scholarly journals SET-UP OF A KUNDT’S TUBE TO OBTAIN THE SPEED OF SOUND AT DIFFERENT TEMPERATURES.

Anales AFA ◽  
2019 ◽  
pp. 42-46
Author(s):  
I. Novara ◽  
M. Matar ◽  
M.A. Parodi ◽  
A. Roatta ◽  
B.J. Gómez ◽  
...  
Keyword(s):  
Speed Of Sound ◽  
Classical Model ◽  
Adiabatic Process ◽  
Resonance Signal ◽  
Oscilloscope Screen ◽  
Different Temperatures ◽  
Set Up ◽  
Experimental Values ◽  
Acoustic Phenomenon ◽  
Air Column

In this work we describe how we designed and built an acoustic system that allowed us to adapt a Kundt’s tube for the measurement of the speed of sound at different temperatures. The air column inside the tube was excited by a speaker at a frequency of 2 kHz. We changed the air column length by moving a piston throughout the tube, and we measured and recorded that length when we observed a resonance signal on the oscilloscope screen. This procedure was repeated at different temperatures, ranging from 19○C to 115○C. Then it was calculated the propagation of the speed of sound based on the temperature. The results were compared with those predicted by the classical model, which assumes that air is an ideal diatomic gas, and that the acoustic phenomenon is an adiabatic process. Finally, it was found a satisfactory agreement between the experimental values and those predicted by the classical model

scholarly journals The Investigation of Effects of Temperature and Nanoparticles Volume Fraction on the Viscosity of Copper Oxide-ethylene Glycol Nanofluids

2017 ◽  
Author(s):  
Mohammad Hemmat Esfe
Keyword(s):  
Ethylene Glycol ◽  
Copper Oxide ◽  
Volume Fraction ◽  
Relative Viscosity ◽  
Experimental Results ◽  
Different Temperatures ◽  
Nanoparticles Volume Fraction ◽  
Effects Of Temperature ◽  
Nanofluid Viscosity ◽  
Experimental Values

In the present article, the effects of temperature and nanoparticles volume fraction on the viscosity of copper oxide-ethylene glycol nanofluid have been investigated experimentally. The experiments have been conducted in volume fractions of 0 to 1.5 % and temperatures from 27.5 to 50 °C. The shear stress computed by experimental values of viscosity and shear rate for volume fraction of 1% and in different temperatures show that this nanofluid has Newtonian behaviour. The experimental results reveal that in a given volume fraction when temperature increases, viscosity decreases, but relative viscosity varies. Also, in a specific temperature, nanofluid viscosity and relative viscosity increase when volume fraction increases. The maximum amount of increase in relative viscosity is 82.46% that occurs in volume fraction of 1.5% and temperature of 50 °C. Some models of computing nanofluid viscosity have been suggested. The greatest difference between the results obtained from these models and experimental results was down of 4 percent that shows that there is a very good agreement between experimental results and the results obtained from these models.

scholarly journals Thermal Conductivities of Choline Chloride-Based Deep Eutectic Solvents and Their Mixtures with Water: Measurement and Estimation

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3816
Author(s):  
Taleb H. Ibrahim ◽  
Muhammad A. Sabri ◽  
Nabil Abdel Jabbar ◽  
Paul Nancarrow ◽  
Farouq S. Mjalli ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Choline Chloride ◽  
Deep Eutectic Solvents ◽  
Standard Uncertainty ◽  
Heat Transfer Fluids ◽  
Wide Range ◽  
Different Temperatures ◽  
Experimental Values ◽  
Water Measurement ◽  
Thermal Conductivities

The thermal conductivities of selected deep eutectic solvents (DESs) were determined using the modified transient plane source (MTPS) method over the temperature range from 295 K to 363 K at atmospheric pressure. The results were found to range from 0.198 W·m−1·K−1 to 0.250 W·m−1·K−1. Various empirical and thermodynamic correlations present in literature, including the group contribution method and mixing correlations, were used to model the thermal conductivities of these DES at different temperatures. The predictions of these correlations were compared and consolidated with the reported experimental values. In addition, the thermal conductivities of DES mixtures with water over a wide range of compositions at 298 K and atmospheric pressure were measured. The standard uncertainty in thermal conductivity was estimated to be less than ± 0.001 W·m−1·K−1 and ± 0.05 K in temperature. The results indicated that DES have significant potential for use as heat transfer fluids.

