Determination Of Temperature Profiles Research Articles

Synthetic helium beam diagnostic and underlying atomic data

We report on synthetic helium beam emission spectroscopy (BES) in fusion edge plasmas, as enabled by the 3D kinetic (neutral particle) transport code EIRENE. We also review and upgrade the underlying atomic helium data base, resorting to the most recent version of the Goto–Fujimoto collisional-radiative code and a recommended and publicly exposed reference cross section data set from an internationally coordinated (IAEA) evaluation activity. On the example of the Wendelstein 7-X (W7-X) stellarator, we use both the upgraded transport code and data base to simulate the penetration of and radiation from thermal helium used for BES in the island divertor region. This allows to evaluate the applicability of the diagnostic in different plasma backgrounds, simulated with the 3D edge plasma Monte Carlo code EMC3-EIRENE, and with different levels of refinement of underlying atomic data. The sensitivity of the diagnostic to the atomic data set—which is crucial for a quantitative determination of electron density and temperature profiles—is investigated and discussed, as well as the effects of p-He beam widening and correlated line-of-sight integration.

Dry Reforming of Methane at High Pressure in a Fixed-Bed Reactor with Axial Temperature Profile Determination

A continuously operated flow setup with fixed-bed reactor and online gas analysis enabled kinetic investigations of catalysts for the carbon dioxide reforming of methane under industrially relevant conditions at temperatures up to 1000 °C and at pressures up to 20 bar. A coaxial reactor design consisting of an inner- and an outer highly alloyed steel tube allowed obtaining axial temperature profiles by means of a moveable thermocouple. A NiAl2O4-based catalyst was tested at 820 °C and pressures of 1, 10 or 20 bar and compared to a conventional Ni catalyst used for steam reforming of methane. A significant cold spot was detected even when using only 10 mg of catalysts diluted in 1 g of silicon carbide. The specifically designed NiAl2O4/Al2O3 dry reforming catalyst with a high dispersion of the active Ni0 phase was found to be far superior to the conventional steam reforming catalyst.

Investigation of masking concepts for influencing the austenitization process during press hardening

One possibility to adjust tailored properties in hot stamping is the application of a masking concept to prevent a complete austenitization. In this study different concepts were investigated in order to use them as a suitable masking. A simulation model of the heating phase was developed for the purpose of predicting the resulting microstructure and hardness. Experimentally determined temperature profiles were used for the numerical model. The numerical results of the temperature profile and hardness were validated by experimental investigations and non-destructive hardness measurements. The simulated hardness is in adequate agreement with the measured hardness.

Infrared absorption spectrometer for the determination of temperature and species profiles in an entrained flow gasifier.

An absorption spectrometer utilizing a tunable distributed feedback diode laser at 2.3μm and an interband cascade laser at 3.1μm has been developed to measure temperature and concentrations of CO, CH4, C2H2, and H2O under gasification conditions. A wavelength division multiplexing approach using a single ZrF4-fiber was used to measure both wavelength regions simultaneously. The performance of the spectrometer has been tested in laminar flat flames and a heated cell and then applied for measurements at an atmospheric entrained flow gasifier (REGA). A water-cooled optical probe was used to provide optical access at two measurement positions. By moving the burner, axial profiles of temperature and species concentration could be obtained. These profiles were compared with numerical simulations and can be used to validate the simulation.

An analysis of the numerical model influence on the ground temperature profile determination

The estimation of the ground temperature profile with respect to the depth and time is the key issue in many engineering applications which use the ground as a source of thermal energy. In the present work, the influence of the model components on the calculated ground temperature distribution has been analysed in order to develop an accurate and robust model for the prediction of the ground temperature profile. The presented mathematical model takes into account all the key phenomena occurring in the soil and on its top surface. The impact of individual model elements on the temperature of the soil has been analysed. It has been found that the simplest models and the most complex model result in a similar temperature variation over the simulation period, but only at a low depth. A detailed analysis shows that a larger depth requires more complex models and the calculation with the use of simple models results in an incorrect temperature and a theoretical COP estimation.

Ferromagnetic particles as magnetic resonance imaging temperature sensors.

Magnetic resonance imaging is an important technique for identifying different types of tissues in a body or spatial information about composite materials. Because temperature is a fundamental parameter reflecting the biological status of the body and individual tissues, it would be helpful to have temperature maps superimposed on spatial maps. Here we show that small ferromagnetic particles with a strong temperature-dependent magnetization, can be used to produce temperature-dependent images in magnetic resonance imaging with an accuracy of about 1 °C. This technique, when further developed, could be used to identify inflammation or tumours, or to obtain spatial maps of temperature in various medical interventional procedures such as hyperthermia and thermal ablation. This method could also be used to determine temperature profiles inside nonmetallic composite materials.

