Basis Of Temperature Measurements Research Articles

Identification of aerothermal heating for thermal protection systems taking into account the thermal resistance between layers

In this paper the aerothermal heating of a reusable launch vehicle is reconstructed on the basis of temperature measurements taken in the thermal protection system of this vehicle. The discussed integrated thermal protection system is composed of three layers. Mathematical model, describing the problem, takes into account the dependence on temperature of the material parameters as well as the thermal resistances occurring in the contact zones of the layers, which is a novelty in the proposed approach. For solving the direct problem, the implicit scheme of the finite difference method is applied. Next, by using the solution of the direct problem, the Tikhonov functional is created, which describes the error of the current approximate solution. Whereas for determining the solution of the inverse problem the Levenberg-Marquardt method, modified and adapted to the Tikhonov functional, is used. The paper presents the mathematical model of the problem and the method of solution together with the selected examples illustrating its exactness and stability. In order to better examination of the solution method some various values of parameters are taken in the demonstrated examples.

Simplified Method of Determination of the Sound Speed in Water on the Basis of Temperature Measurements and Salinity Prediction for Shallow Water Bathymetry

The aim of this paper is to present a method of determining sound speed in water, based on temperature measurements executed by means of a laboratory low-cost thermometer with a probe provided with a long cable. It has been assumed that the salinity variation in respect to depth, found in a shallow water area, has insignificant impact on the sound velocity distribution determined by the temperature changes. The salinity data were obtained via the Internet service from the closest measuring station that registers surface water parameters. The sound speed in water was determined based on the formulas widely adopted in hydroacoustics and compared with the results obtained from the measurements executed by means of a Conductivity/Salinity Temperature Depth (CTD/STD) probe. The impact of inaccuracy in determining the sound speed in respect to the SingleBeam EchoSounder (SBES) immersion depth, i.e., a method commonly used by unmanned surface vessels in seaport measurements, was estimated. The measurements were taken in water areas of the Baltic Sea of low salinity and then verified with measurements in the Mediterranean Sea representing quite high salinity. The method is an alternative for calibrating the SBES the bar check way and has the capacity to meet the requirements in respect to its application in hydrographic surveys.

Recovery of thermal load parameters by means of the Monte Carlo method with fixed and meshless random walks

The paper is focused on the numerical analysis of the two-point inverse stationary heat flow problem, namely the identification of the thermal load. Determination of selected parameters is possible on the basis of temperature measurements, done at specified few locations. This problem may be modelled as the optimization problem, standard numerical analysis of which requires multiple solutions of boundary value problems. However, the novel solution approach, proposed here, is based on the well-known concept of the Monte Carlo method with an appropriate random walk technique. It yields explicit stochastic relations combining computed temperatures and all load parameters. Such relations may be directly applied in most standard optimization algorithms, replacing time-consuming solutions of systems of algebraic equations. Moreover, one may construct the semi-analytical approach, in which the unknown load parameters are obtained explicitly, allowing for the elimination of sensitiveness to initial solutions or requirements for admissible load intervals. The paper is illustrated with results of several benchmark problems with simulated measurement data and various numbers of unknown load parameters. The results comparison, between standard element-free methods with selected optimization algorithms as well as the proposed Monte Carlo solution approach is presented and is especially focused on CPU times.

An Evaluation of Combustion Kinetics for the Synthesis Reaction of the Reinforcing Phase During Casting Phase During Casting

The computer modeling of the solidification process in castings with local composite reinforcement (LCR) obtained as a result of in situ reactions of self-propagating high temperature synthesis (SHS) is difficult due to limited data on the thermo-physical parameters of exothermic effects and the kinetics of the synthesis reaction. In the present study, Hadfield cast steel casting was manufactured with LCR containing titanium carbide particles obtained in situ by the SHS method. Reaction kinetics of titanium carbide synthesis in the composite casting were determined on the basis of temperature measurements in the area of LCR during the process. For the estimation of the reaction, the Fourier Thermal Analysis method was used. The paper presents the results of temperature measurement and the results of the calculation of SHS reaction kinetics. It was found that the reaction time under the conditions of the analyzed casting is below 3 s.

