Determination Of Temperature Profiles Research Articles

Mathematical expression of the temperature profile and experimental determination of compression heating of ethylene glycol during high hydrostatic pressure processing

In this study, we aimed to describe the temperature profile in the pressure vessel and the compression heating during high hydrostatic pressure (HHP) processing. Regression coefficients (R 2), root mean square error ({RMSE}) values and residual plots suggested that fourth-order polynomial function produced reasonable fits to define the temperature profile for all the pressures studied (300–600 MPa). If all the coefficients of this empirical model are determined, initial and final temperatures, a value close to the treatment temperature and maximum temperature reached during pressurization can be obtained or calculated theoretically. Temperature increase of the pressure transmitting fluid (ethylene glycol) at different inital temperatures (−2.5 to 17.5 °C) and at the pressure range studied showed linear dependence with pressure. Maximum temperature increase (about 20 °C) was observed at 600 MPa and at initial temperatures of 14 and 17.5 °C. Minimum temperature increase (about 10 °C) was observed at 300 MPa and at initial temperatures of−2.5 and 8.5 °C. Although compression heating of ethylene glycol highly depends on the applied pressure, it was observed that it has little dependence to initial temperature.

Heat Transfer Study in a Linear Turbine Cascade Using a Thermal Boundary Layer Measurement Technique

An experimental system is designed, constructed, and operated to make local measurements of heat transfer from constant-temperature surfaces in a linear turbine cascade. The system includes a number of embedded heaters and a control system to maintain the turbine blades and end walls in the cascade at a uniform temperature. A five-axis measurement system is used to determine temperature profiles normal to the pressure and suction sides of the blades and to the end wall. Extrapolating these measurements close to the surface, the local heat transfer is calculated using Fourier’s law. The system has been tested in the laboratory, and results are shown for the temperature distributions above the surfaces and for the local variations in the Nusselt number on the different surfaces in the cascade. The system can also be used to study the heat and mass transfer analogy as considerable data are available for mass transfer results with similar geometries.

Development of spectroscopic tools for the determination of temperature and density spatial profiles in implosion cores

Two innovative spectroscopic techniques have been developed to characterize the temperature and density spatial profiles of Inertial Confinement Fusion (ICF) implosion cores. The analyses involve the emissivity ratio of Ly β/He β to extract temperature, followed by the solution of either emissivity or intensity equations based on the Ly β or He β line to infer density. In particular, the idea of solving intensity equations permits the consideration of the effects of opacity. Information on turbulent mixing of the shell material into the core can be extracted by including the optically-thick Ly α line in the intensity analysis. We focus on developing and validating these spectroscopic tools using synthetic data. Hydrodynamic simulations matching the experimental conditions are used to test the codes and to demonstrate the validity of the physical principles in our spectroscopic techniques.

Calibration of the Purple Crow Lidar vibrational Raman water-vapour mixing ratio and temperature measurements

Purple Crow Lidar (PCL) measurements of the vibrational Raman-shifted backscatter from water vapour and nitrogen molecules allows height profiles of the water-vapour mixing ratio to be measured from 500 m up into the lower stratosphere. In addition, the Raman nitrogen measurements allow the determination of temperature profiles from about 10 to 40 km altitude. However, external calibration of these measurements is necessary to compensate for instrumental effects, uncertainties in our knowledge of the relevant molecular cross sections, and atmospheric transmission. A comparison of the PCL-derived water-vapour concentration and temperature profiles with routine radiosonde measurements from Detroit and Buffalo on 37 and 141 nights, respectively, was undertaken to provide this calibration. The calibration is then applied to the measurements and monthly mean-temperature and water-vapour profiles are determined.PACS Nos.: 42.68.Wt, 42.79.Qx

Tidal associated temperature disturbances observed at the middle atmosphere (30–65 km) by a Rayleigh lidar at 23°S

A lidar has been operated in São José dos Campos, Brazil (23.2°S, 45.8°W) since 1972, mainly dedicated to the study of mesospheric sodium at the 589 nm resonant line. The molecular Rayleigh scattering can also be used provided we limit the height to ∼75 km where the sodium scattering begins. Nevertheless, the weak signal obtained only permits the determination of density and temperature profiles by accumulating a large number of shots giving only nocturnal average profiles. Temporal variations in density and temperature on the scale of hours can however, be obtained by performing a superposed epoch analysis for a given time interval and covering a period of several days. In this way we obtained hourly mean profiles grouped by months, seasons and overall, with data acquired from 1993 to 2004. The difference between the hourly temperatures and the nocturnal means shows for some months, with enough data coverage, downward propagating structures that apparently have tidal origin. The seasonal averages show a recurrent feature with high temperatures before and low temperatures after midnight above 50 km. Some similarity is found with the GSWM model, but the observed temperature amplitudes are twice of that for the model.

