Experimental Temperature Values Research Articles

Diagnostics of carbon arc plasma under formation of carbon-encapsulated iron nanoparticles by optical emission and absorption spectroscopy

Absorption and emission spectra pertaining to the electronic transition a 3Πu–d 3Πg (0–0 band) of C2 molecule as present in the carbon arc discharge zone are analysed to determine the temperature and C2 radical content in function of carbon–iron anode composition. One of the objectives was to explore the use of emission and absorption, both approximate, methods for diagnostics of carbon arc plasma used for synthesis of carbon-encapsulated iron nanoparticles. The theory behind both methods was exploited to estimate the errors resulting from both approximate methods. The results obtained showed that the uncertainty in the determination of average temperatures and C2 column densities should not exceed ±3% and 10%, respectively. Contrary to these predictions, the experimental values of temperature and C2 column density determined from the plasma radiation significantly exceeded those resulting from the absorption measurements. It is concluded that some non-equilibrium state is between the ground (a 3Πu) and excited (d 3Πg) electronic states in carbon arc plasma under consideration. The column density distributions of non-excited C2 radical were transformed into radial concentration distributions, and then to carbon vapour pressures assuming thermodynamic equilibrium between carbon species. Both quantities rise with Fe content in the anode. Additionally, clear relationship between the carbon vapour pressure and the yield of carbon encapsulated iron nanoparticles synthesis was found.

A formulation for the flow rate of a fluid passing through an orifice plate from the First Law of Thermodynamics

This work presents a new equation to calculate the mass flow rate through an orifice plate for both natural gas and air samples using a thermodynamic approach. This simple equation does not contain the Reynolds number (viscosity does not appear), thus the calculation is explicit in the mass flow rate, not iterative. Because of its fundamental thermodynamic basis, the resulting expression does not include an expansion factor or discharge coefficient. The energy balance for the orifice plate coupled with experimental values of pressure, temperature, molar composition, densities, geometrical dimensions, and mass flow rates are available for several data sets covering distribution natural gas and air. A simple expression using dimensionless numbers: ΔP/P, diameter ratio (β), and heat capacity ratio (CP/CV) describes the kinetic energy changes calculated from the experimental values. The resulting mass flow rates for natural gas are within±0.4% (2σ) for 0≤(ΔP/P)≤0.3.

Detailed Study of Fluid Flow and Heat Transfer in the Abrasive Grinding Contact Using Computational Fluid Dynamics Methods

This paper introduces a set of research oriented computational fluid dynamics (CFD) 3D models used to simulate the fluid flow and heat transfer in a grinding process. The most important features of these models are described and some representative simulation results are presented, along with comparisons to published experimental data. Distributions of temperatures, pressures, velocities, and liquid volume fractions in and around the grinding region are obtained in great detail. Such results are essential in studying the influence of the fluid on the grinding process, as well as in determining the best fluid composition and supply parameters for a given application. The simulation results agree well with experimental global flow rates, temperature, and pressure values, showing the feasibility of CFD simulations in grinding applications.

Effect of Pressure Gradient on Film Cooling From Holes Supplemented by Anti-Vortex Holes

An experimental test rig is constructed to study the effect of pressure gradient on different configurations of the anti-vortex film cooling technique. This technique depends on adding a pair of cylindrical anti-vortex holes branching out from the main cylindrical film cooling holes to mitigate the effect of kidney vortices that causes the jet to lift off. Four different values of velocity ratios (VR), (Coolant Jet Velocity/Main Stream Velocity) namely VR=0.5, 1.0, 1.5, and 2.0, are studied with three different positions of anti-vortex holes. A single row of 30o angled holes on a flat surface, under zero pressure gradient along the downstream test surface, is taken as a baseline case. The numerical study is carried out using FLUENT commercial code using the k-e model. The density ratio is taken in consideration. Numerical results are first compared with experimental values of temperatures and film cooling effectiveness and the comparisons verified the numerical model. Both of experimental and numerical studies show that the new technique improves the film cooling effectiveness.The numerical velocity vectors in the boundary layer region showed that the anti-vortex holes create reverse vortices against the main vortices that are created by the main hole. These reverse vortices help in keeping the coolant jet flow near the surface. The adverse pressure gradient decreases the film cooling effectiveness while the presence of favorable pressure gradient increases the film cooling effectiveness.

