Estimation Of Temperature Profiles Research Articles

Use of high-resolution measurements for the retrieval of temperature and gas-concentration profiles from outgoing infrared spectra in the presence of cirrus clouds

We explore ways in which high-spectral-resolution measurements can aid in the retrieval of atmospheric temperature and gas-concentration profiles from outgoing infrared spectra when optically thin cirrus clouds are present. Simulated outgoing spectra that contain cirrus are fitted with spectra that do not contain cirrus, and the residuals are examined. For those lines with weighting functions that peak near the same altitude as the thin cirrus, unique features are observed in the residuals. These unique features are highly sensitive to the resolution of the instrumental line shape. For thin cirrus these residual features are narrow (< or = 0.1 cm(-1)), so high spectral resolution is required for unambiguous observation. The magnitudes of these unique features are larger than the noise of modern instruments. The sensitivities of these features to cloud height and cloud optical depth are also discussed. Our sensitivity studies show that, when the errors in the estimation of temperature profiles are not large, the dominant contribution to the residuals is the misinterpretation of cirrus. An analysis that focuses on information content is also presented. An understanding of the magnitude of the effect and of its dependence on spectral resolution as well as on spectral region is important for retrieving spacecraft data and for the design of future infrared instruments for forecasting weather and monitoring greenhouse gases.

Estimation of temperature profiles in microwaved particulates using enzyme and vision system

A new method, which used enzyme (peroxidase) as a time–temperature indicator (TTI) and color vision system to detect enzyme concentration was developed in this study. Peroxidase was immobilized in particulates containing potato starch and alginate. The particulates were heated in a microwave generation and transmission system from 15 to 85 s at 5 s intervals. The enzyme concentration was assayed by a color reaction, and detected by a color vision system. The temperature profiles of particulate foods heated in the microwave cavity were obtained through the calculation based on the results of changes in enzyme concentration. A z-value of 34.5°C and D ref of 1.62 s at reference temperature of 121.1°C were obtained. Matching the results of temperature measurements with a fiber optic probe validated the temperatures estimated by this new method. Furthermore, the color vision system adequately provided the temperature distribution within the particulates including heating time. Therefore, the temperature of particulates could be calculated at any location and heating time.

LPCVD silicon nitride uniformity improvement using adaptive real-time temperature control

An effective approach to improve silicon nitride thickness uniformity has been demonstrated on a batch LPCVD furnace platform. Implementation of adaptive real-time temperature control provides accurate, real-time estimation of substrate temperature profiles that enables model-based optimization of process temperature. Optimization of a 200-nm silicon nitride deposition yielded long-term, overall nitride thickness uniformity of 0.79% 1/spl sigma/ over a seven-week period, compared to 1.24% for an equivalent PID-tuned process. Three sequential silicon nitride deposition iterations were implemented in the process recipe to enable increased temperature ramp rates for more efficient optimization of within-wafer uniformity. The optimized process requalified quickly after major and minor equipment maintenance, and is suitable for use in a manufacturing environment. The ART-optimized temperature ramp intervals used in this study are comparable to temperature deltas often used to offset dichlorosilane depletion effects encountered in some large-batch vertical furnace depositions. SIMS depth profiling of ART-optimized silicon nitride does reveal small oxygen and chlorine peaks, indicating slight interface formation between deposition steps.

APPROXIMATE MODEL OF THERMAL RESIDUAL STRESS IN AN INJECTION MOLDED PART

A description and model of the thermally induced residual stress that forms in a ''platelike'' injected molded polymer part is outlined. A linear heat balance integral (LHBI) temperature profile approximation and the concept of a virtual adjunct mold (VAM) is used to arrive at an approximate algebraic model that, upon providing material properties and processing conditions, gives an immediate evaluation of the residual stress through the plate thickness. Results obtained with this model are in very close agreement with a full numerical solution and agree closely with experimental measurements made on a range of starch-based biodegradable polymer samples.

Influence of turbulent fluctuation on reconstruction of temperature profile in axisymmetric free flames

An iteration method is extended to analyze the influences of the turbulent fluctuation on the reconstruction of Reynolds time-averaged temperature in turbulent axisymmetric free flames when the temperature profiles are retrieved by the low time-resolution data of outgoing emission and transmission radiation intensities. A simplified probability density function is used to simulate the turbulent fluctuation of temperature and absorption coefficient. The effects of turbulent fluctuating intensities on the estimation of the Reynolds time-averaged temperature and absorption coefficient are examined. The results show that the effects of turbulent fluctuation on the reconstruction of time-averaged absorption coefficient are not significant. In the case of weak turbulent fluctuation, the influences of turbulent fluctuation on the estimation of time-averaged temperature profiles are small. But in the case of strong turbulent fluctuation, the influences of turbulent fluctuation on the estimation of time-averaged temperature profiles are significant.

