Prediction Of Thermal Behavior Research Articles

Newspaper sandwiched aerated lightweight concrete wall panels—Thermal inertia, transient thermal behavior and surface temperature prediction

Experimental investigation on aerated lightweight concrete (ALC) wall panels in terms of thermal inertia, transient thermal behavior and surface temperature prediction using finite difference method (FDM) are the main focus of this study. ALC wall panels of different density and different aerial intensity of newspaper sandwiched were produced and installed on a prototype house. The ALC wall panels were facing east direction and subjected to Malaysia natural environment condition. The inner and outer surface temperatures of the wall panels were recorded at 3 min interval, 24 h a day for a period of one year. Time lag and decrement factor were computed from the surface temperatures recorded. The results showed that thermal diffusivity has a positive relationship to the thermal inertia of ALC wall panels. FDM was used to predict the surfaces temperature and the predicted temperature was close to the observed temperature. The average differences between the observed and the predicted outer wall surface temperature lied between 1.4 and 2.4% whereas for the inner wall surface, the range was 1.3–2.2%. Greater deviations were detected on the predicted outer surface temperature could be due to some unaccounted factors such as wind direction and relative humidity in the present FDM.

Numerical simulation of cooling energy consumption in connection with thermostat operation mode and comfort requirements for the Athens buildings

A model and a corresponding numerical procedure, based on the finite-difference method, have been developed for the prediction of buildings thermal behavior under the influence of all possible thermal loads and the “guidance” of cooling control system in conjunction with thermal comfort requirements. Using the developed procedure analyses have been conducted concerning the effects of thermostat operation mode and cooling power in terms of the time, on the total cooling energy consumption for the ideal space cooling, as well as for various usually encountered real cases, thus trying to find ways to reduce cooling energy consumption. The results lead to suggestions for energy savings up to 10%. Extensive comparisons between the ideal and various real cooling modes showed small differences in the 24-h cooling energy consumption. Because of the above finding, our detailed ideal cooling mode predictions gain considerable value and can be considered as a basis for comparison with real cases. They may also provide a good estimate of energy savings obtained if we decide to increase thermostat set point temperature. Therefore, as the extent of cooling energy saving is a priori known, one can decide if (and how much) it is worthy to increase thermostat set point temperature at the expense of thermal comfort. All results of the study, which refer to the Typical Athens Buildings during the typical Athens summer day, under the usual ranges of thermal loads, may be applicable to other regions with similar conditions.

Transient Heat Transfer Model for Car Body Primer Curing

� Abstract—A transient heat transfer mathematical model for the prediction of temperature distribution in the car body during primer baking has been developed by considering the thermal radiation and convection in the furnace chamber and transient heat conduction governing equations in the car framework. The car cockpit is considered like a structure with six flat plates, four vertical plates representing the car doors and the rear and front panels. The other two flat plates are the car roof and floor. The transient heat conduction in each flat plate is modeled by the lumped capacitance method. Comparison with the experimental data shows that the heat transfer model works well for the prediction of thermal behavior of the car body in the curing furnace, with deviations below 5%.

Effective Approach to Characterization of Prediction Errors for Balloon Ascent Trajectories

In order to comply with the objectives of a balloon mission, it is usually necessary to predict, monitor and track the flight trajectory. Within the framework of the Unmanned Space Vehicles program, the Italian Aerospace Research Center has developed several methodologies and tools useful to evaluate balloon mission feasibility, predict balloon flight trajectory and assess trajectory prediction errors. These methodologies are based on weather forecast data for trajectory computation obtained using the Integrated Forecast System model by the European Center for Medium Range Weather Forecast and on the use of a proprietary simulation software for the prediction of flight trajectory and thermal behavior of high altitude zero-pressure balloons. In this paper, we propose an effective approach for the characterization of trajectory prediction error based on: statistical characterization of the forecast error of the Integrated Forecast System atmospheric data (winds, temperature and pressure), statistical characterization of the error on gas mass due to inflation procedures and analytical error propagation of these sources of uncertainties on the balloon’s velocity vector. The proposed approach allows to estimate the actual trajectory dispersion once the predicted trajectory is computed using forecast data. The methodology proposed in this paper is an improvement of the trajectory prediction methodology that has been successfully used during the first Dropped Transonic Flight Test mission accomplished by Italian Aerospace Research Center.