Application of the Swarm Intelligence Algorithm for Reconstructing the Cooling Conditions of Steel Ingot Continuous Casting

This paper presents a proposal to apply one of the swarm intelligence algorithms, the artificial bee colony (ABC) algorithm, to solve the inverse problem of steel ingot continuous casting. The discussed task consists of retrieving the cooling conditions of the process on the basis of temperature measurements and by taking into account the macrosegregation phenomenon. The examined process was modeled by using the mathematical model of solidification within the temperature interval. The solution method was based on the implicit scheme of the finite difference method supplemented by the procedure of correcting the field of temperature in the vicinity of liquidus and solidus curves, which was then used for solving the appropriate direct problem. The computational example, illustrating the stability and accuracy of the proposed method, is also presented in the paper.

Determination and validation of transient temperature fields within a cylindrical element using the inverse heat conduction method

The article aims to determine and experimentally validate the transient temperature fields in a cylindrical component. The applied in-house algorithm, which is based on the inverse heat conduction method, is solved by means of the finite volume method. On the basis of temperature measurements on the outer surface of the element, the algorithm enables thermomechanical analysis of the element. In order to perform experimental validation of the algorithm, the existing laboratory set-up was modernized. During the experiment, the thick-walled steam manifold was heated up rapidly with dry saturated steam. To reconstruct the unsteady temperature distribution within the element, 19 thermocouples were used and 3 thermocouples were inserted inside the wall of the element. The 3 thermocouple locations correspond with nodal positions in the numerical algorithm, thus allowingvalidation of the unstable temperature fields. The analysis of the time-step selection and of the influence of the accidental temperature measurement error on the accuracy of the solution have also been analyzed. Moreover, the algorithm has been validated based on the analytical method. The algorithm does not require knowledge of the boundary conditions on the element’s barely accessible internal surface – a highly valued feature in industrial applications.

Интегральная модель и численный метод определения температуры при линейном теплопереносе

The work deals with the measurement problem associated with the problem of determining the temperature inside the object exposed to external heat. At each point of the surface, the thermal effect is the same and only changes over time. In this case, the temperature measurement problem has the form of a heat transfer problem in a linear object, one end of which corresponds to a point on the surface of the body, and the other end corresponds to the internal control point. The initial data of the problem are formed on the basis of temperature measurements near the object surface. In this recearsh, the problem of heat transfer is reduced to an integral model using the direct and inverse Laplace transform. The obtained integral equation is a Volterra equation of the first kind and characterizes the direct dependence of the unknown temperature functions at the control point on the initial data. To construct a numerical solution of an integral equation that is stable with respect to the error of the initial data, a computational scheme based on a regularizing approach including a multipara-meter algorithm is proposed. In order to obtain experimental estimates of the errors of the solutions to the measurement problem, a computational experiment was carried out on the basis of simulation modeling. During the experiment, the values of temperature functions at the control point of the object were determined and, on the basis of the obtained boundary functions, the temperature values were found at the internal points of the object. Also, in the course of the experiment, a comparative analysis of the temperature functions found in the test point with test values was performed. The results of the computational experiment are presented in the work and testify to the sufficient accuracy of the proposed computational method for determining the temperature during linear heat transfer.

The heat transfer coefficient determination with the use of the Beck-Trefftz method in flow boiling in a minichannel

In this paper, the solution of the two-dimensional inverse heat transfer problem with the use of the Beck method coupled with the Trefftz method is proposed. This method was applied for solving an inverse heat conduction problem. The aim of the calculation was to determine the boiling heat transfer coefficient on the basis of temperature measurements taken by infrared thermography. The experimental data of flow boiling heat transfer in a single vertical minichannel of 1.7 mm depth, heated asymmetrically, were used in calculations. The heating element for two refrigerants (FC-72 and HFE-7100, 3M) flowing in the minichannel was the plate enhanced on the side contacting with the fluid. The analysis of the results was performed on the basis of experimental series obtained for the same heat flux and two different mass flow velocities. The results were presented as infrared thermographs, heated wall temperature and heat transfer coefficient as a function of the distance from the minichannel inlet. The results was discussed for the subcooled and saturated boiling regions separately.

Influence of a strong magnetic field on paramagnetic fluid's flow in cubical enclosure

The fluid behaviour in thermo-magnetic convection of paramagnetic fluid in a strong magnetic field was studied. The fluid was 50% volume aqueous solution of glycerol with an addition of gadolinium nitrate hexahydrate (Gd(NO3)3-6H2O). Experimental enclosure - a vessel with aspect ratio (AR=height/width) equal to 1.0 - was heated from the bottom, and cooled from the top. Temperature difference between top and bottom walls was kept constant at ΔT = 5 and 11 [°C]. The magnetic induction was increased stepwise from 1 to 10 [T] and thermocouples placed inside the enclosures measured temperature changes of the fluid. On the basis of temperature measurements, analysis of the fluid flow was performed.