Determining the temporally and radially resolved temperature distribution inside a pulsed broad-area vertical-cavity surface-emitting laser cavity

The authors experimentally determine temporally and radially resolved profiles of the temperature distribution within the cavity of a broad-area vertical-cavity surface-emitting laser in pulsed operation. For this, the recently discovered state of spatially incoherent emission [M. Peeters et al., Opt. Express 13, 9337 (2005)] is harnessed. Using single-shot measurements of spectrally resolved near field profiles acquired by a fast-gated charge coupled device camera, the wavelength shift due to heating of the device is temporally and radially resolved. From the wavelength shift the temperature shift is extracted, which finally allows for determination of absolute temperature profiles.

The Bonn University lidar at the Esrange: technical description and capabilities for atmospheric research

Abstract. The Bonn University operates a Rayleigh/Mie/Raman backscatter lidar at the Esrange near the Swedish city of Kiruna, north of the Arctic circle. The lidar system covers the atmosphere from about 4 km to 100 km altitude and it is capable of measuring aerosols in the tropo-, strato-, and mesosphere, as well as of determining temperature profiles in the aerosol-free part of the atmosphere (i.e. above 30-km altitude). Density tuned fixed-spacer etalons provide daylight capability and thus increased sensitivity to noctilucent clouds during polar summer. Polarisation measurements allow liquid and solid phase discrimination for aerosol and cloud particles in the tropo- and stratosphere. The derived temperature profiles can be used for the detection and analysis of atmospheric gravity waves. Although several lidar experiments are situated in polar latitudes, a comprehensive instrument which covers the troposphere, stratosphere, and mesosphere, is daylight capable, and observes temperature profiles, as well as aerosols, is exceptional. In this article a technical description, in particular, of the optical configuration of this experiment is given, as well as an overview of achievable geophysical parameters. The potential for geophysical analyses is shown. Keywords. Atmospheric composition and structure (Instruments and techniques; Aerosols and particles; Pressure, density and temperature) – Meteorology and atmospheric dynamics (Middle atmosphere dynamics)

An XMM-Newton view of the cluster of galaxies Abell 85

We have observed the cluster of galaxies Abell 85 with XMM-Newton. These data have allowed us to confirm in a previous paper the existence of the extended 4 Mpc filament detected by the ROSAT PSPC in the neighbourhood of this cluster, and to determine an X-ray temperature of about about 2 keV. We now present a thorough analysis of the properties of the X-ray gas in the cluster itself, including temperature and metallicity maps for the entire cluster. These results show that Abell 85 had intense merging activity in the past and is not fully relaxed, even in the central region. We have also determined the individual abundances for some iron-group metals and alpha-elements in various regions; the ratios of these metallicities to the iron abundance show that both supernova types Ia and II must be involved in the intra-cluster gas enrichment. Spectral analysis of the central region suggests a different redshift of the X-ray emitting gas compared to the mean cluster velocity derived from galaxy member redshifts. We discuss the implications of the difference between the cD galaxy redshift, the mean galaxy redshift and the hot gas redshift, as well as the possibility of several groups being accreted on to Abell 85. Finally, we obtain the dynamical mass profile and baryon fraction taking into account the new determined temperature profile. The dynamical mass in Abell 85 has a steep density profile, similar to the ones found in N-body simulations.

OPTIMAL CONTROL OF DISPERSIVE TUBULAR CHEMICAL REACTORS: PART I

This paper, the first of a series of two, deals with the determination of optimal steady-state jacket fluid temperature profiles for dispersive tubular chemical reactors, ranging from plug flow to perfectly mixed reactors. According to Pontryagin's minimum principle, the optimal control is of the bang-bang type for the proposed terminal cost criterion. The bang-bang switching position is numerically optimised, by means of a weighted shooting-type procedure for the determination of the reactor profiles, ensuring the Danckwerts boundary conditions are satisfied. Following this procedure the impact of dispersion on the optimised profiles is illustrated. In the second paper, the performance of the obtained optimal control laws will be compared with that of practically more feasible controls. Furthermore, the transient behaviour will be assessed.