Non-invasive temperature profile estimation in a lossy medium based on multi-band radiometric signals sensed by a microwave dual-purpose body-contacting antenna

Microwave radiometry has during the past two decades been investigated as a non-invasive scheme for measurement of subcutaneous tissue temperatures, basically for monitoring and control in hyperthermic treatment of cancer. In this effort, we test a contact-type, dual-purpose antenna with integral water bolus. To overcome conflicting optimization criteria in the integration of this thermometry technique with heat applicators exhibiting a large effective field size during superficial hyperthermia, a stacked configuration design is proposed, where the radiometer receive antenna (Archimedean spiral) is located on the front (skin) surface of the water bolus and the heating antenna (Dual-Concentric Conductor aperture) is placed on the bolus back surface. The motivation is to achieve homogeneous tissue heating simultaneously with non-invasive thermography of the target tissue under the applicator. This paper addresses the feasibility of predicting one-dimensional depth temperature profiles from multi-band brightness temperatures. The performance is investigated statistically by a Monte Carlo technique on both simulated and real heated-phantom data using up to six radiometric bands. Analysis of measured data shows that during the transient heating period in a solid lossy phantom, the inversion technique exhibits a precision (2 † T ) and skewness (bias) of estimated compared to actual temperature profiles of better than - 0.38°C and - 0.55°C, respectively.

Methodology for estimation of time-dependent surface heat flux due to cryogen spray cooling.

Cryogen spray cooling (CSC) is an effective technique to protect the epidermis during cutaneous laser therapies. Spraying a cryogen onto the skin surface creates a time-varying heat flux, effectively cooling the skin during and following the cryogen spurt. In previous studies mathematical models were developed to predict the human skin temperature profiles during the cryogen spraying time. However, no studies have accounted for the additional cooling due to residual cryogen left on the skin surface following the spurt termination. We formulate and solve an inverse heat conduction (IHC) problem to predict the time-varying surface heat flux both during and following a cryogen spurt. The IHC formulation uses measured temperature profiles from within a medium to estimate the surface heat flux. We implement a one-dimensional sequential function specification method (SFSM) to estimate the surface heat flux from internal temperatures measured within an in vitro model in response to a cryogen spurt. Solution accuracy and experimental errors are examined using simulated temperature data. Heat flux following spurt termination appears substantial; however, it is less than that during the spraying time. The estimated time-varying heat flux can subsequently be used in forward heat conduction models to estimate temperature profiles in skin during and following a cryogen spurt and predict appropriate timing for onset of the laser pulse.

Foundation heat loss from heated concrete slab-on-grade floors

In recent years, there has been a renewed interest in heated concrete slab floors to provide for space heating in both residential and commercial buildings. The existing design procedures for these heating systems are based on simplified thermal models with several assumptions. In particular, the simplified models assume that both the upper and the lower concrete slab surface are isothermal and that the heat transfer through the bottom of the slab surfaces is uniformly distributed over the entire surface. In this paper, a more realistic and flexible model for heated or cooled concrete slab floors is considered to determine the heat transfer between the concrete slab and the ground. In particular, steady-state and steady-periodic semi-analytical solutions are developed to determine the temperature field within the ground medium and within the concrete slab-on-grade floor where hot or chilled water pipes are embedded. The solution presented in this paper is applied to determine the ground heat loss/gain for a heated or cooled floor under various design conditions including the level of floor insulation, and the temperature of the water pipes. These solutions are obtained using the interzone temperature profile estimation (ITPE) procedure. Detailed analysis is presented to determine the effect of the slab insulation configuration on soil and slab temperature field and on the monthly variation of the total slab heat loss.

Measurement of interfacial temperatures during testing of a subscale aircraft brake

Interfacial temperatures have been measured using fibre opticinserts in the stationary brake ring during ring-on-ring, subscaledynamometer aircraft brake testing. The brake materials are carbonfibre-reinforced, carbon-matrix (carbon-carbon) composites. Thetemperature distribution varies with dynamometer test conditions anddemonstrates the non-uniformity of contact pressure within the interface.A two-dimensional, axis-symmetric finite element model (FEM) is presentedthat is used to estimate temperature profiles during braking using eithera constant pressure or constant energy flux assumption. The modelincorporates the measured temperature-dependence of the thermaldiffusivity and specific heat capacity for the composite materials. Thesurface temperatures obtained from the FEM are compared with the measuredsurface temperatures. Substantial differences between the two results areobserved and discussed.