Thermal behavior of selected Czech marble samples

The definition as well as prediction of rock thermal behavior seems to be a quite difficult problem significantly effected by rock composition and structure. Temperature increase causes various changes of rock material (such as decomposition, oxidation, phase and polymorphic transformation, etc.). These changes are connected to thermal expansion with following appearance of tensions and cracks in minerals and rock structure. After consequential temperature decrease, developed tensions and cracks still influence the process. This study presents the application of thermogravimetric analysis, differential thermal analysis and thermomechanical analysis in characterization of selected marble thermal behavior. The texture and morphological orientation of calcite grains for marble samples was determined by optical microscopy. FTIR spectroscopy application along with X-ray diffraction (XRD) extended data about mineralogical composition. According to optical microscopy, the calcite grains show marked morphological anisotropy in one direction for some samples. Therefore, the thermal expansion had to be measured in three different (perpendicular to each other) directions. It is evident, that the effect of temperature on the final marble properties depends not only on mineralogical composition, but also on structure, texture and morphological orientation of grains. All these facts significantly influence the interpretation of differences in various marble thermal behavior.

Thermal behaviour prediction utilizing artificial neural networks for an open office

This study investigates a neural network-based non-linear autoregressive model with external inputs (NNARX), a non-linear autoregressive moving average model with external inputs (NNARMAX), and a non-linear output error model (NNOE) to predict the thermal behaviour of an open-plan office in a modern commercial building. External and internal climate data recorded over one summer, autumn and winter season were used to build and validate the models. The paper illustrates the potential of using these models to predict room temperature and relative humidity for different time scales ahead (30 min or 2 h ahead). The prediction performance is evaluated using the criteria of goodness of fit, coefficient of determination, mean absolute error and mean squared error between predicted model output and real measurements. To obtain an optimal network structure (avoiding overfitting) after training, a pruning algorithm called optimal brain surgeon (OBS) was used to remove unnecessary input signals, weights and hidden neurons. The results demonstrate that all models provide reasonably good predictions but the NNARX and NNARMAX models outperform the NNOE model. These models can all potentially be used for improving the performance of thermal environment control systems.

Thermal hydraulic behavior in the deteriorated turbulent heat transfer regime for a gas-cooled reactor

One of the key issues in a gas-cooled system with a passive heat removal measure is the correct prediction of thermal hydraulic behavior in the deteriorated turbulent heat transfer (DTHT) regime. Here, a simple one-dimensional analysis of a gas-cooled reactor system was performed to show its strong potential for operation in the DTHT regime. A numerical calculation using computational fluid dynamics (CFD) was done to verify the capability of the Launder–Sharma (LS) turbulence model to predict wall and bulk temperatures while a gas system is operating in the DTHT regime. The results by the LS model are compared to those by the high Reynolds turbulent model, a newly proposed correlation, and recently obtained experimental data. The comparison shows that the LS turbulence model can provide a reasonable prediction in the buoyancy-induced DTHT regime. Additionally, it was found that the LS model predicted strong laminarization near the entrance which deteriorated turbulent heat transfer further compared to the measurements, but re-turbulization took place much earlier than in the experiment which recovered the heat transfer to a normal turbulent heat transfer.