Determination of Recrystallization Kinetics Model of 30Cr2Ni4MoV Steel Based on Dislocation Density

2017 ◽  
Vol 263 ◽  
pp. 59-66
Author(s):  
Peng Zhou ◽  
Qing Xian Ma
Keyword(s):  
Dislocation Density ◽  
Model Comparison ◽  
Kinetics Model ◽  
Structure Evolution ◽  
Metallographic Analysis ◽  
Recrystallization Kinetics ◽  
Proposed Model ◽  
Different Temperatures ◽  
Predicted Values ◽  
Experimental Values

A new model to predict the structure evolution of 30Cr2Ni4MoV steel is proposed based on the dislocation density in this research. Hot compression of 30Cr2Ni4MoV steel is carried out on Gleeble 1500 at different temperatures from 1233 K to 1473 K with a strain rate of 0.01 s-1 and the deformed samples are immediately quenched by water to frozen the austenite structure. The recrystallization kinetics model of 30Cr2Ni4MoV steel is successfully established by inverse analysis of the flow curve based on the relation between flow stress and dislocation density. In order to validate the proposed model, comparison between the predicted values and experimental values obtained by metallographic analysis is implemented. It is shown that the predicted results agree with the experimental results well.

scholarly journals Comparative analysis of cycloid pump based on CFD and fluid structure interactions

2020 ◽  
Vol 12 (11) ◽  
pp. 168781402097353
Author(s):  
Wang Yanhua ◽  
Huang Longlong ◽  
Liu Yong ◽  
Xu Jingsong
Keyword(s):  
Model Building ◽  
Contact Point ◽  
Great Influence ◽  
Test Results ◽  
Fluid Structure Interactions ◽  
Fluid Structure ◽  
Mean Values ◽  
Calculation Results ◽  
Different Temperatures ◽  
Set Up

At present, in the aspect of numerical simulation of cycloid pump, most studies focused on CFD (Computational Fluid Dynamics) in analyzing the pump performance under different service conditions (such as speed, temperature, etc.). The characteristics of the pump under FSI (Fluid Solid Interaction) have not been considered yet. By means of the dynamic mesh technique in the rotating domain, the fluid structure coupling interface is set up on a cycloidal pump model building in COMSOL. The simulation results obtained by applying CFD and FSI are improved by experimental verification. The results show that: (1) the average flow rate of FSI simulation is closer to the test results, and the mean values of CFD and FSI pressure are closer to the actual outlet boundary settings; (2) by comparing the velocity and pressure of rotation region of CFD and FSI at different temperatures, it is concluded that the pressure CFD calculated in the region is more than FSI, and the velocity CFD calculated is less than FSI; (3) by comparing the pressure distribution at some contact point of the fluid structure coupling interface, it is concluded that the fluctuation value of the pressure of CFD with time is greater than that of FSI. Through the comparison, it is found that the coupling has a great influence on the calculation results. The FSI analysis of the pump makes the analysis results more real and more conducive to the analysis of the flow field and rotor dynamics characteristics of the pump.

Evaluation of Low-Temperature Properties and the Fragility of Asphalt Binders with Non-Arrhenius Viscosity–Temperature Dependence

2005 ◽  
Vol 1901 (1) ◽  
pp. 44-51 ◽  
Author(s):  
Huachun Zhai ◽  
Delmar Salomon
Keyword(s):  
Temperature Dependence ◽  
Asphalt Binders ◽  
Arrhenius Behavior ◽  
Direct Tension ◽  
Different Temperatures ◽  
Rotational Viscosity ◽  
Liquid Fragility ◽  
The Difference ◽  
Critical Cracking Temperature ◽  
Experimental Values

Rotational viscosities of different asphalt binders were determined at temperatures between 80°C and 185°C. Viscosity–temperature dependence of asphalt binders was described with the use of the Vogel–Tammann–Fulcher (VTF) and the William–Landel–Ferry (WLF) equations. The Vogel temperature ( Tv) and the glass transition temperature ( Tg) for different asphalt binders were determined by fitting experimental values of viscosity at different temperatures with these two equations. For asphalt binders, the difference between Tv and Tg was about 40K. Effects of asphaltenes, aging, chemical modification, and polymer content on these temperatures were evaluated. As asphaltene content increased, both temperatures, Tv and Tg, increased. Different polymers showed different effects on these temperatures. The values of Tv and Tg were correlated with the critical cracking temperature ( Tcr) determined through use of a bending beam rheometer and a direct tension tester. The results suggested that the correlations between Tv, Tg, and Tcr could be used to determine Tcr from the rotational viscosity results tested at high temperature. With simple rotational measurements, a quick estimation of Tcr of asphalt binders could be obtained. Liquid fragility theory was also used to study Tg of asphalt binders. Parameters determined with the VTF and WLF equations indicated that asphalt binders behaved as fragile liquids because of their non-Arrhenius behavior in the temperature range studied.

