An Improved Generalized Model for Predicting Frost Growth on a Cold Flat Plate

2010 ◽  
Author(s):  
Q. C. Guo ◽  
W. Wang ◽  
J. Xiao ◽  
W. P. Lu
Keyword(s):  
Experimental Data ◽  
Flat Plate ◽  
Current Model ◽  
Theoretical Models ◽  
Maximum Error ◽  
Open Loop ◽  
Experimental Conditions ◽  
Wide Range ◽  
Semi Empirical ◽  
Frost Growth

A generalized quasi-steady and one-dimensional model for predicting the frost growth on flat plate was proposed based on the previous theoretical models. To improve the predicting ability of the current model, a modified semi-empirical correlation for calculating initial condition of frost density was presented experimentally. The experiments were conducted in a suction-type open-loop wind tunnel under a series of experimental conditions: air temperature −8°C to 19°C, humidity 42% to 80%, velocity 5m/s and the temperature of cold plate −16°C to −8°C. The numerical results of frost thickness, frost density, frost surface temperature and heat flux rate were compared to the experimental data. The simulation results were found agree with the experimental results in a maximum error of 10%. The presented model was further validated by comparing with the previous published experimental data in a wide range of frosting conditions. It was found that the presented model was a simple but universal one to predict the frost growth on cold flat plate.

A Review of Flow Pattern of Boiling Flowing in the Tube

2012 ◽  
Vol 569 ◽  
pp. 301-304
Author(s):  
Jun Xia Zhang ◽  
N. Nuoribusiren
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flow Pattern ◽  
Boiling Heat Transfer ◽  
Theoretical Models ◽  
Experimental Conditions ◽  
Flow Pattern Map ◽  
Flow Pattern Transition ◽  
Boiling Flow ◽  
Semi Empirical

Both boiling flowing and heat transfer has widely applied to engineering. The predictions of boiling heat transfer depend on the characteristics of boiling flow pattern, and thus it is necessary to comprehend the update development of flow pattern of boiling heat transfer. At the present work, the recent investigations were reviewed, and these findings mainly focus on the classification of various flow patterns and the transition of flow pattern. The obtained flow pattern map is mainly based on the experimental data from air-water at adiabatic conditions. These investigations tend to propose a simple and general flow pattern map; however, the limitation of both experimental conditions and the number of experimental data modifies the goal. Analysis of flow pattern transition has been developed from few semi-empirical and semi-theoretical models; its application has been limited because of complexity of flow pattern and many determinant factors.

LIQUIDUS THERMO-BAROMETER FOR THE MODELING OF MAGNETITE — MELT EQUILIBRIUM

2018 ◽  
pp. 71-80
Author(s):  
N. S. Aryaeva ◽  
E. V. Koptev-Dvornikov ◽  
D. A. Bychkov
Keyword(s):  
Experimental Data ◽  
Liquidus Temperature ◽  
Vertical Structure ◽  
Maximum Error ◽  
Silicate Melt ◽  
System Of Equations ◽  
Wide Range ◽  
Basaltic Melts ◽  
Multidimensional Statistics

A system of equations of thermobarometer for magnetite-silicate melt equilibrium was obtained by method of multidimensional statistics of 93 experimental data of a magnetite solubility in basaltic melts. Equations reproduce experimental data in a wide range of basalt compositions, temperatures and pressures with small errors. Verification of thermobarometers showed the maximum error in liquidus temperature reproducing does not exceed ±7 °C. The level of cumulative magnetite appearance in the vertical structure of Tsypringa, Kivakka, Burakovsky intrusions predicted with errors from ±10 to ±50 m.