The experimental validation of a CFD model for a heating oven with natural air circulation

This paper discusses a 3-D Computational Fluid Dynamics (CFD) model and presents experimental analysis of the flow and thermal processes within a laboratory heating oven with a natural air circulation. This device is used to store laboratory samples and products at a high, constant and spatially uniform temperature. The mathematical model included heat conduction in the insulated walls and convective and radiative (between walls) heat transfer in the volume of air within the oven. To formulate the mathematical model, a number of experiments were carried out to determine the temperature boundary conditions along the U-shaped heaters and the emissivity of the internal and external walls to determine the radiative heat fluxes. In addition, to validate the spatial temperature and velocity fields in the storage chamber and on the external oven walls, a set of thermocouples and Particle Image Velocimetry (PIV) were employed. The existing device was assessed in four configurations using a certification procedure that was performed at its maximum temperature level. The device was then numerically simulated using the mathematical model developed for this study. The results show satisfactory agreement between the experimental and computational velocity and temperature values. Furthermore, this study developed potential changes for the construction of this device that will improve the temperature uniformity within the storage space.

Prediction of Physical Properties of Dimethacrylate Polymer Networks by a Group Contribution Approach

In this work, the correlation between experimental and theoretical values of density (ρ) and glass transition temperature (T g ) of dimethacrylate polymer networks is elaborated. The developed methodologies are based on the additive principle of the known monomer chemical structures. The predicted values of ρ differed by a maximum of 1% from the experimental values. The methodology developed for T g prediction is based on the assumption that dimethacrylate structural units are treated as main chains between ‒CH2C(CH3)‒ tri-functional volumeless cross-links. Three-quarters of the calculated T g values differed less than 20 K from the experimental ones.

Some Implications of an Alternate Equation for the BCS Energy Gap

A set of generalized-BCS equations (GBCSEs) was recently derived from a temperature-dependent Bethe-Salpeter equation and shown to deal satisfactorily with the experimental data comprising the Tcs and the multiple gaps of a variety of high-temperature superconductors (SCs). These equations are formulated in terms of the binding energies W1(T),W2(T),… of Cooper pairs (CPs) bound via one- and more than one-phonon exchange mechanisms; they contain no direct reference to the gap/s of an SC. Applications of these equations so far were based on the observation that for elemental SCs |W01|=△0 at T = 0 inthe limit of the dimensionless BCS interaction parameter λ→0. Here △0 is the zero-temperature gap whence it follows that the binding energy of a CP bound via one-phonon exchanges at T = 0 is 2|W01|. In this note we carry out a detailed comparison between the GBCSE-based W1(T) and the BCS-based energy gap △(T) for all 0≤T≤Tc and realistic, non-vanishingly-small values of λ. Our study is based on the experimental values of Tc Debye temperature , and ?0 of several selected elements including the “bad actors” such as Pb and Hg. It is thus established that the equation for W1(T) provides a viable alternative to the BCS equation for △(T). This suggests the use of, when required, the equation for W2(T) which refers to CPs bound via two-phonon exchanges, for the larger of the two T-dependent gaps of a non-elemental SC. These considerations naturally lead one to the concept of T-dependent interaction parameters in the theory of superconductivity. It is pointed out that such a concept is needed both in the well-known approach of Suhl et al. to multi-gap superconductivity and the approach provided by the GBCSEs. Attention is drawn to diverse fields where T-dependent Hamiltonians have been fruitfully employed in the past.