Effect of biomass leaching on H2 production, ash and tar behavior during high temperature steam gasification (HTSG) process

Abstract The effect of biomass water leaching on H 2 production, as well as, prediction of ash thermal behavior and formation of biomass tar during high temperature steam gasification (HTSG) of olive kernel is the main aim of the present work. Within this study raw olive kernel samples (OK 1 , OK 2 ) and a pre-treated one by water leaching (LOK 2 ) were examined with regard to their ash fouling propensity and tar concentration in the gaseous phase. Two temperatures ( T = 850 and 950 °C) and a constant steam to biomass ratio ( S / B = 1.28) were chosen in order to perform the steam gasification experiments. Results indicated that considering the samples' ash thermal behavior, it seemed that water leaching improved the fusibility behavior of olive kernel; however, it proved that water leaching does not favour tar steam reforming, while at the same time decreases the H 2 yield in gas product under air gasification conditions, due to possible loss of the catalytic effect of ash with water leaching.

Method for Prediction and Optimization of a Stratospheric Balloon Ascent Trajectory

DOI: 10.2514/1.39469 In this paper, we propose a methodology for the prediction and optimization of the ascent trajectory of a stratospheric balloon to target a specified three-dimensional area. The methodology relies mainly on the Analysis Code for High-Altitude Balloons, a simulation tool for the prediction of flight trajectory and thermal behavior of high-altitude,zero-pressureballoons,andonastatisticalanalysisforestimatingthetrajectorypredictionerrors.The paperalsodescribesthealgorithmsusedforballoonparameteroptimizationtoobtaina flighttrajectorythatreaches apredefinedtargetareawithoutanyballastdroporgasventingcontrol.Theproposedmethodologywassuccessfully used during the first Dropped Transonic Flight Test of the Flying Test Bed 1 demonstrator accomplished on 24February2007bytheItalianAerospaceResearchCenter.Thereportedpostflightanalysisofallthetestcampaign demonstratesthattheproposedmethodologyfortrajectorypredictionandoptimizationguaranteesverysatisfactory and reliable results for both the selection of the best day to perform such a mission and the definition of the correct balloon parameters to be used for targeting a predefined three-dimensional area.

Thermal models for copper-alloyed dies in pressure die casting

A recent innovation in pressure die casting is the use of copper-alloyed dies suitably protected with a thermally sprayed steel layer. The thermal response of copper-alloyed dies is dictated principally by the deposited layer, the cooling arrangement and the casting geometry. This paper is concerned with the development of efficient numerical models for the prediction of both steady-state and transient thermal behaviour of the new die designs. Die temperatures are cyclic but useful information is obtained from a steady-state model, which provides for time-averaged temperatures and energy fluxes. The modelling strategy presented in the paper involves the indirect determination of transient temperatures. A perturbation approach is adopted, where a model for the difference between transient and steady-state temperature is developed. It is shown that this approach can be utilised to determine transient temperature efficiently once steady-state information is available with the transient perturbation model only involving surfaces where a significant variation in temperature occurs. The die-thermal models are founded on the boundary element method as die surface temperatures are of primary importance in pressure die casting. The finite element method is used to model casting solidification, where the formulation adopted provides for accurate energy transport. The dies form a multi-domain environment for thermal predictions making it necessary to utilise a suitably constructed coarse preconditioner to enhance numerical stability and provide for efficient computation. A multiplicative Schwarz method is presented that enables a parameter matrix accelerated GMRES method to be applied on each domain. Numerical experiments are performed to demonstrate the computational effectiveness of the approach. Predicted temperatures are compared with thermocouple readings obtained from a copper–steel die on a commercial die casting machine.

A heat transfer model for the analysis of transient heating of the slab in a direct-fired walking beam type reheating furnace

A mathematical heat transfer model for the prediction of heat flux on the slab surface and temperature distribution in the slab has been developed by considering the thermal radiation in the furnace chamber and transient heat conduction governing equations in the slab, respectively. The furnace is modeled as radiating medium with spatially varying temperature and constant absorption coefficient. The steel slabs are moved on the next fixed beam by the walking beam after being heated up through the non-firing, charging, preheating, heating, and soaking zones in the furnace. Radiative heat flux calculated from the radiative heat exchange within the furnace modeled using the FVM by considering the effect of furnace wall, slab, and combustion gases is introduced as the boundary condition of the transient conduction equation of the slab. Heat transfer characteristics and temperature behavior of the slab is investigated by changing such parameters as absorption coefficient and emissivity of the slab. Comparison with the experimental work show that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace.