Modeling and Experimental Validation of a Reed Check Valve for Hydraulic Applications

2016 ◽  
Author(s):  
Anthony L. Knutson ◽  
James D. Van de Ven
Keyword(s):  
Internal Combustion Engines ◽  
Check Valve ◽  
Maximum Error ◽  
Fast Response ◽  
Single Element ◽  
Hydraulic Systems ◽  
Test Bed ◽  
Experimental Conditions ◽  
Wide Range ◽  
Reed Valve

Reed valves are a type of check valve commonly found in a wide range of applications including air compressors, internal combustion engines, and even the human heart. While reed valves have been studied extensively in these applications, published research on the modeling and application of reed valves in hydraulic systems is severely lacking. Because the spring and mass components of a reed valve are contained in a single element, it is light and compact compared to traditional disc, poppet, or ball style check valves. These advantages make reed valves promising for use in high frequency applications such as piston pumps, switch-mode hydraulics, and digital hydraulics. Furthermore, the small size and fast response of reed valves provide an opportunity to design pumps capable of operating at higher speeds and with lower dead volumes, thus increasing efficiency and power density. In this paper, a modeling technique for reed valves is presented and validated in a hydraulic piston pump test bed. Excellent agreement between modeled and experimentally measured reed valve opening is demonstrated. Across the range of experimental conditions, the model predicts the pump delivery with an error typically less than 1% with a maximum error of 2.2%.

scholarly journals A Calculation Model of the General Theory of Interaction Potentials for Stoichiometric Lanthanide Type Crystals: Applications to the Cs2KLnCl6 System

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Andres Soto ◽  
Shanavas Shajahan ◽  
Roberto Acevedo
Keyword(s):  
General Theory ◽  
Chemical Elements ◽  
Current Model ◽  
Theoretical Models ◽  
Calculation Model ◽  
Lanthanide Ions ◽  
Interaction Potentials ◽  
Model Calculations ◽  
Advantages And Disadvantages ◽  
Semi Empirical

AbstractThis article aims to develop a generalized model calculation model to be applicable to the general theory of interaction potentials with reference to the stoichiometric elpasolite type crystals. In this study, we have chosen to report both a theoretical model and a calculation strategy to undertake semi empirical calculations of thermodynamic properties, such as reticular energies and heats of formation for the series of systems such as: Cs2KLnCl6. We have also carried out quite a number of calculations for a variety of systems such as: Cs2NaLnF6, Cs2NaLnCl6, Cs2NaLnBr6, Rb2NaLnF6and Cs2KLnF6 in the Fm3m space group since we aim to check the strengths and weaknesses of our model calculations. We have analyzed a substantial number of approximate theoretical models and have carried a formidable amount of computing simulations to estimate the reticular energies and the corresponding heat of formation for these type of crystal using a semi empirical model. We made use of the thermodynamic cycles of Born-Haber so as to get a broad view with reference to the accuracy of our semi empirical theoretical models. The problem itself is quite challenging since we have focused our attention upon trivalent lanthanide ions $$L{n}^{+3}$$Ln+3 in the first inner transition series of the chemical elements: (Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu). There are a significant amount of outstanding research works published in the literature with reference to structural analysis, one photon spectroscopy, vibrionic intensity model calculations and generalized models to deal with these kind of complex crystals. The calculated energy values associated with these observables seems to be most reasonable, and these follow the expected trends, as may be expected on both theoretical and experimental grounds. Both, the advantages and disadvantages of the current model calculations, have been tested against other previous calculations performed for this type of complex systems. It is of a paramount importance, the results obtained and reported in this article with regards to convergence tests as well as some master equations derived to account for the various contributions to the total energy. The Born-Mayer-Buckingham potential is carefully examined with reference to these lanthanide type crystals Cs2KLnCl6. Finally but not at last, the most likely sources for improvement are carefully discussed in this work. We strongly believe that there is enough room for improvement and have therefore initiated a new research program of activities tackling systems of well-known optical and structural properties.