Determination of equivalent circulating density of drilling fluids in deepwater drilling

Evaluation of bottom-hole pressure is a critical concern for high-pressure/high temperature (HP/HT) and deepwater drilling operations. Accurate determination of drilling fluid temperature and pressure is a key step for the prediction of fluid density. A simulator was developed to calculate the wellbore temperature and pressure during circulation and static conditions. The simulation includes effects of various operational parameters, such as rate of penetration, fluid loss as well as pump rate schedules. The mathematical model of heat transfer was developed for a deviated offshore well profile to make the algorithm flexible for different applications. The upwind numerical discretization scheme is used for determination of temperature profile. The temperature prediction of the model was verified with available analytical models for a vertical onshore well. The hydraulic model employs the yield power-law rheology model. The local density of drilling fluid as a function of temperature and pressure is evaluated using the available PVT correlations. It is shown that when mud circulation stops, the equivalent static density slightly increases with time. The results of simulation also indicate that during circulation, a higher equivalent circulating density is expected as compared to the case of constant fluid density. The results of the developed method are compared with downhole temperature and pressure data in an offshore well. The comparison indicates that the developed model has a good accuracy to track the bottom-hole circulating temperature and pressure. The proposed method can be integrated into various parts of a drilling simulator such as hydraulic design, wellbore stability and well control.

Determination of effective axial temperature profile in tube furnaces via the Viscous Stretching Method

We present an efficient approach to determine the axial temperature profile in tube furnaces by analyzing the diameter profile after stretching from a silica glass rod. Given the temporal load for stretching, the effective axial temperature profile can be deduced. This approach neglects diameter change due to surface tension by using rods. It also considers homogeneous cross sectional temperatures as effective axial temperatures. Since the effective temperature is derived from the rod’s viscous behavior, it yields optimized temperature profiles for heat treatment with glass rods, such as all-solid fiber drawing. This provides better temperature profiles than using thermal couples, because they are measured by the glass rods from the working material. Silica glass was used in this approach for its well-studied viscosity-temperature relationship. The derived method was carried out in an inductive graphite furnace under argon flow at 1400 °C and 1800 °C, respectively. The results will be validated by the mean of saphire fiber Bragg grating sensor measurements. Finally, the problems of the stretched axis and spatial resolution will be discussed.

Flameless compact combustion system for burning hydrous ethanol

Environmental concerns and uncertainties in oil supply motivate the development of new combustion technologies using biofuels. Flameless combustion is a promising technology capable of operating with high thermal efficiency, reduced pollutant emissions and low operational costs. This work presents an experimental study of a flameless compact combustion system for burning hydrous ethanol, 96% v/v using a blurry injector to atomize the fuel. Relatively uniform sprays with small droplets and narrow cone angles were obtained, favoring the operation of the flameless combustor. The flameless combustion regime was observed under several operational conditions, through the determination of temperature profiles and flue–gas composition. For a 2 kW thermal input, the flameless regime occurred with excess air coefficients 1.65–2.45, temperatures 690–921 °C, NOx emissions 2.55–3.08 ppm and UHC (unburned hydrocarbons) emissions 1.43–1.10 ppm. For a 4 kW thermal input, the flameless regime occurred with excess air coefficients 1.21–1.80, temperatures 810–1002 °C, NOx emissions 1.98–2.16 ppm and UHC emissions 1.53–2.25 ppm. The temperature profiles measured during the flameless regime were relatively homogeneous inside the combustion chamber with very low emissions, compared to the conventional flame regime.

A Mathematical Model for the Exhaust Gas Temperature Profile of a Diesel Engine

This work presents a heat transfer model for the exhaust gas of a diesel power generator to determine the gas temperature profile in the exhaust pipe. The numerical methodology to solve the mathematical model was developed using a finite difference method approach for energy equation resolution and determination of temperature profiles considering turbulent fluid flow and variable fluid properties. The simulation was carried out for engine operation under loads from 0 kW to 40 kW. The model was compared with results obtained using the multidimensional Ansys CFX software, which was applied to solve the governor equations of turbulent fluid flow. The results for the temperature profiles in the exhaust pipe show a good proximity between the mathematical model developed and the multidimensional software.

A new modeling approach for improved ground temperature profile determination

The knowledge of the ground temperature profile with respect to time and depth is very important in many technological fields like geothermal heat pumps, solar energy systems and geotechnical applications. Many researches were performed in the past in order to evaluate this profile. The most common ones, known as energy balance models, use the energy balance equation as a boundary condition. Unfortunately the performance of these models strongly depends on an accurate estimation of several input factors. The objective of this paper is to develop an improved model for the prediction of the ground temperature profile in which the energy balance equation at the ground surface is supplemented by an empirical correlation for the annual average ground surface temperature calculation. This model is less sensitive to uncertainties of input factors. Furthermore, unlike the previous models, a periodic variation of the sky temperature is introduced instead of a previously assumed constant value. The model is validated against measured data in a site located in Varennes (Montreal-Canada) and two further sites, Fort Collins (Colorado) and Temple (Texas) in the U.S.A.

