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Ulf Wickström - One of the best experts on this subject based on the ideXlab platform.

  • measuring incident heat flux and Adiabatic Surface temperature with plate thermometers in ambient and high temperatures
    Fire and Materials, 2019
    Co-Authors: Ulf Wickström, Johan Anderson, Johan Sjostrom
    Abstract:

    A new more insulated and faster responding plate thermometer (PT) is introduced, which has been developed for measurements particularly in air at ambient temperature. It is a cheaper and more pract ...

  • large scale test on a steel column exposed to localized fire
    Journal of Structural Fire Engineering, 2014
    Co-Authors: Alexandra Bystrom, Ulf Wickström, Johan Sjostrom, David Lange, Milan Veljkovic
    Abstract:

    A localized fire is a fire which in a compartment is unlikely to reach flash-over and uniform temperature distribution. Designing for localized fires is generally more difficult than for flash-over compartment fires because of the complexity of the problem. There is also a lack of experimental data. We report here on a full scale test series on a steel column exposed to localized fires. The setup is a 6 meters tall hollow circular column, ϕ = 200 mm with a steel thickness of 10 mm. The unloaded column was hanging centrally above different pool fires. Temperatures of gas and steel were measured by thermocouples, and Adiabatic Surface temperatures at the steel Surface were measured by plate thermometers of various designs. The results are compared with estimates based on Eurocode 1991-1-2 which in all cases studied overestimate the thermal impact for this setup. The input from plate thermometers was used to compute the steel temperatures using finite element methods. Excellent agreement was found if the radiation exchange within the column due to asymmetry of the exposure was taken into account.

  • using plate thermometer measurements to calculate incident heat radiation
    Journal of Fire Sciences, 2013
    Co-Authors: Andreas Haggkvist, Johan Sjostrom, Ulf Wickström
    Abstract:

    The plate thermometer is a device used mainly to measure temperatures in fire resistance tests according to ISO 834-1 and EN 1363-1 and to measure the so-called Adiabatic Surface temperature. Howev...

  • measurement and calculation of Adiabatic Surface temperature in a full scale compartment fire experiment
    Journal of Fire Sciences, 2013
    Co-Authors: Alexandra Bystrom, Ulf Wickström, Xudong Cheng, Milan Veljkovic
    Abstract:

    Adiabatic Surface temperature is an efficient way of expressing thermal exposure. It can be used for bridging the gap between fire models and temperature models, as well as between fire testing and temperature models. In this study, a full-scale compartment fire experiment with wood crib fuel was carried out in a concrete building. Temperatures were measured with plate thermometers and ordinary thermocouples. Five plate thermometers and five thermocouples with a diameter of 0.25 mm were installed at different positions. These two different temperature devices recorded different temperatures, especially near the floor Surface. The Adiabatic Surface temperature was derived by a heat balance analysis from the plate thermometer measurements. The thermal inertia of the plate thermometer was taken into account to correct the measured results. In addition, the fire experiment scenario was also simulated with fire dynamics simulator. The fire source was specified as a given heat release rate, which was calculated from the measured mass loss rate of the wood fuel. The Adiabatic Surface temperatures at these measuring positions were simulated by the fire dynamics simulator model and compared with the experimental Adiabatic Surface temperatures. The comparative results showed that fire dynamics simulator predicted the Adiabatic Surface temperature accurately during the steady-state period. Language: en

  • different types of plate thermometers for measuring incident radiant heat flux and Adiabatic Surface temperature
    Conference proceeding Interflam 2013#N#13th international Fire Science & Engingeering Conference 2013, 2013
    Co-Authors: Johan Sjostrom, Ulf Wickström
    Abstract:

    Different types of plate thermometers for measuring incident radiant heat flux and Adiabatic Surface temperature

Qingsheng Wang - One of the best experts on this subject based on the ideXlab platform.