Investigation of End-Milling Process Based on Monitoring Method with Wireless Telegraphic Multifunctional Tool Holder and Infrared Thermography

Infrared thermographic technology has attracted the attention of various industrial fields. We therefore focus on it as a novel tool temperature monitoring method to improve the end-milling conditions of difficult-to-cut materials. However, it is difficult to measure tool temperature under coolant conditions because coolant prevents the monitoring of end-mill tool surfaces. Thus, we developed a novel temperature monitoring method by applying a pore electric discharge machining process to place a thermocouple sensor in the end-mill tool and by using a wireless telegraphic multifunctional tool holder to directly measure the internal temperature of the end-mill tool under rotation. We evaluated internal temperature distribution under various end-milling conditions on the basis of multipoint simultaneous measurements and discussed the influence of forced convection heat transfer on the internal temperature of the tool under various rotating conditions. In addition, we used a finite element method to analyze unsteady heat conduction on the basis of temperature measurement by high-speed video infrared thermography and compared the results with those of the wireless telegraphic multifunctional tool holder to demonstrate its validity and usefulness.

Comparison of two methods for contactless surface temperature measurement

The aim of the paper is to determine the temperature filed of the heating surface on the basis of temperature measurements taken by liquid crystal thermography and infrared thermography applied in boiling heat transfer research during FC-72 flow in minichannels, and to compare them. The essential part of the experimental stand is the test section with two parallel rectangular minichannels, each 1.7 mm deep, 24 mm wide and 360 mm long. It is possible to observe the channel surfaces through panes: of the first minichannel allows observing foil temperature changes on the plain side due to liquid crystal thermography (LCT), which required treating the foil surface with thermochromic liquid crystals, of the other minichannel enables detecting outer glass or foil surface temperature changes due to infrared thermography (IRT). Comparison of the results of the measurements are presented in graphical form as thermographs and as heating surface temperature vs. minichannel length. The differences between two sets of measurement data concerning the temperature of the heating surface obtained with LCT and IRT, were analyzed using: Pearson linear correlation coefficient, determination coefficient, Experimental Method Error and Method Accuracy. The comparative data analysis shows that similar values and distributions of the surface temperature were obtained from both techniques.

Simultaneously estimation for surface heat fluxes of steel slab in a reheating furnace based on DMC predictive control

The predictive control theory is utilized for the research of a simultaneous estimation of heat fluxes through the upper, side and lower surface of a steel slab in a walking beam type rolling steel reheating furnace. An inverse algorithm based on dynamic matrix control (DMC) is established. That is, each surface heat flux of a slab is simultaneously estimated through rolling optimization on the basis of temperature measurements in selected points of its interior by utilizing step response function as predictive model of a slab's temperature. The reliability of the DMC results is enhanced without prior assuming specific functions of heat fluxes over a period of future time. The inverse algorithm proposed a respective regularization to effectively improve the stability of the estimated results by considering obvious strength differences between the upper as well as lower and side surface heat fluxes of the slab.

Experimental verification of approximate solution of the inverse Stefan problem obtained by applying the invasive weed optimization algorithm

The paper proposes a procedure for solving the inverse Stefan problem consisted in reconstruction of the function describing the heat transfer coefficient on the basis of temperature measurements. Elaborated method is based on two procedures: solution of the appropriate direct Stefan problem by using the finite difference method combined with the alternating phase truncation method and minimization of some functional with the aid of invasive weed optimization algorithm. For verifying the effectiveness of investigated algorithm the experimental data obtained in the solidification of aluminum are used.

Annular flow microreactor: An efficient tool for kinetic studies in gas phase at very short residence times

This study deals with the modelling of a tubular flow microreactor and an annular flow microreactor that are used for kinetic studies of thermal reactions (873–1273K) at very short residence times (10–100ms). The construction of a kinetic model on the basis of experimental reaction data requires the precise characterization of the thermal behaviour and the hydrodynamics of the reactor. In kinetic studies, the reactor is usually considered as an isothermal Plug Flow Reactor. In this paper, we demonstrate that an annular flow microreactor used at very short residence time not only leads to a temperature profile which is better controlled than in a tubular flow microreactor, but also to less axial dispersion for laminar flow. The comparison between both reactors is performed on the basis of temperature measurements, RTD measurements at room temperature, dimensionless numbers calculations and Computational Fluid Dynamics in typical reaction conditions.