Numerical and experimental determination of in-structure temperature profiles

Abstract When building physics simulations are done initial conditions express the actual hygrothermal state of building envelope. For the temperature field simulations initial condition is represented by the initial temperature in the body profile at the start of heat transfer. In-structure temperature varies quickly so temperature initial conditions are often neglected. Nevertheless in specific cases initial conditions have to be taken into an account even when simple temperature field simulations are done. The contribution shows various temperature initial conditions determination for insulated construction of outdoor test cell. Comparison of measured and calculated temperature profiles in structure shows correctness of start-up pre-calculation initial condition consideration

Investigation of pillow-plate condensers for the application in distillation columns

Pillow-plate heat exchangers represent a new promising concept which can be, among others, used in distillation as integrated top-condensers. Today, their application in process industries is growing. Pillow-plate condensers were investigated using two experimental set-ups at the University of Paderborn (lab scale) and at Bayer Technology Services GmbH (pilot scale). Condensation experiments at pilot scale were performed using a non-conventional fibre-optic measurement technique for the determination of the condensation channel axial temperature profiles. Cooling-side heat transfer coefficients and pressure drop values were obtained based on the lab-scale measurements and numerical simulations (CFD). These results were compared to calculated values for virtual plain tube bundles. Measured axial temperature profiles as well as the overall and condensation-side heat transfer coefficients are presented. This allows a comparison of the obtained results with conventional geometries.

Retrieving cloudy atmosphere parameters from RPG-HATPRO radiometer data

An algorithm for simultaneously determining both tropospheric temperature and humidity profiles and cloud liquid water content from ground-based measurements of microwave radiation is presented. A special feature of this algorithm is that it combines different types of measurements and different a priori information on the sought parameters. The features of its use in processing RPG-HATPRO radiometer data obtained in the course of atmospheric remote sensing experiments carried out by specialists from the Faculty of Physics of St. Petersburg State University are discussed. The results of a comparison of both temperature and humidity profiles obtained using a ground-based microwave remote sensing method with those obtained from radiosonde data are analyzed. It is shown that this combined algorithm is comparable (in accuracy) to the classical method of statistical regularization in determining temperature profiles; however, this algorithm demonstrates better accuracy (when compared to the method of statistical regularization) in determining humidity profiles.

On axial temperature gradients due to large pressure drops in dense fluid chromatography

The effect of energy degradation (Degradation is the creation of net entropy resulting from irreversibility.) accompanying pressure drops across chromatographic columns is examined with regard to explaining axial temperature gradients in both high performance liquid chromatography (HPLC) and supercritical fluid chromatography (SFC). The observed effects of warming and cooling can be explained equally well in the language of thermodynamics or fluid dynamics. The necessary equivalence of these treatments is reviewed here to show the legitimacy of using whichever one supports the simpler determination of features of interest. The determination of temperature profiles in columns by direct application of the laws of thermodynamics is somewhat simpler than applying them indirectly by solving the Navier–Stokes (NS) equations. Both disciplines show that the preferred strategy for minimizing the reduction in peak quality caused by temperature gradients is to operate columns as nearly adiabatically as possible (i.e. as Joule–Thomson expansions). This useful fact, however, is not widely familiar or appreciated in the chromatography community due to some misunderstanding of the meaning of certain terms and expressions used in these disciplines. In fluid dynamics, the terms “resistive heating” or “frictional heating” have been widely used as synonyms for the dissipation function, Φ, in the NS energy equation. These terms have been widely used by chromatographers as well, but often misinterpreted as due to friction between the mobile phase and the column packing, when in fact Φ describes the increase in entropy of the system (dissipation, ∫TdSuniv>0) due to the irreversible decompression of the mobile phase. Two distinctly different contributions to the irreversibility are identified; (1) ΔSext, viscous dissipation of work done by the external surroundings driving the flow (the pump) contributing to its warming, and (2) ΔSint, entropy change accompanying decompression of fluid in the column, contributing either to warming or cooling depending on local density and temperature. The molecular basis for this variation is described. Sample calculations of dissipation and temperature profiles of several model fluids including carbon dioxide-methanol mixtures are presented, based on the NIST REFPROP program including select equations of state and property calculation software.