Reverse flow reactor at short switching periods for VOC combustion

A medium-scale reverse flow reactor for VOC combustion is investigated in the stationary and long-term transient states. Heat loss and dilution by fresh air at the core of the reactor are accounted for. A simple linear dynamic model allows estimating temperature profiles at stationary state, and temperature dynamics in the transient state when VOC concentration varies. The extinction limit is also simply estimated. Heat loss and dilution are found to be a crucial phenomena and their effects on the characteristic time of the temperature response are established. Conversely, these phenomena do not seem to affect the extinction limit.

On the effects of the temperature profile approximation in thermal Newtonian solutions of elastohydrodynamic lubrication line contacts

The assumptions of a quadratic temperature profile and mean viscosity across the film, which are frequently used in the analysis of thermal elastohydrodynamic lubrication (EHL), are examined and discussed. Two different approaches for solving the thermal EHL problem are compared for line contact conditions, namely (a) a one-dimensional model based upon both the assumption of a quadratic temperature profile and the adoption of the mean physical properties across the film and (b) a two-dimensional model which includes changes in temperature and physical properties of a lubricant across the film and which takes into account the conditions of reverse flow and heat convection across the film occurring at the inlet region. A multi-grid algorithm is implemented to solve these two conditions. The temperature profile and the general solutions in the conjunction obtained in both approaches are compared. For the one-dimensional model, results reveal that temperature peaks just prior to the inlet of the conjunction. This feature is not apparent in the two-dimensional model and results in lower values in film thickness and larger frictional coefficients than in the two-dimensional model. In the high-pressure region, both equations yield almost the same mean temperature.

Steady-State Component of Three-Dimensional Slab-on-Grade Foundation Heat Transfer

General semi-analytical solutions for the steady-state heat conduction problems for circular and three-dimensional rectangular slab-on-grade floors with uniform insulation are presented. The soil temperature field, and the total slab heat loss are presented and analyzed using the Interzone Temperature Profile Estimation (ITPE) technique. A parametric analysis is conducted to determine the effect of thermal insulation U-value, slab size, and water table depth on the total slab heat loss. In particular, it was found that the total slab heat loss is independent of its shape but is strongly affected by the slab size and thermal characteristics.

Thermally optimal insulation distribution for underground structures

This paper provides an analytical solution of the optimal distribution of thermal insulation along the surfaces of underground structures to minimize the annual heat transfer through the ground-coupled surfaces. The analytical solution is obtained using the Interzone Temperature Profile Estimation (ITPE) technique. Two underground structures are considered in this paper: a fully earth-sheltered structure and a partially bermed structure with a shaft that opens to an above-grade interior space. The results of a parametric analysis are summarized to determine the effects of the amount of heat flux imposed on each surface on the optimum insulation distribution along the underground surfaces.

Simultaneous identification of temperature profile and absorption coefficient in one-dimensional semitransparent medium by inverse radiation analysis

An inverse analysis is presented for simultaneous estimation of temperature profile and absorption coefficient for an absorbing, emitting, non-scattering, gray, one-dimensional semitransparent slab with transparent boundaries from the knowledge of the exit radiation intensities at boundary surfaces. The inverse problem is formulated as an optimization problem and solved by using a mixed method of the conjugate gradient method and the one-dimensional search method. The effects of the measurement errors on the accuracy of the inverse analysis are investigated. The study shows that the temperature profile and the absorption coefficient can be estimated accurately, even with noisy data.

An approach to the selection of optimal sensor locations in distributed parameter systems

This paper presents an approach to the selection of optimal sensor locations in distributed parameter systems, which distinguishes the purposes of state estimation from the purposes of parameter estimation. In the first case, the optimality criterion is based on a measure of independence between the sensor responses, while in the second case, it is based on a measure of independence between the parameter sensitivity functions. The procedure, which is general and can be applied to models with any degree of complexity, is illustrated with the optimal placement of temperature sensors in a catalytic fixed-bed reactor. Some numerical results for the on-line estimation of temperature and concentration profiles as well as for the estimation of unknown model parameters are discussed.