Modified Algebraical Cebeci --- Smith Turbulent Viscosity Model for the Entire Surface of a Blunted Cone

2020 ◽  
pp. 28-41
Author(s):  
V.V. Gorskiy ◽  
A.G. Loktionova
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Experimental Studies ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Entire Surface ◽  
Wide Range ◽  
Semi Empirical ◽  
Transfer Properties ◽  
Turbulent Pulsations

In order to compute the intensity of laminar-turbulent heat transfer, algebraic or differential models are commonly used, which are designed to compute the contribution of turbulent pulsations to the transfer properties of the gas. This, in turn, dictates the necessity of validating these semi-empirical models against experimental data obtained under conditions simulating the gas dynamics inherent to the phenomenon as observed in practice. The gas dynamic patterns observed during gradient flow around fragments of aircraft structure (such as a sphere or a cylinder) differs qualitatively from the patterns revealed by the flow around the lateral surfaces of these fragments, which necessitates using various semi-empirical approaches in this case, followed by mandatory validation against the results of respective experimental studies. In recent years, there appeared scientific publications dealing with modifying one of the algebraic models designed to compute the contribution of turbulent pulsations in the boundary layer to the transfer properties of the gas; this was accomplished by making use of experimental data obtained for a hemisphere at extremely high Reynolds numbers. The paper proposes a similar modification of the same turbulence model, based on fitting a wide range of experimental data obtained for lateral surfaces of spherically blunted cones. As a result of the investigations conducted, we stated a method for computing laminar-to-turbulent heat transfer over the entire surface of a blunted cone; the accuracy of the method is acceptable in terms of most practical applications. We show that the computational method presented is characterised by minimum error as compared to the most widely spread methods for solving this problem

On the Minimum Film Boiling Conditions for Spherical Geometries

1980 ◽  
Vol 102 (2) ◽  
pp. 335-341 ◽  
Author(s):  
F. S. Gunnerson ◽  
A. W. Cronenberg
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Flat Plate ◽  
Analytical Method ◽  
Boiling Point ◽  
Film Boiling ◽  
Heater Surface ◽  
Wide Range ◽  
Minimum Heat ◽  
Good Agreement

An analytical method is presented for predicting the minimum heater temperature and the minimum heat flux at the onset of film boiling for spherical and flat plate heaters in saturated and subcooled liquids. Consideration is given to a variety of factors known to affect the minimum film boiling point, including transient liquid-heater contact, interfacial wettability, heater geometry, and liquid subcooling. The theoretical correlations developed are the first known predictions for spherical geometries. A comparison of theory with experimental data indicates good agreement for the minimum heat flux and the minimum film boiling temperature. Results indicate that the minimum conditions may span a wide range depending upon the thermophysical nature of the heater surface and the boiling liquid.

Intensification of mass transfer in sieve plate bubble columns

1979 ◽  
Vol 44 (2) ◽  
pp. 348-360 ◽  
Author(s):  
Jindřich Zahradník
Keyword(s):  
Liquid Mixture ◽  
Empirical Relation ◽  
Bubble Columns ◽  
Sieve Plate ◽  
Experimental Conditions ◽  
Wide Range ◽  
Bubble Layer ◽  
Semi Empirical ◽  
Reactor Diameter ◽  
Free Area

The effect was studied of gas distribution on the character of the gas-liquid mixture and its porosity in 0.15 and 0.30 m in diameter bubble reactors. The experiments covered a wide range of gas-liquid mixture height to reactor diameter ratios (2-18) with the superficial gas velocities ranging between 0.015 and 0.184 m/s. The gas was distributed by a sieve plate of 0.2 or 0.5% free area exhibiting various configurations of the openings. The obtained experimental evidence suggests that the degree of affecting the character of the bubble layer and its porosity through the design of the distributing plate varies in dependence on the size of the bubble layer. The effect was evaluated of the size of the bubbling layer and the plate free area on the porosity for uniformly bubbling columns. The nonlinear course of the experimentally found dependences of porosity on the superficial velocity of gas was fitted by a simple semi-empirical relation valid for the whole range of experimental conditions covered by experiments.

scholarly journals Thermal analysis of a serpentine flat plate collector and investigation of the flow and convection regime

2019 ◽  
Vol 23 (1) ◽  
pp. 47-59 ◽  
Author(s):  
Dimitrios Korres ◽  
Christos Tzivanidis
Keyword(s):  
Flat Plate ◽  
Current Model ◽  
Flow Simulation ◽  
Special Kind ◽  
Theoretical Models ◽  
Temperature Fields ◽  
Piping System ◽  
Transfer Coefficients ◽  
Inclination Angles ◽  
Flat Plate Collector