Soybean Seed Yield and Quality as a Response to Field Pennycress Residue

ABSTRACTField pennycress (Thlaspi arvense L.; hereafter pennycress) is an oilseed crop being investigated as an off‐season biofuel source that can potentially fit into the existing crop rotation cycle with soybean [Glycine max (L.) Merr.]. The objective of this 2‐yr study was to evaluate the effect of pennycress residue on seed yield and quality components of soybean planted during five consecutive weeks, from mid‐May to mid‐June. In 2009 and 2010, the mean soybean dry weight seed yield after pennycress residue for all planting dates (4108 and 3490 kg ha−1, respectively) was greater than yield from fallow control plots (3636 and 2992 kg ha−1, respectively). However, in 2010, soybean planted after pennycress had slightly lower oil content (202 g kg−1) than that obtained from fallow control plots (207 g kg−1) (P < 0.01). Delayed planting until mid‐June resulted in lower population density, plant height, seed yield, and oil concentration. Before June, planting date had no significant influence on soybean seed yield and quality. Protein content in soybean seed was not affected by year, pennycress residue, or planting date. Variation in the experimental year temperature values led to significant changes in oil components. High temperatures decreased levels of linoleic, linolenic, and stearic acids but increased levels of palmitic and oleic acids. Overall, pennycress had no negative effect on the subsequent soybean crop.

Predicting retention in reverse‐phase liquid chromatography at different mobile phase compositions and temperatures by using the solvation parameter model

The prediction capability of the solvation parameter model in reverse-phase liquid chromatography at different methanol-water mobile phase compositions and temperatures was investigated. By using a carefully selected set of solutes, the training set, linear relationships were established through regression equations between the logarithm of the solute retention factor, logk, and different solute parameters. The coefficients obtained in the regressions were used to create a general retention model able to predict retention in an octadecylsilica stationary phase at any temperature and methanol-water composition. The validity of the model was evaluated by using a different set (the test set) of 30 solutes of very diverse chemical nature. Predictions of logk values were obtained at two different combinations of temperature and mobile phase composition by using two different procedures: (i) by calculating the coefficients through a mathematical linear relationship in which the mobile phase composition and temperature are involved; (ii) by using a general equation, obtained by considering the previous results, in which only the experimental values of temperature and mobile phase composition are required. Predicted logk values were critically compared with the experimental values. Excellent results were obtained considering the diversity of the test set.

Behavior of dowelled and bolted steel-to-timber connections exposed to fire

This study focuses on the load distributions among fasteners in steel-to-timber connections loaded in tension parallel-to-grain under fire exposure. The experimental results of some types of connections with various geometrical configurations are available. The influence of the type of fasteners (bolt, dowel) on the thermo-mechanical behavior of the connections is studied. A three-dimensional finite element model validated on the basis of experimental results is used. Good agreements were observed between the simulated and the experimental values of temperatures and failure times. The type of metal fasteners is crucial to the thermo-mechanical behavior of connections. In the studied connections, one bolt is used in each row of fasteners to prevent the separation between the assembled members. The presence of the bolts greatly influences the behavior of the connections mainly under fire. Various geometrical configurations of connections with only dowels or changing the positions of the bolts are studied. An analytical approach is proposed, from a specific type of connections, by varying some influent geometrical characteristics. A numerical experimental design is realized from the calculated time to failure of the connections.

Computational Fluid Dynamics Analysis of Greenhouses with Artificial Heat Tube

With the workmanship decrease in farms, the necessity to rationalize the use of other inputs and the development of technology has rapidly expanded the use of computer simulation in agricultural systems. One of the agricultural systems in which the modeling process of plant growth has been more engaged is the greenhouse production for horticultural crops. In Mediterranean climate, it is during the night that the energy losses are important and can be compensated with an artificial heat input. In this work an experiment was performed in a greenhouse in the north of Portugal. Temperature values in several points and air velocity in the aperture were measured during the night for three different cases: natural convective heating (case A); artificial heating tubes (AHT) (case B); AHT and natural ventilation (case C). A CFD simulation, carried out using FLOTRAN module of ANSYS, was also performed in two-dimensional configuration to obtain the indoor air temperature and velocity fields for the three cases. A very good agreement between experimental and numerical temperature values were verified, which allows to validate the adopted numerical procedure. In case A, the average temperature was 2.2℃. An average increase of 6.7℃ and 3.5℃ on the air temperature was obtained for the case B and case C, respectively. These results clearly emphasis the influence of each thermal load on greenhouse indoor air properties.