Determination of heat transfer rates in an industry-like spray quench system using multiple impinging water jets

Liquid jet impingement (LJI) cooling is widely employed in quench systems, the majority of which utilise multiple impinging jets. Successful design and operation of such systems require accurate data of actual heat transfer rates. The present study is concerned with the determination of heat transfer rates during rapid cooling of high temperature surfaces using multiple impinging water jets (MIWJs) in an industry-like arrangement. The effects of jet variables have been investigated. Heat transfer coefficients have been numerically calculated using inverse analysis, utilising experimentally determined temperature profiles. Comparison with heat transfer rates of immersion quenching has been considered. The present study provides important information about heat transfer rates in an industry-like water spray quench system using MIWJs. Results demonstrated that the use of MIWJs offers significant flexibility in controlling cooling rates, which renders this technique most suitable for quench operations requiring wide range of cooling rates.

XMM-Newtonobservation of the relaxed cluster A478: Gas and dark matter distribution from 0.01R$_\mathsf{200}$ to 0.5R$\mathsf{_{200}}$

We present an XMM-Newton mosaic observation of the hot (kT ∼ 6.5 keV) and nearby (z = 0.0881) relaxed cluster of galaxies A478. We derive precise gas density, gas temperature, gas mass and total mass profiles up to 12 � (about half of the virial radius R200). The gas density profile is highly peaked towards the center and the surface brightness profile is well fitted by a sum of three β-models. The derived gas density profile is in excellent agreement, both in shape and in normalization, with the published Chandra density profile (measured within 5 � of the center). Projection and PSF effects on the temperature profile determination are thoroughly investigated. The derived radial temperature structure is as expected for a cluster hosting a cooling core, with a strong negative gradient at the cluster center. The temperature rises from ∼2 keV up to a plateau of ∼6.5 keV beyond 2 � (i.e. r > 208 kpc = 0.1R200, R200 = 2.08 Mpc being the virial radius). From the temperature profile and the density profile and on the hypothesis of hydrostatic equilibrium, we derived the total mass profile of A478 down to 0.01 and up to 0.5 times the virial radius. We tested different dark matter models against the observed mass profile. The Navarro et al. (1997) model is significantly preferred to other models. It leads to a total mass of M200 = 1.1 × 10 15 Mfor a concentration parameter of c = 4.2 ± 0.4. The gas mass fraction increases slightly with radius. The gas mass fraction at a density contrast of δ = 2500 is fgas = 0.13 ± 0.02, consistent with previous results on similar hot and massive clusters. We confirm the excess of absorption in the direction of A478. The derived absorbing column density exceeds the 21 cm measurement by a factor of ∼2, this excess extending well beyond the cool core region. Through the study of this absorbing component and a cross correlation with infrared data, we argue that the absorption excess is of Galactic origin, rather than intrinsic to the cluster.

Multispectral imaging of continuum emission for determination of temperature and density profiles inside implosion plasmas

In inertial confinement fusion experiments, implosion of a cryogenic hydrogen isotope-filled capsule produces a plasma with a high-temperature, low-density core (the hot spot) surrounded by a low-temperature, high-density main fuel layer. Experimental measurements of temperature and density profiles in the hot spot are critical for implosion diagnosis. In this paper, we propose a simple technique for measuring core temperature and density profiles in cryogenic implosion plasmas. This technique uses absolutely calibrated continuum emission spectroscopy coupled with two-dimensional imaging to allow temperature and density profiles to be measured directly. We develop the technique analytically, and validate it using synthetic data and hydrodynamics simulation results. We find that the technique should be sufficiently accurate to measure central temperatures and densities to better than 20%. The technique may also find application to the diagnosis of other types of plasmas.