Using Field Data to Evaluate Bottom Ash as Pavement Insulation Layer

A common problem in cold regions is the penetration of frost into susceptible subgrade soils. This study investigated the application of bottom ash in comparison with polystyrene boards as an insulation layer at a test road in Edmonton, Alberta, Canada. The adjacent normal section was used as the control section. All sections were instrumented at various depths to monitor temperature variation. On the basis of temperature measurements in the base and subgrade layers from October 2012 to June 2013, frost depth and freezing and thawing periods were analyzed for each section. R-values for thermal resistivity were calculated for each layer, considering its thickness and thermal properties, and were used for justifying and comparing the temperature trends. R-values were established at 1.4 and 16.7 m2 • °C/W for the bottom ash and polystyrene board, respectively. The base layer in the polystyrene section experienced higher temperatures in the summer and lower temperatures in the winter in relation to the bottom ash and control sections. On the basis of temperature measurements at depths of 1.61 to 3.27 m, the subgrade in the polystyrene section showed the lowest variation in temperature with respect to time and depth, followed by the bottom ash and then the control section. This behavior indicated that the insulation layers obstructed the heat transfer between the surface and the lower layers. The use of polystyrene boards and bottom ash as insulation materials decreased the frost depth by at least 40% and 28%, respectively, compared with the control section.

Experimental verification of immune recruitment mechanism and clonal selection algorithm applied for solving the inverse problems of pure metal solidification

In the paper an application of two immune algorithms — Immune Recruitment Mechanism and Clonal Selection Algorithm — in procedures for solving the inverse problems of pure metals solidification is presented. Discussed problems consist in reconstruction of boundary conditions (forms of the heat transfer coefficient and the heat flux) on the basis of temperature measurements. For verifying the effectiveness of investigated algorithms the experimental data obtained in the solidification of aluminum have been used. An example of applying considered procedures for determining the cooling conditions of the continuously cast ingot is also presented.

Measurement of heat flux density and heat transfer coefficient

Measurement of heat flux density and heat transfer coefficientThe paper presents the solution to a problem of determining the heat flux density and the heat transfer coefficient, on the basis of temperature measurement at three locations in the flat sensor, with the assumption that the heat conductivity of the sensor material is temperature dependent. Three different methods for determining the heat flux and heat transfer coefficient, with their practical applications, are presented. The uncertainties in the determined values are also estimated.

Temperature field of radioactive isotopes in a porous medium

The asymptotic method in zero and first approximations is used to find formulas for the calculation of temperature fields arising as a result of injection of fluid radioactive waste into porous deep-lying beds. A formula is derived for determining the critical value of Henry coefficient Kcr. It is demonstrated that, at K Kcr, it lags behind the latter. Because in actual cases K > Kcr is observed, it is possible to monitor the contamination zone on the basis of temperature measurements in monitor wells.

Estimation of the transient surface temperature and heat flux of a steel slab using an inverse method

In the steel industry it is of great importance to be able to control the surface temperature and heating- or cooling rates during heat treatment processes. An experiment was performed in which a steel slab was heated up to 1250 °C in a fuel fired test furnace. The transient surface temperature and heat flux of a steel slab is calculated using a model for inverse heat conduction. That is, the time dependent local surface temperature and heat flux of a slab is calculated on the basis of temperature measurements in selected points of its interior by using a model of inverse heat conduction. Time- and temperature histories were measured at three points inside a steel slab. Measured temperature histories at the two lower locations of the slab were used as input to calculate the temperature at the position of the third location. A comparison of the experimentally measured and the calculated temperature histories was made to verify the model. The results showed very good agreement and suggest that this model can be applied to similar applications in the Steel industry or in other areas where the target of investigation for some reason is inaccessible to direct measurements.

Comparison of Whole-Domain and Sequential Algorithms for Function Specification Method in the Inverse Heat Transfer Problem of Laminar Convective Pipe Flow

This article compares the application of the whole-domain function specification method (WDFSM) and the sequential function specification method (SFSM) to the inverse problem of transient conjugate heat transfer of laminar forced convection in a circular pipe. The two inverse methods are used to estimate the time-varying inlet temperature and the outer-wall heat flux simultaneously on the basis of temperature measurements taken at two different locations within the pipe flow. The numerical results reveal that the estimations obtained from the WDFSM method are marginally better than those obtained from the SFSM approach.