An Investigation on Temperature Distribution and Cooling Rate of ERW Pipes during TIG Welding

AbstractThe present investigation deals with the determination of temperature profile and subsequent rates of cooling at certain points on the external surface along axis of an ERW pipe, during TIG welding. Two samples of different diameters of pipes of ASTM A 106 Gr. B, seamless type are selected for experimentation. The temperatures on the external surface at different locations on each of these seamless pipes (of different diameters) during welding have been measured with the help of digital pyrometers. The temperature variation along the axis of pipe from the weld arc has been presented. Thereafter, through separate analytical methods the temperature distribution across the external surface of the pipe for a given point heat source is theoretically calculated, and the results are compared with the previously found experimental values of temperatures. They are found to be well in agreement. Further, the rates of cooling of a pre-selected point on the pipe surface are experimentally and analytically determined under varying welding conditions and are compared likewise and are found to be in good agreement too.

Self-consistent determination of the ion thermalization rate at the plasma boundary of TJ-II by the supersonic He beam diagnostic

A method for measuring the thermalization rate of He ions injected into the edge of a magnetically confined plasma, free from calibration and photon-to-ion ratio uncertainties, has been deduced for the first time. He+ ions are introduced into a plasma boundary by means of a supersonic He beam and the radial distribution of neutral He and He+ emissions along the beam propagation path through the plasma is analysed. The new technique allows for the determination of local ion temperature profiles in non-rotating edge plasmas if the impurity composition at the edge is known, thus extending the application of the He beam diagnostic to Ti edge profile measurements. Methods to disentangle rotation and thermalization losses are also proposed, thus further extending the technique to plasma rotation measurements near the last closed flux surface.

Analytical Method of Temperature Prediction in Reinforced Concrete Beams

The determination of temperature profile within a reinforced concrete (RC) beam is essential for carrying out structural analysis at elevated temperatures. The temperatures are usually estimated using sophisticated numerical techniques which require computational support. Since the determination of rebar temperature in RC beams is more important than the concrete temperature a reliable analytical method of temperature prediction can become a helpful tool in simple beam analysis problems which are employed for determining residual strength in fire. This paper presents the details of development of an empirical equation for the prediction of temperature of rebar in RC beams. The equation is also capable of predicting concrete temperatures at different locations within the beam. The predictions made by the equation were compared with the temperatures determined from experimental beam testing and finite element (FE) analysis. A good correlation of the predicted temperatures was found for the entire time-temperature history with both the observed data and the estimated temperatures by FE models.

Model‐based estimation of optimal temperature profile during simultaneous saccharification and fermentation of Arundo donax

A kinetic model fitted to enzymatic hydrolysis of Arundo donax was coupled to a fermentation kinetic model derived from simultaneous saccharification and fermentation (SSF) experiments at different temperatures for the determination of optimal temperature profile (between 36 and 45°C) using iterative dynamic programming (IDP). A sensitivity analysis of enzyme kinetic model not only facilitated model reduction in terms of number of parameters, but also enabled artifacts from parameter estimations to be identified. In separate fermentation experiments conducted at 35, 40, 45, and 50°C using ∼40 g/L background glucose in fiber-free liquid fraction of Arundo it was found that growth was possible at 40°C, but the fermentation capacity was completely lost after 12 h at 50°C. The final ethanol concentration obtained after 120 h in isothermal SSF experiments at 36, 39, 42, and 45°C were 10.6, 13.7, 14.2, and 12.5 g/L, respectively. The predicted optimal temperature profile in SSF determined by iterative dynamic programming was (i) gradual decrease from 40 to 37.5°C until 16 h, (ii) a linear increase upto 45°C until 80 h, and (iii) gradual decrease by 1°C until 120 h. Experimental results were in good agreement with the model predictions. The ethanol concentration after 72 h obtained in the optimal case was 13.6 g/L in comparison to 9.1, 12.2, 12.6, and 11.6 g/L for ISO-SSF at 36, 39, 42, and 45°C, respectively. Moreover this value was 95.8% of the final value achieved at the end of 120 h, indicating that the process times could be significantly shortened by using non-isothermal SSF.

A Finite Element Analysis of Temperature Profiles and Cooling Rates of ERW Pipes during TIG Welding

AbstractThe present investigation deals with the determination of temperature profile and subsequent cooling rates of certain points on the external surface of an ERW pipe with the help of ANSYS Finite Element Modeling and Analysis method, under simulated TIG welding conditions. A TIG welding condition for an ERW pipe is first simulated through ANSYS Finite Element Modeling. The physical and material properties along with the dimensions and size of the ERW pipe are all included in the modeling part. The TIG welding arc is simulated as a point heat source of a given power traversing the periphery of the pipe surface during welding. In the ANSYS program, after modeling the TIG welding problem, the same is run in the post – processing analysis part to get the temperature profile along the external surface of the pipe at various time intervals from the start of the welding. The rate of cooling of a few particular nodes on the modeled pipe surface, from the start of welding to the completion of one welding pass is also studied and results are indicated in graphical form. Later, these cooling rates on the modeled pipe surface are compared with those of an exactly similar ERW pipe, physically welded by TIG welding method in the workshop under similar welding conditions and welding parameters.