in atomically thin layered materials remains a challenge due to the difficult control of the geometry of the sample terminations, the stability of dangling bonds, and the need to measure local properties. In the case of graphene, localized edge modes have been predicted in zigzag and bearded edges, characterized by flat dispersions connecting the Dirac points. Polaritons in semiconductor microcavities have recently emerged as an extraordinary photonic platform to emulate 1D and 2D Hamiltonians, allowing the direct visualization of the wavefunctions in both real- and momentum-space as well as of the energy dispersion of eigenstates via photoluminescence experiments. Here we report on the observation of edge states in a honeycomb lattice of coupled micropillars. The lowest two bands of this structure arise from the coupling of the lowest energy modes of the micropillars, and emulate the π and π* bands of graphene. We show the momentum-space dispersion of the edge states associated with the zigzag and bearded edges, holding unidimensional quasi-flat bands. Additionally, we evaluate polarization effects characteristic of polaritons on the properties of these states.
Method of fabricating lightweight honeycomb structures
Goela, Jitendra S. (Inventor); Pickering, Michael (Inventor); Taylor, Raymond L. (Inventor)
1992-01-01
A process is disclosed for fabricating lightweight honeycomb type structures out of material such as silicon carbide (SiC) and silicon (S). The lightweight structure consists of a core to define the shape and size of the structure. The core is coated with an appropriate deposit such as SiC or Si to give the lightweight structure strength and stiffness and for bonding the lightweight structure to another surface. The core is fabricated from extremely thin ribs of appropriately stiff and strong material such as graphite. First, a graphite core consisting of an outer hexagonal cell with six inner triangular cells is constructed from the graphite ribs. The graphite core may be placed on the back-up side of a SiC faceplate and then coated with SiC to produce a monolithic structure without the use of any bonding agent. Cores and methods for the fabrication thereof in which the six inner triangular cells are further divided into a plurality of cells are also disclosed.
Institute of Scientific and Technical Information of China (English)
邓月超; 赵耀华; 全贞花; 刘中良
2015-01-01
In this paper, a three-dimensional CFD numerical model of heat transfer and fluid flow was developed to simulate the thermal performance of the novel flat plate solar collector based on a micro heat pipe array to provide a theoretical basis for the structure improvement and optimization of the collector. The simulation of the novel collector with water flow included the CFD modeling of solar irradiation and the modes of mixed convection and radiation heat transfer between the absorber plate and glass cover, as well as the heat transfer in the circulating water inside the heat exchanger and conduction of the insulation. The fluid flow and heat transfer in the computational domain satisfied the continuity equation, the momentum equation, and the energy equation. The standardk-ε two-equation turbulence model was used in this paper. In order to predict the direct illumination energy source that results from incident solar radiation and the radiation field inside the collector, the discrete ordinate radiation model with a solar ray-tracing model was used. A commercial computational fluid dynamics program (Fluent 6.3 CFD software) was used to solve the coupled fluid flow, heat transfer, and the radiation equation. The solver used is the segregated solver. Body Force Weighted was selected as the discretization method for pressure, and the SIMPLE algorithm was used to resolve the coupling between pressure and velocity. The discretization methods for the solving of momentum, energy, radiation, and turbulence were second order upwind. The thermal performance could be achieved by simulation results under different conditions. Then, the experimental and numerical results were compared to validate the prediction of the CFD model. The results showed that the numerical results of the thermal efficiency of the novel collector were in reasonable agreement with the experimental data. The validated CFD model was used to analyze the properties of the insulation layer. First, the
Multiscale Finite-Element Modeling of Sandwich Honeycomb Composite Structures
Directory of Open Access Journals (Sweden)
Yu. I. Dimitrienko
2014-01-01
Full Text Available The paper presents a developed multi-scale model of sandwich honeycomb structures. The model allows us both to calculate effective elastic-strength characteristics of honeycomb and forced covering of sandwich, and to find a 3D stress-strain state of structures using the threedimensional elastic theory for non- homogeneous media. On the basis of finite element analysis it is shown, that under four-point bending the maximal value of bending and shear stresses in the sandwich honeycomb structures are realized in the zone of applied force and plate support. Here the local stress maxima approximately 2-3 times exceed the “engineering” theoretical plate values of bending and shear stresses in the middle of panel. It is established that at tests for fourpoint bending there is a failure of the honeycomb sandwich panels because of the local adhesion failure rather than because of the covering exfoliation off the honeycomb core in the middle of panel.
Deformation of Honeycomb with Finite Boundary Subjected to Uniaxial Compression
Directory of Open Access Journals (Sweden)
Dai-Heng Chen
2013-11-01
Full Text Available In this paper, the crushing behavior of hexagonal honeycomb structures with finite boundaries (finite width and height subjected to in-plane uniaxial compressive loading is studied based on the nonlinear finite element analysis. It is found that stress-strain responses for the honeycombs with finite boundaries can be classified into two types: Type I and Type II. Such a characteristic is affected by the wall thickness, the work-hardening coefficient and the yield stress for the honeycombs. Furthermore, a transition from the symmetric to asymmetric deformation mode can be observed in Type I, and these deformed cells were localized in a horizontal layer. However, for the case of Type II response, the symmetric and asymmetric deformation modes can be observed simultaneously, and the region of the asymmetric mode was formed by the cell layer along the diagonal direction. As a result, the shear deformation behavior was developed along that direction. Moreover, the effect of work-hardening on the deformation behavior for the honeycombs with finite boundaries can be explained from that for infinite honeycombs.
Nonlinear Modeling and Identification of an Aluminum Honeycomb Panel with Multiple Bolts
Directory of Open Access Journals (Sweden)
Yongpeng Chu
2016-01-01
Full Text Available This paper focuses on the nonlinear dynamics modeling and parameter identification of an Aluminum Honeycomb Panel (AHP with multiple bolted joints. Finite element method using eight-node solid elements is exploited to model the panel and the bolted connection interface as a homogeneous, isotropic plate and as a thin layer of nonlinear elastic-plastic material, respectively. The material properties of a thin layer are defined by a bilinear elastic plastic model, which can describe the energy dissipation and softening phenomena in the bolted joints under nonlinear states. Experimental tests at low and high excitation levels are performed to reveal the dynamic characteristics of the bolted structure. In particular, the linear material parameters of the panel are identified via experimental tests at low excitation levels, whereas the nonlinear material parameters of the thin layer are updated by using the genetic algorithm to minimize the residual error between the measured and the simulation data at a high excitation level. It is demonstrated by comparing the frequency responses of the updated FEM and the experimental system that the thin layer of bilinear elastic-plastic material is very effective for modeling the nonlinear joint interface of the assembled structure with multiple bolts.
Graphene-like monolayer low-buckled honeycomb germanium film
He, Yezeng; Luo, Haibo; Li, Hui; Sui, Yanwei; Wei, Fuxiang; Meng, Qingkun; Yang, Weiming; Qi, Jiqiu
2017-04-01
Molecular dynamics simulations have been performed to study the cooling process of two-dimensional liquid germanium under nanoslit confinement. The results clearly indicates that the liquid germanium undergoes an obvious liquid-solid phase transition to a monolayer honeycomb film with the decrease of temperature, accompanying the rapid change in potential energy, atomic volume, coordination number and lateral radial distribution function. During the solidification process, some hexagonal atomic islands first randomly emerge in the disordered liquid film and then grow up to stable crystal grains which keep growing and finally connect together to form a honeycomb polycrystalline film. It is worth noting that the honeycomb germanium film is low-buckled, quite different from the planar graphene.
Two-Scale Analysis of Honeycombs Indented by Flat Punch
Asada, Takashi; Tanaka, Yuji; Ohno, Nobutada
The fully implicit incremental homogenization scheme developed by Asada and Ohno (2007) for elastoplastic periodic solids is applied to two-scale analysis of honeycomb blocks subjected to flat punch indentation. To this end, the scheme is rebuilt by introducing half unit cells based on the point-symmetric distributions of stress and strain in unit cells, so that analysis domains in unit cells are reduced by half. Then, by assuming the zigzag and armchair types of cell-arrangements, the two-scale analysis of honeycomb blocks is performed. The corresponding full-scale finite element analysis is also performed to reveal the cell-arrangement dependence of cell deformation in the honeycomb blocks. It is shown that the two-scale analysis is macroscopically successful in spite of microscopic limitations.
A first theoretical realization of honeycomb topological magnon insulator
Owerre, S. A.
2016-09-01
It has been recently shown that in the Heisenberg (anti)ferromagnet on the honeycomb lattice, the magnons (spin wave quasipacticles) realize a massless two-dimensional (2D) Dirac-like Hamiltonian. It was shown that the Dirac magnon Hamiltonian preserves time-reversal symmetry defined with the sublattice pseudo spins and the Dirac points are robust against magnon-magnon interactions. The Dirac points also occur at nonzero energy. In this paper, we propose a simple realization of nontrivial topology (magnon edge states) in this system. We show that the Dirac points are gapped when the inversion symmetry of the lattice is broken by introducing a next-nearest neighbour Dzyaloshinskii-Moriya (DM) interaction. Thus, the system realizes magnon edge states similar to the Haldane model for quantum anomalous Hall effect in electronic systems. However, in contrast to electronic spin current where dissipation can be very large due to Ohmic heating, noninteracting topological magnons can propagate for a long time without dissipation as magnons are uncharged particles. We observe the same magnon edge states for the XY model on the honeycomb lattice. Remarkably, in this case the model maps to interacting hardcore bosons on the honeycomb lattice. Quantum magnetic systems with nontrivial magnon edge states are called topological magnon insulators. They have been studied theoretically on the kagome lattice and recently observed experimentally on the kagome magnet Cu(1-3, bdc) with three magnon bulk bands. Our results for the honeycomb lattice suggests an experimental procedure to search for honeycomb topological magnon insulators within a class of 2D quantum magnets and ultracold atoms trapped in honeycomb optical lattices. In 3D lattices, Dirac and Weyl points were recently studied theoretically, however, the criteria that give rise to them were not well-understood. We argue that the low-energy Hamiltonian near the Weyl points should break time-reversal symmetry of the pseudo spins
Topology optimization of pressure adaptive honeycomb for a morphing flap
Vos, Roelof; Scheepstra, Jan; Barrett, Ron
2011-03-01
The paper begins with a brief historical overview of pressure adaptive materials and structures. By examining avian anatomy, it is seen that pressure-adaptive structures have been used successfully in the Natural world to hold structural positions for extended periods of time and yet allow for dynamic shape changes from one flight state to the next. More modern pneumatic actuators, including FAA certified autopilot servoactuators are frequently used by aircraft around the world. Pneumatic artificial muscles (PAM) show good promise as aircraft actuators, but follow the traditional model of load concentration and distribution commonly found in aircraft. A new system is proposed which leaves distributed loads distributed and manipulates structures through a distributed actuator. By using Pressure Adaptive Honeycomb (PAH), it is shown that large structural deformations in excess of 50% strains can be achieved while maintaining full structural integrity and enabling secondary flight control mechanisms like flaps. The successful implementation of pressure-adaptive honeycomb in the trailing edge of a wing section sparked the motivation for subsequent research into the optimal topology of the pressure adaptive honeycomb within the trailing edge of a morphing flap. As an input for the optimization two known shapes are required: a desired shape in cruise configuration and a desired shape in landing configuration. In addition, the boundary conditions and load cases (including aerodynamic loads and internal pressure loads) should be specified for each condition. Finally, a set of six design variables is specified relating to the honeycomb and upper skin topology of the morphing flap. A finite-element model of the pressure-adaptive honeycomb structure is developed specifically tailored to generate fast but reliable results for a given combination of external loading, input variables, and boundary conditions. Based on two bench tests it is shown that this model correlates well
Lubliner, Jacob
2008-01-01
The aim of Plasticity Theory is to provide a comprehensive introduction to the contemporary state of knowledge in basic plasticity theory and to its applications. It treats several areas not commonly found between the covers of a single book: the physics of plasticity, constitutive theory, dynamic plasticity, large-deformation plasticity, and numerical methods, in addition to a representative survey of problems treated by classical methods, such as elastic-plastic problems, plane plastic flow, and limit analysis; the problem discussed come from areas of interest to mechanical, structural, and
Titanium honeycomb structure. [for supersonic aircraft wing structure
Davis, R. A.; Elrod, S. D.; Lovell, D. T.
1972-01-01
A brazed titanium honeycomb sandwich system for supersonic transport wing cover panels provides the most efficient structure spanwise, chordwise, and loadwise. Flutter testing shows that high wing stiffness is most efficient in a sandwich structure. This structure also provides good thermal insulation if liquid fuel is carried in direct contact with the wing structure in integral fuel tanks.
Pressure Adaptive Honeycomb: Mechanics, Modeling, and Experimental Investigation
Vos, R.; Barrett, R.
2010-01-01
A new type of adaptive structure is presented that relies on a pressure derential to perform gross structural deformations. This structure relies on highly compliant honey-comb cells that can be pressurized externally or can rely on a pressure differential that exists at elevated altitudes. By
Solitons of a vector model on the honeycomb lattice
Vekslerchik, V. E.
2016-11-01
We study a simple nonlinear vector model defined on the honeycomb lattice. We propose a bilinearization scheme for the field equations and demonstrate that the resulting system is closely related to the well-studied integrable models, such as the Hirota bilinear difference equation and the Ablowitz-Ladik system. This result is used to derive the N-soliton solutions.
Photonic crystal fiber with a hybrid honeycomb cladding
DEFF Research Database (Denmark)
Mortensen, Niels Asger; Nielsen, Martin Dybendal; Folkenberg, Jacob Riis;
2004-01-01
be formed by manipulating the cladding region ratherthan the core region itself. Germanium-doping of the honeycomb lattice has recently been suggested for the formation of a photonic band-gap guiding silica-core and here we experimentally demonstrate how an index-guiding silica-core can be formed...
Chronic interstitial pneumonia with honeycombing in coal workers
Energy Technology Data Exchange (ETDEWEB)
Brichet, A.; Tonnel, A.B.; Brambilla, E.; Devouassoux, G.; Remy-Jardin, M.; Copin, M.C.; Wallaert, B. [A. Calmette Hospital, Lille (France)
2002-10-01
Coal worker's pneumoconiosis (CWP) results from coal mine dust inhalation. The paper reports the presence of a chronic interstitial pneumonia (CIP) with honeycombing in 38 cases of coal miners, with or without CWP. The 38 patients were selected on the basis of clinical criteria which are unusual in CWP, i.e. fine inspiratory crackles and severe dyspnea. There were 37 men and one woman; mean age was 67.5 {+-} 9.1 years. Thirty-two were smokers. Duration of exposure was 26.7 {+-} 9.9 years. All the patients had clinical examination, chest radiography, computed tomography (CT), lung function, laboratory investigations, wedged fiberoptic bronchoscopy with bronchoalveolar lavage (BAL). In eight cases, lung specimens were obtained. Seventeen out of 38 had finger clubbing. 17 had radiological signs of CWP limited to the upper lobes or diffusely distributed. CT showed honeycombing (36 cases), and/or ground glass opacities (30 cases) with traction bronchiectasis (8 cases) predominant in the lower lobes. BAL analysis demonstrated an increased percentage of neutrophils (9.4% {+-} 6). Lung function showed a restrictive pattern associated with a decreased DLCO and hypoxemia. Lung specimens demonstrated in 2 cases a homogenous interstitial fibrosis of intra-alveolar septum with an accumulation of immune and inflammatory cells without temporal variation and with obvious honeycombing. The 6 other cases showed features of usual interstitial pneumonia. These cases, should alert other clinicians to a possible association between CIP with honeycombing and coal dust exposure, with or without associated CWP.
Adsorption characteristics of water vapor on honeycomb adsorbents
Wajima, Takaaki; Munakata, Kenzo; Takeishi, Toshiharu; Hara, Keisuke; Wada, Kouhei; Katekari, Kenichi; Inoue, Keita; Shinozaki, Yohei; Mochizuki, Kazuhiro; Tanaka, Masahiro; Uda, Tatsuhiko
2011-10-01
Recovery of tritium released into working areas in nuclear fusion plants is a key issue of safety. A large volume of air from tritium fuel cycle or vacuum vessel should be processed by air cleanup system (ACS). In ACS, tritium gas is oxidized by catalysts, and then tritiated water vapor is collected by adsorbents. This method can remove tritium effectively, whereas high throughput of air causes high-pressure drop in catalyst and adsorbent beds. In this study, the applicability of honeycomb-type adsorbents, which offers a useful advantage in terms of their low-pressure drop, to ACS was examined, in comparison with conventional pebble-type adsorbent. Honeycomb-type adsorbent causes far less pressure drop than pebble-type adsorbent beds. Adsorption capacity of water vapor on a honeycomb-type adsorbent is slightly lower than that on a pebble-type adsorbent, while adsorption rate of water vapor on honeycomb-type adsorbent is much higher than that of pebble-type adsorbent.