Heat transfer process simulation by finite differences for online control of ladle furnaces

A numerical method for solving the two-dimensional transient heat conduction equation is presented to determine temperature profiles of ladle furnaces during the casting of special steels. The method is based on an explicit formulation of the heat transfer process in finite differences. In order to improve the efficiency of the method, two auxiliary algorithms are added, one for correcting finite difference results from coarse mesh calculations and the other to perform time extrapolation of the temperature behaviour between furnace batches. The calculated steel temperatures are found to be in good agreement with experimental data, obtained at a Brazilian thin steel casting facility. Currently, about 80% of the ladle batches at this facility come out within their commercial specifications, against 45% previously observed without the use of such a model. With average processing times of the order of 100 s in an AMD K6II 300 MHz computer, the method is suitable for real time thermal tracking of ladles and steel.

Numerical analysis of an optical method to determine temperature profiles in hot glassmelts

In the present study a technique is developed to determine temperature profiles in hot glassmelts, using intensity measurements performed at various wavelengths in the infraredspectrum. To that end an analytical model is developed which describes the internal energytransfer in a glass layer and the spectral intensity emerging from the glass layer. Thespectral intensity so calculated is confronted with a measured spectral intensity toreconstruct the temperature profile in the glass layer. Because the temperaturereconstruction from the measured spectral intensity is an ill posed inverse problem,Tikhonov regularization and the L-curve method are used to determine a meaningfultemperature distribution in the glass layer. In order to gain insight into the accuracyof the temperature measurement method a sensitivity analysis is made usingnumerical simulations. The influence of random noise on the measurement signal andsystematic errors in the properties is investigated. Furthermore, the temperaturereconstruction of linear, logarithmic and parabolic temperature distributions is analysed.

Revision of TV Thomson scattering data analysis and detection of profile structure

The determination of electron temperature and density profiles with high resolution Thomson Scattering is reconsidered, focusing on the correct treatment of the statistics and error estimation. Based on this, methods are proposed to decide whether spatial structures observed in the measured profiles are significant. A detailed statistical analysis of the detection process is given. It is shown that a maximum likelihood method must be used to fit the theoretical scattering spectra to the data, in order to obtain electron temperature and density. Furthermore, an existing calibration procedure for the detector, based exclusively on the statistics of the detected scattering image, is perfected. This self-consistent analysis leads to a precise definition of the confidence limits. Based on these, statistical tests are designed to determine whether structures seen on the Thomson scattering profiles are significant or not. To test the statistical method, some TEXTOR discharges were analyzed.

Dependence of the stability of semi-implicit atmospheric models on reference temperature profile

The linear stability of three-time-level finite-difference semi-implicit schemes is studied for hydrostatic atmospheric models with viscosity terms. The main objective is the investigation of stability dependence on choice of reference temperature profile. Characteristic equation for amplification factor is derived in the case of simplified baroclinic atmospheric numerical model, keeping the implicit approximation for the basic temperature profile and explicit approximation for its deviations. Analytical solutions for amplification factor are found in some special cases and computational experiments are performed for different values of model parameters, such as vertical discretization (number of levels and its distribution), temperature profile (basic and actual), and time step. The influence of the viscosity terms on scheme stability is also studied. Performed analysis confirms two main results obtained numerically in other models: instability generated by inappropriate determination of temperature profile is absolute and computational stability can be recovered if the basic reference profile is chosen to be warmer than the actual one.

Temperature profile determination from microwave oxygen emissions in limb sounding geometry

We present a theoretical investigation of the temperature profile retrieval capabilities of oxygen emission lines in the microwave. The main focus is on two strong lines, both allowing temperature retrieval throughout the mesosphere. One is within the oxygen cluster at 61.15 GHz, the other one is isolated at 118.75 GHz. A thorough comparison of these two lines is presented. Several instrumental parameters such as system noise temperature, antenna beam width, filter width, and coverage of the line are assessed, as well as the possible impact of an error in the spectroscopic parameters. The instrumental setup follows roughly the specifications for the Millimeter Wave Acquisitions for Stratosphere/Troposphere Exchange Research (MASTER) instrument, serving as a basis for a modern passive microwave instrument. The instrumental parameters have also been varied in order to allow comparisons with two instruments that use the 118.75‐GHz line for temperature profile determination, the Odin submillimeter radiameter (SMR) and the EOS microwave limb sounder (MLS). Simultaneous retrieval of temperature and pointing bias is performed with the Optimal Estimation Method. We find temperature retrieval errors of <5 K in the mesosphere, and at sub‐Kelvin level in the lower stratosphere. Good knowledge of spectroscopic parameters is required for accurate retrievals. The simultaneous retrieval of a pointing bias can reduce the impact of spectroscopic parameter errors on the temperature retrieval.

