Constant effective thermal conductivity of intumescent coatings: Analysis of experimental results

2017 ◽  
Vol 35 (2) ◽  
pp. 132-155 ◽  
Author(s):  
GQ Li ◽  
Jun Han ◽  
Yong C Wang
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Fire Resistance ◽  
Coating Thickness ◽  
Fundamental Property ◽  
Simple Method ◽  
Intumescent Coating ◽  
Intumescent Coatings ◽  
Steel Section ◽  
Fire Conditions

This article presents the results of an investigation to obtain the constant effective thermal conductivities of intumescent coatings under the influence of different intumescent coating factors (type of intumescent coating, coating thickness, steel section factor, fire condition), based on the analysis of an extensive collection of fire test data. The constant effective thermal conductivity is not a fundamental property of the intumescent coating, but is a desired quantity for simplified practical fire resistance design. It is defined as the temperature-averaged value of the temperature-dependent effective thermal conductivity within the temperature range of interest for fire resistance design of steel structures. The results indicate that for each of the intumescent coating types examined, a consistent constant effective thermal conductivity exists. The constant effective thermal conductivity tends to increase with decreasing steel section factor and to decrease with increasing coating thickness. For intumescent coating–protected steel I-sections, incorporating the shadow effect gives more consistent values of constant thermal conductivity compared to those without accounting for the effect. The same constant effective thermal conductivity obtained from the ISO fire tests may be used for different fire conditions as long as the steel temperature is higher than 400 °C. The results of this research make it possible to develop a simple method to calculate temperatures of intumescent coating–protected steel sections under different fire conditions.

scholarly journals Estimation of Effective Thermal Conductivity of Two-Phase Material for Hollow Circular Model

2018 ◽  
Vol 172 ◽  
pp. 02004
Author(s):  
Prateek Kumar Sahu ◽  
Nisha Netam ◽  
Lal Chandra Shah
Keyword(s):  
Thermal Conductivity ◽  
Circular Cylinder ◽  
Effective Thermal Conductivity ◽  
Complex Structure ◽  
Fundamental Property ◽  
Percentage Error ◽  
Phase System ◽  
Two Phase ◽  
Hollow Circular Cylinder ◽  
Circular Model

Two-phase materials are commonly used in engineering application because of its various properties like strength, thermal conductivity, durability and toughness etc. Effective thermal conductivity (ETC) of two-phase material is the fundamental property to predict its thermal performance. Various geometry (spheres, cylinders, irregular particles) have been considered by researchers for calculating ETC of two-phase materials. Due to complex structure, hollow circular cylinder geometry is not reported yet. In this paper, two-dimensional periodic two-phase system, with hollow circular cylinder shape is considered for calculating ETC. In present work unit cell approach method is used to derive collocated parameters model for estimation of ETC. Hollow circular cylinder model with Ψ = 0.2 gives good result for estimating ETC with average percentage error of 6.46%.

scholarly journals Effective conductivity of isotropic composite with Kapitza thermal resistance

2018 ◽  
Author(s):  
Kien Trung Nguyen ◽  
Luat Van Nguyen ◽  
Chinh Duc Pham
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Effective Conductivity ◽  
Imperfect Interface ◽  
Simple Method ◽  
Isotropic Composite ◽  
Equivalent Inclusion

A simple method is introduced for computing the effective conductivity of isotropic composite with imperfect interface. Based on the doubly-coated circle assemblage model, one can determine the effective thermal conductivity of the composite. The application of this model to the composite with imperfect interface of the Kapitza's type is proposed. The results obtained were compared with the FFT simulation and the equivalent inclusion approximation in 2D show the effectiveness of the methods.

scholarly journals Feature of fire resistance calculation of steel structures with intumescent coating

2018 ◽  
Vol 230 ◽  
pp. 02036 ◽  
Author(s):  
Alexey Vasilchenko ◽  
Yuriy Otrosh ◽  
Nikolay Adamenko ◽  
Evgeny Doronin ◽  
Andrey Kovalov
Keyword(s):  
Fire Resistance ◽  
Steel Structure ◽  
Steel Structures ◽  
Metal Structure ◽  
Heating Time ◽  
Steel Frame ◽  
Frame Structures ◽  
Intumescent Coating ◽  
Intumescent Coatings ◽  
Steel Frame Structures

The problem of estimation of fire resistance of steel frame structures with intumescent coatings is considered. It implies that both physical properties of a covering (its thickness and structure) and mechanical properties of a metal structure change critically at heating. All above changes should be considered to maintain the standard values of fire resistance of a construction at calculation. Usually, known technical characteristics of fire resistance of intumescent coverings are used for estimation of fire resistance of steel structures with intumescent coverings. Importance of taking into account the influence of strength loss time at heating of a steel structure on calculation of fire resistance limit of system “intumescent fireproof coating steel structure” is shown in the article. On an example of calculation of heating time to the critical temperature of steel columns and beams protected by intumescent coating, it is shown that own heating time of steel structures before they lose strength makes 10 to 16 % from a settlement limit of fire resistance. This fact should be considered at the forecast of fire resistance of steel frame structures with intumescent coatings.