Pressure adaptive honeycomb: a new adaptive structure for aerospace applications
Vos, R.; Barrett, R.
2010-01-01
A new type of adaptive structure is presented that relies on pressurized honeycomb cells that extent a significant length with respect to the plane of the hexagons. By varying the pressure inside each of the cells, the stiffness can be altered. A variable stiffness in combination with an externally
No crystallization to honeycomb or Kagome in free space
Energy Technology Data Exchange (ETDEWEB)
Grivopoulos, Symeon [Department of Mechanical Engineering, University of California, Santa Barbara, CA 93106-5070 (United States)
2009-03-20
It is intuitive that if an infinite system of particles that interact through an isotropic potential has a crystalline ground state at zero chemical potential, it is of high symmetry. Here, we present an argument why a honeycomb or a Kagome structure cannot be the ground state at zero chemical potential, for a large class of potentials in R{sup 2}.
Honeycombing on CT; its definition, pathologic correlation, and future direction of its diagnosis
Energy Technology Data Exchange (ETDEWEB)
Johkoh, Takeshi, E-mail: johkoht@aol.com [Department of Radiology, Kinki Central Hospital of Mutual Aid Association of Public School Teachers, 3-1 Kurumazuka, Itami, Hyogo, 664-8533 (Japan); Sakai, Fumikazu [Department of Diagnostic Radiology, Saitama International Medical Center, Saitama Medical University, Hidaka (Japan); Noma, Satoshi [Department of Radiology, Tenri Hospital, Tenri (Japan); Akira, Masanori [Department of Radiology, National Hospital Organization Kinki-Chuo Chest Medical Center, Sakai (Japan); Fujimoto, Kiminori [Department of Radiology and Center for Diagnostic Imaging, Kurume University School of Medicine, Kurume (Japan); Watadani, Takeyuki [Department of Radiology, University of Tokyo, Tokyo (Japan); Sugiyama, Yukihiko [Department of Internal Medicine, Jichi Medical University, Shimotsuke (Japan)
2014-01-15
Honeycombing on CT is the clue for the diagnosis of usual interstitial pneumonia (UIP) and its hallmark. According to the ATS-ERS-JRS-ALAT 2010 guideline, the patients with honeycombing on CT can be diagnosed as UIP without surgical biopsy. On CT scans, it is defined as clustered cystic airspaces, typically of comparable diameters of the order of 3–10 mm, which are usually subpleural and have well-defined walls. Pathologically, honeycombing consists of both collapsing of multiple fibrotic alveoli and dilation of alveolar duct and lumen Although the definition of honeycombing seems to be strict, recognition of honeycombing on CT is various among each observer Because typical honeycombing is frequently observed in the patients with UIP, we should judge clustered cysts as honeycombing when a diagnosis of UIP is suspected.
Demonstration of Minimally Machined Honeycomb Silicon Carbide Mirrors
Goodman, William
2012-01-01
Honeycomb silicon carbide composite mirrors are made from a carbon fiber preform that is molded into a honeycomb shape using a rigid mold. The carbon fiber honeycomb is densified by using polymer infiltration pyrolysis, or through a reaction with liquid silicon. A chemical vapor deposit, or chemical vapor composite (CVC), process is used to deposit a polishable silicon or silicon carbide cladding on the honeycomb structure. Alternatively, the cladding may be replaced by a freestanding, replicated CVC SiC facesheet that is bonded to the honeycomb. The resulting carbon fiber-reinforced silicon carbide honeycomb structure is a ceramic matrix composite material with high stiffness and mechanical strength, high thermal conductivity, and low CTE (coefficient of thermal expansion). This innovation enables rapid, inexpensive manufacturing. The web thickness of the new material is less than 1 millimeter, and core geometries tailored. These parameters are based on precursor carbon-carbon honeycomb material made and patented by Ultracor. It is estimated at the time of this reporting that the HoneySiC(Trademark) will have a net production cost on the order of $38,000 per square meter. This includes an Ultracor raw material cost of about $97,000 per square meter, and a Trex silicon carbide deposition cost of $27,000 per square meter. Even at double this price, HoneySiC would beat NASA's goal of $100,000 per square meter. Cost savings are estimated to be 40 to 100 times that of current mirror technologies. The organic, rich prepreg material has a density of 56 kilograms per cubic meter. A charred carbon-carbon panel (volatile organics burnt off) has a density of 270 kilograms per cubic meter. Therefore, it is estimated that a HoneySiC panel would have a density of no more than 900 kilograms per cubic meter, which is about half that of beryllium and about onethird the density of bulk silicon carbide. It is also estimated that larger mirrors could be produced in a matter of weeks
Moseley, Christine
2000-01-01
Presents an environmental science activity designed to enhance students' awareness of the hazards of plastic waste for wildlife in aquatic environments. Discusses how students can take steps to reduce the effects of plastic waste. (WRM)
Electron and phonon properties and gas storage in carbon honeycomb
Gao, Yan; Zhong, Chengyong; Zhang, Zhongwei; Xie, Yuee; Zhang, Shengbai
2016-01-01
A new kind of three-dimensional carbon allotropes, termed carbon honeycomb (CHC), has recently been synthesized [PRL 116, 055501 (2016)]. Based on the experimental results, a family of graphene networks are constructed, and their electronic and phonon properties are calculated by using first principles methods. All networks are porous metal with two types of electron transport channels along the honeycomb axis and they are isolated from each other: one type of channels is originated from the orbital interactions of the carbon zigzag chains and is topologically protected, while the other type of channels is from the straight lines of the carbon atoms that link the zigzag chains and is topologically trivial. The velocity of the electrons can reach ~106 m/s. Phonon transport in these allotropes is strongly anisotropic, and the thermal conductivities can be very low when compared with graphite by at least a factor of 15. Our calculations further indicate that these porous carbon networks possess high storage capa...
Spin-orbital quantum liquid on the honeycomb lattice
Corboz, Philippe
2013-03-01
The symmetric Kugel-Khomskii can be seen as a minimal model describing the interactions between spin and orbital degrees of freedom in transition-metal oxides with orbital degeneracy, and it is equivalent to the SU(4) Heisenberg model of four-color fermionic atoms. We present simulation results for this model on various two-dimensional lattices obtained with infinite projected-entangled pair states (iPEPS), an efficient variational tensor-network ansatz for two dimensional wave functions in the thermodynamic limit. This approach can be seen as a two-dimensional generalization of matrix product states - the underlying ansatz of the density matrix renormalization group method. We find a rich variety of exotic phases: while on the square and checkerboard lattices the ground state exhibits dimer-Néel order and plaquette order, respectively, quantum fluctuations on the honeycomb lattice destroy any order, giving rise to a spin-orbital liquid. Our results are supported from flavor-wave theory and exact diagonalization. Furthermore, the properties of the spin-orbital liquid state on the honeycomb lattice are accurately accounted for by a projected variational wave-function based on the pi-flux state of fermions on the honeycomb lattice at 1/4-filling. In that state, correlations are algebraic because of the presence of a Dirac point at the Fermi level, suggesting that the ground state is an algebraic spin-orbital liquid. This model provides a good starting point to understand the recently discovered spin-orbital liquid behavior of Ba3CuSb2O9. The present results also suggest to choose optical lattices with honeycomb geometry in the search for quantum liquids in ultra-cold four-color fermionic atoms. We acknowledge the financial support from the Swiss National Science Foundation.
Topological quantum error correction in the Kitaev honeycomb model
Lee, Yi-Chan; Brell, Courtney G.; Flammia, Steven T.
2017-08-01
The Kitaev honeycomb model is an approximate topological quantum error correcting code in the same phase as the toric code, but requiring only a 2-body Hamiltonian. As a frustrated spin model, it is well outside the commuting models of topological quantum codes that are typically studied, but its exact solubility makes it more amenable to analysis of effects arising in this noncommutative setting than a generic topologically ordered Hamiltonian. Here we study quantum error correction in the honeycomb model using both analytic and numerical techniques. We first prove explicit exponential bounds on the approximate degeneracy, local indistinguishability, and correctability of the code space. These bounds are tighter than can be achieved using known general properties of topological phases. Our proofs are specialized to the honeycomb model, but some of the methods may nonetheless be of broader interest. Following this, we numerically study noise caused by thermalization processes in the perturbative regime close to the toric code renormalization group fixed point. The appearance of non-topological excitations in this setting has no significant effect on the error correction properties of the honeycomb model in the regimes we study. Although the behavior of this model is found to be qualitatively similar to that of the standard toric code in most regimes, we find numerical evidence of an interesting effect in the low-temperature, finite-size regime where a preferred lattice direction emerges and anyon diffusion is geometrically constrained. We expect this effect to yield an improvement in the scaling of the lifetime with system size as compared to the standard toric code.
Evaluation of thermal shock resistance of cordierite honeycombs
Indian Academy of Sciences (India)
Rathindra Nath Das; C D Madhusoodana; P K Panda; Kiyoshi Okada
2002-04-01
A comparative study on thermal shock resistance (TSR) of extruded cordierite honeycombs is presented. TSR is an important property that predicts the life of these products in thermal environments used for automobile pollution control as catalytic converter or as diesel particulate filter. TSR was experimentally studied by quenching (descending test) the heated samples to water or by heating (ascending test) with an oxyhydrogen flame along with crack detection by acoustic emission (AE) method. TSR was also calculated by using coefficient of themal expasion (CTE), modulus of elasticity (MOE) and modulus of rupture (MOR) of the honeycomb samples. Cordierite honeycombs of 200 and 400 cpsi were used for the above study. It was observed that the trends of TSR were same for both the experimental methods as well as by calculation. The ascending test method showed lower TSR values compared to water quench method due to early detection of cracks by AE. Finite element method (FEM) was also used to evaluate the thermal stress distribution in solid cordierite using thermal shock test data. It was observed that the maximum thermal stress calculated by FEM was lower than the strength of the material; therefore, the solid cordierite did not fail during such tests.
A honeycomb composite of mollusca shell matrix and calcium alginate.
You, Hua-jian; Li, Jin; Zhou, Chan; Liu, Bin; Zhang, Yao-guang
2016-03-01
A honeycomb composite is useful to carry cells for application in bone, cartilage, skin, and soft tissue regenerative therapies. To fabricate a composite, and expand the application of mollusca shells as well as improve preparing methods of calcium alginate in tissue engineering research, Anodonta woodiana shell powder was mixed with sodium alginate at varying mass ratios to obtain a gel mixture. The mixture was frozen and treated with dilute hydrochloric acid to generate a shell matrix/calcium alginate composite. Calcium carbonate served as the control. The composite was transplanted subcutaneously into rats. At 7, 14, 42, and 70 days after transplantation, frozen sections were stained with hematoxylin and eosin, followed by DAPI, β-actin, and collagen type-I immunofluorescence staining, and observed using laser confocal microscopy. The composite featured a honeycomb structure. The control and composite samples displayed significantly different mechanical properties. The water absorption rate of the composite and control group were respectively 205-496% and 417-586%. The composite (mass ratio of 5:5) showed good biological safety over a 70-day period; the subcutaneous structure of the samples was maintained and the degradation rate was lower than that of the control samples. Freezing the gel mixture afforded control over chemical reaction rates. Given these results, the composite is a promising honeycomb scaffold for tissue engineering.
Directory of Open Access Journals (Sweden)
Lei Cao
2015-01-01
Full Text Available Shock absorption characteristics of combined aluminium honeycomb structures were studied experimentally. In the experiments, a testing platform was design to compare the shock absorption level of different honeycomb specimens quantitatively. The shock response curves of six test points mounted on the platform were recorded with acceleration sensors when the buffer was impacted by a bullet driven by high pressure gas. The maximum acceleration values in time domain and in specifically spectral domain were obtained based on spectral analysis. Comparing the data of combined aluminium honeycomb buffer and single aluminium honeycomb buffer, conclusion can be obtained that shock absorbing characteristic of combined aluminium honeycomb buffer is better. Furthermore, compression properties of three kinds of buffers were tested under quasi-static state. The energy absorption parameters were calculated. The results show suitable combined aluminium honeycomb buffer can smooth the stress and lower the energy applied to the testing platform.
Strong and light-weight materials made of reinforced honeycomb sandwich structures
DEFF Research Database (Denmark)
Mikkelsen, Lars Pilgaard; Madsen, Bo
a low cost, in order for them to compete with conventionally used materials like steel or aluminum. A great candidate for a material that can fulfil these requirements of being light, strong and low cost is a sandwich material. A sandwich material is a material that is made of a light-weight core...... with a thin layer of steel or fibre composite on top and bottom of the core. The core in a sandwich material is typically made of a honeycomb structure. Honeycomb structures have been used for more than 50 years. Until now honeycombs have been expensive to produce. However, with a new production method...... it is now possible to produce honeycombs structures at a low cost. In a large collaborative European project called INCOM, the possibility of reinforcing the honeycomb structure is investigated. The honeycomb structure is reinforced with sustainable fibres as the fibres are extracted from saw dust....
Nikhamkin, Mikhail; Sazhenkov, Nikolai; Samodurov, Danil
2017-05-01
Fiber reinforced polymer honeycomb composite sandwich structures are commonly used in different industries. In particular, they are used in the manufacture of gas turbine engines. However, fiber reinforced polymer honeycomb composite sandwich structures often have a manufacturing flaw. In theory, such flaws due to their rapid propagation reduce the durability of fiber reinforced polymer honeycomb composite sandwich structures. In this paper, bending fatigue tests of fiber reinforced polymer honeycomb composite sandwich structures with manufacturing flaws were conducted. Comparative analysis of fatigue fracture of fiber reinforced polymer honeycomb composite sandwich specimens was conducted before and after their bending fatigue tests. The analysis was based on the internal damage X-ray observation of fiber reinforced polymer honeycomb composite sandwich specimens.
Effect of Fatigue Damage on Energy Absorption Properties of Honeycomb Paperboard
Directory of Open Access Journals (Sweden)
Zhi-geng Fan
2015-01-01
Full Text Available The effect of fatigue damage (FD on the energy absorption properties of precompressed honeycomb paperboard is investigated by fatigue compression experiments. The constitutive relations of honeycomb paperboard have been changed after the fatigue damage. The results show that FD has effect on plateau stress and energy absorption capacity of honeycomb paperboard after fatigue cycles but has no significant effect on densification strain. Energy absorption diagram based on the effect of FD is constructed from the stress-strain curves obtained after fatigue compression experiments. FD is a significant consideration for honeycomb paperboard after transports. The results of this paper could be used for optimization design of packaging materials.
Directory of Open Access Journals (Sweden)
Chen Ke
2016-01-01
Full Text Available As the light-weight and high-strength thermoplastic composites, novel honeycomb sandwich panels were discussed in this paper: continuous glass fiber reinforced polypropylene (GF/PP laminated sheets were used as the surface and polypropylene (PP honeycomb was used as the core. The effects of honeycomb core’s height, thickness and aperture on the mechanical properties were analyzed in this paper. The composite honeycomb sandwich panels exhibited excellent bending strength at 37.6MPa and lateral pressure strength at 25.8MPa.
Arunkumar, M. P.; Jagadeesh, M.; Pitchaimani, Jeyaraj; Gangadharan, K. V.; Babu, M. C. Lenin
2016-11-01
This paper presents the results of numerical studies carried out on vibro-acoustic and sound transmission loss behaviour of aluminium honeycomb core sandwich panel with fibre reinforced plastic (FRP) facings. Layered structural shell element with equivalent orthotropic elastic properties of core and orthotropic properties of FRP facing layer is used to predict the free and forced vibration characteristics. Followed by this, acoustic response and transmission loss characteristics are obtained using Rayleigh integral. Vibration and acoustic characteristics of FRP sandwich panels are compared with aluminium sandwich panels. The result reveals that FRP panel has better vibro-acoustic and transmission loss characteristics due to high stiffness and inherent material damping associated with them. Resonant amplitudes of the response are fully controlled by modal damping factors calculated based on modal strain energy. It is also demonstrated that FRP panel can be used to replace the aluminium panel without losing acoustic comfort with nearly 40 percent weight reduction.