Thermal Stability Testing of Refractory Specimen

Abstract The most important properties usually measured for refractories are working temperature and thermal stability. Thermal stability of the alumina based samples was measured using standard laboratory procedure, water quench test (JUS.B.D.8.319). The ImagePro Plus program was used for image analysis of deterioration monitoring of the samples before, during, and after water quench test. Mechanical characteristics were considered such as strength, dynamic modulus of elasticity resulting from resonance frequency measurements, as well as ultrasonic velocity. In this work correlation between deterioration, ultrasonic vtelosity, and strength on thermal stability of the samples were investigated. The results were used for validation of the model for the thermal stability behavior prediction of the refractory.

가열로 내 슬랩의 온도 예측을 위한 2차원 열전달 모델

A mathematical heat transfer model for the prediction of heat flux on the slab surface and temperature distribution in the slab has been developed by considering the thermal radiation in the furnace and transient conduction governing equations in the slab, respectively. The furnace is modeled as radiating medium with spatially varying temperature and constant absorption coefficient. The slab is moved with constant speed through non-firing, charging, preheating, heating, and soaking zones in the furnace. Radiative heat flux which is calculated from the radiative heat exchange within the furnace modeled using the FVM by considering the effect of furnace wall, slab, and combustion gases is applied as the boundary condition of the transient conduction equation of the slab. Heat transfer characteristics and temperature behavior of the slab is investigated by changing such parameters as absorption coefficient and emissivity of the slab. Comparison with the experimental work shows that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace.

RENAL CRYOABLATION AND RADIO FREQUENCY ABLATION: AN EVALUATION OF WORST CASE SCENARIOS IN A PORCINE MODEL

Although ablative technologies, including radio frequency (RF) ablation (RFA) and cryoablation (CA), are being used to treat renal masses, complications associated with injury to vital renal structures are not well understood. We investigated these worst case scenarios by deliberately targeting vital renal structures with CA or RFA in a porcine model. Following surgical exposure of the right kidney in female pigs a cryoneedle or an RF probe was deliberately placed under visual and ultrasound guidance in the renal pelvis (CA in 5 pigs and RFA in 7), major calix (CA and RFA in 5 each) or subsegmental renal vessels (CA in 5 pigs and RFA in 7). Cryo-energy or RF energy was then applied to create a 3 cm lesion. After 10 days the kidneys underwent gross and histological examination for urine and blood extravasation, cell death and injury. Ex vivo retrograde pyelography was performed to evaluate for urinary fistulas. All pigs tolerated the treatment and no procedure related deaths occurred. No significant bleeding was noted. RFA and CA created reproducible lesions and areas of cell death and necrosis. Despite significant intentional injury to the collecting system no urinary fistulas were demonstrated in CA specimens (0 of 15). In contrast, damage to the renal pelvis (4 of 7) by dry (3 of 4) or wet (1 of 3) RFA was associated with a high likelihood of urinary extravasation. This short-term study demonstrates that CA is safe, effective and not associated with urinary extravasation. In contrast, RFA to the renal pelvis is associated with urinary extravasation. Further studies are needed to support these findings.