Thermal, physico-chemical and rheological boundary layers in multi-component oxidic melt spreads

In the unlikely case of a severe accident in a nuclear reactor, the core material could melt and form a molten mixture named corium. The CEA has undertaken a large program to improve knowledge on corium behaviour. An experiment in which 17 kg of simulant corium — mainly made of hafnon, zircon, silica and wüstite — at more than 2 200 K, was spread in the VULCANO facility, is described. It is analysed in terms of thermal cooling by fitting the pyrometric measurements with outputs of a conduction code. This enables the estimation of temperature profiles inside the corium. From physicochemical modelling, the solid fraction, density and viscosity can be estimated. Thermal, physicochemical and rheological boundary layers are thus found. The rheological boundary layer is very steep (exponential decay parameter around 800 m −1) and could significantly affect the flow dynamics. A visible aspect of this boundary layer is the presence of folds on the corium surface, similar to those on ropy pahoehoe lavas.

Flow visualization and residual microstructures associated with the friction-stir welding of 2024 aluminum to 6061 aluminum

The friction-stir welding (FSW) of 0.6 cm plates of 2024 Al (140 HV) to 6061 Al (100 HV) is characterized by residual, equiaxed grains within the weld zone having average sizes ranging from 1 to 15 μm, exhibiting grain growth from dynamically recrystallized grains which provide a mechanism for superplastic flow; producing intercalated, lamellar-like flow patterns. These flow patterns are visualized by differential etching of the 2024 Al producing contrast relative to 6061 Al. The flow patterns are observed to be complex spirals and vortex-like, among others, and to change somewhat systematically with tool rotation (stirring) speed between 400 and 1200 rpm; depending on tool orientation. The equiaxed grain and sub-grain microstructures are observed to vary according to estimated temperature profiles (varying from 0.6 to 0.8 T M , where T M is the absolute melting temperature) referenced to the rotating tool axis. Dislocation spirals and loops are also observed in the 2024 Al intercalation regions within the weld zones at higher speeds (>800 rpm) corresponding to slightly elevated temperatures introducing dislocation climb, and residual microhardness profiles follow microstructural variations which result in a 40% reduction in the 6061 Al workpiece microhardness and a 50% reduction in the 2024 Al workpiece microhardness just outside the FSW zone.

An inverse method for estimation of the initial temperature profile and its evolution in polymer processing

An inversion technique is developed to reconstruct the temperature distribution over the thickness of a part during polymer processing using the surface temperature measurement. The algorithm is validated using surface temperature data generated numerically from a number of theoretical temperature profiles developed during polymer flows. The technique is then applied to the injection stretch blow molding process. In this process a preform is injection molded, stretched to its final length and then inflated. A single stage AOKI machine is used for the experiments. An infrared camera is employed to measure the surface temperature of the preform with time after it is taken out of the injection mold. The initial temperature distribution in the preform and its temperature evolution before stretching and inflation are predicted.

Estimation of concentration and temperature profiles for methane-steam reforming reaction in a porous catalyst

This work represents the results of the theoretical study of the distribution of concentration and temperature in porous catalyst, carried out over spherical catalyst pellets for the methane-steam reforming reaction over Ni/MgAl 2O 4 catalyst. Kinetic information has been taken from a recent study [J. Xu, F.G. Froment, AIChE J. (35) (1989) 88–96] for the above reaction. The mass and heat transfer distribution coupled with chemical reaction, outside and within the catalyst particles for methane-steam reforming reaction was estimated in this present study. A computer program was written to calculate both concentration profile and temperature profile for the methane-steam reforming reaction.

Model for temperature profile estimation in the refractory of a metallurgical ladle

Modeling of the transient thermal state of metallurgical ladels is motivated by the need for estimating the drop in temperature of the liquid metal in the ladle. On-line estimation of the state is required, since the same ladle is used in a number of casting cycles with rapid changes in boundary conditions for the temperature field, and the conditions in the current as well as previous cycles affect the thermal state. Although a large number of methods for the numerical solution of conduction-diffusion partial differential equations have been developed, there are still advantages to keeping thermal field computations at a relatively simple level, in contrast to the situation in the design process of ladles, where two-dimensional modeling may be required. Extensive computations under nonverifiable boundary and initial parameter values are not especially suited for real-time simulation of industrial processes. This article presents a novel approach to the solution of the one-dimensional transient heat conduction problem applied to ladle linings, relying on classical analytical techniques in combination with numerical methods. The performance of the model was validated by a comparison of predictions to thermocouple measurements from the refractory of a steelmaking ladle during a campaign of 26 casting cycles. Reasonable agreement between the measured and simulated variables could be established, which demonstrates the feasibility of the approach.