Barker, Tommy G.
This curriculum guide is designed to assist junior high schools industrial arts teachers in planning new courses and revising existing courses in plastics technology. Addressed in the individual units of the guide are the following topics: introduction to production technology; history and development of plastics; safety; youth leadership,…
Half-metallicity in 2D organometallic honeycomb frameworks
Sun, Hao; Li, Bin; Zhao, Jin
2016-10-01
Half-metallic materials with a high Curie temperature (T C) have many potential applications in spintronics. Magnetic metal free two-dimensional (2D) half-metallic materials with a honeycomb structure contain graphene-like Dirac bands with π orbitals and show excellent aspects in transport properties. In this article, by investigating a series of 2D organometallic frameworks with a honeycomb structure using first principles calculations, we study the origin of forming half-metallicity in this kind of 2D organometallic framework. Our analysis shows that charge transfer and covalent bonding are two crucial factors in the formation of half-metallicity in organometallic frameworks. (i) Sufficient charge transfer from metal atoms to the molecules is essential to form the magnetic centers. (ii) These magnetic centers need to be connected through covalent bonding, which guarantee the strong ferromagnetic (FM) coupling. As examples, the organometallic frameworks composed by (1,3,5)-benzenetricarbonitrile (TCB) molecules with noble metals (Au, Ag, Cu) show half-metallic properties with T C as high as 325 K. In these organometallic frameworks, the strong electronegative cyano-groups (CN groups) drive the charge transfer from metal atoms to the TCB molecules, forming the local magnetic centers. These magnetic centers experience strong FM coupling through the d-p covalent bonding. We propose that most of the 2D organometallic frameworks composed by molecule—CN—noble metal honeycomb structures contain similar half metallicity. This is verified by replacing TCB molecules with other organic molecules. Although the TCB-noble metal organometallic framework has not yet been synthesized, we believe the development of synthesizing techniques and facility will enable the realization of them. Our study provides new insight into the 2D half-metallic material design for the potential applications in nanotechnology.
Dynamic Buffering Performance of the Honeycomb Paperboard Filled with Polyurethane
Institute of Scientific and Technical Information of China (English)
ZHANG Yong; XIE Weihong; CHEN Li
2014-01-01
A new kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, we analyzed the mechanical behaviors of the material under different conditions and obtained the inherent influencing laws of some factors on the material’s dynamic buffering performance. It was shown that the dynamic buffering performance varied directly with impact velocity, and inversely with the void diameter, thickness and buffering area of the composite material.
Electron and phonon properties and gas storage in carbon honeycombs
Gao, Yan; Chen, Yuanping; Zhong, Chengyong; Zhang, Zhongwei; Xie, Yuee; Zhang, Shengbai
2016-06-01
A new kind of three-dimensional carbon allotrope, termed carbon honeycomb (CHC), has recently been synthesized [PRL 116, 055501 (2016)]. Based on the experimental results, a family of graphene networks has been constructed, and their electronic and phonon properties are studied by various theoretical approaches. All networks are porous metals with two types of electron transport channels along the honeycomb axis and they are isolated from each other: one type of channel originates from the orbital interactions of the carbon zigzag chains and is topologically protected, while the other type of channel is from the straight lines of the carbon atoms that link the zigzag chains and is topologically trivial. The velocity of the electrons can reach ~106 m s-1. Phonon transport in these allotropes is strongly anisotropic, and the thermal conductivities can be very low when compared with graphite by at least a factor of 15. Our calculations further indicate that these porous carbon networks possess high storage capacity for gaseous atoms and molecules in agreement with the experiments.A new kind of three-dimensional carbon allotrope, termed carbon honeycomb (CHC), has recently been synthesized [PRL 116, 055501 (2016)]. Based on the experimental results, a family of graphene networks has been constructed, and their electronic and phonon properties are studied by various theoretical approaches. All networks are porous metals with two types of electron transport channels along the honeycomb axis and they are isolated from each other: one type of channel originates from the orbital interactions of the carbon zigzag chains and is topologically protected, while the other type of channel is from the straight lines of the carbon atoms that link the zigzag chains and is topologically trivial. The velocity of the electrons can reach ~106 m s-1. Phonon transport in these allotropes is strongly anisotropic, and the thermal conductivities can be very low when compared with graphite by
[Catalytic ozonation by ceramic honeycomb for the degradation of oxalic acid in aqueous solution].
Zhao, Lei; Sun, Zhi-Zhong; Ma, Jun
2007-11-01
Comparative experiments for the degradation of oxalic acid in aqueous solution were carried out in the three processes of ozonation alone, ceramic honeycomb-catalyzed ozonation and ceramic honeycomb adsorption. The results show that the degradation rates of oxalic acid in the ceramic honeycomb-catalyzed ozonation, ozonation alone and ceramic honeycomb adsorption systems are 37.6%, 2.2% and 0.4%, and the presence of ceramic honeycomb catalyst significantly improves the degradation rate of oxalic acid compared to the results from non-catalytic ozonation and adsorption. With the addition of tert-butanol, the degradation rates of oxalic acid in catalytic ozonation system decrease by 24.1%, 29.0% and 30.1%, respectively, at the concentration of 5, 10 and 15 mg x L(-1). This phenomenon indicates that ceramic honeycomb-catalyzed ozonation for the degradation of oxalic acid in aqueous solution follows the mechanism of *OH oxidation, namely the heterogeneous surface of catalyst enhances the initiation of *OH. The results of TOC analysis demonstrate that the process of ceramic honeycomb-catalyzed ozonation can achieve the complete mineralization level without the formation of intermediary degradation products. The experimental results suggest that the reaction temperature has positive relationship with the degradation rate of oxalic acid. The degradation rates of oxalic acid in the ceramic honeycomb-catalyzed ozonation system are 16.4%, 37.6%, 61.3% and 68.2%, at the respective reaction temperature of 10, 20, 30 and 40 degrees C.
[Degradation of nitrobenzene in aqueous solution by modified ceramic honeycomb-catalyzed ozonation].
Sun, Zhi-Zhong; Zhao, Lei; Ma, Jun
2005-11-01
Comparative experiments of modified ceramic honeycomb, ceramic honeycomb-catalyzed ozonation and ozonation alone were conducted with nitrobenzene as the model organic pollutant. It was found that the processes of modified ceramic honeycomb and ceramic honeycomb-catalyzed ozonation could increase the removal efficiency of nitrobenzene by 38.35% and 15.46%, respectively, compared with that achieved by ozonation alone. Under the conditions of this experiment, the degradation rate of modified ceramic honeycomb-catalyzed ozonation increased by 30.55% with the increase of amount of catalyst to 5 blocks. The degradation rate of three process all increased greatly with the increase of temperature and value of pH in the solution. But when raising the pH value of the solution to 10.00, the advantage of modified ceramic honeycomb-catalyzed ozonation processes lost. The experimental results indicate that in modified ceramic honeycomb-catalyzed ozonation, nitrobenzene is primarily oxidized by *OH free radical in aqueous solution. The adsorption of nitrobenzene is too limited to have any influence on the degradation efficiency of nitrobenzene. With the same total dosage of applied ozone, the multiple steps addition of ozone showed a much higher removal efficiency than that obtained by one step in three processes. Modified ceramic honeycomb had a relative longer lifetime.
Energy absorption of andwiched honeycombs with facesheets under in-plane crushing
Atli-Veltin, B.; Gandhi, F.
2013-01-01
The in-plane crushing and energy absorption of sandwiched honeycomb cores with facesheets are examined through finite element simulations. Assuming no debonding between the facesheet and honeycomb core (which would be the case if manufacturing techniques such as brazing are used to produce very stro
Fabrication and characterization of porous-core honeycomb bandgap THz fibers
DEFF Research Database (Denmark)
Bao, Hualong; Nielsen, Kristian; Rasmussen, Henrik K.
2012-01-01
We present a numerical and experimental investigation of a low-loss porous-core honeycomb fiber for terahertz wave guiding. The introduction of a porous core with hole size of the same dimension as the holes in the surrounding honeycomb cladding results in a fiber that can be drawn with much higher...
He, Chenglin; Chen, Jinxiang; Wu, Zhishen; Xie, Juan; Zu, Qiao; Lu, Yun
2015-05-01
Honeycomb plates can be applied in many fields, including furniture manufacturing, mechanical engineering, civil engineering, transportation and aerospace. In the present study, we discuss the simulated effect on the mechanical properties of bionic integrated honeycomb plates by investigating the compressive and shear failure modes and the mechanical properties of trabeculae reinforced by long or short fibers. The results indicate that the simulated effect represents approximately 80% and 70% of the compressive and shear strengths, respectively. Compared with existing bionic samples, the mass-specific strength was significantly improved. Therefore, this integrated honeycomb technology remains the most effective method for the trial manufacturing of bionic integrated honeycomb plates. The simulated effect of the compressive rigidity is approximately 85%. The short-fiber trabeculae have an advantage over the long-fiber trabeculae in terms of shear rigidity, which provides new evidence for the application of integrated bionic honeycomb plates.
Phase diagram of interacting spinless fermions on the honeycomb lattice
Capponi, Sylvain
2017-02-01
Fermions hopping on a hexagonal lattice represent one of the most active research fields in condensed matter since the discovery of graphene in 2004 and its numerous applications. Another exciting aspect of the interplay between geometry and quantum mechanical effects is given by the Haldane model (Haldane 1988 Phys. Rev. Lett. 61 2015), where spinless fermions experiencing a certain flux pattern on the honeycomb lattice leads to the stabilization of a topological phase of matter, distinct from a Mott insulator and nowadays dubbed Chern insulator. In this context, it is crucial to understand the role of interactions and this review will describe recent results that have been obtained for a minimal model, namely spinless fermions with nearest and next-nearest neighbour density-density interactions on the honeycomb lattice at half-filling. Topics addressed include an introduction of the minimal model and a discussion of the possible instabilities of the Dirac semimetal, a presentation of various theoretical and numerical approaches, and a summary of the results with a particular emphasis on the stability or not of some exotic quantum phases such as charge ordered ones (similar to Wigner crystals) and spontaneous Chern insulator phases.
Kitaev honeycomb tensor networks: exact unitary circuits and applications
Schmoll, Philipp
2016-01-01
The Kitaev honeycomb model is a paradigm of exactly-solvable models, showing non-trivial physical properties such as topological quantum order, abelian and non-abelian anyons, and chirality. Its solution is one of the most beautiful examples of the interplay of different mathematical techniques in condensed matter physics. In this paper, we show how to derive a tensor network (TN) description of the eigenstates of this spin-1/2 model in the thermodynamic limit, and in particular for its ground state. In our setting, eigenstates are naturally encoded by an exact 3d TN structure made of fermionic unitary operators, corresponding to the unitary quantum circuit building up the many-body quantum state. In our derivation we review how the different "solution ingredients" of the Kitaev honeycomb model can be accounted for in the TN language, namely: Jordan-Wigner transformation, braidings of Majorana modes, fermionic Fourier transformation, and Bogoliubov transformation. The TN built in this way allows for a clear u...
Edge magnetism of Heisenberg model on honeycomb lattice.
Huang, Wen-Min; Hikihara, Toshiya; Lee, Yen-Chen; Lin, Hsiu-Hau
2017-03-07
Edge magnetism in graphene sparks intense theoretical and experimental interests. In the previous study, we demonstrated the existence of collective excitations at the zigzag edge of the honeycomb lattice with long-ranged Néel order. By employing the Schwinger-boson approach, we show that the edge magnons remain robust even when the long-ranged order is destroyed by spin fluctuations. Furthermore, in the effective field-theory limit, the dynamics of the edge magnon is captured by the one-dimensional relativistic Klein-Gordon equation. It is intriguing that the boundary field theory for the edge magnon is tied up with its bulk counterpart. By performing density-matrix renormalization group calculations, we show that the robustness may be attributed to the closeness between the ground state and the Néel state. The existence of edge magnon is not limited to the honeycomb structure, as demonstrated in the rotated-square lattice with zigzag edges as well. The universal behavior indicates that the edge magnons may attribute to the uncompensated edges and can be detected in many two-dimensional materials.
Spatial confinement of ferromagnetic resonances in honeycomb antidot lattices
Energy Technology Data Exchange (ETDEWEB)
Krivoruchko, V.N., E-mail: krivoruc@gmail.com [Donetsk Physics and Technology Institute NAS of Ukraine, 72 R. Luxemburg Str., 83114 Donetsk (Ukraine); Marchenko, A.I., E-mail: marchalexx@gmail.com [Donetsk Physics and Technology Institute NAS of Ukraine, 72 R. Luxemburg Str., 83114 Donetsk (Ukraine)
2012-09-15
We report on a theoretical investigation of the magnetic static and dynamic properties of a thin ferromagnetic film with honeycomb lattice of circular antidots using micromagnetic simulations and analytical calculations. The theoretical model is based on the Landau-Lifshitz equations and directly accounts for the effects of the magnetic state nonuniformity. A direct calculation of local dynamic susceptibility tensor yields that the resonance spectra consist of four different quasi-uniform modes of the magnetization precession related to the confinement of magnetic domains by the hole mesh. Three of four resonant modes follow a two-fold variation with respect to the in-plane orientation of the applied magnetic field. The easy axes of these modes are mutually rotated by 60 Degree-Sign and combine to yield the apparent six-fold configurational anisotropy. Additionally, a mode with intrinsic six-fold symmetry behavior exists, as well. Micromagnetic calculations of the local dynamic susceptibility tensor allow identifying the magnetic unit cell areas/domains responsible for each resonance mode. - Highlights: Black-Right-Pointing-Pointer We study the magnetic static and dynamic properties of honeycomb antidot lattices. Black-Right-Pointing-Pointer Micromagnetic simulation and analytical calculation were used. Black-Right-Pointing-Pointer Four quasi-uniform precession modes exist in resonance spectra. Black-Right-Pointing-Pointer The antidot unit cell areas responsible for each resonance mode were identified.
Material Model Evaluation of a Composite Honeycomb Energy Absorber
Jackson, Karen E.; Annett, Martin S.; Fasanella, Edwin L.; Polanco, Michael A.
2012-01-01
A study was conducted to evaluate four different material models in predicting the dynamic crushing response of solid-element-based models of a composite honeycomb energy absorber, designated the Deployable Energy Absorber (DEA). Dynamic crush tests of three DEA components were simulated using the nonlinear, explicit transient dynamic code, LS-DYNA . In addition, a full-scale crash test of an MD-500 helicopter, retrofitted with DEA blocks, was simulated. The four material models used to represent the DEA included: *MAT_CRUSHABLE_FOAM (Mat 63), *MAT_HONEYCOMB (Mat 26), *MAT_SIMPLIFIED_RUBBER/FOAM (Mat 181), and *MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM (Mat 142). Test-analysis calibration metrics included simple percentage error comparisons of initial peak acceleration, sustained crush stress, and peak compaction acceleration of the DEA components. In addition, the Roadside Safety Verification and Validation Program (RSVVP) was used to assess similarities and differences between the experimental and analytical curves for the full-scale crash test.
Experimental study of aluminium honeycomb behaviour under dynamic multiaxial loading
Directory of Open Access Journals (Sweden)
Markiewicz E.
2012-08-01
Full Text Available Split Hopkinson Pressure Bar system (SHPB with large-diameter and Nylon bars introducing a shear-compression loading device is used in order to investigate the dynamic behaviour of aluminium honeycomb under multiaxial loadings conditions. All shear-compression configurations including the loading angle variation from 0∘ to 60∘ are performed with an impact velocity of about 15m/s. The adapted SHPB system with the device are validated numerically and a phenomenon of separation between the input bar and the input beveled bar is observed. Numerical results suggest that this phenomenon provides a cutting of the reflected wave. An electro optical extensometer is employed in experiments. A good agreement between the numerical elastic waves and the experimental ones is obtained. Experimental results show a significant effect of the loading angle on the apparent stress-strain curves. The initial peak value and the plateau stress decrease with the increase of the loading angle. The combined shear-compression device with an enhancement at the alignment set-up provides efficient results for samples dynamically loaded. This device will be used to investigate the influence of the in-plane orientation angle on the deformation mechanisms and multiaxial behaviour of aluminium honeycomb under dynamic and quasi-static loading conditions.