Perturbation techniques for accelerated convergence of cyclic steady state (CSS) in oxygen VSA simulations

Non-isothermal PSA bulk gas separations are notoriously slow to converge to cyclic steady state (CSS). Most numerical simulators that model the slow transient behaviour of these processes share this slow pace of convergence. This difficulty with numerical simulators has long been recognised, and has hampered the optimisation of oxygen VSA. This paper outlines the application of perturbation techniques to enable more rapid determination of CSS temperature profiles. A number of different techniques are proposed. The simplest approach based on experimental observations involves a two-time-scale decomposition of the adsorbent temperature profile. This decomposition of the temperature term enables the rapid numerical determination of the fast (or adsorptive) component of the temperature, followed by the direct determination of an estimated cyclic steady-state slow time-scale (or convective) temperature. It is demonstrated that this approach is the same as a zeroth-order multiple scale analysis (MSA) approach and a simple application of the Krylov–Bogoliubov (K–B) method of averaging. This study compares the results of this acceleration technique for determining CSS with a full numerical model. The results indicate that the proposed acceleration technique based on perturbation methods provides fast and reasonable estimates of the CSS temperature profile with some limitations. Recognising these limitations of the zeroth-order approach, a first-order MSA is developed. This compares better with full numerical simulations, and could be used to augment and complement existing acceleration techniques. It is shown that a first-order MSA approach can also be used to capture the dynamic temperature response of the oxygen VSA process, in addition to the CSS axial temperature profile. The perturbation techniques presented here are limited to a series expansion of the temperature term in the energy balance, and mass balance is ignored in this analysis. A procedure is outlined where a K–B approach can be used to incorporate a perturbation series expansion in the mass balance. We show that these perturbation techniques not only offer potential for simulation acceleration, but also offer useful insights into the thermal convergence to CSS in oxygen VSA.

Multifrequency radiometric determination of temperature profiles in a lossy homogeneous phantom using a dual-mode antenna with integral water bolus

In the treatment of cancer, microwave hyperthermia has been established as an efficient adjunctive procedure to radiation therapy and chemotherapy. Wider acceptance of this method awaits schemes to measure volumetric temperatures noninvasively in human tissue for control of the heating process. This effort describes the design and performance of a new microstrip applicator intended for homogeneous heating of superficial tissue while at the same time monitoring temperature of the underlying tissue by noninvasive radiometric sensing of black-body radiation from the heated volume. Radiometric capabilities are assessed in terms of accuracy of up to six measured brightness temperatures applied in an inversion algorithm from which one-dimensional depth temperature profiles are generated. Based on radiometric signals recorded over the 1-4-GHz range, the temperature accuracy determined from statistical analysis of 200 realizations of the process is better than /spl plusmn/0.2/spl deg/C to a depth of 5 cm in phantom. Aperture heating uniformity is assessed with electric field scans in a homogeneous muscle phantom. As long as sufficiently thin (< 5 mm) water boli are used, SAR distributions at 1-cm depth in phantom extends effectively just outside the aperture perimeter, making this microstrip antenna an excellent building block element of larger multi-antenna array applicators.

Experimental and simulation studies of heat flow and heterocyclic amine mutagen/carcinogen formation in pan-fried meat patties

Heterocylic amine (HA) compounds formed in the cooking of certain foods have been shown to be bacterial mutagens and animal carcinogens, and may be a risk factor for human cancer. To help explain the variation observed in HA formation under different cooking conditions, we have performed heat-flow simulations and experiments on the pan-frying of beef patties. The simulations involve modeling the heat flow within a meat patty using empirically derived thermal transport coefficients for the meat. The predicted temperature profiles are used to integrate the Arrhenius rate equation to estimate the concentration of HAs formed in the meat. We find that our simulations accurately model experimentally determined temperature profiles, cooking times, HA spatial distributions and total HA formation in patties that are flipped once during the pan-frying process. For patties flipped every 60 s, the simulations qualitatively agree with experiment in predicting reduced cooking times and HA formation relative to the singly-flipped patties. However, the simulations overestimate the effect of rapid flipping on cooking times and underestimate the effect of flipping on total HAs formed. These results suggest that the dramatic reductions in HA formation due to rapid flipping may be due to factors other than the heating process or that there is a critical feature of the flipping process that is not captured in our model.