Electric charge transfer associated with temperature gradients in ice

1961 ◽  
Vol 260 (1303) ◽  
pp. 523-536 ◽  
Keyword(s):  
Charge Transfer ◽  
Electric Charge ◽  
Contact Time ◽  
Temperature Gradients ◽  
Potential Difference ◽  
Contact Period ◽  
Maximum Charge ◽  
Different Temperatures ◽  
Electric Potentials ◽  
Set Up

The development of electric potentials in ice crystals under the influence of temperature gradients is investigated both theoretically and experimentally. The maintenance of a steady temperature gradient across a piece of ice is accompanied by concentration gradients of H + and OH - ions; because of the much greater mobility of H + ions, these diffuse more rapidly into the colder part of the ice and, in the steady state, a potential difference is set up across the ice crystal, the colder end being positive. A theory of this effect predicts a surface density of charge on the ends of the ice of σ = 5 x 10 -5 (d T /d x ) e. s. u. cm -2 and a potential difference across a uniform specimen of about 2Δ T mV, where Δ T is the temperature difference across the ends. These values are quite well confirmed by a series of experiments on specimens of highly purified ice. When two pieces of ice of initially different temperatures are brought into temporary contact and separated, the warmer acquires a negative charge and the colder an equal positive charge. The theory indicates that a maximum charge transfer of 3 x 10 -3 Δ T , e. s. u. cm -2 should occur with a contact time of about 0.01 s and that it should thereafter decline as the two pieces of ice become more nearly equal in temperature. The theoretical value for the charge developed for a contact time of ~ 0.01 s is well confirmed by experiments which also show that very little charge separation occurs if the contact period exceeds ½ s. Experiments in which the ice was contaminated with carbon dioxide, hydrofluoric acid, and sodium chloride in concentrations of up to 50 times that normally present in rain water, showed that the electrification was not greatly influenced by these impurities. These phenomena are thought to be of basic importance in the generation of electric charge in thunderstorms, this aspect being developed in the following paper.

Experimental Non-Linear Model Updating Applied in Cylindrical Journal Bearings

2001 ◽  
Author(s):  
Katia Lucchesi Cavalca ◽  
Sérgio Junichi Idehara ◽  
Franco Giuseppe Dedini ◽  
Robson Pederiva
Keyword(s):  
Linear Model ◽  
Model Updating ◽  
Optimization Method ◽  
Model Parameters ◽  
Numeric Model ◽  
Rotating Systems ◽  
Non Linear ◽  
Symmetric Rotor ◽  
Set Up ◽  
Experimental Values

Abstract The present paper proposes the use of non linear model updating applying unrestricted optimization method, in order to obtain a methodology, which allows the calibration of mathematical models in rotating systems. An experimental set up for this purpose consists of a symmetric rotor, on a rigid foundation supported by two hidrodynamic cylindrical bearings and with a central disk of considerable mass, working as na unbalancing excitation force. Once the numeric and experimental values are obtained, error vectors are defined, which are the minimization parameters, through the variation of the numeric model parameters. The method presented satisfactory results, as it was able to calibrate the mathematical model, and then to obtain reliable responses for the physical system studied. The research also presents a contribution for the rotating machine desing area as it presents a relatively simple methodology on the updating and revalidation of computacional models for machines and structures.

High Pressure Supercritical Carbon Dioxide Separation from its Mixture with Nitrogen at Different Temperatures

2020 ◽  
Vol 1008 ◽  
pp. 1-14
Author(s):  
Rehab M. El-Maghraby ◽  
Mahmoud Ramzy ◽  
Ahmed K. Aboul-Gheit
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Membrane Separation ◽  
Point Sources ◽  
Gas Mixture ◽  
Carbon Dioxide Separation ◽  
Different Temperatures ◽  
Supercritical Phase ◽  
High Concentrations ◽  
Set Up

Carbon dioxide (CO2) capturing from point sources is currently being proposed as a way to minimize CO2 emissions to the atmosphere. Carbon dioxide is considered one of the greenhouse gases that affects our environment. Legislations are being enforced in many countries to limit CO2 emissions to the atmosphere. Two methods are mostly used for CO2 capturing from flue gases and natural gases; the first method is absorption using amine-based solvents, while the second is membrane separation. The first method is effective for CO2 separation from gas mixtures with low CO2 concentration in the range of 10 to 20%, while the other can handle gas mixture with intermediate CO2 concentration but there is a limit on the CO2 purity. Hence, such methods cannot be used in pre-combustion and oxy fuel technologies where a more concentrated CO2 gas stream is produced. Throughout this work, a new method is introduced to separate carbon dioxide from its mixture with nitrogen (N2) at high concentrations, 90 mol.% CO2 and 10 mol.% N2 gas mixture. A customized high-pressure experimental set-up was built. Three temperature were tested: 15 °C, 25 °C and 38 °C at 150 bar. At such condition CO2 will be in the liquid and the supercritical phase respectively. The composition of the top and bottom streams where analyzed. The amount of CO2 in the top stream was the smallest at the supercritical condition. In addition, the purity of CO2 in the bottom stream was the highest at 38 °C and 150 bars, when CO2 is at the supercritical phase.

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