Triangular and honeycomb lattices of cold atoms in optical cavities
Safaei, Shabnam; Miniatura, Christian; Grémaud, BenoÃ®t.
2015-10-01
We consider a two-dimensional homogeneous ensemble of cold bosonic atoms loaded inside two optical cavities and pumped by a far-detuned external laser field. We examine the conditions for these atoms to self-organize into triangular and honeycomb lattices as a result of superradiance. By collectively scattering the pump photons, the atoms feed the initially empty cavity modes. As a result, the superposition of the pump and cavity fields creates a space-periodic light-shift external potential and atoms self-organize into the potential wells of this optical lattice. Depending on the phase of the cavity fields with respect to the pump laser, these minima can either form a triangular or a hexagonal lattice. By numerically solving the dynamical equations of the coupled atom-cavity system, we have shown that the two stable atomic structures at long times are the triangular lattice and the honeycomb lattice with equally populated sites. We have also studied how to drive atoms from one lattice structure to another by dynamically changing the phase of the cavity fields with respect to the pump laser.
National Research Council Canada - National Science Library
Singhi, Anil Kumar; Vinoth, Bharathi; Kuruvilla, Sarah; Sivakumar, Kothandam
2015-01-01
Plastic bronchitis, a rare but serious clinical condition, commonly seen after Fontan surgeries in children, may be a manifestation of suboptimal adaptation to the cavopulmonary circulation with unfavorable hemodynamics...
Trettnak, Wolfgang
2015-01-01
In terms of weight, the plastic pollution in the world’s oceans is estimated to be around 300,000 tonnes. This plastic comes from both land-based and ocean-based sources. A lecture at CERN by chemist Wolfgang Trettnak addressed this issue and highlighted the role of art in raising people’s awareness. The slideshow below gives you a taste of the artworks by Wolfgang Trettnak and Margarita Cimadevila.
Institute of Scientific and Technical Information of China (English)
履之
1994-01-01
Already ubiquitous in homes and cars, plastic is now appearing inbridges. An academic-industrial consortium based at the University ofCalifornia in San Diego is launching a three-year research program aimed atdeveloping the world’s first plastic highway bridge, a 450-foot span madeentirely from glass-,carbon,and polymer-fiber-reinforced composite mate-rials, the stuff of military aircraft. It will cross Interstate 5 to connect thetwo sides of the school’s campus.
Institute of Scientific and Technical Information of China (English)
魏生贤; 胡粉娥; 晏翠琼
2016-01-01
thermal performance of the flat-plate type solar energy water heater has been studied globally. In order to ensure the efficient operation of the solar water heater and user's demand to the terminal temperature of a tank, the countries all over the world with different climate have given different recommended value for water-mass-to-collector-area ratio (the ratio is abbreviated as MAR) of the flat-plate solar water heater. However, China has a vast territory and its climate is complex. The value range of recommended value from literatures is too large to be used to practical application. The main residential buildings in large and medium-sized cities are mostly high-rise buildings. The solar water heater installed on roof can only meet hot water use for the top six to eight floors. The application of the balcony wall-mounted solar water heater is one of the effective ways to solve hot water needs for the rest of users in high-rise buildings. Based on the typical meteorological data of nine cities in mild region of China, the values of MAR of the balcony wall-mounted flat-plate solar water heater have been calculated by using the established mathematical model. The water tank terminal temperature of 60℃, the collector angle of 60°-90° and the azimuth angle of 0-90° were used in model analysis. Calculation results for south-facing balcony wall-mounted solar water heater in mild region showed that the appropriate MAR of spring, summer, autumn, winter and the whole year was 28-51, 21-41, 31-53, 37-57 and 31-47 kg/m2, respectively. For convenience of practical application, the linear regression relation between seasonal and annual average MAR and the tilt angle for south-facing balcony wall-mounted solar water heater. The correlation coefficients between them were greater than 0.99. In this paper, we introduced a new concept “azimuth factor of MAR” which was easy to calculate MAR for the collector with different azimuth angle. For the non-south-facing balcony wall
Guarded Flat Plate Cryogenic Test Apparatus and Calorimeter
Fesmire, James E. (Inventor); Johnson, Wesley L. (Inventor)
2017-01-01
A test apparatus for thermal energy measurement of disk-shaped test specimens has a cold mass assembly locatable within a sealable chamber with a guard vessel having a guard chamber to receive a liquid fluid and a bottom surface to contact a cold side of a test specimen, and a test vessel having a test chamber to receive a liquid fluid and encompassed on one side by a center portion of the bottom surface shared with the guard vessel. A lateral wall assembly of the test vessel is closed by a vessel top, the lateral wall assembly comprising an outer wall and an inner wall having opposing surfaces that define a thermal break including a condensable vapor pocket to inhibit heat transfer through the lateral wall from the guard vessel to the test vessel. A warm boundary temperature surface is in thermal communication with a lower surface of the test specimen.
Numerical study of viscous starting flow past a flat plate
Xu, Ling
2014-01-01
Viscous flow past a finite plate which is impulsively started in direction normal to itself is studied numerically using a high order mixed finite difference and semi-Lagrangian scheme. The goal is to resolve details of the vorticity generation at early times, and to determine the effect of viscosity on flow quantities such as the core trajectory and vorticity, and the shed circulation. Vorticity contours, streaklines and streamlines are presented for a range of Reynolds numbers $Re \\in [250, 2000]$ and a range of times $t \\in[0. 0002, 5]$. At early times, most of the vorticity is attached to the plate. The paper proposes a definition for the shed circulation at early as well as late times, and shows that it indeed represents vorticity that separates from the plate without reattaching. The contribution of viscous diffusion to the circulation shedding rate is found to be significant, but, interestingly, to depend only slightly on the value of the Reynolds number. The shed circulation and the vortex core trajec...
Flat plate solar air heater with latent heat storage
Touati, B.; Kerroumi, N.; Virgone, J.
2017-02-01
Our work contains two parts, first is an experimental study of the solar air heater with a simple flow and forced convection, we can use thatlaste oneit in many engineering's sectors as solardrying, space heating in particular. The second part is a numerical study with ansys fluent 15 of the storage of part of this solar thermal energy produced,using latent heat by using phase change materials (PCM). In the experimental parts, we realize and tested our solar air heater in URER.MS ADRAR, locate in southwest Algeria. Where we measured the solarradiation, ambient temperature, air flow, thetemperature of the absorber, glasses and the outlet temperature of the solar air heater from the Sunrise to the sunset. In the second part, we added a PCM at outlet part of the solar air heater. This PCM store a part of the energy produced in the day to be used in peak period at evening by using the latent heat where the PCMs present a grateful storagesystem.A numerical study of the fusion or also named the charging of the PCM using ANSYS Fluent 15, this code use the method of enthalpies to solve the fusion and solidification formulations. Furthermore, to improve the conjugate heat transfer between the heat transfer fluid (Air heated in solar plate air heater) and the PCM, we simulate the effect of adding fins to our geometry. Also, four user define are write in C code to describe the thermophysicalpropriety of the PCM, and the inlet temperature of our geometry which is the temperature at the outflow of the solar heater.
Improvement of flat plate collectors for solar energy conversion
Boeck, H.; Hallermayer, R.; Schoelkopf, W.; Sizman, R.
1984-03-01
Selective absorption for thermal conversion of radiative energy was investigated. Improvement and operation of various measuring devices for absorption and emission are presented. Selective coatings were produced by vapor deposition and galvanic treatment. Calculations of the transmittance of turbular collector fields are presented. Operational Characteristics of Collector were examined. A collector test field with simultaneous recording of data from 24 collectors or uncovered absorbers was built and connected to a high performance microprocessor system. The transient behavior of collectors by variation of the irradiation and the collector inlet temperature were investigated. A mechanism for stratification of hot water of fluctuating inlet temperature in a storage tank was studied. The operating conditions of a heat pump installed in the collector test plant are investigated. A large domestic hot water system is equipped with temperature sensors and flowmeters for computer recording.
GREEN PLASTIC: A NEW PLASTIC FOR PACKAGING
Mr. Pankaj Kumar*, Sonia
2016-01-01
This paper gives a brief idea about a new type of plastic called as bio-plastic or green plastic. Plastic is used as a packaging material for various products, but this plastic is made up of non renewable raw materials. There are various disadvantages of using conventional plastic like littering, CO2 production, non-degradable in nature etc. To overcome these problems a new type of plastic is discovered called bio-plastic or green plastic. Bio-plastic is made from renewable resources and also...
Elastic-Plastic J-Integral Solutions or Surface Cracks in Tension Using an Interpolation Methodology
Allen, P. A.; Wells, D. N.
2013-01-01
No closed form solutions exist for the elastic-plastic J-integral for surface cracks due to the nonlinear, three-dimensional nature of the problem. Traditionally, each surface crack must be analyzed with a unique and time-consuming nonlinear finite element analysis. To overcome this shortcoming, the authors have developed and analyzed an array of 600 3D nonlinear finite element models for surface cracks in flat plates under tension loading. The solution space covers a wide range of crack shapes and depths (shape: 0.2 less than or equal to a/c less than or equal to 1, depth: 0.2 less than or equal to a/B less than or equal to 0.8) and material flow properties (elastic modulus-to-yield ratio: 100 less than or equal to E/ys less than or equal to 1,000, and hardening: 3 less than or equal to n less than or equal to 20). The authors have developed a methodology for interpolating between the goemetric and material property variables that allows the user to reliably evaluate the full elastic-plastic J-integral and force versus crack mouth opening displacement solution; thus, a solution can be obtained very rapidly by users without elastic-plastic fracture mechanics modeling experience. Complete solutions for the 600 models and 25 additional benchmark models are provided in tabular format.
Directed self-assembly of large scaffold-free multi-cellular honeycomb structures
Energy Technology Data Exchange (ETDEWEB)
Tejavibulya, Nalin; Youssef, Jacquelyn; Bao, Brian; Ferruccio, Toni-Marie; Morgan, Jeffrey R, E-mail: Jeffrey_Morgan@Brown.edu [Department of Molecular Pharmacology, Physiology and Biotechnology, Center for Biomedical Engineering, Brown University, G-B 393, Biomed Center, 171 Meeting St, Providence, RI 02912 (United States)
2011-09-15
A significant challenge to the field of biofabrication is the rapid construction of large three-dimensional (3D) living tissues and organs. Multi-cellular spheroids have been used as building blocks. In this paper, we create large multi-cellular honeycomb building blocks using directed self-assembly, whereby cell-to-cell adhesion, in the context of the shape and obstacles of a micro-mold, drives the formation of a 3D structure. Computer-aided design, rapid prototyping and replica molding were used to fabricate honeycomb-shaped micro-molds. Nonadhesive hydrogels cast from these micro-molds were equilibrated in the cell culture medium and seeded with two types of mammalian cells. The cells settled into the honeycomb recess were unable to attach to the nonadhesive hydrogel and so cell-to-cell adhesion drove the self-assembly of a large multi-cellular honeycomb within 24 h. Distinct morphological changes occurred to the honeycomb and its cells indicating the presence of significant cell-mediated tension. Unlike the spheroid, whose size is constrained by a critical diffusion distance needed to maintain cell viability, the overall size of the honeycomb is not limited. The rapid production of the honeycomb building unit, with its multiple rings of high-density cells and open lumen spaces, offers interesting new possibilities for biofabrication strategies.
Embedding of Poly Honeycomb Networks and the Metric dimension of Star of David Network
Directory of Open Access Journals (Sweden)
F.Simonraj
2013-01-01
Full Text Available In this paper, we have introduced few Interconnection Networks, called David Derived Network DD(n ,Dominating David Derived Network DDD(n, Honeycomb cup Network HCC(n and Kite RegularTrianguline Mesh KRrTM(n. We have given drawing algorithm for DDD(n from Honeycomb networkHC(n and embedded poly–Honeycomb Networks, KRrTM(n in to Dominating David Derived Networks.Also we have investigated the metric dimension of Star of David network SD(n and lower bound of themetric dimension for DD(n.
Modulation of the photonic band structure topology of a honeycomb lattice in an atomic vapor
Zhang, Yiqi; Belić, Milivoj R; Wu, Zhenkun; Zhang, Yanpeng
2015-01-01
In an atomic vapor, a honeycomb lattice can be constructed by utilizing the three-beam interference method. In the method, the interference of the three beams splits the dressed energy level periodically, forming a periodic refractive index modulation with the honeycomb profile. The energy band topology of the honeycomb lattice can be modulated by frequency detunings, thereby affecting the appearance (and disappearance) of Dirac points and cones in the momentum space. This effect can be usefully exploited for the generation and manipulation of topological insulators.
1968-01-01
Only simple equipment, simple technology and low initial capital investment are needed in their manufacture. The condoms can be made by people who were previously unskilled or only semi-skilled workers. Plastic condoms differ from those made of latex rubber in that the nature of the plastic film allows unlimited shelf-life. Also, the plastic has a higher degree of lubricity than latex rubber; if there is a demand for extra lubrication in a particular market, this can be provided. Because the plastic is inert, these condoms need not be packaged in hermetically sealed containers. All these attributes make it possible to put these condoms on the distributors' shelves in developing countries competitively with rubber condoms. The shape of the plastic condom is based on that of the lamb caecum, which has long been used as luxury-type condom. The plastic condom is made from plastic film (ethylene ethyl acrilate) of 0.001 inch (0.0254 mm.) thickness. In addition, a rubber ring is provided and sealed into the base of the condom for retention during coitus. The advantage of the plastic condom design and the equipment on which it is made is that production can be carried out either in labour-intensive economy or with varying degrees of mechanization and automation. The uniform, finished condom if made using previously untrained workers. Training of workers can be done in a matter of hours on the two machines which are needed to produce and test the condoms. The plastic film is provided on a double wound roll, and condom blanks are prepared by means of a heat-sealing die on the stamping machine. The rubber rings are united to the condom blanks on an assembly machine, which consists of a mandrel and heat-sealing equipment to seal the rubber ring to the base of the condom. Built into the assembly machine is a simple air-testing apparatus that can detect the smallest pinhole flaw in a condom. The manufacturing process is completed by unravelling the condom from the assembly
Classical Spin Liquid on the Maximally Frustrated Honeycomb Lattice
Rehn, J.; Sen, Arnab; Damle, Kedar; Moessner, R.
2016-10-01
We show that the honeycomb Heisenberg antiferromagnet with J1/2 =J2=J3, where J1 , J2 , and J3 are first-, second-, and third-neighbor couplings, respectively, forms a classical spin liquid with pinch-point singularities in the structure factor at the Brillouin zone corners. Upon dilution with nonmagnetic ions, fractionalized degrees of freedom carrying 1 /3 of the free moment emerge. Their effective description in the limit of low temperature is that of spins randomly located on a triangular lattice, with a frustrated sublattice-sensitive interaction of long-ranged logarithmic form. The X Y version of this magnet exhibits nematic thermal order by disorder. This comes with a clear experimental diagnostic in neutron scattering, which turns out to apply also to the case of the celebrated planar order by disorder of the kagome Heisenberg antiferromagnet.
Topological features of engineered arrays of adsorbates in honeycomb lattices
Energy Technology Data Exchange (ETDEWEB)
Gonzalez-Arraga, Luis A., E-mail: ludovici83@gmail.com [IMDEA Nanociencia, Calle de Faraday, 9, Cantoblanco, 28049 Madrid (Spain); Lado, J.L. [International Iberian Nanotechnology Laboratory (INL), Av. Mestre Jose Veiga, 4715-330 Braga (Portugal); Guinea, Francisco [IMDEA Nanociencia, Calle de Faraday, 9, Cantoblanco, 28049 Madrid (Spain); School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)
2016-09-01
Hydrogen adatoms are one of the most the promising proposals for the functionalization of graphene. The adatoms induce narrow resonances near the Dirac energy, which lead to the formation of magnetic moments. Furthermore, they also create local lattice distortions which enhance the spin–orbit coupling. The combination of magnetism and spin–orbit coupling allows for a rich variety of phases, some of which have non-trivial topological features. We analyze the interplay between magnetism and spin–orbit coupling in ordered arrays of adsorbates on honeycomb lattice monolayers, and classify the different phases that may arise. We extend our model to consider arrays of adsorbates in graphene-like crystals with stronger intrinsic spin–orbit couplings. We also consider a regime away from half-filling in which the Fermi level is at the bottom of the conduction band, we find a Berry curvature distribution corresponding to a Valley–Hall effect.