A special kind of flat plate collectors was examined in detail through CFD analysis. The distinctiveness of the current model has to do with the piping system was applied which is a serpentine flow conduit. The operation of the collector was examined at four different inclination angles (0?, 15?, 30?, and 45?) and several values of the inlet water temperature (10-80?C per 10?C) by providing the same heat perpendicular to the cover in each case. The thermal efficiency as well as the temperature fields of the collector was determined first. Furthermore, the overall heat losses were calculated and compared to these arisen from the Cooper-Dunkle assumption while the mean divergence between these two solutions was around 5%. Moreover, the natural convection inside the gap as well as the tube to water convection was examined and the heat transfer coefficients were validated from theoretical models in horizontal position. In particular, the simulation results found to diverge from the theoretical ones about 12.5% and 7% as regards the pipe flow and the air-gap, respectively. In addition, a remarkable flow phenomenon was observed at the bends of the pipe and the nature of it was explained in detail. Last but not least, the inclination angle seems that affects significantly the collector?s performance since the higher the slope the lower the convection losses. Solidworks and its simulation program Flow Simulation were used to design and simulate the whole collector.

scholarly journals Photochemical laws and visual phenomena

1946 ◽  
Vol 133 (870) ◽  
pp. 63-75 ◽  
Keyword(s):  
Experimental Data ◽  
Recovery Process ◽  
Visual Sensitivity ◽  
Rapid Recovery ◽  
Foveal Vision ◽  
Experimental Conditions ◽  
Reciprocity Law ◽  
Wide Range ◽  
Visual Phenomena ◽  
Nervous Transmission

By measuring the course of recovery of visual sensitivity in the dark, after exposure to light, it has been demonstrated that all the phenomena of recovery can be explained—qualitatively—by the known fundamental principles of photochemistry. In particular, the reciprocity law, which is widely valid in photographic processes, only holds under certain limited circumstances for visual phenomena. In the case of foveal vision the reciprocity law does not hold, owing to the rapid recovery process, except for very brief periods of exposure. In the case of parafoveal vision the recovery process for the scotopic mechanism is sufficiently slow to allow validity of the reciprocity law over a wide range of exposure periods, although the law still breaks down for the parafoveal photopic mechanism. This circumscribed validity of the reciprocity law is of practical service in that the effect of many experimental conditions can be predicted from a very limited set of suitably chosen experimental data. It may be noted that it has not been found necessary to introduce any postulate involving recovery of the nervous transmission system as part of the recovery process.

Modeling and Experimental Validation of a Reed Check Valve for Hydraulic Applications

2020 ◽  
Vol 142 (11) ◽  
Author(s):  
Anthony L. Knutson ◽  
James D. Van de Ven
Keyword(s):  
Internal Combustion Engines ◽  
Check Valve ◽  
Maximum Error ◽  
Fast Response ◽  
Single Element ◽  
Hydraulic Systems ◽  
Test Bed ◽  
Experimental Conditions ◽  
Wide Range ◽  
Reed Valve

Abstract Reed valves are a type of check valve commonly found in a wide range of applications including air compressors, internal combustion engines, musical instruments, and even the human heart. While reed valves have been studied extensively in these applications, published research on the modeling and application of reed valves in hydraulic systems is sparse. Because the spring and mass components of a reed valve are contained in a single element, it is light and compact compared to traditional disk, poppet, or ball style check valves. These advantages make reed valves promising for use in high-frequency applications such as piston pumps, switch-mode hydraulics, and digital hydraulics. Furthermore, the small size and fast response of reed valves provide an opportunity to design pumps capable of operating at higher speeds and with lower dead volumes, thus increasing efficiency and power density. In this paper, a modeling technique for reed valves is presented and validated in a hydraulic piston pump test bed. Excellent agreement between modeled and experimentally measured reed valve opening is demonstrated. Across the range of experimental conditions, the model predicts the pump delivery with an error typically less than 1% with a maximum error of 2.2%.

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