English

Forced convection heat transfer coefficient and friction factor are determined for flow of water and nanofluid in a vertical packed bed column. The analysis is undertaken in the laminar and transition Reynolds number range. The column is filled with spherical glass beads as the bed material. The heat transfer coefficients with Al2O3 nanofluid increased by 12 to 15% with the increase of volume concentration from 0.02 to 0.5% compared to water. The experimental values of axial temperature are in good agreement with NTU-? method proposed by Schumann's model.

A CFD greenhouse night-time condensation model

A computational fluid dynamics (CFD) model for simulating greenhouse night-time climate and condensation is presented. The model was applied to a four-span plastic covered greenhouse. Film condensation was simulated by applying a user defined function (UDF) added to the commercial CFD package. The CFD model was verified by comparing CFD predictions with experimental measurements. The effect of cover temperature on greenhouse humidity was then determined by the CFD model and compared to experimental results. Root mean square values for the differences between the CFD and experimental values of internal temperature and humidity showed there was good agreement between. The results showed the importance of heat transfer losses by radiation, particularly for low values of soil heat flux (SHF). They also showed the roof was the coolest surface in the greenhouse, and therefore the sink for the water vapour produced by the crop. For each configuration (SHF 10, 25, 50 and 100 W m−2 and equivalent sky temperature 263 K, 273 K and 276 K), the condensation rate curves and relative humidity (RH) evolution are presented. It was observed that all the condensation rate curves had the same characteristic shape and could be represented by a single logistic function. The response of the CFD model to a step-change in the water vapour source (night-time transpiration from the crop) was then analysed. It was observed that the model predicted the same steady-state temperature, RH and condensation rate independent of the time when the water vapour source was enabled. The CFD condensation model is intended to be used for the design of strategies for humidity control, particularly in unheated greenhouses.

Finite element study of residual stresses and distortions in arc welding with a trailing liquid nitrogen heat sink

PurposeThe purpose of this paper is to study the effect of trailing liquid nitrogen (LN2) heat sink on arc welding of mild steel plates. The effect on temperature field, stress and distortions are studied using experimental and numerical methods.Design/methodology/approachThe methodology consists of experimental and numerical methods. The temperature measured at a point near the arc is used to estimate the cooling capacity of the heat sink using inverse heat transfer (IHT) method. The estimated cooling flux is applied to the finite element model to study the stress and distortions using LN2 heat sink. The stresses are measured using X‐ray diffraction technique and the distortions using dial gauges.FindingsIHT method has been employed in estimating the cooling capacity of the LN2 jet. This has been applied to welding to study the effect on weld induced stresses and distortions. The method can be extended to calculate the heat removal rate in various manufacturing processes where cooling is employed.Research limitations/implicationsThe lack of temperature dependent material properties resulted in deviation of stresses between analytical results and experiment values.Originality/valueIHT method developed for heat removal capacity of trailing heat sink is a contribution. The estimated heat flux shows good agreement in analytical and experimental temperature values. These temperatures have been extended to calculate stresses and out of plane distortions in welding and there is a reasonable agreement between finite element analysis and experimental results.

3-D CFD Parametric Study of the Impact of the Fluid Properties and Delivery Conditions on Flow and Heat Transfer in Grinding

Fluids have an important role in grinding. Correct fluid application results in enhanced process stability, better work piece quality, and tool life. This paper shows that Computational Fluid Dynamics (CFD) models can be used to simulate the fluid flow and heat transfer in a grinding process, replacing numerous experiments that are expensive, time-consuming, and have limited capabilities. The most important properties of created 3-D model are described, along with results obtained. The results show very detailed distributions of temperatures, pressures, and flow rates in and around the grinding region. The data obtained is essential in studying the influence of the grinding fluid on the grinding process, as well as in determining the best fluid composition and supply parameters for a given application. The results agree well with experimental global flow rates and temperature values and show the feasibility of 3-D CFD-based simulations in grinding applications. The parametric studies of influence of several fluid physical properties on useful flow rates and temperatures were presented as well.