Orbital edge states in a photonic honeycomb lattice
Milićević, Marijana; Montambaux, Gilles; Carusotto, Iacopo; Galopin, Elisabeth; Lemaître, Aristide; Gratiet, Luc Le; Sagnes, Isabelle; Bloch, Jacqueline; Amo, Alberto
2016-01-01
We experimentally reveal the emergence of edge states in a photonic lattice with orbital bands. We use a two-dimensional honeycomb lattice of coupled micropillars whose bulk spectrum shows four gapless bands arising from the coupling of $p$-like photonic orbitals. We observe zero-energy edge states whose topological origin is similar to that of conventional edge states in graphene. Additionally, we report novel dispersive edge states that emerge not only in zigzag and bearded terminations, but also in armchair edges. The observations are reproduced by tight-binding and analytical calculations. Our work shows the potentiality of coupled micropillars in elucidating some of the electronic properties of emergent 2D materials with orbital bands.
Position space formulation for Dirac fermions on honeycomb lattice
Hirotsu, Masaki; Shintani, Eigo
2014-01-01
We study how to construct Dirac fermion defined on the honeycomb lattice in position space. Starting from the nearest neighbor interaction in tight binding model, we show that the Hamiltonian is constructed by kinetic term and second derivative term of three flavor Dirac fermions in which one flavor has a mass of cutoff order and the other flavors are massless. In this formulation the structure of the Dirac point is simplified so that its uniqueness can be easily shown even if we consider the next-nearest neighbor interaction. We also explicitly show that there exists an exact chiral symmetry at finite lattice spacing, which protects the masslessness of the Dirac fermion, and discuss the analogy with the staggered fermion formulation.
Perturbation Solutions for Thermal Process of Honeycomb Regenerator
Institute of Scientific and Technical Information of China (English)
AI Yuan-fang; MEI Chi; HUANG Guo-dong; JIANG Shao-jian
2007-01-01
A parameter perturbation for the unsteady-state heat-transfer characteristics of honeycomb regenerator is presented. It is limited to the cases where the storage matrix has a small wall thickness so that no temperature variation in the matrix perpendicular to the flow direction is considered. Starting from a two-phase transient thermal model for the gas and storage matrix, an approximate solution for regenerator heat transfer process is derived using the multiple-scale method for the limiting case where the longitudinal heat conduction of solid matrix is far less than the convective heat transfer between the gas and the solid. The regenerator temperature profiles are expressed as Taylor series of the coefficient of solid heat conduction item in the model. The analytical validity is shown by comparing the perturbation solution with the experiment and the numerical solution. The results show that it is possible for the perturbation to improve the effectiveness and economics of thermal research on regenerators.
Research on temperature profiles of honeycomb regenerator with asymptotic analysis
Institute of Scientific and Technical Information of China (English)
AI Yuan-fang; MEI Chi; HUANG Guo-dong; JIANG Shao-jian; CHEN Hong-rong
2006-01-01
An asymptotic semi-analytical method for heat transfer in counter-flow honeycomb regenerator is proposed. By introducing a combined heat-transfer coefficient between the gas and solid phase, a heat transfer model is built based on the thin-walled assumption. The dimensionless thermal equation is deduced by considering solid heat conduction along the passage length. The asymptotic analysis is used for the small parameter of heat conduction term in equation. The first order asymptotic solution to temperature distribution under weak solid heat conduction is achieved after Laplace transformation through the multiple scales method and the symbolic manipulation function in MATLAB. Semi-analytical solutions agree with tests and finite-difference numerical results. It is proved possible for the asymptotic analysis to improve the effectiveness, economics and precision of thermal research on regenerator.
Orbital Edge States in a Photonic Honeycomb Lattice
Milićević, M.; Ozawa, T.; Montambaux, G.; Carusotto, I.; Galopin, E.; Lemaître, A.; Le Gratiet, L.; Sagnes, I.; Bloch, J.; Amo, A.
2017-03-01
We experimentally reveal the emergence of edge states in a photonic lattice with orbital bands. We use a two-dimensional honeycomb lattice of coupled micropillars whose bulk spectrum shows four gapless bands arising from the coupling of p -like photonic orbitals. We observe zero-energy edge states whose topological origin is similar to that of conventional edge states in graphene. Additionally, we report novel dispersive edge states in zigzag and armchair edges. The observations are reproduced by tight-binding and analytical calculations, which we extend to bearded edges. Our work shows the potentiality of coupled micropillars in elucidating some of the electronic properties of emergent two-dimensional materials with orbital bands.
Two Dimensional Honeycomb Materials: Random Fields, Dissipation and Fluctuations
Frederico, T.; Oliveira, O.; de Paula, W.; Hussein, M. S.; Cardoso, T. R.
2017-02-01
In this paper, we propose a method to describe the many-body problem of electrons in honeycomb materials via the introduction of random fields which are coupled to the electrons and have a Gaussian distribution. From a one-body approach to the problem, after integrating exactly the contribution of the random fields, one builds a non-hermitian and dissipative effective Hamiltonian with two-body interactions. Our approach introduces besides the usual average over the electron field a second average over the random fields. The interplay of two averages enables the definition of various types of Green's functions which allow the investigation of fluctuation-dissipation characteristics of the interactions that are a manifestation of the many-body problem. In the current work, we study only the dissipative term, through the perturbative analysis of the dynamics associated the effective Hamiltonian generated by two different kinds of couplings. For the cases analyzed, the eigenstates of the effective Hamiltonian are complex and, therefore, some of the states have a finite life time. Moreover, we also investigate, in the mean field approximation, the most general parity conserving coupling to the random fields and compute the width of charge carriers Γ as a function of the Fermi energy E F . The theoretical prediction for Γ( E F ) is compared to the available experimental data for graphene. The good agreement between Γ t h e o and Γ e x p suggests that description of the many-body problem associated to the electrons in honeycomb materials can indeed be done via the introduction of random fields.
Kitaev honeycomb tensor networks: Exact unitary circuits and applications
Schmoll, Philipp; Orús, Román
2017-01-01
The Kitaev honeycomb model is a paradigm of exactly solvable models, showing nontrivial physical properties such as topological quantum order, Abelian and non-Abelian anyons, and chirality. Its solution is one of the most beautiful examples of the interplay of different mathematical techniques in condensed matter physics. In this paper, we show how to derive a tensor network (TN) description of the eigenstates of this spin-1/2 model in the thermodynamic limit, and in particular for its ground state. In our setting, eigenstates are naturally encoded by an exact 3d TN structure made of fermionic unitary operators, corresponding to the unitary quantum circuit building up the many-body quantum state. In our derivation we review how the different "solution ingredients" of the Kitaev honeycomb model can be accounted for in the TN language, namely, Jordan-Wigner transformation, braidings of Majorana modes, fermionic Fourier transformation, and Bogoliubov transformation. The TN built in this way allows for a clear understanding of several properties of the model. In particular, we show how the fidelity diagram is straightforward both at zero temperature and at finite temperature in the vortex-free sector. We also show how the properties of two-point correlation functions follow easily. Finally, we also discuss the pros and cons of contracting of our 3d TN down to a 2d projected entangled pair state (PEPS) with finite bond dimension. The results in this paper can be extended to generalizations of the Kitaev model, e.g., to other lattices, spins, and dimensions.
Rubin, Bruce K
2016-09-01
Plastic bronchitis is an uncommon and probably underrecognized disorder, diagnosed by the expectoration or bronchoscopic removal of firm, cohesive, branching casts. It should not be confused with purulent mucous plugging of the airway as seen in patients with cystic fibrosis or bronchiectasis. Few medications have been shown to be effective and some are now recognized as potentially harmful. Current research directions in plastic bronchitis research include understanding the genetics of lymphatic development and maldevelopment, determining how abnormal lymphatic malformations contribute to cast formation, and developing new treatments. Copyright © 2016 Elsevier Inc. All rights reserved.
Institute of Scientific and Technical Information of China (English)
ZhouYouhe; GaoYuanwen; ZhengXiaojing
2004-01-01
The magneto-plastic instability of a ferromagnetic beam-type plate with simple supports and small initial imperfection is analytically investigated in this paper for that the plastic deformation of the plate with a linear-strain hardening relation is considered when the plate is located in a strong uniformly distributed magnetic field. After the distribution of magnetic fields related to the deflected configuration of plate is imaginably divided into two parts, i.e.,one is related to the flat plate and the other dependent on the perturbation of magnetic fields for which the plate configuration changes from the flat into the deformed state, the perturbation technique is employed to analyze the distribution of the perturbation magnetic fields in and out-of the magnetic medium of the ferromagnetic structure in a transverse magnetic field, which leads to some analytical formulae/solutions for the magnetic fields and the resulting magnetic force exerted on the plate. Based on them, the magneto-plastic buckling and snapping of the plate in a transverse magnetic field is discussed, and the critical magnetic field is analytically formulated in terms of the parameters of geometry and material of the plate employed by solving the governing equation of the magneto-plastic plate in the applied magnetic field. Further, the sensitivity of the initial imperfection on the magneto-plastic instability, expressed by an amplification function, is obtained by solving the dynamic equation of deflection of the plate after the inertial force in the transverse direction is taken into account. The results obtained show that the critical magnetic field is sensitive to the plastic characteristic, e.g., hardening coefficient, and the instability mode and deflection of the plate are dependent on the geometrical imperfection as well.
Mixed plastics recycling technology
Hegberg, Bruce
1995-01-01
Presents an overview of mixed plastics recycling technology. In addition, it characterizes mixed plastics wastes and describes collection methods, costs, and markets for reprocessed plastics products.
Antonella Del Rosso
2015-01-01
In terms of weight, the plastic pollution in the world’s oceans is estimated to be around 300,000 tonnes. This plastic comes from both land-based and ocean-based sources. A lecture at CERN by chemist Wolfgang Trettnak addressed this issue and highlighted the role of art in raising people’s awareness. Artwork by Wolfgang Trettnak. Packaging materials, consumer goods (shoes, kids’ toys, etc.), leftovers from fishing and aquaculture activities… our oceans and beaches are full of plastic litter. Most of the debris from beaches is plastic bottles. “PET bottles have high durability and stability,” explains Wolfgang Trettnak, a chemist by education and artist from Austria, who gave a lecture on this topic organised by the Staff Association at CERN on 26 May. “PET degrades very slowly and the estimated lifetime of a bottle is 450 years.” In addition to the beach litter accumulated from human use, rivers bring several ki...
Roggen, Marjolein
1998-01-01
De zonnecel van de toekomst is in de maak. Onderzoekers van uiteenlopend pluimage werken eendrachtig aan een plastic zonnecel. De basis is technisch gelegd met een optimale, door invallend licht veroorzaakte, vorming van ladingdragers binnen een composiet van polymeren en buckyballs. Nu is het zaak
Sukmaji, I. C.; Wijang, W. R.; Andri, S.; Bambang, K.; Teguh, T.
2017-01-01
Nowadays composite is a superior material used in automotive component due to its outstanding mechanical behavior. The sandwich polypropylene honeycomb core with carbon/glass fiber composite skin (SHCG) as based material in a floor component of electric car application is investigated in the present research. In sandwich structure form, it can absorb noise better compare with the conventional material [1]. Also in present paper, Finite Element Analysis (FEA) of SHCG as based material for floor component of the electric car is analyzed. The composite sandwich is contained with a layer uniform carbon fiber and mixing non-uniform carbon-glass fiber in upper and lower skin. Between skins of SHCG are core polypropylene honeycomb that it have good flexibility to form following dies profile. The variables of volume fraction ratio of carbon/glass fiber in SHCG skin are 20/80%, 30/70%, and 50/50%. The specimen of SHCG is tested using the universal testing machine by three points bending method refers to ASTM C393 and ASTM C365. The cross point between tensile strength to the volume fraction the mixing carbon/glass line and ratio cost line are the searched material with good mechanical performance and reasonable cost. The point is 30/70 volume fraction of carbon/glass fiber. The result of the testing experiment is become input properties of model structure sandwich in FEA simulation. FEA simulation approach is conducted to find critical strength and factor of complex safety geometry against varied distributed passenger loads of a floor component the electric car. The passenger loads variable are 80, 100, 150, 200, 250 and 300 kg.
Chen, Jinxiang; Tuo, Wanyong; Zhang, Xiaoming; He, Chenglin; Xie, Juan; Liu, Chang
2016-12-01
To develop lightweight biomimetic composite structures, the compressive failure and mechanical properties of fully integrated honeycomb plates were investigated experimentally and through the finite element method. The results indicated that: fracturing of the fully integrated honeycomb plates primarily occurred in the core layer, including the sealing edge structure. The morphological failures can be classified into two types, namely dislocations and compactions, and were caused primarily by the stress concentrations at the interfaces between the core layer and the upper and lower laminations and secondarily by the disordered short-fiber distribution in the material; although the fully integrated honeycomb plates manufactured in this experiment were imperfect, their mass-specific compressive strength was superior to that of similar biomimetic samples. Therefore, the proposed bio-inspired structure possesses good overall mechanical properties, and a range of parameters, such as the diameter of the transition arc, was defined for enhancing the design of fully integrated honeycomb plates and improving their compressive mechanical properties.
SiC-SiC and C-SiC Honeycomb for Advanced Flight Structures Project
National Aeronautics and Space Administration — The proposed project builds upon the work done in Phase I with the development of a C-SiC CMC honeycomb material that was successfully tested for mechanical...
Finite Element Analysis for In-Plane Crushing Behaviour of Aluminium Honeycombs
Institute of Scientific and Technical Information of China (English)
ZHU Feng; ZHAO Longmao; LU Guoxing
2006-01-01
A number of finite element simulations were performed to analyze the in-plane crushing behaviour of aluminium honeycombs and the results are presented and discussed.The simulations include both X1 and X2 cases.All the analyses are quasi-static,and can be divided into three groups,which are designed to investigate the effects of cell size,foil thickness and yield stress of the foil material,respectively,on the structural response of honeycombs.The result indicates that these factors can significantly affect the plateau stresses of honeycomb cellular structures in both directions,and the plateau stresses in X2 direction are slightly smaller than those in X1 direction.The simulation results were further compared with published theoretical predictions and show higher values.The difference was then analyzed and a new expression for the plateau stress of honeycombs was suggested.
Fabrication and gas sensing property of honeycomb-like ZnO
Institute of Scientific and Technical Information of China (English)
Chao Li; Zhi Shuo Yu; Shao Ming Fang; Huan Xin Wang; Yang Hai Gui; Jia Qiang Xu; Rong Feng Chen
2008-01-01
We report the structural characterization and proposed formation mechanism of honeycomb-like ZnO conglomerationsfabricated by direct precipitation method. X-ray diffraction (XRD), energy-disperse X-ray spectrometry (EDS), scanning electronmicroscopy (SEM) showed that the as-prepared ZnO calcined at 700℃ were micron sphere particles with honeycomb-likestructure. In the UV-vis absorbing spectrum, it was observed that there is a new additional absorption band at 260 nm, and it wasspeculated that the absorption may be caused by defects on the surface and interface of honeycomb-like ZnO. The as-productsshowed high sensitivity and short response time to sulfured hydrogen gas. These results demonstrate that honeycomb-like ZnOconglomerations are very promising materials for fabricating H2S gas sensors.2008 Chao Li. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Experimental study on absorption of blade vibration of honeycomb seal and shunt injection
Institute of Scientific and Technical Information of China (English)
Zhang Qiang; He Lidong; Huo Genglei; Che Jianye
2008-01-01
Honeycomb seals and shunt injection have been proposed to weaken the blade vibration. Honeycomb seals, as well as, smooth seals were tested with different seals' clearances and shrouded blades. The shunt injection was sprayed to the blade tip clearance in the reverse direction of the main flow. Experimental results showed that both honeycomb seals and shunt injection had the damping effect for blade vibration, and the blade vibration magnitude could be reduced by more than 25% and 17%, respectively. When the two methods were adopted synchronously, more than 1/3 of the blade vibration could be reduced. Consequently, adopting honeycomb seal and superinducing proper shunt injection are two useful ways to minimize vibration of the blade from the viewpoints of avoiding blade rupture and improving the rotor stability.
Monte Carlo study of the honeycomb structure of anthraquinone molecules on Cu(111)
Kim, Kwangmoo; Einstein, T. L.