Measurement of the Thermal Contact Conductance and Thermal Conductivity of Anodized Aluminum Coatings

1990 ◽  
Vol 112 (3) ◽  
pp. 579-585 ◽  
Author(s):  
G. P. Peterson ◽  
L. S. Fletcher
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Coating Thickness ◽  
Thermal Contact ◽  
Thermal Contact Conductance ◽  
Aluminum Surface ◽  
Anodized Aluminum ◽  
Contact Conductance ◽  
Surface Measurements

An experimental investigation was conducted to determine the thermal contact conductance and effective thermal conductivity of anodized coatings. One chemically polished Aluminum 6061-T6 test specimen and seven specimens with anodized coatings varying in thickness from 60.9 μm to 163.8 μm were tested while in contact with a single unanodized aluminum surface. Measurements of the overall joint conductance, composed of the thermal contact conductance between the anodized coating and the bare aluminum surface and the bulk conductance of the coating material, indicated that the overall joint conductance decreased with increasing thickness of the anodized coating and increased with increasing interfacial load. Using the experimental data, a dimensionless expression was developed that related the overall joint conductance to the coating thickness, the surface roughness, the interfacial pressure, and the properties of the aluminum substrate. By subtracting the thermal contact conductance from the measured overall joint conductance, estimations of the effective thermal conductivity of the anodized coating as a function of pressure were obtained for each of the seven anodized specimens. At an extrapolated pressure of zero, the effective thermal conductivity was found to be approximately 0.02 W/m-K. In addition to this extrapolated value, a single expression for predicting the effective thermal conductivity as a function of both the interface pressure and the anodized coating thickness was developed and shown to be within ±5 percent of the experimental data over a pressure range of 0 to 14 MPa.

scholarly journals Fire Performance of Intumescent Waterborne Coatings with Encapsulated APP for Wood Constructions

Coatings ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1272
Author(s):  
Atif Hussain ◽  
Véronic Landry ◽  
Pierre Blanchet ◽  
Doan-Trang Hoang ◽  
Christian Dagenais
Keyword(s):  
Heat Release ◽  
Water Absorption ◽  
Fire Resistance ◽  
Ammonium Polyphosphate ◽  
Vapor Sorption ◽  
Fire Performance ◽  
Dynamic Vapor Sorption ◽  
Intumescent Coating ◽  
Intumescent Coatings ◽  
Cone Calorimeter Test

In this work, intumescent coatings were prepared for protection of wood from fire. The fire-retardant chemical ammonium polyphosphate (APP) is known to have poor resistance to water and high humidity as it is hygroscopic in nature. To improve the water resistance, durability and fire resistance of the intumescent coating, APP was modified using a hybrid organic-inorganic polysiloxane encapsulation shell prepared by the sol–gel method. The physical and chemical properties of the intumescent mix containing microencapsulated ammonium polyphosphate (EAPP) particles were characterized by X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), water absorption, dynamic vapor sorption (DVS) and thermogravimetric analysis (TGA). The EAPP mix showed 50% reduction in water absorption, 75% reduction in water vapor sorption and increased thermal stability when compared to the APP mix. The intumescent coatings were applied on wood samples, and their fire performance was evaluated using a cone calorimeter test. The intumescent coatings containing EAPP mix showed better fire retarding properties with longer time to ignition, lower heat release rate and shorter heat release peak when compared to the coating without EAPP mix. The prepared intumescent coating shows higher resistance to water and moisture, and it has great potential to be used in bio-based construction industry for enhancing the fire resistance of wood.

Numerical modelling of heat transfer through protected composite structural members

2019 ◽  
Vol 5 (3) ◽  
pp. 96
Author(s):  
Burak Kaan Çırpıcı ◽  
Süleyman Nazif Orhan ◽  
Türkay Kotan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Numerical Model ◽  
Numerical Models ◽  
High Energy ◽  
Intumescent Coating ◽  
Steel Temperature ◽  
Intumescent Coatings ◽  
Number Of Layers ◽  
Dry Film Thickness

Among many various types of passive fire protection materials (i.e. plaster boards, sprayed materials and intumescent coatings) thin film intumescent coatings have become the preferable option owing to their good advantages such as flexibility, good appearance (aesthetics), light weight to the structure and fast application. Despite their popularity, there is also a lack of good understanding of fire behaviour. In general, experimental methods are used to push this knowledge with labour and high-energy consumption and extremely expensive processes. With the development of computer technology, numerical models to predict the heat transfer phenomena of intumescent coatings have been developed with time. In this work, the numerical model has been established to predict the heat transfer performance including material properties such as thermal conductivity and dry film thickness of intumescent coating. The developed numerical model has been divided into different layers to understand the sensitivity of steel temperature to the number of layers of intumescent coating and mesh sizes. The temperature-dependent thermal conductivity of intumescent coatings can be calculated based on inverse solution of the equation for calculating temperatures in protected steel according to the Eurocodes (EN 1993-1-2 and EN 1994-1-2). However, as the temperature distribution in the intumescent coatings is highly non-uniform, that Eurocode equation does not give accurate coating thermal conductivity-temperature relationship for use in numerical heat transfer modelling when the coating is divided into a number of layers, each having its characteristic thermal conductivity values. The comparison study of steel temperature under Standard (ISO 834) and Fast fire conditions against Eurocode analytical solution has also been made by assuming both constant thermal conductivity and variable thermal conductivity. The obtained results show close agreement with the Eurocode solution choosing a minimum certain mesh, number of layer and best-fitted thermal conductivity of the intumescent coating.

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