  • a new method to calculate Adiabatic Surface temperature using plate thermometer in an ambient condition
    Applied Thermal Engineering, 2019
    Co-Authors: Ruiqing Shen, Haejun Park, Qingtong Liu, Qingsheng Wang
    Abstract:

    Abstract Adiabatic Surface temperature (AST) is a useful and convenient concept to characterize the thermal boundary condition that a solid Surface is exposed to. Plate thermometer (PT) is often used to calculate AST. However, in an ambient temperature condition, the calculated AST is known to be significantly lower than actual AST. Faced with this challenge, a new method to calculate AST using PT is proposed in the current study. A correlation to determine AST from measured PT temperature in steady state is first developed in a radiation-only environment. Based on this correlation, a correlation for AST is derived for a mixed radiation/convection environment, i.e., for any given convective heat transfer coefficient. AST calculated based on the proposed method is validated against two pool fires.

C Balaji - One of the best experts on this subject based on the ideXlab platform.

  • estimation of local heat transfer coefficient from natural convection experiments using liquid crystal thermography and bayesian method
    Experimental Thermal and Fluid Science, 2018
    Co-Authors: Pradeep S Jakkareddy, C Balaji
    Abstract:

    Abstract In this work, an inverse methodology is developed for estimating the local heat transfer coefficients on a vertical plate embedded with the three discrete heat sources, under steady state natural convection, with the temperatures measured at the Adiabatic Surface without disturbing the fluid flow, using simple conduction/surrogate model and Bayesian inference. Liquid crystal thermography (LCT), an optical measurement method based on the colour-temperature relationship of thermochromic liquid crystal sheet (TLC) is used to determine the temperature field of the Adiabatic Surface. Bayesian framework with Metropolis Hastings-Markov chain Monte Carlo (MH-MCMC) sampling method is considered for exploring the posterior distribution to estimate the parameters in terms of point estimates like mean, Maximum a posteriori (MAP) and standard deviation. A parity plot between simulated (using retrieved parameters) and measured TLC temperatures show good agreement.

Giuseppe Rotondo - One of the best experts on this subject based on the ideXlab platform.

  • influence of wall emissivity and convective heat transfer coefficient on the Adiabatic Surface temperature as thermal structural parameter in fire modeling
    Applied Thermal Engineering, 2013
    Co-Authors: Assunta Andreozzi, Nicola Bianco, Marilena Musto, Giuseppe Rotondo
    Abstract:

    Abstract In fire engineering analysis, one of the open problem is the transfer of thermal parameters obtained by fire CFD model to FEM models for structural analysis. In this study the new useful concept of “Adiabatic Surface Temperature” or more commonly known as AST, introduced by Wickstrom, is investigated. The Adiabatic Surface temperature offers the opportunity to transfer both thermal information of the gas and the net heat flux to the solid phase model, obtained by CFD analysis. In this study two CFD analyses are carried out in order to evaluate the effect of emissivity and of convective heat transfer coefficient to determine the AST. First one CFD analysis simulating a fire scenario, “conjugate heat transfer”, with a square steel beam exposed to hot Surface is carried out to calculate AST, heat convective coefficient and temperature field in the beam. Second one, a conductive analysis is carried out on “standalone beam” imposing a third type boundary condition on its boundaries assuming the AST, evaluated in the conjugate analysis, as external temperature. Different heat convective coefficients are imposed on the beam walls. The comparison between results obtained by means of the two proposed analyses shows the use of AST as transfer thermal parameter between CFD (Computational Fluid Dynamic) and FEM (Finite Element Method) models is appropriate when the convective heat transfer coefficient is properly evaluated.

Mohamed Ali - One of the best experts on this subject based on the ideXlab platform.

  • the effect of lateral mass flux on the natural convection boundary layers induced by a heated vertical plate embedded in a saturated porous medium with internal heat generation
    International Journal of Thermal Sciences, 2007
    Co-Authors: Mohamed Ali
    Abstract:

    Abstract The effect of suction or injection on the free convection boundary layers induced by a heated vertical plate embedded in a saturated porous medium with an exponential decaying heat generation is studied. Similarity solutions are obtained for the governing steady laminar boundary layer equations using Darcy and Boussinesq approximations. The plate is assumed to have a power law temperature distribution. Three distinct cases of uniform lateral mass flux, uniform Surface temperature, and uniform heat flux are studied. The effects of suction/injection parameter f w and temperature exponent λ on the flow of heat transfer are studied. Some exact analytical results are obtained for λ = 1 , − 1 / 3 . Critical values of the suction/injection parameter are obtained for Adiabatic Surface as a function of the temperature exponent parameter λ.