2011-06-01
Using Monte Carlo calculations of the two-dimensional (2D) triangular lattice gas model, we demonstrate a mechanism for the spontaneous formation of honeycomb structure of anthraquinone (AQ) molecules on a Cu(111) plane. In our model long-range attractions play an important role, in addition to the long-range repulsions and short-range attractions proposed by Pawin, Wong, Kwon, and Bartels [ScienceSCIEAS0036-807510.1126/science.1129309 313, 961 (2006)]. We provide a global account of the possible combinations of long-range attractive coupling constants which lead to a honeycomb superstructure. We also provide the critical temperature of disruption of the honeycomb structure and compare the critical local coverage rate of AQ’s where the honeycomb structure starts to form with the experimental observations.
Riss, Fabian; Schilp, Johannes; Reinhart, Gunther
Due to their feasible geometric complexity, additive layer manufacturing (ALM) processes show a highpotential for the production of lightweight components.Therefore, ALM processes enable the realization of bionic-designedcomponents like honeycombs, which are optimized depending upon load and outer boundary conditions.This optimization is based on a closed-loop, three-steps methodology: At first, each honeycomb is conformed to the surface of the part. Secondly, the structure is optimizedfor lightweight design.It is possible to achieve a homogeneous stress distribution in the part by varying the wall thickness, honeycombdiameter and the amount of honeycombs, depending on the subjected stresses and strains. At last, the functional components like threads or bearing carriers are integrated directly into the honeycomb core.Using all these steps as an iterative process, it is possible to reduce the mass of sandwich components about 50 percent compared to conventional approaches.
Energy Technology Data Exchange (ETDEWEB)
Hong, Seok Min; Lee, Jang Il; Byun, Jae Ki; Choi, Young Don [Korea Univ., Seoul (Korea, Republic of)
2014-04-15
Thermal problems that are directly related to the lifetime of an electronic device are becoming increasingly important owing to the miniaturization of electronic devices. To solve thermal problems, it is essential to study thermal stability through thermal diffusion and insulation. A honeycomb sandwich plate has anisotropic thermal conductivity. To analyze the thermal deformation and temperature distribution of a system that employs a honeycomb sandwich plate, the thermal and elastic properties need to be determined. In this study, the thermal and elastic properties of a honeycomb sandwich plate, such as thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and shear modulus, are predicted. The properties of a honeycomb sandwich plate vary according to the hexagon size, thickness, and material properties.
Energy Technology Data Exchange (ETDEWEB)
Pires, A.S.T., E-mail: antpires@fisica.ufmg.br
2015-11-01
Using the SU(3) Schwinger boson formalism, also named the flavor theory, I study the ferroquadrupolar phase of the bilinear–biquadratic Heisenberg model on the honeycomb lattice at zero temperature. The dispersion relations, the quadrupole moment and the static quadrupole structure factor are calculated. - Highlights: • The ferroquadrupolar order on the honeycomb lattice was studied. • The SU(3) Schwinger boson formalism was used. • The static quadrupole structure factor was calculated.
Ko, Wen-Yin; Chen, You-Feng; Lu, Ke-Ming; Lin, Kuan-Jiuh
2016-01-01
The use of lightweight and easily-fabricated MnO2/carbon nanotube (CNT)-based flexible networks as binder-free electrodes and a polyvinyl alcohol/H2SO4 electrolyte for the formation of stretchable solid-state supercapacitors was examined. The active electrodes were fabricated from 3D honeycomb porous MnO2 assembled from cross-walled and interconnected sheet-architectural MnO2 on CNT-based plastic substrates (denoted as honeycomb MnO2/CNT textiles).These substrates were fabricated through a simple two-step procedure involving the coating of multi-walled carbon nanotubes (MWCNTs) onto commercial textiles by a dipping-drying process and subsequent electrodeposition of the interconnected MnO2 sheets onto the MWCNT-coated textile. With such unique MnO2 architectures integrated onto CNT flexible films, good performance was achieved with a specific capacitance of 324 F/g at 0.5 A/g. A maximum energy density of 7.2 Wh/kg and a power density as high as 3.3 kW/kg were exhibited by the honeycomb MnO2/CNT network device, which is comparable to the performance of other carbon-based and metal oxide/carbon-based solid-state supercapacitor devices. Specifically, the long-term cycling stability of this material is excellent, with almost no loss of its initial capacitance and good Coulombic efficiency of 82% after 5000 cycles. These impressive results identify these materials as a promising candidate for use in environmentally friendly, low-cost, and high-performance flexible energy-storage devices.
... PSN PSEN GRAFT Contact Us News Plastic Surgery Statistics Plastic surgery procedural statistics from the American Society of Plastic Surgeons. Statistics by Year Print 2016 Plastic Surgery Statistics 2015 ...
Institute of Scientific and Technical Information of China (English)
丁刚; 左然; 张旭鹏; 王坤
2011-01-01
对传统平板式太阳能空气集热器的流道进行了改进,把对角型进出口流道改为多进出口式流道.对改进的集热器的性能进行了试验测试.新的进出口流道消除了吸热板和空气换热不均的现象,出口温度提升明显.在相同条件下,集热器的瞬时效率增加约20%.用CFD方法对集热器内部的流场结构和传热进行的数值模拟对比表明,传统集热器内部存在流动死区,中心截面温度分布不均匀,吸热板上有局部的高温区域,改进后的集热器流场和温度场分布得较均匀.%The flow channels of traditional flat-plate solar air collector were changed from diagonal inlet/outlet to multi-inlet/outlet. Experimental investigation on characteristics of solar air collectors after the improvement of flow channels was reported. The inlet and outlet channels of the conventional air collector were improved. The new flow channel eliminates the ununiformity of heat transfer between air and absorber plate, so there is a distinct temperature increasing at the outlet. The instantaneous efficiency is improved by about 20％ at the same condition. An analysis of flow characteristics and heat transfer in the collectors had been carried out by using Computation Fluid Dynamic (CFD). There is the dead zone in flow field of traditional collector. The temperature distribution of center section is different and there is local high-temperature region on the heat-absorbing plate in the traditional collector, while the flow field and temperature distribution are uniform in the improved collector.
Institute of Scientific and Technical Information of China (English)
朱海威; 高文峰; 林文贤; 刘滔; 李泽东
2014-01-01
In this paper,the domestic solar water heater with a vertical storage tank and a flat-plat collector,which is commercially available and popular in the market,was experimentally in-vestigated.Firstly, natural circulation experiment platform of flat plate domestic solar water heater was set up.The effect of two different positions of upper connecting pipe on temperature variation in the water tank during the heating stage in the daytime and thermal performances was measured.Through the analysis of test data,The difference of temperature stratification in the water tank with upper connecting pipe at high position and at low position were studied re-spectively.Also the instantaneous efficiency in 10 minutes was defined and compared.The results showed that there was better temperature stratification in the water tank when it’s upper con-necting pipe at high position during heating stage.In addition,the instantaneous efficiency of so-lar water heater,which water tank with upper connecting pipe at high location under the natural circulation condition was superior to the water tank with upper circulation pipe at low position.%对一种常见的平板型立式储热水箱家用太阳能热水器进行试验分析。搭建了自然循环平板型家用太阳能热水器的实验平台。测量了两种不同位置的上循环管对白天加热阶段储热水箱温度变化及对热性能的影响，通过测试数据分析对比了高、低位上循环管循环时，水箱内温度变化、分层状况，定义了十分钟内的平均效率，并进行了比较。结果表明：储热水箱升温阶段采用高位上循环管的水箱内部出现较好的水温分层；高位上循环管热水器的自然循环瞬时效率比低位上循环管热水器的瞬时效率高。
Chandrasekharan, N.; Thompson, L. L.
2016-04-01
The limitations posed by batteries have compelled the need to investigate energy harvesting methods to power small electronic devices that require very low operational power. Vibration based energy harvesting methods with piezoelectric transduction in particular has been shown to possess potential towards energy harvesters replacing batteries. Current piezoelectric energy harvesters exhibit considerably lower power to weight ratio or specific power when compared to batteries the harvesters seek to replace. To attain the goal of battery-less self-sustainable device operation the power to weight ratio gap between piezoelectric energy harvesters and batteries need to be bridged. In this paper the potential of integrating lightweight honeycomb structures with existing piezoelectric device configurations (bimorph) towards achieving higher specific power is investigated. It is shown in this study that at low excitation frequency ranges, replacing the solid continuous substrate of conventional bimorph with honeycomb structures of the same material results in a significant increase in power to weight ratio of the piezoelectric harvester. At higher driving frequency ranges it is shown that unlike the traditional piezoelectric bimorph with solid continuous substrate, the honeycomb substrate bimorph can preserve optimum global design parameters through manipulation of honeycomb unit cell parameters. Increased operating lifetime and design flexibility of the honeycomb core piezoelectric bimorph is demonstrated as unit cell parameters of the honeycomb structures can be manipulated to alter mass and stiffness properties of the substrate, resulting in unit cell parameter significantly influencing power generation.
Institute of Scientific and Technical Information of China (English)
Lei ZHAO; Jun MA; Zhizhong SUN; Zhengqian LIU; Yixin YANG
2008-01-01
The ozonation of nitrobenzene in aqueous solu-tion was carried out in a semi-batch reactor to investigate the degradation efficiency, the effect factors, and the reaction mechanism, where honeycomb ceramic was used as a cata-lyst. The presence of honeycomb ceramic could improve the degradation rate of nitrobenzene by 15.46% compared to the results ofozonation alone. Under the conditions of this exper-iment, the degradation rate of honeycomb ceramic-catalyzed ozonation increased by 12.94% with the increase of the amount of catalyst from 1 to 5 blocks. The degradation rates all increased greatly with the increase of temperature and pH of the solution in the processes of honeycomb ceramic-catalyzed ozonation and ozonation alone. But, when the pH of the solution increased to 9.50, the advantage of the honey-comb ceramic-catalyzed ozonation process would be lost. The experimental findings indicated that in the processes of ozonation alone and honeycomb ceramic-catalyzed ozona-tion, nitrobenzene was primarily oxidized by·OH free radical in aqueous solution. The adsorption of nitrobenzene was too limited to have an important influence on the degradation rate of nitrobenzene. With the same total dosage of applied ozone, the multiple step addition of ozone showed much higher removal efficiency than that obtained by one step in the two processes.
Wave propagation in the polymer-filled star-shaped honeycomb periodic structure
Tang, Hsiang-Wen; Chou, Wei-Di; Chen, Lien-Wen
2017-08-01
The wave propagations in the periodic structure composed of auxetic star-shaped honeycombs are investigated. The matrix of the periodic structure is filled with polymer. The effective material properties of the unit cell of the periodic structure such as the Poisson's ratio, the Young's modulus, and the shear modulus are varied with different filling materials. The finite element method is used to solve the wave propagation within the auxetic star-shaped honeycombs. The dispersion analysis of the band structures and iso-frequency contour are presented. The auxeticity is found to have a significant effect on the wave propagation in the honeycomb structure, and the collimation of the auxetic star-shaped honeycomb structure is also studied. Effects of different types of filling on the wave propagation are also investigated. Among three filling types, the outer-filled honeycomb has the best self-collimation effect. The self-collimation of the polymer-filled auxetic honeycomb structure presented in this study can be applied to various acoustic devices.
One-to-one embedding between honeycomb mesh and Petersen-Torus networks.
Seo, Jung-Hyun; Sim, Hyun; Park, Dae-Heon; Park, Jang-Woo; Lee, Yang-Sun
2011-01-01
As wireless mobile telecommunication bases organize their structure using a honeycomb-mesh algorithm, there are many studies about parallel processing algorithms like the honeycomb mesh in Wireless Sensor Networks. This paper aims to study the Peterson-Torus graph algorithm in regard to the continuity with honeycomb-mesh algorithm in order to apply the algorithm to sensor networks. Once a new interconnection network is designed, parallel algorithms are developed with huge research costs to use such networks. If the old network is embedded in a newly designed network, a developed algorithm in the old network is reusable in a newly designed network. Petersen-Torus has been designed recently, and the honeycomb mesh has already been designed as a well-known interconnection network. In this paper, we propose a one-to-one embedding algorithm for the honeycomb mesh (HMn) in the Petersen-Torus PT(n,n), and prove that dilation of the algorithm is 5, congestion is 2, and expansion is 5/3. The proposed one-to-one embedding is applied so that processor throughput can be minimized when the honeycomb mesh algorithm runs in the Petersen-Torus.
Directory of Open Access Journals (Sweden)
Anil Kumar Singhi
2015-01-01
Full Text Available Plastic bronchitis, a rare but serious clinical condition, commonly seen after Fontan surgeries in children, may be a manifestation of suboptimal adaptation to the cavopulmonary circulation with unfavorable hemodynamics. They are ominous with poor prognosis. Sometimes, infection or airway reactivity may provoke cast bronchitis as a two-step insult on a vulnerable vascular bed. In such instances, aggressive management leads to longer survival. This report of cast bronchitis discusses its current understanding.
Flexural Behavior of Aluminum Honeycomb Core Sandwich Structure
Matta, Vidyasagar; Kumar, J. Suresh; Venkataraviteja, Duddu; Reddy, Guggulla Bharath Kumar
2017-05-01
This project is concerned with the fabrication and flexural testing of aluminium honey comb sandwich structure which is a special case of composite materials that is fabricated by attaching two thin but stiff skins to a light weight but thick core. The core material is normally low density material but its high thickness provide the sandwich composite with high bonding stiffness. Honeycomb core are classified into two types based on the materials and structures. Hexagonal shape has a unique properties i.e has more bonding strength and less formation time based on the cell size and sheet thickness. Sandwich structure exhibit different properties such as high load bearing capacity at low weight and has excellent thermal insulation. By considering the above properties it has tendency to minimize the structural problem. So honey comb sandwich structure is choosed. The core structure has a different applications such as aircraft, ship interiors, construction industries. As there is no proper research on strength characteristics of sandwich structure. So, we use light weight material to desire the strength. There are different parameters involved in this structure i.e cell size, sheet thickness and core height. In this project we considered 3 level of comparison among the 3 different parameters cell size of 4, 6 and 8 mm, sheet thickness of 0.3, 0.5 and 0.7 mm, and core height of 20,25 and 30 mm. In order to reduce the number of experiment we use taguchi design of experiment, and we select the L8 orthogonal array is the best array for this type of situation, which clearly identifies the parameters by independent of material weight to support this we add the minitab software, to identify the main effective plots and regression equation which involves the individual response and corresponding parameters. Aluminium material is used for the fabrication of Honeycomb sandwich structure among the various grades of aluminium we consider the AL6061 which is light weight material
CAPACITIVE TOMOGRAPHY FOR THE LOCATION OF PLASTIC PIPE
Energy Technology Data Exchange (ETDEWEB)
Brian J. Huber
2002-10-30
Throughout the utility industry, there is high interest in subsurface imaging of plastic, ceramic, and metallic objects because of the cost, reliability, and safety benefits available in avoiding impacts with the existing infrastructure and in reducing inappropriate excavations. Industry interest in locating plastic pipe has resulted in funding available for the development of technologies that enable this imaging. Gas Technology Institute (GTI) proposes to develop a compact and inexpensive capacitive tomography imaging sensor that takes the form of a flat plate or flexible mat that can be placed on the ground to image objects embedded in the soil. A compact, low-cost sensor that can image objects through soil could be applied to multiple operations and will produce a number of cost savings for the gas industry. In a stand-alone mode, it could be used to survey an area prior to excavation. The technology would improve the accuracy and reliability of any operation that involves excavation by locating or avoiding buried objects. An accurate subsurface image of an area will enable less costly keyhole excavations and other cost-saving techniques. Ground penetrating radar (GPR) has been applied to this area with limited success. Radar requires a high-frequency carrier to be injected into the soil: the higher the frequency, the greater the image resolution. Unfortunately, high-frequency radio waves are more readily absorbed by soil. Also, high-frequency operation raises the cost of the associated electronics. By contrast, the capacitive tomography sensor uses low frequencies with a multiple-element antenna to obtain good resolution. Low-frequency operation lowers the cost of the associated electronics while improving depth of penetration. The objective of this project is to combine several existing techniques in the area of capacitive sensing to quickly produce a demonstrable prototype. The sensor itself will take the form of a flat array of electrodes that can be
Analytical Round Robin for Elastic-Plastic Analysis of Surface Cracked Plates, Phase II Results
Allen, P. A.; Wells, D. N.