Multibands±Eliashberg theory and temperature-dependent spin-resonance energy in iron pnictide superconductors

The phenomenology of iron pnictide superconductors can be explained in the framework of a three-band s± wave Eliashberg theory with only two free parameters plus a feedback effect, i.e., the effect of the condensate on the antiferromagnetic spin fluctuations responsible for the superconductivity in these compounds. I have examined the experimental data of four materials, LaFeAsO1−xFx , SmFeAsO1−xFx, Ba1−xKxFe2As2, and Ba(FexCo1−x )2As2, and I have found that it is possible to reproduce the experimental critical temperature and gap values in a moderate strong-coupling regime, λtot ≈ 1.7 − 2.0

Modeling of the temperature field of the casting ladle lining

We propose a method for calculating the temperature field of the casting ladle lining by a modified relaxation method. Given such initial data as the metal temperature in the ladle, the ambient temperature, and the lining structure, this method permits calculating the stationary temperature fields both inside the lining and on the surface of the ladle jacket. The model was tested by comparing experimentally measured temperature values on the surface of the ladle jacket with calculated temperatures. A satisfactory agreement between calculated and experimental temperature values of the ladle surface has been obtained.

Mean square amplitudes of vibration and associated Debye temperatures of rhenium, osmium and thallium

The directional mean square amplitudes of vibration, Debye–Waller factors and associated Debye temperatures of hexagonal rhenium, osmium and thallium have been obtained from X-ray integrated intensities. The integrated intensities have been measured with a Philips 3020 powder diffractometer fitted with a proportional counter using filtered CuKα radiation at room temperature and have been corrected for thermal diffuse scattering. Within the limits of experimental errors, the anisotropy observed in these parameters is negligible. The experimental values of directional Debye temperature have been compared with corresponding values obtained from theoretical calculations. Vacancy formation energies of Re, Os and Tl have been estimated using a relation connecting it with the X-ray Debye temperature.

Three-bands±Eliashberg theory and the superconducting gaps of iron pnictides

Superconductivity in iron pnictides has been recently proposed to be due to spin-fluctuation mediated coupling between hole and electron bands with order parameters of opposite sign. BCS multiband models give qualitative predictions but cannot simultaneously reproduce the experimental values of critical temperature and energy gaps. We show, instead, that a three-band strong-coupling Eliashberg model can quantitatively reproduce the gaps and their temperature dependence in both the 1111 and 122 families. We also show that this requires small typical boson energies (in agreement with experiments) and high values of the electron-boson coupling constants.

Heat transfer modelling on windows and glazing under the exposure of solar radiation

Due to the effect of solar radiation on windows and glazing system the evaluation of heat flow is of primary importance in modeling the thermal performance within building interiors to account thermal comfort and overall energy consumption of a building. In this context the optical properties of window glazing are measured to determine the percentage absorption of incident solar radiation. An experimental study was performed in a room to measure the glazing surface temperature due to the global radiation on it. The corresponding window plane global radiation and horizontal global radiation were measured outside for simulation. Mathematical models have been developed to simulate the window plane solar radiation and corresponding glazing surface temperature aiming at validating the measured values. The thermal model is concerned with laminar heat transfer for natural and forced convection process according to the ambient conditions. The estimated errors between experimental and simulated values of window plane radiation and glazing temperature are shown to be within ±5%. Using the developed thermal model the heat flow inside the room through windows is determined. Thus overall heat transfer coefficient of glazing ( U-factor) and the Solar Heat Gain (SHG) of building interior have been predicted from the simulation.