Kinetics of thermal decomposition of unsaturated polyester resins with reduced flammability

AbstractIn this article, the kinetics of thermal decomposition of unsaturated maleic–phthalic polyester resins, flame‐retarded with zinc hydroxystannate, was studied by thermogravimetric analysis at different heating rates. At the first stage, it was found, on the basis of isoconversional analysis by the methods of Friedman and of Ozawa–Flynn–Wall, that the value of the (apparent) activation energy (E) characteristically changes in three steps during the degradation. Further kinetic studies using nonlinear regression methods revealed the best fits for both pristine and stabilized resins. It was observed that the course of E versus the degree of conversion (α) during degradation of zinc hydroxystannate‐containing resins (α > 0.8) was characterized by higher values of E—this phenomenon can be explained in terms of the flame‐retardation action of zinc hydroxystannate, which is believed to operate primarily in the condensed phase. At the next stage, kinetic analysis by the nonregression method was performed to find the kinetic model [f(α) function] of the decomposition process; hence, for pristine resin, the best fit was found for the Avrami–Yerofeeyev model (nuclei growth), and for stabilized samples, the nth‐order function with catalysis proved to be the best approximation. The obtained kinetic parameters in the form of E, the preexponential factor A, and the model function f(α) allow a prediction of the polyester resin's thermal behavior in an extrapolated range of degree of conversion, time, and temperature. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2851–2857, 2003

Thermal Periodic Contact of Exhaust Valves

Internal combustion engines generate exhaust gases at extremely high temperatures and pressures. As these heated gases exit through the exhaust valve, the valve and valve seat insert achieve comparable temperatures. To avoid damage, heat is transferred from the exhaust valve to the valve seat insert as they come into contact with each other during the opening and closing cycle. Modern engine management systems regulate the thermal process through coolant and/or airflow rates, fuel injection, and ignition timing, and exhaust gas recirculation contributions to achieve satisfactory tradeoffs between power, emissions, and efficiency for various engine speeds and loads. One of the primary functions of the engine control unit is the prevention and detection of abnormal combustion to prevent severe engine damage. The online estimation of cylinder component temperatures offers an opportunity for greater engine control measures. A nonlinear dynamic thermal model is presented to describe the transient and steady-state phenomena in the engine's cylinder using a lumped parameter resistance-capacitance network. The model prediction of the engine's thermal behavior establishes a foundation to explore thermal periodic contact issues. Representative experimental and numerical results will be presented and discussed.

On approaches to couple energy simulation and computational fluid dynamics programs

Energy simulation (ES) and computational fluid dynamics (CFD) can play an important role in building design by providing complementary information of the building performance. However, separate applications of ES and CFD usually cannot give an accurate prediction of building thermal and flow behavior due to the assumptions used in the applications. An integration of ES and CFD can eliminate many of these assumptions, since the information provided by ES and CFD is complementary. This paper describes some efficient approaches to integrate ES and CFD, such as static and dynamic coupling strategies, in order to bridge the discontinuities of time-scale, spatial resolution and computing speed between ES and CFD programs. This investigation further demonstrates some of the strategies through two examples by using the EnergyPlus and MIT-CFD programs.

Measurement and prediction of thermal behaviour and assessment of injury in a pig model of renal cryosurgery

Measurement and prediction of thermal behaviour and assessment of injury in a pig model of renal cryosurgery

A Finite Element Model for the Prediction of Thermal and Metallurgical Behavior of Strip on Run-out-table in Hot Rolling.

A finite element-based, integrated process model is presented for a three dimensional, coupled analysis of the thermal and metallurgical behavior of the strip occurring on the run-out-table in hot strip rolling. The validity of the proposed model is examined through comparison with thermal measurements. The model's capability of revealing the effect of diverse process parameters is demonstrated through a series of process simulation.

Prediction of long-term thermal behavior of an irradiated SRAM based on isochronal annealing measurements

In the present paper, the methodology to predict the long-term isothermal annealing of irradiated devices from a single isochronal curve is applied for the first time on devices as complex as commercial SRAMs; moreover, the behavior of the devices was monitored using both an electric and a functional test by respectively measuring the power supply current and the number of bit failed. In both cases, the experimental isothermal and isochronal annealing curves show direct correlates between the electrical parameters and the function of the device. Moreover, from the single experimental isochronal curve, the long-term isothermal behavior of the device is predicted and compared with the experimental isothermal curve using both the parametrical and functional characterizations. In both cases the predicted long-term thermal behaviors are in good agreement with the experimental results.