2017-01-01
The second phase of an analytical round robin for the elastic-plastic analysis of surface cracks in flat plates was conducted under the auspices of ASTM Interlaboratory Study 732. The interlaboratory study (ILS) had 10 participants with a broad range of expertise and experience, and experimental results from a surface crack tension test in 4142 steel plate loaded well into the elastic-plastic regime provided the basis for the study. The participants were asked to evaluate a surface crack tension test according to the version of the surface crack initiation toughness testing standard published at the time of the ILS, E2899-13. Data were provided to each participant that represent the fundamental information that would be provided by a mechanical test laboratory prior to evaluating the test result. Overall, the participant’s test analysis results were in good agreement and constructive feedback was received that has resulted in an improved published version of the standard E2899-15.
Analytical Round Robin for Elastic-Plastic Analysis of Surface Cracked Plates: Phase I Results
Wells, D. N.; Allen, P. A.
2012-01-01
An analytical round robin for the elastic-plastic analysis of surface cracks in flat plates was conducted with 15 participants. Experimental results from a surface crack tension test in 2219-T8 aluminum plate provided the basis for the inter-laboratory study (ILS). The study proceeded in a blind fashion given that the analysis methodology was not specified to the participants, and key experimental results were withheld. This approach allowed the ILS to serve as a current measure of the state of the art for elastic-plastic fracture mechanics analysis. The analytical results and the associated methodologies were collected for comparison, and sources of variability were studied and isolated. The results of the study revealed that the J-integral analysis methodology using the domain integral method is robust, providing reliable J-integral values without being overly sensitive to modeling details. General modeling choices such as analysis code, model size (mesh density), crack tip meshing, or boundary conditions, were not found to be sources of significant variability. For analyses controlled only by far-field boundary conditions, the greatest source of variability in the J-integral assessment is introduced through the constitutive model. This variability can be substantially reduced by using crack mouth opening displacements to anchor the assessment. Conclusions provide recommendations for analysis standardization.
The Existence of Topological Edge States in Honeycomb Plasmonic Lattices
Wang, Li; Xiao, Meng; Han, Dezhuan; Chan, C T; Wen, Weijia
2016-01-01
In this paper, we investigate the band properties of 2D honeycomb plasmonic lattices consisting of metallic nanoparticles. By means of the coupled dipole method and quasi-static approximation, we theoretically analyze the band structures stemming from near-field interaction of localized surface plasmon polaritons for both the infinite lattice and ribbons. Naturally, the interaction of point dipoles decouples into independent out-of-plane and in-plane polarizations. For the out-of-plane modes, both the bulk spectrum and the range of the momentum $k_{\\parallel}$ where edge states exist in ribbons are similar to the electronic bands in graphene. Nevertheless, the in-plane polarized modes show significant differences, which do not only possess additional non-flat edge states in ribbons, but also have different distributions of the flat edge states in reciprocal space. For in-plane polarized modes, we derived the bulk-edge correspondence, namely, the relation between the number of flat edge states at a fixed $k_\\p...
Kondo route to spin inhomogeneities in the honeycomb Kitaev model
Energy Technology Data Exchange (ETDEWEB)
Das, S. D.; Dhochak, K.; Tripathi, V.
2016-07-01
Paramagnetic impurities in a quantum spin liquid give rise to Kondo effects with highly unusual properties. We have studied the effect of locally coupling a paramagnetic impurity with the spin-1/2 honeycomb Kitaev model in its gapless spin-liquid phase. The ( impurity) scaling equations are found to be insensitive to the sign of the coupling. The weak and strong coupling fixed points are stable, with the latter corresponding to a noninteracting vacancy and an interacting, spin-1 defect for the antiferromagnetic and ferromagnetic cases, respectively. The ground state in the strong coupling limit in both cases has a nontrivial topology associated with a finite Z(2) flux at the impurity site. For the antiferromagnetic case, this result has been obtained straightforwardly owing to the integrability of the Kitaev model with a vacancy. The strong-coupling limit of the ferromagnetic case is, however, nonintegrable, and we address this problem through exact-diagonalization calculations with finite Kitaev fragments. Our exact diagonalization calculations indicate that the weak-to-strong coupling transition and the topological phase transition occur rather close to each other and are possibly coincident. We also find an intriguing similarity between the magnetic response of the defect and the impurity susceptibility in the two-channel Kondo problem.
Static and Fatigue Characterization of Nomex Honeycomb Sandwich Panels
Directory of Open Access Journals (Sweden)
Keskes Boualem
2013-07-01
Full Text Available The main benefits of using the sandwich concept in structural components are the high stiffness, good fatigue resistance and low weight ratios. Recent advances in materials and construction techniques have resulted in further improvement and increased uniformity of the sandwich composite properties. In order to use these materials in different applications, the knowledge of simply their static properties alone is not sufficient but additional information on their fatigue properties and durability are required. In this paper, first static and fatigue tests on four points bending of nomex honeycomb composite sandwich panels have been performed. Load/displacement and S-N fatigue curves are presented and analysed. Fatigue failure and damage modes are observed with an optical microscope and are discussed. The second is to address such fatigue behaviour by using a damage model and check it by experimentation. This fatigue damage model is based on stiffness degradation, which is used as a damage indicator. Two non-linear cumulative damage models derived from the chosen stiffness degradation equation are examined with assumption of linear Miner's damage summation. Predicted results are compared with available experimental data.
Experimental study on mechanical properties of aircraft honeycomb sandwich structures
Directory of Open Access Journals (Sweden)
Talebi Mazraehshahi H.
2010-06-01
Full Text Available Mechanical behaviour of sandwich panels under different conditions have been exprimentally studied in this research to increase the knowledge of aircraft sandwich panel structures and facilitate design criteria for aircraft structures. Tests were concentrated on the honeycomb sandwich structures under different loads including flexural, insert shear, flat wise tension and compression loads. Furthermore, effect of core density and face material on mechanical behavior of different samples were investigated and compared with analytical and FEM method. Effects of skin thickness on strength of honycomb sandwhich panels under shear pull out and moments have also been considerd in this study. According to this investigation, insert strength and flexural test under different load conditions is strongly affected by face thickness, but compression and tearoff (falt wise tensile properties of a sandwich panel depends on core material. The study concludes that the correlation between experimental results and the analytical predictions will enable the designer to predict the mechanical behaviour and strength of a sandwich beam; however, applied formula may lead engineers to unreliable results for shear modulus.
Dispersion of Lamb waves in a honeycomb composite sandwich panel.
Baid, Harsh; Schaal, Christoph; Samajder, Himadri; Mal, Ajit
2015-02-01
Composite materials are increasingly being used in advanced aircraft and aerospace structures. Despite their many advantages, composites are often susceptible to hidden damages that may occur during manufacturing and/or service of the structure. Therefore, safe operation of composite structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost effective method for defects monitoring in advanced structures due to their long propagation range and their sensitivity to defects in their propagation path. In this paper, some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures. The laboratory experiments involve a pitch-catch method in which a pair of movable transducers is placed on the outside surface of the structure for generating and recording the wave signals. The specific cases considered include an aluminum plate, a woven composite laminate and an aluminum honeycomb sandwich panel. The agreement between experimental, numerical and theoretical results are shown to be excellent in certain frequency ranges, providing a guidance for the design of effective inspection systems.
Bloch-Zener oscillations in a tunable optical honeycomb lattice
Energy Technology Data Exchange (ETDEWEB)
Uehlinger, Thomas; Greif, Daniel; Jotzu, Gregor; Esslinger, Tilman [Institute for Quantum Electronics, ETH Zurich, 8093 Zurich (Switzerland); Tarruell, Leticia [Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland and LP2N, Universite Bordeaux 1, IOGS, CNRS, 351 cours de la Liberation, 33405 Talence (France)
2013-12-04
Ultracold gases in optical lattices have proved to be a flexible tool to simulate many different phenomena of solid state physics [1, 2]. Recently, optical lattices with complex geometries have been realized [3, 4, 5, 6, 7], paving the way to simulating more realistic systems. The honeycomb structure has recently become accessible in an optical lattice composed of mutually perpendicular laser beams. This lattice structure exhibits topological features in its band structure – the Dirac points. At these points, two energy bands intersect linearly and the particles behave as relativistic Dirac fermions. In optical lattices, Bloch oscillations [8] resolved both in time and in quasi-momentum space can be directly observed. We make use of such Bloch-Zener oscillations to probe the vanishing energy gap at the Dirac points as well as their position in the band structure. In small band gap regions, we observe Landau-Zener tunneling [7, 9] to the second band and the regions of maximum transfer can be identified with the position of the Dirac points.
Stopping dynamics of ions passing through correlated honeycomb clusters
Balzer, Karsten; Schlünzen, Niclas; Bonitz, Michael
2016-12-01
A combined nonequilibrium Green functions-Ehrenfest dynamics approach is developed that allows for a time-dependent study of the energy loss of a charged particle penetrating a strongly correlated system at zero and finite temperatures. Numerical results are presented for finite inhomogeneous two-dimensional Fermi-Hubbard models, where the many-electron dynamics in the target are treated fully quantum mechanically and the motion of the projectile is treated classically. The simulations are based on the solution of the two-time Dyson (Keldysh-Kadanoff-Baym) equations using the second-order Born, third-order, and T -matrix approximations of the self-energy. As application, we consider protons and helium nuclei with a kinetic energy between 1 and 500 keV/u passing through planar fragments of the two-dimensional honeycomb lattice and, in particular, examine the influence of electron-electron correlations on the energy exchange between projectile and electron system. We investigate the time dependence of the projectile's kinetic energy (stopping power), the electron density, the double occupancy, and the photoemission spectrum. Finally, we show that, for a suitable choice of the Hubbard model parameters, the results for the stopping power are in fair agreement with ab initio simulations for particle irradiation of single-layer graphene.
Static and Fatigue Characterization of Nomex Honeycomb Sandwich Panels
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Keskes Boualem
2013-07-01
Full Text Available The main benefits of using the sandwich concept in structural components are the high stiffness, good fatigue resistance and low weight ratios. Recent advances in materials and construction techniques have resulted in further improvement and increased uniformity of the sandwich composite properties. In order to use these materials in different applications, the knowledge of simply their static properties alone is not sufficient but additional information on their fatigue properties and durability are required. In this paper, first static and fatigue tests on four points bending of nomex honeycomb composite sandwich panels have been performed. Load/displacement and S-N fatigue curves are presented and analysed. Fatigue failure and damage modes are observed with an optical microscope and are discussed. The second is to address such fatigue behaviour by using a damage model and check it by experimentation. This fatigue damage model is based on stiffness degradation, which is used as a damage indicator. Two non-linear cumulative damage models derived from the chosen stiffness degradation equation are examined with assumption of linear Miner's damage summation. Predicted results are compared with available experimental data.
A continuum of compass spin models on the honeycomb lattice
Zou, Haiyuan; Liu, Bo; Zhao, Erhai; Liu, W. Vincent
2016-05-01
Quantum spin models with spatially dependent interactions, known as compass models, play an important role in the study of frustrated quantum magnetism. One example is the Kitaev model on the honeycomb lattice with spin-liquid (SL) ground states and anyonic excitations. Another example is the geometrically frustrated quantum 120° model on the same lattice whose ground state has not been unambiguously established. To generalize the Kitaev model beyond the exactly solvable limit and connect it with other compass models, we propose a new model, dubbed ‘the tripod model’, which contains a continuum of compass-type models. It smoothly interpolates the Ising model, the Kitaev model, and the quantum 120° model by tuning a single parameter {θ }\\prime , the angle between the three legs of a tripod in the spin space. Hence it not only unifies three paradigmatic spin models, but also enables the study of their quantum phase transitions. We obtain the phase diagram of the tripod model numerically by tensor networks in the thermodynamic limit. We show that the ground state of the quantum 120° model has long-range dimer order. Moreover, we find an extended spin-disordered (SL) phase between the dimer phase and an antiferromagnetic phase. The unification and solution of a continuum of frustrated spin models as outline here may be useful to exploring new domains of other quantum spin or orbital models.
The honeycomb terrain on the Hellas basin floor, Mars: A case for salt or ice diapirism
Bernhardt, H.; Reiss, D.; Hiesinger, H.; Ivanov, M. A.
2016-04-01
We present quantitative plausibility studies of potential formation mechanisms for the "honeycomb" terrain on the northwestern Hellas basin floor. The honeycomb terrain is a unique landscape of ~10.5 × 5 km wide, mostly cell-shaped depressions that are arranged in a regular, dense pattern covering ~36,000 km2. We argue against the honeycombs being (peri)glacial landforms (till rings, iceberg imprints, and thermokarst) or the result of igneous diapirism, as terrestrial analogs do not reproduce their key characteristics. Fossilized impact melt convection cells also appear to be an unsuitable interpretation, as melt solidification should not permit such structures to be retained. We present arguments in favor of salt or ice diapirism as honeycomb formation models. Honeycomb-sized diapirs could be formed by a ~2 km thick salt layer (~72,000 km3 for the entire honeycomb terrain), which might have been derived from the highlands north of Hellas Planitia—an area of abundant chloride signatures and intense snowfall according to ancient Mars climate models. Nearby volcanic activity ~3.8 Ga ago potentially enabled recurring phases of (probably salty) meltwater runoff (as indicated by meandering channels) and might therefore have enabled evaporite deposition in the Hellas basin. Being twice as buoyant as salt, water ice would require an only ~1 km thick layer (i.e., ~36,000 km3) to form honeycomb-sized diapirs, which would be in agreement with a likely ~2 km thick ice stability zone beneath the Hellas basin floor. However, it would remain an open question as to why we find only one such ice diapir landscape on Mars.
A Maximum Entropy Approach to Assess Debonding in Honeycomb aluminum Plates
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Viviana Meruane
2014-05-01
Full Text Available Honeycomb sandwich structures are used in a wide variety of applications. Nevertheless, due to manufacturing defects or impact loads, these structures can be subject to imperfect bonding or debonding between the skin and the honeycomb core. The presence of debonding reduces the bending stiffness of the composite panel, which causes detectable changes in its vibration characteristics. This article presents a new supervised learning algorithm to identify debonded regions in aluminum honeycomb panels. The algorithm uses a linear approximation method handled by a statistical inference model based on the maximum-entropy principle. The merits of this new approach are twofold: training is avoided and data is processed in a period of time that is comparable to the one of neural networks. The honeycomb panels are modeled with finite elements using a simplified three-layer shell model. The adhesive layer between the skin and core is modeled using linear springs, the rigidities of which are reduced in debonded sectors. The algorithm is validated using experimental data of an aluminum honeycomb panel under different damage scenarios.
Manan, N. H.; Majid, D. L.; Romli, F. I.
2016-10-01
Sandwich structures with honeycomb core are known to significantly improve stiffness at lower weight and possess high flexural rigidity. They have found wide applications in aerospace as part of the primary structures, as well as the interior paneling and floors. High performance aluminum and aramid are the typical materials used for the purpose of honeycomb core whereas in other industries, materials such as fibre glass, carbon fibre, Nomex and also Kevlar reinforced with polymer are used. Recently, growing interest in developing composite structures with natural fibre reinforcement has also spurred research in natural fibre honeycomb material. The majority of the researches done, however, have generally emphasized on the usage of random chopped fibre and only a few are reported on development of honeycomb structure using unidirectional fibre as the reinforcement. This is mainly due to its processing difficulties, which often involve several stages to account for the arrangement of fibres and curing. Since the use of unidirectional fibre supports greater strength compared to random chopped fibre, a single-stage process in conjunction with vacuum infusion is suggested with a mould design that supports fibre arrangement in the direction of honeycomb loading.
Directory of Open Access Journals (Sweden)
Caiqi Zhao
2016-06-01
Full Text Available To solve the problem of critical buckling in the structural analysis and design of the new long-span hollow core roof architecture proposed in this paper (referred to as a “honeycomb panel structural system” (HSSS, lateral compression tests and finite element analyses were employed in this study to examine the lateral compressive buckling performance of this new type of honeycomb panel with different length-to-thickness ratios. The results led to two main conclusions: (1 Under the experimental conditions that were used, honeycomb panels with the same planar dimensions but different thicknesses had the same compressive stiffness immediately before buckling, while the lateral compressive buckling load-bearing capacity initially increased rapidly with an increasing honeycomb core thickness and then approached the same limiting value; (2 The compressive stiffnesses of test pieces with the same thickness but different lengths were different, while the maximum lateral compressive buckling loads were very similar. Overall instability failure is prone to occur in long and flexible honeycomb panels. In addition, the errors between the lateral compressive buckling loads from the experiment and the finite element simulations are within 6%, which demonstrates the effectiveness of the nonlinear finite element analysis and provides a theoretical basis for future analysis and design for this new type of spatial structure.
Detection of disbonds in a honeycomb composite structure using guided waves
Baid, Harsh; Banerjee, Sauvik; Joshi, Shiv; Mal, Siddhartha
2008-03-01
Advanced composites are being used increasingly in state-of-the-art aircraft and aerospace structures. In spite of their many advantages composite materials are highly susceptible to hidden flaws that may occur at any time during the life cycle of a structure and if undetected, may cause sudden and catastrophic failure of the entire structure. An example of such a defects critical structural component is the "honeycomb composite" in which thin composite skins are bonded with adhesives to the two faces of extremely lightweight and relatively thick metallic honeycombs. These components are often used in aircraft and aerospace structures due to their high strength to weight ratio. Unfortunately, the bond between the honeycomb and the skin may degrade with age and service loads leading to separation of the load-bearing skin from the honeycomb (called "disbonds") and compromising the safety of the structure. This paper is concerned with the noninvasive detection of disbonds using ultrasonic guided waves. Laboratory experiments are carried out on a composite honeycomb specimen containing localized disbonded regions. Ultrasonic waves are launched into the specimen using a broadband PZT transducer and are detected by a distributed array of identical transducers located on the surface of the specimen. The guided wave components of the signals are shown to be very strongly influenced by the presence of a disbond. The experimentally observed results are being used to develop an autonomous scheme to locate the disbonds and to estimate their size.
Fabrication and compressive performance of plain carbon steel honeycomb sandwich panels
Institute of Scientific and Technical Information of China (English)
Yu'an Jing; Shiju Guo; Jingtao Han; Yufei Zhang; Weijuan Li
2008-01-01
Plain carbon steel Q215 honeycomb sandwich panels were manufactured by brazing in a vacuum furnace. Their characteristic parameters, including equivalent density, equivalent elastic modulus, and equivalent compressive strength along out-of-plane (z-direction) and in-plane (x- and y-directions), were derived theoretically and then determined experimentally by an 810 material test system. On the basis of the experimental data, the compressive stress-strain curves were given. The results indicate that the measurements of equivalent Young's modulus and initial compressive strength are in good agreement with calculations, and that the maximum compressive strain near to solid can be up to 0.5-0.6 along out-of-plane, 0.6-0.7 along in-plane. The strength-to-density ratio of plain carbon steel honeycomb panels is near to those of Al alloy hexagonal-honeycomb and 304L stainless steel square-honeycomb, but the compressive peak strength is greater than that of Al alloy hexagonal-honeycomb.
Directory of Open Access Journals (Sweden)
Ulrich Martin
2010-01-01
Full Text Available Lightweight linear cellular composite materials on basis of austenite stainless TRIP- (TRansformation Induced Plasticity- steel as matrix with reinforcements of MgO partially stabilized zirconia (Mg-PSZ are described. Two-dimensional cellular materials for structural applications are conventionally produced by sheet expansion or corrugation processes. The presented composites are fabricated by a modified ceramic extrusion powder technology. Characterization of the microstructure in as-received and deformed conditions was carried out by optical and scanning electron microscopy. Magnetic balance measurements and electron backscatter diffraction (EBSD were used to identify the deformation-induced martensite evolution in the cell wall material. The honeycomb composite samples exhibit an increased strain hardening up to a certain engineering compressive strain and an extraordinary high specific energy absorption per unit mass and unit volume, respectively. Based on improved property-to-weight ratio such linear cellular structures will be of interest as crash absorbers or stiffened core materials for aerospace, railway, or automotive applications.
Polanco, Michael A.; Kellas, Sotiris; Jackson, Karen
2009-01-01
The performance of material models to simulate a novel composite honeycomb Deployable Energy Absorber (DEA) was evaluated using the nonlinear explicit dynamic finite element code LS-DYNA(Registered TradeMark). Prototypes of the DEA concept were manufactured using a Kevlar/Epoxy composite material in which the fibers are oriented at +/-45 degrees with respect to the loading axis. The development of the DEA has included laboratory tests at subcomponent and component levels such as three-point bend testing of single hexagonal cells, dynamic crush testing of single multi-cell components, and impact testing of a full-scale fuselage section fitted with a system of DEA components onto multi-terrain environments. Due to the thin nature of the cell walls, the DEA was modeled using shell elements. In an attempt to simulate the dynamic response of the DEA, it was first represented using *MAT_LAMINATED_COMPOSITE_FABRIC, or *MAT_58, in LS-DYNA. Values for each parameter within the material model were generated such that an in-plane isotropic configuration for the DEA material was assumed. Analytical predictions showed that the load-deflection behavior of a single-cell during three-point bending was within the range of test data, but predicted the DEA crush response to be very stiff. In addition, a *MAT_PIECEWISE_LINEAR_PLASTICITY, or *MAT_24, material model in LS-DYNA was developed, which represented the Kevlar/Epoxy composite as an isotropic elastic-plastic material with input from +/-45 degrees tensile coupon data. The predicted crush response matched that of the test and localized folding patterns of the DEA were captured under compression, but the model failed to predict the single-cell three-point bending response.
Overcoming maladaptive plasticity through plastic compensation
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Matthew R.J. MORRIS, Sean M. ROGERS
2013-08-01
Full Text Available Most species evolve within fluctuating environments, and have developed adaptations to meet the challenges posed by environmental heterogeneity. One such adaptation is phenotypic plasticity, or the ability of a single genotype to produce multiple environmentally-induced phenotypes. Yet, not all plasticity is adaptive. Despite the renewed interest in adaptive phenotypic plasticity and its consequences for evolution, much less is known about maladaptive plasticity. However, maladaptive plasticity is likely an important driver of phenotypic similarity among populations living in different environments. This paper traces four strategies for overcoming maladaptive plasticity that result in phenotypic similarity, two of which involve genetic changes (standing genetic variation, genetic compensation and two of which do not (standing epigenetic variation, plastic compensation. Plastic compensation is defined as adaptive plasticity overcoming maladaptive plasticity. In particular, plastic compensation may increase the likelihood of genetic compensation by facilitating population persistence. We provide key terms to disentangle these aspects of phenotypic plasticity and introduce examples to reinforce the potential importance of plastic compensation for understanding evolutionary change [Current Zoology 59 (4: 526–536, 2013].
Overcoming maladaptive plasticity through plastic compensation
Institute of Scientific and Technical Information of China (English)
Matthew R.J.MORRIS; Sean M.ROGERS
2013-01-01
Most species evolve within fluctuating environments,and have developed adaptations to meet the challenges posed by environmental heterogeneity.One such adaptation is phenotypic plasticity,or the ability of a single genotype to produce multiple environmentally-induced phenotypes.Yet,not all plasticity is adaptive.Despite the renewed interest in adaptive phenotypic plasticity and its consequences for evolution,much less is known about maladaptive plasticity.However,maladaptive plasticity is likely an important driver of phenotypic similarity among populations living in different environments.This paper traces four strategies for overcoming maladaptive plasticity that result in phenotypic similarity,two of which involve genetic changes (standing genetic variation,genetic compensation) and two of which do not (standing epigenetic variation,plastic compensation).Plastic compensation is defined as adaptive plasticity overcoming maladaptive plasticity.In particular,plastic compensation may increase the likelihood of genetic compensation by facilitating population persistence.We provide key terms to disentangle these aspects of phenotypic plasticity and introduce examples to reinforce the potential importance of plastic compensation for understanding evolutionary change.
PLASTIC ZONE OF SEMI-INFINITE CRACK INPLANAR KAGOME AND TRIANGULAR LATTICES
Institute of Scientific and Technical Information of China (English)
Xinming Qiu; Lianghong He; Yueqiang Qian; Xiong Zhang
2009-01-01
The fracture investigations of the planar lattices made of ductile cell walls are cur-rently limited to bending-dominated hexagonal honeycomb. In this paper, the plastic zones of stretching-dominated lattices, including Kagome and triangular lattices, are estimated by ana-lyzing their effective yield loci. The normalized in-plane yield loci of these two lattices are almost identical convex curves enclosed by 4 straight lines, which is almost independent of the relative density but is highly sensitive to the principal stress directions. Therefore, the plastic zones around the crack tip of Kagome and triangular are estimated to be quite different to those of the con-tinuum solid and also hexagonal lattice. The plastic zones predictions by convex yield surfaces of both lattices are validated by FE calculations, although the shear lag region caused by non-local bending effect in the Kagome lattice enlarges the plastic zone in cases of small ratio of Tp/l.
Torsional guided wave-based debonding detection in honeycomb sandwich beams
Zhu, Kaige; Qing, Xinlin P.; Liu, Bin
2016-11-01
Debonding is one of the most dangerous damages in honeycomb sandwich structures, which causes stiffness reduction and is invisible from the surface. Guided wave-based non-destructive evaluation is a promising approach with high sensitivity and high efficiency for debonding detection. A torsional guided wave method is proposed to inspect debonding damage in honeycomb sandwich beams, which is proved to be better in damage location for the beams in the paper than the flexural wave used before. The honeycomb heterogeneity effect on the interaction between guided waves and debonding are first investigated by finite element methods. Then the ability of torsional waves to determine debonding locations and sizes is discussed in detail. Finally, in order to verify the proposed method, experiments are carried out to inspect debonding damage with two sizes.
Fabrication and development of several heat pipe honeycomb sandwich panel concepts
Tanzer, H. J.
1982-06-01
The feasibility of fabricating and processing liquid metal heat pipes in a low mass honeycomb sandwich panel configuration for application on the NASA Langley airframe-integrated Scramjet engine was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts was evaluated within constraints dictated by existing manufacturing technology and equipment. The chosen design consists of an all-stainless steel structure, sintered screen facesheets, and two types of core-ribbon; a diffusion bonded wire mesh and a foil-screen composite. Cleaning, fluid charging, processing, and process port sealing techniques were established. The liquid metals potassium, sodium and cesium were used as working fluids. Eleven honeycomb panels 15.24 cm X 15.24 cm X 2.94 cm were delivered to NASA Langley for extensive performance testing and evaluation; nine panels were processed as heat pipes, and two panels were left unprocessed.
Tanzer, H. J.
1982-01-01
The feasibility of fabricating and processing liquid metal heat pipes in a low mass honeycomb sandwich panel configuration for application on the NASA Langley airframe-integrated Scramjet engine was investigated. A variety of honeycomb panel facesheet and core-ribbon wick concepts was evaluated within constraints dictated by existing manufacturing technology and equipment. The chosen design consists of an all-stainless steel structure, sintered screen facesheets, and two types of core-ribbon; a diffusion bonded wire mesh and a foil-screen composite. Cleaning, fluid charging, processing, and process port sealing techniques were established. The liquid metals potassium, sodium and cesium were used as working fluids. Eleven honeycomb panels 15.24 cm X 15.24 cm X 2.94 cm were delivered to NASA Langley for extensive performance testing and evaluation; nine panels were processed as heat pipes, and two panels were left unprocessed.
Hodge, Andrew J.; Walker, James L., II
2008-01-01
A probability of detection study was performed for the detection of impact damage using flash heating infrared thermography on a full scale honeycomb composite structure. The honeycomb structure was an intertank structure from a previous NASA technology demonstration program. The intertank was fabricated from IM7/8552 carbon fiber/epoxy facesheets and aluminum honeycomb core. The intertank was impacted in multiple locations with a range of impact energies utilizing a spherical indenter. In a single blind study, the intertank was inspected with thermography before and after impact damage was incurred. Following thermographic inspection several impact sites were sectioned from the intertank and cross-sectioned for microscopic comparisons of NDE detection and actual damage incurred. The study concluded that thermographic inspection was a good method of detecting delamination damage incurred by impact. The 90/95 confidence level on the probability of detection was close to the impact energy that delaminations were first observed through cross-sectional analysis.
The Total Hemispheric Emissivity of Painted Aluminum Honeycomb at Cryogenic Temperatures
Tuttle, J.; Canavan, E.; DiPirro, M.; Li, X.; Knollenberg, K.
2013-01-01
NASA uses high-emissivity surfaces on deep-space radiators or thermal radiation absorbers in test chambers. Aluminum honeycomb core material, when coated with a high-emissivity paint, provides a lightweight, mechanically robust, and relatively inexpensive black surface that retains its high emissivity down to low temperatures. At temperatures below about 100 Kelvin, this material performs much better than the paint itself. We measured the total hemispheric emissivity of various painted honeycomb configurations using an adaptation of an innovative technique developed for characterizing thin black coatings. These measurements were performed from room temperature down to 30 Kelvin. We describe the measurement technique and compare the results with predictions from a detailed thermal model of each honeycomb configuration.
Abd Kadir, N.; Aminanda, Y.; Ibrahim, M. S.; Mokhtar, H.
2016-10-01
A statistical analysis was performed to evaluate the effect of factor and to obtain the optimum configuration of Kraft paper honeycomb. The factors considered in this study include density of paper, thickness of paper and cell size of honeycomb. Based on three level factorial design, two-factor interaction model (2FI) was developed to correlate the factors with specific energy absorption and specific compression strength. From the analysis of variance (ANOVA), the most influential factor on responses and the optimum configuration was identified. After that, Kraft paper honeycomb with optimum configuration is used to fabricate foam-filled paper honeycomb with five different densities of polyurethane foam as filler (31.8, 32.7, 44.5, 45.7, 52 kg/m3). The foam-filled paper honeycomb is subjected to quasi-static compression loading. Failure mechanism of the foam-filled honeycomb was identified, analyzed and compared with the unfilled paper honeycomb. The peak force and energy absorption capability of foam-filled paper honeycomb are increased up to 32% and 30%, respectively, compared to the summation of individual components.
Institute of Scientific and Technical Information of China (English)
Liu Weidong; Zhu Hua; Zhou Shengqiang; Bai Yalei; Wang Yuan; Zhao Chunsheng
2013-01-01
A novel 0-Poisson's ratio cosine honeycomb support structure of flexible skin is proposed.Mechanical model of the structure is analyzed with the energy method,finite element method (FEM) and experiments have been performed to validate the theoretical model.The in-plane characteristics of the cosine honeycomb are compared with accordion honeycomb through analytical models and experiments.Finally,the application of the cosine honeycomb on a variable camber wing is studied.Studies show that mechanical model agrees well with results of FEM and experiments.The transverse non-dimensional elastic modulus of the cosine honeycomb increases (decreases) when the wavelength or the wall width increases (decreases),or when the amplitude decreases (increases).Compared with accordion honeycomb,the transverse non-dimensional elastic modulus of the cosine honeycomb is smaller,which means the driving force is smaller and the power consumption is less during deformation.In addition,the cosine honeycomb can satisfy the deforming requirements of the variable camber wing.
Energy Technology Data Exchange (ETDEWEB)
Roach, Dennis Patrick; Rackow, Kirk A.
2004-06-01
The FAA's Airworthiness Assurance NDI Validation Center, in conjunction with the Commercial Aircraft Composite Repair Committee, developed a set of composite reference standards to be used in NDT equipment calibration for accomplishment of damage assessment and post-repair inspection of all commercial aircraft composites. In this program, a series of NDI tests on a matrix of composite aircraft structures and prototype reference standards were completed in order to minimize the number of standards needed to carry out composite inspections on aircraft. Two tasks, related to composite laminates and non-metallic composite honeycomb configurations, were addressed. A suite of 64 honeycomb panels, representing the bounding conditions of honeycomb construction on aircraft, was inspected using a wide array of NDI techniques. An analysis of the resulting data determined the variables that play a key role in setting up NDT equipment. This has resulted in a set of minimum honeycomb NDI reference standards that include these key variables. A sequence of subsequent tests determined that this minimum honeycomb reference standard set is able to fully support inspections over the full range of honeycomb construction scenarios found on commercial aircraft. In the solid composite laminate arena, G11 Phenolic was identified as a good generic solid laminate reference standard material. Testing determined matches in key velocity and acoustic impedance properties, as well as, low attenuation relative to carbon laminates. Furthermore, comparisons of resonance testing response curves from the G11 Phenolic NDI reference standard was very similar to the resonance response curves measured on the existing carbon and fiberglass laminates. NDI data shows that this material should work for both pulse-echo (velocity-based) and resonance (acoustic impedance-based) inspections.